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

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2004-2008 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
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 * @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/nlist.h> 
#include <sys/sysctl.h>
#include <libkern/OSAtomic.h>
#include <libkern/OSCacheControl.h>

#include "ImageLoaderMachO.h"
#include "ImageLoaderMachOCompressed.h"
#include "ImageLoaderMachOClassic.h"
#include "mach-o/dyld_images.h"



// relocation_info.r_length field has value 3 for 64-bit executables and value 2 for 32-bit executables
#if __LP64__
        #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 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

uint32_t ImageLoaderMachO::fgSymbolTableBinarySearchs = 0;
uint32_t ImageLoaderMachO::fgSymbolTrieSearchs = 0;


ImageLoaderMachO::ImageLoaderMachO(const macho_header* mh, const char* path, unsigned int segCount, 
                                                                                                                                uint32_t segOffsets[], unsigned int libCount)
 : ImageLoader(path, libCount), fMachOData((uint8_t*)mh), fLinkEditBase(NULL), fSlide(0), 
        fEHFrameSectionOffset(0), fUnwindInfoSectionOffset(0), fDylibIDOffset(0), 
        fSegmentsCount(segCount), fIsSplitSeg(false), fInSharedCache(false),  
#if TEXT_RELOC_SUPPORT
        fTextSegmentRebases(false),
        fTextSegmentBinds(false),
#endif
#if __i386__
        fReadOnlyImportSegment(false),
#endif
        fHasSubLibraries(false), fHasSubUmbrella(false), fInUmbrella(false), fHasDOFSections(false), fHasDashInit(false),
        fHasInitializers(false), fHasTerminators(false)
{
        fIsSplitSeg = ((mh->flags & MH_SPLIT_SEGS) != 0);        

        // construct SegmentMachO object for each LC_SEGMENT cmd using "placement new" to put 
        // each SegmentMachO object in array at end of ImageLoaderMachO object
        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, segIndex=0; i < cmd_count; ++i) {
                if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
                        const struct macho_segment_command* segCmd = (struct macho_segment_command*)cmd;
                        // ignore zero-sized segments
                        if ( segCmd->vmsize != 0 ) {
                                // record offset of load command
                                segOffsets[segIndex++] = (uint8_t*)segCmd - fMachOData;
                        }
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }

}


// determine if this mach-o file has classic or compressed LINKEDIT and number of segments it has
void ImageLoaderMachO::sniffLoadCommands(const macho_header* mh, const char* path, bool* compressed, 
                                                                                        unsigned int* segCount, unsigned int* libCount)
{
        *compressed = false;
        *segCount = 0;
        *libCount = 0;
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds    = (struct load_command*)(((uint8_t*)mh) + sizeof(macho_header));
        const struct load_command* const endCmds = (struct load_command*)(((uint8_t*)mh) + sizeof(macho_header) + mh->sizeofcmds);
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_DYLD_INFO:
                        case LC_DYLD_INFO_ONLY:
                                *compressed = true;
                                break;
                        case LC_SEGMENT_COMMAND:
                                // ignore zero-sized segments
                                if ( ((struct macho_segment_command*)cmd)->vmsize != 0 )
                                        *segCount += 1;
                                break;
                        case LC_LOAD_DYLIB:
                        case LC_LOAD_WEAK_DYLIB:
                        case LC_REEXPORT_DYLIB:
                                *libCount += 1;
                                break;
                }
                uint32_t cmdLength = cmd->cmdsize;
                cmd = (const struct load_command*)(((char*)cmd)+cmdLength);
                if ( cmd > endCmds ) {
                        dyld::throwf("malformed mach-o image: load command #%d length (%u) would exceed sizeofcmds (%u) in %s", 
                                                        i, cmdLength, mh->sizeofcmds, path);
                }
        }
        // fSegmentsArrayCount is only 8-bits
        if ( *segCount > 255 )
                dyld::throwf("malformed mach-o image: more than 255 segments in %s", path);
                
        // fSegmentsArrayCount is only 8-bits
        if ( *libCount > 4095 )
                dyld::throwf("malformed mach-o image: more than 4095 dependent libraries in %s", path);

        if ( needsAddedLibSystemDepency(*libCount, mh) )
                *libCount = 1;
}



// create image for main executable
ImageLoader* ImageLoaderMachO::instantiateMainExecutable(const macho_header* mh, uintptr_t slide, const char* path, const LinkContext& context)
{
        //dyld::log("ImageLoader=%ld, ImageLoaderMachO=%ld, ImageLoaderMachOClassic=%ld, ImageLoaderMachOCompressed=%ld\n",
        //      sizeof(ImageLoader), sizeof(ImageLoaderMachO), sizeof(ImageLoaderMachOClassic), sizeof(ImageLoaderMachOCompressed));
        bool compressed;
        unsigned int segCount;
        unsigned int libCount;
        sniffLoadCommands(mh, path, &compressed, &segCount, &libCount);
        // instantiate concrete class based on content of load commands
        if ( compressed ) 
                return ImageLoaderMachOCompressed::instantiateMainExecutable(mh, slide, path, segCount, libCount, context);
        else
                return ImageLoaderMachOClassic::instantiateMainExecutable(mh, slide, path, segCount, libCount, context);
}


// create image by mapping in a mach-o file
ImageLoader* ImageLoaderMachO::instantiateFromFile(const char* path, int fd, const uint8_t firstPage[4096], uint64_t offsetInFat, 
                                                                        uint64_t lenInFat, const struct stat& info, const LinkContext& context)
{
        // get load commands
        const unsigned int dataSize = sizeof(macho_header) + ((macho_header*)firstPage)->sizeofcmds;
        uint8_t buffer[dataSize];
        const uint8_t* fileData = firstPage;
        if ( dataSize > 4096 ) {
                // only read more if cmds take up more space than first page
                fileData = buffer;
                memcpy(buffer, firstPage, 4096);
                pread(fd, &buffer[4096], dataSize-4096, offsetInFat+4096);
        }

        bool compressed;
        unsigned int segCount;
        unsigned int libCount;
        sniffLoadCommands((const macho_header*)fileData, path, &compressed, &segCount, &libCount);
        // instantiate concrete class based on content of load commands
        if ( compressed ) 
                return ImageLoaderMachOCompressed::instantiateFromFile(path, fd, fileData, offsetInFat, lenInFat, info, segCount, libCount, context);
        else
                return ImageLoaderMachOClassic::instantiateFromFile(path, fd, fileData, offsetInFat, lenInFat, info, segCount, libCount, context);
}

// create image by using cached mach-o file
ImageLoader* ImageLoaderMachO::instantiateFromCache(const macho_header* mh, const char* path, const struct stat& info, const LinkContext& context)
{
        // instantiate right concrete class
        bool compressed;
        unsigned int segCount;
        unsigned int libCount;
        sniffLoadCommands(mh, path, &compressed, &segCount, &libCount);
        // instantiate concrete class based on content of load commands
        if ( compressed ) 
                return ImageLoaderMachOCompressed::instantiateFromCache(mh, path, info, segCount, libCount, context);
        else
                return ImageLoaderMachOClassic::instantiateFromCache(mh, path, info, segCount, libCount, context);
}

// create image by copying an in-memory mach-o file
ImageLoader* ImageLoaderMachO::instantiateFromMemory(const char* moduleName, const macho_header* mh, uint64_t len, const LinkContext& context)
{
        bool compressed;
        unsigned int segCount;
        unsigned int libCount;
        sniffLoadCommands(mh, moduleName, &compressed, &segCount, &libCount);
        // instantiate concrete class based on content of load commands
        if ( compressed ) 
                return ImageLoaderMachOCompressed::instantiateFromMemory(moduleName, mh, len, segCount, libCount, context);
        else
                return ImageLoaderMachOClassic::instantiateFromMemory(moduleName, mh, len, segCount, libCount, context);
}



void ImageLoaderMachO::parseLoadCmds()
{
        // now that segments are mapped in, get real fMachOData, fLinkEditBase, and fSlide
        for(unsigned int i=0; i < fSegmentsCount; ++i) {
                // set up pointer to __LINKEDIT segment
                if ( strcmp(segName(i),"__LINKEDIT") == 0 ) 
                        fLinkEditBase = (uint8_t*)(segActualLoadAddress(i) - segFileOffset(i));
#if TEXT_RELOC_SUPPORT
                // __TEXT segment always starts at beginning of file and contains mach_header and load commands
                if ( strcmp(segName(i),"__TEXT") == 0 ) {
                        if ( segHasRebaseFixUps(i) )
                                fTextSegmentRebases = true;
                        if ( segHasBindFixUps(i) )
                                fTextSegmentBinds = true;
                }
#endif
#if __i386__
                if ( segIsReadOnlyImport(i) )
                        fReadOnlyImportSegment = true;
#endif
                // some segment always starts at beginning of file and contains mach_header and load commands
                if ( (segFileOffset(i) == 0) && (segFileSize(i) != 0) ) {
                        fMachOData = (uint8_t*)(segActualLoadAddress(i));
                }
        }
        
        // keep count of prebound images with weak exports
        if ( this->participatesInCoalescing() ) {
                ++fgImagesRequiringCoalescing;
                if ( this->hasCoalescedExports() ) 
                        ++fgImagesHasWeakDefinitions;
        }

        // keep count of images used in shared cache
        if ( fInSharedCache )
                ++fgImagesUsedFromSharedCache;

        // walk load commands (mapped in at start of __TEXT segment)
        const dyld_info_command* dyldInfo = NULL;
        const macho_nlist* symbolTable = NULL;
        const char* symbolTableStrings = NULL;
        const dysymtab_command* dynSymbolTable = 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_SYMTAB:
                                {
                                        const struct symtab_command* symtab = (struct symtab_command*)cmd;
                                        symbolTableStrings = (const char*)&fLinkEditBase[symtab->stroff];
                                        symbolTable = (macho_nlist*)(&fLinkEditBase[symtab->symoff]);
                                }
                                break;
                        case LC_DYSYMTAB:
                                dynSymbolTable = (struct dysymtab_command*)cmd;
                                break;
                        case LC_SUB_UMBRELLA:
                                fHasSubUmbrella = true;
                                break;
                        case LC_SUB_FRAMEWORK:
                                fInUmbrella = true;
                                break;
                        case LC_SUB_LIBRARY:
                                fHasSubLibraries = true;
                                break;
                        case LC_ROUTINES_COMMAND:
                                fHasDashInit = true;
                                break;
                        case LC_DYLD_INFO:
                        case LC_DYLD_INFO_ONLY:
                                dyldInfo = (struct dyld_info_command*)cmd;
                                break;
                        case LC_SEGMENT_COMMAND:
                                {
                                        const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                                        const bool isTextSeg = (strcmp(seg->segname, "__TEXT") == 0);
                                        const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                                        const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
                                        for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                                                const uint8_t type = sect->flags & SECTION_TYPE;
                                                if ( type == S_MOD_INIT_FUNC_POINTERS )
                                                        fHasInitializers = true;
                                                else if ( type == S_MOD_TERM_FUNC_POINTERS )
                                                        fHasTerminators = true;
                                                else if ( type == S_DTRACE_DOF )
                                                        fHasDOFSections = true;
                                                else if ( isTextSeg && (strcmp(sect->sectname, "__eh_frame") == 0) )
                                                        fEHFrameSectionOffset = (uint8_t*)sect - fMachOData;
                                                else if ( isTextSeg && (strcmp(sect->sectname, "__unwind_info") == 0) )
                                                        fUnwindInfoSectionOffset = (uint8_t*)sect - fMachOData;;
                                        }
                                }
                                break;
                        case LC_TWOLEVEL_HINTS:
                                // no longer supported
                                break;
                        case LC_ID_DYLIB:
                                {
                                        fDylibIDOffset = (uint8_t*)cmd - fMachOData;
                                }
                                break;
                        case LC_RPATH:
                        case LC_LOAD_WEAK_DYLIB:
                    case LC_REEXPORT_DYLIB:
                                // do nothing, just prevent LC_REQ_DYLD exception from occuring
                                break;
                        default:
                                if ( (cmd->cmd & LC_REQ_DYLD) != 0 )
                                        dyld::throwf("unknown required load command 0x%08X", cmd->cmd);
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        
        if ( dyldInfo != NULL )
                this->setDyldInfo(dyldInfo);
        if ( symbolTable != NULL)
                this->setSymbolTableInfo(symbolTable, symbolTableStrings, dynSymbolTable);
        
}

// don't do this work in destructor because we need object to be full subclass
// for UnmapSegments() to work
void ImageLoaderMachO::destroy()
{
        // keep count of images with weak exports
        if ( this->participatesInCoalescing() ) {
                --fgImagesRequiringCoalescing;
                if ( this->hasCoalescedExports() ) 
                        --fgImagesHasWeakDefinitions;
        }

        // keep count of images used in shared cache
        if ( fInSharedCache )
                --fgImagesUsedFromSharedCache;
                
        // unmap image when done
        UnmapSegments();
}


unsigned int ImageLoaderMachO::segmentCount() const
{
        return fSegmentsCount;
}


const macho_segment_command* ImageLoaderMachO::segLoadCommand(unsigned int segIndex) const
{
        uint32_t* lcOffsets = this->segmentCommandOffsets();
        uint32_t lcOffset =     lcOffsets[segIndex];
        return (macho_segment_command*)(&fMachOData[lcOffset]);
}

const char*     ImageLoaderMachO::segName(unsigned int segIndex) const
{
        return segLoadCommand(segIndex)->segname;
}


uintptr_t ImageLoaderMachO::segSize(unsigned int segIndex) const
{
        return segLoadCommand(segIndex)->vmsize;
}


uintptr_t ImageLoaderMachO::segFileSize(unsigned int segIndex) const
{
        return segLoadCommand(segIndex)->filesize;
}


bool ImageLoaderMachO::segHasTrailingZeroFill(unsigned int segIndex)
{
        return ( segWriteable(segIndex) && (segSize(segIndex) > segFileSize(segIndex)) );
}


uintptr_t ImageLoaderMachO::segFileOffset(unsigned int segIndex) const
{
        return segLoadCommand(segIndex)->fileoff;
}


bool ImageLoaderMachO::segReadable(unsigned int segIndex) const
{
        return ( (segLoadCommand(segIndex)->initprot & VM_PROT_READ) != 0);
}


bool ImageLoaderMachO::segWriteable(unsigned int segIndex) const
{
        return ( (segLoadCommand(segIndex)->initprot & VM_PROT_WRITE) != 0);
}


bool ImageLoaderMachO::segExecutable(unsigned int segIndex) const
{
        return ( (segLoadCommand(segIndex)->initprot & VM_PROT_EXECUTE) != 0);
}


bool ImageLoaderMachO::segUnaccessible(unsigned int segIndex) const
{
        return (segLoadCommand(segIndex)->initprot == 0);
}

bool ImageLoaderMachO::segHasPreferredLoadAddress(unsigned int segIndex) const
{
        return (segLoadCommand(segIndex)->vmaddr != 0);
}

uintptr_t ImageLoaderMachO::segPreferredLoadAddress(unsigned int segIndex) const
{
        return segLoadCommand(segIndex)->vmaddr;
}

uintptr_t ImageLoaderMachO::segActualLoadAddress(unsigned int segIndex) const
{
        return segLoadCommand(segIndex)->vmaddr + fSlide;
}


uintptr_t ImageLoaderMachO::segActualEndAddress(unsigned int segIndex) const
{
        return segActualLoadAddress(segIndex) + segSize(segIndex);
}

bool ImageLoaderMachO::segHasRebaseFixUps(unsigned int segIndex) const
{
        // scan sections for fix-up bit
        const macho_segment_command* segCmd = segLoadCommand(segIndex);
        const struct macho_section* const sectionsStart = (struct macho_section*)((char*)segCmd + sizeof(struct macho_segment_command));
        const struct macho_section* const sectionsEnd = &sectionsStart[segCmd->nsects];
        for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                if ( (sect->flags & S_ATTR_LOC_RELOC) != 0 )
                        return true;
        }
        return false;
}

bool ImageLoaderMachO::segHasBindFixUps(unsigned int segIndex) const
{
        // scan sections for fix-up bit
        const macho_segment_command* segCmd = segLoadCommand(segIndex);
        const struct macho_section* const sectionsStart = (struct macho_section*)((char*)segCmd + sizeof(struct macho_segment_command));
        const struct macho_section* const sectionsEnd = &sectionsStart[segCmd->nsects];
        for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                if ( (sect->flags & S_ATTR_EXT_RELOC) != 0 )
                        return true;
        }
        return false;
}

#if __i386__
bool ImageLoaderMachO::segIsReadOnlyImport(unsigned int segIndex) const
{
        const macho_segment_command* segCmd = segLoadCommand(segIndex);
        return (    (segCmd->initprot & VM_PROT_EXECUTE) 
                        && ((segCmd->initprot & VM_PROT_WRITE) == 0) 
                        && (strcmp(segCmd->segname, "__IMPORT") == 0) );
}
#endif


void ImageLoaderMachO::UnmapSegments()
{
        // usually unmap image when done
        if ( ! this->leaveMapped() && (this->getState() >= dyld_image_state_mapped) ) {
                // unmap TEXT segment last because it contains load command being inspected
                unsigned int textSegmentIndex = 0;
                for(unsigned int i=0; i < fSegmentsCount; ++i) {
                        //dyld::log("unmap %s at 0x%08lX\n", seg->getName(), seg->getActualLoadAddress(this));
                        if ( strcmp(segName(i), "__TEXT") == 0 ) {
                                textSegmentIndex = i;
                        }
                        else {
                                // update stats
                                --ImageLoader::fgTotalSegmentsMapped;
                                ImageLoader::fgTotalBytesMapped -= segSize(i);
                                munmap((void*)segActualLoadAddress(i), segSize(i));
                        }
                }
                // now unmap TEXT
                --ImageLoader::fgTotalSegmentsMapped;
                ImageLoader::fgTotalBytesMapped -= segSize(textSegmentIndex);
                munmap((void*)segActualLoadAddress(textSegmentIndex), segSize(textSegmentIndex));
        }
}


// prefetch __DATA/__OBJC pages during launch, but not for dynamically loaded code
void ImageLoaderMachO::preFetchDATA(int fd, uint64_t offsetInFat, const LinkContext& context)
{
        if ( context.linkingMainExecutable ) {
                for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                        if ( segWriteable(i) && (segFileSize(i) > 0) ) {
                                // prefetch writable segment that have mmap'ed regions
                                radvisory advice;
                                advice.ra_offset = offsetInFat + segFileOffset(i);
                                advice.ra_count = segFileSize(i);
                                // limit prefetch to 1MB (256 pages)
                                if ( advice.ra_count > 1024*1024 )
                                        advice.ra_count = 1024*1024;
                                // don't prefetch single pages, let them fault in
                                fgTotalBytesPreFetched += advice.ra_count;
                                fcntl(fd, F_RDADVISE, &advice);
                                if ( context.verboseMapping ) {
                                        dyld::log("%18s prefetching 0x%0lX -> 0x%0lX\n", 
                                                segName(i), segActualLoadAddress(i), segActualLoadAddress(i)+advice.ra_count-1);
                                }
                        }
                }
        }
}


bool ImageLoaderMachO::segmentsMustSlideTogether() const 
{
        return true;
}

bool ImageLoaderMachO::segmentsCanSlide() const 
{
        return (this->isDylib() || this->isBundle() || this->isPositionIndependentExecutable());
}

bool ImageLoaderMachO::isBundle() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( mh->filetype == MH_BUNDLE );
}

bool ImageLoaderMachO::isDylib() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( mh->filetype == MH_DYLIB );
}

bool ImageLoaderMachO::isExecutable() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( mh->filetype == MH_EXECUTE );
}

bool ImageLoaderMachO::isPositionIndependentExecutable() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( (mh->filetype == MH_EXECUTE) && ((mh->flags & MH_PIE) != 0) );
}


bool ImageLoaderMachO::forceFlat() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( (mh->flags & MH_FORCE_FLAT) != 0 );
}

bool ImageLoaderMachO::usesTwoLevelNameSpace() const
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( (mh->flags & MH_TWOLEVEL) != 0 );
}

bool ImageLoaderMachO::isPrebindable() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( (mh->flags & MH_PREBOUND) != 0 );
}

bool ImageLoaderMachO::hasCoalescedExports() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( (mh->flags & MH_WEAK_DEFINES) != 0 );
}

bool ImageLoaderMachO::hasReferencesToWeakSymbols() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        return ( (mh->flags & MH_BINDS_TO_WEAK) != 0 );
}

bool ImageLoaderMachO::participatesInCoalescing() const 
{
        const macho_header* mh = (macho_header*)fMachOData;
        // if image is loaded with RTLD_LOCAL, then its symbols' visibility
        // is reduced and it can't coalesce with other images
        if ( this->hasHiddenExports() )
                return false;
        return ( (mh->flags & (MH_WEAK_DEFINES|MH_BINDS_TO_WEAK)) != 0 );
}



void ImageLoaderMachO::setSlide(intptr_t slide)
{
        fSlide = slide;
}

#if CODESIGNING_SUPPORT
void ImageLoaderMachO::loadCodeSignature(const uint8_t* fileData, int fd,  uint64_t offsetInFatFile)
{
        // look for code signature load command
        // do this in the read() memory buffer - not in the mapped __TEXT segment
        const uint32_t cmd_count = ((macho_header*)fileData)->ncmds;
        const struct load_command* const cmds = (struct load_command*)&fileData[sizeof(macho_header)];
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                if ( cmd->cmd == LC_CODE_SIGNATURE ) {
                        const struct linkedit_data_command *sigcmd = (struct linkedit_data_command*) cmd;
                        // fLinkEditBase is not set up yet, so compute it
                        const uint8_t* linkEditBase = NULL;
                        for(unsigned int i=0; i < fSegmentsCount; ++i) {
                                // set up pointer to __LINKEDIT segment
                                if ( strcmp(segName(i),"__LINKEDIT") == 0 ) {
                                        linkEditBase = (uint8_t*)(segActualLoadAddress(i) - segFileOffset(i));
                                        break;
                                }
                        }
                        fsignatures_t siginfo;
                        siginfo.fs_file_start=offsetInFatFile;                          // CD coverage offset 
                        siginfo.fs_blob_start=(void*)(linkEditBase+sigcmd->dataoff);    // start of CD in file
                        siginfo.fs_blob_size=sigcmd->datasize;                  // size of CD
                        int result = fcntl(fd, F_ADDSIGS, &siginfo);
                        if ( result == -1 ) 
                                dyld::log("dyld: code signature failed for %s with errno=%d\n", this->getPath(), errno);
                        break; // only support one LC_CODE_SIGNATURE
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
}
#endif


const char* ImageLoaderMachO::getInstallPath() const
{
        if ( fDylibIDOffset != 0 ) {
                const dylib_command* dylibID = (dylib_command*)(&fMachOData[fDylibIDOffset]);
                return (char*)dylibID + dylibID->dylib.name.offset;
        }
        return NULL;
}



void* ImageLoaderMachO::getMain() const
{
        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_UNIXTHREAD:
                        {
                        #if __ppc__
                                const ppc_thread_state_t* registers = (ppc_thread_state_t*)(((char*)cmd) + 16);
                                return (void*)(registers->srr0 + fSlide);
                        #elif __ppc64__
                                const ppc_thread_state64_t* registers = (ppc_thread_state64_t*)(((char*)cmd) + 16);
                                return (void*)(registers->srr0 + fSlide);
                        #elif __i386__
                                const i386_thread_state_t* registers = (i386_thread_state_t*)(((char*)cmd) + 16);
                                return (void*)(registers->eip + fSlide);
                        #elif __x86_64__
                                const x86_thread_state64_t* registers = (x86_thread_state64_t*)(((char*)cmd) + 16);
                                return (void*)(registers->rip + fSlide);
                        #elif __arm__
                                const arm_thread_state_t* registers = (arm_thread_state_t*)(((char*)cmd) + 16);
                                return (void*)(registers->__pc + fSlide);
                        #else
                                #warning need processor specific code
                        #endif
                        }
                        break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        return NULL;
}

bool ImageLoaderMachO::needsAddedLibSystemDepency(unsigned int libCount, const macho_header* mh)
{
        // <rdar://problem/6357561> ensure that every image depends on something which depends on libSystem
        if ( libCount > 1 )
                return false;
                
        // <rdar://problem/6409800> dyld implicit-libSystem breaks valgrind
        if ( mh->filetype == MH_EXECUTE ) 
                return false;
        
        bool isNonOSdylib = false;
        const uint32_t cmd_count = mh->ncmds;
        const struct load_command* const cmds = (struct load_command*)((uint8_t*)mh+sizeof(macho_header));
        const struct load_command* cmd = cmds;
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_LOAD_DYLIB:
                        case LC_LOAD_WEAK_DYLIB:
                        case LC_REEXPORT_DYLIB:
                                return false;
                        case LC_ID_DYLIB:
                                {
                                const dylib_command* dylibID = (dylib_command*)cmd;
                                const char* installPath = (char*)cmd + dylibID->dylib.name.offset;
                                // It is OK for OS dylibs (libSystem or libmath or Rosetta shims) to have no dependents
                                // but all other dylibs must depend on libSystem for initialization to initialize libSystem first
                                // <rdar://problem/6497528> rosetta circular dependency spew
                                isNonOSdylib = ( (strncmp(installPath, "/usr/lib/", 9) != 0) && (strncmp(installPath, "/usr/libexec/oah/Shims", 9) != 0) );
                                }
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        return isNonOSdylib;
}


void ImageLoaderMachO::doGetDependentLibraries(DependentLibraryInfo libs[])
{
        if ( needsAddedLibSystemDepency(libraryCount(), (macho_header*)fMachOData) ) {
                DependentLibraryInfo* lib = &libs[0];
                lib->name = "/usr/lib/libSystem.B.dylib";
                lib->info.checksum = 0;
                lib->info.minVersion = 0;
                lib->info.maxVersion = 0;
                lib->required = false;
                lib->reExported = false;
        }
        else {
                uint32_t index = 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_LOAD_DYLIB:
                                case LC_LOAD_WEAK_DYLIB:
                                case LC_REEXPORT_DYLIB:
                                {
                                        const struct dylib_command* dylib = (struct dylib_command*)cmd;
                                        DependentLibraryInfo* lib = &libs[index++];
                                        lib->name = (char*)cmd + dylib->dylib.name.offset;
                                        //lib->name = strdup((char*)cmd + dylib->dylib.name.offset);
                                        lib->info.checksum = dylib->dylib.timestamp;
                                        lib->info.minVersion = dylib->dylib.compatibility_version;
                                        lib->info.maxVersion = dylib->dylib.current_version;
                                        lib->required = (cmd->cmd != LC_LOAD_WEAK_DYLIB);
                                        lib->reExported = (cmd->cmd == LC_REEXPORT_DYLIB);
                                }
                                break;
                        }
                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                }
        }
}

ImageLoader::LibraryInfo ImageLoaderMachO::doGetLibraryInfo()
{
        LibraryInfo info;
        if ( fDylibIDOffset != 0 ) {
                const dylib_command* dylibID = (dylib_command*)(&fMachOData[fDylibIDOffset]);
                info.minVersion = dylibID->dylib.compatibility_version;
                info.maxVersion = dylibID->dylib.current_version;
                info.checksum = dylibID->dylib.timestamp;
        }
        else {
                info.minVersion = 0;
                info.maxVersion = 0;            
                info.checksum = 0;
        }
        return info;
}

void ImageLoaderMachO::getRPaths(const LinkContext& context, std::vector<const char*>& paths) const
{
        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_RPATH:
                                const char* path = (char*)cmd + ((struct rpath_command*)cmd)->path.offset;
                                if ( strncmp(path, "@loader_path/", 13) == 0 ) {
                                        if ( context.processIsRestricted  && (context.mainExecutable == this) ) {
                                                dyld::warn("LC_RPATH %s in %s being ignored in restricted program because of @loader_path\n", path, this->getPath());
                                                break;
                                        }
                                        char resolvedPath[PATH_MAX];
                                        if ( realpath(this->getPath(), resolvedPath) != NULL ) {
                                                char newRealPath[strlen(resolvedPath) + strlen(path)];
                                                strcpy(newRealPath, resolvedPath);
                                                char* addPoint = strrchr(newRealPath,'/');
                                                if ( addPoint != NULL )
                                                        strcpy(&addPoint[1], &path[13]);
                                                else
                                                        strcpy(newRealPath, &path[13]);
                                                path = strdup(newRealPath);
                                        }
                                }
                                else if ( strncmp(path, "@executable_path/", 17) == 0 ) {
                                        if ( context.processIsRestricted ) {
                                                dyld::warn("LC_RPATH %s in %s being ignored in restricted program because of @executable_path\n", path, this->getPath());
                                                break;
                                        }
                                        char resolvedPath[PATH_MAX];
                                        if ( realpath(context.mainExecutable->getPath(), resolvedPath) != NULL ) {
                                                char newRealPath[strlen(resolvedPath) + strlen(path)];
                                                strcpy(newRealPath, resolvedPath);
                                                char* addPoint = strrchr(newRealPath,'/');
                                                if ( addPoint != NULL )
                                                        strcpy(&addPoint[1], &path[17]);
                                                else
                                                        strcpy(newRealPath, &path[17]);
                                                path = strdup(newRealPath);
                                        }
                                }
                                else if ( (path[0] != '/') && context.processIsRestricted ) {
                                        dyld::warn("LC_RPATH %s in %s being ignored in restricted program because it is a relative path\n", path, this->getPath());
                                        break;
                                }
                                else if ( (path[0] == '/') && (context.rootPaths != NULL) ) {
                                        // <rdar://problem/5869973> DYLD_ROOT_PATH should apply to LC_RPATH rpaths
                                        // DYLD_ROOT_PATH can be a list of paths, but at this point we can only support one, so use first combination that exists
                                        bool found = false;
                                        for(const char** rp = context.rootPaths; *rp != NULL; ++rp) {
                                                char newPath[PATH_MAX];
                                                strcpy(newPath, *rp);
                                                strcat(newPath, path);
                                                struct stat stat_buf;
                                                if ( stat(newPath, &stat_buf) != -1 ) {
                                                        //dyld::log("combined DYLD_ROOT_PATH and LC_RPATH: %s\n", newPath);
                                                        path = strdup(newPath);
                                                        found = true;
                                                        break;
                                                }
                                        }
                                        if ( ! found ) {
                                                // make copy so that all elements of 'paths' can be freed
                                                path = strdup(path);
                                        }
                                }
                                else {
                                        // make copy so that all elements of 'paths' can be freed
                                        path = strdup(path);
                                }
                                paths.push_back(path);
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
}

bool ImageLoaderMachO::getUUID(uuid_t uuid) const
{
        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_UUID:
                                uuid_command* uc = (uuid_command*)cmd;
                                memcpy(uuid, uc->uuid, 16);
                                return true;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        bzero(uuid, 16);
        return false;
}

void ImageLoaderMachO::doRebase(const LinkContext& context)
{
        // if prebound and loaded at prebound address, then no need to rebase
        if ( this->usablePrebinding(context) ) {
                // skip rebasing because prebinding is valid
                ++fgImagesWithUsedPrebinding; // bump totals for statistics
                return;
        }

        // print why prebinding was not used
        if ( context.verbosePrebinding ) {
                if ( !this->isPrebindable() ) {
                        dyld::log("dyld: image not prebound, so could not use prebinding in %s\n", this->getPath());
                }
                else if ( fSlide != 0 ) {
                        dyld::log("dyld: image slid, so could not use prebinding in %s\n", this->getPath());
                }
                else if ( !this->allDependentLibrariesAsWhenPreBound() ) {
                        dyld::log("dyld: dependent libraries changed, so could not use prebinding in %s\n", this->getPath());
                }
                else if ( !this->usesTwoLevelNameSpace() ){
                        dyld::log("dyld: image uses flat-namespace so, parts of prebinding ignored %s\n", this->getPath());
                }
                else {
                        dyld::log("dyld: environment variable disabled use of prebinding in %s\n", this->getPath());
                }
        }

        //dyld::log("slide=0x%08lX for %s\n", slide, this->getPath());

#if PREBOUND_IMAGE_SUPPORT
        // if prebound and we got here, then prebinding is not valid, so reset all lazy pointers
        // if this image is in the shared cache, do not reset, they will be bound in doBind()
        if ( this->isPrebindable() && !fInSharedCache )
                this->resetPreboundLazyPointers(context);
#endif

        // if loaded at preferred address, no rebasing necessary
        if ( this->fSlide == 0 ) 
                return;

#if TEXT_RELOC_SUPPORT
        // if there are __TEXT fixups, temporarily make __TEXT writable
        if ( fTextSegmentRebases ) 
                this->makeTextSegmentWritable(context, true);
#endif

        // do actual rebasing
        this->rebase(context);
                        
#if TEXT_RELOC_SUPPORT
        // if there were __TEXT fixups, restore write protection
        if ( fTextSegmentRebases ) 
                this->makeTextSegmentWritable(context, false);
        
#endif  
}

#if TEXT_RELOC_SUPPORT
void ImageLoaderMachO::makeTextSegmentWritable(const LinkContext& context, bool writeable)
{
        int textSegmentIndex = 0;
        for(unsigned int i=0; i < fSegmentsCount; ++i) {
                if ( strcmp(segName(i), "__TEXT") == 0 ) {
                        textSegmentIndex = i;
                        break;
                }
        }

        if ( writeable ) {
                segMakeWritable(textSegmentIndex, context);
        }
        else {
                segProtect(textSegmentIndex, context);
                sys_icache_invalidate((void*)segActualLoadAddress(textSegmentIndex), segSize(textSegmentIndex));
        }
}
#endif

const ImageLoader::Symbol* ImageLoaderMachO::findExportedSymbol(const char* name, bool searchReExports, const ImageLoader** foundIn) const
{
        // look in this image first
        const ImageLoader::Symbol* result = this->findExportedSymbol(name, foundIn);
        if ( result != NULL )
                return result;
        
        if ( searchReExports ) {
                for(unsigned int i=0; i < libraryCount(); ++i){
                        if ( libReExported(i) ) {
                                ImageLoader* image = libImage(i);
                                if ( image != NULL ) {
                                        const Symbol* result = image->findExportedSymbol(name, searchReExports, foundIn);
                                        if ( result != NULL )
                                                return result;
                                }
                        }
                }
        }
        

        return NULL;
}



uintptr_t ImageLoaderMachO::getExportedSymbolAddress(const Symbol* sym, const LinkContext& context, const ImageLoader* requestor) const
{
        return this->getSymbolAddress(sym, requestor, context);
}

uintptr_t ImageLoaderMachO::getSymbolAddress(const Symbol* sym, const ImageLoader* requestor, const LinkContext& context) const
{
        uintptr_t result = exportedSymbolAddress(sym);
        return result;
}

ImageLoader::DefinitionFlags ImageLoaderMachO::getExportedSymbolInfo(const Symbol* sym) const
{
        if ( exportedSymbolIsWeakDefintion(sym) )
                return kWeakDefinition;
        else
                return kNoDefinitionOptions;
}

const char* ImageLoaderMachO::getExportedSymbolName(const Symbol* sym) const
{
        return exportedSymbolName(sym);
}

uint32_t ImageLoaderMachO::getExportedSymbolCount() const
{
        return exportedSymbolCount();
}


const ImageLoader::Symbol* ImageLoaderMachO::getIndexedExportedSymbol(uint32_t index) const
{
        return exportedSymbolIndexed(index);
}


uint32_t ImageLoaderMachO::getImportedSymbolCount() const
{
        return importedSymbolCount();
}


const ImageLoader::Symbol* ImageLoaderMachO::getIndexedImportedSymbol(uint32_t index) const
{
        return importedSymbolIndexed(index);
}


ImageLoader::ReferenceFlags ImageLoaderMachO::getImportedSymbolInfo(const ImageLoader::Symbol* sym) const
{
        ImageLoader::ReferenceFlags flags = kNoReferenceOptions;
        return flags;
}


const char* ImageLoaderMachO::getImportedSymbolName(const ImageLoader::Symbol* sym) const
{
        return importedSymbolName(sym);
}


bool ImageLoaderMachO::getSectionContent(const char* segmentName, const char* sectionName, void** start, size_t* length)
{
        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) {
                                                if ( (strcmp(sect->segname, segmentName) == 0) && (strcmp(sect->sectname, sectionName) == 0) ) {
                                                        *start = (uintptr_t*)(sect->addr + fSlide);
                                                        *length = sect->size;
                                                        return true;
                                                }
                                        }
                                }
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        *start = NULL;
        *length = 0;
        return false;
}

void ImageLoaderMachO::getUnwindInfo(dyld_unwind_sections* info)
{
        info->mh = this->machHeader();
        info->dwarf_section = 0;
        info->dwarf_section_length = 0;
        info->compact_unwind_section = 0;
        info->compact_unwind_section_length = 0;
        if ( fEHFrameSectionOffset != 0 ) {
                const macho_section* sect = (macho_section*)&fMachOData[fEHFrameSectionOffset];
                info->dwarf_section = (void*)(sect->addr + fSlide);
                info->dwarf_section_length = sect->size;
        }
        if ( fUnwindInfoSectionOffset != 0 ) {
                const macho_section* sect = (macho_section*)&fMachOData[fUnwindInfoSectionOffset];
                info->compact_unwind_section = (void*)(sect->addr + fSlide);
                info->compact_unwind_section_length = sect->size;
        }
}


bool ImageLoaderMachO::findSection(const void* imageInterior, const char** segmentName, const char** sectionName, size_t* sectionOffset)
{
        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 uintptr_t unslidInteriorAddress = (uintptr_t)imageInterior - this->getSlide();
        for (uint32_t i = 0; i < cmd_count; ++i) {
                switch (cmd->cmd) {
                        case LC_SEGMENT_COMMAND:
                                {
                                        const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
                                        if ( (unslidInteriorAddress >= seg->vmaddr) && (unslidInteriorAddress < (seg->vmaddr+seg->vmsize)) ) {
                                                const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                                                const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
                                                for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                                                        if ((sect->addr <= unslidInteriorAddress) && (unslidInteriorAddress < (sect->addr+sect->size))) {
                                                                if ( segmentName != NULL )
                                                                        *segmentName = sect->segname;
                                                                if ( sectionName != NULL )
                                                                        *sectionName = sect->sectname;
                                                                if ( sectionOffset != NULL )
                                                                        *sectionOffset = unslidInteriorAddress - sect->addr;
                                                                return true;
                                                        }
                                                }
                                        }
                                }
                                break;
                }
                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
        }
        return false;
}


void __attribute__((noreturn)) ImageLoaderMachO::throwSymbolNotFound(const char* symbol, const char* referencedFrom, const char* expectedIn)
{
        dyld::throwf("Symbol not found: %s\n  Referenced from: %s\n  Expected in: %s\n", symbol, referencedFrom, expectedIn); 
}

const mach_header* ImageLoaderMachO::machHeader() const
{
        return (mach_header*)fMachOData;
}

uintptr_t ImageLoaderMachO::getSlide() const
{
        return fSlide;
}

// hmm. maybe this should be up in ImageLoader??
const void* ImageLoaderMachO::getEnd() const
{
        uintptr_t lastAddress = 0;
        for(unsigned int i=0; i < fSegmentsCount; ++i) {
                uintptr_t segEnd = segActualEndAddress(i);
                if ( strcmp(segName(i), "__UNIXSTACK") != 0 ) {
                        if ( segEnd > lastAddress )
                                lastAddress = segEnd;
                }
        }
        return (const void*)lastAddress;
}


uintptr_t ImageLoaderMachO::bindLocation(const LinkContext& context, uintptr_t location, uintptr_t value, 
                                                                                const ImageLoader* targetImage, uint8_t type, const char* symbolName, 
                                                                                intptr_t addend, const char* msg)
{
        // log
        if ( context.verboseBind ) {
                if ( addend != 0 )
                        dyld::log("dyld: %sbind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX + %ld\n",
                                                msg, this->getShortName(), (uintptr_t)location,
                                                ((targetImage != NULL) ? targetImage->getShortName() : "<weak_import-missing>"),
                                                symbolName, (uintptr_t)location, value, addend);
                else
                        dyld::log("dyld: %sbind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX\n",
                                                msg, this->getShortName(), (uintptr_t)location,
                                                ((targetImage != NULL) ? targetImage->getShortName() : "<weak>import-missing>"),
                                                 symbolName, (uintptr_t)location, value);
        }
        
        // do actual update
        uintptr_t* locationToFix = (uintptr_t*)location;
        uint32_t* loc32;
        uintptr_t newValue = value+addend;
        uint32_t value32;
        switch (type) {
                case BIND_TYPE_POINTER:
                        // test first so we don't needless dirty pages
                        if ( *locationToFix != newValue )
                                *locationToFix = newValue;
                        break;
                case BIND_TYPE_TEXT_ABSOLUTE32:
                        loc32 = (uint32_t*)locationToFix;
                        value32 = (uint32_t)newValue;
                        if ( *loc32 != value32 )
                                *loc32 = value32;
                        break;
                case BIND_TYPE_TEXT_PCREL32:
                        loc32 = (uint32_t*)locationToFix;
                        value32 = (uint32_t)newValue - (((uintptr_t)locationToFix) + 4);
                        if ( *loc32 != value32 )
                                *loc32 = value32;
                        break;
                default:
                        dyld::throwf("bad bind type %d", type);
        }
        
        // update statistics
        ++fgTotalBindFixups;
        
        return newValue;
}





#if SUPPORT_OLD_CRT_INITIALIZATION
// first 16 bytes of "start" in crt1.o
#if __ppc__
        static uint32_t sStandardEntryPointInstructions[4] = { 0x7c3a0b78, 0x3821fffc, 0x54210034, 0x38000000 };
#elif __i386__
        static uint8_t sStandardEntryPointInstructions[16] = { 0x6a, 0x00, 0x89, 0xe5, 0x83, 0xe4, 0xf0, 0x83, 0xec, 0x10, 0x8b, 0x5d, 0x04, 0x89, 0x5c, 0x24 };
#endif
#endif

struct DATAdyld {
        void*                   dyldLazyBinder;         // filled in at launch by dyld to point into dyld to &stub_binding_helper_interface
        void*                   dyldFuncLookup;         // filled in at launch by dyld to point into dyld to &_dyld_func_lookup
        // the following only exist in main executables built for 10.5 or later
        ProgramVars             vars;
};

// These are defined in dyldStartup.s
extern "C" void stub_binding_helper();
extern "C" bool dyld_func_lookup(const char* name, uintptr_t* address);


void ImageLoaderMachO::setupLazyPointerHandler(const LinkContext& context)
{
        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;
        // set up __dyld section
        // optimizations:
        //   1) do nothing if image is in dyld shared cache and dyld loaded at same address as when cache built
        //       2) first read __dyld value, if already correct don't write, this prevents dirtying a page
        if ( !fInSharedCache || !context.dyldLoadedAtSameAddressNeededBySharedCache ) {
                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 ( strcmp(seg->segname, "__DATA") == 0 ) {
                                        const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
                                        const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
                                        for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
                                                if ( strcmp(sect->sectname, "__dyld" ) == 0 ) {
                                                        struct DATAdyld* dd = (struct DATAdyld*)(sect->addr + fSlide);
                                                        if ( sect->size > offsetof(DATAdyld, dyldLazyBinder) ) {
                                                                if ( dd->dyldLazyBinder != (void*)&stub_binding_helper )
                                                                        dd->dyldLazyBinder = (void*)&stub_binding_helper;
                                                        }
                                                        if ( sect->size > offsetof(DATAdyld, dyldFuncLookup) ) {
                                                                if ( dd->dyldFuncLookup != (void*)&dyld_func_lookup )
                                                                        dd->dyldFuncLookup = (void*)&dyld_func_lookup;
                                                        }
                                                        if ( mh->filetype == MH_EXECUTE ) {
                                                                // there are two ways to get the program variables
                                                                if ( (sect->size > offsetof(DATAdyld, vars)) && (dd->vars.mh == mh) ) {
                                                                        // some really old binaries have space for vars, but it is zero filled
                                                                        // main executable has 10.5 style __dyld section that has program variable pointers
                                                                        context.setNewProgramVars(dd->vars);
                                                                }
                                                                else {
                                                                        // main executable is pre-10.5 and requires the symbols names to be looked up
                                                                        this->lookupProgramVars(context);
                                #if SUPPORT_OLD_CRT_INITIALIZATION
                                                                        // If the first 16 bytes of the entry point's instructions do not 
                                                                        // match what crt1.o supplies, then the program has a custom entry point.
                                                                        // This means it might be doing something that needs to be executed before 
                                                                        // initializers are run. 
                                                                        if ( memcmp(this->getMain(), sStandardEntryPointInstructions, 16) != 0 ) {
                                                                                if ( context.verboseInit )
                                                                                        dyld::log("dyld: program uses non-standard entry point so delaying running of initializers\n");
                                                                                context.setRunInitialzersOldWay();
                                                                        }
                                #endif
                                                                }
                                                        }
                                                }
                                                else if ( (strcmp(sect->sectname, "__program_vars" ) == 0) && (mh->filetype == MH_EXECUTE) ) {
                                                        // this is a Mac OS X 10.6 or later main executable 
                                                        struct ProgramVars* pv = (struct ProgramVars*)(sect->addr + fSlide);
                                                        context.setNewProgramVars(*pv);
                                                }
                                        }
                                }
                        }
                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                }
        }
}

                                                                        
void ImageLoaderMachO::lookupProgramVars(const LinkContext& context) const
{
        ProgramVars vars = context.programVars;
        const ImageLoader::Symbol* sym;
        
        // get mach header directly
        vars.mh = (macho_header*)fMachOData;
        
        // lookup _NXArgc
        sym = this->findExportedSymbol("_NXArgc", false, NULL);
        if ( sym != NULL )
                vars.NXArgcPtr = (int*)this->getExportedSymbolAddress(sym, context, this);
                
        // lookup _NXArgv
        sym = this->findExportedSymbol("_NXArgv", false, NULL);
        if ( sym != NULL )
                vars.NXArgvPtr = (const char***)this->getExportedSymbolAddress(sym, context, this);
                
        // lookup _environ
        sym = this->findExportedSymbol("_environ", false, NULL);
        if ( sym != NULL )
                vars.environPtr = (const char***)this->getExportedSymbolAddress(sym, context, this);
                
        // lookup __progname
        sym = this->findExportedSymbol("___progname", false, NULL);
        if ( sym != NULL )
                vars.__prognamePtr = (const char**)this->getExportedSymbolAddress(sym, context, this);
                
        context.setNewProgramVars(vars);
}


bool ImageLoaderMachO::usablePrebinding(const LinkContext& context) const
{
        // if prebound and loaded at prebound address, and all libraries are same as when this was prebound, then no need to bind
        if ( (this->isPrebindable() || fInSharedCache)
                && (this->getSlide() == 0) 
                && this->usesTwoLevelNameSpace()
                && this->allDependentLibrariesAsWhenPreBound() ) {
                // allow environment variables to disable prebinding
                if ( context.bindFlat )
                        return false;
                switch ( context.prebindUsage ) {
                        case kUseAllPrebinding:
                                return true;
                        case kUseSplitSegPrebinding:
                                return this->fIsSplitSeg;
                        case kUseAllButAppPredbinding:
                                return (this != context.mainExecutable);
                        case kUseNoPrebinding:
                                return false;
                }
        }
        return false;
}


void ImageLoaderMachO::doImageInit(const LinkContext& context)
{
        if ( fHasDashInit ) {
                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_ROUTINES_COMMAND:
                                        Initializer func = (Initializer)(((struct macho_routines_command*)cmd)->init_address + fSlide);
                                        if ( context.verboseInit )
                                                dyld::log("dyld: calling -init function 0x%p in %s\n", func, this->getPath());
                                        func(context.argc, context.argv, context.envp, context.apple, &context.programVars);
                                        break;
                        }
                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                }
        }
}

void ImageLoaderMachO::doModInitFunctions(const LinkContext& context)
{
        if ( fHasInitializers ) {
                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;
                                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_MOD_INIT_FUNC_POINTERS ) {
                                                Initializer* inits = (Initializer*)(sect->addr + fSlide);
                                                const uint32_t count = sect->size / sizeof(uintptr_t);
                                                for (uint32_t i=0; i < count; ++i) {
                                                        Initializer func = inits[i];
                                                        if ( context.verboseInit )
                                                                dyld::log("dyld: calling initializer function %p in %s\n", func, this->getPath());
                                                        func(context.argc, context.argv, context.envp, context.apple, &context.programVars);
                                                }
                                        }
                                }
                                cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                        }
                }
        }
}






void ImageLoaderMachO::doGetDOFSections(const LinkContext& context, std::vector<ImageLoader::DOFInfo>& dofs)
{
        if ( fHasDOFSections ) {
                // walk load commands (mapped in at start of __TEXT segment)
                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) {
                                                        if ( (sect->flags & SECTION_TYPE) == S_DTRACE_DOF ) {
                                                                ImageLoader::DOFInfo info;
                                                                info.dof                        = (void*)(sect->addr + fSlide);
                                                                info.imageHeader        = this->machHeader();
                                                                info.imageShortName = this->getShortName();
                                                                dofs.push_back(info);
                                                        }
                                                }
                                        }
                                        break;
                        }
                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                }
        }
}       


void ImageLoaderMachO::doInitialization(const LinkContext& context)
{
        // mach-o has -init and static initializers
        doImageInit(context);
        doModInitFunctions(context);
}

bool ImageLoaderMachO::needsInitialization()
{
        return ( fHasDashInit || fHasInitializers );
}


bool ImageLoaderMachO::needsTermination()
{
        return fHasTerminators;
}


void ImageLoaderMachO::doTermination(const LinkContext& context)
{
        if ( fHasTerminators ) {
                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;
                                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_MOD_TERM_FUNC_POINTERS ) {
                                                Terminator* terms = (Terminator*)(sect->addr + fSlide);
                                                const uint32_t count = sect->size / sizeof(uintptr_t);
                                                for (uint32_t i=count; i > 0; --i) {
                                                        Terminator func = terms[i-1];
                                                        if ( context.verboseInit )
                                                                dyld::log("dyld: calling termination function %p in %s\n", func, this->getPath());
                                                        func();
                                                }
                                        }
                                }
                        }
                        cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
                }
        }
}


void ImageLoaderMachO::printStatistics(unsigned int imageCount)
{
        ImageLoader::printStatistics(imageCount);
        dyld::log("total symbol trie searches:    %d\n", fgSymbolTrieSearchs);
        dyld::log("total symbol table binary searches:    %d\n", fgSymbolTableBinarySearchs);
        dyld::log("total images defining/using weak symbols:  %u/%u\n", fgImagesHasWeakDefinitions, fgImagesRequiringCoalescing);
}


intptr_t ImageLoaderMachO::assignSegmentAddresses(const LinkContext& context)
{
        // preflight and calculate slide if needed
        const bool inPIE = (fgNextPIEDylibAddress != 0);
        intptr_t slide = 0;
        if ( this->segmentsCanSlide() && this->segmentsMustSlideTogether() ) {
                bool needsToSlide = false;
                bool imageHasPreferredLoadAddress = segHasPreferredLoadAddress(0);
                uintptr_t lowAddr = (unsigned long)(-1);
                uintptr_t highAddr = 0;
                for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                        const uintptr_t segLow = segPreferredLoadAddress(i);
                        const uintptr_t segHigh = (segLow + segSize(i) + 4095) & -4096;
                        if ( segLow < lowAddr )
                                lowAddr = segLow;
                        if ( segHigh > highAddr )
                                highAddr = segHigh;
                                
                        if ( needsToSlide || !imageHasPreferredLoadAddress || inPIE || !reserveAddressRange(segPreferredLoadAddress(i), segSize(i)) )
                                needsToSlide = true;
                }
                if ( needsToSlide ) {
                        // find a chunk of address space to hold all segments
                        uintptr_t addr = reserveAnAddressRange(highAddr-lowAddr, context);
                        slide = addr - lowAddr;
                }
        } 
        else if ( ! this->segmentsCanSlide() ) {
                for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                        if ( strcmp(segName(i), "__PAGEZERO") == 0 )
                                continue;
                        if ( !reserveAddressRange(segPreferredLoadAddress(i), segSize(i)) )
                                throw "can't map";
                }
        }
        else {
                throw "mach-o does not support independently sliding segments";
        }
        return slide;
}


uintptr_t ImageLoaderMachO::reserveAnAddressRange(size_t length, const ImageLoader::LinkContext& context)
{
        vm_address_t addr = 0;
        vm_size_t size = length;
        // in PIE programs, load initial dylibs after main executable so they don't have fixed addresses either
        if ( fgNextPIEDylibAddress != 0 ) {
                addr = fgNextPIEDylibAddress + (arc4random() & 0x3) * 4096; // add small random padding between dylibs
                kern_return_t r = vm_allocate(mach_task_self(), &addr, size, VM_FLAGS_FIXED);
                if ( r == KERN_SUCCESS ) {
                        fgNextPIEDylibAddress = addr + size;
                        return addr;
                }
                fgNextPIEDylibAddress = 0;
        }
        kern_return_t r = vm_allocate(mach_task_self(), &addr, size, VM_FLAGS_ANYWHERE);
        if ( r != KERN_SUCCESS ) 
                throw "out of address space";
        
        return addr;
}

bool ImageLoaderMachO::reserveAddressRange(uintptr_t start, size_t length)
{
        vm_address_t addr = start;
        vm_size_t size = length;
        kern_return_t r = vm_allocate(mach_task_self(), &addr, size, false /*only this range*/);
        if ( r != KERN_SUCCESS ) 
                return false;
        return true;
}



void ImageLoaderMachO::mapSegments(int fd, uint64_t offsetInFat, uint64_t lenInFat, uint64_t fileLen, const LinkContext& context)
{
        // find address range for image
        intptr_t slide = this->assignSegmentAddresses(context);
        if ( context.verboseMapping )
                dyld::log("dyld: Mapping %s\n", this->getPath());
        // map in all segments
        for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                vm_offset_t fileOffset = segFileOffset(i) + offsetInFat;
                vm_size_t size = segFileSize(i);
                void* requestedLoadAddress = (void*)(segPreferredLoadAddress(i) + slide);
                int protection = 0;
                if ( !segUnaccessible(i) ) {
                        if ( segExecutable(i) )
                                protection   |= PROT_EXEC;
                        if ( segReadable(i) )
                                protection   |= PROT_READ;
                        if ( segWriteable(i) )
                                protection   |= PROT_WRITE;
                }
        #if __i386__
                // initially map __IMPORT segments R/W so dyld can update them
                if ( segIsReadOnlyImport(i) )
                        protection |= PROT_WRITE;
        #endif
                // wholly zero-fill segments have nothing to mmap() in
                if ( size > 0 ) {
                        if ( (fileOffset+size) > fileLen ) {
                                dyld::throwf("truncated mach-o error: segment %s extends to %llu which is past end of file %llu", 
                                                                segName(i), (uint64_t)(fileOffset+size), fileLen);
                        }
                        void* loadAddress = mmap(requestedLoadAddress, size, protection, MAP_FIXED | MAP_PRIVATE, fd, fileOffset);
                        if ( loadAddress == ((void*)(-1)) ) {
                                dyld::throwf("mmap() error %d at address=0x%08lX, size=0x%08lX segment=%s in Segment::map() mapping %s", 
                                        errno, (uintptr_t)requestedLoadAddress, (uintptr_t)size, segName(i), getPath());
                        }
                }
                // update stats
                ++ImageLoader::fgTotalSegmentsMapped;
                ImageLoader::fgTotalBytesMapped += size;
                if ( context.verboseMapping )
                        dyld::log("%18s at 0x%08lX->0x%08lX with permissions %c%c%c\n", segName(i), (uintptr_t)requestedLoadAddress, (uintptr_t)((char*)requestedLoadAddress+size-1),
                                (protection & PROT_READ) ? 'r' : '.',  (protection & PROT_WRITE) ? 'w' : '.',  (protection & PROT_EXEC) ? 'x' : '.' );
        }
        // update slide to reflect load location                        
        this->setSlide(slide);
}

void ImageLoaderMachO::mapSegments(const void* memoryImage, uint64_t imageLen, const LinkContext& context)
{
        // find address range for image
        intptr_t slide = this->assignSegmentAddresses(context);
        if ( context.verboseMapping )
                dyld::log("dyld: Mapping memory %p\n", memoryImage);
        // map in all segments
        for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                vm_address_t loadAddress = segPreferredLoadAddress(i) + slide;
                vm_address_t srcAddr = (uintptr_t)memoryImage + segFileOffset(i);
                vm_size_t size = segFileSize(i);
                kern_return_t r = vm_copy(mach_task_self(), srcAddr, size, loadAddress);
                if ( r != KERN_SUCCESS ) 
                        throw "can't map segment";
                if ( context.verboseMapping )
                        dyld::log("%18s at 0x%08lX->0x%08lX\n", segName(i), (uintptr_t)loadAddress, (uintptr_t)loadAddress+size-1);
        }
        // update slide to reflect load location                        
        this->setSlide(slide);
        // set R/W permissions on all segments at slide location
        for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                segProtect(i, context);         
        }
}


void ImageLoaderMachO::segProtect(unsigned int segIndex, const ImageLoader::LinkContext& context)
{
        vm_prot_t protection = 0;
        if ( !segUnaccessible(segIndex) ) {
                if ( segExecutable(segIndex) )
                        protection   |= PROT_EXEC;
                if ( segReadable(segIndex) )
                        protection   |= PROT_READ;
                if ( segWriteable(segIndex) )
                        protection   |= PROT_WRITE;
        }
        vm_address_t addr = segActualLoadAddress(segIndex);
        vm_size_t size = segSize(segIndex);
        const bool setCurrentPermissions = false;
        kern_return_t r = vm_protect(mach_task_self(), addr, size, setCurrentPermissions, protection);
        if ( r != KERN_SUCCESS ) 
                throw "can't set vm permissions for mapped segment";
        if ( context.verboseMapping ) {
                dyld::log("%18s at 0x%08lX->0x%08lX altered permissions to %c%c%c\n", segName(segIndex), (uintptr_t)addr, (uintptr_t)addr+size-1,
                        (protection & PROT_READ) ? 'r' : '.',  (protection & PROT_WRITE) ? 'w' : '.',  (protection & PROT_EXEC) ? 'x' : '.' );
        }
}       

void ImageLoaderMachO::segMakeWritable(unsigned int segIndex, const ImageLoader::LinkContext& context)
{
        vm_address_t addr = segActualLoadAddress(segIndex);
        vm_size_t size = segSize(segIndex);
        const bool setCurrentPermissions = false;
        vm_prot_t protection = VM_PROT_WRITE | VM_PROT_READ;
        if ( segExecutable(segIndex) )
                protection |= VM_PROT_EXECUTE;
        kern_return_t r = vm_protect(mach_task_self(), addr, size, setCurrentPermissions, protection);
        if ( r != KERN_SUCCESS ) 
                throw "can't set vm permissions for mapped segment";
        if ( context.verboseMapping ) {
                dyld::log("%18s at 0x%08lX->0x%08lX altered permissions to %c%c%c\n", segName(segIndex), (uintptr_t)addr, (uintptr_t)addr+size-1,
                        (protection & PROT_READ) ? 'r' : '.',  (protection & PROT_WRITE) ? 'w' : '.',  (protection & PROT_EXEC) ? 'x' : '.' );
        }
}