dyld-360.22.tar.gz

[apple/dyld.git] / src / dyld.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 <dirent.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-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>


#ifndef CPU_SUBTYPE_ARM_V5TEJ
        #define CPU_SUBTYPE_ARM_V5TEJ           ((cpu_subtype_t) 7)
#endif
#ifndef CPU_SUBTYPE_ARM_XSCALE
        #define CPU_SUBTYPE_ARM_XSCALE          ((cpu_subtype_t) 8)
#endif
#ifndef CPU_SUBTYPE_ARM_V7
        #define CPU_SUBTYPE_ARM_V7                      ((cpu_subtype_t) 9)
#endif
#ifndef CPU_SUBTYPE_ARM_V7F
        #define CPU_SUBTYPE_ARM_V7F                     ((cpu_subtype_t) 10)
#endif
#ifndef CPU_SUBTYPE_ARM_V7S
        #define CPU_SUBTYPE_ARM_V7S                     ((cpu_subtype_t) 11)
#endif
#ifndef CPU_SUBTYPE_ARM_V7K
        #define CPU_SUBTYPE_ARM_V7K                     ((cpu_subtype_t) 12)
#endif
#ifndef LC_DYLD_ENVIRONMENT
        #define LC_DYLD_ENVIRONMENT                     0x27
#endif

#ifndef CPU_SUBTYPE_X86_64_H
        #define CPU_SUBTYPE_X86_64_H            ((cpu_subtype_t) 8) 
#endif  

#ifndef VM_PROT_SLIDE   
    #define VM_PROT_SLIDE 0x20
#endif

#include <vector>
#include <algorithm>

#include "mach-o/dyld_gdb.h"

#include "dyld.h"
#include "ImageLoader.h"
#include "ImageLoaderMachO.h"
#include "dyldLibSystemInterface.h"
#include "dyldSyscallInterface.h"
#if DYLD_SHARED_CACHE_SUPPORT
#include "dyld_cache_format.h"
#endif
#include <coreSymbolicationDyldSupport.h>
#if TARGET_IPHONE_SIMULATOR
        extern "C" void xcoresymbolication_load_notifier(void *connection, uint64_t load_timestamp, const char *image_path, const struct mach_header *mach_header);
        extern "C" void xcoresymbolication_unload_notifier(void *connection, uint64_t unload_timestamp, const char *image_path, const struct mach_header *mach_header);
        #define coresymbolication_load_notifier(c, t, p, h) xcoresymbolication_load_notifier(c, t, p, h)
        #define coresymbolication_unload_notifier(c, t, p, h) xcoresymbolication_unload_notifier(c, t, p, h)
#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__ || __x86_64__) && !TARGET_IPHONE_SIMULATOR)

#if __LP64__
        #define LC_SEGMENT_COMMAND              LC_SEGMENT_64
        #define LC_SEGMENT_COMMAND_WRONG LC_SEGMENT
        #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 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 addImagesToAllImages(uint32_t infoCount, const dyld_image_info info[]);
extern void removeImageFromAllImages(const mach_header* mh);
extern void setAlImageInfosHalt(const char* message, uintptr_t flags);
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[]);

// magic so CrashReporter logs message
extern "C" {
        char error_string[1024];
}
// implemented in dyldStartup.s for CrashReporter
extern "C" void dyld_fatal_error(const char* errString) __attribute__((noreturn));

// 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;
        bool                                            DYLD_PRINT_LIBRARIES_POST_LAUNCH;
        bool                                            DYLD_BIND_AT_LAUNCH;
        bool                                            DYLD_PRINT_STATISTICS;
        bool                                            DYLD_PRINT_OPTS;
        bool                                            DYLD_PRINT_ENV;
        bool                                            DYLD_DISABLE_DOFS;
        bool                                            DYLD_PRINT_CS_NOTIFICATIONS;
                            //  DYLD_SHARED_CACHE_DONT_VALIDATE ==> sSharedCacheIgnoreInodeAndTimeStamp
                            //  DYLD_SHARED_CACHE_DIR           ==> sSharedCacheDir
                                                        //      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
};



typedef std::vector<dyld_image_state_change_handler> StateHandlers;


enum RestrictedReason { restrictedNot, restrictedBySetGUid, restrictedBySegment, restrictedByEntitlements };
        
// all global state
static const char*                                      sExecPath = NULL;
static const char*                                      sExecShortName = NULL;
static const macho_header*                      sMainExecutableMachHeader = NULL;
#if CPU_SUBTYPES_SUPPORTED
static cpu_type_t                                       sHostCPU;
static cpu_subtype_t                            sHostCPUsubtype;
#endif
static ImageLoader*                                     sMainExecutable = NULL;
static bool                                                     sProcessIsRestricted = false;
static bool                                                     sProcessRequiresLibraryValidation = false;
static RestrictedReason                         sRestrictedReason = restrictedNot;
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 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 };
#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
#if DYLD_SHARED_CACHE_SUPPORT
static const dyld_cache_header*         sSharedCache = NULL;
static long                                                     sSharedCacheSlide = 0;
static bool                                                     sSharedCacheIgnoreInodeAndTimeStamp = false;
           bool                                                 gSharedCacheOverridden = false;
#if __IPHONE_OS_VERSION_MIN_REQUIRED
        static const char*                              sSharedCacheDir = IPHONE_DYLD_SHARED_CACHE_DIR;
        static bool                                             sDylibsOverrideCache = false;
        #define ENABLE_DYLIBS_TO_OVERRIDE_CACHE_SIZE 1024
#else
        static const char*                              sSharedCacheDir = MACOSX_DYLD_SHARED_CACHE_DIR;
#endif
#endif
ImageLoader::LinkContext                        gLinkContext;
bool                                                            gLogAPIs = false;
const struct LibSystemHelpers*          gLibSystemHelpers = NULL;
#if SUPPORT_OLD_CRT_INITIALIZATION
bool                                                            gRunInitializersOldWay = false;
#endif
static std::vector<DylibOverride>       sDylibOverrides;
#if !TARGET_IPHONE_SIMULATOR    
static int                                                      sLogSocket = -1;
#endif
static bool                                                     sFrameworksFoundAsDylibs = false;
#if __x86_64__
static bool                                                     sHaswell = false;
#endif
static std::vector<ImageLoader::DynamicReference> sDynamicReferences;
static OSSpinLock                                       sDynamicReferencesLock = 0;
static bool                                                     sLogToFile = false;
static char                                                     sLoadingCrashMessage[1024] = "dyld: launch, loading dependent libraries";

//
// 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
{
        enum { count=400 };
        struct {
                ImageLoader*    image;
                uintptr_t               start;
                uintptr_t               end;
        } array[count];
        MappedRanges*           next;
};

static MappedRanges                     sMappedRangesStart;

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 (int i=0; i < MappedRanges::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
        MappedRanges* newRanges = (MappedRanges*)malloc(sizeof(MappedRanges));
        bzero(newRanges, sizeof(MappedRanges));
        newRanges->array[0].start = start;
        newRanges->array[0].end = end;
        newRanges->array[0].image = image;
        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 (int i=0; i < MappedRanges::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;
                        }
                }
        }
}

ImageLoader* findMappedRange(uintptr_t target)
{
        for (MappedRanges* p = &sMappedRangesStart; p != NULL; p = p->next) {
                for (int i=0; i < MappedRanges::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_IPHONE_SIMULATOR
static int sLogfile = STDERR_FILENO;
#endif

#if LOG_BINDINGS
static int sBindingsLogfile = -1;
static void mysprintf(char* dst, 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);
                strcpy(dst, _simple_string(buf));
                _simple_sfree(buf);
        }
        else {
                strcpy(dst, "out of memory");
        }
}
void logBindings(const char* format, ...) 
{
        if ( sBindingsLogfile != -1 ) {
                va_list list;
                va_start(list, format);
                _simple_vdprintf(sBindingsLogfile, format, list);
                va_end(list);
        }
}
#endif

#if !TARGET_IPHONE_SIMULATOR    
// based on CFUtilities.c: also_do_stderr()
static bool useSyslog()
{
        // Use syslog() for processes managed by launchd
        if ( (gLibSystemHelpers != NULL) && (gLibSystemHelpers->version >= 11) ) {
                if ( (*gLibSystemHelpers->isLaunchdOwned)() ) {
                        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 ( !sLogToFile && useSyslog() ) 
                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);
}


#endif // !TARGET_IPHONE_SIMULATOR      


// <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);
}


// 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
//
static void 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++)
                        (*it)(image->machHeader(), image->getSlide());
                image->setAddFuncNotified();
        }
}



// 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;
}

static void notifySingle(dyld_image_states state, const ImageLoader* image)
{
        //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);
                        }
                }
        }
    // mach message csdlc about dynamically unloaded images
        if ( image->addFuncNotified() && (state == dyld_image_state_terminated) ) {
                uint64_t loadTimestamp = mach_absolute_time();
                if ( sEnv.DYLD_PRINT_CS_NOTIFICATIONS ) {
                        dyld::log("dyld: coresymbolication_unload_notifier(%p, 0x%016llX, %p, %s)\n",
                                          dyld::gProcessInfo->coreSymbolicationShmPage, loadTimestamp, image->machHeader(), image->getPath());
                }
                if ( dyld::gProcessInfo->coreSymbolicationShmPage != NULL) {
                        coresymbolication_unload_notifier(dyld::gProcessInfo->coreSymbolicationShmPage, loadTimestamp, image->getPath(), image->machHeader());
                }
        }
}




//
// 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)
{
        std::vector<dyld_image_state_change_handler>* handlers = stateToHandlers(state, sBatchHandlers);
        if ( handlers != NULL ) {
                // don't use a vector because it will use malloc/free and we want notifcation to be low cost
        allImagesLock();
        ImageLoader* images[sAllImages.size()+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 count = (uint32_t)(end-images);
                if ( end != images ) {
                        // sort bottom up
                        qsort(images, count, sizeof(ImageLoader*), &imageSorter);
                        // build info array
                        dyld_image_info infos[count];
                        for (unsigned int i=0; i < count; ++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();
                                // special case for add_image hook
                                if ( state == dyld_image_state_bound )
                                        notifyAddImageCallbacks(image);
                        }
                        
                        if ( onlyHandler != NULL ) {
                                const char* result = (*onlyHandler)(state, count, 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 
                                for (std::vector<dyld_image_state_change_handler>::iterator it = handlers->begin(); it != handlers->end(); ++it) {
                                        const char* result = (*it)(state, count, 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;
                                        }
                                }
                        }
                        if ( (state == dyld_image_state_dependents_mapped) && ((dyld::gProcessInfo->coreSymbolicationShmPage != NULL) || sEnv.DYLD_PRINT_CS_NOTIFICATIONS) ) {
                                // mach message csdlc about loaded images
                                uint64_t loadTimestamp = mach_absolute_time();
                                for (unsigned j=0; j < count; ++j) {
                                        if ( sEnv.DYLD_PRINT_CS_NOTIFICATIONS ) {
                                                dyld::log("dyld: coresymbolication_load_notifier(%p, 0x%016llX, %p, %s)\n",
                                                                  dyld::gProcessInfo->coreSymbolicationShmPage, loadTimestamp, infos[j].imageLoadAddress, infos[j].imageFilePath);
                                        }
                                        coresymbolication_load_notifier(dyld::gProcessInfo->coreSymbolicationShmPage, loadTimestamp, infos[j].imageFilePath, infos[j].imageLoadAddress);
                                }
                        }
                }
        allImagesUnlock();
        if ( dontLoadReason != NULL )
            throw dontLoadReason;
        }
}



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

// 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()
{
        return (unsigned int)sAllImages.size();
}


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 void addDynamicReference(ImageLoader* from, ImageLoader* to) {
        // don't add dynamic reference if either are in the shared cache
        if( from->inSharedCache() )
                return;
        if( to->inSharedCache() )
                return;

        // don't add dynamic reference if there already is a static one
        if ( from->dependsOn(to) )
                return;
        
        // 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);
}

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 ( sEnv.DYLD_PRINT_LIBRARIES || (sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH && (sMainExecutable!=NULL) && sMainExecutable->isLinked()) ) {
                dyld::log("dyld: loaded: %s\n", image->getPath());
        }
        
}

//
// 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++) {
                        (*it)(image->machHeader(), image->getSlide());
                }
                sRemoveImageCallbacksInUse = false;
        }
        
        // notify 
        notifySingle(dyld_image_state_terminated, image);
        
        // 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();
        
        // remove from sDynamicReferences
        OSSpinLockLock(&sDynamicReferencesLock);
                sDynamicReferences.erase(std::remove_if(sDynamicReferences.begin(), sDynamicReferences.end(), RefUsesImage(image)), sDynamicReferences.end());
        OSSpinLockUnlock(&sDynamicReferencesLock);

        // 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;
                }
        }

        // log if requested
        if ( sEnv.DYLD_PRINT_LIBRARIES || (sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH && (sMainExecutable!=NULL) && sMainExecutable->isLinked()) ) {
                dyld::log("dyld: unloaded: %s\n", image->getPath());
        }

        // 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);
        }
        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[sAllImages.size()];
        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 )
                ImageLoaderMachO::printStatistics((unsigned int)sAllImages.size(), 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];
        int 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];
        int 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) ) {
                                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) ) {
                                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) ) {
                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) ) {
                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;
                // leak old arrays
                *storage = combinedList;
        }
}

 
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;
}


#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);
        }
        else if ( strcmp(key, "DYLD_FALLBACK_FRAMEWORK_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FALLBACK_FRAMEWORK_PATH);
        }
        else if ( strcmp(key, "DYLD_LIBRARY_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_LIBRARY_PATH);
        }
        else if ( strcmp(key, "DYLD_FALLBACK_LIBRARY_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_FALLBACK_LIBRARY_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;
                                }
                        }
                }
        } 
        else if ( strcmp(key, "DYLD_IMAGE_SUFFIX") == 0 ) {
                gLinkContext.imageSuffix = value;
        }
        else if ( strcmp(key, "DYLD_INSERT_LIBRARIES") == 0 ) {
                sEnv.DYLD_INSERT_LIBRARIES = parseColonList(value, NULL);
        }
        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_DISABLE_PREFETCH") == 0 ) {
                gLinkContext.preFetchDisabled = true;
        }
        else if ( strcmp(key, "DYLD_PRINT_LIBRARIES") == 0 ) {
                sEnv.DYLD_PRINT_LIBRARIES = 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;
        }
        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;
        }
        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_CS_NOTIFICATIONS") == 0 ) {
                sEnv.DYLD_PRINT_CS_NOTIFICATIONS = 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 ) {
                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");
                }
        }
#if DYLD_SHARED_CACHE_SUPPORT
        else if ( strcmp(key, "DYLD_SHARED_CACHE_DIR") == 0 ) {
        sSharedCacheDir = value;
        }
        else if ( strcmp(key, "DYLD_SHARED_CACHE_DONT_VALIDATE") == 0 ) {
                sSharedCacheIgnoreInodeAndTimeStamp = true;
        }
#endif
        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);
        }
        else if ( strcmp(key, "DYLD_VERSIONED_FRAMEWORK_PATH") == 0 ) {
                appendParsedColonList(value, mainExecutableDir, &sEnv.DYLD_VERSIONED_FRAMEWORK_PATH);
        }
#endif
#if !TARGET_IPHONE_SIMULATOR
        else if ( (strcmp(key, "DYLD_PRINT_TO_FILE") == 0) && (mainExecutableDir == NULL) ) {
                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);
                }
        }
#endif
        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);
                                                                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  


//
// 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)
{
        // 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;
// <rdar://11894054> Disable warnings about DYLD_ env vars being ignored.  The warnings are causing too much confusion.
#if 0
        if ( removedCount != 0 ) {
                dyld::log("dyld: DYLD_ environment variables being ignored because ");
                switch (sRestrictedReason) {
                        case restrictedNot:
                                break;
                        case restrictedBySetGUid:
                                dyld::log("main executable (%s) is setuid or setgid\n", sExecPath);
                                break;
                        case restrictedBySegment:
                                dyld::log("main executable (%s) has __RESTRICT/__restrict section\n", sExecPath);
                                break;
                        case restrictedByEntitlements:
                                dyld::log("main executable (%s) is code signed with entitlements\n", sExecPath);
                                break;
                }
        }
#endif
        // 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));
}

static void defaultUninitializedFallbackPaths(const char* envp[])
{
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        // 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[])
{
        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';
                                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   
        
        // <rdar://problem/11281064> DYLD_IMAGE_SUFFIX and DYLD_ROOT_PATH cannot be used together
        if ( (gLinkContext.imageSuffix != NULL) && (gLinkContext.rootPaths != NULL) ) {
                dyld::warn("Ignoring DYLD_IMAGE_SUFFIX because DYLD_ROOT_PATH is used.\n");
                gLinkContext.imageSuffix = NULL;
        }
}

#if __x86_64__
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;
#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__
        #if TARGET_IPHONE_SIMULATOR
          sHaswell = false;
        #else
          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()
{
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        // if main executable has segments that overlap the shared region, 
        // then disable using the shared region
        if ( sMainExecutable->overlapsWithAddressRange((void*)(uintptr_t)SHARED_REGION_BASE, (void*)(uintptr_t)(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 ( sProcessIsRestricted ) {
                // <rdar://problem/15280847> use private or no shared region for suid processes
                gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
        }
#endif
#endif
        // iPhoneOS 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)
{
        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 ) {
                                                        if ( strcmp( gLinkContext.imageSuffix, &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 __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_LIB64|CPU_SUBTYPE_X86_64_H, 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_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 __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 __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

//
// 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 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 & CPU_TYPE_MASK) == 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 ) 
                        return fatFindBestFromOrderedList(cpu, subTypePreferenceList, fh, offset, len);
                
                // 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 & CPU_TYPE_MASK) == 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 ImageLoader* 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 image;
        }
        
        throw "main executable not a known format";
}


#if DYLD_SHARED_CACHE_SUPPORT
static bool findInSharedCacheImage(const char* path, bool searchByPath, const struct stat* stat_buf, const macho_header** mh, const char** pathInCache, long* slide)
{
        if ( sSharedCache != NULL ) {
#if __MAC_OS_X_VERSION_MIN_REQUIRED     
                // Mac OS X always requires inode/mtime to valid cache
                // if stat() not done yet, do it now
                struct stat statb;
                if ( stat_buf == NULL ) {
                        if ( my_stat(path, &statb) == -1 )
                                return false;
                        stat_buf = &statb;
                }
#endif
#if __IPHONE_OS_VERSION_MIN_REQUIRED    
                uint64_t hash = 0;
                for (const char* s=path; *s != '\0'; ++s)
                        hash += hash*4 + *s;
#endif

                // walk shared cache to see if there is a cached image that matches the inode/mtime/path desired
                const dyld_cache_image_info* const start = (dyld_cache_image_info*)((uint8_t*)sSharedCache + sSharedCache->imagesOffset);
                const dyld_cache_image_info* const end = &start[sSharedCache->imagesCount];
#if __IPHONE_OS_VERSION_MIN_REQUIRED    
                const bool cacheHasHashInfo = (start->modTime == 0);
#endif
                for( const dyld_cache_image_info* p = start; p != end; ++p) {
#if __IPHONE_OS_VERSION_MIN_REQUIRED    
                        // just check path
                        const char* aPath = (char*)sSharedCache + p->pathFileOffset;
                        if ( cacheHasHashInfo && (p->inode != hash) )
                                continue;
                        if ( strcmp(path, aPath) == 0 ) {
                                // found image in cache
                                *mh = (macho_header*)(p->address+sSharedCacheSlide);
                                *pathInCache = aPath;
                                *slide = sSharedCacheSlide;
                                return true;
                        }
#elif __MAC_OS_X_VERSION_MIN_REQUIRED
                        // check mtime and inode first because it is fast
                        bool inodeMatch = ( ((time_t)p->modTime == stat_buf->st_mtime) && ((ino_t)p->inode == stat_buf->st_ino) );
                        if ( searchByPath || sSharedCacheIgnoreInodeAndTimeStamp || inodeMatch ) {
                                // mod-time and inode match an image in the shared cache, now check path
                                const char* aPath = (char*)sSharedCache + p->pathFileOffset;
                                bool cacheHit = (strcmp(path, aPath) == 0);
                                if ( inodeMatch && !cacheHit ) {
                                        // path does not match install name of dylib in cache, but inode and mtime does match
                                        // perhaps path is a symlink to the cached dylib
                                        struct stat pathInCacheStatBuf;
                                        if ( my_stat(aPath, &pathInCacheStatBuf) != -1 )
                                                cacheHit = ( (pathInCacheStatBuf.st_dev == stat_buf->st_dev) && (pathInCacheStatBuf.st_ino == stat_buf->st_ino) );      
                                }
                                if ( cacheHit ) {
                                        // found image in cache, return info
                                        *mh = (macho_header*)(p->address+sSharedCacheSlide);
                                        //dyld::log("findInSharedCacheImage(), mh=%p, p->address=0x%0llX, slid=0x%0lX, path=%p\n", 
                                        //      *mh, p->address, sSharedCacheSlide, aPath);
                                        *pathInCache = aPath;
                                        *slide = sSharedCacheSlide;
                                        return true;
                                }
                        }
#endif
                }       
        }
        return false;
}

bool inSharedCache(const char* path)
{
        const macho_header* mhInCache;
        const char*                     pathInCache;
        long                            slide;
        return findInSharedCacheImage(path, true, NULL, &mhInCache, &pathInCache, &slide);
}

#endif

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_IPHONE_SIMULATOR     
static bool isSimulatorBinary(const uint8_t* firstPage, const char* path)
{
        const macho_header* mh = (macho_header*)firstPage;
        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_VERSION_MIN_IPHONEOS:
                        case LC_VERSION_MIN_TVOS:
                        case LC_VERSION_MIN_WATCHOS:
                                return true;
                        case LC_VERSION_MIN_MACOSX:
                                // grandfather in a few libSystem dylibs
                                if (strstr(path, "/usr/lib/system") || strstr(path, "/usr/lib/libSystem"))
                                        return true;
                                return false;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                if ( cmd > cmdsReadEnd )
                        return true;
        }
        return false;
}
#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 firstPage[4096];
        bool shortPage = false;
        
        // min mach-o file is 4K
        if ( fileLength < 4096 ) {
                if ( pread(fd, firstPage, fileLength, 0) != (ssize_t)fileLength )
                        throwf("pread of short file failed: %d", errno);
                shortPage = true;
        } 
        else {
                if ( pread(fd, firstPage, 4096,0) != 4096 )
                        throwf("pread of first 4K failed: %d", errno);
        }
        
        // if fat wrapper, find usable sub-file
        const fat_header* fileStartAsFat = (fat_header*)firstPage;
        if ( fileStartAsFat->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
                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, firstPage, 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(firstPage, path) ) {

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

#if TARGET_IPHONE_SIMULATOR     
        #if TARGET_OS_WATCH || TARGET_OS_TV
                // disable error during bring up of these simulators
        #else
                // <rdar://problem/14168872> dyld_sim should restrict loading osx binaries
                if ( !isSimulatorBinary(firstPage, path) ) {
                        throw "mach-o, but not built for iOS simulator";
                }
        #endif
#endif

                // instantiate an image
                ImageLoader* image = ImageLoaderMachO::instantiateFromFile(path, fd, firstPage, fileOffset, fileLength, stat_buf, gLinkContext);
                
                // validate
                return checkandAddImage(image, context);
        }
        
        // try other file formats here...
        
        
        // throw error about what was found
        switch (*(uint32_t*)firstPage) {
                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", 
                        firstPage[0], firstPage[1], firstPage[2], firstPage[3], firstPage[4], firstPage[5], firstPage[6],firstPage[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 = 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;
        }
}


#if __MAC_OS_X_VERSION_MIN_REQUIRED     
static ImageLoader* loadPhase5load(const char* path, const char* orgPath, const LoadContext& context, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        ImageLoader* image = NULL;

        // just return NULL if file not found, but record any other errors
        struct stat stat_buf;
        if ( my_stat(path, &stat_buf) == -1 ) {
                int err = errno;
                if ( err != ENOENT ) {
                        exceptions->push_back(dyld::mkstringf("%s: stat() failed with errno=%d", path, err));
                }
                return NULL;
        }
        
        // in case image was renamed or found via symlinks, check for inode match
        image = findLoadedImage(stat_buf);
        if ( image != NULL )
                return image;
        
        // do nothing if not already loaded and if RTLD_NOLOAD or NSADDIMAGE_OPTION_RETURN_ONLY_IF_LOADED
        if ( context.dontLoad )
                return NULL;

#if DYLD_SHARED_CACHE_SUPPORT
        // see if this image is in shared cache
        const macho_header* mhInCache;
        const char*                     pathInCache;
        long                            slideInCache;
        if ( findInSharedCacheImage(path, false, &stat_buf, &mhInCache, &pathInCache, &slideInCache) ) {
                image = ImageLoaderMachO::instantiateFromCache(mhInCache, pathInCache, slideInCache, stat_buf, gLinkContext);
                return checkandAddImage(image, context);
        }
#endif
        // file exists and is not in dyld shared cache, so open it
        return loadPhase5open(path, context, stat_buf, exceptions);
}
#endif // __MAC_OS_X_VERSION_MIN_REQUIRED



#if __IPHONE_OS_VERSION_MIN_REQUIRED 
static ImageLoader* loadPhase5stat(const char* path, const LoadContext& context, struct stat* stat_buf, 
                                                                        int* statErrNo, bool* imageFound, std::vector<const char*>* exceptions)
{
        ImageLoader* image = NULL;
        *imageFound = false;
        *statErrNo = 0;
        if ( my_stat(path, stat_buf) == 0 ) {
                // in case image was renamed or found via symlinks, check for inode match
                image = findLoadedImage(*stat_buf);
                if ( image != NULL ) {
                        *imageFound = true;
                        return image;
                }
                // do nothing if not already loaded and if RTLD_NOLOAD 
                if ( context.dontLoad ) {
                        *imageFound = true;
                        return NULL;
                }
                image = loadPhase5open(path, context, *stat_buf, exceptions);
                if ( image != NULL ) {
                        *imageFound = true;
                        return image;
                }
        }
        else {
                *statErrNo = errno;
        }
        return NULL;
}

// try to open file
static ImageLoader* loadPhase5load(const char* path, const char* orgPath, const LoadContext& context, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        struct stat stat_buf;
        bool imageFound;
        int statErrNo;
        ImageLoader* image;
#if DYLD_SHARED_CACHE_SUPPORT
        if ( sDylibsOverrideCache ) {
                // flag is set that allows installed framework roots to override dyld shared cache
                image = loadPhase5stat(path, context, &stat_buf, &statErrNo, &imageFound, exceptions);
                if ( imageFound )
                        return image;
        }
        // see if this image is in shared cache
        const macho_header* mhInCache;
        const char*                     pathInCache;
        long                            slideInCache;
        if ( findInSharedCacheImage(path, true, NULL, &mhInCache, &pathInCache, &slideInCache) ) {
                // 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 macho_header*)anImage->machHeader() == mhInCache )
                                return anImage;
                }
                // do nothing if not already loaded and if RTLD_NOLOAD 
                if ( context.dontLoad )
                        return NULL;
                // nope, so instantiate a new image from dyld shared cache
                // <rdar://problem/7014995> zero out stat buffer so mtime, etc are zero for items from the shared cache
                bzero(&stat_buf, sizeof(stat_buf));
                image = ImageLoaderMachO::instantiateFromCache(mhInCache, pathInCache, slideInCache, stat_buf, gLinkContext);
                return checkandAddImage(image, context);
        }
        
        if ( !sDylibsOverrideCache ) {
                // flag is not set, and not in cache to try opening it
                image = loadPhase5stat(path, context, &stat_buf, &statErrNo, &imageFound, exceptions);
                if ( imageFound )
                        return image;
        }
#else
        image = loadPhase5stat(path, context, &stat_buf, &statErrNo, &imageFound, exceptions);
        if ( imageFound )
                return image;
#endif
        // just return NULL if file not found, but record any other errors
        if ( (statErrNo != ENOENT) && (statErrNo != 0) ) {
                exceptions->push_back(dyld::mkstringf("%s: stat() failed with errno=%d", path, statErrNo));
        }
        return NULL;
}
#endif // __IPHONE_OS_VERSION_MIN_REQUIRED


// 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, 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, 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, std::vector<const char*>* exceptions)
{
        //dyld::log("%s(%s, %p)\n", __func__ , path, exceptions);
        ImageLoader* image = NULL;
        if (  gLinkContext.imageSuffix != NULL ) {
                char pathWithSuffix[strlen(path)+strlen( gLinkContext.imageSuffix)+2];
                ImageLoader::addSuffix(path,  gLinkContext.imageSuffix, pathWithSuffix);
                image = loadPhase5(pathWithSuffix, orgPath, context, exceptions);
        }
        if ( image == NULL )
                image = loadPhase5(path, orgPath, context, exceptions);
        return image;
}

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


// expand @ variables
static ImageLoader* loadPhase3(const char* path, const char* orgPath, const LoadContext& context, 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 ( sProcessIsRestricted && !sProcessRequiresLibraryValidation )
                        throwf("unsafe use of @executable_path in %s with restricted binary", 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, 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);
                        char* addPoint = strrchr(newRealPath,'/');
                        if ( addPoint != NULL )
                                strcpy(&addPoint[1], &path[17]);
                        else
                                strcpy(newRealPath, &path[17]);
                        image = loadPhase4(newRealPath, orgPath, context, 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 ( sProcessIsRestricted && (strcmp(context.origin, sExecPath) == 0) && !sProcessRequiresLibraryValidation )
                        throwf("unsafe use of @loader_path in %s with restricted binary", 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, 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);
                        char* addPoint = strrchr(newRealPath,'/');
                        if ( addPoint != NULL )
                                strcpy(&addPoint[1], &path[13]);
                        else
                                strcpy(newRealPath, &path[13]);
                        image = loadPhase4(newRealPath, orgPath, context, 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);
                                        strcat(newPath, "/"); 
                                        strcat(newPath, trailingPath); 
                                        image = loadPhase4(newPath, orgPath, context, 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 to 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, 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 (sProcessIsRestricted && (path[0] != '/' ) && !sProcessRequiresLibraryValidation) {
                throwf("unsafe use of relative rpath %s in %s with restricted binary", path, context.origin);
        }
        
        return loadPhase4(path, orgPath, context, exceptions);
}


// try search paths
static ImageLoader* loadPhase2(const char* path, const char* orgPath, const LoadContext& context, 
                                                           const char* const frameworkPaths[], const char* const libraryPaths[], 
                                                           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, exceptions);
                                if ( image != NULL )
                                        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, exceptions);
                        if ( image != NULL )
                                return image;
                }
        }
        return NULL;
}

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

        // 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, 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, exceptions);
                if ( image != NULL )
                        return image;
        }
        
        // try raw path
        image = loadPhase3(path, orgPath, context, 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, exceptions);
                if ( image != NULL )
                        return image;
        }
                
        return NULL;
}

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

        // 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) {
                        char newPath[strlen(*rootPath) + strlen(path)+2];
                        strcpy(newPath, *rootPath);
                        strcat(newPath, path);
                        ImageLoader* image = loadPhase1(newPath, orgPath, context, exceptions);
                        if ( image != NULL )
                                return image;
                }
        }

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

#if DYLD_SHARED_CACHE_SUPPORT
        static bool cacheablePath(const char* path) {
                if (strncmp(path, "/usr/lib/", 9) == 0)
                        return true;
                if (strncmp(path, "/System/Library/", 16) == 0)
                        return true;
                return false;
        }
#endif

//
// 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)
{
        CRSetCrashLogMessage2(path);
        const char* orgPath = path;
        
        //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) ) {
                if ( realpath(path, realPath) != NULL )
                        path = realPath;
        }
        
        // try all path permutations and check against existing loaded images
        ImageLoader* image = loadPhase0(path, orgPath, context, 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, &exceptions);
#if __IPHONE_OS_VERSION_MIN_REQUIRED && DYLD_SHARED_CACHE_SUPPORT && !TARGET_IPHONE_SIMULATOR
        // <rdar://problem/16704628> support symlinks on disk to a path in dyld shared cache
        if ( (image == NULL) && cacheablePath(path) && !context.dontLoad ) {
                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) )
                {
                        // see if this image is in shared cache
                        const macho_header* mhInCache;
                        const char*                     pathInCache;
                        long                            slideInCache;
                        if ( findInSharedCacheImage(resolvedPath, false, NULL, &mhInCache, &pathInCache, &slideInCache) ) {
                                struct stat stat_buf;
                                bzero(&stat_buf, sizeof(stat_buf));
                                try {
                                        image = ImageLoaderMachO::instantiateFromCache(mhInCache, pathInCache, slideInCache, stat_buf, gLinkContext);
                                        image = checkandAddImage(image, context);
                                }
                                catch (...) {
                                        image = NULL;
                                }
                        }
                }
        }
#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 DYLD_SHARED_CACHE_SUPPORT
                // 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() && cacheablePath(path) && inSharedCache(path) ) {
                        gSharedCacheOverridden = true;
                }
#endif
                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;
        }
}



#if DYLD_SHARED_CACHE_SUPPORT



#if __i386__
        #define ARCH_NAME                       "i386"
        #define ARCH_CACHE_MAGIC        "dyld_v1    i386"
#elif __x86_64__
        #define ARCH_NAME                       "x86_64"
        #define ARCH_CACHE_MAGIC        "dyld_v1  x86_64"
        #define ARCH_NAME_H                     "x86_64h"
        #define ARCH_CACHE_MAGIC_H      "dyld_v1 x86_64h"
#elif __ARM_ARCH_5TEJ__
        #define ARCH_NAME                       "armv5"
        #define ARCH_CACHE_MAGIC        "dyld_v1   armv5"
#elif __ARM_ARCH_6K__
        #define ARCH_NAME                       "armv6"
        #define ARCH_CACHE_MAGIC        "dyld_v1   armv6"
#elif __ARM_ARCH_7F__
        #define ARCH_NAME                       "armv7f"
        #define ARCH_CACHE_MAGIC        "dyld_v1  armv7f"
#elif __ARM_ARCH_7K__
        #define ARCH_NAME                       "armv7k"
        #define ARCH_CACHE_MAGIC        "dyld_v1  armv7k"
#elif __ARM_ARCH_7A__
        #define ARCH_NAME                       "armv7"
        #define ARCH_CACHE_MAGIC        "dyld_v1   armv7"
#elif __ARM_ARCH_7S__
        #define ARCH_NAME                       "armv7s"
        #define ARCH_CACHE_MAGIC        "dyld_v1  armv7s"
#elif __arm64__
        #define ARCH_NAME                       "arm64"
        #define ARCH_CACHE_MAGIC        "dyld_v1   arm64"
#endif


static int __attribute__((noinline)) _shared_region_check_np(uint64_t* start_address)
{
        if ( gLinkContext.sharedRegionMode == ImageLoader::kUseSharedRegion ) 
                return syscall(294, start_address);
        return -1;
}


static int __attribute__((noinline)) _shared_region_map_and_slide_np(int fd, uint32_t count, const shared_file_mapping_np mappings[],
                                                                                                int codeSignatureMappingIndex, long slide, void* slideInfo, unsigned long slideInfoSize)
{
        // register code signature blob for whole dyld cache
        if ( codeSignatureMappingIndex != -1 ) {
                fsignatures_t siginfo;
                siginfo.fs_file_start = 0;  // cache always starts at beginning of file
                siginfo.fs_blob_start = (void*)mappings[codeSignatureMappingIndex].sfm_file_offset;
                siginfo.fs_blob_size  = mappings[codeSignatureMappingIndex].sfm_size;
                int result = fcntl(fd, F_ADDFILESIGS, &siginfo);
                // <rdar://problem/12891874> don't warn in chrooted case because mapping syscall is about to fail too
                if ( (result == -1) && gLinkContext.verboseMapping )
                        dyld::log("dyld: code signature registration for shared cache failed with errno=%d\n", errno);
        }

        if ( gLinkContext.sharedRegionMode == ImageLoader::kUseSharedRegion ) {
                return syscall(438, fd, count, mappings, slide, slideInfo, slideInfoSize);
        }

        // remove the shared region sub-map
        vm_deallocate(mach_task_self(), (vm_address_t)SHARED_REGION_BASE, SHARED_REGION_SIZE);
        
        // notify gdb or other lurkers that this process is no longer using the shared region
        dyld::gProcessInfo->processDetachedFromSharedRegion = true;

        // map cache just for this process with mmap()
        const shared_file_mapping_np* const start = mappings;
        const shared_file_mapping_np* const end = &mappings[count];
        for (const shared_file_mapping_np* p = start; p < end; ++p ) {
                void* mmapAddress = (void*)(uintptr_t)(p->sfm_address);
                size_t size = p->sfm_size;
                //dyld::log("dyld: mapping address %p with size 0x%08lX\n", mmapAddress, size);
                int protection = 0;
                if ( p->sfm_init_prot & VM_PROT_EXECUTE )
                        protection   |= PROT_EXEC;
                if ( p->sfm_init_prot & VM_PROT_READ )
                        protection   |= PROT_READ;
                if ( p->sfm_init_prot & VM_PROT_WRITE )
                        protection   |= PROT_WRITE;
                off_t offset = p->sfm_file_offset;
                if ( mmap(mmapAddress, size, protection, MAP_FIXED | MAP_PRIVATE, fd, offset) != mmapAddress ) {
                        // failed to map some chunk of this shared cache file
                        // clear shared region
                        vm_deallocate(mach_task_self(), (vm_address_t)SHARED_REGION_BASE, SHARED_REGION_SIZE);
                        // go back to not using shared region at all
                        gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
                        if ( gLinkContext.verboseMapping ) {
                                dyld::log("dyld: shared cached region cannot be mapped at address %p with size 0x%08lX\n",
                                                        mmapAddress, size);
                        }
                        // return failure
                        return -1;
                }
        }

        // update all __DATA pages with slide info
        if ( slide != 0 ) {
                const uintptr_t dataPagesStart = mappings[1].sfm_address;
                const dyld_cache_slide_info* slideInfoHeader = (dyld_cache_slide_info*)slideInfo;
                const uint16_t* toc = (uint16_t*)((long)(slideInfoHeader) + slideInfoHeader->toc_offset);
                const uint8_t* entries = (uint8_t*)((long)(slideInfoHeader) + slideInfoHeader->entries_offset);
                for(uint32_t i=0; i < slideInfoHeader->toc_count; ++i) {
                        const uint8_t* entry = &entries[toc[i]*slideInfoHeader->entries_size];
                        const uint8_t* page = (uint8_t*)(long)(dataPagesStart + (4096*i));
                        //dyld::log("page=%p toc[%d]=%d entries=%p\n", page, i, toc[i], entry);
                        for(int j=0; j < 128; ++j) {
                                uint8_t b = entry[j];
                                //dyld::log("    entry[%d] = 0x%02X\n", j, b);
                                if ( b != 0 ) {
                                        for(int k=0; k < 8; ++k) {
                                                if ( b & (1<<k) ) {
                                                        uintptr_t* p = (uintptr_t*)(page + j*8*4 + k*4);
                                                        uintptr_t value = *p;
                                                        //dyld::log("        *%p was 0x%lX will be 0x%lX\n", p, value, value+sSharedCacheSlide);
                                                        *p = value + slide;
                                                }
                                        }
                                }
                        }
                }
        }

        // succesfully mapped shared cache for just this process
        gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
        
        return 0;
}


const void*     imMemorySharedCacheHeader()
{
        return sSharedCache;
}

const char* getStandardSharedCacheFilePath()
{
#if __IPHONE_OS_VERSION_MIN_REQUIRED
        return IPHONE_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME;
#else
  #if __x86_64__
        if ( sHaswell ) {
                const char* path2 = MACOSX_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME_H;
                struct stat statBuf;
                if ( my_stat(path2, &statBuf) == 0 )
                        return path2;
        }
  #endif
        return MACOSX_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME;
#endif
}

int openSharedCacheFile()
{
        char path[MAXPATHLEN];
        strlcpy(path, sSharedCacheDir, MAXPATHLEN);
        strlcat(path, "/", MAXPATHLEN);
#if __x86_64__
        if ( sHaswell ) {
                strlcat(path, DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME_H, MAXPATHLEN);
                int fd = my_open(path, O_RDONLY, 0);
                if ( fd != -1 ) {
                        if ( gLinkContext.verboseMapping ) 
                                dyld::log("dyld: Mapping%s shared cache from %s\n", (gLinkContext.sharedRegionMode == ImageLoader::kUsePrivateSharedRegion) ? " private": "", path);
                        return fd;
                }
                strlcpy(path, sSharedCacheDir, MAXPATHLEN);
        }
#endif
        strlcat(path, DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, MAXPATHLEN);
        if ( gLinkContext.verboseMapping ) 
                dyld::log("dyld: Mapping%s shared cache from %s\n", (gLinkContext.sharedRegionMode == ImageLoader::kUsePrivateSharedRegion) ? " private": "", path);
        return my_open(path, O_RDONLY, 0);
}


static void getCacheBounds(uint32_t mappingsCount, const shared_file_mapping_np mappings[], uint64_t& lowAddress, uint64_t& highAddress)
{
        lowAddress = 0;
        highAddress = 0;
        for(uint32_t i=0; i < mappingsCount; ++i) {
                if ( lowAddress == 0 ) {
                        lowAddress = mappings[i].sfm_address;
                        highAddress = mappings[i].sfm_address + mappings[i].sfm_size;
                }
                else {
                        if ( mappings[i].sfm_address < lowAddress )
                                lowAddress = mappings[i].sfm_address;
                        if ( (mappings[i].sfm_address + mappings[i].sfm_size) > highAddress )
                                highAddress = mappings[i].sfm_address + mappings[i].sfm_size;
                }
        }
}

static long pickCacheSlide(uint32_t mappingsCount, shared_file_mapping_np mappings[])
{
#if __x86_64__
        // x86_64 has a two memory regions:
        //       256MB at 0x00007FFF70000000 
        //      1024MB at 0x00007FFF80000000
        // Some old shared caches have r/w region after rx region, so all regions slide within 1GB range
        // Newer shared caches have r/w region based at 0x7FFF70000000 and r/o regions at 0x7FFF80000000, so each part has max slide
        if ( (mappingsCount >= 3) && (mappings[1].sfm_init_prot == (VM_PROT_READ|VM_PROT_WRITE)) && (mappings[1].sfm_address == 0x00007FFF70000000) ) {
                const uint64_t rwSize = mappings[1].sfm_size;
                const uint64_t rwSlop = 0x10000000ULL - rwSize;
                const uint64_t roSize = (mappings[2].sfm_address + mappings[2].sfm_size) - mappings[0].sfm_address;
                const uint64_t roSlop = 0x40000000ULL - roSize;
                const uint64_t space = (rwSlop < roSlop) ? rwSlop : roSlop;
                
                // choose new random slide
                long slide = (arc4random() % space) & (-4096);
                //dyld::log("rwSlop=0x%0llX, roSlop=0x%0llX\n", rwSlop, roSlop);
                //dyld::log("space=0x%0llX, slide=0x%0lX\n", space, slide);
                
                // update mappings
                for(uint32_t i=0; i < mappingsCount; ++i) {
                        mappings[i].sfm_address += slide;
                }
                
                return slide;
        }
        // else fall through to handle old style cache
#endif
        // get bounds of cache
        uint64_t lowAddress;
        uint64_t highAddress;
        getCacheBounds(mappingsCount, mappings, lowAddress, highAddress);
        
        // find slop space
        const uint64_t space = (SHARED_REGION_BASE + SHARED_REGION_SIZE) - highAddress;
        
        // choose new random slide
        long slide = dyld_page_trunc(arc4random() % space);
        //dyld::log("slideSpace=0x%0llX\n", space);
        //dyld::log("slide=0x%0lX\n", slide);
        
        // update mappings
        for(uint32_t i=0; i < mappingsCount; ++i) {
                mappings[i].sfm_address += slide;
        }
        
        return slide;
}

static void mapSharedCache()
{
        uint64_t cacheBaseAddress = 0;
        // quick check if a cache is already mapped into shared region
        if ( _shared_region_check_np(&cacheBaseAddress) == 0 ) {
                sSharedCache = (dyld_cache_header*)cacheBaseAddress;
                // if we don't understand the currently mapped shared cache, then ignore
#if __x86_64__
                const char* magic = (sHaswell ? ARCH_CACHE_MAGIC_H : ARCH_CACHE_MAGIC);
#else
                const char* magic = ARCH_CACHE_MAGIC;
#endif
                if ( strcmp(sSharedCache->magic, magic) != 0 ) {
                        sSharedCache = NULL;
                        if ( gLinkContext.verboseMapping ) {
                                dyld::log("dyld: existing shared cached in memory is not compatible\n");
                                return;
                        }
                }
                // check if cache file is slidable
                const dyld_cache_header* header = sSharedCache;
                if ( (header->mappingOffset >= 0x48) && (header->slideInfoSize != 0) ) {
                        // solve for slide by comparing loaded address to address of first region
                        const uint8_t* loadedAddress = (uint8_t*)sSharedCache;
                        const dyld_cache_mapping_info* const mappings = (dyld_cache_mapping_info*)(loadedAddress+header->mappingOffset);
                        const uint8_t* preferedLoadAddress = (uint8_t*)(long)(mappings[0].address);
                        sSharedCacheSlide = loadedAddress - preferedLoadAddress;
                        dyld::gProcessInfo->sharedCacheSlide = sSharedCacheSlide;
                        //dyld::log("sSharedCacheSlide=0x%08lX, loadedAddress=%p, preferedLoadAddress=%p\n", sSharedCacheSlide, loadedAddress, preferedLoadAddress);
                }
                // if cache has a uuid, copy it 
                if ( header->mappingOffset >= 0x68 ) {
                        memcpy(dyld::gProcessInfo->sharedCacheUUID, header->uuid, 16);
                }
                // verbose logging
                if ( gLinkContext.verboseMapping ) {
                        dyld::log("dyld: re-using existing shared cache mapping\n");
                }
        }
        else {
#if __i386__ || __x86_64__
                // <rdar://problem/5925940> Safe Boot should disable dyld shared cache
                // if we are in safe-boot mode and the cache was not made during this boot cycle,
                // delete the cache file
                uint32_t        safeBootValue = 0;
                size_t          safeBootValueSize = sizeof(safeBootValue);
                if ( (sysctlbyname("kern.safeboot", &safeBootValue, &safeBootValueSize, NULL, 0) == 0) && (safeBootValue != 0) ) {
                        // user booted machine in safe-boot mode
                        struct stat dyldCacheStatInfo;
                        //  Don't use custom DYLD_SHARED_CACHE_DIR if provided, use standard path
                        if ( my_stat(MACOSX_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, &dyldCacheStatInfo) == 0 ) {
                                struct timeval bootTimeValue;
                                size_t bootTimeValueSize = sizeof(bootTimeValue);
                                if ( (sysctlbyname("kern.boottime", &bootTimeValue, &bootTimeValueSize, NULL, 0) == 0) && (bootTimeValue.tv_sec != 0) ) {
                                        // if the cache file was created before this boot, then throw it away and let it rebuild itself
                                        if ( dyldCacheStatInfo.st_mtime < bootTimeValue.tv_sec ) {
                                                ::unlink(MACOSX_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME);
                                                gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
                                                return;
                                        }
                                }
                        }
                }
#endif
                // map in shared cache to shared region
                int fd = openSharedCacheFile();
                if ( fd != -1 ) {
                        uint8_t firstPages[8192];
                        if ( ::read(fd, firstPages, 8192) == 8192 ) {
                                dyld_cache_header* header = (dyld_cache_header*)firstPages;
                #if __x86_64__
                                const char* magic = (sHaswell ? ARCH_CACHE_MAGIC_H : ARCH_CACHE_MAGIC);
                #else
                                const char* magic = ARCH_CACHE_MAGIC;
                #endif
                                if ( strcmp(header->magic, magic) == 0 ) {
                                        const dyld_cache_mapping_info* const fileMappingsStart = (dyld_cache_mapping_info*)&firstPages[header->mappingOffset];
                                        const dyld_cache_mapping_info* const fileMappingsEnd = &fileMappingsStart[header->mappingCount];
                                        shared_file_mapping_np  mappings[header->mappingCount+1]; // add room for code-sig 
                                        unsigned int mappingCount = header->mappingCount;
                                        int codeSignatureMappingIndex = -1;
                                        int readWriteMappingIndex = -1;
                                        int readOnlyMappingIndex = -1;
                                        // validate that the cache file has not been truncated
                                        bool goodCache = false;
                                        struct stat stat_buf;
                                        if ( fstat(fd, &stat_buf) == 0 ) {
                                                goodCache = true;
                                                int i=0;
                                                for (const dyld_cache_mapping_info* p = fileMappingsStart; p < fileMappingsEnd; ++p, ++i) {
                                                        mappings[i].sfm_address         = p->address;
                                                        mappings[i].sfm_size            = p->size;
                                                        mappings[i].sfm_file_offset     = p->fileOffset;
                                                        mappings[i].sfm_max_prot        = p->maxProt;
                                                        mappings[i].sfm_init_prot       = p->initProt;
                                                        // rdar://problem/5694507 old update_dyld_shared_cache tool could make a cache file
                                                        // that is not page aligned, but otherwise ok.
                                                        if ( p->fileOffset+p->size > (uint64_t)(stat_buf.st_size+4095 & (-4096)) ) {
                                                                dyld::log("dyld: shared cached file is corrupt: %s" DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME "\n", sSharedCacheDir);
                                                                goodCache = false;
                                                        }
                                                        if ( (mappings[i].sfm_init_prot & (VM_PROT_READ|VM_PROT_WRITE)) == (VM_PROT_READ|VM_PROT_WRITE) ) {
                                                                readWriteMappingIndex = i;
                                                        }
                                                        if ( mappings[i].sfm_init_prot == VM_PROT_READ ) {
                                                                readOnlyMappingIndex = i;
                                                        }
                                                }
                                                // if shared cache is code signed, add a mapping for the code signature
                                                uint64_t signatureSize = header->codeSignatureSize;
                                                // zero size in header means signature runs to end-of-file
                                                if ( signatureSize == 0 )
                                                        signatureSize = stat_buf.st_size - header->codeSignatureOffset;
                                                if ( signatureSize != 0 ) {
                            int linkeditMapping = mappingCount-1;
                                                        codeSignatureMappingIndex = mappingCount++;
                                                        mappings[codeSignatureMappingIndex].sfm_address         = mappings[linkeditMapping].sfm_address + mappings[linkeditMapping].sfm_size;
#if __arm__ || __arm64__
                                                        mappings[codeSignatureMappingIndex].sfm_size            = (signatureSize+16383) & (-16384);
#else
                                                        mappings[codeSignatureMappingIndex].sfm_size            = (signatureSize+4095) & (-4096);
#endif
                                                        mappings[codeSignatureMappingIndex].sfm_file_offset     = header->codeSignatureOffset;
                                                        mappings[codeSignatureMappingIndex].sfm_max_prot        = VM_PROT_READ;
                                                        mappings[codeSignatureMappingIndex].sfm_init_prot       = VM_PROT_READ;
                                                }
                                        }
#if __MAC_OS_X_VERSION_MIN_REQUIRED     
                                        // sanity check that /usr/lib/libSystem.B.dylib stat() info matches cache
                                        if ( header->imagesCount * sizeof(dyld_cache_image_info) + header->imagesOffset < 8192 ) {
                                                bool foundLibSystem = false;
                                                if ( my_stat("/usr/lib/libSystem.B.dylib", &stat_buf) == 0 ) {
                                                        const dyld_cache_image_info* images = (dyld_cache_image_info*)&firstPages[header->imagesOffset];
                                                        const dyld_cache_image_info* const imagesEnd = &images[header->imagesCount];
                                                        for (const dyld_cache_image_info* p = images; p < imagesEnd; ++p) {
                                                                if ( ((time_t)p->modTime == stat_buf.st_mtime) && ((ino_t)p->inode == stat_buf.st_ino) ) {
                                                                        foundLibSystem = true;
                                                                        break;
                                                                }
                                                        }                                       
                                                }
                                                if ( !sSharedCacheIgnoreInodeAndTimeStamp && !foundLibSystem ) {
                                                        dyld::log("dyld: shared cached file was built against a different libSystem.dylib, ignoring cache.\n"
                                                                        "to update dyld shared cache run: 'sudo update_dyld_shared_cache' then reboot.\n");
                                                        goodCache = false;
                                                }
                                        }
#endif
#if __IPHONE_OS_VERSION_MIN_REQUIRED
                                        {
                                                uint64_t lowAddress;
                                                uint64_t highAddress;
                                                getCacheBounds(mappingCount, mappings, lowAddress, highAddress);
                                                if ( (highAddress-lowAddress) > SHARED_REGION_SIZE ) 
                                                        throw "dyld shared cache is too big to fit in shared region";
                                        }
#endif

                                        if ( goodCache && (readWriteMappingIndex == -1) ) {
                                                dyld::log("dyld: shared cached file is missing read/write mapping: %s" DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME "\n", sSharedCacheDir);
                                                goodCache = false;
                                        }
                                        if ( goodCache && (readOnlyMappingIndex == -1) ) {
                                                dyld::log("dyld: shared cached file is missing read-only mapping: %s" DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME "\n", sSharedCacheDir);
                                                goodCache = false;
                                        }
                                        if ( goodCache ) {
                                                long cacheSlide = 0;
                                                void* slideInfo = NULL;
                                                uint64_t slideInfoSize = 0;
                                                // check if shared cache contains slid info
                                                if ( header->slideInfoSize != 0 ) {
                                                        // <rdar://problem/8611968> don't slide shared cache if ASLR disabled (main executable didn't slide)
                                                        if ( sMainExecutable->isPositionIndependentExecutable() && (sMainExecutable->getSlide() == 0) )
                                                                cacheSlide = 0;
                                                        else {
                                                                // generate random slide amount
                                                                cacheSlide = pickCacheSlide(mappingCount, mappings);
                                                                slideInfo = (void*)(long)(mappings[readOnlyMappingIndex].sfm_address + (header->slideInfoOffset - mappings[readOnlyMappingIndex].sfm_file_offset));
                                                                slideInfoSize = header->slideInfoSize;
                                                                // add VM_PROT_SLIDE bit to __DATA area of cache
                                                                mappings[readWriteMappingIndex].sfm_max_prot  |= VM_PROT_SLIDE;
                                                                mappings[readWriteMappingIndex].sfm_init_prot |= VM_PROT_SLIDE;
                                                        }
                                                }
                                                if ( gLinkContext.verboseMapping ) {
                                                        dyld::log("dyld: calling _shared_region_map_and_slide_np() with regions:\n");
                                                        for (int i=0; i < mappingCount; ++i) {
                                                                dyld::log("   address=0x%08llX, size=0x%08llX, fileOffset=0x%08llX\n", mappings[i].sfm_address, mappings[i].sfm_size, mappings[i].sfm_file_offset);
                                                        }
                                                }
                                                if (_shared_region_map_and_slide_np(fd, mappingCount, mappings, codeSignatureMappingIndex, cacheSlide, slideInfo, slideInfoSize) == 0) {
                                                        // successfully mapped cache into shared region
                                                        sSharedCache = (dyld_cache_header*)mappings[0].sfm_address;
                                                        sSharedCacheSlide = cacheSlide;
                                                        dyld::gProcessInfo->sharedCacheSlide = cacheSlide;
                                                        //dyld::log("sSharedCache=%p sSharedCacheSlide=0x%08lX\n", sSharedCache, sSharedCacheSlide);
                                                        // if cache has a uuid, copy it
                                                        if ( header->mappingOffset >= 0x68 ) {
                                                                memcpy(dyld::gProcessInfo->sharedCacheUUID, header->uuid, 16);
                                                        }
                                                }
                                                else {
#if __IPHONE_OS_VERSION_MIN_REQUIRED
                                                        throw "dyld shared cache could not be mapped";
#endif
                                                        if ( gLinkContext.verboseMapping ) 
                                                                dyld::log("dyld: shared cached file could not be mapped\n");
                                                }
                                        }
                                }
                                else {
                                        if ( gLinkContext.verboseMapping ) 
                                                dyld::log("dyld: shared cached file is invalid\n");
                                }
                        }
                        else {
                                if ( gLinkContext.verboseMapping ) 
                                        dyld::log("dyld: shared cached file cannot be read\n");
                        }
                        close(fd);
                }
                else {
                        if ( gLinkContext.verboseMapping ) 
                                dyld::log("dyld: shared cached file cannot be opened\n");
                }
        }
        
        // remember if dyld loaded at same address as when cache built
        if ( sSharedCache != NULL ) {
                gLinkContext.dyldLoadedAtSameAddressNeededBySharedCache = ((uintptr_t)(sSharedCache->dyldBaseAddress) == (uintptr_t)&_mh_dylinker_header);
        }
        
        // tell gdb where the shared cache is
        if ( sSharedCache != NULL ) {
                const dyld_cache_mapping_info* const start = (dyld_cache_mapping_info*)((uint8_t*)sSharedCache + sSharedCache->mappingOffset);
                dyld_shared_cache_ranges.sharedRegionsCount = sSharedCache->mappingCount;
                // only room to tell gdb about first four regions
                if ( dyld_shared_cache_ranges.sharedRegionsCount > 4 )
                        dyld_shared_cache_ranges.sharedRegionsCount = 4;
                const dyld_cache_mapping_info* const end = &start[dyld_shared_cache_ranges.sharedRegionsCount];
                int index = 0;
                for (const dyld_cache_mapping_info* p = start; p < end; ++p, ++index ) {
                        dyld_shared_cache_ranges.ranges[index].start = p->address+sSharedCacheSlide;
                        dyld_shared_cache_ranges.ranges[index].length = p->size;
                        if ( gLinkContext.verboseMapping ) {
                                dyld::log("        0x%08llX->0x%08llX %s%s%s init=%x, max=%x\n", 
                                        p->address+sSharedCacheSlide, p->address+sSharedCacheSlide+p->size-1,
                                        ((p->initProt & VM_PROT_READ) ? "read " : ""),
                                        ((p->initProt & VM_PROT_WRITE) ? "write " : ""),
                                        ((p->initProt & VM_PROT_EXECUTE) ? "execute " : ""),  p->initProt, p->maxProt);
                        }
                #if __i386__
                        // If a non-writable and executable region is found in the R/W shared region, then this is __IMPORT segments
                        // This is an old cache.  Make writable.  dyld no longer supports turn W on and off as it binds
                        if ( (p->initProt == (VM_PROT_READ|VM_PROT_EXECUTE)) && ((p->address & 0xF0000000) == 0xA0000000) ) {
                                if ( p->size != 0 ) {
                                        vm_prot_t prot = VM_PROT_EXECUTE | PROT_READ | VM_PROT_WRITE;
                                        vm_protect(mach_task_self(), p->address, p->size, false, prot);
                                        if ( gLinkContext.verboseMapping ) {
                                                dyld::log("%18s at 0x%08llX->0x%08llX altered permissions to %c%c%c\n", "", p->address, 
                                                        p->address+p->size-1,
                                                        (prot & PROT_READ) ? 'r' : '.',  (prot & PROT_WRITE) ? 'w' : '.',  (prot & PROT_EXEC) ? 'x' : '.' );
                                        }
                                }
                        }
                #endif
                }
                if ( gLinkContext.verboseMapping ) {
                        // list the code blob
                        dyld_cache_header* header = (dyld_cache_header*)sSharedCache;
                        uint64_t signatureSize = header->codeSignatureSize;
                        // zero size in header means signature runs to end-of-file
                        if ( signatureSize == 0 ) {
                                struct stat stat_buf;
                                // FIXME: need size of cache file actually used
                                if ( my_stat(IPHONE_DYLD_SHARED_CACHE_DIR DYLD_SHARED_CACHE_BASE_NAME ARCH_NAME, &stat_buf) == 0 )
                                        signatureSize = stat_buf.st_size - header->codeSignatureOffset;
                        }
                        if ( signatureSize != 0 ) {
                                const dyld_cache_mapping_info* const last = &start[dyld_shared_cache_ranges.sharedRegionsCount-1];
                                uint64_t codeBlobStart = last->address + last->size;
                                dyld::log("        0x%08llX->0x%08llX (code signature)\n", codeBlobStart, codeBlobStart+signatureSize);
                        }
                }
#if __IPHONE_OS_VERSION_MIN_REQUIRED
                // check for file that enables dyld shared cache dylibs to be overridden
                struct stat enableStatBuf;
                // check file size to determine if correct file is in place. 
                // See <rdar://problem/13591370> Need a way to disable roots without removing /S/L/C/com.apple.dyld/enable...
                sDylibsOverrideCache = ( (my_stat(IPHONE_DYLD_SHARED_CACHE_DIR "enable-dylibs-to-override-cache", &enableStatBuf) == 0)
                                                                        && (enableStatBuf.st_size < ENABLE_DYLIBS_TO_OVERRIDE_CACHE_SIZE) );
#endif  
        }
}
#endif // #if DYLD_SHARED_CACHE_SUPPORT



// 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 )
                        (*func)(image->machHeader(), image->getSlide());
        }
}

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)
{
        dyld::log("dyld: %s\n", message);
        setErrorMessage(message);
        uintptr_t terminationFlags = 0;
        if ( !gLinkContext.startedInitializingMainExecutable ) 
                terminationFlags = 1;
        setAlImageInfosHalt(error_string, terminationFlags);
        dyld_fatal_error(error_string);
}

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 ) {
                        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)
{
        // search all images in order
        const ImageLoader* firstWeakImage = NULL;
        const ImageLoader::Symbol* firstWeakSym = 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];
                }
                if ( ! anImage->hasHiddenExports() && (!onlyInCoalesced || anImage->hasCoalescedExports()) ) {
                        *sym = anImage->findExportedSymbol(name, false, image);
                        if ( *sym != NULL ) {
                                // if weak definition found, record first one found
                                if ( ((*image)->getExportedSymbolInfo(*sym) & ImageLoader::kWeakDefinition) != 0 ) {
                                        if ( firstWeakImage == NULL ) {
                                                firstWeakImage = *image;
                                                firstWeakSym = *sym;
                                        }
                                }
                                else {
                                        // found non-weak, so immediately return with it
                                        return true;
                                }
                        }
                }
        }
        if ( firstWeakSym != NULL ) {
                // found a weak definition, but no non-weak, so return first weak found
                *sym = firstWeakSym;
                *image = firstWeakImage;
                return true;
        }
        
        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)
{
        return findExportedSymbol(name, true, sym, image);
}


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 int count = 0;
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* image = *it;
                if ( image->participatesInCoalescing() ) {
                        *images++ = *it;
                        ++count;
                }
        }
        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);
                }
                catch (const char* msg) {
                        // ignore request to abort during registration
                }
        }
}

static ImageLoader* libraryLocator(const char* libraryName, bool search, const char* origin, const ImageLoader::RPathChain* rpaths)
{
        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);
}

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                       = &registerDOFs;
        gLinkContext.clearAllDepths                     = &clearAllDepths;
        gLinkContext.printAllDepths                     = &printAllDepths;
        gLinkContext.imageCount                         = &imageCount;
        gLinkContext.setNewProgramVars          = &setNewProgramVars;
#if DYLD_SHARED_CACHE_SUPPORT
        gLinkContext.inSharedCache                      = &inSharedCache;
#endif
        gLinkContext.setErrorStrings            = &setErrorStrings;
#if SUPPORT_OLD_CRT_INITIALIZATION
        gLinkContext.setRunInitialzersOldWay= &setRunInitialzersOldWay;
#endif
        gLinkContext.findImageContainingAddress = &findImageContainingAddress;
        gLinkContext.addDynamicReference        = &addDynamicReference;
        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;
#if TARGET_IPHONE_SIMULATOR
        gLinkContext.sharedRegionMode           = ImageLoader::kDontUseSharedRegion;
#else
        gLinkContext.sharedRegionMode           = ImageLoader::kUseSharedRegion;
#endif
}



//
// Look for a special segment in the mach header. 
// Its presences means that the binary wants to have DYLD ignore
// DYLD_ environment variables.
//
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;
}


#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 DYLD_SHARED_CACHE_SUPPORT
                // 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;
        #else
                return false;
        #endif
        }

        // 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)
{
        // 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 {
                image->link(gLinkContext, forceLazysBound, false, neverUnload, loaderRPaths);
        }
        catch (const char* msg) {
                garbageCollectImages();
                throw;
        }
}


void runInitializers(ImageLoader* image)
{
        // do bottom up initialization
        ImageLoader::InitializerTimingList initializerTimes[sAllImages.size()];
        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();
                }
                
                // 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() ) {
                                OSSpinLockLock(&sDynamicReferencesLock);
                                        image->markedUsedRecursive(sDynamicReferences);
                                OSSpinLockUnlock(&sDynamicReferencesLock);
                        }
                }

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

                // collect phase: run termination routines for images not marked in-use
                __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)
{
        try {
                if ( image->isBundle() ) 
                        sBundleBeingLoaded = image;     // hack
                image->link(gLinkContext, false, true, false, loaderRPaths);
        }
        catch (const char* msg) {       
                preflight_finally(image);
                throw;
        }
        preflight_finally(image);
}

static void loadInsertedDylib(const char* path)
{
        ImageLoader* image = NULL;
        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;
                image = load(path, context);
        }
        catch (const char* msg) {
#if TARGET_IPHONE_SIMULATOR
                dyld::log("dyld: warning: could not load inserted library '%s' because %s\n", path, msg);
#else
                if ( sProcessRequiresLibraryValidation )
                        dyld::log("dyld: warning: could not load inserted library '%s' into library validated process because %s\n", path, msg);
                else
                        halt(dyld::mkstringf("could not load inserted library '%s' because %s\n", path, msg));
#endif
        }
        catch (...) {
                halt(dyld::mkstringf("could not load inserted library '%s'\n", path));
        }
}

static bool processRestricted(const macho_header* mainExecutableMH, bool* ignoreEnvVars, bool* processRequiresLibraryValidation)
{       
#if TARGET_IPHONE_SIMULATOR
        gLinkContext.codeSigningEnforced = true;
#else
    // ask kernel if code signature of program makes it restricted
    uint32_t flags;
        if ( csops(0, CS_OPS_STATUS, &flags, sizeof(flags)) != -1 ) {
                if (flags & CS_REQUIRE_LV)
                        *processRequiresLibraryValidation = true;

  #if __MAC_OS_X_VERSION_MIN_REQUIRED
                if ( flags & CS_ENFORCEMENT ) {
                        gLinkContext.codeSigningEnforced = true;
                }
                if ( ((flags & CS_RESTRICT) == CS_RESTRICT) && (csr_check(CSR_ALLOW_TASK_FOR_PID) != 0) ) {
                        sRestrictedReason = restrictedByEntitlements;
                        return true;
                }
  #else
                if ((flags & CS_ENFORCEMENT) && !(flags & CS_GET_TASK_ALLOW)) {
                        *ignoreEnvVars = true;
                }
                gLinkContext.codeSigningEnforced = true;
  #endif
        }
#endif

        // all processes with setuid or setgid bit set are restricted
    if ( issetugid() ) {
                sRestrictedReason = restrictedBySetGUid;
                return true;
        }
                
        // <rdar://problem/13158444&13245742> Respect __RESTRICT,__restrict section for root processes
        if ( hasRestrictedSegment(mainExecutableMH) ) {
                // existence of __RESTRICT/__restrict section make process restricted
                sRestrictedReason = restrictedBySegment;
                return true;
        }
    return false;
}


bool processIsRestricted()
{
        return sProcessIsRestricted;
}


// <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);
        }
}

#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 SyscallHelpers sSysCalls = {
                4,
                // 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
};

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

        // <rdar://problem/25311921> simulator does not support restricted processes
        uint32_t flags;
        if ( csops(0, CS_OPS_STATUS, &flags, sizeof(flags)) == -1 )
                return 0;
        if ( (flags & CS_RESTRICT) == CS_RESTRICT )
                return 0;
        if ( issetugid() )
                return 0;
        if ( hasRestrictedSegment(mainExecutableMH) )
                return 0;

        // verify simulator dyld file is owned by root
        struct stat sb;
        if ( fstat(fd, &sb) == -1 )
                return 0;

        // read first page of dyld file
        uint8_t firstPage[4096];
        if ( pread(fd, firstPage, 4096, 0) != 4096 )
                return 0;
        
        // 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 0;
                // re-read buffer from start of mach-o slice in fat file
                if ( pread(fd, firstPage, 4096, fileOffset) != 4096 )
                        return 0;
        }
        else if ( !isCompatibleMachO(firstPage, dyldPath) ) {
                return 0;
        }
        
        // 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 ( (sizeof(macho_header) + mh->sizeofcmds) > 4096 )
                return 0;
        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 0;
                const struct load_command* const nextCmd = (const struct load_command*)(((char*)cmd)+cmdLength);
                if ( (nextCmd > endCmds) || (nextCmd < cmd) )
                        return 0;
                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 0;
                                        if ( seg->vmsize < seg->filesize )
                                                return 0;
                                        if ( lastSeg == NULL ) {
                                                // first segment must be __TEXT and start at beginning of file/slice
                                                firstSeg = seg;
                                                if ( strcmp(seg->segname, "__TEXT") != 0 )
                                                        return 0;
                                                if ( seg->fileoff != 0 )
                                                        return 0;
                                                if ( seg->filesize < (sizeof(macho_header) + mh->sizeofcmds) )
                                                        return 0;
                                                preferredLoadAddress = seg->vmaddr;
                                        }
                                        else {
                                                // other sements must be continguous with previous segment and not executable
                                                if ( lastSeg->fileoff + lastSeg->filesize != seg->fileoff )
                                                        return 0;
                                                if ( lastSeg->vmaddr + lastSeg->vmsize != seg->vmaddr )
                                                        return 0;
                                                if ( (seg->initprot & VM_PROT_EXECUTE) != 0 )
                                                        return 0;
                                        }
                                        mappingSize += seg->vmsize;
                                        lastSeg = seg;
                                }
                                break;
                        case LC_SEGMENT_COMMAND_WRONG:
                                return 0;
                }
                cmd = nextCmd;
        }
        // last segment must be named __LINKEDIT and not writable
        if ( strcmp(lastSeg->segname, "__LINKEDIT") != 0 )
                return 0;
        if ( lastSeg->initprot & VM_PROT_WRITE )
                return 0;

        // reserve space, then mmap each segment
        vm_address_t loadAddress = 0;
        if ( ::vm_allocate(mach_task_self(), &loadAddress, mappingSize, VM_FLAGS_ANYWHERE) != 0 )
                return 0;
        cmd = cmds;
        struct linkedit_data_command* codeSigCmd = NULL;
        struct source_version_command* dyldVersionCmd = 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 0;
                                        if ( ((uintptr_t)segAddress < loadAddress) || ((uintptr_t)segAddress+seg->filesize > loadAddress+mappingSize) )
                                                return 0;
                                }
                                break;
                        case LC_CODE_SIGNATURE:
                                codeSigCmd = (struct linkedit_data_command*)cmd;
                                break;
                        case LC_SOURCE_VERSION:
                                dyldVersionCmd = (struct source_version_command*)cmd;
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }

        // must have code signature which is contained within LINKEDIT segment
        if ( codeSigCmd == NULL )
                return 0;
        if ( codeSigCmd->dataoff < lastSeg->fileoff )
                return 0;
        if ( (codeSigCmd->dataoff + codeSigCmd->datasize) > (lastSeg->fileoff + lastSeg->filesize) )
                return 0;

        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 ) {
                dyld::log("fcntl(F_ADDFILESIGS_FOR_DYLD_SIM) failed with errno=%d\n", errno);
                return 0;
        }
        close(fd);
        // file range covered by code signature must extend up to code signature itself
        if ( siginfo.fs_file_start < codeSigCmd->dataoff )
                return 0;

        // 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 0;
                        if ( registers->__eip > (firstSeg->vmaddr + firstSeg->vmsize) )
                                return 0;
                        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 0;
                        if ( registers->__rip > (firstSeg->vmaddr + firstSeg->vmsize) )
                                return 0;
                        entry = (registers->__rip + loadAddress - preferredLoadAddress);
                #endif
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }

        // 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);

        const char** appleParams = apple;
        // 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;
        return (*newDyld)(argc, argv, envp, appleParams, mainExecutableMH, (macho_header*)loadAddress,
                                         loadAddress - preferredLoadAddress, 
                                         &sSysCalls, startGlue);
}
#endif


//
// 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)
{
        uintptr_t result = 0;
        sMainExecutableMachHeader = mainExecutableMH;
#if __MAC_OS_X_VERSION_MIN_REQUIRED
        // 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 ) {
                        result = useSimulatorDyld(fd, mainExecutableMH, simDyldPath, argc, argv, envp, apple, startGlue);
                        if ( !result && (*startGlue == 0) )
                                halt("problem loading iOS simulator dyld");
                        return result;
                }
        }
#endif

        CRSetCrashLogMessage("dyld: launch started");

#if LOG_BINDINGS
        char bindingsLogPath[256];
        
        const char* shortProgName = "unknown";
        if ( argc > 0 ) {
                shortProgName = strrchr(argv[0], '/');
                if ( shortProgName == NULL )
                        shortProgName = argv[0];
                else 
                        ++shortProgName;
        }
        mysprintf(bindingsLogPath, "/tmp/bindings/%d-%s", getpid(), shortProgName);
        sBindingsLogfile = open(bindingsLogPath, O_WRONLY | O_CREAT, 0666);
        if ( sBindingsLogfile == -1 ) {
                ::mkdir("/tmp/bindings", 0777);
                sBindingsLogfile = open(bindingsLogPath, O_WRONLY | O_CREAT, 0666);
        }
        //dyld::log("open(%s) => %d, errno = %d\n", bindingsLogPath, sBindingsLogfile, errno);
#endif  
        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];
        
        bool ignoreEnvironmentVariables = false;
        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;
    sProcessIsRestricted = processRestricted(mainExecutableMH, &ignoreEnvironmentVariables, &sProcessRequiresLibraryValidation);
    if ( sProcessIsRestricted ) {
#if SUPPORT_LC_DYLD_ENVIRONMENT
                checkLoadCommandEnvironmentVariables();
#endif  
                pruneEnvironmentVariables(envp, &apple);
                // set again because envp and apple may have changed or moved
                setContext(mainExecutableMH, argc, argv, envp, apple);
        }
        else {
                if ( !ignoreEnvironmentVariables )
                        checkEnvironmentVariables(envp);
                defaultUninitializedFallbackPaths(envp);
        }
        if ( sEnv.DYLD_PRINT_OPTS )
                printOptions(argv);
        if ( sEnv.DYLD_PRINT_ENV ) 
                printEnvironmentVariables(envp);
        getHostInfo(mainExecutableMH, mainExecutableSlide);
        // 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
        sAllImages.reserve(INITIAL_IMAGE_COUNT);
        sImageRoots.reserve(16);
        sAddImageCallbacks.reserve(4);
        sRemoveImageCallbacks.reserve(4);
        sImageFilesNeedingTermination.reserve(16);
        sImageFilesNeedingDOFUnregistration.reserve(8);
        
#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
        

        try {
                // add dyld itself to UUID list
                addDyldImageToUUIDList();
                CRSetCrashLogMessage(sLoadingCrashMessage);
                // instantiate ImageLoader for main executable
                sMainExecutable = instantiateFromLoadedImage(mainExecutableMH, mainExecutableSlide, sExecPath);
                gLinkContext.mainExecutable = sMainExecutable;
                gLinkContext.processIsRestricted = sProcessIsRestricted;
                gLinkContext.processRequiresLibraryValidation = sProcessRequiresLibraryValidation;
                gLinkContext.mainExecutableCodeSigned = hasCodeSignatureLoadCommand(mainExecutableMH);

#if TARGET_IPHONE_SIMULATOR
        #if TARGET_OS_WATCH || TARGET_OS_TV
                // disable error during bring up of these simulators
        #else
                // check main executable is not too new for this OS
                {
                        if ( ! isSimulatorBinary((uint8_t*)mainExecutableMH, sExecPath) ) {
                                throwf("program was built for Mac OS X and cannot be run in simulator"); 
                        }
                        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 ) {
                                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

                // load shared cache
                checkSharedRegionDisable();
        #if DYLD_SHARED_CACHE_SUPPORT
                if ( gLinkContext.sharedRegionMode != ImageLoader::kDontUseSharedRegion )
                        mapSharedCache();
        #endif

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

                // 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;
                link(sMainExecutable, sEnv.DYLD_BIND_AT_LAUNCH, true, ImageLoader::RPathChain(NULL, NULL));
                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));
                                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();
                        }
                }

                // <rdar://problem/19315404> dyld should support interposition even without DYLD_INSERT_LIBRARIES
                for (int i=sInsertedDylibCount+1; i < sAllImages.size(); ++i) {
                        ImageLoader* image = sAllImages[i];
                        if ( image->inSharedCache() )
                                continue;
                        image->registerInterposing();
                }

                // apply interposing to initial set of images
                for(int i=0; i < sImageRoots.size(); ++i) {
                        sImageRoots[i]->applyInterposing(gLinkContext);
                }
                gLinkContext.linkingMainExecutable = false;
                
                // <rdar://problem/12186933> do weak binding only after all inserted images linked
                sMainExecutable->weakBind(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
                // find entry point for main executable
                result = (uintptr_t)sMainExecutable->getThreadPC();
                if ( result != 0 ) {
                        // main executable uses LC_MAIN, needs to return to glue in libdyld.dylib
                        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->getMain();
                        *startGlue = 0;
                }
        }
        catch(const char* message) {
                syncAllImages();
                halt(message);
        }
        catch(...) {
                dyld::log("dyld: launch failed\n");
        }

        CRSetCrashLogMessage(NULL);
        
        return result;
}



} // namespace