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

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2004-2005 Apple Computer, 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 <fcntl.h>
#include <sys/param.h>
#include <mach/mach_time.h> // mach_absolute_time()
#include <sys/types.h>
#include <sys/stat.h> 
#include <mach-o/fat.h> 
#include <mach-o/loader.h> 
#include <libkern/OSByteOrder.h> 
#include <mach/mach.h>
#include <sys/sysctl.h>

#include <vector>

#include "mach-o/dyld_gdb.h"

#include "dyld.h"
#include "ImageLoader.h"
#include "ImageLoaderMachO.h"
#include "dyldLibSystemThreadHelpers.h"


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


/* implemented in dyld_gdb.cpp */
void addImagesToAllImages(uint32_t infoCount, const dyld_image_info info[]);
void removeImageFromAllImages(const mach_header* mh);
#if OLD_GDB_DYLD_INTERFACE
void addImageForgdb(const mach_header* mh, uintptr_t slide, const char* physicalPath, const char* logicalPath);
void removeImageForgdb(const struct mach_header* mh);
#endif

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


//
// 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 {


// 
// 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_ROOT_PATH;
        const char* const *                     DYLD_INSERT_LIBRARIES;
        const char* const *                     LD_LIBRARY_PATH;                        // for unix conformance
        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;
                                                        //      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_REBASINGS                    ==> gLinkContext.verboseRebase
                                                        //      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_SLIDE_AND_PACK_DYLIBS              ==> gLinkContext.slideAndPackDylibs
                                                        //      DYLD_PRINT_WARNINGS                             ==> gLinkContext.verboseWarnings
};

// all global state
static const char*                                      sExecPath = NULL;
static const struct mach_header*        sMainExecutableMachHeader = NULL;
static cpu_type_t                                       sHostCPU;
static cpu_subtype_t                            sHostCPUsubtype;
static ImageLoader*                                     sMainExecutable = NULL;
static bool                                                     sAllImagesMightContainUnlinkedImages;    // necessary until will support dylib unloading
static std::vector<ImageLoader*>        sAllImages;
static std::vector<ImageLoader*>        sImageRoots;
static std::vector<ImageLoader*>        sImageFilesNeedingTermination;
static std::vector<ImageLoader*>        sImagesToNotifyAboutOtherImages;
static std::vector<ImageCallback>   sAddImageCallbacks;
static std::vector<ImageCallback>   sRemoveImageCallbacks;
static ImageLoader*                                     sLastImageByAddressCache;
static EnvironmentVariables                     sEnv;
static const char*                                      sFrameworkFallbackPaths[] = { "$HOME/Library/Frameworks", "/Library/Frameworks", "/Network/Library/Frameworks", "/System/Library/Frameworks", NULL };
static const char*                                      sLibraryFallbackPaths[] = { "$HOME/lib", "/usr/local/lib", "/usr/lib", NULL };
static BundleNotificationCallBack   sBundleNotifier = NULL;
static BundleLocatorCallBack            sBundleLocation = NULL;
static UndefinedHandler                         sUndefinedHandler = NULL;
ImageLoader::LinkContext                        gLinkContext;
bool                                                            gLogAPIs = false;
const struct ThreadingHelpers*          gThreadHelpers = NULL;



// 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 = open(path, O_RDONLY, 0);
}

FileOpener::~FileOpener()
{
        close(fd);
}



// Objective-C installs an addImage hook to dyld to get notified about new images
// The callback needs to be run after the image is rebased and bound, but before its initializers are called
static uint32_t imageNotification(ImageLoader* image, uint32_t startIndex)
{
        // tell all register add image handlers about this
        const uint32_t callbackCount = sAddImageCallbacks.size();
        for (uint32_t i=startIndex; i < callbackCount; ++i) {
                ImageCallback cb = sAddImageCallbacks[i];
                //fprintf(stderr, "dyld: calling add-image-callback[%d]=%p for %s\n", i, cb, image->getPath());
                (cb)(image->machHeader(), image->getSlide());
        }
        return callbackCount;
}



// notify gdb et al about these new images
static void notifyAdding(std::vector<ImageLoader*>& images)
{
        // build array
        unsigned int len = images.size();
        if ( len != 0 ) {
                dyld_image_info infos[len];
                for (unsigned int i=0; i < len; ++i) {
                        dyld_image_info* p = &infos[i];
                        ImageLoader* image = images[i];
                        p->imageLoadAddress = image->machHeader();
                        p->imageFilePath = image->getPath();
                        p->imageFileModDate = image->lastModified();
                        //fprintf(stderr, "notifying objc about %s\n", image->getPath());
                }
                
                // tell gdb
                addImagesToAllImages(len, infos);
                                
                // tell all interested images (after gdb, so you can debug anything the notification does)
                for (std::vector<ImageLoader*>::iterator it=sImagesToNotifyAboutOtherImages.begin(); it != sImagesToNotifyAboutOtherImages.end(); it++) {
                        (*it)->doNotification(dyld_image_adding, len, infos);
                }
        }
}



// 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)
{
        //fprintf(stderr, "addRootImage(%p, %s)\n", image, image->getPath());
        // add to list of roots
        sImageRoots.push_back(image);
}

// Objective-C will contain a __DATA/__image_notify section which contains pointers to a function to call
// whenever any new image is loaded.
static void addImageNeedingNotification(ImageLoader* image)
{
        sImagesToNotifyAboutOtherImages.push_back(image);
}

static void addImage(ImageLoader* image)
{
        // add to master list
        sAllImages.push_back(image);
        
        if ( sEnv.DYLD_PRINT_LIBRARIES || (sEnv.DYLD_PRINT_LIBRARIES_POST_LAUNCH && (sMainExecutable!=NULL) && sMainExecutable->isLinked()) ) {
                uint64_t offset = image->getOffsetInFatFile();
                if ( offset == 0 )
                        fprintf(stderr, "dyld: loaded: %s\n", image->getPath());
                else
                        fprintf(stderr, "dyld: loaded: %s, cpu-sub-type: %d\n", image->getPath(), image->machHeader()->cpusubtype);
        }
        
#if OLD_GDB_DYLD_INTERFACE
        // let gdb find out about this
        addImageForgdb(image->machHeader(), image->getSlide(), image->getPath(), image->getLogicalPath());
#endif
}

void removeImage(ImageLoader* image)
{
        // if in termination list, pull it out and run terminator
        for (std::vector<ImageLoader*>::iterator it=sImageFilesNeedingTermination.begin(); it != sImageFilesNeedingTermination.end(); it++) {
                if ( *it == image ) {
                        sImageFilesNeedingTermination.erase(it);
                        image->doTermination(gLinkContext);
                        break;
                }
        }
        
        // tell all register add image handlers about this
        // do this before removing image from internal data structures so that the callback can querey dyld about the image
        for (std::vector<ImageCallback>::iterator it=sRemoveImageCallbacks.begin(); it != sRemoveImageCallbacks.end(); it++) {
                (*it)(image->machHeader(), image->getSlide());
        }
        
        // tell all interested images
        for (std::vector<ImageLoader*>::iterator it=sImagesToNotifyAboutOtherImages.begin(); it != sImagesToNotifyAboutOtherImages.end(); it++) {
                dyld_image_info info;
                info.imageLoadAddress = image->machHeader();
                info.imageFilePath = image->getPath();
                info.imageFileModDate = image->lastModified();
                (*it)->doNotification(dyld_image_removing, 1, &info);
        }

        // remove from master list
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                if ( *it == image ) {
                        sAllImages.erase(it);
                        break;
                }
        }
        
        // flush find-by-address cache
        if ( sLastImageByAddressCache == image )
                sLastImageByAddressCache = NULL;

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

        // 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;
                }
        }

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

#if OLD_GDB_DYLD_INTERFACE
        // tell gdb, old way
        removeImageForgdb(image->machHeader());
        gdb_dyld_state_changed();
#endif
}


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

const char* getExecutablePath()
{
        return sExecPath;
}


void initializeMainExecutable()
{
        const int rootCount = sImageRoots.size();
        for(int i=0; i < rootCount; ++i) {
                ImageLoader* image = sImageRoots[i];
                //fprintf(stderr, "initializeMainExecutable: image = %p\n", image);
                image->runInitializers(gLinkContext);
        }
/*
        // this does not work???
        for (std::vector<ImageLoader*>::iterator it=sImageRoots.begin(); it != sImageRoots.end(); it++) {
                ImageLoader* image = *it;
                fprintf(stderr, "initializeMainExecutable: image = %p\n", image);
                // don't know why vector sometimes starts with NULL element???
                if ( image != NULL ) 
                        image->runInitializers(gLinkContext);
        }
*/
        if ( sEnv.DYLD_PRINT_STATISTICS )
                ImageLoaderMachO::printStatistics(sAllImages.size());
}

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

ImageLoader* mainExecutable()
{
        return sMainExecutable;
}


void runTerminators()
{
        const unsigned int imageCount = sImageFilesNeedingTermination.size();
        for(unsigned int i=imageCount; i > 0; --i){
                ImageLoader* image = sImageFilesNeedingTermination[i-1];
                image->doTermination(gLinkContext);
        }
        sImageFilesNeedingTermination.clear();
}


//
// Turns a colon separated list of strings
// into a NULL terminated array of string 
// pointers.
//
static const char** parseColonList(const char* list)
{
        if ( list[0] == '\0' )
                return NULL;

        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 == ':') {
                        int len = s-start;
                        char* str = new char[len+1];
                        strncpy(str, start, len);
                        str[len] = '\0';
                        start = &s[1];
                        result[index++] = str;
                }
        }
        int len = strlen(start);
        char* str = new char[len+1];
        strcpy(str, start);
        result[index++] = str;
        result[index] = NULL;
        
        return (const char**)result;
}

/*
 * Library path searching is not done for setuid programs
 * which are not run by the real user.  Futher the
 * evironment varaible for the library path is cleared so
 * that if this program executes a non-set uid program this
 * part of the evironment will not be passed along so that
 * that program also will not have it's libraries searched
 * for.
 */
 static bool riskyUser()
 {
        static bool checked = false;
        static bool risky = false;
        if ( !checked ) {
                risky = ( getuid() != 0 && (getuid() != geteuid() || getgid() != getegid()) );
                checked = true;
        }
        return risky;
 }
 
 
static bool disableIfBadUser(char* rhs)
{
        bool didDisable = false;
        if ( riskyUser() ) {
                *rhs ='\0';
                didDisable = true;
        }
        return didDisable;
}

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);
        for(int s=0,d=0; (paths[d] != NULL) && (paths[s] != NULL); ++s, ++d) {
                if ( strncmp(paths[s], prefix, prefixLen) == 0 )
                        ++s;
                paths[d] = paths[s];
        }
}

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

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

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



void processDyldEnvironmentVarible(const char* key, const char* value)
{
        if ( strcmp(key, "DYLD_FRAMEWORK_PATH") == 0 ) {
                if ( !disableIfBadUser((char*)value) )
                        sEnv.DYLD_FRAMEWORK_PATH = parseColonList(value);
        }
        else if ( strcmp(key, "DYLD_FALLBACK_FRAMEWORK_PATH") == 0 ) {
                if ( !disableIfBadUser((char*)value) )
                        sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = parseColonList(value);
        }
        else if ( strcmp(key, "DYLD_LIBRARY_PATH") == 0 ) {
                if ( !disableIfBadUser((char*)value) )
                        sEnv.DYLD_LIBRARY_PATH = parseColonList(value);
        }
        else if ( strcmp(key, "DYLD_FALLBACK_LIBRARY_PATH") == 0 ) {
                if ( !disableIfBadUser((char*)value) )
                        sEnv.DYLD_FALLBACK_LIBRARY_PATH = parseColonList(value);
        }
        else if ( (strcmp(key, "DYLD_ROOT_PATH") == 0) || (strcmp(key, "DYLD_PATHS_ROOT") == 0) ) {
                if ( !disableIfBadUser((char*)value) ) {
                        if ( strcmp(value, "/") != 0 ) {
                                sEnv.DYLD_ROOT_PATH = parseColonList(value);
                                for (int i=0; sEnv.DYLD_ROOT_PATH[i] != NULL; ++i) {
                                        if ( sEnv.DYLD_ROOT_PATH[i][0] != '/' ) {
                                                fprintf(stderr, "dyld: warning DYLD_ROOT_PATH not used because it contains a non-absolute path\n");
                                                sEnv.DYLD_ROOT_PATH = NULL;
                                                break;
                                        }
                                }
                        }
                }
        } 
        else if ( strcmp(key, "DYLD_IMAGE_SUFFIX") == 0 ) {
                if ( !disableIfBadUser((char*)value) )
                        gLinkContext.imageSuffix = value;
        }
        else if ( strcmp(key, "DYLD_INSERT_LIBRARIES") == 0 ) {
                if ( !disableIfBadUser((char*)value) )
                        sEnv.DYLD_INSERT_LIBRARIES = parseColonList(value);
        }
        else if ( strcmp(key, "DYLD_DEBUG_TRACE") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_DEBUG_TRACE not supported\n");
        }
        else if ( strcmp(key, "DYLD_ERROR_PRINT") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_ERROR_PRINT not supported\n");
        }
        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_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_TRACE") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_TRACE not supported\n");
        }
        else if ( strcmp(key, "DYLD_EBADEXEC_ONLY") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_EBADEXEC_ONLY not supported\n");
        }
        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_DEAD_LOCK_HANG") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_DEAD_LOCK_HANG not supported\n");
        }
        else if ( strcmp(key, "DYLD_ABORT_MULTIPLE_INITS") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_ABORT_MULTIPLE_INITS not supported\n");
        }
        else if ( strcmp(key, "DYLD_NEW_LOCAL_SHARED_REGIONS") == 0 ) {
                gLinkContext.sharedRegionMode = ImageLoader::kUsePrivateSharedRegion;
        }
        else if ( strcmp(key, "DYLD_SLIDE_AND_PACK_DYLIBS") == 0 ) {
                gLinkContext.slideAndPackDylibs = true;
        }
        else if ( strcmp(key, "DYLD_NO_FIX_PREBINDING") == 0 ) {
                // since the new dyld never runs fix_prebinding, no need to warn if someone does not want it run
                //fprintf(stderr, "dyld: warning DYLD_NO_FIX_PREBINDING not supported\n");
        }
        else if ( strcmp(key, "DYLD_PREBIND_DEBUG") == 0 ) {
                gLinkContext.verbosePrebinding = true;
        }
        else if ( strcmp(key, "DYLD_HINTS_DEBUG") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_HINTS_DEBUG not supported\n");
        }
        else if ( strcmp(key, "DYLD_SAMPLE_DEBUG") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_SAMPLE_DEBUG not supported\n");
        }
        else if ( strcmp(key, "DYLD_EXECUTABLE_PATH_DEBUG") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_EXECUTABLE_PATH_DEBUG not supported\n");
        }
        else if ( strcmp(key, "DYLD_TWO_LEVEL_DEBUG") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_TWO_LEVEL_DEBUG not supported\n");
        }
        else if ( strcmp(key, "DYLD_LAZY_INITIALIZERS") == 0 ) {
                fprintf(stderr, "dyld: warning DYLD_LAZY_INITIALIZERS not supported\n");
        }
        else if ( strcmp(key, "DYLD_PRINT_INITIALIZERS") == 0 ) {
                gLinkContext.verboseInit = 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_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_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 {
                        fprintf(stderr, "dyld: warning unknown option to DYLD_SHARED_REGION.  Valid options are: use, private, avoid\n");
                }
        }
        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 {
                        fprintf(stderr, "dyld: warning unknown option to DYLD_IGNORE_PREBINDING.  Valid options are: all, app, nonsplit\n");
                }
        }
        else {
                fprintf(stderr, "dyld: warning, unknown environment variable: %s\n", key);
        }
}

static void checkEnvironmentVariables(const char* envp[], bool ignoreEnviron)
{
        const char* home = NULL;
        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) && !ignoreEnviron ) {
                                const char* value = &equals[1];
                                const int keyLen = equals-keyEqualsValue;
                                char key[keyLen+1];
                                strncpy(key, keyEqualsValue, keyLen);
                                key[keyLen] = '\0';
                                processDyldEnvironmentVarible(key, value);
                        }
                }
            else if ( strncmp(keyEqualsValue, "HOME=", 5) == 0 ) {
                        home = &keyEqualsValue[5];
                }
                else if ( strncmp(keyEqualsValue, "LD_LIBRARY_PATH=", 16) == 0 ) {
                        const char* path = &keyEqualsValue[16];
                        if ( !disableIfBadUser((char*)path) )
                                sEnv.LD_LIBRARY_PATH = parseColonList(path);
                }
        }
        
        // default value for DYLD_FALLBACK_FRAMEWORK_PATH, if not set in environment
        if ( sEnv.DYLD_FALLBACK_FRAMEWORK_PATH == NULL ) {
                const char** paths = sFrameworkFallbackPaths;
                if ( home != NULL ) {
                        if ( riskyUser() )
                                removePathWithPrefix(paths, "$HOME");
                        else
                                paths_expand_roots(paths, "$HOME", home);
                }
                sEnv.DYLD_FALLBACK_FRAMEWORK_PATH = paths;
        }

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


static void getHostInfo()
{
#if 0
        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);
        mach_port_deallocate(mach_task_self(), hostPort);
        if ( result != KERN_SUCCESS )
                throw "host_info() failed";
        
        sHostCPU                = info.cpu_type;
        sHostCPUsubtype = info.cpu_subtype;
#endif

        size_t valSize = sizeof(sHostCPU);
        if (sysctlbyname ("hw.cputype", &sHostCPU, &valSize, NULL, 0) != 0) 
                throw "sysctlbyname(hw.cputype) failed";
        valSize = sizeof(sHostCPUsubtype);
        if (sysctlbyname ("hw.cpusubtype", &sHostCPUsubtype, &valSize, NULL, 0) != 0) 
                throw "sysctlbyname(hw.cpusubtype) failed";
}

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

uint32_t getImageCount()
{
        if ( sAllImagesMightContainUnlinkedImages ) {
                uint32_t count = 0;
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                        if ( (*it)->isLinked() )
                                ++count;
                }
                return count;
        }
        else {
                return sAllImages.size();
        }
}

ImageLoader* getIndexedImage(unsigned int index)
{
        if ( sAllImagesMightContainUnlinkedImages ) {
                uint32_t count = 0;
                for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                        if ( (*it)->isLinked() ) {
                                if ( index == count )
                                        return *it;
                                ++count;
                        }
                }
        }
        else {
                if ( index < sAllImages.size() )
                        return sAllImages[index];
        }
        return NULL;
}

ImageLoader* findImageByMachHeader(const struct mach_header* target)
{
        const unsigned int imageCount = sAllImages.size();
        for(unsigned int i=0; i < imageCount; ++i) {
                ImageLoader* anImage = sAllImages[i];
                if ( anImage->machHeader() == target )
                        return anImage;
        }
        return NULL;
}


ImageLoader* findImageContainingAddress(const void* addr)
{
#if FIND_STATS  
        static int cacheHit = 0; 
        static int cacheMiss = 0; 
        static int cacheNotMacho = 0; 
        if ( ((cacheHit+cacheMiss+cacheNotMacho) % 100) == 0 )
                fprintf(stderr, "findImageContainingAddress(): cache hit = %d, miss = %d, unknown = %d\n", cacheHit, cacheMiss, cacheNotMacho);
#endif
        // first look in image where last address was found rdar://problem/3685517
        if ( (sLastImageByAddressCache != NULL) && sLastImageByAddressCache->containsAddress(addr) ) {
#if FIND_STATS  
                ++cacheHit;
#endif
                return sLastImageByAddressCache;
        }
        // do exhastive search 
        // todo: consider maintaining a list sorted by address ranges and do a binary search on that
        const unsigned int imageCount = sAllImages.size();
        for(unsigned int i=0; i < imageCount; ++i) {
                ImageLoader* anImage = sAllImages[i];
                if ( anImage->containsAddress(addr) ) {
                        sLastImageByAddressCache = anImage;
#if FIND_STATS  
                ++cacheMiss;
#endif
                        return anImage;
                }
        }
#if FIND_STATS  
                ++cacheNotMacho;
#endif
        return NULL;
}

ImageLoader* findImageContainingAddressThreadSafe(const void* addr)
{
        // do exhastive search 
        // todo: consider maintaining a list sorted by address ranges and do a binary search on that
        const unsigned int imageCount = sAllImages.size();
        for(unsigned int i=0; i < imageCount; ++i) {
                ImageLoader* anImage = sAllImages[i];
                if ( anImage->containsAddress(addr) ) {
                        return anImage;
                }
        }
        return NULL;
}


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

ImageLoader* findLoadedImage(const struct stat& stat_buf)
{
        const unsigned int imageCount = sAllImages.size();
        for(unsigned int 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 int 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;
                                int 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;
}



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.
//


//       
//      32-bit PowerPC sub-type lists
//
const int kPPC_RowCount = 4;
static const cpu_subtype_t kPPC32[kPPC_RowCount][6] = { 
        // G5 can run any code
        {  CPU_SUBTYPE_POWERPC_970, CPU_SUBTYPE_POWERPC_7450,  CPU_SUBTYPE_POWERPC_7400, CPU_SUBTYPE_POWERPC_750, CPU_SUBTYPE_POWERPC_ALL, CPU_SUBTYPE_END_OF_LIST },
        
        // G4 can run all but G5 code
        {  CPU_SUBTYPE_POWERPC_7450,  CPU_SUBTYPE_POWERPC_7400,  CPU_SUBTYPE_POWERPC_750, CPU_SUBTYPE_POWERPC_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },
        {  CPU_SUBTYPE_POWERPC_7400,  CPU_SUBTYPE_POWERPC_7450,  CPU_SUBTYPE_POWERPC_750, CPU_SUBTYPE_POWERPC_ALL, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST },

        // G3 cannot run G4 or G5 code
        { CPU_SUBTYPE_POWERPC_750,  CPU_SUBTYPE_POWERPC_ALL, CPU_SUBTYPE_END_OF_LIST,  CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST, CPU_SUBTYPE_END_OF_LIST }
};


//       
//      64-bit PowerPC sub-type lists
//
const int kPPC64_RowCount = 1;
static const cpu_subtype_t kPPC64[kPPC64_RowCount][3] = { 
        // G5 can run any 64-bit code
        {  CPU_SUBTYPE_POWERPC_970, CPU_SUBTYPE_POWERPC_ALL, CPU_SUBTYPE_END_OF_LIST },
};



//       
//      32-bit x86 sub-type lists
//
//      TO-DO



// 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) {
                case CPU_TYPE_POWERPC:
                        for (int i=0; i < kPPC_RowCount ; ++i) {
                                if ( kPPC32[i][0] == subtype )
                                        return kPPC32[i];
                        }
                        break;
                case CPU_TYPE_POWERPC64:
                        for (int i=0; i < kPPC64_RowCount ; ++i) {
                                if ( kPPC64[i][0] == subtype )
                                        return kPPC64[i];
                        }
                        break;
                case CPU_TYPE_I386:
                        // To do 
                        break;
        }
        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] == 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) {
                                case CPU_TYPE_POWERPC:
                                case CPU_TYPE_POWERPC64:
                                        if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_POWERPC_ALL ) {
                                                *offset = OSSwapBigToHostInt32(archs[i].offset);
                                                *len = OSSwapBigToHostInt32(archs[i].size);
                                                return true;
                                        }
                                        break;
                                case CPU_TYPE_I386:
                                        if ( (cpu_subtype_t)OSSwapBigToHostInt32(archs[i].cpusubtype) == CPU_SUBTYPE_I386_ALL ) {
                                                *offset = OSSwapBigToHostInt32(archs[i].offset);
                                                *len = OSSwapBigToHostInt32(archs[i].size);
                                                return true;
                                        }
                                        break;
                        }
                }
        }
        return false;
}


//
// 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)
{
        // 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);
}



//
// This is used to validate if a non-fat (aka thin or raw) mach-o file can be used
// on the current processor.  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
//
//
bool isCompatibleMachO(const uint8_t* firstPage)
{
        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
                                        throw "incompatible cpu-subtype";
                                }
                                // unknown cpu sub-type, but if exact match for current subtype then ok to use
                                if ( mh->cpusubtype == sHostCPUsubtype ) 
                                        return true;
                        }
                        
                        // cpu unknown, so don't know if subtype is compatible
                        // only load _ALL variant
                        switch (mh->cputype) {
                                case CPU_TYPE_POWERPC:
                                case CPU_TYPE_POWERPC64:
                                        if ( mh->cpusubtype == CPU_SUBTYPE_POWERPC_ALL ) 
                                                return true;
                                        break;
                                case CPU_TYPE_I386:
                                        if ( mh->cpusubtype == CPU_SUBTYPE_I386_ALL ) 
                                                return true;
                                        break;                                  
                        }
                }
        }
        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 struct mach_header* mh, const char* path)
{
        // try mach-o loader
        if ( isCompatibleMachO((const uint8_t*)mh) ) {
                ImageLoader* image = new ImageLoaderMachO(path, mh, 0, gLinkContext);
                addImage(image);
                return image;
        }
        
        return NULL;
}




// map in file and instantiate an ImageLoader
static ImageLoader* loadPhase6(int fd, struct stat& stat_buf, const char* path, const LoadContext& context)
{
        //fprintf(stderr, "%s(%s)\n", __func__ , path);
        uint64_t fileOffset = 0;
        uint64_t fileLength = stat_buf.st_size;
#if __ppc64__
        if ( *((uint32_t*)((char*)(&stat_buf)+0x60)) == 0xFEFEFEFE )
                fileLength = *((uint64_t*)((char*)(&stat_buf)+0x30));   // HACK work around for kernel stat bug rdar://problem/3845883
#endif

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

        // min file is 4K
        if ( fileLength < 4096 ) {
                throw "file to short";
        }
        
        uint8_t firstPage[4096];
        pread(fd, firstPage, 4096,0);
        
        // 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) ) {
                        pread(fd, firstPage, 4096, fileOffset);
                }
                else {
                        throw "no matching architecture in universal wrapper";
                }
        }
        
        // try mach-o loader
        if ( isCompatibleMachO(firstPage) ) {
                char realFilePath[PATH_MAX];
                if ( gLinkContext.slideAndPackDylibs ) {
                        // when prebinding, we always want to track the real path of images
                        if ( realpath(path, realFilePath) != NULL )
                                path = realFilePath;
                }

                // instantiate an image
                ImageLoader* image = new ImageLoaderMachO(path, fd, firstPage, fileOffset, fileLength, stat_buf, gLinkContext);
                
                // 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 ) {
                                                //fprintf(stderr, "duplicate(%s) => %p\n", installPath, anImage);
                                                delete 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";

                // 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...
        
        
        // 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]);
        }
}


// try to open file
static ImageLoader* loadPhase5open(const char* path, const LoadContext& context, std::vector<const char*>* exceptions)
{
        //fprintf(stdout, "%s(%s)\n", __func__, path);
        ImageLoader* image = NULL;

        // open file (automagically closed when this function exits)
        FileOpener file(path);
        
        //fprintf(stderr, "open(%s) => %d\n", path, file.getFileDescriptor() );
        
        if ( file.getFileDescriptor() == -1 )
                return NULL;
                
        struct stat stat_buf;
#if __ppc64__
        memset(&stat_buf, 254, sizeof(struct stat));     // hack until rdar://problem/3845883 is fixed
#endif
        if ( fstat(file.getFileDescriptor(), &stat_buf) == -1)
                throw "stat error";
        
        // in case image was renamed or found via symlinks, check for inode match
        image = findLoadedImage(stat_buf);
        if ( image != NULL )
                return image;
        
        // needed to implement NSADDIMAGE_OPTION_RETURN_ONLY_IF_LOADED
        if ( context.dontLoad )
                return NULL;
        
        try {
                return loadPhase6(file.getFileDescriptor(), stat_buf, path, context);
        }
        catch (const char* msg) {
                char* newMsg = new char[strlen(msg) + strlen(path) + 8];
                sprintf(newMsg, "%s: %s", path, msg);
                exceptions->push_back(newMsg);
                return NULL;
        }
}

// look for path match with existing loaded images
static ImageLoader* loadPhase5check(const char* path, const LoadContext& context)
{
        //fprintf(stderr, "%s(%s)\n", __func__ , path);
        // search path against load-path and install-path of all already loaded images
        uint32_t hash = ImageLoader::hash(path);
        for (std::vector<ImageLoader*>::iterator it=sAllImages.begin(); it != sAllImages.end(); it++) {
                ImageLoader* anImage = *it;
                // check has first to cut down on strcmp calls
                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;
                                }
                        }
                }
        }
        
        //fprintf(stderr, "check(%s) => NULL\n", path);
        return NULL;
}


// open or check existing
static ImageLoader* loadPhase5(const char* path, const LoadContext& context, std::vector<const char*>* exceptions)
{
        //fprintf(stderr, "%s(%s)\n", __func__ , path);
        if ( exceptions != NULL ) 
                return loadPhase5open(path, context, exceptions);
        else
                return loadPhase5check(path, context);
}

// try with and without image suffix
static ImageLoader* loadPhase4(const char* path, const LoadContext& context, std::vector<const char*>* exceptions)
{
        //fprintf(stderr, "%s(%s)\n", __func__ , path);
        ImageLoader* image = NULL;
        if (  gLinkContext.imageSuffix != NULL ) {
                char pathWithSuffix[strlen(path)+strlen( gLinkContext.imageSuffix)+2];
                ImageLoader::addSuffix(path,  gLinkContext.imageSuffix, pathWithSuffix);
                image = loadPhase5(pathWithSuffix, context, exceptions);
        }
        if ( image == NULL )
                image = loadPhase5(path, context, exceptions);
        return image;
}


// expand @ variables
static ImageLoader* loadPhase3(const char* path, const LoadContext& context, std::vector<const char*>* exceptions)
{
        //fprintf(stderr, "%s(%s)\n", __func__ , path);
        ImageLoader* image = NULL;
        if ( strncmp(path, "@executable_path/", 17) == 0 ) {
                // 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, 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, context, exceptions);
                        if ( image != NULL ) 
                                return image;
                }
        }
        else if ( (strncmp(path, "@loader_path/", 13) == 0) && (context.origin != NULL) ) {
                // 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, 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, context, exceptions);
                        if ( image != NULL ) 
                                return image;
                }
        }
        
        return loadPhase4(path, context, exceptions);
}


// try search paths
static ImageLoader* loadPhase2(const char* path, const LoadContext& context, 
                                                           const char* const frameworkPaths[], const char* const libraryPaths[], 
                                                           std::vector<const char*>* exceptions)
{
        //fprintf(stderr, "%s(%s)\n", __func__ , path);
        ImageLoader* image = NULL;
        const char* frameworkPartialPath = getFrameworkPartialPath(path);
        if ( frameworkPaths != NULL ) {
                if ( frameworkPartialPath != NULL ) {
                        const int 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);
                                //fprintf(stderr, "dyld: fallback framework path used: %s() -> loadPhase4(\"%s\", ...)\n", __func__, npath);
                                image = loadPhase4(npath, context, exceptions);
                                if ( image != NULL )
                                        return image;
                        }
                }
        }
        if ( libraryPaths != NULL ) {
                const char* libraryLeafName = getLibraryLeafName(path);
                const int 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);
                        //fprintf(stderr, "dyld: fallback library path used: %s() -> loadPhase4(\"%s\", ...)\n", __func__, libpath);
                        image = loadPhase4(libpath, context, exceptions);
                        if ( image != NULL )
                                return image;
                }
        }
        return NULL;
}

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

        // handle LD_LIBRARY_PATH environment variables that force searching
        if ( context.useLdLibraryPath && (sEnv.LD_LIBRARY_PATH != NULL) ) {
                image = loadPhase2(path, 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, context, sEnv.DYLD_FRAMEWORK_PATH, sEnv.DYLD_LIBRARY_PATH, exceptions);
                if ( image != NULL )
                        return image;
        }
        
        // try raw path
        image = loadPhase3(path, context, exceptions);
        if ( image != NULL )
                return image;
        
        // try fallback paths during second time (will open file)
        if ( (exceptions != NULL) && ((sEnv.DYLD_FALLBACK_FRAMEWORK_PATH != NULL) || (sEnv.DYLD_FALLBACK_LIBRARY_PATH != NULL)) ) {
                image = loadPhase2(path, context, sEnv.DYLD_FALLBACK_FRAMEWORK_PATH, sEnv.DYLD_FALLBACK_LIBRARY_PATH, exceptions);
                if ( image != NULL )
                        return image;
        }
                
        return NULL;
}

// try root substitutions
static ImageLoader* loadPhase0(const char* path, const LoadContext& context, std::vector<const char*>* exceptions)
{
        //fprintf(stderr, "%s(%s)\n", __func__ , path);
        
        // handle DYLD_ROOT_PATH which forces absolute paths to use a new root
        if ( (sEnv.DYLD_ROOT_PATH != NULL) && (path[0] == '/') ) {
                for(const char* const* rootPath = sEnv.DYLD_ROOT_PATH ; *rootPath != NULL; ++rootPath) {
                        char newPath[strlen(*rootPath) + strlen(path)+2];
                        strcpy(newPath, *rootPath);
                        strcat(newPath, path);
                        ImageLoader* image = loadPhase1(newPath, context, exceptions);
                        if ( image != NULL )
                                return image;
                }
        }

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

//
// Given all the DYLD_ environment variables, the general case for loading libraries
// is that any given path expands into a list of possible locations to load.  We
// also must take care to ensure two copies of the "same" library are never loaded.
//
// The algorithm used here is that there is a separate function for each "phase" of the
// path expansion.  Each phase function calls the next phase with each possible expansion
// of that phase.  The result is the last phase is called with all possible paths.  
//
// To catch duplicates the algorithm is run twice.  The first time, the last phase checks
// the path against all loaded images.  The second time, the last phase calls open() on 
// the path.  Either time, if an image is found, the phases all unwind without checking
// for other paths.
//
ImageLoader* load(const char* path, const LoadContext& context)
{
        //fprintf(stderr, "%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, context, NULL);
        if ( image != NULL )
                return image;
        
        // try all path permutations and try open() until first sucesss
        std::vector<const char*> exceptions;
        image = loadPhase0(path, context, &exceptions);
        if ( image != NULL )
                return image;
        else if ( context.dontLoad )
                return NULL;
        else if ( exceptions.size() == 0 )
                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 (unsigned int i=0; i < exceptions.size(); ++i) 
                        allsizes += (strlen(exceptions[i]) + strlen(delim));
                char* fullMsg = new char[allsizes];
                strcpy(fullMsg, msgStart);
                for (unsigned int i=0; i < exceptions.size(); ++i) {
                        strcat(fullMsg, delim);
                        strcat(fullMsg, exceptions[i]);
                }
                throw (const char*)fullMsg;
        }
}




// create when NSLinkModule is called for a second time on a bundle
ImageLoader* cloneImage(ImageLoader* image)
{
        const uint64_t offsetInFat = image->getOffsetInFatFile();

        // open file (automagically closed when this function exits)
        FileOpener file(image->getPath());
        
        struct stat stat_buf;
#if __ppc64__
        memset(&stat_buf, 254, sizeof(struct stat));     // hack until rdar://problem/3845883 is fixed
#endif
        if ( fstat(file.getFileDescriptor(), &stat_buf) == -1)
                throw "stat error";
        
        // read first page of file
        uint8_t firstPage[4096];
        pread(file.getFileDescriptor(), firstPage, 4096, offsetInFat);
        
        // fat length is only used for sanity checking, since this image was already loaded once, just use upper bound
        uint64_t lenInFat = stat_buf.st_size - offsetInFat;
        
        // try mach-o loader
        if ( isCompatibleMachO(firstPage) ) {
                ImageLoader* clone = new ImageLoaderMachO(image->getPath(), file.getFileDescriptor(), firstPage, offsetInFat, lenInFat, stat_buf, 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(clone);
                return clone;
        }
        
        // try other file formats...
        throw "can't clone image";
}


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 mach-o each loader
        if ( isCompatibleMachO(mem) ) {
                ImageLoader* image = new ImageLoaderMachO(moduleName, (mach_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...
        
        // 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, starting at roots
        const int rootCount = sImageRoots.size();
        for(int i=0; i < rootCount; ++i) {
                ImageLoader* image = sImageRoots[i];
                image->runNotification(gLinkContext, sAddImageCallbacks.size());
        }
        
//      for (std::vector<ImageLoader*>::iterator it=sImageRoots.begin(); it != sImageRoots.end(); it++) {
//              ImageLoader* image = *it;
//              image->runNotification(gLinkContext, sAddImageCallbacks.size());
//      }
}

void registerRemoveCallback(ImageCallback func)
{
        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
        strncpy(error_string, message, sizeof(error_string)-1);
        error_string[sizeof(error_string)-1] = '\0';
}

const char* getErrorMessage()
{
        return error_string;
}

void  halt(const char* message)
{
        fprintf(stderr, "dyld: %s\n", message);
        setErrorMessage(message);
        strncpy(error_string, message, sizeof(error_string)-1);
        error_string[sizeof(error_string)-1] = '\0';
        
#if __ppc__ || __ppc64__
        __asm__  ("trap");
#elif __i386__
        __asm__  ("int3");
#else
        #error unknown architecture
#endif
        abort();        // needed to suppress warning that noreturn function returns
}


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 ( gThreadHelpers != NULL ) 
                (*gThreadHelpers->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::findImageContainingAddressThreadSafe(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 )
                        throw "image not found for lazy pointer";
                result = target->doBindLazySymbol(lazyPointer, gLinkContext);
        }
        catch (const char* message) {
                fprintf(stderr, "dyld: lazy symbol binding failed: %s\n", message);
                halt(message);
        }
        // release read-lock on dyld's data structures
#if 0
        if ( gThreadHelpers != NULL ) 
                (*gThreadHelpers->unlockForReading)();
#endif
        // return target address to glue which jumps to it with real parameters restored
        return result;
}


// SPI used by ZeroLink to lazy load bundles
void registerZeroLinkHandlers(BundleNotificationCallBack notify, BundleLocatorCallBack locate)
{
        sBundleNotifier = notify;
        sBundleLocation = locate;
}

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, ImageLoader** image)
{
        // try ZeroLink short cut to finding bundle which exports this symbol
        if ( sBundleLocation != NULL ) {
                ImageLoader* zlImage = (*sBundleLocation)(name);
                if ( zlImage == ((ImageLoader*)(-1)) ) {
                        // -1 is magic value that request symbol is in a bundle not yet linked into process
                        // try calling handler to link in that symbol
                        undefinedHandler(name);
                        // call locator again
                        zlImage = (*sBundleLocation)(name);
                }
                // if still not found, then ZeroLink has no idea where to find it
                if ( zlImage == ((ImageLoader*)(-1)) ) 
                        return false;
                if ( zlImage != NULL ) {
                        // ZeroLink cache knows where the symbol is
                        *sym = zlImage->findExportedSymbol(name, NULL, false, image);
                        if ( *sym != NULL ) {
                                *image = zlImage;
                                return true;
                        }
                }
                else {
                        // ZeroLink says it is in some bundle already loaded, but not linked, walk them all
                        const unsigned int imageCount = sAllImages.size();
                        for(unsigned int i=0; i < imageCount; ++i){
                                ImageLoader* anImage = sAllImages[i];
                                if ( anImage->isBundle() && !anImage->hasHiddenExports() ) {
                                        //fprintf(stderr, "dyld: search for %s in %s\n", name, anImage->getPath());
                                        *sym = anImage->findExportedSymbol(name, NULL, false, image);
                                        if ( *sym != NULL ) {
                                                return true;
                                        }
                                }
                        }
                }
        }

        // search all images in order
        ImageLoader* firstWeakImage = NULL;
        const ImageLoader::Symbol* firstWeakSym = NULL;
        const unsigned int imageCount = sAllImages.size();
        for(unsigned int i=0; i < imageCount; ++i){
                ImageLoader* anImage = sAllImages[i];
                if ( ! anImage->hasHiddenExports() && (!onlyInCoalesced || anImage->hasCoalescedExports()) ) {
                        *sym = anImage->findExportedSymbol(name, NULL, 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, ImageLoader** image)
{
        return findExportedSymbol(name, false, sym, image);
}

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


bool flatFindExportedSymbolWithHint(const char* name, const char* librarySubstring, const ImageLoader::Symbol** sym, ImageLoader** image)
{
        // search all images in order
        const unsigned int imageCount = sAllImages.size();
        for(unsigned int 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, NULL, false, image);
                        if ( *sym != NULL ) {
                                return true;
                        }
                }
        }
        return false;
}

static void getMappedRegions(ImageLoader::RegionsVector& regions)
{
        const unsigned int imageCount = sAllImages.size();
        for(unsigned int i=0; i < imageCount; ++i){
                ImageLoader* anImage = sAllImages[i];
                anImage->addMappedRegions(regions);
        }
}


static ImageLoader* libraryLocator(const char* libraryName, bool search, const char* origin, const char* rpath[])
{
        dyld::LoadContext context;
        context.useSearchPaths          = search;
        context.useLdLibraryPath        = false;
        context.dontLoad                        = false;
        context.mustBeBundle            = false;
        context.mustBeDylib                     = true;
        context.matchByInstallName      = false;
        context.origin                          = origin;
        context.rpath                           = rpath;
        return load(libraryName, context);
}

        
static void setContext(int argc, const char* argv[], const char* envp[], const char* apple[])
{
        gLinkContext.loadLibrary                        = &libraryLocator;
        gLinkContext.imageNotification          = &imageNotification;
        gLinkContext.terminationRecorder        = &terminationRecorder;
        gLinkContext.flatExportFinder           = &flatFindExportedSymbol;
        gLinkContext.coalescedExportFinder      = &findCoalescedExportedSymbol;
        gLinkContext.undefinedHandler           = &undefinedHandler;
        gLinkContext.addImageNeedingNotification = &addImageNeedingNotification;
        gLinkContext.notifyAdding                       = &notifyAdding;
        gLinkContext.getAllMappedRegions        = &getMappedRegions;
        gLinkContext.bindingHandler                     = NULL;
        gLinkContext.bindingOptions                     = ImageLoader::kBindingNone;
        gLinkContext.mainExecutable                     = sMainExecutable;
        gLinkContext.argc                                       = argc;
        gLinkContext.argv                                       = argv;
        gLinkContext.envp                                       = envp;
        gLinkContext.apple                                      = apple;
}

static bool checkEmulation()
{
#if __i386__
        int mib[] = { CTL_KERN, KERN_CLASSIC, getpid() };
        int is_classic = 0;
        size_t len = sizeof(int);
        int ret = sysctl(mib, 3, &is_classic, &len, NULL, 0);
        if ((ret != -1) && is_classic) {
                // When a 32-bit ppc program is run under emulation on an Intel processor,
                // we want any i386 dylibs (e.g. the emulator) to not load in the shared region
                // because the shared region is being used by ppc dylibs
                gLinkContext.sharedRegionMode = ImageLoader::kDontUseSharedRegion;
                return true;
        }
#endif
        return false;
}

void link(ImageLoader* image, ImageLoader::BindingLaziness bindness, ImageLoader::InitializerRunning runInitializers)
{
        // add to list of known images.  This did not happen at creation time for bundles
        if ( image->isBundle() )
                addImage(image);

        // we detect root images as those not linked in yet 
        if ( !image->isLinked() )
                addRootImage(image);
        
        // notify ZeroLink of new image with concat of logical and physical name
        if ( sBundleNotifier != NULL && image->isBundle() ) {
                const int logicalLen = strlen(image->getLogicalPath());
                char logAndPhys[strlen(image->getPath())+logicalLen+2];
                strcpy(logAndPhys, image->getLogicalPath());
                strcpy(&logAndPhys[logicalLen+1], image->getPath());
                (*sBundleNotifier)(logAndPhys, image);
        }

        // process images
        try {
                image->link(gLinkContext, bindness, runInitializers, sAddImageCallbacks.size());
        }
        catch (const char* msg) {
                sAllImagesMightContainUnlinkedImages = true;
                throw msg;
        }
        
#if OLD_GDB_DYLD_INTERFACE
        // notify gdb that loaded libraries have changed
        gdb_dyld_state_changed();
#endif
}


//
// _pthread_keys is partitioned in a lower part that dyld will use; libSystem
// will use the upper part.  We set __pthread_tsd_first to 1 as the start of
// the lower part.  Libc will take #1 and c++ exceptions will take #2.  There
// is one free key=3 left.
//
extern "C" {
        extern int __pthread_tsd_first;
}
 

//
// 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 struct mach_header* mainExecutableMH, int argc, const char* argv[], const char* envp[], const char* apple[])
{       
        // set pthread keys to dyld range
        __pthread_tsd_first = 1;
        
        bool isEmulated = checkEmulation();
        // Pickup the pointer to the exec path.
        sExecPath = apple[0];
        if (isEmulated) {
                // under Rosetta 
                sExecPath = strdup(apple[0] + strlen(apple[0]) + 1);
        }
        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;
                }
        }
        uintptr_t result = 0;
        sMainExecutableMachHeader = mainExecutableMH;
        checkEnvironmentVariables(envp, isEmulated);
        if ( sEnv.DYLD_PRINT_OPTS ) 
                printOptions(argv);
        if ( sEnv.DYLD_PRINT_ENV ) 
                printEnvironmentVariables(envp);
        getHostInfo();
        setContext(argc, argv, envp, apple);
        ImageLoader::BindingLaziness bindness = sEnv.DYLD_BIND_AT_LAUNCH ? ImageLoader::kLazyAndNonLazy : ImageLoader::kNonLazyOnly;
        
        // load any inserted libraries before loading the main executable so that they are first in flat namespace
        int insertLibrariesCount = 0;
        if ( sEnv.DYLD_INSERT_LIBRARIES != NULL ) {
                for (const char* const* lib = sEnv.DYLD_INSERT_LIBRARIES; *lib != NULL; ++lib) {
                        insertLibrariesCount++;
                }
        }
        ImageLoader* insertedImages[insertLibrariesCount];
        if ( insertLibrariesCount > 0 ) {
                for (int i=0; i < insertLibrariesCount; ++i) {
                        try {
                                LoadContext context;
                                context.useSearchPaths          = false;
                                context.useLdLibraryPath        = false;
                                context.dontLoad                        = false;
                                context.mustBeBundle            = false;
                                context.mustBeDylib                     = true;
                                context.matchByInstallName      = false;
                                context.origin                          = NULL; // can't use @loader_path with DYLD_INSERT_LIBRARIES
                                context.rpath                           = NULL;
                                insertedImages[i] = load(sEnv.DYLD_INSERT_LIBRARIES[i], context);
                        }
                        catch (...) {
                                char buf[strlen(sEnv.DYLD_INSERT_LIBRARIES[i])+50];
                                sprintf(buf, "could not load inserted library: %s\n", sEnv.DYLD_INSERT_LIBRARIES[i]);
                                insertedImages[i]  = NULL;
                                halt(buf);
                        }
                }
        }
        
        // load and link main executable
        try {
                sMainExecutable = instantiateFromLoadedImage(mainExecutableMH, sExecPath);
                gLinkContext.mainExecutable = sMainExecutable;
                if ( sMainExecutable->forceFlat() ) {
                        gLinkContext.bindFlat = true;
                        gLinkContext.prebindUsage = ImageLoader::kUseNoPrebinding;
                }
                link(sMainExecutable, bindness, ImageLoader::kDontRunInitializers);
                result = (uintptr_t)sMainExecutable->getMain();
        }
        catch(const char* message) {
                halt(message);
        }
        catch(...) {
                fprintf(stderr, "dyld: launch failed\n");
        }
        
        // Link in any inserted libraries.  
        // Do this after link main executable so any extra libraries pulled in by inserted libraries are at end of flat namespace
        if ( insertLibrariesCount > 0 ) {
                for (int i=0; i < insertLibrariesCount; ++i) {
                        try {
                                if ( insertedImages[i] != NULL )
                                        link(insertedImages[i], bindness, ImageLoader::kDontRunInitializers);
                        }
                        catch (const char* message) {
                                char buf[strlen(sEnv.DYLD_INSERT_LIBRARIES[i])+50+strlen(message)];
                                sprintf(buf, "could not link inserted library: %s\n%s\n", sEnv.DYLD_INSERT_LIBRARIES[i], message);
                                halt(buf);
                        }
                }
        }
        
        return result;
}




}; // namespace