dyld-832.7.1.tar.gz

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

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2004-2010 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@
 */

// work around until conformance work is complete rdar://problem/4508801
#define __srr0  srr0 
#define __eip   eip 
#define __rip   rip 


#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/fcntl.h>
#include <sys/stat.h> 
#include <sys/mman.h>
#include <mach/mach.h>
#include <mach/thread_status.h>
#include <mach-o/loader.h> 
#include <mach-o/reloc.h> 
#include <mach-o/nlist.h> 
#include <sys/sysctl.h>
#include <libkern/OSAtomic.h>
#include <libkern/OSCacheControl.h>
#include <mach-o/dyld_images.h>

#if __x86_64__
        #include <mach-o/x86_64/reloc.h>
#endif
#if __arm__
        #include <mach-o/arm/reloc.h>
#endif

#include "ImageLoaderMachOClassic.h"

// in dyldStartup.s
extern "C" void stub_binding_helper_i386_old();


#if __x86_64__
        #define POINTER_RELOC X86_64_RELOC_UNSIGNED
#else
        #define POINTER_RELOC GENERIC_RELOC_VANILLA
#endif


// relocation_info.r_length field has value 3 for 64-bit executables and value 2 for 32-bit executables
#if __LP64__
        #define RELOC_SIZE 3
        #define LC_SEGMENT_COMMAND              LC_SEGMENT_64
        #define LC_ROUTINES_COMMAND             LC_ROUTINES_64
        struct macho_segment_command    : public segment_command_64  {};
        struct macho_section                    : public section_64  {};        
        struct macho_routines_command   : public routines_command_64  {};       
#else
        #define RELOC_SIZE 2
        #define LC_SEGMENT_COMMAND              LC_SEGMENT
        #define LC_ROUTINES_COMMAND             LC_ROUTINES
        struct macho_segment_command    : public segment_command {};
        struct macho_section                    : public section  {};   
        struct macho_routines_command   : public routines_command  {};  
#endif




// create image for main executable
ImageLoaderMachOClassic* ImageLoaderMachOClassic::instantiateMainExecutable(const macho_header* mh, uintptr_t slide, const char* path, 
                                                                                                                                                unsigned int segCount, unsigned int libCount, const LinkContext& context)
{
        ImageLoaderMachOClassic* image = ImageLoaderMachOClassic::instantiateStart(mh, path, segCount, libCount);

        // set slide for PIE programs
        image->setSlide(slide);

        // for PIE record end of program, to know where to start loading dylibs
        if ( slide != 0 )
                fgNextPIEDylibAddress = (uintptr_t)image->getEnd();

        image->disableCoverageCheck();
        image->instantiateFinish(context);
        image->setMapped(context);

#if __i386__
        // kernel may have mapped in __IMPORT segment read-only, we need it read/write to do binding
        if ( image->fReadOnlyImportSegment ) {
                for(unsigned int i=0; i < image->fSegmentsCount; ++i) {
                        if ( image->segIsReadOnlyImport(i) )
                                image->segMakeWritable(i, context);
                }
        }
#endif

        if ( context.verboseMapping ) {
                dyld::log("dyld: Main executable mapped %s\n", path);
                for(unsigned int i=0, e=image->segmentCount(); i < e; ++i) {
                        const char* name = image->segName(i);
                        if ( (strcmp(name, "__PAGEZERO") == 0) || (strcmp(name, "__UNIXSTACK") == 0)  )
                                dyld::log("%18s at 0x%08lX->0x%08lX\n", name, image->segPreferredLoadAddress(i), image->segPreferredLoadAddress(i)+image->segSize(i));
                        else
                                dyld::log("%18s at 0x%08lX->0x%08lX\n", name, image->segActualLoadAddress(i), image->segActualEndAddress(i));
                }
        }

        return image;
}

// create image by mapping in a mach-o file
ImageLoaderMachOClassic* ImageLoaderMachOClassic::instantiateFromFile(const char* path, int fd, const uint8_t* fileData, size_t lenFileData,
                                                                                                                        uint64_t offsetInFat, uint64_t lenInFat, const struct stat& info, 
                                                                                                                        unsigned int segCount, unsigned int libCount, 
                                                                                                                        const struct linkedit_data_command* codeSigCmd, const LinkContext& context)
{
        ImageLoaderMachOClassic* image = ImageLoaderMachOClassic::instantiateStart((macho_header*)fileData, path, segCount, libCount);
        try {
                // record info about file  
                image->setFileInfo(info.st_dev, info.st_ino, info.st_mtime);

                // if this image is code signed, let kernel validate signature before mapping any pages from image
                image->loadCodeSignature(codeSigCmd, fd, offsetInFat, context);
                
                // Validate that first data we read with pread actually matches with code signature
                image->validateFirstPages(codeSigCmd, fd, fileData, lenFileData, offsetInFat, context);

                // mmap segments
                image->mapSegmentsClassic(fd, offsetInFat, lenInFat, info.st_size, context);

                // finish up
                image->instantiateFinish(context);

                // if path happens to be same as in LC_DYLIB_ID load command use that, otherwise malloc a copy of the path
                const char* installName = image->getInstallPath();
                if ( (installName != NULL) && (strcmp(installName, path) == 0) && (path[0] == '/') )
                        image->setPathUnowned(installName);
                else if ( (path[0] != '/') || (strstr(path, "../") != NULL) ) {
                        // rdar://problem/10733082 Fix up @path based paths during introspection
                        // rdar://problem/5135363 turn relative paths into absolute paths so gdb, Symbolication can later find them
                        char realPath[MAXPATHLEN];
                        if ( fcntl(fd, F_GETPATH, realPath) == 0 ) 
                                image->setPaths(path, realPath);
                        else
                                image->setPath(path);
                }
                else 
                        image->setPath(path);

                // make sure path is stable before recording in dyld_all_image_infos
                image->setMapped(context);

        }
        catch (...) {
                // ImageLoader::setMapped() can throw an exception to block loading of image
                // <rdar://problem/6169686> Leaked fSegmentsArray and image segments during failed dlopen_preflight
                delete image;
                throw;
        }
        
        return image;
}

// create image by using cached mach-o file
ImageLoaderMachOClassic* ImageLoaderMachOClassic::instantiateFromCache(const macho_header* mh, const char* path, long slide, const struct stat& info,
                                                                                                                                unsigned int segCount, unsigned int libCount, const LinkContext& context)
{
        ImageLoaderMachOClassic* image = ImageLoaderMachOClassic::instantiateStart(mh, path, segCount, libCount);
        try {
                // record info about file  
                image->setFileInfo(info.st_dev, info.st_ino, info.st_mtime);

                // remember this is from shared cache and cannot be unloaded
                image->fInSharedCache = true;
                image->setNeverUnload();
                image->disableCoverageCheck();

                // segments already mapped in cache
                if ( context.verboseMapping ) {
                        dyld::log("dyld: Using shared cached for %s\n", path);
                        for(unsigned int i=0, e=image->segmentCount(); i < e; ++i) {
                                dyld::log("%18s at 0x%08lX->0x%08lX\n", image->segName(i), image->segActualLoadAddress(i), image->segActualEndAddress(i));
                        }
                }

                image->instantiateFinish(context);
                image->setMapped(context);
        }
        catch (...) {
                // ImageLoader::setMapped() can throw an exception to block loading of image
                // <rdar://problem/6169686> Leaked fSegmentsArray and image segments during failed dlopen_preflight
                delete image;
                throw;
        }
        
        return image;
}

// create image by copying an in-memory mach-o file
ImageLoaderMachOClassic* ImageLoaderMachOClassic::instantiateFromMemory(const char* moduleName, const macho_header* mh, uint64_t len, 
                                                                                                                        unsigned int segCount, unsigned int libCount, const LinkContext& context)
{
        ImageLoaderMachOClassic* image = ImageLoaderMachOClassic::instantiateStart(mh, moduleName, segCount, libCount);
        try {
                // map segments 
                if ( mh->filetype == MH_EXECUTE ) 
                        throw "can't load another MH_EXECUTE";
                
                // vmcopy segments
                image->ImageLoaderMachO::mapSegments((const void*)mh, len, context);

                // for compatibility, never unload dylibs loaded from memory
                image->setNeverUnload();

                image->disableCoverageCheck();

                // bundle loads need path copied
                if ( moduleName != NULL ) 
                        image->setPath(moduleName);

                image->instantiateFinish(context);
                image->setMapped(context);
        }
        catch (...) {
                // ImageLoader::setMapped() can throw an exception to block loading of image
                // <rdar://problem/6169686> Leaked fSegmentsArray and image segments during failed dlopen_preflight
                delete image;
                throw;
        }
        
        return image;
}


ImageLoaderMachOClassic::ImageLoaderMachOClassic(const macho_header* mh, const char* path, 
                                                                                                        unsigned int segCount, uint32_t segOffsets[], unsigned int libCount)
 : ImageLoaderMachO(mh, path, segCount, segOffsets, libCount), fStrings(NULL), fSymbolTable(NULL), fDynamicInfo(NULL)
{
}

// construct ImageLoaderMachOClassic using "placement new" with SegmentMachO objects array at end
ImageLoaderMachOClassic* ImageLoaderMachOClassic::instantiateStart(const macho_header* mh, const char* path,
                                                                                                                                                unsigned int segCount, unsigned int libCount)
{
        size_t size = sizeof(ImageLoaderMachOClassic) + segCount * sizeof(uint32_t) + libCount * sizeof(ImageLoader*);
        ImageLoaderMachOClassic* allocatedSpace = static_cast<ImageLoaderMachOClassic*>(malloc(size));
        if ( allocatedSpace == NULL )
                throw "malloc failed";
        uint32_t* segOffsets = ((uint32_t*)(((uint8_t*)allocatedSpace) + sizeof(ImageLoaderMachOClassic)));
        bzero(&segOffsets[segCount], libCount*sizeof(void*));   // zero out lib array
        return new (allocatedSpace) ImageLoaderMachOClassic(mh, path, segCount, segOffsets, libCount);
}



// common code to finish initializing object
void ImageLoaderMachOClassic::instantiateFinish(const LinkContext& context)
{
        // now that segments are mapped in, get real fMachOData, fLinkEditBase, and fSlide
        this->parseLoadCmds(context);
}

ImageLoaderMachOClassic::~ImageLoaderMachOClassic()
{
        // don't do clean up in ~ImageLoaderMachO() because virtual call to segmentCommandOffsets() won't work
        destroy();
}

uint32_t* ImageLoaderMachOClassic::segmentCommandOffsets() const
{
        return ((uint32_t*)(((uint8_t*)this) + sizeof(ImageLoaderMachOClassic)));
}


ImageLoader* ImageLoaderMachOClassic::libImage(unsigned int libIndex) const
{
        const uintptr_t* images = ((uintptr_t*)(((uint8_t*)this) + sizeof(ImageLoaderMachOClassic) + fSegmentsCount*sizeof(uint32_t)));
        // mask off low bits
        return (ImageLoader*)(images[libIndex] & (-4));
}

bool ImageLoaderMachOClassic::libReExported(unsigned int libIndex) const
{
        const uintptr_t* images = ((uintptr_t*)(((uint8_t*)this) + sizeof(ImageLoaderMachOClassic) + fSegmentsCount*sizeof(uint32_t)));
        // re-export flag is low bit
        return ((images[libIndex] & 1) != 0);
}       

bool ImageLoaderMachOClassic::libIsUpward(unsigned int libIndex) const
{
        const uintptr_t* images = ((uintptr_t*)(((uint8_t*)this) + sizeof(ImageLoaderMachOClassic) + fSegmentsCount*sizeof(uint32_t)));
        // upward flag is second bit
        return ((images[libIndex] & 2) != 0);
}       


void ImageLoaderMachOClassic::setLibImage(unsigned int libIndex, ImageLoader* image, bool reExported, bool upward)
{
        uintptr_t* images = ((uintptr_t*)(((uint8_t*)this) + sizeof(ImageLoaderMachOClassic) + fSegmentsCount*sizeof(uint32_t)));
        uintptr_t value = (uintptr_t)image;
        if ( reExported ) 
                value |= 1;
        if ( upward ) 
                value |= 2;
        images[libIndex] = value;
}


void ImageLoaderMachOClassic::setSymbolTableInfo(const macho_nlist* symbols, const char* strings, const dysymtab_command* dynSym)
{
        fSymbolTable = symbols;
        fStrings = strings;
        fDynamicInfo = dynSym;
}



#if SPLIT_SEG_DYLIB_SUPPORT     
unsigned int
ImageLoaderMachOClassic::getExtraZeroFillEntriesCount()
{
        // calculate mapping entries
        unsigned int extraZeroFillEntries = 0;
        for(unsigned int i=0; i < fSegmentsCount; ++i) {
                if ( segHasTrailingZeroFill(i) )
                        ++extraZeroFillEntries;
        }
        
        return extraZeroFillEntries;
}

void
ImageLoaderMachOClassic::initMappingTable(uint64_t offsetInFat,
                                                                   shared_file_mapping_np *mappingTable)
{
        for(unsigned int i=0,entryIndex=0; i < fSegmentsCount; ++i, ++entryIndex) {
                shared_file_mapping_np* entry = &mappingTable[entryIndex];
                entry->sfm_address                      = segActualLoadAddress(i);
                entry->sfm_size                         = segFileSize(i);
                entry->sfm_file_offset          = segFileOffset(i) + offsetInFat;
                entry->sfm_init_prot            = VM_PROT_NONE;
                if ( !segUnaccessible(i) ) {
                        if ( segExecutable(i) )
                                entry->sfm_init_prot   |= VM_PROT_EXECUTE;
                        if ( segReadable(i) )
                                entry->sfm_init_prot   |= VM_PROT_READ;
                        if ( segWriteable(i) )
                                entry->sfm_init_prot   |= VM_PROT_WRITE | VM_PROT_COW;
                }
                entry->sfm_max_prot                     = entry->sfm_init_prot;
                if ( segHasTrailingZeroFill(i) ) {
                        shared_file_mapping_np* zfentry = &mappingTable[++entryIndex];
                        zfentry->sfm_address            = entry->sfm_address + segFileSize(i);
                        zfentry->sfm_size                       = segSize(i) - segFileSize(i);
                        zfentry->sfm_file_offset        = 0;
                        zfentry->sfm_init_prot          = entry->sfm_init_prot | VM_PROT_COW | VM_PROT_ZF;
                        zfentry->sfm_max_prot           = zfentry->sfm_init_prot;
                }
        }
}

int
ImageLoaderMachOClassic::mapSplitSegDylibOutsideSharedRegion(int fd,
                                                                                                        uint64_t offsetInFat,
                                                                                                        uint64_t lenInFat,
                                                                                                        uint64_t fileLen,
                                                                                                        const LinkContext& context)
{
        uintptr_t nextAltLoadAddress = 0;
        const unsigned int segmentCount = fSegmentsCount;
        const unsigned int extraZeroFillEntries = getExtraZeroFillEntriesCount();
        const unsigned int regionCount = segmentCount+extraZeroFillEntries;
        shared_file_mapping_np regions[regionCount];
        initMappingTable(offsetInFat, regions);
        int r = -1;
        // find space somewhere to allocate split seg
        bool foundRoom = false;
        while ( ! foundRoom ) {
                foundRoom = true;
                for(unsigned int i=0; i < regionCount; ++i) {
                        vm_address_t addr = (vm_address_t)(nextAltLoadAddress + regions[i].sfm_address - regions[0].sfm_address);
                        vm_size_t size = (vm_size_t)regions[i].sfm_size ;
                        r = vm_allocate(mach_task_self(), &addr, size, false /*only this range*/);
                        if ( 0 != r ) {
                                // no room here, deallocate what has succeeded so far
                                for(unsigned int j=0; j < i; ++j) {
                                        addr = (vm_address_t)(nextAltLoadAddress + regions[j].sfm_address - regions[0].sfm_address);
                                        size = (vm_size_t)(regions[j].sfm_size);
                                        (void)vm_deallocate(mach_task_self(), addr, size);
                                }
                                nextAltLoadAddress += 0x00100000;  // skip ahead 1MB and try again
                                // skip over shared region
                                if ( (SHARED_REGION_BASE <= nextAltLoadAddress) && (nextAltLoadAddress < (SHARED_REGION_BASE + SHARED_REGION_SIZE)) )
                                        nextAltLoadAddress = (SHARED_REGION_BASE + SHARED_REGION_SIZE);
                                if ( nextAltLoadAddress > 0xFF000000 )
                                        throw "can't map split seg anywhere";
                                foundRoom = false;
                                break;
                        }
                }
        }
        
        // map in each region
        uintptr_t slide = (uintptr_t)(nextAltLoadAddress - regions[0].sfm_address);
        this->setSlide(slide);
        for(unsigned int i=0; i < regionCount; ++i) {
                if ( ((regions[i].sfm_init_prot & VM_PROT_ZF) != 0) || (regions[i].sfm_size == 0) ) {
                        // nothing to mmap for zero-fills areas, they are just vm_allocated 
                }
                else {
                        void* mmapAddress = (void*)(uintptr_t)(regions[i].sfm_address + slide);
                        size_t size = (size_t)regions[i].sfm_size;
                        int protection = 0;
                        if ( regions[i].sfm_init_prot & VM_PROT_EXECUTE )
                                protection   |= PROT_EXEC;
                        if ( regions[i].sfm_init_prot & VM_PROT_READ )
                                protection   |= PROT_READ;
                        if ( regions[i].sfm_init_prot & VM_PROT_WRITE )
                                protection   |= PROT_WRITE;
                        off_t offset = regions[i].sfm_file_offset;
                        //dyld::log("mmap(%p, 0x%08lX, %s\n", mmapAddress, size, fPath);
                        mmapAddress = mmap(mmapAddress, size, protection, MAP_FIXED | MAP_PRIVATE, fd, offset);
                        if ( mmapAddress == ((void*)(-1)) )
                                throw "mmap error";
                }
        }
        
        // logging
        if ( context.verboseMapping ) {
                dyld::log("dyld: Mapping split-seg outside shared region, slid by 0x%08lX %s\n", this->fSlide, this->getPath());
                for(unsigned int segIndex=0,entryIndex=0; segIndex < segmentCount; ++segIndex, ++entryIndex){
                        const shared_file_mapping_np* entry = &regions[entryIndex];
                        if ( (entry->sfm_init_prot & VM_PROT_ZF) == 0 ) 
                                dyld::log("%18s at 0x%08lX->0x%08lX\n",
                                                segName(segIndex), segActualLoadAddress(segIndex), segActualEndAddress(segIndex)-1);
                        if ( entryIndex < (regionCount-1) ) {
                                const shared_file_mapping_np* nextEntry = &regions[entryIndex+1];
                                if ( (nextEntry->sfm_init_prot & VM_PROT_ZF) != 0 ) {
                                        uint64_t segOffset = nextEntry->sfm_address - entry->sfm_address;
                                        dyld::log("%18s at 0x%08lX->0x%08lX (zerofill)\n",
                                                        segName(segIndex), (uintptr_t)(segActualLoadAddress(segIndex) + segOffset), (uintptr_t)(segActualLoadAddress(segIndex) + segOffset + nextEntry->sfm_size - 1));
                                        ++entryIndex;
                                }
                        }
                }
        }
        
        return r;
}
#endif // SPLIT_SEG_DYLIB_SUPPORT


void ImageLoaderMachOClassic::mapSegmentsClassic(int fd, uint64_t offsetInFat, uint64_t lenInFat, uint64_t fileLen, const LinkContext& context)
{
        // non-split segment libraries handled by super class
        if ( !fIsSplitSeg )
                return ImageLoaderMachO::mapSegments(fd, offsetInFat, lenInFat, fileLen, context);

#if SPLIT_SEG_SHARED_REGION_SUPPORT     
        // don't map split-seg dylibs into shared region if shared cache is in use
        if ( ! context.dyldLoadedAtSameAddressNeededBySharedCache ) {
                // try to map into shared region at preferred address
                if ( mapSplitSegDylibInfoSharedRegion(fd, offsetInFat, lenInFat, fileLen, context) == 0) 
                        return;
        }
        // if there is a problem, fall into case where we map file somewhere outside the shared region
#endif

#if SPLIT_SEG_DYLIB_SUPPORT
        // support old split-seg dylibs by mapping them where ever we find space
        if ( mapSplitSegDylibOutsideSharedRegion(fd, offsetInFat, lenInFat, fileLen, context) != 0 ) 
#endif
                throw "mapping error";
}


#if SPLIT_SEG_SHARED_REGION_SUPPORT     
static int _shared_region_map_np(int fd, uint32_t count, const shared_file_mapping_np mappings[])
{
        return syscall(295, fd, count, mappings);
}

int
ImageLoaderMachOClassic::mapSplitSegDylibInfoSharedRegion(int fd,
                                         uint64_t offsetInFat,
                                         uint64_t lenInFat,
                                         uint64_t fileLen,
                                         const LinkContext& context)
{
        // build table of segments to map
        const unsigned int segmentCount = fSegmentsCount;
        const unsigned int extraZeroFillEntries = getExtraZeroFillEntriesCount();
        const unsigned int mappingTableCount = segmentCount+extraZeroFillEntries;
        shared_file_mapping_np mappingTable[mappingTableCount];
        initMappingTable(offsetInFat, mappingTable);

        // try to map it in shared
        int r = _shared_region_map_np(fd, mappingTableCount, mappingTable);
        if ( 0 == r ) {
                this->setNeverUnload();
                if ( context.verboseMapping ) {
                        dyld::log("dyld: Mapping split-seg shared %s\n", this->getPath());
                        for(unsigned int segIndex=0,entryIndex=0; segIndex < segmentCount; ++segIndex, ++entryIndex){
                                const shared_file_mapping_np* entry = &mappingTable[entryIndex];
                                if ( (entry->sfm_init_prot & VM_PROT_ZF) == 0 ) 
                                        dyld::log("%18s at 0x%08lX->0x%08lX\n",
                                                          segName(segIndex), segActualLoadAddress(segIndex), segActualEndAddress(segIndex)-1);
                                if ( entryIndex < (mappingTableCount-1) ) {
                                        const shared_file_mapping_np* nextEntry = &mappingTable[entryIndex+1];
                                        if ( (nextEntry->sfm_init_prot & VM_PROT_ZF) != 0 ) {
                                                uint64_t segOffset = nextEntry->sfm_address - entry->sfm_address;
                                                dyld::log("%18s at 0x%08lX->0x%08lX\n",
                                                                  segName(segIndex), (uintptr_t)(segActualLoadAddress(segIndex) + segOffset), 
                                                                  (uintptr_t)(segActualLoadAddress(segIndex) + segOffset + nextEntry->sfm_size - 1));
                                                ++entryIndex;
                                        }
                                }
                        }
                }
        }
        return r;
}

#endif // SPLIT_SEG_SHARED_REGION_SUPPORT       

// test if this image is re-exported through parent (the image that loaded this one)
bool ImageLoaderMachOClassic::isSubframeworkOf(const LinkContext& context, const ImageLoader* parent) const
{
        if ( fInUmbrella ) {
                const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
                const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
                const struct load_command* cmd = cmds;
                for (uint32_t i = 0; i < cmd_count; ++i) {
                        if (cmd->cmd == LC_SUB_FRAMEWORK) {
                                const struct sub_framework_command* subf = (struct sub_framework_command*)cmd;
                                const char* exportThruName = (char*)cmd + subf->umbrella.offset;
                                // need to match LC_SUB_FRAMEWORK string against the leaf name of the install location of parent...
                                const char* parentInstallPath = parent->getInstallPath();
                                if ( parentInstallPath != NULL ) {
                                        const char* lastSlash = strrchr(parentInstallPath, '/');
                                        if ( lastSlash != NULL ) {
                                                if ( strcmp(&lastSlash[1], exportThruName) == 0 )
                                                        return true;
                                                if ( context.imageSuffix != NULL ) {
                                                        // when DYLD_IMAGE_SUFFIX is used, lastSlash string needs imageSuffix removed from end
                                                        for(const char* const* suffix = context.imageSuffix; *suffix != NULL; ++suffix) {
                                                                char reexportAndSuffix[strlen(*suffix)+strlen(exportThruName)+1];
                                                                strcpy(reexportAndSuffix, exportThruName);
                                                                strcat(reexportAndSuffix, *suffix);
                                                                if ( strcmp(&lastSlash[1], reexportAndSuffix) == 0 )
                                                                        return true;
                                                        }
                                                }
                                        }
                                }
                        }
                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                }
        }
        return false;
}

// test if child is re-exported 
bool ImageLoaderMachOClassic::hasSubLibrary(const LinkContext& context, const ImageLoader* child) const
{
        if ( fHasSubLibraries ) {
                // need to match LC_SUB_LIBRARY string against the leaf name (without extension) of the install location of child...
                const char* childInstallPath = child->getInstallPath();
                if ( childInstallPath != NULL ) {
                        const char* lastSlash = strrchr(childInstallPath, '/');
                        if ( lastSlash != NULL ) {
                                const char* firstDot = strchr(lastSlash, '.');
                                size_t len;
                                if ( firstDot == NULL )
                                        len = strlen(lastSlash);
                                else
                                        len = firstDot-lastSlash-1;
                                char childLeafName[len+1];
                                strncpy(childLeafName, &lastSlash[1], len);
                                childLeafName[len] = '\0';
                                const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
                                const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
                                const struct load_command* cmd = cmds;
                                for (uint32_t i = 0; i < cmd_count; ++i) {
                                        switch (cmd->cmd) {
                                                case LC_SUB_LIBRARY:
                                                        {
                                                                const struct sub_library_command* lib = (struct sub_library_command*)cmd;
                                                                const char* aSubLibName = (char*)cmd + lib->sub_library.offset;
                                                                if ( strcmp(aSubLibName, childLeafName) == 0 )
                                                                        return true;
                                                                if ( context.imageSuffix != NULL ) {
                                                                        // when DYLD_IMAGE_SUFFIX is used, childLeafName string needs imageSuffix removed from end
                                                                        for(const char* const* suffix = context.imageSuffix; *suffix != NULL; ++suffix) {
                                                                                char aSubLibNameAndSuffix[strlen(*suffix)+strlen(aSubLibName)+1];
                                                                                strcpy(aSubLibNameAndSuffix, aSubLibName);
                                                                                strcat(aSubLibNameAndSuffix, *suffix);
                                                                                if ( strcmp(aSubLibNameAndSuffix, childLeafName) == 0 )
                                                                                        return true;
                                                                        }
                                                                }
                                                        }
                                                        break;
                                        }
                                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                                }
                        }
                }
        }
        if ( fHasSubUmbrella ) {
                // need to match LC_SUB_UMBRELLA string against the leaf name of install location of child...
                const char* childInstallPath = child->getInstallPath();
                if ( childInstallPath != NULL ) {
                        const char* lastSlash = strrchr(childInstallPath, '/');
                        if ( lastSlash != NULL ) {
                                const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
                                const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
                                const struct load_command* cmd = cmds;
                                for (uint32_t i = 0; i < cmd_count; ++i) {
                                        switch (cmd->cmd) {
                                                case LC_SUB_UMBRELLA:
                                                        {
                                                                const struct sub_umbrella_command* um = (struct sub_umbrella_command*)cmd;
                                                                const char* aSubUmbrellaName = (char*)cmd + um->sub_umbrella.offset;
                                                                if ( strcmp(aSubUmbrellaName, &lastSlash[1]) == 0 )
                                                                        return true;
                                                                if ( context.imageSuffix != NULL ) {
                                                                        // when DYLD_IMAGE_SUFFIX is used, lastSlash string needs imageSuffix removed from end
                                                                        for(const char* const* suffix = context.imageSuffix; *suffix != NULL; ++suffix) {
                                                                                char umbrellaAndSuffix[strlen(*suffix)+strlen(aSubUmbrellaName)+1];
                                                                                strcpy(umbrellaAndSuffix, aSubUmbrellaName);
                                                                                strcat(umbrellaAndSuffix, *suffix);
                                                                                if ( strcmp(umbrellaAndSuffix, &lastSlash[1]) == 0 )
                                                                                        return true;
                                                                        }
                                                                }
                                                        }
                                                        break;
                                        }
                                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                                }
                        }
                }
        }
        return false;
}


uintptr_t ImageLoaderMachOClassic::getFirstWritableSegmentAddress()
{
        // in split segment libraries r_address is offset from first writable segment
        for(unsigned int i=0; i < fSegmentsCount; ++i) {
                if ( segWriteable(i) ) 
                        return segActualLoadAddress(i);
        }
        throw "no writable segment";
}

uintptr_t ImageLoaderMachOClassic::getRelocBase()
{
        // r_address is either an offset from the first segment address
        // or from the first writable segment address
#if __x86_64__
        return getFirstWritableSegmentAddress();
#else
        if ( fIsSplitSeg )
                return getFirstWritableSegmentAddress();
        else
                return segActualLoadAddress(0);
#endif
}


#if PREBOUND_IMAGE_SUPPORT
void ImageLoaderMachOClassic::resetPreboundLazyPointers(const LinkContext& context)
{
        // loop through all local (internal) relocation records looking for pre-bound-lazy-pointer values
        const uintptr_t relocBase = this->getRelocBase();
    const uintptr_t slide = this->fSlide;
        const relocation_info* const relocsStart = (struct relocation_info*)(&fLinkEditBase[fDynamicInfo->locreloff]);
        const relocation_info* const relocsEnd = &relocsStart[fDynamicInfo->nlocrel];
        for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
                if ( (reloc->r_address & R_SCATTERED) != 0 ) {
                        const struct scattered_relocation_info* sreloc = (struct scattered_relocation_info*)reloc;
                        if (sreloc->r_length == RELOC_SIZE) {
                                uintptr_t* locationToFix = (uintptr_t*)(sreloc->r_address + relocBase);
                                switch(sreloc->r_type) {
                #if __i386__
                                        case GENERIC_RELOC_PB_LA_PTR:
                                                *locationToFix = sreloc->r_value + slide;
                                                break;
                #endif
                #if __arm__
                                        case ARM_RELOC_PB_LA_PTR:
                                                *locationToFix = sreloc->r_value + slide;
                                                break;
                #endif
                                }
                        }
                }
        }
}
#endif




void ImageLoaderMachOClassic::rebase(const LinkContext& context, uintptr_t slide)
{
        CRSetCrashLogMessage2(this->getPath());
        const uintptr_t relocBase = this->getRelocBase();

        // loop through all local (internal) relocation records
        const relocation_info* const relocsStart = (struct relocation_info*)(&fLinkEditBase[fDynamicInfo->locreloff]);
        const relocation_info* const relocsEnd = &relocsStart[fDynamicInfo->nlocrel];
        for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
                uintptr_t rebaseAddr;
                try {
        #if LINKEDIT_USAGE_DEBUG
                        noteAccessedLinkEditAddress(reloc);
        #endif
                #if __x86_64__
                        // only one kind of local relocation supported for x86_64
                        if ( reloc->r_length != 3 ) 
                                throw "bad local relocation length";
                        if ( reloc->r_type != X86_64_RELOC_UNSIGNED ) 
                                throw "unknown local relocation type";
                        if ( reloc->r_pcrel != 0 ) 
                                throw "bad local relocation pc_rel";
                        if ( reloc->r_extern != 0 ) 
                                throw "extern relocation found with local relocations";
                        rebaseAddr = reloc->r_address + relocBase;
                        if ( ! this->containsAddress((void*)rebaseAddr) )
                                dyld::throwf("local reloc %p not in mapped image\n", (void*)rebaseAddr);
                        *((uintptr_t*)rebaseAddr) += slide;
                        if ( context.verboseRebase )
                                dyld::log("dyld: rebase: %s:*0x%08lX += 0x%08lX\n", this->getShortName(), rebaseAddr, slide);
                #else   
                        if ( (reloc->r_address & R_SCATTERED) == 0 ) {
                                if ( reloc->r_symbolnum == R_ABS ) {
                                        // ignore absolute relocations
                                }
                                else if (reloc->r_length == RELOC_SIZE) {
                                        switch(reloc->r_type) {
                                                case GENERIC_RELOC_VANILLA:
                                                        rebaseAddr = reloc->r_address + relocBase;
                                                        if ( ! this->containsAddress((void*)rebaseAddr) )
                                                                dyld::throwf("local reloc %p not in mapped image\n", (void*)rebaseAddr);
                                                        *((uintptr_t*)rebaseAddr) += slide;
                                                        if ( context.verboseRebase )
                                                                dyld::log("dyld: rebase: %s:*0x%08lX += 0x%08lX\n", this->getShortName(), rebaseAddr, slide);
                                                        break;
                                                default:
                                                        throw "unknown local relocation type";
                                        }
                                }
                                else {
                                        throw "bad local relocation length";
                                }
                        }
                        else {
                                const struct scattered_relocation_info* sreloc = (struct scattered_relocation_info*)reloc;
                                if (sreloc->r_length == RELOC_SIZE) {
                                        uintptr_t* locationToFix = (uintptr_t*)(sreloc->r_address + relocBase);
                                        switch(sreloc->r_type) {
                                                case GENERIC_RELOC_VANILLA:
                                                        if ( ! this->containsAddress((void*)locationToFix) ) 
                                                                dyld::throwf("local scattered reloc %p not in mapped image\n", locationToFix);
                                                        *locationToFix += slide;
                                                        if ( context.verboseRebase )
                                                                dyld::log("dyld: rebase: %s:*0x%08lX += 0x%08lX\n", this->getShortName(), (uintptr_t)locationToFix, slide);
                                                        break;
                        #if __i386__
                                                case GENERIC_RELOC_PB_LA_PTR:
                                                        // do nothing
                                                        break;
                        #elif __arm__
                                                case ARM_RELOC_PB_LA_PTR:
                                                        // do nothing
                                                        break;
                        #endif
                                                default:
                                                        throw "unknown local scattered relocation type";
                                        }
                                }
                                else {
                                        throw "bad local scattered relocation length";
                                }
                        }
                #endif // x86_64
                }
                catch (const char* msg) {
                        const uint8_t* r = (uint8_t*)reloc;
                        dyld::throwf("%s in %s. reloc record at %p: 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X 0x%02X",
                                msg, this->getPath(), reloc, r[0], r[1], r[2], r[3], r[4], r[5], r[6], r[7]);
                }
        }
        
        // update stats
        fgTotalRebaseFixups += fDynamicInfo->nlocrel;
        CRSetCrashLogMessage2(NULL);
}



const struct macho_nlist* ImageLoaderMachOClassic::binarySearchWithToc(const char* key, const char stringPool[], const struct macho_nlist symbols[], 
                                                                                                const struct dylib_table_of_contents toc[], uint32_t symbolCount, uint32_t hintIndex) const
{
        int32_t high = symbolCount-1;
        int32_t mid = hintIndex;
        
        // handle out of range hint
        if ( mid >= (int32_t)symbolCount )
                mid = symbolCount/2;
        ++ImageLoaderMachO::fgSymbolTableBinarySearchs;
        ++fgTotalBindImageSearches;     

        //dyld::log("dyld: binarySearchWithToc for %s in %s\n", key, this->getShortName());

        for (int32_t low = 0; low <= high; mid = (low+high)/2) {
                const uint32_t index = toc[mid].symbol_index;
                const struct macho_nlist* pivot = &symbols[index];
                const char* pivotStr = &stringPool[pivot->n_un.n_strx];
#if LINKEDIT_USAGE_DEBUG
                noteAccessedLinkEditAddress(&toc[mid]);
                noteAccessedLinkEditAddress(pivot);
                noteAccessedLinkEditAddress(pivotStr);
#endif
                int cmp = strcmp(key, pivotStr);
                if ( cmp == 0 )
                        return pivot;
                if ( cmp > 0 ) {
                        // key > pivot 
                        low = mid + 1;
                }
                else {
                        // key < pivot 
                        high = mid - 1;
                }
        }
        return NULL;
}

const struct macho_nlist* ImageLoaderMachOClassic::binarySearch(const char* key, const char stringPool[], const struct macho_nlist symbols[], uint32_t symbolCount) const
{
        // update stats
        ++fgTotalBindImageSearches;     
        ++ImageLoaderMachO::fgSymbolTableBinarySearchs;
        
        //dyld::log("dyld: binarySearch for %s in %s, stringpool=%p, symbols=%p, symbolCount=%u\n", 
        //                              key, this->getShortName(), stringPool, symbols, symbolCount);

        const struct macho_nlist* base = symbols;
        for (uint32_t n = symbolCount; n > 0; n /= 2) {
                const struct macho_nlist* pivot = &base[n/2];
                const char* pivotStr = &stringPool[pivot->n_un.n_strx];
#if LINKEDIT_USAGE_DEBUG
                noteAccessedLinkEditAddress(pivot);
                noteAccessedLinkEditAddress(pivotStr);
#endif
                int cmp = strcmp(key, pivotStr);
                if ( cmp == 0 )
                        return pivot;
                if ( cmp > 0 ) {
                        // key > pivot 
                        // move base to symbol after pivot
                        base = &pivot[1];
                        --n; 
                }
                else {
                        // key < pivot 
                        // keep same base
                }
        }
        return NULL;
}


const ImageLoader::Symbol* ImageLoaderMachOClassic::findShallowExportedSymbol(const char* name, const ImageLoader** foundIn) const
{
        const struct macho_nlist* sym = NULL;
        if ( fDynamicInfo->tocoff == 0 )
                sym = binarySearch(name, fStrings, &fSymbolTable[fDynamicInfo->iextdefsym], fDynamicInfo->nextdefsym);
        else 
                sym = binarySearchWithToc(name, fStrings, fSymbolTable, (dylib_table_of_contents*)&fLinkEditBase[fDynamicInfo->tocoff], 
                                                                                fDynamicInfo->ntoc, fDynamicInfo->nextdefsym);
        if ( sym != NULL ) {
                if ( foundIn != NULL )
                        *foundIn = (ImageLoader*)this;          
                return (const Symbol*)sym;
        }
        return NULL;
}



bool ImageLoaderMachOClassic::containsSymbol(const void* addr) const
{
        return ( (fSymbolTable <= addr) && (addr < fStrings) );
}


uintptr_t ImageLoaderMachOClassic::exportedSymbolAddress(const LinkContext& context, const Symbol* symbol, const ImageLoader* requestor, bool runResolver) const
{
        const struct macho_nlist* sym = (macho_nlist*)symbol;
        uintptr_t result = sym->n_value + fSlide;
        #if __arm__
                // processor assumes code address with low bit set is thumb
                if (sym->n_desc & N_ARM_THUMB_DEF)
                        result |= 1;
        #endif
        return result;
}

bool ImageLoaderMachOClassic::exportedSymbolIsWeakDefintion(const Symbol* symbol) const
{
        const struct macho_nlist* nlistSym = (const struct macho_nlist*)symbol;
        return ( (nlistSym->n_desc & N_WEAK_DEF) != 0 );
}

const char* ImageLoaderMachOClassic::exportedSymbolName(const Symbol* symbol) const
{
        const struct macho_nlist* nlistSym = (const struct macho_nlist*)symbol;
        return &fStrings[nlistSym->n_un.n_strx];
}

unsigned int ImageLoaderMachOClassic::exportedSymbolCount() const
{
        return fDynamicInfo->nextdefsym;
}

const ImageLoader::Symbol* ImageLoaderMachOClassic::exportedSymbolIndexed(unsigned int index) const
{
        if ( index < fDynamicInfo->nextdefsym ) {
                const struct macho_nlist* sym = &fSymbolTable[fDynamicInfo->iextdefsym + index];
                return (const ImageLoader::Symbol*)sym;
        }
        return NULL;
}

unsigned int ImageLoaderMachOClassic::importedSymbolCount() const
{
        return fDynamicInfo->nundefsym;
}

const ImageLoader::Symbol* ImageLoaderMachOClassic::importedSymbolIndexed(unsigned int index) const
{
        if ( index < fDynamicInfo->nundefsym ) {
                const struct macho_nlist* sym = &fSymbolTable[fDynamicInfo->iundefsym + index];
                return (const ImageLoader::Symbol*)sym;
        }
        return NULL;
}       

const char* ImageLoaderMachOClassic::importedSymbolName(const Symbol* symbol) const
{
        const struct macho_nlist* nlistSym = (const struct macho_nlist*)symbol;
        return &fStrings[nlistSym->n_un.n_strx];
}



bool ImageLoaderMachOClassic::symbolIsWeakDefinition(const struct macho_nlist* symbol)
{
        // if a define and weak ==> coalesced 
        if ( ((symbol->n_type & N_TYPE) == N_SECT) && ((symbol->n_desc & N_WEAK_DEF) != 0) ) 
                return true;
        
        // regular symbol
        return false;
}

bool ImageLoaderMachOClassic::symbolIsWeakReference(const struct macho_nlist* symbol)
{
        // if an undefine and not referencing a weak symbol ==> coalesced
        if ( ((symbol->n_type & N_TYPE) != N_SECT) && ((symbol->n_desc & N_REF_TO_WEAK) != 0) )
                return true;
        
        // regular symbol
        return false;
}

uintptr_t ImageLoaderMachOClassic::getSymbolAddress(const macho_nlist* sym, const LinkContext& context, bool runResolver) const
{
        return ImageLoaderMachO::getSymbolAddress((Symbol*)sym, this, context, runResolver);
}

uintptr_t ImageLoaderMachOClassic::resolveUndefined(const LinkContext& context, const struct macho_nlist* undefinedSymbol, 
                                                                                bool twoLevel, bool dontCoalesce, bool runResolver, const ImageLoader** foundIn)
{
        ++fgTotalBindSymbolsResolved;
        const char* symbolName = &fStrings[undefinedSymbol->n_un.n_strx];

#if LINKEDIT_USAGE_DEBUG
        noteAccessedLinkEditAddress(undefinedSymbol);
        noteAccessedLinkEditAddress(symbolName);
#endif
        if ( context.bindFlat || !twoLevel ) {
                // flat lookup
                if ( ((undefinedSymbol->n_type & N_PEXT) != 0) && ((undefinedSymbol->n_type & N_TYPE) == N_SECT) ) {
                        // is a multi-module private_extern internal reference that the linker did not optimize away
                        uintptr_t addr = this->getSymbolAddress(undefinedSymbol, context, false);
                        *foundIn = this;
                        return addr;
                }
                const Symbol* sym;
                if ( context.flatExportFinder(symbolName, &sym, foundIn) ) {
                        if ( *foundIn != this )
                                context.addDynamicReference(this, const_cast<ImageLoader*>(*foundIn));
                        return (*foundIn)->getExportedSymbolAddress(sym, context, this);
                }
                // if a bundle is loaded privately the above will not find its exports
                if ( this->isBundle() && this->hasHiddenExports() ) {
                        // look in self for needed symbol
                        sym = this->findShallowExportedSymbol(symbolName, foundIn);
                        if ( sym != NULL )
                                return (*foundIn)->getExportedSymbolAddress(sym, context, this);
                }
                if ( (undefinedSymbol->n_desc & N_WEAK_REF) != 0 ) {
                        // definition can't be found anywhere
                        // if reference is weak_import, then it is ok, just return 0
                        return 0;
                }
                throwSymbolNotFound(context, symbolName, this->getPath(), "", "flat namespace");
        }
        else {
                // symbol requires searching images with coalesced symbols (not done during prebinding)
                if ( !context.prebinding && !dontCoalesce && (symbolIsWeakReference(undefinedSymbol) || symbolIsWeakDefinition(undefinedSymbol)) ) {
                        const Symbol* sym;
                        if ( context.coalescedExportFinder(symbolName, &sym, foundIn, nullptr) ) {
                                if ( *foundIn != this )
                                        context.addDynamicReference(this, const_cast<ImageLoader*>(*foundIn));
                                return (*foundIn)->getExportedSymbolAddress(sym, context, this);
                        }
                        //throwSymbolNotFound(context, symbolName, this->getPath(), "coalesced namespace");
                        //dyld::log("dyld: coalesced symbol %s not found in any coalesced image, falling back to two-level lookup", symbolName);
                }
                
                // if this is a real definition (not an undefined symbol) there is no ordinal
                if ( (undefinedSymbol->n_type & N_TYPE) == N_SECT ) {
                        // static linker should never generate this case, but if it does, do something sane
                        uintptr_t addr = this->getSymbolAddress(undefinedSymbol, context, false);
                        *foundIn = this;
                        return addr;
                }

                // two level lookup
                ImageLoader* target = NULL;
                uint8_t ord = GET_LIBRARY_ORDINAL(undefinedSymbol->n_desc);
                if ( ord == EXECUTABLE_ORDINAL ) {
                        target = context.mainExecutable;
                }
                else if ( ord == SELF_LIBRARY_ORDINAL ) {
                        target = this;
                }
                else if ( ord == DYNAMIC_LOOKUP_ORDINAL ) {
                        // rnielsen: HACKHACK
                        // flat lookup
                        const Symbol* sym;
                        if ( context.flatExportFinder(symbolName, &sym, foundIn) )
                                return (*foundIn)->getExportedSymbolAddress(sym, context, this);
                        // no image has exports this symbol
                        // report error
                        context.undefinedHandler(symbolName);
                        // try looking again
                        if ( context.flatExportFinder(symbolName, &sym, foundIn) )
                                return (*foundIn)->getExportedSymbolAddress(sym, context, this);
                        
                        throwSymbolNotFound(context, symbolName, this->getPath(), "", "dynamic lookup");
                }
                else if ( ord <= libraryCount() ) {
                        target = libImage(ord-1);
                        if ( target == NULL ) {
                                // if target library not loaded and reference is weak or library is weak return 0
                                return 0;
                        }
                }
                else {
                        dyld::throwf("bad mach-o binary, library ordinal (%u) too big (max %u) for symbol %s in %s",
                                ord, libraryCount(), symbolName, this->getPath());
                }
                
                if ( target == NULL ) {
                        //dyld::log("resolveUndefined(%s) in %s\n", symbolName, this->getPath());
                        throw "symbol not found";
                }

                uintptr_t address;
                if ( target->findExportedSymbolAddress(context, symbolName, this, ord, runResolver, foundIn, &address) )
                        return address;

                if ( (undefinedSymbol->n_type & N_PEXT) != 0 ) {
                        // don't know why the static linker did not eliminate the internal reference to a private extern definition
                        *foundIn = this;
                        return this->getSymbolAddress(undefinedSymbol, context, false);
                }
                else if ( (undefinedSymbol->n_desc & N_WEAK_REF) != 0 ) {
                        // if definition not found and reference is weak return 0
                        return 0;
                }
                
                // nowhere to be found
                throwSymbolNotFound(context, symbolName, this->getPath(), "", target->getPath());
        }
}



// returns if 'addr' is within the address range of section 'sectionIndex'
// fSlide is not used.  'addr' is assumed to be a prebound address in this image 
bool ImageLoaderMachOClassic::isAddrInSection(uintptr_t addr, uint8_t sectionIndex)
{
        uint8_t currentSectionIndex = 1;
        const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
        const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
                        const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                        if ( (currentSectionIndex <= sectionIndex) && (sectionIndex < currentSectionIndex+seg->nsects) ) {
                                // 'sectionIndex' is in this segment, get section info
                                const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                                const struct macho_section* const section = &sectionsStart[sectionIndex-currentSectionIndex];
                                return ( (section->addr <= addr) && (addr < section->addr+section->size) );
                        }
                        else {
                                // 'sectionIndex' not in this segment, skip to next segment
                                currentSectionIndex += seg->nsects;
                        }
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        
        return false;
}

void ImageLoaderMachOClassic::doBindExternalRelocations(const LinkContext& context)
{
        const uintptr_t relocBase = this->getRelocBase();
        const bool twoLevel = this->usesTwoLevelNameSpace();
        const bool prebound = this->isPrebindable();
        
#if TEXT_RELOC_SUPPORT
        // if there are __TEXT fixups, temporarily make __TEXT writable
        if ( fTextSegmentBinds ) 
                this->makeTextSegmentWritable(context, true);
#endif
        // cache last lookup
        const struct macho_nlist*       lastUndefinedSymbol = NULL;
        uintptr_t                                       symbolAddr = 0;
        const ImageLoader*                      image = NULL;
        
        // loop through all external relocation records and bind each
        const relocation_info* const relocsStart = (struct relocation_info*)(&fLinkEditBase[fDynamicInfo->extreloff]);
        const relocation_info* const relocsEnd = &relocsStart[fDynamicInfo->nextrel];
        for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
                if (reloc->r_length == RELOC_SIZE) {
                        switch(reloc->r_type) {
                                case POINTER_RELOC:
                                        {
                                                const struct macho_nlist* undefinedSymbol = &fSymbolTable[reloc->r_symbolnum];
                                                uintptr_t* location = ((uintptr_t*)(reloc->r_address + relocBase));
                                                if ( ! this->containsAddress((void*)location) )
                                                        dyld::throwf("external reloc %p not in mapped image %s\n", (void*)location, this->getPath());
                                                uintptr_t value = *location;
                                                bool symbolAddrCached = true;
                                        #if __i386__
                                                if ( reloc->r_pcrel ) {
                                                        value += (uintptr_t)location + 4 - fSlide;
                                                }
                                        #endif
                                                if ( prebound ) {
                                                        // we are doing relocations, so prebinding was not usable
                                                        // in a prebound executable, the n_value field of an undefined symbol is set to the address where the symbol was found when prebound
                                                        // so, subtracting that gives the initial displacement which we need to add to the newly found symbol address
                                                        // if mach-o relocation structs had an "addend" field this complication would not be necessary.
                                                        if ( ((undefinedSymbol->n_type & N_TYPE) == N_SECT) && ((undefinedSymbol->n_desc & N_WEAK_DEF) != 0) ) {
                                                                // weak symbols need special casing, since *location may have been prebound to a definition in another image.
                                                                // If *location is currently prebound to somewhere in the same section as the weak definition, we assume 
                                                                // that we can subtract off the weak symbol address to get the addend.
                                                                // If prebound elsewhere, we've lost the addend and have to assume it is zero.
                                                                // The prebinding to elsewhere only happens with 10.4+ update_prebinding which only operates on a small set of Apple dylibs
                                                                if ( (value == undefinedSymbol->n_value) || this->isAddrInSection(value, undefinedSymbol->n_sect) ) {
                                                                        value -= undefinedSymbol->n_value;
                        #if __arm__
                                    // if weak and thumb subtract off extra thumb bit
                                    if ( (undefinedSymbol->n_desc & N_ARM_THUMB_DEF) != 0 )
                                        value -= 1;
                        #endif
                                                                }
                                                                else
                                                                        value = 0;
                                                        } 
                                        #if __arm__
                                                        else if ( ((undefinedSymbol->n_type & N_TYPE) == N_SECT) && ((undefinedSymbol->n_desc & N_ARM_THUMB_DEF) != 0) ) {
                                                                // it was prebound to a defined symbol for thumb code in the same linkage unit
                                                                // we need to subtract off one to get real addend
                                                                value -= (undefinedSymbol->n_value+1);
                                                        }
                                        #endif
                                                        else {
                                                                // is undefined or non-weak symbol, so do subtraction to get addend
                                                                value -= undefinedSymbol->n_value;
                                                        }
                                                }
                                                // if undefinedSymbol is same as last time, then symbolAddr and image will resolve to the same too
                                                if ( undefinedSymbol != lastUndefinedSymbol ) {
                                                        bool dontCoalesce = true;
                                                        if ( symbolIsWeakReference(undefinedSymbol) ) { 
                                                                // when weakbind() is run on a classic mach-o encoding, it won't try
                                                                // to coalesce N_REF_TO_WEAK symbols because they are not in the sorted
                                                                // range of global symbols.  To handle that case we do the coalesing now.
                                                                dontCoalesce = false;
                                                        }
                                                        symbolAddr = this->resolveUndefined(context, undefinedSymbol, twoLevel, dontCoalesce, false, &image);
                                                        lastUndefinedSymbol = undefinedSymbol;
                                                        symbolAddrCached = false;
                                                }
                                                if ( context.verboseBind && (undefinedSymbol != NULL) ) {
                                                        const char *path = NULL;
                                                        if ( image != NULL ) {
                                                                path = image->getShortName();
                                                        }
                                                        const char* cachedString = "(cached)";
                                                        if ( !symbolAddrCached ) 
                                                                cachedString = "";
                                                        if ( value == 0 ) {
                                                                dyld::log("dyld: bind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX%s\n",
                                                                                this->getShortName(), (uintptr_t)location,
                                                                                path, &fStrings[undefinedSymbol->n_un.n_strx], (uintptr_t)location, symbolAddr, cachedString);
                                                        }
                                                        else {
                                                                dyld::log("dyld: bind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX%s + %ld\n",
                                                                                this->getShortName(), (uintptr_t)location,
                                                                                path, &fStrings[undefinedSymbol->n_un.n_strx], (uintptr_t)location, symbolAddr, cachedString, value);
                                                        }
                                                }
                                                value += symbolAddr;
                                        #if __i386__
                                                if ( reloc->r_pcrel ) {
                                                        *location = value - ((uintptr_t)location + 4);
                                                }
                                                else {
                                                        // don't dirty page if prebound value was correct
                                                        if ( !prebound || (*location != value) )
                                                                *location = value; 
                                                }
                                        #else
                                                // don't dirty page if prebound value was correct
                                                if ( !prebound || (*location != value) )
                                                        *location = value; 
                                        #endif
                                                // update stats
                                                ++fgTotalBindFixups;
                                        }
                                        break;
                                default:
                                        throw "unknown external relocation type";
                        }
                }
                else {
                        throw "bad external relocation length";
                }
        }
        
#if TEXT_RELOC_SUPPORT
        // if there were __TEXT fixups, restore write protection
        if ( fTextSegmentBinds ) {
                this->makeTextSegmentWritable(context, true);
        }
#endif
}



uintptr_t ImageLoaderMachOClassic::bindIndirectSymbol(uintptr_t* ptrToBind, const struct macho_section* sect, const char* symbolName, uintptr_t targetAddr, const ImageLoader* targetImage, const LinkContext& context)
{
        if ( context.verboseBind ) {
                const char* path = NULL;
                if ( targetImage != NULL )
                        path = targetImage->getShortName();
                dyld::log("dyld: bind indirect sym: %s:%s$%s = %s:%s, *0x%08lx = 0x%08lx\n",
                                this->getShortName(), symbolName, (((sect->flags & SECTION_TYPE)==S_NON_LAZY_SYMBOL_POINTERS) ? "non_lazy_ptr" : "lazy_ptr"),
                                ((path != NULL) ? path : "<weak_import-not-found>"), symbolName, (uintptr_t)ptrToBind, targetAddr);
        }
        if ( context.bindingHandler != NULL ) {
                const char* path = NULL;
                if ( targetImage != NULL )
                        path = targetImage->getShortName();
                targetAddr = (uintptr_t)context.bindingHandler(path, symbolName, (void *)targetAddr);
        }
#if __i386__
        // i386 has special self-modifying stubs that change from "CALL rel32" to "JMP rel32"
        if ( ((sect->flags & SECTION_TYPE) == S_SYMBOL_STUBS) && ((sect->flags & S_ATTR_SELF_MODIFYING_CODE) != 0) && (sect->reserved2 == 5) ) {
                uint32_t rel32 = targetAddr - (((uint32_t)ptrToBind)+5);
                // re-write instruction in a thread-safe manner
                // use 8-byte compare-and-swap to alter 5-byte jump table entries
                // loop is required in case the extra three bytes that cover the next entry are altered by another thread
                bool done = false;
                while ( !done ) {
                        volatile int64_t* jumpPtr = (int64_t*)ptrToBind;
                        int pad = 0;
                        // By default the three extra bytes swapped follow the 5-byte JMP.
                        // But, if the 5-byte jump is up against the end of the __IMPORT segment
                        // We don't want to access bytes off the end of the segment, so we shift
                        // the extra bytes to precede the 5-byte JMP.
                        if ( (((uint32_t)ptrToBind + 8) & 0x00000FFC) == 0x00000000 ) {
                                jumpPtr = (int64_t*)((uint32_t)ptrToBind - 3);
                                pad = 3;
                        }
                        int64_t oldEntry = *jumpPtr;
                        union {
                                int64_t int64;
                                uint8_t bytes[8];
                        } newEntry;
                        newEntry.int64 = oldEntry;
                        newEntry.bytes[pad+0] = 0xE9; // JMP rel32
                        newEntry.bytes[pad+1] = rel32 & 0xFF;
                        newEntry.bytes[pad+2] = (rel32 >> 8) & 0xFF;
                        newEntry.bytes[pad+3] = (rel32 >> 16) & 0xFF;
                        newEntry.bytes[pad+4] = (rel32 >> 24) & 0xFF;
                        done = OSAtomicCompareAndSwap64Barrier(oldEntry, newEntry.int64, (int64_t*)jumpPtr);
                }
        }
        else
#endif
        *ptrToBind = targetAddr;
        return targetAddr;
}

uintptr_t ImageLoaderMachOClassic::doBindFastLazySymbol(uint32_t lazyBindingInfoOffset, const LinkContext& context, void (*lock)(), void (*unlock)())
{
        throw "compressed LINKEDIT lazy binder called with classic LINKEDIT";
}

uintptr_t ImageLoaderMachOClassic::doBindLazySymbol(uintptr_t* lazyPointer, const LinkContext& context)
{
        // scan for all lazy-pointer sections
        const bool twoLevel = this->usesTwoLevelNameSpace();
        const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
        const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
        const struct load_command* cmd = cmds;
        const uint32_t* const indirectTable = (uint32_t*)&fLinkEditBase[fDynamicInfo->indirectsymoff];
        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;
                                        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) {
                                                const uint8_t type = sect->flags & SECTION_TYPE;
                                                uint32_t symbolIndex = INDIRECT_SYMBOL_LOCAL;
                                                if ( type == S_LAZY_SYMBOL_POINTERS ) {
                                                        const size_t pointerCount = sect->size / sizeof(uintptr_t);
                                                        uintptr_t* const symbolPointers = (uintptr_t*)(sect->addr + fSlide);
                                                        if ( (lazyPointer >= symbolPointers) && (lazyPointer < &symbolPointers[pointerCount]) ) {
                                                                const uint32_t indirectTableOffset = sect->reserved1;
                                                                const size_t lazyIndex = lazyPointer - symbolPointers;
                                                                symbolIndex = indirectTable[indirectTableOffset + lazyIndex];
                                                        }
                                                }
                                        #if __i386__
                                                else if ( (type == S_SYMBOL_STUBS) && (sect->flags & S_ATTR_SELF_MODIFYING_CODE) && (sect->reserved2 == 5) ) {
                                                        // 5 bytes stubs on i386 are new "fast stubs"
                                                        uint8_t* const jmpTableBase = (uint8_t*)(sect->addr + fSlide);
                                                        uint8_t* const jmpTableEnd = jmpTableBase + sect->size;
                                                        // initial CALL instruction in jump table leaves pointer to next entry, so back up
                                                        uint8_t* const jmpTableEntryToPatch = ((uint8_t*)lazyPointer) - 5;  
                                                        lazyPointer = (uintptr_t*)jmpTableEntryToPatch; 
                                                        if ( (jmpTableEntryToPatch >= jmpTableBase) && (jmpTableEntryToPatch < jmpTableEnd) ) {
                                                                const uint32_t indirectTableOffset = sect->reserved1;
                                                                const uint32_t entryIndex = (jmpTableEntryToPatch - jmpTableBase)/5;
                                                                symbolIndex = indirectTable[indirectTableOffset + entryIndex];
                                                        }
                                                }
                                        #endif
                                                if ( symbolIndex != INDIRECT_SYMBOL_ABS && symbolIndex != INDIRECT_SYMBOL_LOCAL ) {
                                                        const char* symbolName = &fStrings[fSymbolTable[symbolIndex].n_un.n_strx];
                                                        const ImageLoader* image = NULL;
                                                        uintptr_t symbolAddr = this->resolveUndefined(context, &fSymbolTable[symbolIndex], twoLevel, false, true, &image);
                                                        symbolAddr = this->bindIndirectSymbol(lazyPointer, sect, symbolName, symbolAddr, image,  context);
                                                        ++fgTotalLazyBindFixups;
                                                        return symbolAddr;
                                                }
                                        }
                                }
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        dyld::throwf("lazy pointer not found at address %p in image %s", lazyPointer, this->getPath());
}



void ImageLoaderMachOClassic::initializeCoalIterator(CoalIterator& it, unsigned int loadOrder, unsigned)
{
        it.image = this;
        it.symbolName = " ";
        it.loadOrder = loadOrder;
        it.weakSymbol = false;
        it.symbolMatches = false;
        it.done = false;
        it.type = 0; 
        if ( fDynamicInfo->tocoff != 0 ) {
                it.curIndex = 0;
                it.endIndex = fDynamicInfo->ntoc;
        }
        else {
                it.curIndex = 0;
                it.endIndex = fDynamicInfo->nextdefsym;
        }
}


bool ImageLoaderMachOClassic::incrementCoalIterator(CoalIterator& it)
{
        if ( it.done )
                return false;
                
        if ( fDynamicInfo->tocoff != 0 ) {
                if ( it.curIndex >= fDynamicInfo->ntoc ) {
                        it.done = true;
                        it.symbolName = "~~~";
                        return true;
                }
                else {
                        const dylib_table_of_contents* toc = (dylib_table_of_contents*)&fLinkEditBase[fDynamicInfo->tocoff];
                        const uint32_t index = toc[it.curIndex].symbol_index;
                        const struct macho_nlist* sym = &fSymbolTable[index];
                        const char* symStr = &fStrings[sym->n_un.n_strx];
                        it.symbolName = symStr;
                        it.weakSymbol = (sym->n_desc & N_WEAK_DEF);
                        it.symbolMatches = false;
                        it.type = 0; // clear flag that says we applied updates for this symbol
                        //dyld::log("incrementCoalIterator() curIndex=%ld, symbolName=%s in %s\n", it.curIndex, symStr, this->getPath());
                        it.curIndex++;
                        return false;
                }
        }
        else {
                if ( it.curIndex >= fDynamicInfo->nextdefsym ) {
                        it.done = true;
                        it.symbolName = "~~~";
                        return true;
                }
                else {
                        const struct macho_nlist* sym = &fSymbolTable[fDynamicInfo->iextdefsym+it.curIndex];
                        const char* symStr = &fStrings[sym->n_un.n_strx];
                        it.symbolName = symStr;
                        it.weakSymbol = (sym->n_desc & N_WEAK_DEF);
                        it.symbolMatches = false;
                        it.type = 0; // clear flag that says we applied updates for this symbol
                        //dyld::log("incrementCoalIterator() curIndex=%ld, symbolName=%s in %s\n", it.curIndex, symStr, this->getPath());
                        it.curIndex++;
                        return false;
                }
        }       
        
        return false;
}

uintptr_t ImageLoaderMachOClassic::getAddressCoalIterator(CoalIterator& it, const LinkContext& context)
{
        uint32_t symbol_index = 0;
        if ( fDynamicInfo->tocoff != 0 ) {
                const dylib_table_of_contents* toc = (dylib_table_of_contents*)&fLinkEditBase[fDynamicInfo->tocoff];
                symbol_index = toc[it.curIndex-1].symbol_index;
        }
        else {
                symbol_index = fDynamicInfo->iextdefsym + (uint32_t)it.curIndex - 1;
        }       
        const struct macho_nlist* sym = &fSymbolTable[symbol_index];
        //dyld::log("getAddressCoalIterator() => 0x%llX, %s symbol_index=%d, in %s\n", (uint64_t)(sym->n_value + fSlide), &fStrings[sym->n_un.n_strx], symbol_index, this->getPath());
#if __arm__
                // processor assumes code address with low bit set is thumb
                if (sym->n_desc & N_ARM_THUMB_DEF)
                        return (sym->n_value | 1) + fSlide ;
                else
                        return sym->n_value + fSlide;
#else
        return sym->n_value + fSlide;
#endif
}


void ImageLoaderMachOClassic::updateUsesCoalIterator(CoalIterator& it, uintptr_t value, ImageLoader* targetImage, unsigned targetIndex, const LinkContext& context)
{
        // flat_namespace images with classic LINKEDIT do not need late coalescing.
        // They still need to be iterated becuase they may implement
        // something needed by other coalescing images.
        // But they need no updating because during the bind phase every symbol lookup is a full scan.
        if ( !this->usesTwoLevelNameSpace() )
                return;
                
        // <rdar://problem/6570879> weak binding done too early with inserted libraries
        if ( this->getState() < dyld_image_state_bound  )
                return;

        uint32_t symbol_index = 0;
        if ( fDynamicInfo->tocoff != 0 ) {
                const dylib_table_of_contents* toc = (dylib_table_of_contents*)&fLinkEditBase[fDynamicInfo->tocoff];
                symbol_index = toc[it.curIndex-1].symbol_index;
        }
        else {
                symbol_index = fDynamicInfo->iextdefsym + (uint32_t)it.curIndex - 1;
        }       

        // if this image's copy of the symbol is not a weak definition nor a weak reference then nothing to coalesce here
        if ( !symbolIsWeakReference(&fSymbolTable[symbol_index]) && !symbolIsWeakDefinition(&fSymbolTable[symbol_index]) ) {
                return;
        }

        // <rdar://problem/6555720> malformed dylib with duplicate weak symbols causes re-binding
        if ( it.type ) 
                return;

        bool boundSomething = false;
        // scan external relocations for uses of symbol_index
        const uintptr_t relocBase = this->getRelocBase();
        const bool prebound = this->isPrebindable();
        const relocation_info* const relocsStart = (struct relocation_info*)(&fLinkEditBase[fDynamicInfo->extreloff]);
        const relocation_info* const relocsEnd = &relocsStart[fDynamicInfo->nextrel];
        for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
                if ( reloc->r_symbolnum == symbol_index ) {
                        //dyld::log("found external reloc using symbol_index=%d in %s\n",symbol_index, this->getPath());
                        const struct macho_nlist* undefinedSymbol = &fSymbolTable[reloc->r_symbolnum];
                        const char* symbolName = &fStrings[undefinedSymbol->n_un.n_strx];
                        uintptr_t* location = ((uintptr_t*)(reloc->r_address + relocBase));
                        const uintptr_t initialValue = *location;
                        uintptr_t addend = 0;
                        if ( prebound ) {
                                // we are doing relocations, so prebinding was not usable
                                // in a prebound executable, the n_value field of an undefined symbol is set to the address where the symbol was found when prebound
                                // so, subtracting that gives the initial displacement which we need to add to the newly found symbol address
                                // if mach-o relocation structs had an "addend" field this complication would not be necessary.
                                if ( ((undefinedSymbol->n_type & N_TYPE) == N_SECT) && ((undefinedSymbol->n_desc & N_WEAK_DEF) != 0) ) {
                                        // weak symbols need special casing, since *location may have been prebound to a definition in another image.
                                        // If *location is currently prebound to somewhere in the same section as the weak definition, we assume 
                                        // that we can subtract off the weak symbol address to get the addend.
                                        // If prebound elsewhere, we've lost the addend and have to assume it is zero.
                                        // The prebinding to elsewhere only happens with 10.4+ update_prebinding which only operates on a small set of Apple dylibs
                                        if ( (initialValue == undefinedSymbol->n_value) || this->isAddrInSection(initialValue, undefinedSymbol->n_sect) ) {
                                                addend = initialValue - undefinedSymbol->n_value;
                        #if __arm__
                                                // if weak and thumb subtract off extra thumb bit
                                                if ( (undefinedSymbol->n_desc & N_ARM_THUMB_DEF) != 0 )
                                                        addend &= -2;
                        #endif
                                        }
                                } 
                #if __arm__
                                else if ( ((undefinedSymbol->n_type & N_TYPE) == N_SECT) && ((undefinedSymbol->n_desc & N_ARM_THUMB_DEF) != 0) ) {
                                        // it was prebound to a defined symbol for thumb code in the same linkage unit
                                        // we need to subtract off one to get real addend
                                        addend = initialValue - (undefinedSymbol->n_value+1);
                                }
                #endif
                                else {
                                        // is undefined or non-weak symbol, so do subtraction to get addend
                                        addend = initialValue - undefinedSymbol->n_value;
                                }
                        }
                        else {
                                // non-prebound case
                                if ( ((undefinedSymbol->n_type & N_TYPE) == N_SECT) && ((undefinedSymbol->n_desc & N_WEAK_DEF) != 0) ) {
                                        // if target is weak-def in same linkage unit, then bind phase has already set initialValue 
                                        // to be definition address plus addend
                                        //dyld::log("weak def, initialValue=0x%lX, undefAddr=0x%lX\n", initialValue, undefinedSymbol->n_value+fSlide);
                                        addend = initialValue - (undefinedSymbol->n_value + fSlide);
                #if __arm__
                                        // if weak and thumb subtract off extra thumb bit
                                        if ( (undefinedSymbol->n_desc & N_ARM_THUMB_DEF) != 0 )
                                                addend &= -2;
                #endif
                                }
                                else {
                                        // nothing fixed up yet, addend is just initial value
                                        //dyld::log("addend=0x%lX\n", initialValue);
                                        addend = initialValue;
                                }
                        }
                        
                        uint8_t type = BIND_TYPE_POINTER;
                #if __i386__
                        if ( reloc->r_pcrel ) 
                                type = BIND_TYPE_TEXT_PCREL32;
                #endif
                        this->bindLocation(context, this->imageBaseAddress(), (uintptr_t)location, value, type, symbolName, addend, this->getPath(), targetImage ? targetImage->getPath() : NULL, "weak ", NULL, fSlide);
                        boundSomething = true;
                }
        }

        // scan lazy and non-lazy pointers for uses of symbol_index
        const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
        const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
        const struct load_command* cmd = cmds;
        const uint32_t* const indirectTable = (uint32_t*)&fLinkEditBase[fDynamicInfo->indirectsymoff];
        for (uint32_t i = 0; i < cmd_count; ++i) {
                if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
                        const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                        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) {
                                uint32_t elementSize = sizeof(uintptr_t);
                                switch ( sect->flags & SECTION_TYPE ) {
                                #if __i386__
                                        case S_SYMBOL_STUBS:
                                                if ( ((sect->flags & S_ATTR_SELF_MODIFYING_CODE) ==0) || (sect->reserved2 != 5) )
                                                        continue;
                                                elementSize = 5;
                        [[clang::fallthrough]];
                                #endif
                                        case S_NON_LAZY_SYMBOL_POINTERS:
                                        case S_LAZY_SYMBOL_POINTERS:
                                        {
                                                size_t elementCount = sect->size / elementSize;
                                                const uint32_t indirectTableOffset = sect->reserved1;
                                                uint8_t* ptrToBind = (uint8_t*)(sect->addr + fSlide);
                                                //dyld::log(" scanning section %s of %s starting at %p\n", sect->sectname, this->getShortName(), ptrToBind);
                                                for (size_t j=0; j < elementCount; ++j, ptrToBind += elementSize) {
                                                        if ( indirectTable[indirectTableOffset + j] == symbol_index ) {
                                                                //dyld::log("  found symbol index match at %d/%d, ptrToBind=%p\n", j, elementCount, ptrToBind);
                                                                // update pointer
                                                                this->bindIndirectSymbol((uintptr_t*)ptrToBind, sect, it.symbolName, value, targetImage, context);
                                                                boundSomething = true;
                                                        }
                                                }
                                        }
                                        break;
                                }
                        }
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        if ( boundSomething && (targetImage != this) ) {
                context.addDynamicReference(this, targetImage);
        }
        
        // mark that this symbol has already been bound, so we don't try to bind again
        it.type = 1;
}


void ImageLoaderMachOClassic::bindIndirectSymbolPointers(const LinkContext& context, bool bindNonLazys, bool bindLazys)
{
        // scan for all non-lazy-pointer sections 
        const bool twoLevel = this->usesTwoLevelNameSpace();
        const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
        const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
        const struct load_command* cmd = cmds;
        const uint32_t* const indirectTable = (uint32_t*)&fLinkEditBase[fDynamicInfo->indirectsymoff];
        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;
                                        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) {
                                                bool isLazySymbol = false;
                                                const uint8_t type = sect->flags & SECTION_TYPE;
                                                uint32_t elementSize = sizeof(uintptr_t);
                                                size_t elementCount = sect->size / elementSize;
                                                if ( type == S_NON_LAZY_SYMBOL_POINTERS ) {
                                                        if ( ! bindNonLazys )
                                                                continue;
                                                }
                                                else if ( type == S_LAZY_SYMBOL_POINTERS ) {
                                                        // process each symbol pointer in this section
                                                        fgTotalPossibleLazyBindFixups += elementCount;
                                                        isLazySymbol = true;
                                                        if ( ! bindLazys )
                                                                continue;
                                                }
                                #if __i386__
                                                else if ( (type == S_SYMBOL_STUBS) && (sect->flags & S_ATTR_SELF_MODIFYING_CODE) && (sect->reserved2 == 5) ) {
                                                        // process each jmp entry in this section
                                                        elementCount = sect->size / 5;
                                                        elementSize = 5;
                                                        fgTotalPossibleLazyBindFixups += elementCount;
                                                        isLazySymbol = true;
                                                        if ( ! bindLazys )
                                                                continue;
                                                }
                                #endif
                                                else {
                                                        continue;
                                                }
                                                const uint32_t indirectTableOffset = sect->reserved1;
                                                uint8_t* ptrToBind = (uint8_t*)(sect->addr + fSlide);
                                                for (size_t j=0; j < elementCount; ++j, ptrToBind += elementSize) {
                                #if LINKEDIT_USAGE_DEBUG
                                                        noteAccessedLinkEditAddress(&indirectTable[indirectTableOffset + j]);
                                #endif
                                                        uint32_t symbolIndex = indirectTable[indirectTableOffset + j];
                                                        if ( symbolIndex == INDIRECT_SYMBOL_LOCAL) {
                                                                *((uintptr_t*)ptrToBind) += this->fSlide;
                                                        }
                                                        else if ( symbolIndex == INDIRECT_SYMBOL_ABS) {
                                                                // do nothing since already has absolute address
                                                        }
                                                        else {
                                                                const struct macho_nlist* sym = &fSymbolTable[symbolIndex];
                                                                if ( symbolIndex == 0 ) {
                                                                        // This could be rdar://problem/3534709 
                                                                        if ( ((const macho_header*)fMachOData)->filetype == MH_EXECUTE ) {
                                                                                static bool alreadyWarned = false;
                                                                                if ( (sym->n_type & N_TYPE) != N_UNDF ) {
                                                                                        // The indirect table parallels the (non)lazy pointer sections.  For
                                                                                        // instance, to find info about the fifth lazy pointer you look at the
                                                                                        // fifth entry in the indirect table.  (try otool -Iv on a file).
                                                                                        // The entry in the indirect table contains an index into the symbol table.

                                                                                        // The bug in ld caused the entry in the indirect table to be zero
                                                                                        // (instead of a magic value that means a local symbol).  So, if the
                                                                                        // symbolIndex == 0, we may be encountering the bug, or 0 may be a valid
                                                                                        // symbol table index. The check I put in place is to see if the zero'th
                                                                                        // symbol table entry is an import entry (usually it is a local symbol
                                                                                        // definition).
                                                                                        if ( context.verboseWarnings && !alreadyWarned ) {
                                                                                                dyld::log("dyld: malformed executable '%s', skipping indirect symbol to %s\n",
                                                                                                                this->getPath(), &fStrings[sym->n_un.n_strx]);
                                                                                                alreadyWarned = true;
                                                                                        }
                                                                                        continue;
                                                                                }
                                                                        }
                                                                }
                                                                const ImageLoader* image = NULL;
                                                                // let weak definitions resolve to themselves, later coalescing may overwrite them
                                                                bool dontCoalesce = true;
                                                                if ( bindLazys && isLazySymbol ) {
                                                                        // if this is something normally lazy bound, but we are forcing
                                                                        // it to be bound now, do coalescing
                                                                        dontCoalesce = false;
                                                                }
                                                                if ( symbolIsWeakReference(sym) ) { 
                                                                        // when weakbind() is run on a classic mach-o encoding, it won't try
                                                                        // to coalesce N_REF_TO_WEAK symbols because they are not in the sorted
                                                                        // range of global symbols.  To handle that case we do the coalesing now.
                                                                        dontCoalesce = false;
                                                                }
                                                                uintptr_t symbolAddr = resolveUndefined(context, sym, twoLevel, dontCoalesce, false, &image);
                                                                // update pointer
                                                                this->bindIndirectSymbol((uintptr_t*)ptrToBind, sect, &fStrings[sym->n_un.n_strx], symbolAddr, image,  context);
                                                                // update stats
                                                                ++fgTotalBindFixups;
                                                        }
                                                }
                                        }
                                }
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
}



#if __i386__
void ImageLoaderMachOClassic::initializeLazyStubs(const LinkContext& context)
{
        if ( ! this->usablePrebinding(context) ) {
                // reset all "fast" stubs
                const macho_header* mh = (macho_header*)fMachOData;
                const uint32_t cmd_count = mh->ncmds;
                const struct load_command* const cmds = (struct load_command*)&fMachOData[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;
                                        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) {
                                                const uint8_t type = sect->flags & SECTION_TYPE;
                                                if ( (type == S_SYMBOL_STUBS) && (sect->flags & S_ATTR_SELF_MODIFYING_CODE) && (sect->reserved2 == 5) ) {
                                                        // reset each jmp entry in this section
                                                        const uint32_t indirectTableOffset = sect->reserved1;
                                                        const uint32_t* const indirectTable = (uint32_t*)&fLinkEditBase[fDynamicInfo->indirectsymoff];
                                                        uint8_t* start = (uint8_t*)(sect->addr + this->fSlide);
                                                        uint8_t* end = start + sect->size;
                                                        uintptr_t dyldHandler = (uintptr_t)&stub_binding_helper_i386_old;
                                                        uint32_t entryIndex = 0;
                                                        for (uint8_t* entry = start; entry < end; entry += 5, ++entryIndex) {
                                                                bool installLazyHandler = true;
                                                                // jump table entries that cross a (64-byte) cache line boundary have the potential to cause crashes
                                                                // if the instruction is updated by one thread while being executed by another
                                                                if ( ((uint32_t)entry & 0xFFFFFFC0) != ((uint32_t)entry+4 & 0xFFFFFFC0) ) {
                                                                        // need to bind this now to avoid a potential problem if bound lazily
                                                                        uint32_t symbolIndex = indirectTable[indirectTableOffset + entryIndex];
                                                                        // the latest linker marks 64-byte crossing stubs with INDIRECT_SYMBOL_ABS so they are not used
                                                                        if ( symbolIndex != INDIRECT_SYMBOL_ABS ) {
                                                                                const char* symbolName = &fStrings[fSymbolTable[symbolIndex].n_un.n_strx];
                                                                                const ImageLoader* image = NULL;
                                                                                try {
                                                                                        uintptr_t symbolAddr = this->resolveUndefined(context, &fSymbolTable[symbolIndex], this->usesTwoLevelNameSpace(), false, false, &image);
                                                                                        symbolAddr = this->bindIndirectSymbol((uintptr_t*)entry, sect, symbolName, symbolAddr, image, context);
                                                                                        ++fgTotalBindFixups;
                                                                                        uint32_t rel32 = symbolAddr - (((uint32_t)entry)+5);
                                                                                        entry[0] = 0xE9; // JMP rel32
                                                                                        entry[1] = rel32 & 0xFF;
                                                                                        entry[2] = (rel32 >> 8) & 0xFF;
                                                                                        entry[3] = (rel32 >> 16) & 0xFF;
                                                                                        entry[4] = (rel32 >> 24) & 0xFF;
                                                                                        installLazyHandler = false;
                                                                                } 
                                                                                catch (const char* msg) {
                                                                                        // ignore errors when binding symbols early
                                                                                        // maybe the function is never called, and therefore erroring out now would be a regression
                                                                                }
                                                                        }
                                                                }
                                                                if ( installLazyHandler ) {
                                                                        uint32_t rel32 = dyldHandler - (((uint32_t)entry)+5);
                                                                        entry[0] = 0xE8; // CALL rel32
                                                                        entry[1] = rel32 & 0xFF;
                                                                        entry[2] = (rel32 >> 8) & 0xFF;
                                                                        entry[3] = (rel32 >> 16) & 0xFF;
                                                                        entry[4] = (rel32 >> 24) & 0xFF;
                                                                }
                                                        }
                                                }
                                        }
                                }
                        }
                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                }
        }
}
#endif // __i386__


void ImageLoaderMachOClassic::doBind(const LinkContext& context, bool forceLazysBound, const ImageLoader* reExportParent)
{
        CRSetCrashLogMessage2(this->getPath());
#if __i386__
        this->initializeLazyStubs(context);
#endif

        // if prebound and loaded at prebound address, and all libraries are same as when this was prebound, then no need to bind
        // note: flat-namespace binaries need to have imports rebound (even if correctly prebound)
        if ( this->usablePrebinding(context) ) {
                // binding already up to date
        }
        else {
                // no valid prebinding, so bind symbols.
                // values bound by name are stored two different ways in classic mach-o:
                
        #if TEXT_RELOC_SUPPORT
                // if there are __TEXT fixups, temporarily make __TEXT writable
                if ( fTextSegmentBinds ) 
                        this->makeTextSegmentWritable(context, true);
        #endif

                // 1) external relocations are used for data initialized to external symbols
                this->doBindExternalRelocations(context);
                
                // 2) "indirect symbols" are used for code references to external symbols
                // if this image is in the shared cache, there is no way to reset the lazy pointers, so bind them now
                this->bindIndirectSymbolPointers(context, true, forceLazysBound || fInSharedCache);

        #if TEXT_RELOC_SUPPORT
                // if there were __TEXT fixups, restore write protection
                if ( fTextSegmentBinds ) 
                        this->makeTextSegmentWritable(context, false);
        #endif  
        }
        
        // set up dyld entry points in image
        this->setupLazyPointerHandler(context);
        
        CRSetCrashLogMessage2(NULL);
}

void ImageLoaderMachOClassic::doBindJustLazies(const LinkContext& context)
{
        // some API called requested that all lazy pointers in this image be force bound
        this->bindIndirectSymbolPointers(context, false, true);
}

void ImageLoaderMachOClassic::doInterpose(const LinkContext& context)
{
        if ( context.verboseInterposing )
                dyld::log("dyld: interposing %lu tuples onto: %s\n", fgInterposingTuples.size(), this->getPath());

        // scan indirect symbols
        const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
        const struct load_command* const cmds = (struct load_command*)&fMachOData[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;
                                        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) {
                                                const uint8_t type = sect->flags & SECTION_TYPE;
                                                if ( (type == S_NON_LAZY_SYMBOL_POINTERS) || (type == S_LAZY_SYMBOL_POINTERS) ) {
                                                        const size_t pointerCount = sect->size / sizeof(uintptr_t);
                                                        uintptr_t* const symbolPointers = (uintptr_t*)(sect->addr + fSlide);
                                                        for (size_t pointerIndex=0; pointerIndex < pointerCount; ++pointerIndex) {
                                                                uintptr_t newValue = interposedAddress(context, symbolPointers[pointerIndex], this);
                                                                if ( newValue != symbolPointers[pointerIndex] )
                                                                        symbolPointers[pointerIndex] = newValue;
                                                        }
                                                }
                                #if __i386__
                                                // i386 has special self-modifying stubs that might be prebound to "JMP rel32" that need checking
                                                else if ( (type == S_SYMBOL_STUBS) && ((sect->flags & S_ATTR_SELF_MODIFYING_CODE) != 0) && (sect->reserved2 == 5) ) {
                                                        // check each jmp entry in this section
                                                        uint8_t* start = (uint8_t*)(sect->addr + this->fSlide);
                                                        uint8_t* end = start + sect->size;
                                                        for (uint8_t* entry = start; entry < end; entry += 5) {
                                                                if ( entry[0] == 0xE9 ) { // 0xE9 == JMP 
                                                                        uint32_t rel32 = *((uint32_t*)&entry[1]); // assume unaligned load of uint32_t is ok
                                                                        uint32_t target = (uint32_t)&entry[5] + rel32;
                                                                        uint32_t newTarget = interposedAddress(context, target, this);
                                                                        if ( newTarget != target ) {
                                                                                uint32_t newRel32 = newTarget - (uint32_t)&entry[5];
                                                                                *((uint32_t*)&entry[1]) = newRel32; // assume unaligned store of uint32_t is ok
                                                                        }
                                                                }
                                                        }
                                                }
                                #endif
                                        }
                                }
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        
        // scan external relocations 
        const uintptr_t relocBase = this->getRelocBase();
        const relocation_info* const relocsStart = (struct relocation_info*)(&fLinkEditBase[fDynamicInfo->extreloff]);
        const relocation_info* const relocsEnd = &relocsStart[fDynamicInfo->nextrel];
        for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
                if (reloc->r_length == RELOC_SIZE) {
                        switch(reloc->r_type) {
                                case POINTER_RELOC:
                                        {
                                                uintptr_t* location = ((uintptr_t*)(reloc->r_address + relocBase));
                                                uintptr_t value = *location;
                                                uintptr_t newValue = interposedAddress(context, value, this);
                                                if ( newValue != value )
                                                        *location = newValue;
                                        }
                                        break;
                        }
                }
        }
}

void ImageLoaderMachOClassic::dynamicInterpose(const LinkContext& context) 
{
        if ( context.verboseInterposing )
                dyld::log("dyld: dynamic interposing %lu tuples onto image: %s\n", context.dynamicInterposeCount, this->getPath());

        // scan indirect symbols
        const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
        const struct load_command* const cmds = (struct load_command*)&fMachOData[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;
                                        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) {
                                                const uint8_t type = sect->flags & SECTION_TYPE;
                                                if ( (type == S_NON_LAZY_SYMBOL_POINTERS) || (type == S_LAZY_SYMBOL_POINTERS) ) {
                                                        const size_t pointerCount = sect->size / sizeof(uintptr_t);
                                                        uintptr_t* const symbolPointers = (uintptr_t*)(sect->addr + fSlide);
                                                        for (size_t pointerIndex=0; pointerIndex < pointerCount; ++pointerIndex) {
                                                                for(size_t j=0; j < context.dynamicInterposeCount; ++j) {
                                                                        // replace all references to 'replacee' with 'replacement'
                                                                        if ( symbolPointers[pointerIndex] == (uintptr_t)context.dynamicInterposeArray[j].replacee ) {
                                                                                if ( context.verboseInterposing ) {
                                                                                        dyld::log("dyld: dynamic interposing: at %p replace %p with %p in %s\n", 
                                                                                                &symbolPointers[pointerIndex], context.dynamicInterposeArray[j].replacee, context.dynamicInterposeArray[j].replacement, this->getPath());
                                                                                }
                                                                                symbolPointers[pointerIndex] = (uintptr_t)context.dynamicInterposeArray[j].replacement;
                                                                        }
                                                                }
                                                        }
                                                }
                                        }
                                }
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        
        // scan external relocations 
        const uintptr_t relocBase = this->getRelocBase();
        const relocation_info* const relocsStart = (struct relocation_info*)(&fLinkEditBase[fDynamicInfo->extreloff]);
        const relocation_info* const relocsEnd = &relocsStart[fDynamicInfo->nextrel];
        for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
                if (reloc->r_length == RELOC_SIZE) {
                        switch(reloc->r_type) {
                                case POINTER_RELOC:
                                        {
                                                uintptr_t* location = ((uintptr_t*)(reloc->r_address + relocBase));
                                                for(size_t i=0; i < context.dynamicInterposeCount; ++i) {
                                                        // replace all references to 'replacee' with 'replacement'
                                                        if ( *location == (uintptr_t)context.dynamicInterposeArray[i].replacee ) {
                                                                if ( context.verboseInterposing ) {
                                                                        dyld::log("dyld: dynamic interposing: at %p replace %p with %p in %s\n", 
                                                                                location, context.dynamicInterposeArray[i].replacee, context.dynamicInterposeArray[i].replacement, this->getPath());
                                                                }
                                                                *location = (uintptr_t)context.dynamicInterposeArray[i].replacement;
                                                        }
                                                }
                                        }
                                        break;
                        }
                }
        }
}


const char* ImageLoaderMachOClassic::findClosestSymbol(const void* addr, const void** closestAddr) const
{
        uintptr_t targetAddress = (uintptr_t)addr - fSlide;
        const struct macho_nlist* bestSymbol = NULL;
        // first walk all global symbols
        const struct macho_nlist* const globalsStart = &fSymbolTable[fDynamicInfo->iextdefsym];
        const struct macho_nlist* const globalsEnd= &globalsStart[fDynamicInfo->nextdefsym];
        for (const struct macho_nlist* s = globalsStart; s < globalsEnd; ++s) {
                if ( (s->n_type & N_TYPE) == N_SECT ) {
                        if ( bestSymbol == NULL ) {
                                if ( s->n_value <= targetAddress )
                                        bestSymbol = s;
                        }
                        else if ( (s->n_value <= targetAddress) && (bestSymbol->n_value < s->n_value) ) {
                                bestSymbol = s;
                        }
                }
        }
        // next walk all local symbols
        const struct macho_nlist* const localsStart = &fSymbolTable[fDynamicInfo->ilocalsym];
        const struct macho_nlist* const localsEnd= &localsStart[fDynamicInfo->nlocalsym];
        for (const struct macho_nlist* s = localsStart; s < localsEnd; ++s) {
                if ( ((s->n_type & N_TYPE) == N_SECT) && ((s->n_type & N_STAB) == 0) ) {
                        if ( bestSymbol == NULL ) {
                                if ( s->n_value <= targetAddress )
                                        bestSymbol = s;
                        }
                        else if ( (s->n_value <= targetAddress) && (bestSymbol->n_value < s->n_value) ) {
                                bestSymbol = s;
                        }
                }
        }
        if ( bestSymbol != NULL ) {
#if __arm__
                if (bestSymbol->n_desc & N_ARM_THUMB_DEF)
                        *closestAddr = (void*)((bestSymbol->n_value | 1) + fSlide);
                else
                        *closestAddr = (void*)(bestSymbol->n_value + fSlide);
#else
                *closestAddr = (void*)(bestSymbol->n_value + fSlide);
#endif
                return &fStrings[bestSymbol->n_un.n_strx];
        }
        return NULL;
}