dyld-733.6.tar.gz

[apple/dyld.git] / src / dyld2.cpp

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2004-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <dirent.h>
#include <pthread.h>
#include <libproc.h>
#include <sys/param.h>
#include <mach/mach_time.h> // mach_absolute_time()
#include <mach/mach_init.h> 
#include <sys/types.h>
#include <sys/stat.h> 
#include <sys/syscall.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/syslog.h>
#include <sys/uio.h>
#include <mach/mach.h>
#include <mach-o/fat.h>
#include <mach-o/loader.h> 
#include <mach-o/ldsyms.h> 
#include <libkern/OSByteOrder.h> 
#include <libkern/OSAtomic.h>
#include <mach/mach.h>
#include <sys/sysctl.h>
#include <sys/mman.h>
#include <sys/dtrace.h>
#include <libkern/OSAtomic.h>
#include <Availability.h>
#include <System/sys/codesign.h>
#include <System/sys/csr.h>
#include <_simple.h>
#include <os/lock_private.h>
#include <System/machine/cpu_capabilities.h>
#include <System/sys/reason.h>
#include <kern/kcdata.h>
#include <sys/attr.h>
#include <sys/fsgetpath.h>

#if TARGET_OS_SIMULATOR
        enum {
                AMFI_DYLD_INPUT_PROC_IN_SIMULATOR = (1 << 0),
        };
        enum amfi_dyld_policy_output_flag_set {
                AMFI_DYLD_OUTPUT_ALLOW_AT_PATH = (1 << 0),
                AMFI_DYLD_OUTPUT_ALLOW_PATH_VARS = (1 << 1),
                AMFI_DYLD_OUTPUT_ALLOW_CUSTOM_SHARED_CACHE = (1 << 2),
                AMFI_DYLD_OUTPUT_ALLOW_FALLBACK_PATHS = (1 << 3),
                AMFI_DYLD_OUTPUT_ALLOW_PRINT_VARS = (1 << 4),
                AMFI_DYLD_OUTPUT_ALLOW_FAILED_LIBRARY_INSERTION = (1 << 5),
        };
        extern "C" int amfi_check_dyld_policy_self(uint64_t input_flags, uint64_t* output_flags);
#else
        #include <libamfi.h>
#endif
#include <sandbox.h>
#include <sandbox/private.h>
#if __has_feature(ptrauth_calls)
        #include <ptrauth.h>
#endif

extern "C" int __fork();

#include <array>
#include <algorithm>
#include <vector>


#include "dyld2.h"
#include "ImageLoader.h"
#include "ImageLoaderMachO.h"
#include "dyldLibSystemInterface.h"
#include "dyld_cache_format.h"
#include "dyld_process_info_internal.h"

#if SUPPORT_ACCELERATE_TABLES
        #include "ImageLoaderMegaDylib.h"
#endif

#if TARGET_OS_SIMULATOR
        extern "C" void* gSyscallHelpers;
#else
        #include "dyldSyscallInterface.h"
#endif

#include "Closure.h"
#include "libdyldEntryVector.h"
#include "MachOLoaded.h"
#include "Loading.h"
#include "DyldSharedCache.h"
#include "SharedCacheRuntime.h"
#include "StringUtils.h"
#include "Tracing.h"
#include "ClosureBuilder.h"
#include "ClosureFileSystemPhysical.h"
#include "FileUtils.h"
#include "BootArgs.h"

#ifndef MH_HAS_OBJC
  #define MH_HAS_OBJC                   0x40000000
#endif

// not libc header for send() syscall interface
extern "C" ssize_t __sendto(int, const void *, size_t, int, const struct sockaddr *, socklen_t);


// ARM and x86_64 are the only architecture that use cpu-sub-types
#define CPU_SUBTYPES_SUPPORTED  ((__arm__ || __arm64__ || __x86_64__) && !TARGET_OS_SIMULATOR)

#if __LP64__
        #define LC_SEGMENT_COMMAND              LC_SEGMENT_64
        #define LC_SEGMENT_COMMAND_WRONG LC_SEGMENT
        #define LC_ENCRYPT_COMMAND              LC_ENCRYPTION_INFO
        #define macho_segment_command   segment_command_64
        #define macho_section                   section_64
#else
        #define LC_SEGMENT_COMMAND              LC_SEGMENT
        #define LC_SEGMENT_COMMAND_WRONG LC_SEGMENT_64
        #define LC_ENCRYPT_COMMAND              LC_ENCRYPTION_INFO_64
        #define macho_segment_command   segment_command
        #define macho_section                   section
#endif



#define CPU_TYPE_MASK 0x00FFFFFF        /* complement of CPU_ARCH_MASK */


/* implemented in dyld_gdb.cpp */
extern void resetAllImages();
extern void addImagesToAllImages(uint32_t infoCount, const dyld_image_info info[]);
extern void removeImageFromAllImages(const mach_header* mh);
extern void addNonSharedCacheImageUUID(const dyld_uuid_info& info);
extern const char* notifyGDB(enum dyld_image_states state, uint32_t infoCount, const dyld_image_info info[]);
extern size_t allImagesCount();

// magic so CrashReporter logs message
extern "C" {
        char error_string[1024];
}

// magic linker symbol for start of dyld binary
extern "C" const macho_header __dso_handle;


//
// The file contains the core of dyld used to get a process to main().  
// The API's that dyld supports are implemented in dyldAPIs.cpp.
//
//
//
//
//
namespace dyld {
        struct RegisteredDOF { const mach_header* mh; int registrationID; };
        struct DylibOverride { const char* installName; const char* override; };
}


VECTOR_NEVER_DESTRUCTED(ImageLoader*);
VECTOR_NEVER_DESTRUCTED(dyld::RegisteredDOF);
VECTOR_NEVER_DESTRUCTED(dyld::ImageCallback);
VECTOR_NEVER_DESTRUCTED(dyld::DylibOverride);
VECTOR_NEVER_DESTRUCTED(ImageLoader::DynamicReference);

VECTOR_NEVER_DESTRUCTED(dyld_image_state_change_handler);

namespace dyld {


// 
// state of all environment variables dyld uses
//
struct EnvironmentVariables {
        const char* const *                     DYLD_FRAMEWORK_PATH;
        const char* const *                     DYLD_FALLBACK_FRAMEWORK_PATH;
        const char* const *                     DYLD_LIBRARY_PATH;
        const char* const *                     DYLD_FALLBACK_LIBRARY_PATH;
        const char* const *                     DYLD_INSERT_LIBRARIES;
        const char* const *                     LD_LIBRARY_PATH;                        // for unix conformance
        const char* const *                     DYLD_VERSIONED_LIBRARY_PATH;
        const char* const *                     DYLD_VERSIONED_FRAMEWORK_PATH;
        bool                                            DYLD_PRINT_LIBRARIES_POST_LAUNCH;
        bool                                            DYLD_BIND_AT_LAUNCH;
        bool                                            DYLD_PRINT_STATISTICS;
        bool                                            DYLD_PRINT_STATISTICS_DETAILS;
        bool                                            DYLD_PRINT_OPTS;
        bool                                            DYLD_PRINT_ENV;
        bool                                            DYLD_DISABLE_DOFS;
        bool                                            hasOverride;
                            //  DYLD_SHARED_CACHE_DIR           ==> sSharedCacheOverrideDir
                                                        //      DYLD_ROOT_PATH                                  ==> gLinkContext.rootPaths
                                                        //      DYLD_IMAGE_SUFFIX                               ==> gLinkContext.imageSuffix
                                                        //      DYLD_PRINT_OPTS                                 ==> gLinkContext.verboseOpts
                                                        //      DYLD_PRINT_ENV                                  ==> gLinkContext.verboseEnv
                                                        //      DYLD_FORCE_FLAT_NAMESPACE               ==> gLinkContext.bindFlat
                                                        //      DYLD_PRINT_INITIALIZERS                 ==> gLinkContext.verboseInit
                                                        //      DYLD_PRINT_SEGMENTS                             ==> gLinkContext.verboseMapping
                                                        //      DYLD_PRINT_BINDINGS                             ==> gLinkContext.verboseBind
                                                        //  DYLD_PRINT_WEAK_BINDINGS            ==> gLinkContext.verboseWeakBind
                                                        //      DYLD_PRINT_REBASINGS                    ==> gLinkContext.verboseRebase
                                                        //      DYLD_PRINT_DOFS                                 ==> gLinkContext.verboseDOF
                                                        //      DYLD_PRINT_APIS                                 ==> gLogAPIs
                                                        //      DYLD_IGNORE_PREBINDING                  ==> gLinkContext.prebindUsage
                                                        //      DYLD_PREBIND_DEBUG                              ==> gLinkContext.verbosePrebinding
                                                        //      DYLD_NEW_LOCAL_SHARED_REGIONS   ==> gLinkContext.sharedRegionMode
                                                        //      DYLD_SHARED_REGION                              ==> gLinkContext.sharedRegionMode
                                                        //      DYLD_PRINT_WARNINGS                             ==> gLinkContext.verboseWarnings
                                                        //      DYLD_PRINT_RPATHS                               ==> gLinkContext.verboseRPaths
                                                        //      DYLD_PRINT_INTERPOSING                  ==> gLinkContext.verboseInterposing
                                                        //  DYLD_PRINT_LIBRARIES                        ==> gLinkContext.verboseLoading
};



typedef std::vector<dyld_image_state_change_handler> StateHandlers;


enum EnvVarMode { envNone, envPrintOnly, envAll };
        
// all global state
static const char*                                      sExecPath = NULL;
static const char*                                      sExecShortName = NULL;
static const macho_header*                      sMainExecutableMachHeader = NULL;
static uintptr_t                                        sMainExecutableSlide = 0;
#if CPU_SUBTYPES_SUPPORTED
static cpu_type_t                                       sHostCPU;
static cpu_subtype_t                            sHostCPUsubtype;
#endif
static ImageLoaderMachO*                        sMainExecutable = NULL;
static size_t                                           sInsertedDylibCount = 0;
static std::vector<ImageLoader*>        sAllImages;
static std::vector<ImageLoader*>        sImageRoots;
static std::vector<ImageLoader*>        sImageFilesNeedingTermination;
static std::vector<RegisteredDOF>       sImageFilesNeedingDOFUnregistration;
static std::vector<ImageCallback>   sAddImageCallbacks;
static std::vector<ImageCallback>   sRemoveImageCallbacks;
static std::vector<LoadImageCallback> sAddLoadImageCallbacks;
static std::vector<LoadImageBulkCallback> sAddBulkLoadImageCallbacks;
static bool                                                     sRemoveImageCallbacksInUse = false;
static void*                                            sSingleHandlers[7][3];
static void*                                            sBatchHandlers[7][3];
static ImageLoader*                                     sLastImageByAddressCache;
static EnvironmentVariables                     sEnv;
#if __MAC_OS_X_VERSION_MIN_REQUIRED
static const char*                                      sFrameworkFallbackPaths[] = { "$HOME/Library/Frameworks", "/Library/Frameworks", "/Network/Library/Frameworks", "/System/Library/Frameworks", NULL };
static const char*                                      sLibraryFallbackPaths[] = { "$HOME/lib", "/usr/local/lib", "/usr/lib", NULL };
static const char*                                      sRestrictedFrameworkFallbackPaths[] = { "/System/Library/Frameworks", NULL };
static const char*                                      sRestrictedLibraryFallbackPaths[] = { "/usr/lib", NULL };
#else
static const char*                                      sFrameworkFallbackPaths[] = { "/System/Library/Frameworks", NULL };
static const char*                                      sLibraryFallbackPaths[] = { "/usr/local/lib", "/usr/lib", NULL };
#endif
static UndefinedHandler                         sUndefinedHandler = NULL;
static ImageLoader*                                     sBundleBeingLoaded = NULL;      // hack until OFI is reworked
static dyld3::SharedCacheLoadInfo       sSharedCacheLoadInfo;
static const char*                                      sSharedCacheOverrideDir;
       bool                                                     gSharedCacheOverridden = false;
ImageLoader::LinkContext                        gLinkContext;
bool                                                            gLogAPIs = false;
#if SUPPORT_ACCELERATE_TABLES
bool                                                            gLogAppAPIs = false;
#endif
const struct LibSystemHelpers*          gLibSystemHelpers = NULL;
#if SUPPORT_OLD_CRT_INITIALIZATION
bool                                                            gRunInitializersOldWay = false;
#endif
static std::vector<DylibOverride>       sDylibOverrides;
#if !TARGET_OS_SIMULATOR        
static int                                                      sLogSocket = -1;
#endif
static bool                                                     sFrameworksFoundAsDylibs = false;
#if __x86_64__ && !TARGET_OS_SIMULATOR
static bool                                                     sHaswell = false;
#endif
static std::vector<ImageLoader::DynamicReference> sDynamicReferences;
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
static OSSpinLock                                       sDynamicReferencesLock = 0;
#pragma clang diagnostic pop
#if !TARGET_OS_SIMULATOR
static bool                                                     sLogToFile = false;
#endif
static char                                                     sLoadingCrashMessage[1024] = "dyld: launch, loading dependent libraries";
static _dyld_objc_notify_mapped         sNotifyObjCMapped;
static _dyld_objc_notify_init           sNotifyObjCInit;
static _dyld_objc_notify_unmapped       sNotifyObjCUnmapped;

#if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
static bool                                                     sForceStderr = false;
#endif


#if SUPPORT_ACCELERATE_TABLES
static ImageLoaderMegaDylib*            sAllCacheImagesProxy = NULL;
// Note these are now off by default as everything should use dyld3.
static bool                                                     sDisableAcceleratorTables = true;
#endif

bool                                                            gUseDyld3 = false;
static bool                                                     sSkipMain = false;
static void                       (*sEntryOveride)() = nullptr;
static bool                                                     sJustBuildClosure = false;
static bool                                                     sLogClosureFailure = false;

enum class ClosureMode {
        // Unset means we haven't provided an env variable or boot-arg to explicitly choose a mode
        Unset,
        // On means we set DYLD_USE_CLOSURES=1, or we didn't have DYLD_USE_CLOSURES=0 but did have
        // -force_dyld3=1 env variable or a customer cache on iOS
        On,
        // Off means we set DYLD_USE_CLOSURES=0, or we didn't have DYLD_USE_CLOSURES=1 but did have
        // -force_dyld2=1 env variable or an internal cache on iOS
        Off,
        // PreBuiltOnly means only use a shared cache closure and don't try build a new one
        PreBuiltOnly
};

static ClosureMode                                      sClosureMode = ClosureMode::Unset;
static bool                                                     sForceInvalidSharedCacheClosureFormat = false;
static uint64_t                                         launchTraceID = 0;

//
// The MappedRanges structure is used for fast address->image lookups.
// The table is only updated when the dyld lock is held, so we don't
// need to worry about multiple writers.  But readers may look at this
// data without holding the lock. Therefore, all updates must be done
// in an order that will never cause readers to see inconsistent data.
// The general rule is that if the image field is non-NULL then
// the other fields are valid.
//
struct MappedRanges
{
        MappedRanges*           next;
        unsigned long           count;
        struct {
                ImageLoader*    image;
                uintptr_t               start;
                uintptr_t               end;
        } array[1];
};

static MappedRanges*    sMappedRangesStart;

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
void addMappedRange(ImageLoader* image, uintptr_t start, uintptr_t end)
{
        //dyld::log("addMappedRange(0x%lX->0x%lX) for %s\n", start, end, image->getShortName());
        for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
                for (unsigned long i=0; i < p->count; ++i) {
                        if ( p->array[i].image == NULL ) {
                                p->array[i].start = start;
                                p->array[i].end = end;
                                // add image field last with a barrier so that any reader will see consistent records
                                OSMemoryBarrier();
                                p->array[i].image = image;
                                return;
                        }
                }
        }
        // table must be full, chain another
#if SUPPORT_ACCELERATE_TABLES
        unsigned count = (sAllCacheImagesProxy != NULL) ? 16 : 400;
#else
        unsigned count = 400;
#endif
        size_t allocationSize = sizeof(MappedRanges) + (count-1)*3*sizeof(void*);
        MappedRanges* newRanges = (MappedRanges*)malloc(allocationSize);
        bzero(newRanges, allocationSize);
        newRanges->count = count;
        newRanges->array[0].start = start;
        newRanges->array[0].end = end;
        newRanges->array[0].image = image;
        OSMemoryBarrier();
        if ( sMappedRangesStart == NULL ) {
                sMappedRangesStart = newRanges;
        }
        else {
                for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
                        if ( p->next == NULL ) {
                                OSMemoryBarrier();
                                p->next = newRanges;
                                break;
                        }
                }
        }
}

void removedMappedRanges(ImageLoader* image)
{
        for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
                for (unsigned long i=0; i < p->count; ++i) {
                        if ( p->array[i].image == image ) {
                                // clear with a barrier so that any reader will see consistent records
                                OSMemoryBarrier();
                                p->array[i].image = NULL;
                        }
                }
        }
}
#pragma clang diagnostic pop

ImageLoader* findMappedRange(uintptr_t target)
{
        for (MappedRanges* p = sMappedRangesStart; p != NULL; p = p->next) {
                for (unsigned long i=0; i < p->count; ++i) {
                        if ( p->array[i].image != NULL ) {
                                if ( (p->array[i].start <= target) && (target < p->array[i].end) )
                                        return p->array[i].image;
                        }
                }
        }
        return NULL;
}



const char* mkstringf(const char* format, ...)
{
        _SIMPLE_STRING buf = _simple_salloc();
        if ( buf != NULL ) {
                va_list list;
                va_start(list, format);
                _simple_vsprintf(buf, format, list);
                va_end(list);
                const char*     t = strdup(_simple_string(buf));
                _simple_sfree(buf);
                if ( t != NULL )
                        return t;
        }
        return "mkstringf, out of memory error";
}


void throwf(const char* format, ...) 
{
        _SIMPLE_STRING buf = _simple_salloc();
        if ( buf != NULL ) {
                va_list list;
                va_start(list, format);
                _simple_vsprintf(buf, format, list);
                va_end(list);
                const char*     t = strdup(_simple_string(buf));
                _simple_sfree(buf);
                if ( t != NULL )
                        throw t;
        }
        throw "throwf, out of memory error";
}


#if !TARGET_OS_SIMULATOR
static int sLogfile = STDERR_FILENO;
#endif

#if !TARGET_OS_SIMULATOR        
// based on CFUtilities.c: also_do_stderr()
static bool useSyslog()
{
        // Use syslog() for processes managed by launchd
        static bool launchdChecked = false;
        static bool launchdOwned = false;
        if ( !launchdChecked && gProcessInfo->libSystemInitialized ) {
                if ( (gLibSystemHelpers != NULL) && (gLibSystemHelpers->version >= 11) ) {
                        // <rdar://problem/23520449> only call isLaunchdOwned() after libSystem is initialized
                        launchdOwned = (*gLibSystemHelpers->isLaunchdOwned)();
                        launchdChecked = true;
                }
        }
        if ( launchdChecked && launchdOwned )
                return true;

        // If stderr is not available, use syslog()
        struct stat sb;
        int result = fstat(STDERR_FILENO, &sb);
        if ( result < 0 )
                return true; // file descriptor 2 is closed

        return false;
}

        
static void socket_syslogv(int priority, const char* format, va_list list)
{
        // lazily create socket and connection to syslogd
        if ( sLogSocket == -1 ) {
                sLogSocket = ::socket(AF_UNIX, SOCK_DGRAM, 0);
                if (sLogSocket == -1)
                        return;  // cannot log
                ::fcntl(sLogSocket, F_SETFD, 1);
        
                struct sockaddr_un addr;
                addr.sun_family = AF_UNIX;
                strncpy(addr.sun_path, _PATH_LOG, sizeof(addr.sun_path));
                if ( ::connect(sLogSocket, (struct sockaddr *)&addr, sizeof(addr)) == -1 ) {
                        ::close(sLogSocket);
                        sLogSocket = -1;
                        return;
                }
        }
        
        // format message to syslogd like: "<priority>Process[pid]: message"
        _SIMPLE_STRING buf = _simple_salloc();
        if ( buf == NULL )
                return;
        if ( _simple_sprintf(buf, "<%d>%s[%d]: ", LOG_USER|LOG_NOTICE, sExecShortName, getpid()) == 0 ) {
                if ( _simple_vsprintf(buf, format, list) == 0 ) {
                        const char* p = _simple_string(buf);
                        ::__sendto(sLogSocket, p, strlen(p), 0, NULL, 0);
                }
        }
        _simple_sfree(buf);
}



void vlog(const char* format, va_list list)
{
#if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
        // <rdar://problem/25965832> log to console when running iOS app from Xcode
        if ( !sLogToFile && !sForceStderr && useSyslog() )
#else
        if ( !sLogToFile && useSyslog() )
#endif
                socket_syslogv(LOG_ERR, format, list);
        else {
                _simple_vdprintf(sLogfile, format, list);
        }
}

void log(const char* format, ...)
{
        va_list list;
        va_start(list, format);
        vlog(format, list);
        va_end(list);
}


void vwarn(const char* format, va_list list) 
{
        _simple_dprintf(sLogfile, "dyld: warning, ");
        _simple_vdprintf(sLogfile, format, list);
}

void warn(const char* format, ...) 
{
        va_list list;
        va_start(list, format);
        vwarn(format, list);
        va_end(list);
}

#else
        extern void vlog(const char* format, va_list list);
#endif // !TARGET_OS_SIMULATOR  


#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
// <rdar://problem/8867781> control access to sAllImages through a lock
// because global dyld lock is not held during initialization phase of dlopen()
// <rdar://problem/16145518> Use OSSpinLockLock to allow yielding
static OSSpinLock sAllImagesLock = 0;

static void allImagesLock()
{
        OSSpinLockLock(&sAllImagesLock);
}

static void allImagesUnlock()
{
        OSSpinLockUnlock(&sAllImagesLock);
}
#pragma clang diagnostic pop


// utility class to assure files are closed when an exception is thrown
class FileOpener {
public:
        FileOpener(const char* path);
        ~FileOpener();
        int getFileDescriptor() { return fd; }
private:
        int fd;
};

FileOpener::FileOpener(const char* path)
 : fd(-1)
{
        fd = my_open(path, O_RDONLY, 0);
}

FileOpener::~FileOpener()
{
        if ( fd != -1 )
                close(fd);
}


static void     registerDOFs(const std::vector<ImageLoader::DOFInfo>& dofs)
{
        const size_t dofSectionCount = dofs.size();
        if ( !sEnv.DYLD_DISABLE_DOFS && (dofSectionCount != 0) ) {
                int fd = open("/dev/" DTRACEMNR_HELPER, O_RDWR);
                if ( fd < 0 ) {
                        //dyld::warn("can't open /dev/" DTRACEMNR_HELPER " to register dtrace DOF sections\n");
                }
                else {
                        // allocate a buffer on the stack for the variable length dof_ioctl_data_t type
                        uint8_t buffer[sizeof(dof_ioctl_data_t) + dofSectionCount*sizeof(dof_helper_t)];
                        dof_ioctl_data_t* ioctlData = (dof_ioctl_data_t*)buffer;
                        
                        // fill in buffer with one dof_helper_t per DOF section
                        ioctlData->dofiod_count = dofSectionCount;
                        for (unsigned int i=0; i < dofSectionCount; ++i) {
                                strlcpy(ioctlData->dofiod_helpers[i].dofhp_mod, dofs[i].imageShortName, DTRACE_MODNAMELEN);
                                ioctlData->dofiod_helpers[i].dofhp_dof = (uintptr_t)(dofs[i].dof);
                                ioctlData->dofiod_helpers[i].dofhp_addr = (uintptr_t)(dofs[i].dof);
                        }
                        
                        // tell kernel about all DOF sections en mas
                        // pass pointer to ioctlData because ioctl() only copies a fixed size amount of data into kernel
                        user_addr_t val = (user_addr_t)(unsigned long)ioctlData;
                        if ( ioctl(fd, DTRACEHIOC_ADDDOF, &val) != -1 ) {
                                // kernel returns a unique identifier for each section in the dofiod_helpers[].dofhp_dof field.
                                for (unsigned int i=0; i < dofSectionCount; ++i) {
                                        RegisteredDOF info;
                                        info.mh = dofs[i].imageHeader;
                                        info.registrationID = (int)(ioctlData->dofiod_helpers[i].dofhp_dof);
                                        sImageFilesNeedingDOFUnregistration.push_back(info);
                                        if ( gLinkContext.verboseDOF ) {
                                                dyld::log("dyld: registering DOF section %p in %s with dtrace, ID=0x%08X\n", 
                                                        dofs[i].dof, dofs[i].imageShortName, info.registrationID);
                                        }
                                }
                        }
                        else {
                                //dyld::log( "dyld: ioctl to register dtrace DOF section failed\n");
                        }
                        close(fd);
                }
        }
}

static void     unregisterDOF(int registrationID)
{
        int fd = open("/dev/" DTRACEMNR_HELPER, O_RDWR);
        if ( fd < 0 ) {
                dyld::warn("can't open /dev/" DTRACEMNR_HELPER " to unregister dtrace DOF section\n");
        }
        else {
                ioctl(fd, DTRACEHIOC_REMOVE, registrationID);
                close(fd);
                if ( gLinkContext.verboseInit )
                        dyld::warn("unregistering DOF section ID=0x%08X with dtrace\n", registrationID);
        }
}


//
// _dyld_register_func_for_add_image() is implemented as part of the general image state change notification
// Returns true if we did call add image callbacks on this image
//
static bool notifyAddImageCallbacks(ImageLoader* image)
{
        // use guard so that we cannot notify about the same image twice
        if ( ! image->addFuncNotified() ) {
                for (std::vector<ImageCallback>::iterator it=sAddImageCallbacks.begin(); it != sAddImageCallbacks.end(); it++) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*it), 0);
                        (*it)(image->machHeader(), image->getSlide());
                }
                for (LoadImageCallback func : sAddLoadImageCallbacks) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*func), 0);
                        (*func)(image->machHeader(), image->getPath(), !image->neverUnload());
                }
                image->setAddFuncNotified();
                return true;
        }
        return false;
}



// notify gdb about these new images
static const char* updateAllImages(enum dyld_image_states state, uint32_t infoCount, const struct dyld_image_info info[])
{
        // <rdar://problem/8812589> don't add images without paths to all-image-info-list
        if ( info[0].imageFilePath != NULL )
                addImagesToAllImages(infoCount, info);
        return NULL;
}


static StateHandlers* stateToHandlers(dyld_image_states state, void* handlersArray[7][3])
{
        switch ( state ) {
                case dyld_image_state_mapped:
                        return reinterpret_cast<StateHandlers*>(&handlersArray[0]);
                        
                case dyld_image_state_dependents_mapped:
                        return reinterpret_cast<StateHandlers*>(&handlersArray[1]);
                        
                case dyld_image_state_rebased:
                        return reinterpret_cast<StateHandlers*>(&handlersArray[2]);
                        
                case dyld_image_state_bound:
                        return reinterpret_cast<StateHandlers*>(&handlersArray[3]);
                        
                case dyld_image_state_dependents_initialized:
                        return reinterpret_cast<StateHandlers*>(&handlersArray[4]);

                case dyld_image_state_initialized:
                        return reinterpret_cast<StateHandlers*>(&handlersArray[5]);
                        
                case dyld_image_state_terminated:
                        return reinterpret_cast<StateHandlers*>(&handlersArray[6]);
        }
        return NULL;
}

#if SUPPORT_ACCELERATE_TABLES
static dyld_image_state_change_handler getPreInitNotifyHandler(unsigned index)
{
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(dyld_image_state_dependents_initialized, sSingleHandlers);
        if ( index >= handlers->size() )
                return NULL;
        return (*handlers)[index];
}

static dyld_image_state_change_handler getBoundBatchHandler(unsigned index)
{
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(dyld_image_state_bound, sBatchHandlers);
        if ( index >= handlers->size() )
                return NULL;
        return (*handlers)[index];
}

static void notifySingleFromCache(dyld_image_states state, const mach_header* mh, const char* path)
{
        //dyld::log("notifySingle(state=%d, image=%s)\n", state, image->getPath());
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sSingleHandlers);
        if ( handlers != NULL ) {
                dyld_image_info info;
                info.imageLoadAddress   = mh;
                info.imageFilePath              = path;
                info.imageFileModDate   = 0;
                for (dyld_image_state_change_handler handler : *handlers) {
                        const char* result = (*handler)(state, 1, &info);
                        if ( (result != NULL) && (state == dyld_image_state_mapped) ) {
                                //fprintf(stderr, "  image rejected by handler=%p\n", *it);
                                // make copy of thrown string so that later catch clauses can free it
                                const char* str = strdup(result);
                                throw str;
                        }
                }
        }
        if ( (state == dyld_image_state_dependents_initialized) && (sNotifyObjCInit != NULL) && (mh->flags & MH_HAS_OBJC) ) {
                dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_INIT, (uint64_t)mh, 0, 0);
                (*sNotifyObjCInit)(path, mh);
        }
}
#endif

#if !TARGET_OS_SIMULATOR
static void sendMessage(unsigned portSlot, mach_msg_id_t msgId, mach_msg_size_t sendSize, mach_msg_header_t* buffer, mach_msg_size_t bufferSize) {
        // Allocate a port to listen on in this monitoring task
        mach_port_t sendPort = dyld::gProcessInfo->notifyPorts[portSlot];
        if (sendPort == MACH_PORT_NULL) {
                return;
        }
        mach_port_t replyPort = MACH_PORT_NULL;
        mach_port_options_t options = { .flags = MPO_CONTEXT_AS_GUARD | MPO_STRICT,
                .mpl = { 1 }};
        kern_return_t kr = mach_port_construct(mach_task_self(), &options, (mach_port_context_t)&replyPort, &replyPort);
        if (kr != KERN_SUCCESS) {
                return;
        }
        // Assemble a message
        mach_msg_header_t* h = buffer;
        h->msgh_bits         = MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND,MACH_MSG_TYPE_MAKE_SEND_ONCE);
        h->msgh_id           = msgId;
        h->msgh_local_port   = replyPort;
        h->msgh_remote_port  = sendPort;
        h->msgh_reserved     = 0;
        h->msgh_size         = sendSize;
        kr = mach_msg(h, MACH_SEND_MSG | MACH_RCV_MSG, h->msgh_size, bufferSize, replyPort, 0, MACH_PORT_NULL);
        mach_msg_destroy(h);
        if ( kr == MACH_SEND_INVALID_DEST ) {
                if (OSAtomicCompareAndSwap32(sendPort, 0, (volatile int32_t*)&dyld::gProcessInfo->notifyPorts[portSlot])) {
                        mach_port_deallocate(mach_task_self(), sendPort);
                }
        }
        mach_port_destruct(mach_task_self(), replyPort, 0, (mach_port_context_t)&replyPort);
}

static void notifyMonitoringDyld(bool unloading, unsigned imageCount, const struct mach_header* loadAddresses[],
                                                                 const char* imagePaths[])
{
        dyld3::ScopedTimer(DBG_DYLD_REMOTE_IMAGE_NOTIFIER, 0, 0, 0);
        for (int slot=0; slot < DYLD_MAX_PROCESS_INFO_NOTIFY_COUNT; ++slot) {
                if ( dyld::gProcessInfo->notifyPorts[slot] == 0) continue;
                unsigned entriesSize = imageCount*sizeof(dyld_process_info_image_entry);
                unsigned pathsSize = 0;
                for (unsigned j=0; j < imageCount; ++j) {
                        pathsSize += (strlen(imagePaths[j]) + 1);
                }
                unsigned totalSize = (sizeof(dyld_process_info_notify_header) + entriesSize + pathsSize + 127) & -128;   // align
                if ( totalSize > DYLD_PROCESS_INFO_NOTIFY_MAX_BUFFER_SIZE ) {
                        // Putting all image paths into one message would make buffer too big.
                        // Instead split into two messages.  Recurse as needed until paths fit in buffer.
                        unsigned imageHalfCount = imageCount/2;
                        notifyMonitoringDyld(unloading, imageHalfCount, loadAddresses, imagePaths);
                        notifyMonitoringDyld(unloading, imageCount - imageHalfCount, &loadAddresses[imageHalfCount], &imagePaths[imageHalfCount]);
                        return;
                }
                uint8_t buffer[totalSize + MAX_TRAILER_SIZE];
                dyld_process_info_notify_header* header = (dyld_process_info_notify_header*)buffer;
                header->version                 = 1;
                header->imageCount              = imageCount;
                header->imagesOffset    = sizeof(dyld_process_info_notify_header);
                header->stringsOffset   = sizeof(dyld_process_info_notify_header) + entriesSize;
                header->timestamp               = dyld::gProcessInfo->infoArrayChangeTimestamp;
                dyld_process_info_image_entry* entries = (dyld_process_info_image_entry*)&buffer[header->imagesOffset];
                char* const pathPoolStart = (char*)&buffer[header->stringsOffset];
                char* pathPool = pathPoolStart;
                for (unsigned j=0; j < imageCount; ++j) {
                        strcpy(pathPool, imagePaths[j]);
                        uint32_t len = (uint32_t)strlen(pathPool);
                        bzero(entries->uuid, 16);
                        dyld3::MachOFile* mf = (dyld3::MachOFile*)loadAddresses[j];
                        mf->getUuid(entries->uuid);
                        entries->loadAddress = (uint64_t)loadAddresses[j];
                        entries->pathStringOffset = (uint32_t)(pathPool - pathPoolStart);
                        entries->pathLength  = len;
                        pathPool += (len +1);
                        ++entries;
                }
                if (unloading) {
                        sendMessage(slot, DYLD_PROCESS_INFO_NOTIFY_UNLOAD_ID, totalSize, (mach_msg_header_t*)buffer, totalSize+MAX_TRAILER_SIZE);
                } else {
                        sendMessage(slot, DYLD_PROCESS_INFO_NOTIFY_LOAD_ID, totalSize, (mach_msg_header_t*)buffer, totalSize+MAX_TRAILER_SIZE);
                }
        }
}

static void notifyMonitoringDyldMain()
{
        dyld3::ScopedTimer(DBG_DYLD_REMOTE_IMAGE_NOTIFIER, 0, 0, 0);
        for (int slot=0; slot < DYLD_MAX_PROCESS_INFO_NOTIFY_COUNT; ++slot) {
                if ( dyld::gProcessInfo->notifyPorts[slot] == 0) continue;
                uint8_t buffer[sizeof(mach_msg_header_t) + MAX_TRAILER_SIZE];
                sendMessage(slot, DYLD_PROCESS_INFO_NOTIFY_MAIN_ID, sizeof(mach_msg_header_t), (mach_msg_header_t*)buffer, sizeof(mach_msg_header_t) + MAX_TRAILER_SIZE);
        }
}
#else
extern void notifyMonitoringDyldMain() VIS_HIDDEN;
extern void notifyMonitoringDyld(bool unloading, unsigned imageCount, const struct mach_header* loadAddresses[],
                                                                 const char* imagePaths[]) VIS_HIDDEN;
#endif

void notifyKernel(const ImageLoader& image, bool loading) {
        uint32_t baseCode = loading ? DBG_DYLD_UUID_MAP_A : DBG_DYLD_UUID_UNMAP_A;
        uuid_t uuid;
        image.getUUID(uuid);
        if ( image.inSharedCache() ) {
                dyld3::kdebug_trace_dyld_image(baseCode, image.getInstallPath(), (const uuid_t *)&uuid, {0}, {{ 0, 0 }}, image.machHeader());
        } else {
                fsid_t fsid = {{0, 0}};
                fsobj_id_t fsobj = {0};
                ino_t inode = image.getInode();
                fsobj.fid_objno = (uint32_t)inode;
                fsobj.fid_generation = (uint32_t)(inode>>32);
                fsid.val[0] = image.getDevice();
                dyld3::kdebug_trace_dyld_image(baseCode, image.getPath(), (const uuid_t *)&uuid, fsobj, fsid, image.machHeader());
        }
}

static void notifySingle(dyld_image_states state, const ImageLoader* image, ImageLoader::InitializerTimingList* timingInfo)
{
        //dyld::log("notifySingle(state=%d, image=%s)\n", state, image->getPath());
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sSingleHandlers);
        if ( handlers != NULL ) {
                dyld_image_info info;
                info.imageLoadAddress   = image->machHeader();
                info.imageFilePath              = image->getRealPath();
                info.imageFileModDate   = image->lastModified();
                for (std::vector<dyld_image_state_change_handler>::iterator it = handlers->begin(); it != handlers->end(); ++it) {
                        const char* result = (*it)(state, 1, &info);
                        if ( (result != NULL) && (state == dyld_image_state_mapped) ) {
                                //fprintf(stderr, "  image rejected by handler=%p\n", *it);
                                // make copy of thrown string so that later catch clauses can free it
                                const char* str = strdup(result);
                                throw str;
                        }
                }
        }
        if ( state == dyld_image_state_mapped ) {
                // <rdar://problem/7008875> Save load addr + UUID for images from outside the shared cache
                if ( !image->inSharedCache() ) {
                        dyld_uuid_info info;
                        if ( image->getUUID(info.imageUUID) ) {
                                info.imageLoadAddress = image->machHeader();
                                addNonSharedCacheImageUUID(info);
                        }
                }
        }
        if ( (state == dyld_image_state_dependents_initialized) && (sNotifyObjCInit != NULL) && image->notifyObjC() ) {
                uint64_t t0 = mach_absolute_time();
                dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_INIT, (uint64_t)image->machHeader(), 0, 0);
                (*sNotifyObjCInit)(image->getRealPath(), image->machHeader());
                uint64_t t1 = mach_absolute_time();
                uint64_t t2 = mach_absolute_time();
                uint64_t timeInObjC = t1-t0;
                uint64_t emptyTime = (t2-t1)*100;
                if ( (timeInObjC > emptyTime) && (timingInfo != NULL) ) {
                        timingInfo->addTime(image->getShortName(), timeInObjC);
                }
        }
    // mach message csdlc about dynamically unloaded images
        if ( image->addFuncNotified() && (state == dyld_image_state_terminated) ) {
                notifyKernel(*image, false);
                const struct mach_header* loadAddress[] = { image->machHeader() };
                const char* loadPath[] = { image->getPath() };
                notifyMonitoringDyld(true, 1, loadAddress, loadPath);
        }
}


//
// Normally, dyld_all_image_infos is only updated in batches after an entire
// graph is loaded.  But if there is an error loading the initial set of
// dylibs needed by the main executable, dyld_all_image_infos is not yet set 
// up, leading to usually brief crash logs.
//
// This function manually adds the images loaded so far to dyld::gProcessInfo.
// It should only be called before terminating.
//
void syncAllImages()
{
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); ++it) {
                dyld_image_info info;
                ImageLoader* image = *it;
                info.imageLoadAddress = image->machHeader();
                info.imageFilePath = image->getRealPath();
                info.imageFileModDate = image->lastModified();
                // add to all_image_infos if not already there
                bool found = false;
                int existingCount = dyld::gProcessInfo->infoArrayCount;
                const dyld_image_info* existing = dyld::gProcessInfo->infoArray;
                if ( existing != NULL ) {
                        for (int i=0; i < existingCount; ++i) {
                                if ( existing[i].imageLoadAddress == info.imageLoadAddress ) {
                                        //dyld::log("not adding %s\n", info.imageFilePath);
                                        found = true;
                                        break;
                                }
                        }
                }
                if ( ! found ) {
                        //dyld::log("adding %s\n", info.imageFilePath);
                        addImagesToAllImages(1, &info);
                }
        }
}


static int imageSorter(const void* l, const void* r)
{
        const ImageLoader* left = *((ImageLoader**)l);
        const ImageLoader* right= *((ImageLoader**)r);
        return left->compare(right);
}

static void notifyBatchPartial(dyld_image_states state, bool orLater, dyld_image_state_change_handler onlyHandler, bool preflightOnly, bool onlyObjCMappedNotification)
{
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sBatchHandlers);
        if ( (handlers != NULL) || ((state == dyld_image_state_bound) && (sNotifyObjCMapped != NULL)) ) {
                // don't use a vector because it will use malloc/free and we want notifcation to be low cost
        allImagesLock();
                dyld_image_info infos[allImagesCount()+1];
        ImageLoader* images[allImagesCount()+1];
        ImageLoader** end = images;
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            dyld_image_states imageState = (*it)->getState();
            if ( (imageState == state) || (orLater && (imageState > state)) )
                *end++ = *it;
        }
                if ( sBundleBeingLoaded != NULL ) {
                        dyld_image_states imageState = sBundleBeingLoaded->getState();
                        if ( (imageState == state) || (orLater && (imageState > state)) )
                                *end++ = sBundleBeingLoaded;
                }
        const char* dontLoadReason = NULL;
                uint32_t imageCount = (uint32_t)(end-images);
                if ( imageCount != 0 ) {
                        // sort bottom up
                        qsort(images, imageCount, sizeof(ImageLoader*), &imageSorter);

                        const mach_header* mhs[imageCount];
                        const char*        paths[imageCount];
                        uint32_t                   bulkNotifyImageCount = 0;

                        // build info array
                        for (unsigned int i=0; i < imageCount; ++i) {
                                dyld_image_info* p = &infos[i];
                                ImageLoader* image = images[i];
                                //dyld::log("  state=%d, name=%s\n", state, image->getPath());
                                p->imageLoadAddress = image->machHeader();
                                p->imageFilePath    = image->getRealPath();
                                p->imageFileModDate = image->lastModified();
                                // get these registered with the kernel as early as possible
                                if ( state == dyld_image_state_dependents_mapped)
                                        notifyKernel(*image, true);
                                // special case for add_image hook
                                if ( state == dyld_image_state_bound ) {
                                        if ( notifyAddImageCallbacks(image) ) {
                                                // Add this to the list of images to bulk notify
                                                mhs[bulkNotifyImageCount]   = infos[i].imageLoadAddress;
                                                paths[bulkNotifyImageCount] = infos[i].imageFilePath;
                                                ++bulkNotifyImageCount;
                                        }
                                }
                        }

                        if ( (state == dyld_image_state_bound) && !sAddBulkLoadImageCallbacks.empty() && (bulkNotifyImageCount != 0) ) {
                                for (LoadImageBulkCallback func : sAddBulkLoadImageCallbacks) {
                                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)mhs[0], (uint64_t)func, 0);
                                        (*func)(bulkNotifyImageCount, mhs, paths);
                                }
                        }
                }
#if SUPPORT_ACCELERATE_TABLES
                if ( sAllCacheImagesProxy != NULL ) {
                        unsigned cacheCount = sAllCacheImagesProxy->appendImagesToNotify(state, orLater, &infos[imageCount]);
                        // support _dyld_register_func_for_add_image()
                        if ( state == dyld_image_state_bound ) {
                                for (ImageCallback callback : sAddImageCallbacks) {
                                        for (unsigned i=0; i < cacheCount; ++i) {
                                                dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[imageCount+i].imageLoadAddress, (uint64_t)(*callback), 0);
                                                (*callback)(infos[imageCount+i].imageLoadAddress, sSharedCacheLoadInfo.slide);
                                        }
                                }
                                for (LoadImageCallback func : sAddLoadImageCallbacks) {
                                        for (unsigned i=0; i < cacheCount; ++i) {
                                                dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[imageCount+i].imageLoadAddress, (uint64_t)(*func), 0);
                                                (*func)(infos[imageCount+i].imageLoadAddress, infos[imageCount+i].imageFilePath, false);
                                        }
                                }
                                if ( !sAddBulkLoadImageCallbacks.empty() ) {
                                        const mach_header* bulk_mhs[cacheCount];
                                        const char*        bulk_paths[cacheCount];
                                        for (int i=0; i < cacheCount; ++i) {
                                                bulk_mhs[i]   = infos[imageCount+i].imageLoadAddress;
                                                bulk_paths[i] = infos[imageCount+i].imageFilePath;
                                        }
                                        for (LoadImageBulkCallback func : sAddBulkLoadImageCallbacks) {
                                                dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)bulk_mhs[0], (uint64_t)func, 0);
                                                (*func)(cacheCount, bulk_mhs, bulk_paths);
                                        }
                                }
                        }
                        imageCount += cacheCount;
                }
#endif
                if ( imageCount != 0 ) {
                        if ( !onlyObjCMappedNotification ) {
                                if ( onlyHandler != NULL ) {
                                        const char* result = NULL;
                                        if ( result == NULL ) {
                                                result = (*onlyHandler)(state, imageCount, infos);
                                        }
                                        if ( (result != NULL) && (state == dyld_image_state_dependents_mapped) ) {
                                                //fprintf(stderr, "  images rejected by handler=%p\n", onlyHandler);
                                                // make copy of thrown string so that later catch clauses can free it
                                                dontLoadReason = strdup(result);
                                        }
                                }
                                else {
                                        // call each handler with whole array
                                        if ( handlers != NULL ) {
                                                for (std::vector<dyld_image_state_change_handler>::iterator it = handlers->begin(); it != handlers->end(); ++it) {
                                                        const char* result = (*it)(state, imageCount, infos);
                                                        if ( (result != NULL) && (state == dyld_image_state_dependents_mapped) ) {
                                                                //fprintf(stderr, "  images rejected by handler=%p\n", *it);
                                                                // make copy of thrown string so that later catch clauses can free it
                                                                dontLoadReason = strdup(result);
                                                                break;
                                                        }
                                                }
                                        }
                                }
                        }
                        // tell objc about new images
                        if ( (onlyHandler == NULL) && ((state == dyld_image_state_bound) || (orLater && (dyld_image_state_bound > state))) && (sNotifyObjCMapped != NULL) ) {
                                const char* paths[imageCount];
                                const mach_header* mhs[imageCount];
                                unsigned objcImageCount = 0;
                                for (int i=0; i < imageCount; ++i) {
                                        ImageLoader* image = findImageByMachHeader(infos[i].imageLoadAddress);
                                        bool hasObjC = false;
                                        if ( image != NULL ) {
                                                if ( image->objCMappedNotified() )
                                                        continue;
                                                hasObjC = image->notifyObjC();
                                        }
#if SUPPORT_ACCELERATE_TABLES
                                        else if ( sAllCacheImagesProxy != NULL ) {
                                                const mach_header* mh;
                                                const char* path;
                                                unsigned index;
                                                if ( sAllCacheImagesProxy->addressInCache(infos[i].imageLoadAddress, &mh, &path, &index) ) {
                                                        hasObjC = (mh->flags & MH_HAS_OBJC);
                                                }
                                        }
#endif
                                        if ( hasObjC ) {
                                                paths[objcImageCount] = infos[i].imageFilePath;
                                                mhs[objcImageCount]   = infos[i].imageLoadAddress;
                                                ++objcImageCount;
                                                if ( image != NULL )
                                                        image->setObjCMappedNotified();
                                        }
                                }
                                if ( objcImageCount != 0 ) {
                                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_MAP, 0, 0, 0);
                                        uint64_t t0 = mach_absolute_time();
                                        (*sNotifyObjCMapped)(objcImageCount, paths, mhs);
                                        uint64_t t1 = mach_absolute_time();
                                        ImageLoader::fgTotalObjCSetupTime += (t1-t0);
                                }
                        }
                }
        allImagesUnlock();
        if ( dontLoadReason != NULL )
            throw dontLoadReason;
                if ( !preflightOnly && (state == dyld_image_state_dependents_mapped) ) {
                        const struct mach_header* loadAddresses[imageCount];
                        const char* loadPaths[imageCount];
                        for(uint32_t i = 0; i<imageCount; ++i) {
                                loadAddresses[i] = infos[i].imageLoadAddress;
                                loadPaths[i] = infos[i].imageFilePath;
                        }
                        notifyMonitoringDyld(false, imageCount, loadAddresses, loadPaths);
                }
        }
}

static void notifyBatch(dyld_image_states state, bool preflightOnly)
{
        notifyBatchPartial(state, false, NULL, preflightOnly, false);
}

#if __MAC_OS_X_VERSION_MIN_REQUIRED
static
void coresymbolication_load_notifier(void* connection, uint64_t timestamp, const char* path, const struct mach_header* mh)
{
        const struct mach_header* loadAddress[] = { mh };
        const char* loadPath[] = { path };
        notifyMonitoringDyld(false, 1, loadAddress, loadPath);
}

static
void coresymbolication_unload_notifier(void* connection, uint64_t timestamp, const char* path, const struct mach_header* mh)
{
        const struct mach_header* loadAddress = { mh };
        const char* loadPath = { path };
        notifyMonitoringDyld(true, 1, &loadAddress, &loadPath);
}

static
kern_return_t legacy_task_register_dyld_image_infos(task_t task, dyld_kernel_image_info_array_t dyld_images,
                                                                                         mach_msg_type_number_t dyld_imagesCnt)
{
        return KERN_SUCCESS;
}

static
kern_return_t legacy_task_unregister_dyld_image_infos(task_t task, dyld_kernel_image_info_array_t dyld_images,
                                                                                           mach_msg_type_number_t dyld_imagesCnt)
{
        return KERN_SUCCESS;
}

static
kern_return_t legacy_task_get_dyld_image_infos(task_inspect_t task, dyld_kernel_image_info_array_t *dyld_images,
                                                                                mach_msg_type_number_t *dyld_imagesCnt)
{
        return KERN_SUCCESS;
}

static
kern_return_t legacy_task_register_dyld_shared_cache_image_info(task_t task, dyld_kernel_image_info_t dyld_cache_image,
                                                                                                                 boolean_t no_cache, boolean_t private_cache)
{
        return KERN_SUCCESS;
}

static
kern_return_t legacy_task_register_dyld_set_dyld_state(task_t task, uint8_t dyld_state)
{
        return KERN_SUCCESS;
}

static
kern_return_t legacy_task_register_dyld_get_process_state(task_t task, dyld_kernel_process_info_t *dyld_process_state)
{
        return KERN_SUCCESS;
}
#endif

// In order for register_func_for_add_image() callbacks to to be called bottom up,
// we need to maintain a list of root images. The main executable is usally the
// first root. Any images dynamically added are also roots (unless already loaded).
// If DYLD_INSERT_LIBRARIES is used, those libraries are first.
static void addRootImage(ImageLoader* image)
{
        //dyld::log("addRootImage(%p, %s)\n", image, image->getPath());
        // add to list of roots
        sImageRoots.push_back(image);
}


static void clearAllDepths()
{
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++)
                (*it)->clearDepth();
}

static void printAllDepths()
{
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++)
                dyld::log("%03d %s\n",  (*it)->getDepth(), (*it)->getShortName());
}


static unsigned int imageCount()
{
    allImagesLock();
                unsigned int result = (unsigned int)sAllImages.size();
    allImagesUnlock();
        return (result);
}


static void setNewProgramVars(const ProgramVars& newVars)
{
        // make a copy of the pointers to program variables
        gLinkContext.programVars = newVars;
        
        // now set each program global to their initial value
        *gLinkContext.programVars.NXArgcPtr = gLinkContext.argc;
        *gLinkContext.programVars.NXArgvPtr = gLinkContext.argv;
        *gLinkContext.programVars.environPtr = gLinkContext.envp;
        *gLinkContext.programVars.__prognamePtr = gLinkContext.progname;
}

#if SUPPORT_OLD_CRT_INITIALIZATION
static void setRunInitialzersOldWay()
{
        gRunInitializersOldWay = true;          
}
#endif

static bool sandboxBlocked(const char* path, const char* kind)
{
#if TARGET_OS_SIMULATOR
        // sandbox calls not yet supported in simulator runtime
        return false;
#else
        sandbox_filter_type filter = (sandbox_filter_type)(SANDBOX_FILTER_PATH | SANDBOX_CHECK_NO_REPORT);
        return ( sandbox_check(getpid(), kind, filter, path) > 0 );
#endif
}

bool sandboxBlockedMmap(const char* path)
{
        return sandboxBlocked(path, "file-map-executable");
}

bool sandboxBlockedOpen(const char* path)
{
        return sandboxBlocked(path, "file-read-data");
}

bool sandboxBlockedStat(const char* path)
{
        return sandboxBlocked(path, "file-read-metadata");
}


static void addDynamicReference(ImageLoader* from, ImageLoader* to) {
        // don't add dynamic reference if target is in the shared cache (since it can't be unloaded)
        if ( to->inSharedCache() )
                return;

        // don't add dynamic reference if there already is a static one
        if ( from->dependsOn(to) )
                return;
        
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        // don't add if this combination already exists
        OSSpinLockLock(&sDynamicReferencesLock);
        for (std::vector<ImageLoader::DynamicReference>::iterator it=sDynamicReferences.begin(); it != sDynamicReferences.end(); ++it) {
                if ( (it->from == from) && (it->to == to) ) {
                        OSSpinLockUnlock(&sDynamicReferencesLock);
                        return;
                }
        }

        //dyld::log("addDynamicReference(%s, %s\n", from->getShortName(), to->getShortName());
        ImageLoader::DynamicReference t;
        t.from = from;
        t.to = to;
        sDynamicReferences.push_back(t);
        OSSpinLockUnlock(&sDynamicReferencesLock);
#pragma clang diagnostic pop
}

static void addImage(ImageLoader* image)
{
        // add to master list
    allImagesLock();
        sAllImages.push_back(image);
    allImagesUnlock();
        
        // update mapped ranges
        uintptr_t lastSegStart = 0;
        uintptr_t lastSegEnd = 0;
        for(unsigned int i=0, e=image->segmentCount(); i < e; ++i) {
                if ( image->segUnaccessible(i) ) 
                        continue;
                uintptr_t start = image->segActualLoadAddress(i);
                uintptr_t end = image->segActualEndAddress(i);
                if ( start == lastSegEnd ) {
                        // two segments are contiguous, just record combined segments
                        lastSegEnd = end;
                }
                else {
                        // non-contiguous segments, record last (if any)
                        if ( lastSegEnd != 0 )
                                addMappedRange(image, lastSegStart, lastSegEnd);
                        lastSegStart = start;
                        lastSegEnd = end;
                }               
        }
        if ( lastSegEnd != 0 )
                addMappedRange(image, lastSegStart, lastSegEnd);

        
        if ( gLinkContext.verboseLoading || (sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH && (sMainExecutable!=NULL) && sMainExecutable->isLinked()) ) {
                const char *imagePath = image->getPath();
                uuid_t imageUUID;
                if ( image->getUUID(imageUUID) ) {
                        uuid_string_t imageUUIDStr;
                        uuid_unparse_upper(imageUUID, imageUUIDStr);
                        dyld::log("dyld: loaded: <%s> %s\n", imageUUIDStr, imagePath);
                }
                else {
                        dyld::log("dyld: loaded: %s\n", imagePath);
                }
        }
        
}

//
// Helper for std::remove_if
//
class RefUsesImage {
public:
        RefUsesImage(ImageLoader* image) : _image(image) {}
        bool operator()(const ImageLoader::DynamicReference& ref) const {
                return ( (ref.from == _image) || (ref.to == _image) );
        }
private:
        ImageLoader* _image;
};



void removeImage(ImageLoader* image)
{
        // if has dtrace DOF section, tell dtrace it is going away, then remove from sImageFilesNeedingDOFUnregistration
        for (std::vector<RegisteredDOF>::iterator it=sImageFilesNeedingDOFUnregistration.begin(); it != sImageFilesNeedingDOFUnregistration.end(); ) {
                if ( it->mh == image->machHeader() ) {
                        unregisterDOF(it->registrationID);
                        sImageFilesNeedingDOFUnregistration.erase(it);
                        // don't increment iterator, the erase caused next element to be copied to where this iterator points
                }
                else {
                        ++it;
                }
        }
        
        // tell all registered remove image handlers about this
        // do this before removing image from internal data structures so that the callback can query dyld about the image
        if ( image->getState() >= dyld_image_state_bound ) {
                sRemoveImageCallbacksInUse = true; // This only runs inside dyld's global lock, so ok to use a global for the in-use flag.
                for (std::vector<ImageCallback>::iterator it=sRemoveImageCallbacks.begin(); it != sRemoveImageCallbacks.end(); it++) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_REMOVE_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*it), 0);
                        (*it)(image->machHeader(), image->getSlide());
                }
                sRemoveImageCallbacksInUse = false;

                if ( sNotifyObjCUnmapped !=  NULL && image->notifyObjC() )
                        (*sNotifyObjCUnmapped)(image->getRealPath(), image->machHeader());
        }
        
        // notify 
        notifySingle(dyld_image_state_terminated, image, NULL);
        
        // remove from mapped images table
        removedMappedRanges(image);

        // remove from master list
    allImagesLock();
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
            if ( *it == image ) {
                sAllImages.erase(it);
                break;
            }
        }
    allImagesUnlock();
        
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        // remove from sDynamicReferences
        OSSpinLockLock(&sDynamicReferencesLock);
                sDynamicReferences.erase(std::remove_if(sDynamicReferences.begin(), sDynamicReferences.end(), RefUsesImage(image)), sDynamicReferences.end());
        OSSpinLockUnlock(&sDynamicReferencesLock);
#pragma clang diagnostic pop

        // flush find-by-address cache (do this after removed from master list, so there is no chance it can come back)
        if ( sLastImageByAddressCache == image )
                sLastImageByAddressCache = NULL;

        // if in root list, pull it out 
        for (std::vector<ImageLoader*>::iterator it=sImageRoots.begin(); it != sImageRoots.end(); it++) {
                if ( *it == image ) {
                        sImageRoots.erase(it);
                        break;
                }
        }

        // If this image is the potential canonical definition of any weak defs, then set them to a tombstone value
        if ( gLinkContext.weakDefMapInitialized && image->hasCoalescedExports() ) {
                Diagnostics diag;
                const dyld3::MachOAnalyzer* ma = (const dyld3::MachOAnalyzer*)image->machHeader();
                ma->forEachWeakDef(diag, ^(const char *symbolName, uintptr_t imageOffset, bool isFromExportTrie) {
                        auto it = gLinkContext.weakDefMap.find(symbolName);
                        assert(it != gLinkContext.weakDefMap.end());
                        it->second = { nullptr, 0 };
                        if ( !isFromExportTrie ) {
                                // The string was already duplicated if we are an export trie
                                // so only strdup as we are the nlist
                                size_t hash1 = ImageLoader::HashCString::hash(it->first);
                                it->first = strdup(it->first);
                                size_t hash2 = ImageLoader::HashCString::hash(it->first);
                                assert(hash1 == hash2);
                        }
                });
        }

        // log if requested
        if ( gLinkContext.verboseLoading || (sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH && (sMainExecutable!=NULL) && sMainExecutable->isLinked()) ) {
                const char *imagePath = image->getPath();
                uuid_t imageUUID;
                if ( image->getUUID(imageUUID) ) {
                        uuid_string_t imageUUIDStr;
                        uuid_unparse_upper(imageUUID, imageUUIDStr);
                        dyld::log("dyld: unloaded: <%s> %s\n", imageUUIDStr, imagePath);
                }
                else {
                        dyld::log("dyld: unloaded: %s\n", imagePath);
                }
        }

        // tell gdb, new way
        removeImageFromAllImages(image->machHeader());
}


void runImageStaticTerminators(ImageLoader* image)
{
        // if in termination list, pull it out and run terminator
        bool mightBeMore;
        do {
                mightBeMore = false;
                for (std::vector<ImageLoader*>::iterator it=sImageFilesNeedingTermination.begin(); it != sImageFilesNeedingTermination.end(); it++) {
                        if ( *it == image ) {
                                sImageFilesNeedingTermination.erase(it);
                                if (gLogAPIs) dyld::log("dlclose(), running static terminators for %p %s\n", image, image->getShortName());
                                image->doTermination(gLinkContext);
                                mightBeMore = true;
                                break;
                        }
                }
        } while ( mightBeMore );
}

static void terminationRecorder(ImageLoader* image)
{
        sImageFilesNeedingTermination.push_back(image);
}

const char* getExecutablePath()
{
        return sExecPath;
}

static void runAllStaticTerminators(void* extra)
{
        try {
                const size_t imageCount = sImageFilesNeedingTermination.size();
                for(size_t i=imageCount; i > 0; --i){
                        ImageLoader* image = sImageFilesNeedingTermination[i-1];
                        image->doTermination(gLinkContext);
                }
                sImageFilesNeedingTermination.clear();
                notifyBatch(dyld_image_state_terminated, false);
        }
        catch (const char* msg) {
                halt(msg);
        }
}

void initializeMainExecutable()
{
        // record that we've reached this step
        gLinkContext.startedInitializingMainExecutable = true;

        // run initialzers for any inserted dylibs
        ImageLoader::InitializerTimingList initializerTimes[allImagesCount()];
        initializerTimes[0].count = 0;
        const size_t rootCount = sImageRoots.size();
        if ( rootCount > 1 ) {
                for(size_t i=1; i < rootCount; ++i) {
                        sImageRoots[i]->runInitializers(gLinkContext, initializerTimes[0]);
                }
        }
        
        // run initializers for main executable and everything it brings up 
        sMainExecutable->runInitializers(gLinkContext, initializerTimes[0]);
        
        // register cxa_atexit() handler to run static terminators in all loaded images when this process exits
        if ( gLibSystemHelpers != NULL ) 
                (*gLibSystemHelpers->cxa_atexit)(&runAllStaticTerminators, NULL, NULL);

        // dump info if requested
        if ( sEnv.DYLD_PRINT_STATISTICS )
                ImageLoader::printStatistics((unsigned int)allImagesCount(), initializerTimes[0]);
        if ( sEnv.DYLD_PRINT_STATISTICS_DETAILS )
                ImageLoaderMachO::printStatisticsDetails((unsigned int)allImagesCount(), initializerTimes[0]);
}

bool mainExecutablePrebound()
{
        return sMainExecutable->usablePrebinding(gLinkContext);
}

ImageLoader* mainExecutable()
{
        return sMainExecutable;
}




#if SUPPORT_VERSIONED_PATHS

// forward reference
static bool getDylibVersionAndInstallname(const char* dylibPath, uint32_t* version, char* installName);


//
// Examines a dylib file and if its current_version is newer than the installed
// dylib at its install_name, then add the dylib file to sDylibOverrides.
//
static void checkDylibOverride(const char* dylibFile)
{
        //dyld::log("checkDylibOverride('%s')\n", dylibFile);
        uint32_t altVersion;
        char sysInstallName[PATH_MAX];
        if ( getDylibVersionAndInstallname(dylibFile, &altVersion, sysInstallName) && (sysInstallName[0] =='/') ) {
                //dyld::log("%s has version 0x%08X and install name %s\n", dylibFile, altVersion, sysInstallName);
                uint32_t sysVersion;
                if ( getDylibVersionAndInstallname(sysInstallName, &sysVersion, NULL) ) {
                        //dyld::log("%s has version 0x%08X\n", sysInstallName, sysVersion);
                        if ( altVersion > sysVersion ) {
                                //dyld::log("override found: %s -> %s\n", sysInstallName, dylibFile);
                                // see if there already is an override for this dylib
                                bool entryExists = false;
                                for (std::vector<DylibOverride>::iterator it = sDylibOverrides.begin(); it != sDylibOverrides.end(); ++it) {
                                        if ( strcmp(it->installName, sysInstallName) == 0 ) {
                                                entryExists = true;
                                                uint32_t prevVersion;
                                                if ( getDylibVersionAndInstallname(it->override, &prevVersion, NULL) ) {
                                                        if ( altVersion > prevVersion ) {
                                                                // found an even newer override
                                                                free((void*)(it->override));
                                                                char resolvedPath[PATH_MAX];
                                                                if ( realpath(dylibFile, resolvedPath) != NULL )
                                                                        it->override = strdup(resolvedPath);
                                                                else
                                                                        it->override = strdup(dylibFile);
                                                                break;
                                                        }
                                                }
                                        }
                                }
                                if ( ! entryExists ) {
                                        DylibOverride entry;
                                        entry.installName = strdup(sysInstallName);
                                        char resolvedPath[PATH_MAX];
                                        if ( realpath(dylibFile, resolvedPath) != NULL )
                                                entry.override = strdup(resolvedPath);
                                        else
                                                entry.override = strdup(dylibFile);
                                        sDylibOverrides.push_back(entry);
                                        //dyld::log("added override: %s -> %s\n", entry.installName, entry.override);
                                }
                        }
                }
        }
        
}

static void checkDylibOverridesInDir(const char* dirPath)
{
        //dyld::log("checkDylibOverridesInDir('%s')\n", dirPath);
        char dylibPath[PATH_MAX];
        long dirPathLen = strlcpy(dylibPath, dirPath, PATH_MAX-1);
        if ( dirPathLen >= PATH_MAX )
                return;
        DIR* dirp = opendir(dirPath);
        if ( dirp != NULL) {
                dirent entry;
                dirent* entp = NULL;
                while ( readdir_r(dirp, &entry, &entp) == 0 ) {
                        if ( entp == NULL )
                                break;
                        if ( entp->d_type != DT_REG ) 
                                continue;
                        dylibPath[dirPathLen] = '/';
                        dylibPath[dirPathLen+1] = '\0';
                        if ( strlcat(dylibPath, entp->d_name, PATH_MAX) >= PATH_MAX )
                                continue;
                        checkDylibOverride(dylibPath);
                }
                closedir(dirp);
        }
}


static void checkFrameworkOverridesInDir(const char* dirPath)
{
        //dyld::log("checkFrameworkOverridesInDir('%s')\n", dirPath);
        char frameworkPath[PATH_MAX];
        long dirPathLen = strlcpy(frameworkPath, dirPath, PATH_MAX-1);
        if ( dirPathLen >= PATH_MAX )
                return;
        DIR* dirp = opendir(dirPath);
        if ( dirp != NULL) {
                dirent entry;
                dirent* entp = NULL;
                while ( readdir_r(dirp, &entry, &entp) == 0 ) {
                        if ( entp == NULL )
                                break;
                        if ( entp->d_type != DT_DIR ) 
                                continue;
                        frameworkPath[dirPathLen] = '/';
                        frameworkPath[dirPathLen+1] = '\0';
                        int dirNameLen = (int)strlen(entp->d_name);
                        if ( dirNameLen < 11 )
                                continue;
                        if ( strcmp(&entp->d_name[dirNameLen-10], ".framework") != 0 )
                                continue;
                        if ( strlcat(frameworkPath, entp->d_name, PATH_MAX) >= PATH_MAX )
                                continue;
                        if ( strlcat(frameworkPath, "/", PATH_MAX) >= PATH_MAX )
                                continue;
                        if ( strlcat(frameworkPath, entp->d_name, PATH_MAX) >= PATH_MAX )
                                continue;
                        frameworkPath[strlen(frameworkPath)-10] = '\0';
                        checkDylibOverride(frameworkPath);
                }
                closedir(dirp);
        }
}
#endif // SUPPORT_VERSIONED_PATHS


//
// Turns a colon separated list of strings into a NULL terminated array 
// of string pointers. If mainExecutableDir param is not NULL,
// substitutes @loader_path with main executable's dir.
//
static const char** parseColonList(const char* list, const char* mainExecutableDir)
{
        static const char* sEmptyList[] = { NULL };

        if ( list[0] == '\0' ) 
                return sEmptyList;
        
        int colonCount = 0;
        for(const char* s=list; *s != '\0'; ++s) {
                if (*s == ':') 
                        ++colonCount;
        }
        
        int index = 0;
        const char* start = list;
        char** result = new char*[colonCount+2];
        for(const char* s=list; *s != '\0'; ++s) {
                if (*s == ':') {
                        size_t len = s-start;
                        if ( (mainExecutableDir != NULL) && (strncmp(start, "@loader_path/", 13) == 0) ) {
                                if ( !gLinkContext.allowAtPaths ) {
                                        dyld::log("dyld: warning: @loader_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
                                        continue;
                                }
                                size_t mainExecDirLen = strlen(mainExecutableDir);
                                char* str = new char[mainExecDirLen+len+1];
                                strcpy(str, mainExecutableDir);
                                strlcat(str, &start[13], mainExecDirLen+len+1);
                                str[mainExecDirLen+len-13] = '\0';
                                start = &s[1];
                                result[index++] = str;
                        }
                        else if ( (mainExecutableDir != NULL) && (strncmp(start, "@executable_path/", 17) == 0) ) {
                                if ( !gLinkContext.allowAtPaths ) {
                                        dyld::log("dyld: warning: @executable_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
                                        continue;
                                }
                                size_t mainExecDirLen = strlen(mainExecutableDir);
                                char* str = new char[mainExecDirLen+len+1];
                                strcpy(str, mainExecutableDir);
                                strlcat(str, &start[17], mainExecDirLen+len+1);
                                str[mainExecDirLen+len-17] = '\0';
                                start = &s[1];
                                result[index++] = str;
                        }
                        else {
                                char* str = new char[len+1];
                                strncpy(str, start, len);
                                str[len] = '\0';
                                start = &s[1];
                                result[index++] = str;
                        }
                }
        }
        size_t len = strlen(start);
        if ( (mainExecutableDir != NULL) && (strncmp(start, "@loader_path/", 13) == 0) ) {
                if ( !gLinkContext.allowAtPaths ) {
                        dyld::log("dyld: warning: @loader_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
                }
                else
                {
                        size_t mainExecDirLen = strlen(mainExecutableDir);
                        char* str = new char[mainExecDirLen+len+1];
                        strcpy(str, mainExecutableDir);
                        strlcat(str, &start[13], mainExecDirLen+len+1);
                        str[mainExecDirLen+len-13] = '\0';
                        result[index++] = str;
                }
        }
        else if ( (mainExecutableDir != NULL) && (strncmp(start, "@executable_path/", 17) == 0) ) {
                if ( !gLinkContext.allowAtPaths ) {
                        dyld::log("dyld: warning: @executable_path/ ignored because of amfi policy (Codesign main executable with Library Validation to allow @ paths)\n");
                }
                else
                {
                        size_t mainExecDirLen = strlen(mainExecutableDir);
                        char* str = new char[mainExecDirLen+len+1];
                        strcpy(str, mainExecutableDir);
                        strlcat(str, &start[17], mainExecDirLen+len+1);
                        str[mainExecDirLen+len-17] = '\0';
                        result[index++] = str;
                }
        }
        else {
                char* str = new char[len+1];
                strcpy(str, start);
                result[index++] = str;
        }
        result[index] = NULL;
        
        //dyld::log("parseColonList(%s)\n", list);
        //for(int i=0; result[i] != NULL; ++i)
        //      dyld::log("  %s\n", result[i]);
        return (const char**)result;
}

static void     appendParsedColonList(const char* list, const char* mainExecutableDir, const char* const ** storage)
{
        const char** newlist = parseColonList(list, mainExecutableDir);
        if ( *storage == NULL ) {
                // first time, just set
                *storage = newlist;
        }
        else {
                // need to append to existing list
                const char* const* existing = *storage;
                int count = 0;
                for(int i=0; existing[i] != NULL; ++i)
                        ++count;
                for(int i=0; newlist[i] != NULL; ++i)
                        ++count;
                const char** combinedList = new const char*[count+2];
                int index = 0;
                for(int i=0; existing[i] != NULL; ++i)
                        combinedList[index++] = existing[i];
                for(int i=0; newlist[i] != NULL; ++i)
                        combinedList[index++] = newlist[i];
                combinedList[index] = NULL;
                delete[] newlist; // free array, note: strings in newList may be leaked
                *storage = combinedList;
        }
}

#if __MAC_OS_X_VERSION_MIN_REQUIRED
static void paths_expand_roots(const char **paths, const char *key, const char *val)
{
//      assert(val != NULL);
//      assert(paths != NULL);
        if(NULL != key) {
                size_t keyLen = strlen(key);
                for(int i=0; paths[i] != NULL; ++i) {
                        if ( strncmp(paths[i], key, keyLen) == 0 ) {
                                char* newPath = new char[strlen(val) + (strlen(paths[i]) - keyLen) + 1];
                                strcpy(newPath, val);
                                strcat(newPath, &paths[i][keyLen]);
                                paths[i] = newPath;
                        }
                }
        }
        return;
}

static void removePathWithPrefix(const char* paths[], const char* prefix)
{
    size_t prefixLen = strlen(prefix);
    int skip = 0;
    int i;
    for(i = 0; paths[i] != NULL; ++i) {
        if ( strncmp(paths[i], prefix, prefixLen) == 0 )
            ++skip;
        else
            paths[i-skip] = paths[i];
    }
    paths[i-skip] = NULL;
}
#endif


#if 0
static void paths_dump(const char **paths)
{
//   assert(paths != NULL);
  const char **strs = paths;
  while(*strs != NULL)
  {
    dyld::log("\"%s\"\n", *strs);
    strs++;
  }
  return;
}
#endif



static void printOptions(const char* argv[])
{
        uint32_t i = 0;
        while ( NULL != argv[i] ) {
                dyld::log("opt[%i] = \"%s\"\n", i, argv[i]);
                i++;
        }
}

static void printEnvironmentVariables(const char* envp[])
{
        while ( NULL != *envp ) {
                dyld::log("%s\n", *envp);
                envp++;
        }
}

void processDyldEnvironmentVariable(const char* key, const char* value, const char* mainExecutableDir)
{
        if ( strcmp(key, "DYLD_FRAMEWORK_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FRAMEWORK_PATH);
                sEnv.hasOverride = true;
        }
        else if ( strcmp(key, "DYLD_FALLBACK_FRAMEWORK_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FALLBACK_FRAMEWORK_PATH);
                sEnv.hasOverride = true;
        }
        else if ( strcmp(key, "DYLD_LIBRARY_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_LIBRARY_PATH);
                sEnv.hasOverride = true;
        }
        else if ( strcmp(key, "DYLD_FALLBACK_LIBRARY_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FALLBACK_LIBRARY_PATH);
                sEnv.hasOverride = true;
        }
#if SUPPORT_ROOT_PATH
        else if ( (strcmp(key, "DYLD_ROOT_PATH") == 0) || (strcmp(key, "DYLD_PATHS_ROOT") == 0) ) {
                if ( strcmp(value, "/") != 0 ) {
                        gLinkContext.rootPaths = parseColonList(value, mainExecutableDir);
                        for (int i=0; gLinkContext.rootPaths[i] != NULL; ++i) {
                                if ( gLinkContext.rootPaths[i][0] != '/' ) {
                                        dyld::warn("DYLD_ROOT_PATH not used because it contains a non-absolute path\n");
                                        gLinkContext.rootPaths = NULL;
                                        break;
                                }
                        }
                }
                sEnv.hasOverride = true;
        }
#endif
        else if ( strcmp(key, "DYLD_IMAGE_SUFFIX") == 0 ) {
                gLinkContext.imageSuffix = parseColonList(value, NULL);
                sEnv.hasOverride = true;
        }
        else if ( strcmp(key, "DYLD_INSERT_LIBRARIES") == 0 ) {
                sEnv.DYLD_INSERT_LIBRARIES = parseColonList(value, NULL);
#if SUPPORT_ACCELERATE_TABLES
                sDisableAcceleratorTables = true;
#endif
                sEnv.hasOverride = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_OPTS") == 0 ) {
                sEnv.DYLD_PRINT_OPTS = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_ENV") == 0 ) {
                sEnv.DYLD_PRINT_ENV = true;
        }
        else if ( strcmp(key, "DYLD_DISABLE_DOFS") == 0 ) {
                sEnv.DYLD_DISABLE_DOFS = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_LIBRARIES") == 0 ) {
                gLinkContext.verboseLoading = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_LIBRARIES_POST_LAUNCH") == 0 ) {
                sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH = true;
        }
        else if ( strcmp(key, "DYLD_BIND_AT_LAUNCH") == 0 ) {
                sEnv.DYLD_BIND_AT_LAUNCH = true;
        }
        else if ( strcmp(key, "DYLD_FORCE_FLAT_NAMESPACE") == 0 ) {
                gLinkContext.bindFlat = true;
        }
        else if ( strcmp(key, "DYLD_NEW_LOCAL_SHARED_REGIONS") == 0 ) {
                // ignore, no longer relevant but some scripts still set it
        }
        else if ( strcmp(key, "DYLD_NO_FIX_PREBINDING") == 0 ) {
        }
        else if ( strcmp(key, "DYLD_PREBIND_DEBUG") == 0 ) {
                gLinkContext.verbosePrebinding = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_INITIALIZERS") == 0 ) {
                gLinkContext.verboseInit = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_DOFS") == 0 ) {
                gLinkContext.verboseDOF = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_STATISTICS") == 0 ) {
                sEnv.DYLD_PRINT_STATISTICS = true;
#if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
                // <rdar://problem/26614838> DYLD_PRINT_STATISTICS no longer logs to xcode console for device apps
                sForceStderr = true;
#endif
        }
        else if ( strcmp(key, "DYLD_PRINT_TO_STDERR") == 0 ) {
#if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
                // <rdar://problem/26633440> DYLD_PRINT_STATISTICS no longer logs to xcode console for device apps
                sForceStderr = true;
#endif
        }
        else if ( strcmp(key, "DYLD_PRINT_STATISTICS_DETAILS") == 0 ) {
                sEnv.DYLD_PRINT_STATISTICS_DETAILS = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_SEGMENTS") == 0 ) {
                gLinkContext.verboseMapping = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_BINDINGS") == 0 ) {
                gLinkContext.verboseBind = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_WEAK_BINDINGS") == 0 ) {
                gLinkContext.verboseWeakBind = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_REBASINGS") == 0 ) {
                gLinkContext.verboseRebase = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_APIS") == 0 ) {
                gLogAPIs = true;
        }
#if SUPPORT_ACCELERATE_TABLES
        else if ( strcmp(key, "DYLD_PRINT_APIS_APP") == 0 ) {
                gLogAppAPIs = true;
        }
#endif
        else if ( strcmp(key, "DYLD_PRINT_WARNINGS") == 0 ) {
                gLinkContext.verboseWarnings = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_RPATHS") == 0 ) {
                gLinkContext.verboseRPaths = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_INTERPOSING") == 0 ) {
                gLinkContext.verboseInterposing = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_CODE_SIGNATURES") == 0 ) {
                gLinkContext.verboseCodeSignatures = true;
        }
        else if ( (strcmp(key, "DYLD_SHARED_REGION") == 0) && gLinkContext.allowEnvVarsSharedCache ) {
                if ( strcmp(value, "private") == 0 ) {
                        gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
                }
                else if ( strcmp(value, "avoid") == 0 ) {
                        gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
                }
                else if ( strcmp(value, "use") == 0 ) {
                        gLinkContext.sharedRegionMode = ImageLoader::kUseSharedRegion;
                }
                else if ( value[0] == '\0' ) {
                        gLinkContext.sharedRegionMode = ImageLoader::kUseSharedRegion;
                }
                else {
                        dyld::warn("unknown option to DYLD_SHARED_REGION.  Valid options are: use, private, avoid\n");
                }
        }
        else if ( (strcmp(key, "DYLD_SHARED_CACHE_DIR") == 0) && gLinkContext.allowEnvVarsSharedCache  ) {
                sSharedCacheOverrideDir = value;
        }
        else if ( strcmp(key, "DYLD_USE_CLOSURES") == 0 ) {
                // Handled elsewhere
        }
        else if ( strcmp(key, "DYLD_FORCE_INVALID_CACHE_CLOSURES") == 0 ) {
                if ( dyld3::internalInstall() ) {
                        sForceInvalidSharedCacheClosureFormat = true;
                }
        }
        else if ( strcmp(key, "DYLD_IGNORE_PREBINDING") == 0 ) {
                if ( strcmp(value, "all") == 0 ) {
                        gLinkContext.prebindUsage = ImageLoader::kUseNoPrebinding;
                }
                else if ( strcmp(value, "app") == 0 ) {
                        gLinkContext.prebindUsage = ImageLoader::kUseAllButAppPredbinding;
                }
                else if ( strcmp(value, "nonsplit") == 0 ) {
                        gLinkContext.prebindUsage = ImageLoader::kUseSplitSegPrebinding;
                }
                else if ( value[0] == '\0' ) {
                        gLinkContext.prebindUsage = ImageLoader::kUseSplitSegPrebinding;
                }
                else {
                        dyld::warn("unknown option to DYLD_IGNORE_PREBINDING.  Valid options are: all, app, nonsplit\n");
                }
        }
#if SUPPORT_VERSIONED_PATHS
        else if ( strcmp(key, "DYLD_VERSIONED_LIBRARY_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_VERSIONED_LIBRARY_PATH);
        #if SUPPORT_ACCELERATE_TABLES
                sDisableAcceleratorTables = true;
        #endif
                sEnv.hasOverride = true;
        }
        else if ( strcmp(key, "DYLD_VERSIONED_FRAMEWORK_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_VERSIONED_FRAMEWORK_PATH);
        #if SUPPORT_ACCELERATE_TABLES
                sDisableAcceleratorTables = true;
        #endif
                sEnv.hasOverride = true;
        }
#endif
#if !TARGET_OS_SIMULATOR
        else if ( (strcmp(key, "DYLD_PRINT_TO_FILE") == 0) && (mainExecutableDir == NULL) && gLinkContext.allowEnvVarsSharedCache ) {
                int fd = open(value, O_WRONLY | O_CREAT | O_APPEND, 0644);
                if ( fd != -1 ) {
                        sLogfile = fd;
                        sLogToFile = true;
                }
                else {
                        dyld::log("dyld: could not open DYLD_PRINT_TO_FILE='%s', errno=%d\n", value, errno);
                }
        }
        else if ( (strcmp(key, "DYLD_SKIP_MAIN") == 0)) {
                if ( dyld3::internalInstall() )
                        sSkipMain = true;
        }
        else if ( (strcmp(key, "DYLD_JUST_BUILD_CLOSURE") == 0) ) {
                // handled elsewhere
        }
#endif
        else if (strcmp(key, "DYLD_FORCE_PLATFORM") == 0) {
                // handled elsewhere
        }
        else if (strcmp(key, "DYLD_AMFI_FAKE") == 0) {
                // handled elsewhere
        }
        else {
                dyld::warn("unknown environment variable: %s\n", key);
        }
}


#if SUPPORT_LC_DYLD_ENVIRONMENT
static void checkLoadCommandEnvironmentVariables()
{
        // <rdar://problem/8440934> Support augmenting dyld environment variables in load commands
        const uint32_t cmd_count = sMainExecutableMachHeader->ncmds;
        const struct load_command* const cmds = (struct load_command*)(((char*)sMainExecutableMachHeader)+sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_DYLD_ENVIRONMENT:
                        {
                                const struct dylinker_command* envcmd = (struct dylinker_command*)cmd;
                                const char* keyEqualsValue = (char*)envcmd + envcmd->name.offset;
                                char mainExecutableDir[strlen(sExecPath)+2];
                                strcpy(mainExecutableDir, sExecPath);
                                char* lastSlash = strrchr(mainExecutableDir, '/');
                                if ( lastSlash != NULL)
                                        lastSlash[1] = '\0';
                                // only process variables that start with DYLD_ and end in _PATH
                                if ( (strncmp(keyEqualsValue, "DYLD_", 5) == 0) ) {
                                        const char* equals = strchr(keyEqualsValue, '=');
                                        if ( equals != NULL ) {
                                                if ( strncmp(&equals[-5], "_PATH", 5) == 0 ) {
                                                        const char* value = &equals[1];
                                                        const size_t keyLen = equals-keyEqualsValue;
                                                        // <rdar://problem/22799635> don't let malformed load command overflow stack
                                                        if ( keyLen < 40 ) {
                                                                char key[keyLen+1];
                                                                strncpy(key, keyEqualsValue, keyLen);
                                                                key[keyLen] = '\0';
                                                                //dyld::log("processing: %s\n", keyEqualsValue);
                                                                //dyld::log("mainExecutableDir: %s\n", mainExecutableDir);
#if SUPPORT_ROOT_PATH
                                                                if ( (strcmp(key, "DYLD_ROOT_PATH") == 0) || (strcmp(key, "DYLD_PATHS_ROOT") == 0) )
                                                                        continue;
#endif
                                                                processDyldEnvironmentVariable(key, value, mainExecutableDir);
                                                        }
                                                }
                                        }
                                }
                        }
                        break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
}
#endif // SUPPORT_LC_DYLD_ENVIRONMENT   

        
static bool hasCodeSignatureLoadCommand(const macho_header* mh)
{
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                if (cmd->cmd == LC_CODE_SIGNATURE) 
                        return true;
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        return false;
}
        

#if SUPPORT_VERSIONED_PATHS
static void checkVersionedPaths()
{
        // search DYLD_VERSIONED_LIBRARY_PATH directories for dylibs and check if they are newer
        if ( sEnv.DYLD_VERSIONED_LIBRARY_PATH != NULL ) {
                for(const char* const* lp = sEnv.DYLD_VERSIONED_LIBRARY_PATH; *lp != NULL; ++lp) {
                        checkDylibOverridesInDir(*lp);
                }
        }
        
        // search DYLD_VERSIONED_FRAMEWORK_PATH directories for dylibs and check if they are newer
        if ( sEnv.DYLD_VERSIONED_FRAMEWORK_PATH != NULL ) {
                for(const char* const* fp = sEnv.DYLD_VERSIONED_FRAMEWORK_PATH; *fp != NULL; ++fp) {
                        checkFrameworkOverridesInDir(*fp);
                }
        }
}
#endif  


#if __MAC_OS_X_VERSION_MIN_REQUIRED
//
// For security, setuid programs ignore DYLD_* environment variables.
// Additionally, the DYLD_* enviroment variables are removed
// from the environment, so that any child processes don't see them.
//
static void pruneEnvironmentVariables(const char* envp[], const char*** applep)
{
#if SUPPORT_LC_DYLD_ENVIRONMENT
        checkLoadCommandEnvironmentVariables();
#endif

    // Are we testing dyld on an internal config?
    if ( _simple_getenv(envp, "DYLD_SKIP_MAIN") != NULL ) {
                if ( dyld3::internalInstall() )
            sSkipMain = true;
    }

        // delete all DYLD_* and LD_LIBRARY_PATH environment variables
        int removedCount = 0;
        const char** d = envp;
        for(const char** s = envp; *s != NULL; s++) {
                
            if ( (strncmp(*s, "DYLD_", 5) != 0) && (strncmp(*s, "LD_LIBRARY_PATH=", 16) != 0) ) {
                        *d++ = *s;
                }
                else {
                        ++removedCount;
                }
        }
        *d++ = NULL;
        // slide apple parameters
        if ( removedCount > 0 ) {
                *applep = d;
                do {
                        *d = d[removedCount];
                } while ( *d++ != NULL );
                for(int i=0; i < removedCount; ++i)
                        *d++ = NULL;
        }
        
        // disable framework and library fallback paths for setuid binaries rdar://problem/4589305
        sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = NULL;
        sEnv.DYLD_FALLBACK_LIBRARY_PATH = NULL;

        if ( removedCount > 0 )
                strlcat(sLoadingCrashMessage, ", ignoring DYLD_* env vars", sizeof(sLoadingCrashMessage));
}
#endif

static void defaultUninitializedFallbackPaths(const char* envp[])
{
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        if ( !gLinkContext.allowClassicFallbackPaths ) {
                sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = sRestrictedFrameworkFallbackPaths;
                sEnv.DYLD_FALLBACK_LIBRARY_PATH   = sRestrictedLibraryFallbackPaths;
                return;
        }

        // default value for DYLD_FALLBACK_FRAMEWORK_PATH, if not set in environment
        const char* home = _simple_getenv(envp, "HOME");;
        if ( sEnv.DYLD_FALLBACK_FRAMEWORK_PATH == NULL ) {
                const char** fpaths = sFrameworkFallbackPaths;
                if ( home == NULL )
                        removePathWithPrefix(fpaths, "$HOME");
                else
                        paths_expand_roots(fpaths, "$HOME", home);
                sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = fpaths;
        }

    // default value for DYLD_FALLBACK_LIBRARY_PATH, if not set in environment
        if ( sEnv.DYLD_FALLBACK_LIBRARY_PATH == NULL ) {
                const char** lpaths = sLibraryFallbackPaths;
                if ( home == NULL )
                        removePathWithPrefix(lpaths, "$HOME");
                else
                        paths_expand_roots(lpaths, "$HOME", home);
                sEnv.DYLD_FALLBACK_LIBRARY_PATH = lpaths;
        }
#else
        if ( sEnv.DYLD_FALLBACK_FRAMEWORK_PATH == NULL )
                sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = sFrameworkFallbackPaths;

        if ( sEnv.DYLD_FALLBACK_LIBRARY_PATH == NULL )
                sEnv.DYLD_FALLBACK_LIBRARY_PATH = sLibraryFallbackPaths;
#endif
}


static void checkEnvironmentVariables(const char* envp[])
{
        if ( !gLinkContext.allowEnvVarsPath && !gLinkContext.allowEnvVarsPrint )
                return;
        const char** p;
        for(p = envp; *p != NULL; p++) {
                const char* keyEqualsValue = *p;
            if ( strncmp(keyEqualsValue, "DYLD_", 5) == 0 ) {
                        const char* equals = strchr(keyEqualsValue, '=');
                        if ( equals != NULL ) {
                                strlcat(sLoadingCrashMessage, "\n", sizeof(sLoadingCrashMessage));
                                strlcat(sLoadingCrashMessage, keyEqualsValue, sizeof(sLoadingCrashMessage));
                                const char* value = &equals[1];
                                const size_t keyLen = equals-keyEqualsValue;
                                char key[keyLen+1];
                                strncpy(key, keyEqualsValue, keyLen);
                                key[keyLen] = '\0';
                                if ( (strncmp(key, "DYLD_PRINT_", 11) == 0) && !gLinkContext.allowEnvVarsPrint )
                                        continue;
                                processDyldEnvironmentVariable(key, value, NULL);
                        }
                }
                else if ( strncmp(keyEqualsValue, "LD_LIBRARY_PATH=", 16) == 0 ) {
                        const char* path = &keyEqualsValue[16];
                        sEnv.LD_LIBRARY_PATH = parseColonList(path, NULL);
                }
        }

#if SUPPORT_LC_DYLD_ENVIRONMENT
        checkLoadCommandEnvironmentVariables();
#endif // SUPPORT_LC_DYLD_ENVIRONMENT   
        
#if SUPPORT_ROOT_PATH
        // <rdar://problem/11281064> DYLD_IMAGE_SUFFIX and DYLD_ROOT_PATH cannot be used together
        if ( (gLinkContext.imageSuffix != NULL && *gLinkContext.imageSuffix != NULL) && (gLinkContext.rootPaths != NULL) ) {
                dyld::warn("Ignoring DYLD_IMAGE_SUFFIX because DYLD_ROOT_PATH is used.\n");
                gLinkContext.imageSuffix = NULL; // this leaks allocations from parseColonList
        }
#endif
}

#if __x86_64__ && !TARGET_OS_SIMULATOR
static bool isGCProgram(const macho_header* mh, uintptr_t slide)
{
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_SEGMENT_COMMAND:
                        {
                                const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                                if (strcmp(seg->segname, "__DATA") == 0) {
                                        const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                                        const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
                                        for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                                                if (strncmp(sect->sectname, "__objc_imageinfo", 16) == 0) {
                                                        const uint32_t*  objcInfo = (uint32_t*)(sect->addr + slide);
                                                        return (objcInfo[1] & 6); // 6 = (OBJC_IMAGE_SUPPORTS_GC | OBJC_IMAGE_REQUIRES_GC)
                                                }
                                        }
                                }
                        }
                        break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        return false;
}
#endif

static void getHostInfo(const macho_header* mainExecutableMH, uintptr_t mainExecutableSlide)
{
#if CPU_SUBTYPES_SUPPORTED
#if __ARM_ARCH_7K__
        sHostCPU                = CPU_TYPE_ARM;
        sHostCPUsubtype = CPU_SUBTYPE_ARM_V7K;
#elif __ARM_ARCH_7A__
        sHostCPU                = CPU_TYPE_ARM;
        sHostCPUsubtype = CPU_SUBTYPE_ARM_V7;
#elif __ARM_ARCH_6K__
        sHostCPU                = CPU_TYPE_ARM;
        sHostCPUsubtype = CPU_SUBTYPE_ARM_V6;
#elif __ARM_ARCH_7F__
        sHostCPU                = CPU_TYPE_ARM;
        sHostCPUsubtype = CPU_SUBTYPE_ARM_V7F;
#elif __ARM_ARCH_7S__
        sHostCPU                = CPU_TYPE_ARM;
        sHostCPUsubtype = CPU_SUBTYPE_ARM_V7S;
#elif __ARM64_ARCH_8_32__
        sHostCPU                = CPU_TYPE_ARM64_32;
        sHostCPUsubtype = CPU_SUBTYPE_ARM64_32_V8;
#elif __arm64e__
        sHostCPU                = CPU_TYPE_ARM64;
        sHostCPUsubtype = CPU_SUBTYPE_ARM64E;
#elif __arm64__
        sHostCPU                = CPU_TYPE_ARM64;
        sHostCPUsubtype = CPU_SUBTYPE_ARM64_V8;
#else
        struct host_basic_info info;
        mach_msg_type_number_t count = HOST_BASIC_INFO_COUNT;
        mach_port_t hostPort = mach_host_self();
        kern_return_t result = host_info(hostPort, HOST_BASIC_INFO, (host_info_t)&info, &count);
        if ( result != KERN_SUCCESS )
                throw "host_info() failed";
        sHostCPU                = info.cpu_type;
        sHostCPUsubtype = info.cpu_subtype;
        mach_port_deallocate(mach_task_self(), hostPort);
  #if __x86_64__
          // host_info returns CPU_TYPE_I386 even for x86_64.  Override that here so that
          // we don't need to mask the cpu type later.
          sHostCPU = CPU_TYPE_X86_64;
        #if !TARGET_OS_SIMULATOR
          sHaswell = (sHostCPUsubtype == CPU_SUBTYPE_X86_64_H);
          // <rdar://problem/18528074> x86_64h: Fall back to the x86_64 slice if an app requires GC.
          if ( sHaswell ) {
                if ( isGCProgram(mainExecutableMH, mainExecutableSlide) ) {
                        // When running a GC program on a haswell machine, don't use and 'h slices
                        sHostCPUsubtype = CPU_SUBTYPE_X86_64_ALL;
                        sHaswell = false;
                        gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
                }
          }
        #endif
  #endif
#endif
#endif
}

static void checkSharedRegionDisable(const dyld3::MachOLoaded* mainExecutableMH, uintptr_t mainExecutableSlide)
{
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        // if main executable has segments that overlap the shared region,
        // then disable using the shared region
        if ( mainExecutableMH->intersectsRange(SHARED_REGION_BASE, SHARED_REGION_SIZE) ) {
                gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
                if ( gLinkContext.verboseMapping )
                        dyld::warn("disabling shared region because main executable overlaps\n");
        }
#if __i386__
        if ( !gLinkContext.allowEnvVarsPath ) {
                // <rdar://problem/15280847> use private or no shared region for suid processes
                gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
        }
#endif
#endif
        // iOS cannot run without shared region
}

bool validImage(const ImageLoader* possibleImage)
{
    const size_t imageCount = sAllImages.size();
    for(size_t i=0; i < imageCount; ++i) {
        if ( possibleImage == sAllImages[i] ) {
            return true;
        }
    }
        return false;
}

uint32_t getImageCount()
{
        return (uint32_t)sAllImages.size();
}

ImageLoader* getIndexedImage(unsigned int index)
{
        if ( index < sAllImages.size() )
                return sAllImages[index];
        return NULL;
}

ImageLoader* findImageByMachHeader(const struct mach_header* target)
{
        return findMappedRange((uintptr_t)target);
}


ImageLoader* findImageContainingAddress(const void* addr)
{
  #if SUPPORT_ACCELERATE_TABLES
        if ( sAllCacheImagesProxy != NULL ) {
                const mach_header* mh;
                const char* path;
                unsigned index;
                if ( sAllCacheImagesProxy->addressInCache(addr, &mh, &path, &index) )
                        return sAllCacheImagesProxy;
        }
  #endif
        return findMappedRange((uintptr_t)addr);
}


ImageLoader* findImageContainingSymbol(const void* symbol)
{
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* anImage = *it;
                if ( anImage->containsSymbol(symbol) )
                        return anImage;
        }
        return NULL;
}



void forEachImageDo( void (*callback)(ImageLoader*, void* userData), void* userData)
{
        const size_t imageCount = sAllImages.size();
        for(size_t i=0; i < imageCount; ++i) {
                ImageLoader* anImage = sAllImages[i];
                (*callback)(anImage, userData);
        }
}

ImageLoader* findLoadedImage(const struct stat& stat_buf)
{
        const size_t imageCount = sAllImages.size();
        for(size_t i=0; i < imageCount; ++i){
                ImageLoader* anImage = sAllImages[i];
                if ( anImage->statMatch(stat_buf) )
                        return anImage;
        }
        return NULL;
}

// based on ANSI-C strstr()
static const char* strrstr(const char* str, const char* sub) 
{
        const size_t sublen = strlen(sub);
        for(const char* p = &str[strlen(str)]; p != str; --p) {
                if ( strncmp(p, sub, sublen) == 0 )
                        return p;
        }
        return NULL;
}


//
// Find framework path
//
//  /path/foo.framework/foo                                                             =>   foo.framework/foo  
//  /path/foo.framework/Versions/A/foo                                  =>   foo.framework/Versions/A/foo
//  /path/foo.framework/Frameworks/bar.framework/bar    =>   bar.framework/bar
//  /path/foo.framework/Libraries/bar.dylb                              =>   NULL
//  /path/foo.framework/bar                                                             =>   NULL
//
// Returns NULL if not a framework path
//
static const char* getFrameworkPartialPath(const char* path)
{
        const char* dirDot = strrstr(path, ".framework/");
        if ( dirDot != NULL ) {
                const char* dirStart = dirDot;
                for ( ; dirStart >= path; --dirStart) {
                        if ( (*dirStart == '/') || (dirStart == path) ) {
                                const char* frameworkStart = &dirStart[1];
                                if ( dirStart == path )
                                        --frameworkStart;
                                size_t len = dirDot - frameworkStart;
                                char framework[len+1];
                                strncpy(framework, frameworkStart, len);
                                framework[len] = '\0';
                                const char* leaf = strrchr(path, '/');
                                if ( leaf != NULL ) {
                                        if ( strcmp(framework, &leaf[1]) == 0 ) {
                                                return frameworkStart;
                                        }
                                        if (  gLinkContext.imageSuffix != NULL ) {
                                                // some debug frameworks have install names that end in _debug
                                                if ( strncmp(framework, &leaf[1], len) == 0 ) {
                                                        for (const char* const* suffix=gLinkContext.imageSuffix; *suffix != NULL; ++suffix) {
                                                                if ( strcmp(*suffix, &leaf[len+1]) == 0 )
                                                                        return frameworkStart;
                                                        }
                                                }
                                        }
                                }
                        }
                }
        }
        return NULL;
}


static const char* getLibraryLeafName(const char* path)
{
        const char* start = strrchr(path, '/');
        if ( start != NULL )
                return &start[1];
        else
                return path;
}


// only for architectures that use cpu-sub-types
#if CPU_SUBTYPES_SUPPORTED 

const cpu_subtype_t CPU_SUBTYPE_END_OF_LIST = -1;


//
//      A fat file may contain multiple sub-images for the same CPU type.
//      In that case, dyld picks which sub-image to use by scanning a table
//      of preferred cpu-sub-types for the running cpu.  
//      
//      There is one row in the table for each cpu-sub-type on which dyld might run.
//  The first entry in a row is that cpu-sub-type.  It is followed by all
//      cpu-sub-types that can run on that cpu, if preferred order.  Each row ends with 
//      a "SUBTYPE_ALL" (to denote that images written to run on any cpu-sub-type are usable), 
//  followed by one or more CPU_SUBTYPE_END_OF_LIST to pad out this row.
//


#if __arm__
//      
//     ARM sub-type lists
//
const int kARM_RowCount = 8;
static const cpu_subtype_t kARM[kARM_RowCount][9] = { 

        // armv7f can run: v7f, v7, v6, v5, and v4
        {  CPU_SUBTYPE_ARM_V7F, CPU_SUBTYPE_ARM_V7, CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST },

        // armv7k can run: v7k
        {  CPU_SUBTYPE_ARM_V7K, CPU_SUBTYPE_END_OF_LIST },

        // armv7s can run: v7s, v7, v7f, v7k, v6, v5, and v4
        {  CPU_SUBTYPE_ARM_V7S, CPU_SUBTYPE_ARM_V7, CPU_SUBTYPE_ARM_V7F, CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST },

        // armv7 can run: v7, v6, v5, and v4
        {  CPU_SUBTYPE_ARM_V7, CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST },
        
        // armv6 can run: v6, v5, and v4
        {  CPU_SUBTYPE_ARM_V6, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
        
        // xscale can run: xscale, v5, and v4
        {  CPU_SUBTYPE_ARM_XSCALE, CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
        
        // armv5 can run: v5 and v4
        {  CPU_SUBTYPE_ARM_V5TEJ, CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },

        // armv4 can run: v4
        {  CPU_SUBTYPE_ARM_V4T, CPU_SUBTYPE_ARM_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
};
#endif

#if __arm64__
//
//     ARM64 sub-type lists
//
const int kARM64_RowCount = 2;
static const cpu_subtype_t kARM64[kARM64_RowCount][4] = {

        // armv64e can run: 64e, 64
        {  CPU_SUBTYPE_ARM64E, CPU_SUBTYPE_ARM64_V8, CPU_SUBTYPE_ARM64_ALL, CPU_SUBTYPE_END_OF_LIST },

        // armv64 can run: 64
        {  CPU_SUBTYPE_ARM64_V8, CPU_SUBTYPE_ARM64_ALL, CPU_SUBTYPE_END_OF_LIST },
};

#if __ARM64_ARCH_8_32__
const int kARM64_32_RowCount = 2;
static const cpu_subtype_t kARM64_32[kARM64_32_RowCount][4] = {

        // armv64_32 can run: v8
        {  CPU_SUBTYPE_ARM64_32_V8, CPU_SUBTYPE_END_OF_LIST },

        // armv64 can run: 64
        {  CPU_SUBTYPE_ARM64_V8, CPU_SUBTYPE_ARM64_ALL, CPU_SUBTYPE_END_OF_LIST },
};
#endif
        
#endif

#if __x86_64__
//      
//     x86_64 sub-type lists
//
const int kX86_64_RowCount = 2;
static const cpu_subtype_t kX86_64[kX86_64_RowCount][5] = {

        // x86_64h can run: x86_64h, x86_64h(lib), x86_64(lib), and x86_64
        { CPU_SUBTYPE_X86_64_H, (cpu_subtype_t)(CPU_SUBTYPE_LIB64|CPU_SUBTYPE_X86_64_H), (cpu_subtype_t)(CPU_SUBTYPE_LIB64|CPU_SUBTYPE_X86_64_ALL), CPU_SUBTYPE_X86_64_ALL,  CPU_SUBTYPE_END_OF_LIST },

        // x86_64 can run: x86_64(lib) and x86_64
        { CPU_SUBTYPE_X86_64_ALL, (cpu_subtype_t)(CPU_SUBTYPE_LIB64|CPU_SUBTYPE_X86_64_ALL), CPU_SUBTYPE_END_OF_LIST },

};
#endif


// scan the tables above to find the cpu-sub-type-list for this machine
static const cpu_subtype_t* findCPUSubtypeList(cpu_type_t cpu, cpu_subtype_t subtype)
{
        switch (cpu) {
#if __arm__
                case CPU_TYPE_ARM:
                        for (int i=0; i < kARM_RowCount ; ++i) {
                                if ( kARM[i][0] == subtype )
                                        return kARM[i];
                        }
                        break;
#endif
#if __arm64__
                case CPU_TYPE_ARM64:
                        for (int i=0; i < kARM64_RowCount ; ++i) {
                                if ( kARM64[i][0] == subtype )
                                        return kARM64[i];
                        }
                        break;

#if __ARM64_ARCH_8_32__
                case CPU_TYPE_ARM64_32:
                        for (int i=0; i < kARM64_32_RowCount ; ++i) {
                                if ( kARM64_32[i][0] == subtype )
                                        return kARM64_32[i];
                        }
                        break;
#endif

#endif
#if __x86_64__
                case CPU_TYPE_X86_64:
                        for (int i=0; i < kX86_64_RowCount ; ++i) {
                                if ( kX86_64[i][0] == subtype )
                                        return kX86_64[i];
                        }
                        break;
#endif
        }
        return NULL;
}




// scan fat table-of-contents for best most preferred subtype
static bool fatFindBestFromOrderedList(cpu_type_t cpu, const cpu_subtype_t list[], const fat_header* fh, uint64_t* offset, uint64_t* len)
{
        const fat_arch* const archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
        for (uint32_t subTypeIndex=0; list[subTypeIndex] != CPU_SUBTYPE_END_OF_LIST; ++subTypeIndex) {
                for(uint32_t fatIndex=0; fatIndex < OSSwapBigToHostInt32(fh->nfat_arch); ++fatIndex) {
                        if ( ((cpu_type_t)OSSwapBigToHostInt32(archs[fatIndex].cputype) == cpu) 
                                && (list[subTypeIndex] == (cpu_subtype_t)OSSwapBigToHostInt32(archs[fatIndex].cpusubtype)) ) {
                                *offset = OSSwapBigToHostInt32(archs[fatIndex].offset);
                                *len = OSSwapBigToHostInt32(archs[fatIndex].size);
                                return true;
                        }
                }
        }
        return false;
}

// scan fat table-of-contents for exact match of cpu and cpu-sub-type
static bool fatFindExactMatch(cpu_type_t cpu, cpu_subtype_t subtype, const fat_header* fh, uint64_t* offset, uint64_t* len)
{
        const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
        for(uint32_t i=0; i < OSSwapBigToHostInt32(fh->nfat_arch); ++i) {
                if ( ((cpu_type_t)OSSwapBigToHostInt32(archs[i].cputype) == cpu)
                        && ((cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == subtype) ) {
                        *offset = OSSwapBigToHostInt32(archs[i].offset);
                        *len = OSSwapBigToHostInt32(archs[i].size);
                        return true;
                }
        }
        return false;
}

// scan fat table-of-contents for image with matching cpu-type and runs-on-all-sub-types
static bool fatFindRunsOnAllCPUs(cpu_type_t cpu, const fat_header* fh, uint64_t* offset, uint64_t* len)
{
        const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
        for(uint32_t i=0; i < OSSwapBigToHostInt32(fh->nfat_arch); ++i) {
                if ( (cpu_type_t)OSSwapBigToHostInt32(archs[i].cputype) == cpu) {
                        switch (cpu) {
#if __arm__
                                case CPU_TYPE_ARM:
                                        if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_ARM_ALL ) {
                                                *offset = OSSwapBigToHostInt32(archs[i].offset);
                                                *len = OSSwapBigToHostInt32(archs[i].size);
                                                return true;
                                        }
                                        break;
#endif
#if __arm64__
                                case CPU_TYPE_ARM64:
                                        if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_ARM64_ALL ) {
                                                *offset = OSSwapBigToHostInt32(archs[i].offset);
                                                *len = OSSwapBigToHostInt32(archs[i].size);
                                                return true;
                                        }
                                        break;
#endif
#if __x86_64__
                                case CPU_TYPE_X86_64:
                                        if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_X86_64_ALL ) {
                                                *offset = OSSwapBigToHostInt32(archs[i].offset);
                                                *len = OSSwapBigToHostInt32(archs[i].size);
                                                return true;
                                        }
                                        break;
#endif
                        }
                }
        }
        return false;
}

#endif // CPU_SUBTYPES_SUPPORTED


//
// Validate the fat_header and fat_arch array:
//
// 1) arch count would not cause array to extend past 4096 byte read buffer
// 2) no slice overlaps the fat_header and arch array
// 3) arch list does not contain duplicate cputype/cpusubtype tuples
// 4) arch list does not have two overlapping slices.
//
static bool fatValidate(const fat_header* fh)
{
        if ( fh->magic != OSSwapBigToHostInt32(FAT_MAGIC) )
                return false;

        // since only first 4096 bytes of file read, we can only handle up to 204 slices.
        const uint32_t sliceCount = OSSwapBigToHostInt32(fh->nfat_arch);
        if ( sliceCount > 204 )
                return false;

        // compare all slices looking for conflicts
        const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
        for (uint32_t i=0; i < sliceCount; ++i) {
                uint32_t i_offset     = OSSwapBigToHostInt32(archs[i].offset);
                uint32_t i_size       = OSSwapBigToHostInt32(archs[i].size);
                uint32_t i_cputype    = OSSwapBigToHostInt32(archs[i].cputype);
                uint32_t i_cpusubtype = OSSwapBigToHostInt32(archs[i].cpusubtype);
                uint32_t i_end        = i_offset + i_size;
                // slice cannot overlap with header
                if ( i_offset < 4096 )
                        return false;
                // slice size cannot overflow
                if ( i_end < i_offset )
                        return false;
                for (uint32_t j=i+1; j < sliceCount; ++j) {
                        uint32_t j_offset     = OSSwapBigToHostInt32(archs[j].offset);
                        uint32_t j_size       = OSSwapBigToHostInt32(archs[j].size);
                        uint32_t j_cputype    = OSSwapBigToHostInt32(archs[j].cputype);
                        uint32_t j_cpusubtype = OSSwapBigToHostInt32(archs[j].cpusubtype);
                        uint32_t j_end        = j_offset + j_size;
                        // duplicate slices types not allowed
                        if ( (i_cputype == j_cputype) && (i_cpusubtype == j_cpusubtype) )
                                return false;
                        // slice size cannot overflow
                        if ( j_end < j_offset )
                                return false;
                        // check for overlap of slices
                        if ( i_offset <= j_offset ) {
                                if ( j_offset < i_end )
                                        return false; //  j overlaps end of i
                        }
                        else {
                                //  j overlaps end of i
                                if ( i_offset < j_end )
                                        return false;  //  i overlaps end of j
                        }
                }
        }
        return true;
}

//
// A fat file may contain multiple sub-images for the same cpu-type,
// each optimized for a different cpu-sub-type (e.g G3 or G5).
// This routine picks the optimal sub-image.
//
static bool fatFindBest(const fat_header* fh, uint64_t* offset, uint64_t* len)
{
        if ( !fatValidate(fh) )
                return false;

#if CPU_SUBTYPES_SUPPORTED
        // assume all dylibs loaded must have same cpu type as main executable
        const cpu_type_t cpu = sMainExecutableMachHeader->cputype;

        // We only know the subtype to use if the main executable cpu type matches the host
        if ( cpu == sHostCPU ) {
                // get preference ordered list of subtypes
                const cpu_subtype_t* subTypePreferenceList = findCPUSubtypeList(cpu, sHostCPUsubtype);
        
                // use ordered list to find best sub-image in fat file
                if ( subTypePreferenceList != NULL ) {
                        if ( fatFindBestFromOrderedList(cpu, subTypePreferenceList, fh, offset, len) )
                                return true;
                }

                // if running cpu is not in list, try for an exact match
                if ( fatFindExactMatch(cpu, sHostCPUsubtype, fh, offset, len) )
                        return true;
        }
        
        // running on an uknown cpu, can only load generic code
        return fatFindRunsOnAllCPUs(cpu, fh, offset, len);
#else
        // just find first slice with matching architecture
        const fat_arch* archs = (fat_arch*)(((char*)fh)+sizeof(fat_header));
        for(uint32_t i=0; i < OSSwapBigToHostInt32(fh->nfat_arch); ++i) {
                if ( (cpu_type_t)OSSwapBigToHostInt32(archs[i].cputype) == sMainExecutableMachHeader->cputype) {
                        *offset = OSSwapBigToHostInt32(archs[i].offset);
                        *len = OSSwapBigToHostInt32(archs[i].size);
                        return true;
                }
        }
        return false;
#endif
}



//
// This is used to validate if a non-fat (aka thin or raw) mach-o file can be used
// on the current processor. //
bool isCompatibleMachO(const uint8_t* firstPage, const char* path)
{
#if CPU_SUBTYPES_SUPPORTED
        // It is deemed compatible if any of the following are true:
        //  1) mach_header subtype is in list of compatible subtypes for running processor
        //  2) mach_header subtype is same as running processor subtype
        //  3) mach_header subtype runs on all processor variants
        const mach_header* mh = (mach_header*)firstPage;
        if ( mh->magic == sMainExecutableMachHeader->magic ) {
                if ( mh->cputype == sMainExecutableMachHeader->cputype ) {
                        if ( mh->cputype == sHostCPU ) {
                                // get preference ordered list of subtypes that this machine can use
                                const cpu_subtype_t* subTypePreferenceList = findCPUSubtypeList(mh->cputype, sHostCPUsubtype);
                                if ( subTypePreferenceList != NULL ) {
                                        // if image's subtype is in the list, it is compatible
                                        for (const cpu_subtype_t* p = subTypePreferenceList; *p != CPU_SUBTYPE_END_OF_LIST; ++p) {
                                                if ( *p == mh->cpusubtype )
                                                        return true;
                                        }
                                        // have list and not in list, so not compatible
                                        throwf("incompatible cpu-subtype: 0x%08X in %s", mh->cpusubtype, path);
                                }
                                // unknown cpu sub-type, but if exact match for current subtype then ok to use
                                if ( mh->cpusubtype == sHostCPUsubtype ) 
                                        return true;
                        }
                        
                        // cpu type has no ordered list of subtypes
                        switch (mh->cputype) {
                                case CPU_TYPE_I386:
                                case CPU_TYPE_X86_64:
                                        // subtypes are not used or these architectures
                                        return true;
                        }
                }
        }
#else
        // For architectures that don't support cpu-sub-types
        // this just check the cpu type.
        const mach_header* mh = (mach_header*)firstPage;
        if ( mh->magic == sMainExecutableMachHeader->magic ) {
                if ( mh->cputype == sMainExecutableMachHeader->cputype ) {
                        return true;
                }
        }
#endif
        return false;
}




// The kernel maps in main executable before dyld gets control.  We need to 
// make an ImageLoader* for the already mapped in main executable.
static ImageLoaderMachO* instantiateFromLoadedImage(const macho_header* mh, uintptr_t slide, const char* path)
{
        // try mach-o loader
        if ( isCompatibleMachO((const uint8_t*)mh, path) ) {
                ImageLoader* image = ImageLoaderMachO::instantiateMainExecutable(mh, slide, path, gLinkContext);
                addImage(image);
                return (ImageLoaderMachO*)image;
        }
        
        throw "main executable not a known format";
}

#if SUPPORT_ACCELERATE_TABLES
static bool dylibsCanOverrideCache()
{
        if ( !dyld3::internalInstall() )
                return false;
        return ( (sSharedCacheLoadInfo.loadAddress != nullptr) && (sSharedCacheLoadInfo.loadAddress->header.cacheType == kDyldSharedCacheTypeDevelopment) );
}
#endif

const void* imMemorySharedCacheHeader()
{
        return sSharedCacheLoadInfo.loadAddress;
}


const char* getStandardSharedCacheFilePath()
{
        if ( sSharedCacheLoadInfo.loadAddress != nullptr )
                return sSharedCacheLoadInfo.path;
        else
                return nullptr;
}

bool hasInsertedOrInterposingLibraries() {
        return (sInsertedDylibCount > 0) || ImageLoader::haveInterposingTuples();
}


#if SUPPORT_VERSIONED_PATHS
static bool findInSharedCacheImage(const char* path, bool searchByPath, const struct stat* stat_buf, const macho_header** mh, const char** pathInCache, long* slide)
{
        dyld3::SharedCacheFindDylibResults results;
        if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &results) ) {
                *mh                      = (macho_header*)results.mhInCache;
                *pathInCache = results.pathInCache;
                *slide       = results.slideInCache;
                return true;
        }
        return false;
}
#endif

bool inSharedCache(const char* path)
{
        return dyld3::pathIsInSharedCacheImage(sSharedCacheLoadInfo, path);
}


static ImageLoader* checkandAddImage(ImageLoader* image, const LoadContext& context)
{
        // now sanity check that this loaded image does not have the same install path as any existing image
        const char* loadedImageInstallPath = image->getInstallPath();
        if ( image->isDylib() && (loadedImageInstallPath != NULL) && (loadedImageInstallPath[0] == '/') ) {
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                        ImageLoader* anImage = *it;
                        const char* installPath = anImage->getInstallPath();
                        if ( installPath != NULL) {
                                if ( strcmp(loadedImageInstallPath, installPath) == 0 ) {
                                        //dyld::log("duplicate(%s) => %p\n", installPath, anImage);
                                        removeImage(image);
                                        ImageLoader::deleteImage(image);
                                        return anImage;
                                }
                        }
                }
        }

        // some API's restrict what they can load
        if ( context.mustBeBundle && !image->isBundle() )
                throw "not a bundle";
        if ( context.mustBeDylib && !image->isDylib() )
                throw "not a dylib";

        // regular main executables cannot be loaded 
        if ( image->isExecutable() ) {
                if ( !context.canBePIE || !image->isPositionIndependentExecutable() )
                        throw "can't load a main executable";
        }
        
        // don't add bundles to global list, they can be loaded but not linked.  When linked it will be added to list
        if ( ! image->isBundle() ) 
                addImage(image);
        
        return image;
}

#if TARGET_OS_SIMULATOR 
static bool isSimulatorBinary(const uint8_t* firstPages, const char* path)
{
        const macho_header* mh = (macho_header*)firstPages;
        const uint32_t cmd_count = mh->ncmds;
        const load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
        const load_command* const cmdsEnd = (load_command*)((char*)cmds + mh->sizeofcmds);
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
        #if TARGET_OS_WATCH
                        case LC_VERSION_MIN_WATCHOS:
                                return true;
        #elif TARGET_OS_TV
                        case LC_VERSION_MIN_TVOS:
                                return true;
        #elif TARGET_OS_IOS
                        case LC_VERSION_MIN_IPHONEOS:
                                return true;
        #endif
                        case LC_VERSION_MIN_MACOSX:
                                // grandfather in a few libSystem dylibs
                                if ((strcmp(path, "/usr/lib/system/libsystem_kernel.dylib") == 0) ||
                                    (strcmp(path, "/usr/lib/system/libsystem_platform.dylib") == 0) ||
                                    (strcmp(path, "/usr/lib/system/libsystem_pthread.dylib") == 0) ||
                                    (strcmp(path, "/usr/lib/system/libsystem_platform_debug.dylib") == 0) ||
                                    (strcmp(path, "/usr/lib/system/libsystem_pthread_debug.dylib") == 0) ||
                                    (strcmp(path, "/sbin/launchd_sim_trampoline") == 0) ||
                                    (strcmp(path, "/usr/sbin/iokitsimd") == 0) ||
                                    (strcmp(path, "/usr/lib/system/host/liblaunch_sim.dylib") == 0))
                                        return true;
                                return false;
                        case LC_BUILD_VERSION:
                        {
                                // Same logic as above, but for LC_BUILD_VERSION instead of legacy load commands
                                const struct build_version_command* buildVersionCmd = (build_version_command*)cmd;
                                switch(buildVersionCmd->platform) {
                                        case PLATFORM_IOSSIMULATOR:
                                        case PLATFORM_TVOSSIMULATOR:
                                        case PLATFORM_WATCHOSSIMULATOR:
                                        case PLATFORM_WATCHOS:
                                                return true;
        #if TARGET_OS_IOSMAC
                                        case 6:
                                                return true;
        #endif
                                        case PLATFORM_MACOS:
                                                if ((strcmp(path, "/usr/lib/system/libsystem_kernel.dylib") == 0) ||
                                                        (strcmp(path, "/usr/lib/system/libsystem_platform.dylib") == 0) ||
                                                        (strcmp(path, "/usr/lib/system/libsystem_pthread.dylib") == 0) ||
                                                        (strcmp(path, "/usr/lib/system/libsystem_platform_debug.dylib") == 0) ||
                                                        (strcmp(path, "/usr/lib/system/libsystem_pthread_debug.dylib") == 0) ||
                                                        (strcmp(path, "/sbin/launchd_sim_trampoline") == 0) ||
                                                        (strcmp(path, "/usr/sbin/iokitsimd") == 0) ||
                                                        (strcmp(path, "/usr/lib/system/host/liblaunch_sim.dylib") == 0))
                                                        return true;
                                }
                        }
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                if ( cmd > cmdsEnd )
                        return false;
        }
        return false;
}
#endif

#if __MAC_OS_X_VERSION_MIN_REQUIRED
static bool iOSonMacDenied(const char* path)
{
        static char*  blackListBuffer   = nullptr;
        static size_t blackListSize     = 0;
        static bool   tried                     = false;
        if ( !tried ) {
                // only try to map file once
                blackListBuffer = (char*)mapFileReadOnly("/System/iOSSupport/dyld/macOS-deny-list.txt", blackListSize);
                tried = true;
        }
        __block bool result = false;
        if ( blackListBuffer != nullptr ) {
                dyld3::forEachLineInFile(blackListBuffer, blackListSize, ^(const char* line, bool& stop) {
                        // lines in the file are prefixes.  Any path that starts with one of these lines is allowed to be unzippered
                        size_t lineLen = strlen(line);
                        if ( (*line == '/') && strncmp(line, path, lineLen) == 0 ) {
                                result = true;
                                stop = true;
                        }
                });
        }
        return result;
}
#endif

// map in file and instantiate an ImageLoader
static ImageLoader* loadPhase6(int fd, const struct stat& stat_buf, const char* path, const LoadContext& context)
{
        //dyld::log("%s(%s)\n", __func__ , path);
        uint64_t fileOffset = 0;
        uint64_t fileLength = stat_buf.st_size;

        // validate it is a file (not directory)
        if ( (stat_buf.st_mode & S_IFMT) != S_IFREG ) 
                throw "not a file";

        uint8_t firstPages[MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE];
        uint8_t *firstPagesPtr = firstPages;
        bool shortPage = false;
        
        // min mach-o file is 4K
        if ( fileLength < 4096 ) {
                if ( pread(fd, firstPages, (size_t)fileLength, 0) != (ssize_t)fileLength )
                        throwf("pread of short file failed: %d", errno);
                shortPage = true;
        } 
        else {
                // optimistically read only first 4KB
                if ( pread(fd, firstPages, 4096, 0) != 4096 )
                        throwf("pread of first 4K failed: %d", errno);
        }
        
        // if fat wrapper, find usable sub-file
        const fat_header* fileStartAsFat = (fat_header*)firstPages;
        if ( fileStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
                if ( OSSwapBigToHostInt32(fileStartAsFat->nfat_arch) > ((4096 - sizeof(fat_header)) / sizeof(fat_arch)) )
                        throwf("fat header too large: %u entries", OSSwapBigToHostInt32(fileStartAsFat->nfat_arch));
                if ( fatFindBest(fileStartAsFat, &fileOffset, &fileLength) ) {
                        if ( (fileOffset+fileLength) > (uint64_t)(stat_buf.st_size) )
                                throwf("truncated fat file.  file length=%llu, but needed slice goes to %llu", stat_buf.st_size, fileOffset+fileLength);
                        if (pread(fd, firstPages, 4096, fileOffset) != 4096)
                                throwf("pread of fat file failed: %d", errno);
                }
                else {
                        throw "no matching architecture in universal wrapper";
                }
        }
        
        // try mach-o loader
        if ( shortPage ) 
                throw "file too short";

        if ( isCompatibleMachO(firstPages, path) ) {

                // only MH_BUNDLE, MH_DYLIB, and some MH_EXECUTE can be dynamically loaded
                const mach_header* mh = (mach_header*)firstPages;
                switch ( mh->filetype ) {
                        case MH_EXECUTE:
                        case MH_DYLIB:
                        case MH_BUNDLE:
                                break;
                        default:
                                throw "mach-o, but wrong filetype";
                }

                uint32_t headerAndLoadCommandsSize = sizeof(macho_header) + mh->sizeofcmds;
                if ( headerAndLoadCommandsSize > MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE )
                        throwf("malformed mach-o: load commands size (%u) > %u", headerAndLoadCommandsSize, MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE);

                if ( headerAndLoadCommandsSize > fileLength )
                        dyld::throwf("malformed mach-o: load commands size (%u) > mach-o file size (%llu)", headerAndLoadCommandsSize, fileLength);

                if ( headerAndLoadCommandsSize > 4096 ) {
                        // read more pages
                        unsigned readAmount = headerAndLoadCommandsSize - 4096;
                        if ( pread(fd, &firstPages[4096], readAmount, fileOffset+4096) != readAmount )
                                throwf("pread of extra load commands past 4KB failed: %d", errno);
                }

#if TARGET_OS_SIMULATOR 
                // <rdar://problem/14168872> dyld_sim should restrict loading osx binaries
                if ( !isSimulatorBinary(firstPages, path) ) {
        #if TARGET_OS_WATCH
                        throw "mach-o, but not built for watchOS simulator";
        #elif TARGET_OS_TV
                        throw "mach-o, but not built for tvOS simulator";
        #else
                        throw "mach-o, but not built for iOS simulator";
        #endif
                }
#endif

#if __MAC_OS_X_VERSION_MIN_REQUIRED
                if ( gLinkContext.iOSonMac ) {
                        const dyld3::MachOFile* mf = (dyld3::MachOFile*)firstPages;
                        bool supportsiOSMac = mf->supportsPlatform(dyld3::Platform::iOSMac);
                        if ( !supportsiOSMac && iOSonMacDenied(path) ) {
                                throw "mach-o, but not built for UIKitForMac";
                        }
                }
                else if ( gLinkContext.driverKit ) {
                        const dyld3::MachOFile* mf = (dyld3::MachOFile*)firstPages;
                        bool isDriverKitDylib = mf->supportsPlatform(dyld3::Platform::driverKit);
                        if ( !isDriverKitDylib ) {
                                throw "mach-o, but not built for driverkit";
                        }
                }
#endif

#if __arm64e__
                if ( (sMainExecutableMachHeader->cpusubtype == CPU_SUBTYPE_ARM64E) && (mh->cpusubtype != CPU_SUBTYPE_ARM64E) )
                        throw "arm64 dylibs cannot be loaded into arm64e processes";
#endif
                ImageLoader* image = nullptr;
                {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_MAP_IMAGE, path, 0, 0);
                        image = ImageLoaderMachO::instantiateFromFile(path, fd, firstPagesPtr, headerAndLoadCommandsSize, fileOffset, fileLength, stat_buf, gLinkContext);
                        timer.setData4((uint64_t)image->machHeader());
                }
                
                // validate
                return checkandAddImage(image, context);
        }
        
        // try other file formats here...
        
        
        // throw error about what was found
        switch (*(uint32_t*)firstPages) {
                case MH_MAGIC:
                case MH_CIGAM:
                case MH_MAGIC_64:
                case MH_CIGAM_64:
                        throw "mach-o, but wrong architecture";
                default:
                throwf("unknown file type, first eight bytes: 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X", 
                        firstPages[0], firstPages[1], firstPages[2], firstPages[3], firstPages[4], firstPages[5], firstPages[6],firstPages[7]);
        }
}


static ImageLoader* loadPhase5open(const char* path, const LoadContext& context, const struct stat& stat_buf, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);

        // open file (automagically closed when this function exits)
        FileOpener file(path);
                
        // just return NULL if file not found, but record any other errors
        if ( file.getFileDescriptor() == -1 ) {
                int err = errno;
                if ( err != ENOENT ) {
                        const char* newMsg;
                        if ( (err == EPERM) && sandboxBlockedOpen(path) )
                                newMsg = dyld::mkstringf("file system sandbox blocked open() of '%s'", path);
                        else
                                newMsg = dyld::mkstringf("%s: open() failed with errno=%d", path, err);
                        exceptions->push_back(newMsg);
                }
                return NULL;
        }

        try {
                return loadPhase6(file.getFileDescriptor(), stat_buf, path, context);
        }
        catch (const char* msg) {
                const char* newMsg = dyld::mkstringf("%s: %s", path, msg);
                exceptions->push_back(newMsg);
                free((void*)msg);
                return NULL;
        }
}

static bool isFileRelativePath(const char* path)
{
        if ( path[0] == '/' )
                return false;
        if ( path[0] != '.' )
                return true;
        if ( path[1] == '/' )
                return true;
        if ( (path[1] == '.') && (path[2] == '/') )
                return true;
        return false;
}


// try to open file
static ImageLoader* loadPhase5load(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);

        // <rdar://problem/47682983> don't allow file system relative paths in hardened programs
        if ( (exceptions != NULL) &&  !gLinkContext.allowEnvVarsPath && isFileRelativePath(path) ) {
                exceptions->push_back("file system relative paths not allowed in hardened programs");
                return NULL;
        }

#if SUPPORT_ACCELERATE_TABLES
        if ( sAllCacheImagesProxy != NULL ) {
                if ( sAllCacheImagesProxy->hasDylib(path, &cacheIndex) )
                        return sAllCacheImagesProxy;
        }
#endif
#if TARGET_OS_SIMULATOR
        // in simulators, 'path' has DYLD_ROOT_PATH prepended, but cache index does not have the prefix, so use orgPath
        const char* pathToFindInCache = orgPath;
#else
        const char* pathToFindInCache = path;
#endif
        uint statErrNo;
        struct stat statBuf;
        bool didStat = false;
        bool existsOnDisk;
        dyld3::SharedCacheFindDylibResults shareCacheResults;
        shareCacheResults.image = nullptr;
        if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, pathToFindInCache, &shareCacheResults) ) {
                // see if this image in the cache was already loaded via a different path
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); ++it) {
                        ImageLoader* anImage = *it;
                        if ( (const mach_header*)anImage->machHeader() == shareCacheResults.mhInCache )
                                return anImage;
                }
                // if RTLD_NOLOAD, do nothing if not already loaded
                if ( context.dontLoad ) {
                        // <rdar://33412890> possible that there is an override of cache
                        if ( my_stat(path, &statBuf) == 0 ) {
                                ImageLoader* imageLoader = findLoadedImage(statBuf);
                                if ( imageLoader != NULL )
                                        return imageLoader;
                        }
                        return NULL;
                }
                bool useCache = false;
                if ( shareCacheResults.image == nullptr ) {
                        // HACK to support old caches
                        existsOnDisk = ( my_stat(path, &statBuf) == 0 );
                        didStat = true;
                        statErrNo = errno;
                        useCache = !existsOnDisk;
                }
                else {
                        // <rdar://problem/7014995> zero out stat buffer so mtime, etc are zero for items from the shared cache
                        bzero(&statBuf, sizeof(statBuf));
                        if ( shareCacheResults.image->overridableDylib() ) {
                                existsOnDisk = ( my_stat(path, &statBuf) == 0 );
                                didStat = true;
                                statErrNo = errno;
                                if ( sSharedCacheLoadInfo.loadAddress->header.dylibsExpectedOnDisk ) {
                                        uint64_t expectedINode;
                                        uint64_t expectedMtime;
                                        if ( shareCacheResults.image->hasFileModTimeAndInode(expectedINode, expectedMtime) ) {
                                                if ( (expectedMtime == statBuf.st_mtime) && (expectedINode == statBuf.st_ino) )
                                                        useCache = true;
                                        }
                                }
                                else {
                                        if ( !existsOnDisk )
                                                useCache = true;
                                }
                        }
                        else {
                                useCache = true;
                        }
                }
                if ( useCache ) {
#if __MAC_OS_X_VERSION_MIN_REQUIRED
                        if ( gLinkContext.iOSonMac ) {
                                const dyld3::MachOFile* mf = (dyld3::MachOFile*)shareCacheResults.mhInCache;
                                bool supportsiOSMac = mf->supportsPlatform(dyld3::Platform::iOSMac);
                                if ( !supportsiOSMac && iOSonMacDenied(path) ) {
                                        throw "mach-o, but not built for UIKitForMac";
                                }
                        }
#endif
                        ImageLoader* imageLoader = ImageLoaderMachO::instantiateFromCache((macho_header*)shareCacheResults.mhInCache, shareCacheResults.pathInCache, shareCacheResults.slideInCache, statBuf, gLinkContext);
                        return checkandAddImage(imageLoader, context);
                }
        }

        // not in cache or cache not usable
        if ( !didStat ) {
                existsOnDisk = ( my_stat(path, &statBuf) == 0 );
                statErrNo = errno;
        }
        if ( existsOnDisk ) {
                // in case image was renamed or found via symlinks, check for inode match
                ImageLoader* imageLoader = findLoadedImage(statBuf);
                if ( imageLoader != NULL )
                        return imageLoader;
                // do nothing if not already loaded and if RTLD_NOLOAD 
                if ( context.dontLoad )
                        return NULL;
                // try opening file
                imageLoader = loadPhase5open(path, context, statBuf, exceptions);
                if ( imageLoader != NULL ) {
                        if ( shareCacheResults.image != nullptr ) {
                                // if image was found in cache, but is overridden by a newer file on disk, record what the image overrides
                                imageLoader->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                        }
                        return imageLoader;
                }
        }

        // just return NULL if file not found, but record any other errors
        if ( (statErrNo != ENOENT) && (statErrNo != 0) ) {
                if ( (statErrNo == EPERM) && sandboxBlockedStat(path) )
                        exceptions->push_back(dyld::mkstringf("%s: file system sandbox blocked stat()", path));
                else
                        exceptions->push_back(dyld::mkstringf("%s: stat() failed with errno=%d", path, statErrNo));
        }
        return NULL;
}

// look for path match with existing loaded images
static ImageLoader* loadPhase5check(const char* path, const char* orgPath, const LoadContext& context)
{
        //dyld::log("%s(%s, %s)\n", __func__ , path, orgPath);
        // search path against load-path and install-path of all already loaded images
        uint32_t hash = ImageLoader::hash(path);
        //dyld::log("check() hash=%d, path=%s\n", hash, path);
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* anImage = *it;
                // check hash first to cut down on strcmp calls
                //dyld::log("    check() hash=%d, path=%s\n", anImage->getPathHash(), anImage->getPath());
                if ( anImage->getPathHash() == hash ) {
                        if ( strcmp(path, anImage->getPath()) == 0 ) {
                                // if we are looking for a dylib don't return something else
                                if ( !context.mustBeDylib || anImage->isDylib() )
                                        return anImage;
                        }
                }
                if ( context.matchByInstallName || anImage->matchInstallPath() ) {
                        const char* installPath = anImage->getInstallPath();
                        if ( installPath != NULL) {
                                if ( strcmp(path, installPath) == 0 ) {
                                        // if we are looking for a dylib don't return something else
                                        if ( !context.mustBeDylib || anImage->isDylib() )
                                                return anImage;
                                }
                        }
                }
                // an install name starting with @rpath should match by install name, not just real path
                if ( (orgPath[0] == '@') && (strncmp(orgPath, "@rpath/", 7) == 0) ) {
                        const char* installPath = anImage->getInstallPath();
                        if ( installPath != NULL) {
                                if ( !context.mustBeDylib || anImage->isDylib() ) {
                                        if ( strcmp(orgPath, installPath) == 0 )
                                                return anImage;
                                }
                        }
                }
        }
        
        //dyld::log("%s(%s) => NULL\n", __func__,   path);
        return NULL;
}


// open or check existing
static ImageLoader* loadPhase5(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        
        // check for specific dylib overrides
        for (std::vector<DylibOverride>::iterator it = sDylibOverrides.begin(); it != sDylibOverrides.end(); ++it) {
                if ( strcmp(it->installName, path) == 0 ) {
                        path = it->override;
                        break;
                }
        }
        
        if ( exceptions != NULL ) 
                return loadPhase5load(path, orgPath, context, cacheIndex, exceptions);
        else
                return loadPhase5check(path, orgPath, context);
}

// try with and without image suffix
static ImageLoader* loadPhase4(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        ImageLoader* image = NULL;
        if ( gLinkContext.imageSuffix != NULL ) {
                for (const char* const* suffix=gLinkContext.imageSuffix; *suffix != NULL; ++suffix) {
                        char pathWithSuffix[strlen(path)+strlen(*suffix)+2];
                        ImageLoader::addSuffix(path, *suffix, pathWithSuffix);
                        image = loadPhase5(pathWithSuffix, orgPath, context, cacheIndex, exceptions);
                        if ( image != NULL )
                                break;
                }
                if ( image != NULL ) {
                        // if original path is in the dyld cache, then mark this one found as an override
                        dyld3::SharedCacheFindDylibResults shareCacheResults;
                        if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &shareCacheResults) && (shareCacheResults.image != nullptr) )
                                image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                }
        }
        if ( image == NULL )
                image = loadPhase5(path, orgPath, context, cacheIndex, exceptions);
        return image;
}

static ImageLoader* loadPhase2(const char* path, const char* orgPath, const LoadContext& context,
                                                           const char* const frameworkPaths[], const char* const libraryPaths[],
                                                           unsigned& cacheIndex, std::vector<const char*>* exceptions); // forward reference


// expand @ variables
static ImageLoader* loadPhase3(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        ImageLoader* image = NULL;
        if ( strncmp(path, "@executable_path/", 17) == 0 ) {
                // executable_path cannot be in used in any binary in a setuid process rdar://problem/4589305
                if ( !gLinkContext.allowAtPaths )
                        throwf("unsafe use of @executable_path in %s with restricted binary (Codesign main executable with Library Validation to allow @ paths)", context.origin);
                // handle @executable_path path prefix
                const char* executablePath = sExecPath;
                char newPath[strlen(executablePath) + strlen(path)];
                strcpy(newPath, executablePath);
                char* addPoint = strrchr(newPath,'/');
                if ( addPoint != NULL )
                        strcpy(&addPoint[1], &path[17]);
                else
                        strcpy(newPath, &path[17]);
                image = loadPhase4(newPath, orgPath, context, cacheIndex, exceptions);
                if ( image != NULL )
                        return image;

                // perhaps main executable path is a sym link, find realpath and retry
                char resolvedPath[PATH_MAX];
                if ( realpath(sExecPath, resolvedPath) != NULL ) {
                        char newRealPath[strlen(resolvedPath) + strlen(path)];
                        strcpy(newRealPath, resolvedPath);
                        addPoint = strrchr(newRealPath,'/');
                        if ( addPoint != NULL )
                                strcpy(&addPoint[1], &path[17]);
                        else
                                strcpy(newRealPath, &path[17]);
                        image = loadPhase4(newRealPath, orgPath, context, cacheIndex, exceptions);
                        if ( image != NULL )
                                return image;
                }
        }
        else if ( (strncmp(path, "@loader_path/", 13) == 0) && (context.origin != NULL) ) {
                // @loader_path cannot be used from the main executable of a setuid process rdar://problem/4589305
                if ( !gLinkContext.allowAtPaths  && (strcmp(context.origin, sExecPath) == 0) )
                        throwf("unsafe use of @loader_path in %s with restricted binary (Codesign main executable with Library Validation to allow @ paths)", context.origin);
                // handle @loader_path path prefix
                char newPath[strlen(context.origin) + strlen(path)];
                strcpy(newPath, context.origin);
                char* addPoint = strrchr(newPath,'/');
                if ( addPoint != NULL )
                        strcpy(&addPoint[1], &path[13]);
                else
                        strcpy(newPath, &path[13]);
                image = loadPhase4(newPath, orgPath, context, cacheIndex, exceptions);
                if ( image != NULL )
                        return image;
                
                // perhaps loader path is a sym link, find realpath and retry
                char resolvedPath[PATH_MAX];
                if ( realpath(context.origin, resolvedPath) != NULL ) {
                        char newRealPath[strlen(resolvedPath) + strlen(path)];
                        strcpy(newRealPath, resolvedPath);
                        addPoint = strrchr(newRealPath,'/');
                        if ( addPoint != NULL )
                                strcpy(&addPoint[1], &path[13]);
                        else
                                strcpy(newRealPath, &path[13]);
                        image = loadPhase4(newRealPath, orgPath, context, cacheIndex, exceptions);
                        if ( image != NULL )
                                return image;
                }
        }
        else if ( context.implicitRPath || (strncmp(path, "@rpath/", 7) == 0) ) {
                const char* trailingPath = (strncmp(path, "@rpath/", 7) == 0) ? &path[7] : path;
                // substitute @rpath with all -rpath paths up the load chain
                for(const ImageLoader::RPathChain* rp=context.rpath; rp != NULL; rp=rp->next) {
                        if (rp->paths != NULL ) {
                                for(std::vector<const char*>::iterator it=rp->paths->begin(); it != rp->paths->end(); ++it) {
                                        const char* anRPath = *it;
                                        char newPath[strlen(anRPath) + strlen(trailingPath)+2];
                                        strcpy(newPath, anRPath);
                                        if ( newPath[strlen(newPath)-1] != '/' )
                                                strcat(newPath, "/");
                                        strcat(newPath, trailingPath); 
                                        image = loadPhase4(newPath, orgPath, context, cacheIndex, exceptions);
                                        if ( gLinkContext.verboseRPaths && (exceptions != NULL) ) {
                                                if ( image != NULL ) 
                                                        dyld::log("RPATH successful expansion of %s to: %s\n", orgPath, newPath);
                                                else
                                                        dyld::log("RPATH failed expanding     %s to: %s\n", orgPath, newPath);
                                        }
                                        if ( image != NULL ) 
                                                return image;
                                }
                        }
                }
                
                // substitute @rpath with LD_LIBRARY_PATH
                if ( sEnv.LD_LIBRARY_PATH != NULL ) {
                        image = loadPhase2(trailingPath, orgPath, context, NULL, sEnv.LD_LIBRARY_PATH, cacheIndex, exceptions);
                        if ( image != NULL )
                                return image;
                }
                
                // if this is the "open" pass, don't try to open @rpath/... as a relative path
                if ( (exceptions != NULL) && (trailingPath != path) )
                        return NULL;
        }
        else if ( !gLinkContext.allowEnvVarsPath && (path[0] != '/' ) ) {
                throwf("unsafe use of relative rpath %s in %s with restricted binary", path, context.origin);
        }

        return loadPhase4(path, orgPath, context, cacheIndex, exceptions);
}

static ImageLoader* loadPhase2cache(const char* path, const char *orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions) {
        ImageLoader* image = NULL;
#if !TARGET_OS_SIMULATOR
        if ( (exceptions != NULL) && (gLinkContext.allowEnvVarsPath || !isFileRelativePath(path)) && (path[0] != '@') ) {
                char resolvedPath[PATH_MAX];
                realpath(path, resolvedPath);
                int myerr = errno;
                // If realpath() resolves to a path which does not exist on disk, errno is set to ENOENT
                if ( (myerr == ENOENT) || (myerr == 0) )
                {
                        image = loadPhase4(resolvedPath, orgPath, context, cacheIndex, exceptions);
                }
        }
#endif
        return image;
}


// try search paths
static ImageLoader* loadPhase2(const char* path, const char* orgPath, const LoadContext& context,
                                                           const char* const frameworkPaths[], const char* const libraryPaths[], 
                                                           unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        ImageLoader* image = NULL;
        const char* frameworkPartialPath = getFrameworkPartialPath(path);
        if ( frameworkPaths != NULL ) {
                if ( frameworkPartialPath != NULL ) {
                        const size_t frameworkPartialPathLen = strlen(frameworkPartialPath);
                        for(const char* const* fp = frameworkPaths; *fp != NULL; ++fp) {
                                char npath[strlen(*fp)+frameworkPartialPathLen+8];
                                strcpy(npath, *fp);
                                strcat(npath, "/");
                                strcat(npath, frameworkPartialPath);
                                //dyld::log("dyld: fallback framework path used: %s() -> loadPhase4(\"%s\", ...)\n", __func__, npath);
                                image = loadPhase4(npath, orgPath, context, cacheIndex, exceptions);
                                // Look in the cache if appropriate
                                if ( image == NULL)
                                        image = loadPhase2cache(npath, orgPath, context, cacheIndex, exceptions);
                                if ( image != NULL ) {
                                        // if original path is in the dyld cache, then mark this one found as an override
                                        dyld3::SharedCacheFindDylibResults shareCacheResults;
                                        if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &shareCacheResults) && (shareCacheResults.image != nullptr) )
                                                image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                                        return image;
                                }
                        }
                }
        }
        // <rdar://problem/12649639> An executable with the same name as a framework & DYLD_LIBRARY_PATH pointing to it gets loaded twice
        // <rdar://problem/14160846> Some apps depend on frameworks being found via library paths
        if ( (libraryPaths != NULL) && ((frameworkPartialPath == NULL) || sFrameworksFoundAsDylibs) ) {
                const char* libraryLeafName = getLibraryLeafName(path);
                const size_t libraryLeafNameLen = strlen(libraryLeafName);
                for(const char* const* lp = libraryPaths; *lp != NULL; ++lp) {
                        char libpath[strlen(*lp)+libraryLeafNameLen+8];
                        strcpy(libpath, *lp);
                        strcat(libpath, "/");
                        strcat(libpath, libraryLeafName);
                        //dyld::log("dyld: fallback library path used: %s() -> loadPhase4(\"%s\", ...)\n", __func__, libpath);
                        image = loadPhase4(libpath, orgPath, context, cacheIndex, exceptions);
                        // Look in the cache if appropriate
                        if ( image == NULL)
                                image = loadPhase2cache(libpath, orgPath, context, cacheIndex, exceptions);
                        if ( image != NULL ) {
                                // if original path is in the dyld cache, then mark this one found as an override
                                dyld3::SharedCacheFindDylibResults shareCacheResults;
                                if ( dyld3::findInSharedCacheImage(sSharedCacheLoadInfo, path, &shareCacheResults) && (shareCacheResults.image != nullptr) )
                                        image->setOverridesCachedDylib(shareCacheResults.image->imageNum());
                                return image;
                        }
                }
        }
        return NULL;
}

// try search overrides and fallbacks
static ImageLoader* loadPhase1(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        ImageLoader* image = NULL;

        bool pathIsInDyldCacheWhichCannotBeOverridden = false;
        if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
                pathIsInDyldCacheWhichCannotBeOverridden = sSharedCacheLoadInfo.loadAddress->hasNonOverridablePath(path);
        }

        // <rdar://problem/48490116> dyld customer cache cannot be overridden
        if ( !pathIsInDyldCacheWhichCannotBeOverridden ) {
                // handle LD_LIBRARY_PATH environment variables that force searching
                if ( context.useLdLibraryPath && (sEnv.LD_LIBRARY_PATH != NULL) ) {
                        image = loadPhase2(path, orgPath, context,  NULL, sEnv.LD_LIBRARY_PATH, cacheIndex,exceptions);
                        if ( image != NULL )
                                return image;
                }

                // handle DYLD_ environment variables that force searching
                if ( context.useSearchPaths && ((sEnv.DYLD_FRAMEWORK_PATH != NULL) || (sEnv.DYLD_LIBRARY_PATH != NULL)) ) {
                        image = loadPhase2(path, orgPath, context, sEnv.DYLD_FRAMEWORK_PATH, sEnv.DYLD_LIBRARY_PATH, cacheIndex, exceptions);
                        if ( image != NULL )
                                return image;
                }
        }

        // try raw path
        image = loadPhase3(path, orgPath, context, cacheIndex, exceptions);
        if ( image != NULL )
                return image;
        
        // try fallback paths during second time (will open file)
        const char* const* fallbackLibraryPaths = sEnv.DYLD_FALLBACK_LIBRARY_PATH;
        if ( (fallbackLibraryPaths != NULL) && !context.useFallbackPaths )
                fallbackLibraryPaths = NULL;
        if ( !context.dontLoad  && (exceptions != NULL) && ((sEnv.DYLD_FALLBACK_FRAMEWORK_PATH != NULL) || (fallbackLibraryPaths != NULL)) ) {
                image = loadPhase2(path, orgPath, context, sEnv.DYLD_FALLBACK_FRAMEWORK_PATH, fallbackLibraryPaths, cacheIndex, exceptions);
                if ( image != NULL )
                        return image;
        }

        // <rdar://problem/47682983> if hardened app calls dlopen() with a leaf path, dyld should only look in /usr/lib
        if ( context.useLdLibraryPath && (fallbackLibraryPaths == NULL) ) {
                const char* stdPaths[2] = { "/usr/lib", NULL };
                image = loadPhase2(path, orgPath, context, NULL, stdPaths, cacheIndex, exceptions);
                if ( image != NULL )
                        return image;
        }

        return NULL;
}

// try root substitutions
static ImageLoader* loadPhase0(const char* path, const char* orgPath, const LoadContext& context, unsigned& cacheIndex, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);

#if __MAC_OS_X_VERSION_MIN_REQUIRED
        // handle macOS dylibs dlopen()ing versioned path which needs to map to flat path in mazipan simulator
        if ( gLinkContext.iOSonMac && strstr(path, ".framework/Versions/")) {
                uintptr_t sourceOffset = 0;
                uintptr_t destOffset = 0;
                size_t sourceLangth = strlen(path);
                char flatPath[sourceLangth];
                flatPath[0] = 0;
                const char* frameworkBase = NULL;
                while ((frameworkBase = strstr(&path[sourceOffset], ".framework/Versions/"))) {
                        uintptr_t foundLength = (frameworkBase - &path[sourceOffset]) + strlen(".framework/") ;
                        strlcat(&flatPath[destOffset], &path[sourceOffset], foundLength);
                        sourceOffset += foundLength + strlen("Versions/") + 1;
                        destOffset += foundLength - 1;
                }
                strlcat(&flatPath[destOffset], &path[sourceOffset], sourceLangth);
                ImageLoader* image = loadPhase0(flatPath, orgPath, context, cacheIndex, exceptions);
                if ( image != NULL )
                        return image;
        }
#endif
        
#if SUPPORT_ROOT_PATH
        // handle DYLD_ROOT_PATH which forces absolute paths to use a new root
        if ( (gLinkContext.rootPaths != NULL) && (path[0] == '/') ) {
                for(const char* const* rootPath = gLinkContext.rootPaths; *rootPath != NULL; ++rootPath) {
                        size_t rootLen = strlen(*rootPath);
                        if ( strncmp(path, *rootPath, rootLen) != 0 ) {
                                char newPath[rootLen + strlen(path)+2];
                                strcpy(newPath, *rootPath);
                                strcat(newPath, path);
                                ImageLoader* image = loadPhase1(newPath, orgPath, context, cacheIndex, exceptions);
                                if ( image != NULL )
                                        return image;
                        }
                }
        }
#endif

        // try raw path
        return loadPhase1(path, orgPath, context, cacheIndex, exceptions);
}

//
// Given all the DYLD_ environment variables, the general case for loading libraries
// is that any given path expands into a list of possible locations to load.  We
// also must take care to ensure two copies of the "same" library are never loaded.
//
// The algorithm used here is that there is a separate function for each "phase" of the
// path expansion.  Each phase function calls the next phase with each possible expansion
// of that phase.  The result is the last phase is called with all possible paths.  
//
// To catch duplicates the algorithm is run twice.  The first time, the last phase checks
// the path against all loaded images.  The second time, the last phase calls open() on 
// the path.  Either time, if an image is found, the phases all unwind without checking
// for other paths.
//
ImageLoader* load(const char* path, const LoadContext& context, unsigned& cacheIndex)
{
        CRSetCrashLogMessage2(path);
        const char* orgPath = path;
        cacheIndex = UINT32_MAX;
        
        //dyld::log("%s(%s)\n", __func__ , path);
        char realPath[PATH_MAX];
        // when DYLD_IMAGE_SUFFIX is in used, do a realpath(), otherwise a load of "Foo.framework/Foo" will not match
        if ( context.useSearchPaths && ( gLinkContext.imageSuffix != NULL && *gLinkContext.imageSuffix != NULL) ) {
                if ( realpath(path, realPath) != NULL )
                        path = realPath;
        }
        
        // try all path permutations and check against existing loaded images

        ImageLoader* image = loadPhase0(path, orgPath, context, cacheIndex, NULL);
        if ( image != NULL ) {
                CRSetCrashLogMessage2(NULL);
                return image;
        }

        // try all path permutations and try open() until first success
        std::vector<const char*> exceptions;
        image = loadPhase0(path, orgPath, context, cacheIndex, &exceptions);
#if !TARGET_OS_SIMULATOR
        // <rdar://problem/16704628> support symlinks on disk to a path in dyld shared cache
        if ( image == NULL)
                image = loadPhase2cache(path, orgPath, context, cacheIndex, &exceptions);
#endif
    CRSetCrashLogMessage2(NULL);
        if ( image != NULL ) {
                // <rdar://problem/6916014> leak in dyld during dlopen when using DYLD_ variables
                for (std::vector<const char*>::iterator it = exceptions.begin(); it != exceptions.end(); ++it) {
                        free((void*)(*it));
                }
                // if loaded image is not from cache, but original path is in cache
                // set gSharedCacheOverridden flag to disable some ObjC optimizations
                if ( !gSharedCacheOverridden && !image->inSharedCache() && image->isDylib() && dyld3::MachOFile::isSharedCacheEligiblePath(path) && inSharedCache(path) ) {
                        gSharedCacheOverridden = true;
                }
                return image;
        }
        else if ( exceptions.size() == 0 ) {
                if ( context.dontLoad ) {
                        return NULL;
                }
                else
                        throw "image not found";
        }
        else {
                const char* msgStart = "no suitable image found.  Did find:";
                const char* delim = "\n\t";
                size_t allsizes = strlen(msgStart)+8;
                for (size_t i=0; i < exceptions.size(); ++i) 
                        allsizes += (strlen(exceptions[i]) + strlen(delim));
                char* fullMsg = new char[allsizes];
                strcpy(fullMsg, msgStart);
                for (size_t i=0; i < exceptions.size(); ++i) {
                        strcat(fullMsg, delim);
                        strcat(fullMsg, exceptions[i]);
                        free((void*)exceptions[i]);
                }
                throw (const char*)fullMsg;
        }
}





static void mapSharedCache()
{
        dyld3::SharedCacheOptions opts;
        opts.cacheDirOverride   = sSharedCacheOverrideDir;
        opts.forcePrivate               = (gLinkContext.sharedRegionMode == ImageLoader::kUsePrivateSharedRegion);


#if __x86_64__ && !TARGET_OS_SIMULATOR
        opts.useHaswell                 = sHaswell;
#else
        opts.useHaswell                 = false;
#endif
        opts.verbose                    = gLinkContext.verboseMapping;
        loadDyldCache(opts, &sSharedCacheLoadInfo);

        // update global state
        if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
                gLinkContext.dyldCache                                                          = sSharedCacheLoadInfo.loadAddress;
                dyld::gProcessInfo->processDetachedFromSharedRegion = opts.forcePrivate;
                dyld::gProcessInfo->sharedCacheSlide                = sSharedCacheLoadInfo.slide;
                dyld::gProcessInfo->sharedCacheBaseAddress          = (unsigned long)sSharedCacheLoadInfo.loadAddress;
                sSharedCacheLoadInfo.loadAddress->getUUID(dyld::gProcessInfo->sharedCacheUUID);
                dyld3::kdebug_trace_dyld_image(DBG_DYLD_UUID_SHARED_CACHE_A, sSharedCacheLoadInfo.path, (const uuid_t *)&dyld::gProcessInfo->sharedCacheUUID[0], {0,0}, {{ 0, 0 }}, (const mach_header *)sSharedCacheLoadInfo.loadAddress);
        }

//#if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
// RAM disk booting does not have shared cache yet
// Don't make lack of a shared cache fatal in that case
//      if ( sSharedCacheLoadInfo.loadAddress == nullptr ) {
//              if ( sSharedCacheLoadInfo.errorMessage != nullptr )
//                      halt(sSharedCacheLoadInfo.errorMessage);
//              else
//                      halt("error loading dyld shared cache");
//      }
//#endif
}



// create when NSLinkModule is called for a second time on a bundle
ImageLoader* cloneImage(ImageLoader* image)
{
        // open file (automagically closed when this function exits)
        FileOpener file(image->getPath());
        
        struct stat stat_buf;
        if ( fstat(file.getFileDescriptor(), &stat_buf) == -1)
                throw "stat error";
        
        dyld::LoadContext context;
        context.useSearchPaths          = false;
        context.useFallbackPaths        = false;
        context.useLdLibraryPath        = false;
        context.implicitRPath           = false;
        context.matchByInstallName      = false;
        context.dontLoad                        = false;
        context.mustBeBundle            = true;
        context.mustBeDylib                     = false;
        context.canBePIE                        = false;
        context.origin                          = NULL;
        context.rpath                           = NULL;
        return loadPhase6(file.getFileDescriptor(), stat_buf, image->getPath(), context);
}


ImageLoader* loadFromMemory(const uint8_t* mem, uint64_t len, const char* moduleName)
{
        // if fat wrapper, find usable sub-file
        const fat_header* memStartAsFat = (fat_header*)mem;
        uint64_t fileOffset = 0;
        uint64_t fileLength = len;
        if ( memStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
                if ( fatFindBest(memStartAsFat, &fileOffset, &fileLength) ) {
                        mem = &mem[fileOffset];
                        len = fileLength;
                }
                else {
                        throw "no matching architecture in universal wrapper";
                }
        }

        // try each loader
        if ( isCompatibleMachO(mem, moduleName) ) {
                ImageLoader* image = ImageLoaderMachO::instantiateFromMemory(moduleName, (macho_header*)mem, len, gLinkContext);
                // don't add bundles to global list, they can be loaded but not linked.  When linked it will be added to list
                if ( ! image->isBundle() ) 
                        addImage(image);
                return image;
        }
        
        // try other file formats here...
        
        // throw error about what was found
        switch (*(uint32_t*)mem) {
                case MH_MAGIC:
                case MH_CIGAM:
                case MH_MAGIC_64:
                case MH_CIGAM_64:
                        throw "mach-o, but wrong architecture";
                default:
                throwf("unknown file type, first eight bytes: 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X", 
                        mem[0], mem[1], mem[2], mem[3], mem[4], mem[5], mem[6],mem[7]);
        }
}


void registerAddCallback(ImageCallback func)
{
        // now add to list to get notified when any more images are added
        sAddImageCallbacks.push_back(func);
        
        // call callback with all existing images
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* image = *it;
                if ( image->getState() >= dyld_image_state_bound && image->getState() < dyld_image_state_terminated ) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*func), 0);
                        (*func)(image->machHeader(), image->getSlide());
                }
        }
#if SUPPORT_ACCELERATE_TABLES
        if ( sAllCacheImagesProxy != NULL ) {
                dyld_image_info infos[allImagesCount()+1];
                unsigned cacheCount = sAllCacheImagesProxy->appendImagesToNotify(dyld_image_state_bound, true, infos);
                for (unsigned i=0; i < cacheCount; ++i) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[i].imageLoadAddress, (uint64_t)(*func), 0);
                        (*func)(infos[i].imageLoadAddress, sSharedCacheLoadInfo.slide);
                }
        }
#endif
}

void registerLoadCallback(LoadImageCallback func)
{
        // now add to list to get notified when any more images are added
        sAddLoadImageCallbacks.push_back(func);

        // call callback with all existing images
        for (ImageLoader* image : sAllImages) {
                if ( image->getState() >= dyld_image_state_bound && image->getState() < dyld_image_state_terminated ) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)image->machHeader(), (uint64_t)(*func), 0);
                        (*func)(image->machHeader(), image->getPath(), !image->neverUnload());
                }
        }
#if SUPPORT_ACCELERATE_TABLES
        if ( sAllCacheImagesProxy != NULL ) {
                dyld_image_info infos[allImagesCount()+1];
                unsigned cacheCount = sAllCacheImagesProxy->appendImagesToNotify(dyld_image_state_bound, true, infos);
                for (unsigned i=0; i < cacheCount; ++i) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)infos[i].imageLoadAddress, (uint64_t)(*func), 0);
                        (*func)(infos[i].imageLoadAddress, infos[i].imageFilePath, false);
                }
        }
#endif
}

void registerBulkLoadCallback(LoadImageBulkCallback func)
{
        // call callback with all existing images
        unsigned count = dyld::gProcessInfo->infoArrayCount;
        const dyld_image_info* infoArray = dyld::gProcessInfo->infoArray;
        if ( infoArray != NULL ) {
                const mach_header* mhs[count];
                const char*        paths[count];
                for (unsigned i=0; i < count; ++i) {
                        mhs[i]   = infoArray[i].imageLoadAddress;
                        paths[i] = infoArray[i].imageFilePath;
                }
                dyld3::ScopedTimer timer(DBG_DYLD_TIMING_FUNC_FOR_ADD_IMAGE, (uint64_t)mhs[0], (uint64_t)func, 0);
                func(count, mhs, paths);
        }

        // now add to list to get notified when any more images are added
        sAddBulkLoadImageCallbacks.push_back(func);
}

void registerRemoveCallback(ImageCallback func)
{
        // <rdar://problem/15025198> ignore calls to register a notification during a notification
        if ( sRemoveImageCallbacksInUse )
                return;
        sRemoveImageCallbacks.push_back(func);
}

void clearErrorMessage()
{
        error_string[0] = '\0';
}

void setErrorMessage(const char* message)
{
        // save off error message in global buffer for CrashReporter to find
        strlcpy(error_string, message, sizeof(error_string));
}

const char* getErrorMessage()
{
        return error_string;
}

void halt(const char* message)
{
        if ( sSharedCacheLoadInfo.errorMessage != nullptr ) {
                // <rdar://problem/45957449> if dyld fails with a missing dylib and there is no shared cache, display the shared cache load error message
                dyld::log("dyld: dyld cache load error: %s\n", sSharedCacheLoadInfo.errorMessage);
                dyld::log("dyld: %s\n", message);
                strlcpy(error_string, "dyld cache load error: ", sizeof(error_string));
                strlcat(error_string, sSharedCacheLoadInfo.errorMessage, sizeof(error_string));
                strlcat(error_string, "\n", sizeof(error_string));
                strlcat(error_string, message, sizeof(error_string));
        }
        else {
                dyld::log("dyld: %s\n", message);
                strlcpy(error_string, message, sizeof(error_string));
        }

        dyld::gProcessInfo->errorMessage = error_string;
        if ( !gLinkContext.startedInitializingMainExecutable )
                dyld::gProcessInfo->terminationFlags = 1;
        else
                dyld::gProcessInfo->terminationFlags = 0;

        char payloadBuffer[EXIT_REASON_PAYLOAD_MAX_LEN];
        dyld_abort_payload* payload = (dyld_abort_payload*)payloadBuffer;
        payload->version               = 1;
        payload->flags                 = gLinkContext.startedInitializingMainExecutable ? 0 : 1;
        payload->targetDylibPathOffset = 0;
        payload->clientPathOffset      = 0;
        payload->symbolOffset          = 0;
        int payloadSize = sizeof(dyld_abort_payload);

        if ( dyld::gProcessInfo->errorTargetDylibPath != NULL ) {
                payload->targetDylibPathOffset = payloadSize;
                payloadSize += strlcpy(&payloadBuffer[payloadSize], dyld::gProcessInfo->errorTargetDylibPath, sizeof(payloadBuffer)-payloadSize) + 1;
        }
        if ( dyld::gProcessInfo->errorClientOfDylibPath != NULL ) {
                payload->clientPathOffset = payloadSize;
                payloadSize += strlcpy(&payloadBuffer[payloadSize], dyld::gProcessInfo->errorClientOfDylibPath, sizeof(payloadBuffer)-payloadSize) + 1;
        }
        if ( dyld::gProcessInfo->errorSymbol != NULL ) {
                payload->symbolOffset = payloadSize;
                payloadSize += strlcpy(&payloadBuffer[payloadSize], dyld::gProcessInfo->errorSymbol, sizeof(payloadBuffer)-payloadSize) + 1;
        }
        char truncMessage[EXIT_REASON_USER_DESC_MAX_LEN];
        strlcpy(truncMessage, error_string, EXIT_REASON_USER_DESC_MAX_LEN);
        abort_with_payload(OS_REASON_DYLD, dyld::gProcessInfo->errorKind ? dyld::gProcessInfo->errorKind : DYLD_EXIT_REASON_OTHER, payloadBuffer, payloadSize, truncMessage, 0);
}

static void setErrorStrings(unsigned errorCode, const char* errorClientOfDylibPath,
                                                                const char* errorTargetDylibPath, const char* errorSymbol)
{
        dyld::gProcessInfo->errorKind = errorCode;
        dyld::gProcessInfo->errorClientOfDylibPath = errorClientOfDylibPath;
        dyld::gProcessInfo->errorTargetDylibPath = errorTargetDylibPath;
        dyld::gProcessInfo->errorSymbol = errorSymbol;
}


uintptr_t bindLazySymbol(const mach_header* mh, uintptr_t* lazyPointer)
{
        uintptr_t result = 0;
        // acquire read-lock on dyld's data structures
#if 0 // rdar://problem/3811777 turn off locking until deadlock is resolved
        if ( gLibSystemHelpers != NULL ) 
                (*gLibSystemHelpers->lockForReading)();
#endif
        // lookup and bind lazy pointer and get target address
        try {
                ImageLoader* target;
        #if __i386__
                // fast stubs pass NULL for mh and image is instead found via the location of stub (aka lazyPointer)
                if ( mh == NULL )
                        target = dyld::findImageContainingAddress(lazyPointer);
                else
                        target = dyld::findImageByMachHeader(mh);
        #else
                // note, target should always be mach-o, because only mach-o lazy handler wired up to this
                target = dyld::findImageByMachHeader(mh);
        #endif
                if ( target == NULL )
                        throwf("image not found for lazy pointer at %p", lazyPointer);
                result = target->doBindLazySymbol(lazyPointer, gLinkContext);
        }
        catch (const char* message) {
                dyld::log("dyld: lazy symbol binding failed: %s\n", message);
                halt(message);
        }
        // release read-lock on dyld's data structures
#if 0
        if ( gLibSystemHelpers != NULL ) 
                (*gLibSystemHelpers->unlockForReading)();
#endif
        // return target address to glue which jumps to it with real parameters restored
        return result;
}


uintptr_t fastBindLazySymbol(ImageLoader** imageLoaderCache, uintptr_t lazyBindingInfoOffset)
{
        uintptr_t result = 0;
        // get image 
        if ( *imageLoaderCache == NULL ) {
                // save in cache
                *imageLoaderCache = dyld::findMappedRange((uintptr_t)imageLoaderCache);
                if ( *imageLoaderCache == NULL ) {
#if SUPPORT_ACCELERATE_TABLES
                if ( sAllCacheImagesProxy != NULL ) {
                        const mach_header* mh;
                        const char* path;
                        unsigned index;
                        if ( sAllCacheImagesProxy->addressInCache(imageLoaderCache, &mh, &path, &index) ) {
                                result = sAllCacheImagesProxy->bindLazy(lazyBindingInfoOffset, gLinkContext, mh, index);
                                if ( result == 0 ) {
                                        halt("dyld: lazy symbol binding failed for image in dyld shared\n");
                                }
                                return result;
                        }
                }
#endif
                        const char* message = "fast lazy binding from unknown image";
                        dyld::log("dyld: %s\n", message);
                        halt(message);
                }
        }
        
        // bind lazy pointer and return it
        try {
                result = (*imageLoaderCache)->doBindFastLazySymbol((uint32_t)lazyBindingInfoOffset, gLinkContext, 
                                                                (dyld::gLibSystemHelpers != NULL) ? dyld::gLibSystemHelpers->acquireGlobalDyldLock : NULL,
                                                                (dyld::gLibSystemHelpers != NULL) ? dyld::gLibSystemHelpers->releaseGlobalDyldLock : NULL);
        }
        catch (const char* message) {
                dyld::log("dyld: lazy symbol binding failed: %s\n", message);
                halt(message);
        }

        // return target address to glue which jumps to it with real parameters restored
        return result;
}



void registerUndefinedHandler(UndefinedHandler handler)
{
        sUndefinedHandler = handler;
}

static void undefinedHandler(const char* symboName)
{
        if ( sUndefinedHandler != NULL ) {
                (*sUndefinedHandler)(symboName);
        }
}

static bool findExportedSymbol(const char* name, bool onlyInCoalesced, const ImageLoader::Symbol** sym, const ImageLoader** image, ImageLoader::CoalesceNotifier notifier=NULL)
{
        // search all images in order
        const ImageLoader* firstWeakImage = NULL;
        const ImageLoader::Symbol* firstWeakSym = NULL;
        const ImageLoader* firstNonWeakImage = NULL;
        const ImageLoader::Symbol* firstNonWeakSym = NULL;
        const size_t imageCount = sAllImages.size();
        for(size_t i=0; i < imageCount; ++i) {
                ImageLoader* anImage = sAllImages[i];
                // the use of inserted libraries alters search order
                // so that inserted libraries are found before the main executable
                if ( sInsertedDylibCount > 0 ) {
                        if ( i < sInsertedDylibCount )
                                anImage = sAllImages[i+1];
                        else if ( i == sInsertedDylibCount )
                                anImage = sAllImages[0];
                }
                //dyld::log("findExportedSymbol(%s) looking at %s\n", name, anImage->getPath());
                if ( ! anImage->hasHiddenExports() && (!onlyInCoalesced || anImage->hasCoalescedExports()) ) {
                        const ImageLoader* foundInImage;
                        *sym = anImage->findExportedSymbol(name, false, &foundInImage);
                        //dyld::log("findExportedSymbol(%s) found: sym=%p, anImage=%p, foundInImage=%p\n", name, *sym, anImage, foundInImage /*, (foundInImage ? foundInImage->getPath() : "")*/);
                        if ( *sym != NULL ) {
                                if ( notifier && (foundInImage == anImage) )
                                        notifier(*sym, foundInImage, foundInImage->machHeader());
                                // if weak definition found, record first one found
                                if ( (foundInImage->getExportedSymbolInfo(*sym) & ImageLoader::kWeakDefinition) != 0 ) {
                                        if ( firstWeakImage == NULL ) {
                                                firstWeakImage = foundInImage;
                                                firstWeakSym = *sym;
                                        }
                                }
                                else {
                                        // found non-weak
                                        if ( !onlyInCoalesced ) {
                                                // for flat lookups, return first found
                                                *image = foundInImage;
                                                return true;
                                        }
                                        if ( firstNonWeakImage == NULL ) {
                                                firstNonWeakImage = foundInImage;
                                                firstNonWeakSym = *sym;
                                        }
                                }
                        }
                }
        }
        if ( firstNonWeakImage != NULL ) {
                // found a weak definition, but no non-weak, so return first weak found
                *sym = firstNonWeakSym;
                *image = firstNonWeakImage;
                return true;
        }
        if ( firstWeakSym != NULL ) {
                // found a weak definition, but no non-weak, so return first weak found
                *sym = firstWeakSym;
                *image = firstWeakImage;
                return true;
        }
#if SUPPORT_ACCELERATE_TABLES
        if ( sAllCacheImagesProxy != NULL ) {
                if ( sAllCacheImagesProxy->flatFindSymbol(name, onlyInCoalesced, sym, image, notifier) )
                        return true;
        }
#endif

        return false;
}

bool flatFindExportedSymbol(const char* name, const ImageLoader::Symbol** sym, const ImageLoader** image)
{
        return findExportedSymbol(name, false, sym, image);
}

bool findCoalescedExportedSymbol(const char* name, const ImageLoader::Symbol** sym, const ImageLoader** image, ImageLoader::CoalesceNotifier notifier)
{
        return findExportedSymbol(name, true, sym, image, notifier);
}


bool flatFindExportedSymbolWithHint(const char* name, const char* librarySubstring, const ImageLoader::Symbol** sym, const ImageLoader** image)
{
        // search all images in order
        const size_t imageCount = sAllImages.size();
        for(size_t i=0; i < imageCount; ++i){
                ImageLoader* anImage = sAllImages[i];
                // only look at images whose paths contain the hint string (NULL hint string is wildcard)
                if ( ! anImage->isBundle() && ((librarySubstring==NULL) || (strstr(anImage->getPath(), librarySubstring) != NULL)) ) {
                        *sym = anImage->findExportedSymbol(name, false, image);
                        if ( *sym != NULL ) {
                                return true;
                        }
                }
        }
        return false;
}


unsigned int getCoalescedImages(ImageLoader* images[], unsigned imageIndex[])
{
        unsigned int count = 0;
        const size_t imageCount = sAllImages.size();
        for(size_t i=0; i < imageCount; ++i) {
                ImageLoader* anImage = sAllImages[i];
                // the use of inserted libraries alters search order
                // so that inserted libraries are found before the main executable
                if ( sInsertedDylibCount > 0 ) {
                        if ( i < sInsertedDylibCount )
                                anImage = sAllImages[i+1];
                        else if ( i == sInsertedDylibCount )
                                anImage = sAllImages[0];
                }
                if ( anImage->participatesInCoalescing() ) {
                        images[count] = anImage;
                        imageIndex[count] = 0;
                        ++count;
                }
        }
#if SUPPORT_ACCELERATE_TABLES
        if ( sAllCacheImagesProxy != NULL ) {
                sAllCacheImagesProxy->appendImagesNeedingCoalescing(images, imageIndex, count);
        }
#endif
        return count;
}


static ImageLoader::MappedRegion* getMappedRegions(ImageLoader::MappedRegion* regions)
{
        ImageLoader::MappedRegion* end = regions;
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                (*it)->getMappedRegions(end);
        }
        return end;
}

void registerImageStateSingleChangeHandler(dyld_image_states state, dyld_image_state_change_handler handler)
{
        // mark the image that the handler is in as never-unload because dyld has a reference into it
        ImageLoader* handlerImage = findImageContainingAddress((void*)handler);
        if ( handlerImage != NULL )
                handlerImage->setNeverUnload();

        // add to list of handlers
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sSingleHandlers);
        if ( handlers != NULL ) {
        // <rdar://problem/10332417> need updateAllImages() to be last in dyld_image_state_mapped list
        // so that if ObjC adds a handler that prevents a load, it happens before the gdb list is updated
        if ( state == dyld_image_state_mapped )
            handlers->insert(handlers->begin(), handler);
        else
            handlers->push_back(handler);

                // call callback with all existing images
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                        ImageLoader* image = *it;
                        dyld_image_info  info;
                        info.imageLoadAddress   = image->machHeader();
                        info.imageFilePath              = image->getRealPath();
                        info.imageFileModDate   = image->lastModified();
                        // should only call handler if state == image->state
                        if ( image->getState() == state )
                                (*handler)(state, 1, &info);
                        // ignore returned string, too late to do anything
                }
        }
}

void registerImageStateBatchChangeHandler(dyld_image_states state, dyld_image_state_change_handler handler)
{
        // mark the image that the handler is in as never-unload because dyld has a reference into it
        ImageLoader* handlerImage = findImageContainingAddress((void*)handler);
        if ( handlerImage != NULL )
                handlerImage->setNeverUnload();

        // add to list of handlers
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sBatchHandlers);
        if ( handlers != NULL ) {
                // insert at front, so that gdb handler is always last
                handlers->insert(handlers->begin(), handler);
                
                // call callback with all existing images
                try {
                        notifyBatchPartial(state, true, handler, false, false);
                }
                catch (const char* msg) {
                        // ignore request to abort during registration
                }
        }
}


void registerObjCNotifiers(_dyld_objc_notify_mapped mapped, _dyld_objc_notify_init init, _dyld_objc_notify_unmapped unmapped)
{
        // record functions to call
        sNotifyObjCMapped       = mapped;
        sNotifyObjCInit         = init;
        sNotifyObjCUnmapped = unmapped;

        // call 'mapped' function with all images mapped so far
        try {
                notifyBatchPartial(dyld_image_state_bound, true, NULL, false, true);
        }
        catch (const char* msg) {
                // ignore request to abort during registration
        }

        // <rdar://problem/32209809> call 'init' function on all images already init'ed (below libSystem)
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* image = *it;
                if ( (image->getState() == dyld_image_state_initialized) && image->notifyObjC() ) {
                        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_OBJC_INIT, (uint64_t)image->machHeader(), 0, 0);
                        (*sNotifyObjCInit)(image->getRealPath(), image->machHeader());
                }
        }
}

bool sharedCacheUUID(uuid_t uuid)
{
        if ( sSharedCacheLoadInfo.loadAddress == nullptr )
                return false;

        sSharedCacheLoadInfo.loadAddress->getUUID(uuid);
        return true;
}

#if SUPPORT_ACCELERATE_TABLES

bool dlopenFromCache(const char* path, int mode, void** handle)
{
        if ( sAllCacheImagesProxy == NULL )
                return false;
        char fallbackPath[PATH_MAX];
        bool result = sAllCacheImagesProxy->dlopenFromCache(gLinkContext, path, mode, handle);
        if ( !result && (strchr(path, '/') == NULL) ) {
                // POSIX says you can call dlopen() with a leaf name (e.g. dlopen("libz.dylb"))
                strcpy(fallbackPath, "/usr/lib/");
                strlcat(fallbackPath, path, PATH_MAX);
                result = sAllCacheImagesProxy->dlopenFromCache(gLinkContext, fallbackPath, mode, handle);
                if ( !result )
                        path = fallbackPath;
        }
        if ( !result ) {
                // leaf name could be a symlink
                char resolvedPath[PATH_MAX];
                realpath(path, resolvedPath);
                int realpathErrno = errno;
                // If realpath() resolves to a path which does not exist on disk, errno is set to ENOENT
                if ( (realpathErrno == ENOENT) || (realpathErrno == 0) ) {
                        result = sAllCacheImagesProxy->dlopenFromCache(gLinkContext, resolvedPath, mode, handle);
                }
        }

        return result;
}

bool makeCacheHandle(ImageLoader* image, unsigned cacheIndex, int mode, void** result)
{
        if ( sAllCacheImagesProxy == NULL )
                return false;
        return sAllCacheImagesProxy->makeCacheHandle(gLinkContext, cacheIndex, mode, result);
}

bool isCacheHandle(void* handle)
{
        if ( sAllCacheImagesProxy == NULL )
                return false;
        return sAllCacheImagesProxy->isCacheHandle(handle, NULL, NULL);
}

bool isPathInCache(const char* path)
{
        if ( sAllCacheImagesProxy == NULL )
                return false;
        unsigned index;
        return sAllCacheImagesProxy->hasDylib(path, &index);
}

const char* getPathFromIndex(unsigned cacheIndex)
{
        if ( sAllCacheImagesProxy == NULL )
                return NULL;
        return sAllCacheImagesProxy->getIndexedPath(cacheIndex);
}

void* dlsymFromCache(void* handle, const char* symName, unsigned index)
{
        if ( sAllCacheImagesProxy == NULL )
                return NULL;
        return sAllCacheImagesProxy->dlsymFromCache(gLinkContext, handle, symName, index);
}

bool addressInCache(const void* address, const mach_header** mh, const char** path, unsigned* index)
{
        if ( sAllCacheImagesProxy == NULL )
                return false;
        unsigned ignore;
        return sAllCacheImagesProxy->addressInCache(address, mh, path, index ? index : &ignore);
}

bool findUnwindSections(const void* addr, dyld_unwind_sections* info)
{
        if ( sAllCacheImagesProxy == NULL )
                return false;
        return sAllCacheImagesProxy->findUnwindSections(addr, info);
}

bool dladdrFromCache(const void* address, Dl_info* info)
{
        if ( sAllCacheImagesProxy == NULL )
                return false;
        return sAllCacheImagesProxy->dladdrFromCache(address, info);
}
#endif

static ImageLoader* libraryLocator(const char* libraryName, bool search, const char* origin, const ImageLoader::RPathChain* rpaths, unsigned& cacheIndex)
{
        dyld::LoadContext context;
        context.useSearchPaths          = search;
        context.useFallbackPaths        = search;
        context.useLdLibraryPath        = false;
        context.implicitRPath           = false;
        context.matchByInstallName      = false;
        context.dontLoad                        = false;
        context.mustBeBundle            = false;
        context.mustBeDylib                     = true;
        context.canBePIE                        = false;
        context.origin                          = origin;
        context.rpath                           = rpaths;
        return load(libraryName, context, cacheIndex);
}

static const char* basename(const char* path)
{
    const char* last = path;
    for (const char* s = path; *s != '\0'; s++) {
        if (*s == '/') 
                        last = s+1;
    }
    return last;
}

static void setContext(const macho_header* mainExecutableMH, int argc, const char* argv[], const char* envp[], const char* apple[])
{
        gLinkContext.loadLibrary                        = &libraryLocator;
        gLinkContext.terminationRecorder        = &terminationRecorder;
        gLinkContext.flatExportFinder           = &flatFindExportedSymbol;
        gLinkContext.coalescedExportFinder      = &findCoalescedExportedSymbol;
        gLinkContext.getCoalescedImages         = &getCoalescedImages;
        gLinkContext.undefinedHandler           = &undefinedHandler;
        gLinkContext.getAllMappedRegions        = &getMappedRegions;
        gLinkContext.bindingHandler                     = NULL;
        gLinkContext.notifySingle                       = &notifySingle;
        gLinkContext.notifyBatch                        = &notifyBatch;
        gLinkContext.removeImage                        = &removeImage;
        gLinkContext.registerDOFs                       = dyld3::Loader::dtraceUserProbesEnabled() ? &registerDOFs : NULL;
        gLinkContext.clearAllDepths                     = &clearAllDepths;
        gLinkContext.printAllDepths                     = &printAllDepths;
        gLinkContext.imageCount                         = &imageCount;
        gLinkContext.setNewProgramVars          = &setNewProgramVars;
        gLinkContext.inSharedCache                      = &inSharedCache;
        gLinkContext.setErrorStrings            = &setErrorStrings;
#if SUPPORT_OLD_CRT_INITIALIZATION
        gLinkContext.setRunInitialzersOldWay= &setRunInitialzersOldWay;
#endif
        gLinkContext.findImageContainingAddress = &findImageContainingAddress;
        gLinkContext.addDynamicReference        = &addDynamicReference;
#if SUPPORT_ACCELERATE_TABLES
        gLinkContext.notifySingleFromCache      = &notifySingleFromCache;
        gLinkContext.getPreInitNotifyHandler= &getPreInitNotifyHandler;
        gLinkContext.getBoundBatchHandler   = &getBoundBatchHandler;
#endif
        gLinkContext.bindingOptions                     = ImageLoader::kBindingNone;
        gLinkContext.argc                                       = argc;
        gLinkContext.argv                                       = argv;
        gLinkContext.envp                                       = envp;
        gLinkContext.apple                                      = apple;
        gLinkContext.progname                           = (argv[0] != NULL) ? basename(argv[0]) : "";
        gLinkContext.programVars.mh                     = mainExecutableMH;
        gLinkContext.programVars.NXArgcPtr      = &gLinkContext.argc;
        gLinkContext.programVars.NXArgvPtr      = &gLinkContext.argv;
        gLinkContext.programVars.environPtr     = &gLinkContext.envp;
        gLinkContext.programVars.__prognamePtr=&gLinkContext.progname;
        gLinkContext.mainExecutable                     = NULL;
        gLinkContext.imageSuffix                        = NULL;
        gLinkContext.dynamicInterposeArray      = NULL;
        gLinkContext.dynamicInterposeCount      = 0;
        gLinkContext.prebindUsage                       = ImageLoader::kUseAllPrebinding;
        gLinkContext.sharedRegionMode           = ImageLoader::kUseSharedRegion;
}



//
// Look for a special segment in the mach header. 
// Its presences means that the binary wants to have DYLD ignore
// DYLD_ environment variables.
//
#if __MAC_OS_X_VERSION_MIN_REQUIRED
static bool hasRestrictedSegment(const macho_header* mh)
{
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_SEGMENT_COMMAND:
                        {
                                const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                                
                                //dyld::log("seg name: %s\n", seg->segname);
                                if (strcmp(seg->segname, "__RESTRICT") == 0) {
                                        const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                                        const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
                                        for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                                                if (strcmp(sect->sectname, "__restrict") == 0) 
                                                        return true;
                                        }
                                }
                        }
                        break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
                
        return false;
}
#endif

#if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
static bool isFairPlayEncrypted(const macho_header* mh)
{
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                if ( cmd->cmd == LC_ENCRYPT_COMMAND ) {
                        const encryption_info_command* enc = (encryption_info_command*)cmd;
                        return (enc->cryptid != 0);
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }

        return false;
}
#endif

#if SUPPORT_VERSIONED_PATHS

static bool readFirstPage(const char* dylibPath, uint8_t firstPage[4096]) 
{
        firstPage[0] = 0;
        // open file (automagically closed when this function exits)
        FileOpener file(dylibPath);

        if ( file.getFileDescriptor() == -1 ) 
                return false;
        
        if ( pread(file.getFileDescriptor(), firstPage, 4096, 0) != 4096 )
                return false;

        // if fat wrapper, find usable sub-file
        const fat_header* fileStartAsFat = (fat_header*)firstPage;
        if ( fileStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
                uint64_t fileOffset;
                uint64_t fileLength;
                if ( fatFindBest(fileStartAsFat, &fileOffset, &fileLength) ) {
                        if ( pread(file.getFileDescriptor(), firstPage, 4096, fileOffset) != 4096 )
                                return false;
                }
                else {
                        return false;
                }
        }
        
        return true;
}

//
// Peeks at a dylib file and returns its current_version and install_name.
// Returns false on error.
//
static bool getDylibVersionAndInstallname(const char* dylibPath, uint32_t* version, char* installName)
{
        uint8_t firstPage[4096];
        const macho_header* mh = (macho_header*)firstPage;
        if ( !readFirstPage(dylibPath, firstPage) ) {
                // If file cannot be read, check to see if path is in shared cache
                const macho_header* mhInCache;
                const char*                     pathInCache;
                long                            slideInCache;
                if ( !findInSharedCacheImage(dylibPath, true, NULL, &mhInCache, &pathInCache, &slideInCache) )
                        return false;
                mh = mhInCache;
        }

        // check mach-o header
        if ( mh->magic != sMainExecutableMachHeader->magic ) 
                return false;
        if ( mh->cputype != sMainExecutableMachHeader->cputype )
                return false;

        // scan load commands for LC_ID_DYLIB
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
        const struct load_command* const cmdsReadEnd = (struct load_command*)(((char*)mh)+4096);
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_ID_DYLIB:
                        {
                                const struct dylib_command* id = (struct dylib_command*)cmd;
                                *version = id->dylib.current_version;
                                if ( installName != NULL )
                                        strlcpy(installName, (char *)id + id->dylib.name.offset, PATH_MAX);
                                return true;
                        }
                        break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                if ( cmd > cmdsReadEnd )
                        return false;
        }
        
        return false;
}
#endif // SUPPORT_VERSIONED_PATHS
                                                

#if 0
static void printAllImages()
{
        dyld::log("printAllImages()\n");
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* image = *it;
                dyld_image_states imageState = image->getState();
                dyld::log("  state=%d, dlopen-count=%d, never-unload=%d, in-use=%d, name=%s\n",
                                  imageState, image->dlopenCount(), image->neverUnload(), image->isMarkedInUse(), image->getShortName());
        }
}
#endif

void link(ImageLoader* image, bool forceLazysBound, bool neverUnload, const ImageLoader::RPathChain& loaderRPaths, unsigned cacheIndex)
{
        // add to list of known images.  This did not happen at creation time for bundles
        if ( image->isBundle() && !image->isLinked() )
                addImage(image);

        // we detect root images as those not linked in yet 
        if ( !image->isLinked() )
                addRootImage(image);
        
        // process images
        try {
                const char* path = image->getPath();
#if SUPPORT_ACCELERATE_TABLES
                if ( image == sAllCacheImagesProxy )
                        path = sAllCacheImagesProxy->getIndexedPath(cacheIndex);
#endif
                image->link(gLinkContext, forceLazysBound, false, neverUnload, loaderRPaths, path);
        }
        catch (const char* msg) {
                garbageCollectImages();
                throw;
        }
}


void runInitializers(ImageLoader* image)
{
        // do bottom up initialization
        ImageLoader::InitializerTimingList initializerTimes[allImagesCount()];
        initializerTimes[0].count = 0;
        image->runInitializers(gLinkContext, initializerTimes[0]);
}

// This function is called at the end of dlclose() when the reference count goes to zero.
// The dylib being unloaded may have brought in other dependent dylibs when it was loaded.
// Those dependent dylibs need to be unloaded, but only if they are not referenced by
// something else.  We use a standard mark and sweep garbage collection.
//
// The tricky part is that when a dylib is unloaded it may have a termination function that
// can run and itself call dlclose() on yet another dylib.  The problem is that this
// sort of gabage collection is not re-entrant.  Instead a terminator's call to dlclose()
// which calls garbageCollectImages() will just set a flag to re-do the garbage collection
// when the current pass is done.
//
// Also note that this is done within the dyld global lock, so it is always single threaded.
//
void garbageCollectImages()
{
        static bool sDoingGC = false;
        static bool sRedo = false;

        if ( sDoingGC ) {
                // GC is currently being run, just set a flag to have it run again.
                sRedo = true;
                return;
        }
        
        sDoingGC = true;
        do {
                sRedo = false;
                
                // mark phase: mark all images not-in-use
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                        ImageLoader* image = *it;
                        //dyld::log("gc: neverUnload=%d name=%s\n", image->neverUnload(), image->getShortName());
                        image->markNotUsed();
                }
                
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
                // sweep phase: mark as in-use, images reachable from never-unload or in-use image
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                        ImageLoader* image = *it;
                        if ( (image->dlopenCount() != 0) || (image->neverUnload() && (image->getState() >= dyld_image_state_bound)) || (image == sMainExecutable) ) {
                                OSSpinLockLock(&sDynamicReferencesLock);
                                        image->markedUsedRecursive(sDynamicReferences);
                                OSSpinLockUnlock(&sDynamicReferencesLock);
                        }
                }
#pragma clang diagnostic pop

                // collect phase: build array of images not marked in-use
                ImageLoader* deadImages[sAllImages.size()];
                unsigned deadCount = 0;
                int maxRangeCount = 0;
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                        ImageLoader* image = *it;
                        if ( ! image->isMarkedInUse() ) {
                                deadImages[deadCount++] = image;
                                if (gLogAPIs) dyld::log("dlclose(), found unused image %p %s\n", image, image->getShortName());
                                maxRangeCount += image->segmentCount();
                        }
                }

                // collect phase: run termination routines for images not marked in-use
                if ( maxRangeCount != 0 ) {
                        __cxa_range_t ranges[maxRangeCount];
                        int rangeCount = 0;
                        for (unsigned i=0; i < deadCount; ++i) {
                                ImageLoader* image = deadImages[i];
                                for (unsigned int j=0; j < image->segmentCount(); ++j) {
                                        if ( !image->segExecutable(j) )
                                                continue;
                                        if ( rangeCount < maxRangeCount ) {
                                                ranges[rangeCount].addr = (const void*)image->segActualLoadAddress(j);
                                                ranges[rangeCount].length = image->segSize(j);
                                                ++rangeCount;
                                        }
                                }
                                try {
                                        runImageStaticTerminators(image);
                                }
                                catch (const char* msg) {
                                        dyld::warn("problem running terminators for image: %s\n", msg);
                                }
                        }

                        // <rdar://problem/14718598> dyld should call __cxa_finalize_ranges()
                        if ( (rangeCount > 0) && (gLibSystemHelpers != NULL) && (gLibSystemHelpers->version >= 13) )
                                (*gLibSystemHelpers->cxa_finalize_ranges)(ranges, rangeCount);
                }

                // collect phase: delete all images which are not marked in-use
                bool mightBeMore;
                do {
                        mightBeMore = false;
                        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                                ImageLoader* image = *it;
                                if ( ! image->isMarkedInUse() ) {
                                        try {
                                                if (gLogAPIs) dyld::log("dlclose(), deleting %p %s\n", image, image->getShortName());
                                                removeImage(image);
                                                ImageLoader::deleteImage(image);
                                                mightBeMore = true;
                                                break;  // interator in invalidated by this removal
                                        }
                                        catch (const char* msg) {
                                                dyld::warn("problem deleting image: %s\n", msg);
                                        }
                                }
                        }
                } while ( mightBeMore );
        } while (sRedo);
        sDoingGC = false;

        //printAllImages();

}


static void preflight_finally(ImageLoader* image)
{
        if ( image->isBundle() ) {
                removeImageFromAllImages(image->machHeader());
                ImageLoader::deleteImage(image);
        }
        sBundleBeingLoaded = NULL;
        dyld::garbageCollectImages();
}


void preflight(ImageLoader* image, const ImageLoader::RPathChain& loaderRPaths, unsigned cacheIndex)
{
        try {
                if ( image->isBundle() ) 
                        sBundleBeingLoaded = image;     // hack
                const char* path = image->getPath();
#if SUPPORT_ACCELERATE_TABLES
                if ( image == sAllCacheImagesProxy )
                        path = sAllCacheImagesProxy->getIndexedPath(cacheIndex);
#endif
                image->link(gLinkContext, false, true, false, loaderRPaths, path);
        }
        catch (const char* msg) {       
                preflight_finally(image);
                throw;
        }
        preflight_finally(image);
}

static void loadInsertedDylib(const char* path)
{
        unsigned cacheIndex;
        try {
                LoadContext context;
                context.useSearchPaths          = false;
                context.useFallbackPaths        = false;
                context.useLdLibraryPath        = false;
                context.implicitRPath           = false;
                context.matchByInstallName      = false;
                context.dontLoad                        = false;
                context.mustBeBundle            = false;
                context.mustBeDylib                     = true;
                context.canBePIE                        = false;
                context.origin                          = NULL; // can't use @loader_path with DYLD_INSERT_LIBRARIES
                context.rpath                           = NULL;
                load(path, context, cacheIndex);
        }
        catch (const char* msg) {
                if ( gLinkContext.allowInsertFailures )
                        dyld::log("dyld: warning: could not load inserted library '%s' into hardened process because %s\n", path, msg);
                else
                        halt(dyld::mkstringf("could not load inserted library '%s' because %s\n", path, msg));
        }
        catch (...) {
                halt(dyld::mkstringf("could not load inserted library '%s'\n", path));
        }
}


static void configureProcessRestrictions(const macho_header* mainExecutableMH, const char* envp[])
{
        uint64_t amfiInputFlags = 0;
#if TARGET_OS_SIMULATOR
        amfiInputFlags |= AMFI_DYLD_INPUT_PROC_IN_SIMULATOR;
#elif __MAC_OS_X_VERSION_MIN_REQUIRED
        if ( hasRestrictedSegment(mainExecutableMH) )
                amfiInputFlags |= AMFI_DYLD_INPUT_PROC_HAS_RESTRICT_SEG;
#elif __IPHONE_OS_VERSION_MIN_REQUIRED
        if ( isFairPlayEncrypted(mainExecutableMH) )
                amfiInputFlags |= AMFI_DYLD_INPUT_PROC_IS_ENCRYPTED;
#endif
        uint64_t amfiOutputFlags = 0;
        const char* amfiFake = nullptr;
        if ( dyld3::internalInstall() && dyld3::BootArgs::enableDyldTestMode() ) {
                amfiFake = _simple_getenv(envp, "DYLD_AMFI_FAKE");
        }
        if ( amfiFake != nullptr ) {
                amfiOutputFlags = hexToUInt64(amfiFake, nullptr);
        }
        if ( (amfiFake != nullptr) || (amfi_check_dyld_policy_self(amfiInputFlags, &amfiOutputFlags) == 0) ) {
                gLinkContext.allowAtPaths                               = (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_AT_PATH);
                gLinkContext.allowEnvVarsPrint                  = (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_PRINT_VARS);
                gLinkContext.allowEnvVarsPath                   = (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_PATH_VARS);
                gLinkContext.allowEnvVarsSharedCache    = (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_CUSTOM_SHARED_CACHE);
                gLinkContext.allowClassicFallbackPaths  = (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_FALLBACK_PATHS);
                gLinkContext.allowInsertFailures        = (amfiOutputFlags & AMFI_DYLD_OUTPUT_ALLOW_FAILED_LIBRARY_INSERTION);
        }
        else {
#if __MAC_OS_X_VERSION_MIN_REQUIRED
                // support chrooting from old kernel
                bool isRestricted = false;
                bool libraryValidation = false;
                // any processes with setuid or setgid bit set or with __RESTRICT segment is restricted
                if ( issetugid() || hasRestrictedSegment(mainExecutableMH) ) {
                        isRestricted = true;
                }
                bool usingSIP = (csr_check(CSR_ALLOW_TASK_FOR_PID) != 0);
                uint32_t flags;
                if ( csops(0, CS_OPS_STATUS, &flags, sizeof(flags)) != -1 ) {
                        // On OS X CS_RESTRICT means the program was signed with entitlements
                        if ( ((flags & CS_RESTRICT) == CS_RESTRICT) && usingSIP ) {
                                isRestricted = true;
                        }
                        // Library Validation loosens searching but requires everything to be code signed
                        if ( flags & CS_REQUIRE_LV ) {
                                isRestricted = false;
                                libraryValidation = true;
                        }
                }
                gLinkContext.allowAtPaths                = !isRestricted;
                gLinkContext.allowEnvVarsPrint           = !isRestricted;
                gLinkContext.allowEnvVarsPath            = !isRestricted;
                gLinkContext.allowEnvVarsSharedCache     = !libraryValidation || !usingSIP;
                gLinkContext.allowClassicFallbackPaths   = !isRestricted;
                gLinkContext.allowInsertFailures         = false;
#else
                halt("amfi_check_dyld_policy_self() failed\n");
#endif
        }
}

// called by _dyld_register_driverkit_main()
void setMainEntry(void (*main)())
{
        if ( sEntryOveride == nullptr )
                sEntryOveride = main;
        else
                halt("_dyld_register_driverkit_main() may only be called once");
}

bool processIsRestricted()
{
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        return !gLinkContext.allowEnvVarsPath;
#else
        return false;
#endif
}


// <rdar://problem/10583252> Add dyld to uuidArray to enable symbolication of stackshots
static void addDyldImageToUUIDList()
{
        const struct macho_header* mh = (macho_header*)&__dso_handle;
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)((char*)mh + sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_UUID: {
                                uuid_command* uc = (uuid_command*)cmd;
                                dyld_uuid_info info;
                                info.imageLoadAddress = (mach_header*)mh;
                                memcpy(info.imageUUID, uc->uuid, 16);
                                addNonSharedCacheImageUUID(info);
                                return;
                        }
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
}

void notifyKernelAboutImage(const struct macho_header* mh, const char* fileInfo)
{
        const char *endptr = nullptr;
        uint64_t tmp = hexToUInt64(fileInfo, &endptr);
        fsid_t fsid = *reinterpret_cast<fsid_t *>(&tmp);
        uint64_t fsobj_id_scalar = 0;
        fsobj_id_t fsobj_id = {0};
        if (endptr != nullptr) {
                fsobj_id_scalar = hexToUInt64(endptr+1, &endptr);
                fsobj_id = *reinterpret_cast<fsobj_id_t *>(&tmp);
        }
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)((char*)mh + sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_UUID: {
                                // Add dyld to the kernel image info
                                uuid_command* uc = (uuid_command*)cmd;
                                char path[MAXPATHLEN];
                                if (fsgetpath(path, MAXPATHLEN, &fsid, fsobj_id_scalar) < 0) {
                                        path[0] = 0;
                                }
                                dyld3::kdebug_trace_dyld_image(DBG_DYLD_UUID_MAP_A, path, (const uuid_t *)&uc->uuid[0], fsobj_id, fsid, (const mach_header *)mh);
                                return;
                        }
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
}

#if __MAC_OS_X_VERSION_MIN_REQUIRED
typedef int (*open_proc_t)(const char*, int, int);
typedef int (*fcntl_proc_t)(int, int, void*);
typedef int (*ioctl_proc_t)(int, unsigned long, void*);
static void* getProcessInfo() { return dyld::gProcessInfo; }
static const SyscallHelpers sSysCalls = {
                12,
                // added in version 1
                (open_proc_t)&open, 
                &close, 
                &pread, 
                &write, 
                &mmap, 
                &munmap, 
                &madvise,
                &stat, 
                (fcntl_proc_t)&fcntl, 
                (ioctl_proc_t)&ioctl, 
                &issetugid, 
                &getcwd, 
                &realpath, 
                &vm_allocate, 
                &vm_deallocate,
                &vm_protect,
                &vlog, 
                &vwarn, 
                &pthread_mutex_lock, 
                &pthread_mutex_unlock,
                &mach_thread_self, 
                &mach_port_deallocate, 
                &task_self_trap,
                &mach_timebase_info,
                &OSAtomicCompareAndSwapPtrBarrier, 
                &OSMemoryBarrier,
                &getProcessInfo,
                &__error,
                &mach_absolute_time,
                // added in version 2
                &thread_switch,
                // added in version 3
                &opendir,
                &readdir_r,
                &closedir,
                // added in version 4
                &coresymbolication_load_notifier,
                &coresymbolication_unload_notifier,
                // Added in version 5
                &proc_regionfilename,
                &getpid,
                &mach_port_insert_right,
                &mach_port_allocate,
                &mach_msg,
                // Added in version 6
                &abort_with_payload,
                // Added in version 7
                &legacy_task_register_dyld_image_infos,
                &legacy_task_unregister_dyld_image_infos,
                &legacy_task_get_dyld_image_infos,
                &legacy_task_register_dyld_shared_cache_image_info,
                &legacy_task_register_dyld_set_dyld_state,
                &legacy_task_register_dyld_get_process_state,
                // Added in version 8
                &task_info,
                &thread_info,
                &kdebug_is_enabled,
                &kdebug_trace,
                // Added in version 9
                &kdebug_trace_string,
                // Added in version 10
                &amfi_check_dyld_policy_self,
                // Added in version 11
                &notifyMonitoringDyldMain,
                &notifyMonitoringDyld,
                // Add in version 12
                &mach_msg_destroy,
                &mach_port_construct,
                &mach_port_destruct
};

__attribute__((noinline))
static const char* useSimulatorDyld(int fd, const macho_header* mainExecutableMH, const char* dyldPath,
                                                                int argc, const char* argv[], const char* envp[], const char* apple[],
                                                                uintptr_t* startGlue, uintptr_t* mainAddr)
{
        *startGlue = 0;
        *mainAddr = 0;

        // <rdar://problem/25311921> simulator does not support restricted processes
        uint32_t flags;
        if ( csops(0, CS_OPS_STATUS, &flags, sizeof(flags)) == -1 )
                return "csops() failed";
        if ( (flags & CS_RESTRICT) == CS_RESTRICT )
                return "dyld_sim cannot be loaded in a restricted process";
        if ( issetugid() )
                return "dyld_sim cannot be loaded in a setuid process";
        if ( hasRestrictedSegment(mainExecutableMH) )
                return "dyld_sim cannot be loaded in a restricted process";

        // get file size of dyld_sim
        struct stat sb;
        if ( fstat(fd, &sb) == -1 )
                return "stat(dyld_sim) failed";

        // read first page of dyld_sim file
        uint8_t firstPage[4096];
        if ( pread(fd, firstPage, 4096, 0) != 4096 )
                return "pread(dyld_sim) failed";

        // if fat file, pick matching slice
        uint64_t fileOffset = 0;
        uint64_t fileLength = sb.st_size;
        const fat_header* fileStartAsFat = (fat_header*)firstPage;
        if ( fileStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
                if ( !fatFindBest(fileStartAsFat, &fileOffset, &fileLength) ) 
                        return "no matching arch in dyld_sim";
                // re-read buffer from start of mach-o slice in fat file
                if ( pread(fd, firstPage, 4096, fileOffset) != 4096 )
                        return "pread(dyld_sim) failed";
        }
        else if ( !isCompatibleMachO(firstPage, dyldPath) ) {
                return "dyld_sim is not compatible with the loaded process, likely due to architecture mismatch";
        }
        
        // calculate total size of dyld segments
        const macho_header* mh = (const macho_header*)firstPage;
        struct macho_segment_command* lastSeg = NULL;
        struct macho_segment_command* firstSeg = NULL;
        uintptr_t mappingSize = 0;
        uintptr_t preferredLoadAddress = 0;
        const uint32_t cmd_count = mh->ncmds;
        if ( mh->sizeofcmds > 4096 )
                return "dyld_sim load commands to large";
        if ( (sizeof(macho_header) + mh->sizeofcmds) > 4096 )
                return "dyld_sim load commands to large";
        struct linkedit_data_command* codeSigCmd = NULL;
        const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header));
        const struct load_command* const endCmds = (struct load_command*)(((char*)mh) + sizeof(macho_header) + mh->sizeofcmds);
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                uint32_t cmdLength = cmd->cmdsize;
                if ( cmdLength < 8 )
                        return "dyld_sim load command too small";
                const struct load_command* const nextCmd = (const struct load_command*)(((char*)cmd)+cmdLength);
                if ( (nextCmd > endCmds) || (nextCmd < cmd) )
                        return "dyld_sim load command too large";
                switch (cmd->cmd) {
                        case LC_SEGMENT_COMMAND:
                                {
                                        struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                                        if ( seg->vmaddr + seg->vmsize < seg->vmaddr )
                                                return "dyld_sim seg wraps address space";
                                        if ( seg->vmsize < seg->filesize )
                                                return "dyld_sim seg vmsize too small";
                                        if ( (seg->fileoff + seg->filesize) < seg->fileoff )
                                                return "dyld_sim seg size wraps address space";
                                        if ( lastSeg == NULL ) {
                                                // first segment must be __TEXT and start at beginning of file/slice
                                                firstSeg = seg;
                                                if ( strcmp(seg->segname, "__TEXT") != 0 )
                                                        return "dyld_sim first segment not __TEXT";
                                                if ( seg->fileoff != 0 )
                                                        return "dyld_sim first segment not at file offset zero";
                                                if ( seg->filesize < (sizeof(macho_header) + mh->sizeofcmds) )
                                                        return "dyld_sim first segment smaller than load commands";
                                                preferredLoadAddress = seg->vmaddr;
                                        }
                                        else {
                                                // other sements must be continguous with previous segment and not executable
                                                if ( lastSeg->fileoff + lastSeg->filesize != seg->fileoff )
                                                        return "dyld_sim segments not contiguous";
                                                if ( lastSeg->vmaddr + lastSeg->vmsize != seg->vmaddr )
                                                        return "dyld_sim segments not address contiguous";
                                                if ( (seg->initprot & VM_PROT_EXECUTE) != 0 )
                                                        return "dyld_sim non-first segment is executable";
                                        }
                                        mappingSize += seg->vmsize;
                                        lastSeg = seg;
                                }
                                break;
                        case LC_SEGMENT_COMMAND_WRONG:
                                return "dyld_sim wrong load segment load command";
                        case LC_CODE_SIGNATURE:
                                codeSigCmd = (struct linkedit_data_command*)cmd;
                                break;
                }
                cmd = nextCmd;
        }
        // last segment must be named __LINKEDIT and not writable
        if ( lastSeg == NULL )
                return "dyld_sim has no segments";
        if ( strcmp(lastSeg->segname, "__LINKEDIT") != 0 )
                return "dyld_sim last segment not __LINKEDIT";
        if ( lastSeg->initprot & VM_PROT_WRITE )
                return "dyld_sim __LINKEDIT segment writable";

        // must have code signature which is contained within LINKEDIT segment
        if ( codeSigCmd == NULL )
                return "dyld_sim not code signed";
        if ( codeSigCmd->dataoff < lastSeg->fileoff )
                return "dyld_sim code signature not in __LINKEDIT";
        if ( (codeSigCmd->dataoff + codeSigCmd->datasize) <  codeSigCmd->dataoff )
                return "dyld_sim code signature size wraps";
        if ( (codeSigCmd->dataoff + codeSigCmd->datasize) > (lastSeg->fileoff + lastSeg->filesize) )
                return "dyld_sim code signature extends beyond __LINKEDIT";

        // register code signature with kernel before mmap()ing segments
        fsignatures_t siginfo;
        siginfo.fs_file_start=fileOffset;                                                       // start of mach-o slice in fat file
        siginfo.fs_blob_start=(void*)(long)(codeSigCmd->dataoff);       // start of code-signature in mach-o file
        siginfo.fs_blob_size=codeSigCmd->datasize;                                      // size of code-signature
        int result = fcntl(fd, F_ADDFILESIGS_FOR_DYLD_SIM, &siginfo);
        if ( result == -1 ) {
                return mkstringf("dyld_sim fcntl(F_ADDFILESIGS_FOR_DYLD_SIM) failed with errno=%d", errno);
        }
        // file range covered by code signature must extend up to code signature itself
        if ( siginfo.fs_file_start < codeSigCmd->dataoff )
                return mkstringf("dyld_sim code signature does not cover all of dyld_sim. Signature covers up to 0x%08lX. Signature starts at 0x%08X", (unsigned long)siginfo.fs_file_start, codeSigCmd->dataoff);

        // reserve space, then mmap each segment
        vm_address_t loadAddress = 0;
        if ( ::vm_allocate(mach_task_self(), &loadAddress, mappingSize, VM_FLAGS_ANYWHERE) != 0 )
                return "dyld_sim cannot allocate space";
        cmd = cmds;
        struct source_version_command*  dyldVersionCmd = NULL;
        struct uuid_command*                    uuidCmd = NULL;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_SEGMENT_COMMAND:
                                {
                                        struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                                        uintptr_t requestedLoadAddress = seg->vmaddr - preferredLoadAddress + loadAddress;
                                        void* segAddress = ::mmap((void*)requestedLoadAddress, seg->filesize, seg->initprot, MAP_FIXED | MAP_PRIVATE, fd, fileOffset + seg->fileoff);
                                        //dyld::log("dyld_sim %s mapped at %p\n", seg->segname, segAddress);
                                        if ( segAddress == (void*)(-1) )
                                                return "dyld_sim mmap() of segment failed";
                                        if ( ((uintptr_t)segAddress < loadAddress) || ((uintptr_t)segAddress+seg->filesize > loadAddress+mappingSize) )
                                                return "dyld_sim mmap() to wrong location";
                                }
                                break;
                        case LC_SOURCE_VERSION:
                                dyldVersionCmd = (struct source_version_command*)cmd;
                                break;
                        case LC_UUID: {
                                uuidCmd = (uuid_command*)cmd;
                                break;
                        }
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        close(fd);

        // walk newly mapped dyld_sim __TEXT load commands to find entry point
        uintptr_t entry = 0;
        cmd = (struct load_command*)(((char*)loadAddress)+sizeof(macho_header));
        const uint32_t count = ((macho_header*)(loadAddress))->ncmds;
        for (uint32_t i = 0; i < count; ++i) {
                if (cmd->cmd == LC_UNIXTHREAD) {
                #if __i386__
                        const i386_thread_state_t* registers = (i386_thread_state_t*)(((char*)cmd) + 16);
                        // entry point must be in first segment
                        if ( registers->__eip < firstSeg->vmaddr )
                                return "dyld_sim entry point not in __TEXT segment";
                        if ( registers->__eip > (firstSeg->vmaddr + firstSeg->vmsize) )
                                return "dyld_sim entry point not in __TEXT segment";
                        entry = (registers->__eip + loadAddress - preferredLoadAddress);
                #elif __x86_64__
                        const x86_thread_state64_t* registers = (x86_thread_state64_t*)(((char*)cmd) + 16);
                        // entry point must be in first segment
                        if ( registers->__rip < firstSeg->vmaddr )
                                return "dyld_sim entry point not in __TEXT segment";
                        if ( registers->__rip > (firstSeg->vmaddr + firstSeg->vmsize) )
                                return "dyld_sim entry point not in __TEXT segment";
                        entry = (registers->__rip + loadAddress - preferredLoadAddress);
                #endif
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        if ( entry == 0 )
                return "dyld_sim entry not found";

        // notify debugger that dyld_sim is loaded
        dyld_image_info info;
        info.imageLoadAddress = (mach_header*)loadAddress;
        info.imageFilePath        = strdup(dyldPath);
        info.imageFileModDate = sb.st_mtime;
        addImagesToAllImages(1, &info);
        dyld::gProcessInfo->notification(dyld_image_adding, 1, &info);

        fsid_t fsid = {{0, 0}};
        fsobj_id_t fsobj = {0};
        ino_t inode = sb.st_ino;
        fsobj.fid_objno = (uint32_t)inode;
        fsobj.fid_generation = (uint32_t)(inode>>32);
        fsid.val[0] = sb.st_dev;
        dyld3::kdebug_trace_dyld_image(DBG_DYLD_UUID_MAP_A, dyldPath, (const uuid_t *)&uuidCmd->uuid[0], fsobj, fsid, (const mach_header *)mh);

        const char** appleParams = apple;

        // <rdar://problem/5077374> have host dyld detach macOS shared cache from process before jumping into dyld_sim
        dyld3::deallocateExistingSharedCache();

        // jump into new simulator dyld
        typedef uintptr_t (*sim_entry_proc_t)(int argc, const char* argv[], const char* envp[], const char* apple[],
                                                                const macho_header* mainExecutableMH, const macho_header* dyldMH, uintptr_t dyldSlide,
                                                                const dyld::SyscallHelpers* vtable, uintptr_t* startGlue);
        sim_entry_proc_t newDyld = (sim_entry_proc_t)entry;
        *mainAddr = (*newDyld)(argc, argv, envp, appleParams, mainExecutableMH, (macho_header*)loadAddress,
                                         loadAddress - preferredLoadAddress, 
                                         &sSysCalls, startGlue);
        return NULL;
}
#endif

// 
// If the DYLD_SKIP_MAIN environment is set to 1, dyld will return the 
// address of this function instead of main() in the target program which 
// __dyld_start jumps to. Useful for qualifying dyld itself.
//
int
fake_main()
{
        return 0;
}



#if !TARGET_OS_SIMULATOR

static bool envVarMatches(const dyld3::closure::LaunchClosure* mainClosure, const char* envp[], const char* varName)
{
        __block const char* valueFromClosure = nullptr;
        mainClosure->forEachEnvVar(^(const char* keyEqualValue, bool& stop) {
                size_t keyLen = strlen(varName);
                if ( (strncmp(varName, keyEqualValue, keyLen) == 0) && (keyEqualValue[keyLen] == '=') ) {
                        valueFromClosure = &keyEqualValue[keyLen+1];
                        stop = true;
                }
        });

        const char* valueFromEnv = _simple_getenv(envp, varName);

        bool inClosure = (valueFromClosure != nullptr);
        bool inEnv     = (valueFromEnv != nullptr);
        if ( inClosure != inEnv )
                return false;
        if ( !inClosure && !inEnv )
                return true;
        return ( strcmp(valueFromClosure, valueFromEnv) == 0 );
}

static const char* const sEnvVarsToCheck[] = {
        "DYLD_LIBRARY_PATH",
        "DYLD_FRAMEWORK_PATH",
        "DYLD_FALLBACK_LIBRARY_PATH",
        "DYLD_FALLBACK_FRAMEWORK_PATH",
        "DYLD_INSERT_LIBRARIES",
        "DYLD_IMAGE_SUFFIX",
        "DYLD_VERSIONED_FRAMEWORK_PATH",
        "DYLD_VERSIONED_LIBRARY_PATH",
        "DYLD_ROOT_PATH"
};

static bool envVarsMatch(const dyld3::closure::LaunchClosure* mainClosure, const char* envp[])
{
        for (const char* envVar : sEnvVarsToCheck) {
                if ( !envVarMatches(mainClosure, envp, envVar) ) {
                        if ( gLinkContext.verboseWarnings )
                                dyld::log("dyld: closure %p not used because %s changed\n", mainClosure, envVar);
                        return false;
                }
        }

        // FIXME: dyld3 doesn't support versioned paths so we need to fall back to dyld2 if we have them.
        // <rdar://problem/37004660> dyld3: support DYLD_VERSIONED_*_PATHs ?
        if ( sEnv.DYLD_VERSIONED_LIBRARY_PATH != nullptr ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because DYLD_VERSIONED_LIBRARY_PATH used\n", mainClosure);
                return false;
        }
        if ( sEnv.DYLD_VERSIONED_FRAMEWORK_PATH != nullptr ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because DYLD_VERSIONED_FRAMEWORK_PATH used\n", mainClosure);
                return false;
        }

        return true;
}

static bool closureValid(const dyld3::closure::LaunchClosure* mainClosure, const dyld3::closure::LoadedFileInfo& mainFileInfo,
                                                 const uint8_t* mainExecutableCDHash, bool closureInCache, const char* envp[])
{
        if ( closureInCache ) {
                // We can only use the cache closure if the cache version is the same as dyld
                if (sSharedCacheLoadInfo.loadAddress->header.formatVersion != dyld3::closure::kFormatVersion) {
                        if ( gLinkContext.verboseWarnings )
                                dyld::log("dyld: dyld closure version 0x%08X does not match dyld cache version 0x%08X\n",
                                                  dyld3::closure::kFormatVersion, sSharedCacheLoadInfo.loadAddress->header.formatVersion);
                        return false;
                }
                if (sForceInvalidSharedCacheClosureFormat) {
                        if ( gLinkContext.verboseWarnings )
                                dyld::log("dyld: closure %p dyld cache version forced invalid\n", mainClosure);
                        return false;
                }
        } else {
                // verify current dyld cache is same as expected
                uuid_t expectedCacheUUID;
                if ( mainClosure->builtAgainstDyldCache(expectedCacheUUID) ) {
                        if ( sSharedCacheLoadInfo.loadAddress == nullptr ) {
                                if ( gLinkContext.verboseWarnings )
                                        dyld::log("dyld: closure %p dyld cache not loaded\n", mainClosure);
                                return false;
                        }
                        else {
                                uuid_t actualCacheUUID;
                                sSharedCacheLoadInfo.loadAddress->getUUID(actualCacheUUID);
                                if ( memcmp(expectedCacheUUID, actualCacheUUID, sizeof(uuid_t)) != 0 ) {
                                        if ( gLinkContext.verboseWarnings )
                                                dyld::log("dyld: closure %p not used because built against different dyld cache\n", mainClosure);
                                        return false;
                                }
                        }
                }
                else {
                        // closure built assume there is no dyld cache
                        if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
                                if ( gLinkContext.verboseWarnings )
                                        dyld::log("dyld: closure %p built expecting no dyld cache\n", mainClosure);
                                return false;
                        }
                }
#if __IPHONE_OS_VERSION_MIN_REQUIRED
                // verify this closure is not from a previous reboot
                const char* expectedBootUUID = mainClosure->bootUUID();
                char actualBootSessionUUID[256] = { 0 };
                size_t bootSize = sizeof(actualBootSessionUUID);
                bool gotActualBootUUID = (sysctlbyname("kern.bootsessionuuid", actualBootSessionUUID, &bootSize, NULL, 0) == 0);
                if ( gotActualBootUUID ) {
                        // If we got a boot UUID then we should have also recorded it in the closure
                        if ( expectedBootUUID == nullptr) {
                                // The closure didn't have a UUID but now we do.  This isn't valid.
                                if ( gLinkContext.verboseWarnings )
                                        dyld::log("dyld: closure %p missing boot-UUID\n", mainClosure);
                                return false;
                        } else if ( strcmp(expectedBootUUID, actualBootSessionUUID) != 0 ) {
                                if ( gLinkContext.verboseWarnings )
                                        dyld::log("dyld: closure %p built in different boot context\n", mainClosure);
                                return false;
                        }
                } else {
                        // We didn't get a UUID now, which is ok so long as the closure also doesn't have one.
                        if ( expectedBootUUID != nullptr) {
                                if ( gLinkContext.verboseWarnings )
                                        dyld::log("dyld: closure %p has boot-UUID\n", mainClosure);
                                return false;
                        }
                }
#endif
        }

        // verify all mach-o files have not changed since closure was built
        __block bool foundFileThatInvalidatesClosure = false;
        mainClosure->images()->forEachImage(^(const dyld3::closure::Image* image, bool& stop) {
                __block uint64_t expectedInode;
                __block uint64_t expectedMtime;
                if ( image->hasFileModTimeAndInode(expectedInode, expectedMtime) ) {
                        struct stat statBuf;
                        if ( ::stat(image->path(), &statBuf) == 0 ) {
                                if ( (statBuf.st_mtime != expectedMtime) || (statBuf.st_ino != expectedInode) ) {
                                        if ( gLinkContext.verboseWarnings )
                                                dyld::log("dyld: closure %p not used because mtime/inode for '%s' has changed since closure was built\n", mainClosure, image->path());
                                        foundFileThatInvalidatesClosure = true;
                                        stop = true;
                                }
                        }
                        else {
                                if ( gLinkContext.verboseWarnings )
                                        dyld::log("dyld: closure %p not used because '%s' is needed by closure but is missing\n", mainClosure, image->path());
                                foundFileThatInvalidatesClosure = true;
                                stop = true;
                        }
                }
        });
        if ( foundFileThatInvalidatesClosure )
                return false;

        // verify cdHash of main executable is same as recorded in closure
        const dyld3::closure::Image* mainImage = mainClosure->images()->imageForNum(mainClosure->topImage());

        __block bool foundCDHash = false;
        __block bool foundValidCDHash = false;
        mainImage->forEachCDHash(^(const uint8_t *expectedHash, bool& stop) {
                if ( mainExecutableCDHash == nullptr ) {
                        if ( gLinkContext.verboseWarnings )
                                dyld::log("dyld: closure %p not used because main executable is not code signed but was expected to be\n", mainClosure);
                        stop = true;
                        return;
                }
                foundCDHash = true;
                if ( memcmp(mainExecutableCDHash, expectedHash, 20) == 0 ) {
                        // found a match, so lets use this one.
                        foundValidCDHash = true;
                        stop = true;
                        return;
                }
        });

        // If we found cd hashes, but they were all invalid, then print them out
        if ( foundCDHash && !foundValidCDHash ) {
                auto getCDHashString = [](const uint8_t cdHash[20], char* cdHashBuffer) {
                        for (int i=0; i < 20; ++i) {
                                uint8_t byte = cdHash[i];
                                uint8_t nibbleL = byte & 0x0F;
                                uint8_t nibbleH = byte >> 4;
                                if ( nibbleH < 10 ) {
                                        *cdHashBuffer = '0' + nibbleH;
                                        ++cdHashBuffer;
                                } else {
                                        *cdHashBuffer = 'a' + (nibbleH-10);
                                        ++cdHashBuffer;
                                }
                                if ( nibbleL < 10 ) {
                                        *cdHashBuffer = '0' + nibbleL;
                                        ++cdHashBuffer;
                                } else {
                                        *cdHashBuffer = 'a' + (nibbleL-10);
                                        ++cdHashBuffer;
                                }
                        }
                };
                if ( gLinkContext.verboseWarnings ) {
                        mainImage->forEachCDHash(^(const uint8_t *expectedHash, bool &stop) {
                                char mainExecutableCDHashBuffer[128] = { '\0' };
                                char expectedCDHashBuffer[128] = { '\0' };

                                getCDHashString(mainExecutableCDHash, mainExecutableCDHashBuffer);
                                getCDHashString(expectedHash, expectedCDHashBuffer);

                                dyld::log("dyld: closure %p not used because main executable cd-hash (%s) changed since closure was built with (%s)\n",
                                                  mainClosure, mainExecutableCDHashBuffer, expectedCDHashBuffer);
                        });
                }

                return false;
        }
        
        // verify UUID of main executable is same as recorded in closure
        uuid_t expectedUUID;
        bool hasExpect = mainImage->getUuid(expectedUUID);
        uuid_t actualUUID;
        const dyld3::MachOLoaded* mainExecutableMH = (const dyld3::MachOLoaded*)mainFileInfo.fileContent;
        bool hasActual = mainExecutableMH->getUuid(actualUUID);
        if ( hasExpect != hasActual ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because UUID of executable changed since closure was built\n", mainClosure);
                return false;
        }
        if ( hasExpect && hasActual && memcmp(actualUUID, expectedUUID, sizeof(uuid_t)) != 0 ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because UUID of executable changed since closure was built\n", mainClosure);
                return false;
        }

        // verify DYLD_* env vars are same as when closure was built
        if ( !envVarsMatch(mainClosure, envp) ) {
                return false;
        }

        // verify files that are supposed to be missing actually are missing
        mainClosure->forEachMustBeMissingFile(^(const char* path, bool& stop) {
                struct stat statBuf;
                if ( ::stat(path, &statBuf) == 0 ) {
                        stop = true;
                        foundFileThatInvalidatesClosure = true;
                        if ( gLinkContext.verboseWarnings )
                                dyld::log("dyld: closure %p not used because found unexpected file '%s'\n", mainClosure, path);
                }
        });

        // verify files that are supposed to exist are there with the
        mainClosure->forEachSkipIfExistsFile(^(const dyld3::closure::LaunchClosure::SkippedFile &file, bool &stop) {
                struct stat statBuf;
                if ( ::stat(file.path, &statBuf) == 0 ) {
                        if ( (statBuf.st_mtime != file.mtime) || (statBuf.st_ino != file.inode) ) {
                                if ( gLinkContext.verboseWarnings )
                                        dyld::log("dyld: closure %p not used because mtime/inode for '%s' has changed since closure was built\n", mainClosure, file.path);
                                foundFileThatInvalidatesClosure = true;
                                stop = true;
                        }
                }
        });

        // verify closure did not require anything unavailable
        if ( mainClosure->usedAtPaths() && !gLinkContext.allowAtPaths ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because is used @paths, but process does not allow that\n", mainClosure);
                return false;
        }
        if ( mainClosure->usedFallbackPaths() && !gLinkContext.allowClassicFallbackPaths ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: closure %p not used because is used default fallback paths, but process does not allow that\n", mainClosure);
                return false;
        }

        return !foundFileThatInvalidatesClosure;
}

static bool nolog(const char* format, ...)
{
        return false;
}

static bool dolog(const char* format, ...)
{
        va_list list;
        va_start(list, format);
        vlog(format, list);
        va_end(list);
        return true;
}

static bool launchWithClosure(const dyld3::closure::LaunchClosure* mainClosure,
                                                          const DyldSharedCache* dyldCache,
                                                          const dyld3::MachOLoaded* mainExecutableMH, uintptr_t mainExecutableSlide,
                                                          int argc, const char* argv[], const char* envp[], const char* apple[],
                                                          uintptr_t* entry, uintptr_t* startGlue)
{
        // build list of all known ImageArrays (at most three: cached dylibs, other OS dylibs, and main prog)
        STACK_ALLOC_ARRAY(const dyld3::closure::ImageArray*, imagesArrays, 3);
        const dyld3::closure::ImageArray* mainClosureImages = mainClosure->images();
        if ( dyldCache != nullptr ) {
                imagesArrays.push_back(dyldCache->cachedDylibsImageArray());
                if ( auto others = dyldCache->otherOSImageArray() )
                        imagesArrays.push_back(others);
        }
        imagesArrays.push_back(mainClosureImages);

        // allocate space for Array<LoadedImage>
        STACK_ALLOC_ARRAY(dyld3::LoadedImage, allImages, mainClosure->initialLoadCount());

        // Get the pre-optimized Objective-C so that we can bind the selectors
        const dyld3::closure::ObjCSelectorOpt*                                  selectorOpt = nullptr;
        dyld3::Array<dyld3::closure::Image::ObjCSelectorImage>  selectorImages;
        mainClosure->selectorHashTable(selectorImages, selectorOpt);

        __block dyld3::Loader loader({}, allImages, dyldCache, imagesArrays,
                                                                 selectorOpt, selectorImages,
                                                                 (gLinkContext.verboseLoading ? &dolog : &nolog),
                                                                 (gLinkContext.verboseMapping ? &dolog : &nolog),
                                                                 (gLinkContext.verboseBind    ? &dolog : &nolog),
                                                                 (gLinkContext.verboseDOF     ? &dolog : &nolog));
        dyld3::closure::ImageNum mainImageNum = mainClosure->topImage();
        mainClosureImages->forEachImage(^(const dyld3::closure::Image* image, bool& stop) {
                if ( image->imageNum() == mainImageNum ) {
                        // add main executable (which is already mapped by kernel) to list
                        dyld3::LoadedImage mainLoadedImage = dyld3::LoadedImage::make(image, mainExecutableMH);
                        mainLoadedImage.setState(dyld3::LoadedImage::State::mapped);
                        mainLoadedImage.markLeaveMapped();
                        loader.addImage(mainLoadedImage);
                        stop = true;
                }
                else {
                        // add inserted library to initial list
                        loader.addImage(dyld3::LoadedImage::make(image));
                }
        });

        // recursively load all dependents and fill in allImages array
        bool someCacheImageOverridden = false;
        Diagnostics diag;
        loader.completeAllDependents(diag, someCacheImageOverridden);
        if ( diag.noError() )
                loader.mapAndFixupAllImages(diag, dyld3::Loader::dtraceUserProbesEnabled());
        if ( diag.hasError() ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: %s\n", diag.errorMessage());
                return false;
        }

        //dyld::log("loaded image list:\n");
        //for (const dyld3::LoadedImage& info : allImages) {
        //      dyld::log("mh=%p, path=%s\n", info.loadedAddress(), info.image()->path());
        //}

        // find libdyld entry
        dyld3::closure::Image::ResolvedSymbolTarget dyldEntry;
        mainClosure->libDyldEntry(dyldEntry);
        const dyld3::LibDyldEntryVector* libDyldEntry = (dyld3::LibDyldEntryVector*)loader.resolveTarget(dyldEntry);

        // send info on all images to libdyld.dylb
        libDyldEntry->setVars(mainExecutableMH, argc, argv, envp, apple);
        if ( libDyldEntry->vectorVersion > 4 )
                libDyldEntry->setRestrictions(gLinkContext.allowAtPaths, gLinkContext.allowEnvVarsPath, gLinkContext.allowClassicFallbackPaths);
        libDyldEntry->setHaltFunction(&halt);
        if ( libDyldEntry->vectorVersion > 5 ) {
                libDyldEntry->setNotifyMonitoringDyldMain(&notifyMonitoringDyldMain);
                libDyldEntry->setNotifyMonitoringDyld(&notifyMonitoringDyld);
        }

        if ( libDyldEntry->vectorVersion > 6 )
                libDyldEntry->setHasCacheOverrides(someCacheImageOverridden);

        if ( libDyldEntry->vectorVersion > 2 )
                libDyldEntry->setChildForkFunction(&_dyld_fork_child);
#if !TARGET_OS_SIMULATOR
        if ( libDyldEntry->vectorVersion > 3 )
                libDyldEntry->setLogFunction(&dyld::vlog);
#endif
        libDyldEntry->setOldAllImageInfo(gProcessInfo);
        dyld3::LoadedImage* libSys = loader.findImage(mainClosure->libSystemImageNum());
        libDyldEntry->setInitialImageList(mainClosure, dyldCache, sSharedCacheLoadInfo.path, allImages, *libSys);
        // run initializers
        CRSetCrashLogMessage("dyld3: launch, running initializers");
        libDyldEntry->runInitialzersBottomUp((mach_header*)mainExecutableMH);
        //dyld::log("returned from runInitialzersBottomUp()\n");

        if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
                dyld3::kdebug_trace_dyld_duration_end(launchTraceID, DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, 0, 0, 3);
        }
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        if ( gLinkContext.driverKit ) {
                *entry = (uintptr_t)sEntryOveride;
                if ( *entry == 0 )
                        halt("no entry point registered");
                *startGlue = (uintptr_t)(libDyldEntry->startFunc);
        }
        else
#endif
        {
                dyld3::closure::Image::ResolvedSymbolTarget progEntry;
                if ( mainClosure->mainEntry(progEntry) ) {
                        // modern app with LC_MAIN
                        // set startGlue to "start" function in libdyld.dylib
                        // set entry to "main" function in program
                        *startGlue = (uintptr_t)(libDyldEntry->startFunc);
                        *entry     = loader.resolveTarget(progEntry);
                }
                else if ( mainClosure->startEntry(progEntry) ) {
                        // old style app linked with crt1.o
                        // entry is "start" function in program
                        *startGlue = 0;
                        *entry     = loader.resolveTarget(progEntry);
                }
                else {
                        assert(0);
                }
        }
        CRSetCrashLogMessage("dyld3 mode");
        return true;
}


static const char* getTempDir(const char* envp[])
{
        if (const char* tempDir = _simple_getenv(envp, "TMPDIR"))
                return tempDir;

#if __MAC_OS_X_VERSION_MIN_REQUIRED
        return "/private/tmp/";
#else
        return "/private/var/tmp/";
#endif
}

static const dyld3::closure::LaunchClosure* mapClosureFile(const char* closurePath)
{
        struct stat statbuf;
        if ( ::stat(closurePath, &statbuf) == -1 )
                return nullptr;

        // check for tombstone file
        if ( statbuf.st_size == 0 )
                return nullptr;

        int fd = ::open(closurePath, O_RDONLY);
        if ( fd < 0 )
                return nullptr;

        const dyld3::closure::LaunchClosure* closure = (dyld3::closure::LaunchClosure*)::mmap(NULL, (size_t)statbuf.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        ::close(fd);

        if ( closure == MAP_FAILED )
                return nullptr;

        return closure;
}

static bool needsDyld2ErrorMessage(const char* msg)
{
        if ( strcmp(msg, "lazy bind opcodes missing binds") == 0 )
                return true;
        return false;
}


// Note: buildLaunchClosure calls halt() if there is an error building the closure
static const dyld3::closure::LaunchClosure* buildLaunchClosure(const uint8_t* mainExecutableCDHash,
                                                                                                                           const dyld3::closure::LoadedFileInfo& mainFileInfo, const char* envp[])
{
        const dyld3::MachOLoaded* mainExecutableMH = (const dyld3::MachOLoaded*)mainFileInfo.fileContent;
        dyld3::closure::PathOverrides pathOverrides;
        pathOverrides.setFallbackPathHandling(gLinkContext.allowClassicFallbackPaths ? dyld3::closure::PathOverrides::FallbackPathMode::classic : dyld3::closure::PathOverrides::FallbackPathMode::restricted);
        pathOverrides.setEnvVars(envp, mainExecutableMH, mainFileInfo.path);
        STACK_ALLOC_ARRAY(const dyld3::closure::ImageArray*,  imagesArrays, 3);
        if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
                imagesArrays.push_back(sSharedCacheLoadInfo.loadAddress->cachedDylibsImageArray());
                if ( auto others = sSharedCacheLoadInfo.loadAddress->otherOSImageArray() )
                        imagesArrays.push_back(others);
        }

        char closurePath[PATH_MAX];
        dyld3::closure::ClosureBuilder::LaunchErrorInfo* errorInfo = (dyld3::closure::ClosureBuilder::LaunchErrorInfo*)&gProcessInfo->errorKind;
        dyld3::closure::FileSystemPhysical fileSystem;
        const dyld3::GradedArchs& archs = dyld3::GradedArchs::forCurrentOS(mainExecutableMH);
        dyld3::closure::ClosureBuilder::AtPath atPathHanding = (gLinkContext.allowAtPaths ? dyld3::closure::ClosureBuilder::AtPath::all : dyld3::closure::ClosureBuilder::AtPath::none);
        dyld3::closure::ClosureBuilder builder(dyld3::closure::kFirstLaunchClosureImageNum, fileSystem, sSharedCacheLoadInfo.loadAddress, true,
                                                                                   archs, pathOverrides, atPathHanding, gLinkContext.allowEnvVarsPath, errorInfo);
        if (sForceInvalidSharedCacheClosureFormat)
                builder.setDyldCacheInvalidFormatVersion();
        const dyld3::closure::LaunchClosure* result = builder.makeLaunchClosure(mainFileInfo, gLinkContext.allowInsertFailures);
        if ( builder.diagnostics().hasError() ) {
                const char* errMsg = builder.diagnostics().errorMessage();
                // let apps with this error fallback to dyld2 mode
                if ( needsDyld2ErrorMessage(errMsg) ) {
                        if ( dyld3::closure::LaunchClosure::buildClosureCachePath(mainFileInfo.path, closurePath, getTempDir(envp), true) ) {
                                // create empty file as a tombstone to not keep trying
                                int fd = ::open(closurePath, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
                                if ( fd != -1 ) {
                                        ::fchmod(fd, S_IRUSR);
                                        ::close(fd);
                                        if ( gLinkContext.verboseWarnings )
                                                dyld::log("dyld: just built tombstone closure for %s\n", sExecPath);
                                        // We only care about closure failures that do not also cause dyld2 to fail, so defer logging
                                        // until after dyld2 has tried to launch the binary
                                        sLogClosureFailure = true;
                                }
                        }
                        return nullptr;
                }
                // terminate process
                halt(errMsg);
        }

        if ( result == nullptr )
                return nullptr;

        if ( !closureValid(result, mainFileInfo, mainExecutableCDHash, false, envp) ) {
                // some how the freshly generated closure is invalid...
                result->deallocate();
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: somehow just built closure is invalid\n");
                return nullptr;
        }
        // try to atomically save closure to disk to speed up next launch
        if ( dyld3::closure::LaunchClosure::buildClosureCachePath(mainFileInfo.path, closurePath, getTempDir(envp), true) ) {
                char closurePathTemp[PATH_MAX];
                strlcpy(closurePathTemp, closurePath, PATH_MAX);
                int mypid = getpid();
                char pidBuf[16];
                char* s = pidBuf;
                *s++ = '.';
                putHexByte(mypid >> 24, s);
                putHexByte(mypid >> 16, s);
                putHexByte(mypid >> 8, s);
                putHexByte(mypid, s);
                *s = '\0';
                strlcat(closurePathTemp, pidBuf, PATH_MAX);
                int fd = ::open(closurePathTemp, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
                if ( fd != -1 ) {
                        ::ftruncate(fd, result->size());
                        ::write(fd, result, result->size());
                        ::fchmod(fd, S_IRUSR);
                        ::close(fd);
                        ::rename(closurePathTemp, closurePath);
                        // free built closure and mmap file() to reduce dirty memory
                        result->deallocate();
                        result = mapClosureFile(closurePath);
                }
                else if ( gLinkContext.verboseWarnings ) {
                        dyld::log("could not save closure (errno=%d) to: %s\n", errno, closurePathTemp);
                }
        }

        if ( gLinkContext.verboseWarnings )
                dyld::log("dyld: just built closure %p (size=%lu) for %s\n", result, result->size(), sExecPath);

        return result;
}

static const dyld3::closure::LaunchClosure* findCachedLaunchClosure(const uint8_t* mainExecutableCDHash,
                                                                                                                                    const dyld3::closure::LoadedFileInfo& mainFileInfo,
                                                                                                                                        const char* envp[])
{
        char closurePath[PATH_MAX];
        // build base path of $TMPDIR/dyld/<prog-name>-
        if ( !dyld3::closure::LaunchClosure::buildClosureCachePath(mainFileInfo.path, closurePath, getTempDir(envp), false) )
                return nullptr;
        const dyld3::closure::LaunchClosure* closure = mapClosureFile(closurePath);
        if ( closure == nullptr )
                return nullptr;

        if ( !closureValid(closure, mainFileInfo, mainExecutableCDHash, false, envp) ) {
                ::munmap((void*)closure, closure->size());
                return nullptr;
        }

        if ( gLinkContext.verboseWarnings )
                dyld::log("dyld: used cached closure %p (size=%lu) for %s\n", closure, closure->size(), sExecPath);

        return closure;
}

#endif // !TARGET_OS_SIMULATOR

        
static ClosureMode getPlatformDefaultClosureMode() {
#if __MAC_OS_X_VERSION_MIN_REQUIRED
#if __i386__
        // rdar://problem/32701418: Don't use dyld3 for i386 for now.
        return ClosureMode::Off;
#else
        // x86_64 defaults to using the shared cache closures
        return ClosureMode::PreBuiltOnly;
#endif // __i386__
        
#else
        // <rdar://problem/33171968> enable dyld3 mode for all OS programs when using customer dyld cache (no roots)
        if ( (sSharedCacheLoadInfo.loadAddress != nullptr) && (sSharedCacheLoadInfo.loadAddress->header.cacheType == kDyldSharedCacheTypeProduction) )
                return ClosureMode::On;
        else
                return ClosureMode::Off;
#endif // __MAC_OS_X_VERSION_MIN_REQUIRED
}

//
// Entry point for dyld.  The kernel loads dyld and jumps to __dyld_start which
// sets up some registers and call this function.
//
// Returns address of main() in target program which __dyld_start jumps to
//
uintptr_t
_main(const macho_header* mainExecutableMH, uintptr_t mainExecutableSlide, 
                int argc, const char* argv[], const char* envp[], const char* apple[], 
                uintptr_t* startGlue)
{
        if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
                launchTraceID = dyld3::kdebug_trace_dyld_duration_start(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, (uint64_t)mainExecutableMH, 0, 0);
        }

        //Check and see if there are any kernel flags
        dyld3::BootArgs::setFlags(hexToUInt64(_simple_getenv(apple, "dyld_flags"), nullptr));

    // Grab the cdHash of the main executable from the environment
        uint8_t mainExecutableCDHashBuffer[20];
        const uint8_t* mainExecutableCDHash = nullptr;
        if ( hexToBytes(_simple_getenv(apple, "executable_cdhash"), 40, mainExecutableCDHashBuffer) )
                mainExecutableCDHash = mainExecutableCDHashBuffer;

#if !TARGET_OS_SIMULATOR
        // Trace dyld's load
        notifyKernelAboutImage((macho_header*)&__dso_handle, _simple_getenv(apple, "dyld_file"));
        // Trace the main executable's load
        notifyKernelAboutImage(mainExecutableMH, _simple_getenv(apple, "executable_file"));
#endif

        uintptr_t result = 0;
        sMainExecutableMachHeader = mainExecutableMH;
        sMainExecutableSlide = mainExecutableSlide;


        // Set the platform ID in the all image infos so debuggers can tell the process type
        // FIXME: This can all be removed once we make the kernel handle it in rdar://43369446
        if (gProcessInfo->version >= 16) {
                __block bool platformFound = false;
                ((dyld3::MachOFile*)mainExecutableMH)->forEachSupportedPlatform(^(dyld3::Platform platform, uint32_t minOS, uint32_t sdk) {
                        if (platformFound) {
                                halt("MH_EXECUTE binaries may only specify one platform");
                        }
                        gProcessInfo->platform = (uint32_t)platform;
                        platformFound = true;
                });
                if (gProcessInfo->platform == (uint32_t)dyld3::Platform::unknown) {
                        // There were no platforms found in the binary. This may occur on macOS for alternate toolchains and old binaries.
                        // It should never occur on any of our embedded platforms.
#if __MAC_OS_X_VERSION_MIN_REQUIRED
                        gProcessInfo->platform = (uint32_t)dyld3::Platform::macOS;
#else
                        halt("MH_EXECUTE binaries must specify a minimum supported OS version");
#endif
                }
        }

#if __MAC_OS_X_VERSION_MIN_REQUIRED
        // Check to see if we need to override the platform
        const char* forcedPlatform = _simple_getenv(envp, "DYLD_FORCE_PLATFORM");
        if (forcedPlatform) {
                if (strncmp(forcedPlatform, "6", 1) != 0) {
                        halt("DYLD_FORCE_PLATFORM is only supported for platform 6");
                }
                const dyld3::MachOFile* mf = (dyld3::MachOFile*)sMainExecutableMachHeader;
                if (mf->allowsAlternatePlatform()) {
                        gProcessInfo->platform = PLATFORM_IOSMAC;
                }
        }

        // if this is host dyld, check to see if iOS simulator is being run
        const char* rootPath = _simple_getenv(envp, "DYLD_ROOT_PATH");
        if ( (rootPath != NULL) ) {
                // look to see if simulator has its own dyld
                char simDyldPath[PATH_MAX]; 
                strlcpy(simDyldPath, rootPath, PATH_MAX);
                strlcat(simDyldPath, "/usr/lib/dyld_sim", PATH_MAX);
                int fd = my_open(simDyldPath, O_RDONLY, 0);
                if ( fd != -1 ) {
                        const char* errMessage = useSimulatorDyld(fd, mainExecutableMH, simDyldPath, argc, argv, envp, apple, startGlue, &result);
                        if ( errMessage != NULL )
                                halt(errMessage);
                        return result;
                }
        }
        else {
                ((dyld3::MachOFile*)mainExecutableMH)->forEachSupportedPlatform(^(dyld3::Platform platform, uint32_t minOS, uint32_t sdk) {
                        if ( dyld3::MachOFile::isSimulatorPlatform(platform) )
                                halt("attempt to run simulator program outside simulator (DYLD_ROOT_PATH not set)");
                });
        }
#endif

        CRSetCrashLogMessage("dyld: launch started");

        setContext(mainExecutableMH, argc, argv, envp, apple);

        // Pickup the pointer to the exec path.
        sExecPath = _simple_getenv(apple, "executable_path");

        // <rdar://problem/13868260> Remove interim apple[0] transition code from dyld
        if (!sExecPath) sExecPath = apple[0];

#if __IPHONE_OS_VERSION_MIN_REQUIRED && !TARGET_OS_SIMULATOR
        // <rdar://54095622> kernel is not passing a real path for main executable
        if ( strncmp(sExecPath, "/var/containers/Bundle/Application/", 35) == 0 ) {
                if ( char* newPath = (char*)malloc(strlen(sExecPath)+10) ) {
                        strcpy(newPath, "/private");
                        strcat(newPath, sExecPath);
                        sExecPath = newPath;
                }
        }
#endif

        if ( sExecPath[0] != '/' ) {
                // have relative path, use cwd to make absolute
                char cwdbuff[MAXPATHLEN];
            if ( getcwd(cwdbuff, MAXPATHLEN) != NULL ) {
                        // maybe use static buffer to avoid calling malloc so early...
                        char* s = new char[strlen(cwdbuff) + strlen(sExecPath) + 2];
                        strcpy(s, cwdbuff);
                        strcat(s, "/");
                        strcat(s, sExecPath);
                        sExecPath = s;
                }
        }

        // Remember short name of process for later logging
        sExecShortName = ::strrchr(sExecPath, '/');
        if ( sExecShortName != NULL )
                ++sExecShortName;
        else
                sExecShortName = sExecPath;

    configureProcessRestrictions(mainExecutableMH, envp);

        // Check if we should force dyld3.  Note we have to do this outside of the regular env parsing due to AMFI
        if ( dyld3::internalInstall() ) {
                if (const char* useClosures = _simple_getenv(envp, "DYLD_USE_CLOSURES")) {
                        if ( strcmp(useClosures, "0") == 0 ) {
                                sClosureMode = ClosureMode::Off;
                        } else if ( strcmp(useClosures, "1") == 0 ) {
#if __MAC_OS_X_VERSION_MIN_REQUIRED

#if __i386__
                                // don't support dyld3 for 32-bit macOS
#else
                                // Also don't support dyld3 for iOSMac right now
                                if ( gProcessInfo->platform != PLATFORM_IOSMAC ) {
                                        sClosureMode = ClosureMode::On;
                                }
#endif // __i386__

#else
                                sClosureMode = ClosureMode::On;
#endif // __MAC_OS_X_VERSION_MIN_REQUIRED
                        } else {
                                dyld::warn("unknown option to DYLD_USE_CLOSURES.  Valid options are: 0 and 1\n");
                        }

                }
        }

#if __MAC_OS_X_VERSION_MIN_REQUIRED
    if ( !gLinkContext.allowEnvVarsPrint && !gLinkContext.allowEnvVarsPath && !gLinkContext.allowEnvVarsSharedCache ) {
                pruneEnvironmentVariables(envp, &apple);
                // set again because envp and apple may have changed or moved
                setContext(mainExecutableMH, argc, argv, envp, apple);
        }
        else
#endif
        {
                checkEnvironmentVariables(envp);
                defaultUninitializedFallbackPaths(envp);
        }
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        if ( gProcessInfo->platform == PLATFORM_IOSMAC ) {
                gLinkContext.rootPaths = parseColonList("/System/iOSSupport", NULL);
                gLinkContext.iOSonMac = true;
                if ( sEnv.DYLD_FALLBACK_LIBRARY_PATH == sLibraryFallbackPaths )
                        sEnv.DYLD_FALLBACK_LIBRARY_PATH = sRestrictedLibraryFallbackPaths;
                if ( sEnv.DYLD_FALLBACK_FRAMEWORK_PATH == sFrameworkFallbackPaths )
                        sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = sRestrictedFrameworkFallbackPaths;
        }
        else if ( ((dyld3::MachOFile*)mainExecutableMH)->supportsPlatform(dyld3::Platform::driverKit) ) {
                gLinkContext.driverKit = true;
                gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
        }
#endif
        if ( sEnv.DYLD_PRINT_OPTS )
                printOptions(argv);
        if ( sEnv.DYLD_PRINT_ENV ) 
                printEnvironmentVariables(envp);

        // Parse this envirionment variable outside of the regular logic as we want to accept
        // this on binaries without an entitelment
#if !TARGET_OS_SIMULATOR
        if ( _simple_getenv(envp, "DYLD_JUST_BUILD_CLOSURE") != nullptr ) {
#if TARGET_OS_IPHONE
                const char* tempDir = getTempDir(envp);
                if ( (tempDir != nullptr) && (geteuid() != 0) ) {
                        // Use realpath to prevent something like TMPRIR=/tmp/../usr/bin
                        char realPath[PATH_MAX];
                        if ( realpath(tempDir, realPath) != NULL )
                                tempDir = realPath;
                        if (strncmp(tempDir, "/private/var/mobile/Containers/", strlen("/private/var/mobile/Containers/")) == 0) {
                                sJustBuildClosure = true;
                        }
                }
#endif
                // If we didn't like the format of TMPDIR, just exit.  We don't want to launch the app as that would bring up the UI
                if (!sJustBuildClosure) {
                        _exit(EXIT_SUCCESS);
                }
        }
#endif

        if ( sJustBuildClosure )
                sClosureMode = ClosureMode::On;
        getHostInfo(mainExecutableMH, mainExecutableSlide);

        // load shared cache
        checkSharedRegionDisable((dyld3::MachOLoaded*)mainExecutableMH, mainExecutableSlide);
        if ( gLinkContext.sharedRegionMode != ImageLoader::kDontUseSharedRegion ) {
#if TARGET_OS_SIMULATOR
                if ( sSharedCacheOverrideDir)
                        mapSharedCache();
#else
                mapSharedCache();
#endif
        }

        // If we haven't got a closure mode yet, then check the environment and cache type
        if ( sClosureMode == ClosureMode::Unset ) {
                // First test to see if we forced in dyld2 via a kernel boot-arg
                if ( dyld3::BootArgs::forceDyld2() ) {
                        sClosureMode = ClosureMode::Off;
                } else if ( inDenyList(sExecPath) ) {
                        sClosureMode = ClosureMode::Off;
                } else if ( sEnv.hasOverride ) {
                        sClosureMode = ClosureMode::Off;
                } else if ( dyld3::BootArgs::forceDyld3() ) {
                        sClosureMode = ClosureMode::On;
                } else {
                        sClosureMode = getPlatformDefaultClosureMode();
                }
        }

#if !TARGET_OS_SIMULATOR
        if ( sClosureMode == ClosureMode::Off ) {
                if ( gLinkContext.verboseWarnings )
                        dyld::log("dyld: not using closure because of DYLD_USE_CLOSURES or -force_dyld2=1 override\n");
        } else {
                const dyld3::closure::LaunchClosure* mainClosure = nullptr;
                dyld3::closure::LoadedFileInfo mainFileInfo;
                mainFileInfo.fileContent = mainExecutableMH;
                mainFileInfo.path = sExecPath;
                // FIXME: If we are saving this closure, this slice offset/length is probably wrong in the case of FAT files.
                mainFileInfo.sliceOffset = 0;
                mainFileInfo.sliceLen = -1;
                struct stat mainExeStatBuf;
                if ( ::stat(sExecPath, &mainExeStatBuf) == 0 ) {
                        mainFileInfo.inode = mainExeStatBuf.st_ino;
                        mainFileInfo.mtime = mainExeStatBuf.st_mtime;
                }
                // check for closure in cache first
                if ( sSharedCacheLoadInfo.loadAddress != nullptr ) {
                        mainClosure = sSharedCacheLoadInfo.loadAddress->findClosure(sExecPath);
                        if ( gLinkContext.verboseWarnings && (mainClosure != nullptr) )
                                dyld::log("dyld: found closure %p (size=%lu) in dyld shared cache\n", mainClosure, mainClosure->size());
                }

                // We only want to try build a closure at runtime if its an iOS third party binary, or a macOS binary from the shared cache
                bool allowClosureRebuilds = false;
                if ( sClosureMode == ClosureMode::On ) {
                        allowClosureRebuilds = true;
                } else if ( (sClosureMode == ClosureMode::PreBuiltOnly) && (mainClosure != nullptr) ) {
                        allowClosureRebuilds = true;
                }

                if ( (mainClosure != nullptr) && !closureValid(mainClosure, mainFileInfo, mainExecutableCDHash, true, envp) )
                        mainClosure = nullptr;

                // If we didn't find a valid cache closure then try build a new one
                if ( (mainClosure == nullptr) && allowClosureRebuilds ) {
                        // if forcing closures, and no closure in cache, or it is invalid, check for cached closure
                        if ( !sForceInvalidSharedCacheClosureFormat )
                                mainClosure = findCachedLaunchClosure(mainExecutableCDHash, mainFileInfo, envp);
                        if ( mainClosure == nullptr ) {
                                // if  no cached closure found, build new one
                                mainClosure = buildLaunchClosure(mainExecutableCDHash, mainFileInfo, envp);
                        }
                }

                // exit dyld after closure is built, without running program
                if ( sJustBuildClosure )
                        _exit(EXIT_SUCCESS);

                // try using launch closure
                if ( mainClosure != nullptr ) {
                        CRSetCrashLogMessage("dyld3: launch started");
                        bool launched = launchWithClosure(mainClosure, sSharedCacheLoadInfo.loadAddress, (dyld3::MachOLoaded*)mainExecutableMH,
                                                                                          mainExecutableSlide, argc, argv, envp, apple, &result, startGlue);
                        if ( !launched && allowClosureRebuilds ) {
                                // closure is out of date, build new one
                                mainClosure = buildLaunchClosure(mainExecutableCDHash, mainFileInfo, envp);
                                if ( mainClosure != nullptr ) {
                                        launched = launchWithClosure(mainClosure, sSharedCacheLoadInfo.loadAddress, (dyld3::MachOLoaded*)mainExecutableMH,
                                                                                                 mainExecutableSlide, argc, argv, envp, apple, &result, startGlue);
                                }
                        }
                        if ( launched ) {
#if __has_feature(ptrauth_calls)
                                // start() calls the result pointer as a function pointer so we need to sign it.
                                result = (uintptr_t)__builtin_ptrauth_sign_unauthenticated((void*)result, 0, 0);
#endif
                                if (sSkipMain)
                                        result = (uintptr_t)&fake_main;
                                return result;
                        }
                        else {
                                if ( gLinkContext.verboseWarnings ) {
                                        dyld::log("dyld: unable to use closure %p\n", mainClosure);
                                }
                        }
                }
        }
#endif // TARGET_OS_SIMULATOR
        // could not use closure info, launch old way



        // install gdb notifier
        stateToHandlers(dyld_image_state_dependents_mapped, sBatchHandlers)->push_back(notifyGDB);
        stateToHandlers(dyld_image_state_mapped, sSingleHandlers)->push_back(updateAllImages);
        // make initial allocations large enough that it is unlikely to need to be re-alloced
        sImageRoots.reserve(16);
        sAddImageCallbacks.reserve(4);
        sRemoveImageCallbacks.reserve(4);
        sAddLoadImageCallbacks.reserve(4);
        sImageFilesNeedingTermination.reserve(16);
        sImageFilesNeedingDOFUnregistration.reserve(8);

#if !TARGET_OS_SIMULATOR
#ifdef WAIT_FOR_SYSTEM_ORDER_HANDSHAKE
        // <rdar://problem/6849505> Add gating mechanism to dyld support system order file generation process
        WAIT_FOR_SYSTEM_ORDER_HANDSHAKE(dyld::gProcessInfo->systemOrderFlag);
#endif
#endif


        try {
                // add dyld itself to UUID list
                addDyldImageToUUIDList();

#if SUPPORT_ACCELERATE_TABLES
#if __arm64e__
                // Disable accelerator tables when we have threaded rebase/bind, which is arm64e executables only for now.
                if (sMainExecutableMachHeader->cpusubtype == CPU_SUBTYPE_ARM64E)
                        sDisableAcceleratorTables = true;
#endif
                bool mainExcutableAlreadyRebased = false;
                if ( (sSharedCacheLoadInfo.loadAddress != nullptr) && !dylibsCanOverrideCache() && !sDisableAcceleratorTables && (sSharedCacheLoadInfo.loadAddress->header.accelerateInfoAddr != 0) ) {
                        struct stat statBuf;
                        if ( ::stat(IPHONE_DYLD_SHARED_CACHE_DIR "no-dyld2-accelerator-tables", &statBuf) != 0 )
                                sAllCacheImagesProxy = ImageLoaderMegaDylib::makeImageLoaderMegaDylib(&sSharedCacheLoadInfo.loadAddress->header, sSharedCacheLoadInfo.slide, mainExecutableMH, gLinkContext);
                }

reloadAllImages:
#endif


        #if __MAC_OS_X_VERSION_MIN_REQUIRED
                gLinkContext.strictMachORequired = false;
        // <rdar://problem/22805519> be less strict about old macOS mach-o binaries
        ((dyld3::MachOFile*)mainExecutableMH)->forEachSupportedPlatform(^(dyld3::Platform platform, uint32_t minOS, uint32_t sdk) {
            if ( (platform == dyld3::Platform::macOS) && (sdk >= DYLD_PACKED_VERSION(10,15,0)) ) {
                gLinkContext.strictMachORequired = true;
                        }
        });
            if ( gLinkContext.iOSonMac )
                    gLinkContext.strictMachORequired = true;
        #else
                // simulators, iOS, tvOS, watchOS, are always strict
                gLinkContext.strictMachORequired = true;
        #endif


                CRSetCrashLogMessage(sLoadingCrashMessage);
                // instantiate ImageLoader for main executable
                sMainExecutable = instantiateFromLoadedImage(mainExecutableMH, mainExecutableSlide, sExecPath);
                gLinkContext.mainExecutable = sMainExecutable;
                gLinkContext.mainExecutableCodeSigned = hasCodeSignatureLoadCommand(mainExecutableMH);

#if TARGET_OS_SIMULATOR
                // check main executable is not too new for this OS
                {
                        if ( ! isSimulatorBinary((uint8_t*)mainExecutableMH, sExecPath) ) {
                                throwf("program was built for a platform that is not supported by this runtime");
                        }
                        uint32_t mainMinOS = sMainExecutable->minOSVersion();

                        // dyld is always built for the current OS, so we can get the current OS version
                        // from the load command in dyld itself.
                        uint32_t dyldMinOS = ImageLoaderMachO::minOSVersion((const mach_header*)&__dso_handle);
                        if ( mainMinOS > dyldMinOS ) {
        #if TARGET_OS_WATCH
                                throwf("app was built for watchOS %d.%d which is newer than this simulator %d.%d",
                                                mainMinOS >> 16, ((mainMinOS >> 8) & 0xFF),
                                                dyldMinOS >> 16, ((dyldMinOS >> 8) & 0xFF));
        #elif TARGET_OS_TV
                                throwf("app was built for tvOS %d.%d which is newer than this simulator %d.%d",
                                                mainMinOS >> 16, ((mainMinOS >> 8) & 0xFF),
                                                dyldMinOS >> 16, ((dyldMinOS >> 8) & 0xFF));
        #else
                                throwf("app was built for iOS %d.%d which is newer than this simulator %d.%d",
                                                mainMinOS >> 16, ((mainMinOS >> 8) & 0xFF),
                                                dyldMinOS >> 16, ((dyldMinOS >> 8) & 0xFF));
        #endif
                        }
                }
#endif


        #if SUPPORT_ACCELERATE_TABLES
                sAllImages.reserve((sAllCacheImagesProxy != NULL) ? 16 : INITIAL_IMAGE_COUNT);
        #else
                sAllImages.reserve(INITIAL_IMAGE_COUNT);
        #endif

                // Now that shared cache is loaded, setup an versioned dylib overrides
        #if SUPPORT_VERSIONED_PATHS
                checkVersionedPaths();
        #endif


                // dyld_all_image_infos image list does not contain dyld
                // add it as dyldPath field in dyld_all_image_infos
                // for simulator, dyld_sim is in image list, need host dyld added
#if TARGET_OS_SIMULATOR
                // get path of host dyld from table of syscall vectors in host dyld
                void* addressInDyld = gSyscallHelpers;
#else
                // get path of dyld itself
                void*  addressInDyld = (void*)&__dso_handle;
#endif
                char dyldPathBuffer[MAXPATHLEN+1];
                int len = proc_regionfilename(getpid(), (uint64_t)(long)addressInDyld, dyldPathBuffer, MAXPATHLEN);
                if ( len > 0 ) {
                        dyldPathBuffer[len] = '\0'; // proc_regionfilename() does not zero terminate returned string
                        if ( strcmp(dyldPathBuffer, gProcessInfo->dyldPath) != 0 )
                                gProcessInfo->dyldPath = strdup(dyldPathBuffer);
                }

                // load any inserted libraries
                if      ( sEnv.DYLD_INSERT_LIBRARIES != NULL ) {
                        for (const char* const* lib = sEnv.DYLD_INSERT_LIBRARIES; *lib != NULL; ++lib) 
                                loadInsertedDylib(*lib);
                }
                // record count of inserted libraries so that a flat search will look at 
                // inserted libraries, then main, then others.
                sInsertedDylibCount = sAllImages.size()-1;

                // link main executable
                gLinkContext.linkingMainExecutable = true;
#if SUPPORT_ACCELERATE_TABLES
                if ( mainExcutableAlreadyRebased ) {
                        // previous link() on main executable has already adjusted its internal pointers for ASLR
                        // work around that by rebasing by inverse amount
                        sMainExecutable->rebase(gLinkContext, -mainExecutableSlide);
                }
#endif
                link(sMainExecutable, sEnv.DYLD_BIND_AT_LAUNCH, true, ImageLoader::RPathChain(NULL, NULL), -1);
                sMainExecutable->setNeverUnloadRecursive();
                if ( sMainExecutable->forceFlat() ) {
                        gLinkContext.bindFlat = true;
                        gLinkContext.prebindUsage = ImageLoader::kUseNoPrebinding;
                }

                // link any inserted libraries
                // do this after linking main executable so that any dylibs pulled in by inserted 
                // dylibs (e.g. libSystem) will not be in front of dylibs the program uses
                if ( sInsertedDylibCount > 0 ) {
                        for(unsigned int i=0; i < sInsertedDylibCount; ++i) {
                                ImageLoader* image = sAllImages[i+1];
                                link(image, sEnv.DYLD_BIND_AT_LAUNCH, true, ImageLoader::RPathChain(NULL, NULL), -1);
                                image->setNeverUnloadRecursive();
                        }
                        // only INSERTED libraries can interpose
                        // register interposing info after all inserted libraries are bound so chaining works
                        for(unsigned int i=0; i < sInsertedDylibCount; ++i) {
                                ImageLoader* image = sAllImages[i+1];
                                image->registerInterposing(gLinkContext);
                        }
                }

                // <rdar://problem/19315404> dyld should support interposition even without DYLD_INSERT_LIBRARIES
                for (long i=sInsertedDylibCount+1; i < sAllImages.size(); ++i) {
                        ImageLoader* image = sAllImages[i];
                        if ( image->inSharedCache() )
                                continue;
                        image->registerInterposing(gLinkContext);
                }
        #if SUPPORT_ACCELERATE_TABLES
                if ( (sAllCacheImagesProxy != NULL) && ImageLoader::haveInterposingTuples() ) {
                        // Accelerator tables cannot be used with implicit interposing, so relaunch with accelerator tables disabled
                        ImageLoader::clearInterposingTuples();
                        // unmap all loaded dylibs (but not main executable)
                        for (long i=1; i < sAllImages.size(); ++i) {
                                ImageLoader* image = sAllImages[i];
                                if ( image == sMainExecutable )
                                        continue;
                                if ( image == sAllCacheImagesProxy )
                                        continue;
                                image->setCanUnload();
                                ImageLoader::deleteImage(image);
                        }
                        // note: we don't need to worry about inserted images because if DYLD_INSERT_LIBRARIES was set we would not be using the accelerator table
                        sAllImages.clear();
                        sImageRoots.clear();
                        sImageFilesNeedingTermination.clear();
                        sImageFilesNeedingDOFUnregistration.clear();
                        sAddImageCallbacks.clear();
                        sRemoveImageCallbacks.clear();
                        sAddLoadImageCallbacks.clear();
                        sAddBulkLoadImageCallbacks.clear();
                        sDisableAcceleratorTables = true;
                        sAllCacheImagesProxy = NULL;
                        sMappedRangesStart = NULL;
                        mainExcutableAlreadyRebased = true;
                        gLinkContext.linkingMainExecutable = false;
                        resetAllImages();
                        goto reloadAllImages;
                }
        #endif

                // apply interposing to initial set of images
                for(int i=0; i < sImageRoots.size(); ++i) {
                        sImageRoots[i]->applyInterposing(gLinkContext);
                }
                ImageLoader::applyInterposingToDyldCache(gLinkContext);

                // Bind and notify for the main executable now that interposing has been registered
                uint64_t bindMainExecutableStartTime = mach_absolute_time();
                sMainExecutable->recursiveBindWithAccounting(gLinkContext, sEnv.DYLD_BIND_AT_LAUNCH, true);
                uint64_t bindMainExecutableEndTime = mach_absolute_time();
                ImageLoaderMachO::fgTotalBindTime += bindMainExecutableEndTime - bindMainExecutableStartTime;
                gLinkContext.notifyBatch(dyld_image_state_bound, false);

                // Bind and notify for the inserted images now interposing has been registered
                if ( sInsertedDylibCount > 0 ) {
                        for(unsigned int i=0; i < sInsertedDylibCount; ++i) {
                                ImageLoader* image = sAllImages[i+1];
                                image->recursiveBind(gLinkContext, sEnv.DYLD_BIND_AT_LAUNCH, true);
                        }
                }
                
                // <rdar://problem/12186933> do weak binding only after all inserted images linked
                sMainExecutable->weakBind(gLinkContext);
                gLinkContext.linkingMainExecutable = false;

                sMainExecutable->recursiveMakeDataReadOnly(gLinkContext);

                CRSetCrashLogMessage("dyld: launch, running initializers");
        #if SUPPORT_OLD_CRT_INITIALIZATION
                // Old way is to run initializers via a callback from crt1.o
                if ( ! gRunInitializersOldWay ) 
                        initializeMainExecutable(); 
        #else
                // run all initializers
                initializeMainExecutable(); 
        #endif

                // notify any montoring proccesses that this process is about to enter main()
                notifyMonitoringDyldMain();
                if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
                        dyld3::kdebug_trace_dyld_duration_end(launchTraceID, DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, 0, 0, 2);
                }
                ARIADNEDBG_CODE(220, 1);

#if __MAC_OS_X_VERSION_MIN_REQUIRED
                if ( gLinkContext.driverKit ) {
                        result = (uintptr_t)sEntryOveride;
                        if ( result == 0 )
                                halt("no entry point registered");
                        *startGlue = (uintptr_t)gLibSystemHelpers->startGlueToCallExit;
                }
                else
#endif
                {
                        // find entry point for main executable
                        result = (uintptr_t)sMainExecutable->getEntryFromLC_MAIN();
                        if ( result != 0 ) {
                                // main executable uses LC_MAIN, we need to use helper in libdyld to call into main()
                                if ( (gLibSystemHelpers != NULL) && (gLibSystemHelpers->version >= 9) )
                                        *startGlue = (uintptr_t)gLibSystemHelpers->startGlueToCallExit;
                                else
                                        halt("libdyld.dylib support not present for LC_MAIN");
                        }
                        else {
                                // main executable uses LC_UNIXTHREAD, dyld needs to let "start" in program set up for main()
                                result = (uintptr_t)sMainExecutable->getEntryFromLC_UNIXTHREAD();
                                *startGlue = 0;
                        }
                }
#if __has_feature(ptrauth_calls)
                // start() calls the result pointer as a function pointer so we need to sign it.
                result = (uintptr_t)__builtin_ptrauth_sign_unauthenticated((void*)result, 0, 0);
#endif
        }
        catch(const char* message) {
                syncAllImages();
                halt(message);
        }
        catch(...) {
                dyld::log("dyld: launch failed\n");
        }

        CRSetCrashLogMessage("dyld2 mode");
#if !TARGET_OS_SIMULATOR
        if (sLogClosureFailure) {
                // We failed to launch in dyld3, but dyld2 can handle it. synthesize a crash report for analytics
                dyld3::syntheticBacktrace("Could not generate launchClosure, falling back to dyld2", true);
        }
#endif

        if (sSkipMain) {
                notifyMonitoringDyldMain();
                if (dyld3::kdebug_trace_dyld_enabled(DBG_DYLD_TIMING_LAUNCH_EXECUTABLE)) {
                        dyld3::kdebug_trace_dyld_duration_end(launchTraceID, DBG_DYLD_TIMING_LAUNCH_EXECUTABLE, 0, 0, 2);
                }
                ARIADNEDBG_CODE(220, 1);
                result = (uintptr_t)&fake_main;
                *startGlue = (uintptr_t)gLibSystemHelpers->startGlueToCallExit;
        }
        
        return result;
}


} // namespace