DyldSharedCache.cpp   [plain text]

/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
 *
 * Copyright (c) 2014 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */


#include <dirent.h>
#include <sys/errno.h>
#include <sys/fcntl.h>
#include <sys/param.h>
#include <mach/mach.h>
#include <mach-o/loader.h>
#include <mach-o/fat.h>
#include <mach-o/dyld_priv.h>
#include <assert.h>
#include <unistd.h>
#include <dlfcn.h>
#include <CommonCrypto/CommonDigest.h>
#include <CommonCrypto/CommonDigestSPI.h>

#if BUILDING_CACHE_BUILDER
#include <set>
#include <string>
#include <vector>
#include <unordered_map>
#include <unordered_set>
#endif

#define NO_ULEB
#include "MachOLoaded.h"
#include "ClosureFileSystemPhysical.h"
#include "CacheBuilder.h"
#include "DyldSharedCache.h"
#include "Trie.hpp"
#include "StringUtils.h"
#include "FileUtils.h"



#if BUILDING_CACHE_BUILDER
DyldSharedCache::CreateResults DyldSharedCache::create(const CreateOptions&             options,
                                                       const std::vector<MappedMachO>&  dylibsToCache,
                                                       const std::vector<MappedMachO>&  otherOsDylibs,
                                                       const std::vector<MappedMachO>&  osExecutables)
{
    CreateResults  results;
    const char* prefix = nullptr;
    if ( (options.pathPrefixes.size() == 1) && !options.pathPrefixes[0].empty() )
        prefix = options.pathPrefixes[0].c_str();
    // FIXME: This prefix will be applied to dylib closures and executable closures, even though
    // the old code didn't have a prefix on cache dylib closures
    dyld3::closure::FileSystemPhysical fileSystem(prefix);
    CacheBuilder   cache(options, fileSystem);
    if (!cache.errorMessage().empty()) {
        results.errorMessage = cache.errorMessage();
        return results;
    }

    std::vector<FileAlias> aliases;
    switch ( options.platform ) {
        case dyld3::Platform::iOS:
        case dyld3::Platform::watchOS:
        case dyld3::Platform::tvOS:
            // FIXME: embedded cache builds should be getting aliases from manifest
            aliases.push_back({"/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit", "/System/Library/Frameworks/IOKit.framework/IOKit"});
            aliases.push_back({"/usr/lib/libstdc++.6.dylib",                                  "/usr/lib/libstdc++.dylib"});
            aliases.push_back({"/usr/lib/libstdc++.6.dylib",                                  "/usr/lib/libstdc++.6.0.9.dylib"});
            aliases.push_back({"/usr/lib/libz.1.dylib",                                       "/usr/lib/libz.dylib"});
            aliases.push_back({"/usr/lib/libSystem.B.dylib",                                  "/usr/lib/libSystem.dylib"});
            break;
        default:
            break;
    }

    cache.build(dylibsToCache, otherOsDylibs, osExecutables, aliases);

    results.agileSignature = cache.agileSignature();
    results.cdHashFirst    = cache.cdHashFirst();
    results.cdHashSecond   = cache.cdHashSecond();
    results.warnings       = cache.warnings();
    results.evictions      = cache.evictions();
    if ( cache.errorMessage().empty() ) {
        if ( !options.outputFilePath.empty() )  {
            // write cache file, if path non-empty
            cache.writeFile(options.outputFilePath);
        }
        if ( !options.outputMapFilePath.empty() ) {
            // write map file, if path non-empty
            cache.writeMapFile(options.outputMapFilePath);
        }
    }
    results.errorMessage = cache.errorMessage();
    cache.deleteBuffer();
    return results;
}

bool DyldSharedCache::verifySelfContained(std::vector<MappedMachO>& dylibsToCache, MappedMachO (^loader)(const std::string& runtimePath), std::vector<std::pair<DyldSharedCache::MappedMachO, std::set<std::string>>>& rejected)
{
    // build map of dylibs
    __block std::map<std::string, std::set<std::string>> badDylibs;
    __block std::set<std::string> knownDylibs;
    for (const DyldSharedCache::MappedMachO& dylib : dylibsToCache) {
        std::set<std::string> reasons;
        if ( dylib.mh->canBePlacedInDyldCache(dylib.runtimePath.c_str(), ^(const char* msg) { badDylibs[dylib.runtimePath].insert(msg);}) ) {
            knownDylibs.insert(dylib.runtimePath);
            knownDylibs.insert(dylib.mh->installName());
        }
    }

    // check all dependencies to assure every dylib in cache only depends on other dylibs in cache
    __block bool doAgain = true;
    while ( doAgain ) {
        __block std::vector<DyldSharedCache::MappedMachO> foundMappings;
        doAgain = false;
        // scan dylib list making sure all dependents are in dylib list
        for (const DyldSharedCache::MappedMachO& dylib : dylibsToCache) {
            if ( badDylibs.count(dylib.runtimePath) != 0 )
                continue;
            dylib.mh->forEachDependentDylib(^(const char* loadPath, bool isWeak, bool isReExport, bool isUpward, uint32_t compatVersion, uint32_t curVersion, bool& stop) {
                if ( knownDylibs.count(loadPath) == 0 ) {
                    doAgain = true;
                    MappedMachO foundMapping;
                    if ( badDylibs.count(loadPath) == 0 )
                        foundMapping = loader(loadPath);
                    if ( foundMapping.length == 0 ) {
                        badDylibs[dylib.runtimePath].insert(std::string("Could not find dependency '") + loadPath +"'");
                        knownDylibs.erase(dylib.runtimePath);
                        knownDylibs.erase(dylib.mh->installName());
                    }
                    else {
                        std::set<std::string> reasons;
                        if ( foundMapping.mh->canBePlacedInDyldCache(foundMapping.runtimePath.c_str(), ^(const char* msg) { badDylibs[foundMapping.runtimePath].insert(msg);})) {
                            // see if existing mapping was returned
                            bool alreadyInVector = false;
                            for (const MappedMachO& existing : dylibsToCache) {
                                if ( existing.mh == foundMapping.mh ) {
                                    alreadyInVector = true;
                                    break;
                                }
                            }
                            if ( !alreadyInVector )
                                foundMappings.push_back(foundMapping);
                            knownDylibs.insert(loadPath);
                            knownDylibs.insert(foundMapping.runtimePath);
                            knownDylibs.insert(foundMapping.mh->installName());
                        }
                   }
                }
            });
        }
        dylibsToCache.insert(dylibsToCache.end(), foundMappings.begin(), foundMappings.end());
        // remove bad dylibs
        const auto badDylibsCopy = badDylibs;
        dylibsToCache.erase(std::remove_if(dylibsToCache.begin(), dylibsToCache.end(), [&](const DyldSharedCache::MappedMachO& dylib) {
            auto i = badDylibsCopy.find(dylib.runtimePath);
            if ( i !=  badDylibsCopy.end()) {
                rejected.push_back(std::make_pair(dylib, i->second));
                return true;
             }
             else {
                return false;
             }
        }), dylibsToCache.end());
    }

    return badDylibs.empty();
}
#endif

void DyldSharedCache::forEachRegion(void (^handler)(const void* content, uint64_t vmAddr, uint64_t size, uint32_t permissions)) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    const dyld_cache_mapping_info* mappingsEnd = &mappings[header.mappingCount];
    for (const dyld_cache_mapping_info* m=mappings; m < mappingsEnd; ++m) {
        handler((char*)this + m->fileOffset, m->address, m->size, m->initProt);
    }
}

bool DyldSharedCache::inCache(const void* addr, size_t length, bool& readOnly) const
{
    // quick out if before start of cache
    if ( addr < this )
        return false;

    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    uintptr_t slide = (uintptr_t)this - (uintptr_t)(mappings[0].address);
    uintptr_t unslidStart = (uintptr_t)addr - slide;

    // quick out if after end of cache
    if ( unslidStart > (mappings[2].address + mappings[2].size) )
        return false;

    // walk cache regions
    const dyld_cache_mapping_info* mappingsEnd = &mappings[header.mappingCount];
    uintptr_t unslidEnd = unslidStart + length;
    for (const dyld_cache_mapping_info* m=mappings; m < mappingsEnd; ++m) {
        if ( (unslidStart >= m->address) && (unslidEnd < (m->address+m->size)) ) {
            readOnly = ((m->initProt & VM_PROT_WRITE) == 0);
            return true;
        }
    }

    return false;
}

void DyldSharedCache::forEachImage(void (^handler)(const mach_header* mh, const char* installName)) const
{
    const dyld_cache_image_info*   dylibs   = (dyld_cache_image_info*)((char*)this + header.imagesOffset);
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    if ( mappings[0].fileOffset != 0 )
        return;
    uint64_t firstImageOffset = 0;
    uint64_t firstRegionAddress = mappings[0].address;
    for (uint32_t i=0; i < header.imagesCount; ++i) {
        const char* dylibPath  = (char*)this + dylibs[i].pathFileOffset;
        uint64_t offset = dylibs[i].address - firstRegionAddress;
        if ( firstImageOffset == 0 )
            firstImageOffset = offset;
        // skip over aliases
        if ( dylibs[i].pathFileOffset < firstImageOffset)
            continue;
        const mach_header* mh = (mach_header*)((char*)this + offset);
        handler(mh, dylibPath);
    }
}

void DyldSharedCache::forEachImageEntry(void (^handler)(const char* path, uint64_t mTime, uint64_t inode)) const
{
    const dyld_cache_image_info*   dylibs   = (dyld_cache_image_info*)((char*)this + header.imagesOffset);
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    if ( mappings[0].fileOffset != 0 )
        return;
    uint64_t firstImageOffset = 0;
    uint64_t firstRegionAddress = mappings[0].address;
    for (uint32_t i=0; i < header.imagesCount; ++i) {
        const char* dylibPath  = (char*)this + dylibs[i].pathFileOffset;
        uint64_t offset = dylibs[i].address - firstRegionAddress;
        if ( firstImageOffset == 0 )
            firstImageOffset = offset;
        // skip over aliases
        if ( dylibs[i].pathFileOffset < firstImageOffset)
            continue;
        handler(dylibPath, dylibs[i].modTime, dylibs[i].inode);
    }
}

const mach_header* DyldSharedCache::getIndexedImageEntry(uint32_t index, uint64_t& mTime, uint64_t& inode) const
{
    const dyld_cache_image_info*   dylibs   = (dyld_cache_image_info*)((char*)this + header.imagesOffset);
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    mTime = dylibs[index].modTime;
    inode = dylibs[index].inode;
    return (mach_header*)((uint8_t*)this + dylibs[index].address - mappings[0].address);
}

void DyldSharedCache::forEachImageTextSegment(void (^handler)(uint64_t loadAddressUnslid, uint64_t textSegmentSize, const uuid_t dylibUUID, const char* installName, bool& stop)) const
{
    // check for old cache without imagesText array
    if ( header.mappingOffset < 123 )
        return;

    // walk imageText table and call callback for each entry
    const dyld_cache_image_text_info* imagesText = (dyld_cache_image_text_info*)((char*)this + header.imagesTextOffset);
    const dyld_cache_image_text_info* imagesTextEnd = &imagesText[header.imagesTextCount];
    bool stop = false;
    for (const dyld_cache_image_text_info* p=imagesText; p < imagesTextEnd && !stop; ++p) {
        handler(p->loadAddress, p->textSegmentSize, p->uuid, (char*)this + p->pathOffset, stop);
    }
}

bool DyldSharedCache::addressInText(uint32_t cacheOffset, uint32_t* imageIndex) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    if ( cacheOffset > mappings[0].size )
        return false;
    uint64_t targetAddr = mappings[0].address + cacheOffset;
    // walk imageText table and call callback for each entry
    const dyld_cache_image_text_info* imagesText = (dyld_cache_image_text_info*)((char*)this + header.imagesTextOffset);
    const dyld_cache_image_text_info* imagesTextEnd = &imagesText[header.imagesTextCount];
    for (const dyld_cache_image_text_info* p=imagesText; p < imagesTextEnd; ++p) {
        if ( (p->loadAddress <= targetAddr) && (targetAddr < p->loadAddress+p->textSegmentSize) ) {
            *imageIndex = (uint32_t)(p-imagesText);
            return true;
        }
    }
    return false;
}

const char* DyldSharedCache::archName() const
{
    const char* archSubString = ((char*)this) + 8;
    while (*archSubString == ' ')
        ++archSubString;
    return archSubString;
}


dyld3::Platform DyldSharedCache::platform() const
{
    return (dyld3::Platform)header.platform;
}

#if BUILDING_CACHE_BUILDER
std::string DyldSharedCache::mapFile() const
{
    __block std::string             result;
    __block std::vector<uint64_t>   regionStartAddresses;
    __block std::vector<uint64_t>   regionSizes;
    __block std::vector<uint64_t>   regionFileOffsets;

    result.reserve(256*1024);
    forEachRegion(^(const void* content, uint64_t vmAddr, uint64_t size, uint32_t permissions) {
        regionStartAddresses.push_back(vmAddr);
        regionSizes.push_back(size);
        regionFileOffsets.push_back((uint8_t*)content - (uint8_t*)this);
        char lineBuffer[256];
        const char* prot = "RW";
        if ( permissions == (VM_PROT_EXECUTE|VM_PROT_READ) )
            prot = "EX";
        else if ( permissions == VM_PROT_READ )
            prot = "RO";
        if ( size > 1024*1024 )
            sprintf(lineBuffer, "mapping  %s %4lluMB 0x%0llX -> 0x%0llX\n", prot, size/(1024*1024), vmAddr, vmAddr+size);
        else
            sprintf(lineBuffer, "mapping  %s %4lluKB 0x%0llX -> 0x%0llX\n", prot, size/1024,        vmAddr, vmAddr+size);
        result += lineBuffer;
    });

    // TODO:  add linkedit breakdown
    result += "\n\n";

    forEachImage(^(const mach_header* mh, const char* installName) {
        result += std::string(installName) + "\n";
        const dyld3::MachOFile* mf = (dyld3::MachOFile*)mh;
        mf->forEachSegment(^(const dyld3::MachOFile::SegmentInfo& info, bool& stop) {
            char lineBuffer[256];
            sprintf(lineBuffer, "\t%16s 0x%08llX -> 0x%08llX\n", info.segName, info.vmAddr, info.vmAddr+info.vmSize);
            result += lineBuffer;
        });
        result += "\n";
    });

    return result;
}
#endif


uint64_t DyldSharedCache::unslidLoadAddress() const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    return mappings[0].address;
}

void DyldSharedCache::getUUID(uuid_t uuid) const
{
    memcpy(uuid, header.uuid, sizeof(uuid_t));
}

uint64_t DyldSharedCache::mappedSize() const
{
    __block uint64_t startAddr = 0;
    __block uint64_t endAddr = 0;
    forEachRegion(^(const void* content, uint64_t vmAddr, uint64_t size, uint32_t permissions) {
        if ( startAddr == 0 )
            startAddr = vmAddr;
        uint64_t end = vmAddr+size;
        if ( end > endAddr )
            endAddr = end;
    });
    return (endAddr - startAddr);
}

bool DyldSharedCache::findMachHeaderImageIndex(const mach_header* mh, uint32_t& imageIndex) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    uintptr_t slide = (uintptr_t)this - (uintptr_t)(mappings[0].address);
    uint64_t unslidMh = (uintptr_t)mh - slide;
    const dyld_cache_image_info* dylibs = (dyld_cache_image_info*)((char*)this + header.imagesOffset);
    for (uint32_t i=0; i < header.imagesCount; ++i) {
        if ( dylibs[i].address == unslidMh ) {
            imageIndex = i;
            return true;
        }
    }
    return false;
}

bool DyldSharedCache::hasImagePath(const char* dylibPath, uint32_t& imageIndex) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    if ( mappings[0].fileOffset != 0 )
        return false;
    if ( header.mappingOffset >= 0x118 ) {
        uintptr_t      slide           = (uintptr_t)this - (uintptr_t)(mappings[0].address);
        const uint8_t* dylibTrieStart  = (uint8_t*)(this->header.dylibsTrieAddr + slide);
        const uint8_t* dylibTrieEnd    = dylibTrieStart + this->header.dylibsTrieSize;

        Diagnostics diag;
        const uint8_t* imageNode = dyld3::MachOLoaded::trieWalk(diag, dylibTrieStart, dylibTrieEnd, dylibPath);
        if ( imageNode != NULL ) {
            imageIndex = (uint32_t)dyld3::MachOFile::read_uleb128(diag, imageNode, dylibTrieEnd);
            return true;
        }
    }
    else {
        const dyld_cache_image_info* dylibs = (dyld_cache_image_info*)((char*)this + header.imagesOffset);
        uint64_t firstImageOffset = 0;
        uint64_t firstRegionAddress = mappings[0].address;
        for (uint32_t i=0; i < header.imagesCount; ++i) {
            const char* aPath  = (char*)this + dylibs[i].pathFileOffset;
            if ( strcmp(aPath, dylibPath) == 0 ) {
                imageIndex = i;
                return true;
            }
            uint64_t offset = dylibs[i].address - firstRegionAddress;
            if ( firstImageOffset == 0 )
                firstImageOffset = offset;
            // skip over aliases
            if ( dylibs[i].pathFileOffset < firstImageOffset)
                continue;
        }
    }

    return false;
}

const dyld3::closure::Image* DyldSharedCache::findDlopenOtherImage(const char* path) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    if ( mappings[0].fileOffset != 0 )
        return nullptr;
    if ( header.mappingOffset < sizeof(dyld_cache_header) )
        return nullptr;
    if ( header.otherImageArrayAddr == 0 )
        return nullptr;
    uintptr_t      slide           = (uintptr_t)this - (uintptr_t)(mappings[0].address);
    const uint8_t* dylibTrieStart  = (uint8_t*)(this->header.otherTrieAddr + slide);
    const uint8_t* dylibTrieEnd    = dylibTrieStart + this->header.otherTrieSize;

    Diagnostics diag;
    const uint8_t* imageNode = dyld3::MachOLoaded::trieWalk(diag, dylibTrieStart, dylibTrieEnd, path);
    if ( imageNode != NULL ) {
        dyld3::closure::ImageNum imageNum = (uint32_t)dyld3::MachOFile::read_uleb128(diag, imageNode, dylibTrieEnd);
        uint64_t arrayAddrOffset = header.otherImageArrayAddr - mappings[0].address;
        const dyld3::closure::ImageArray* otherImageArray = (dyld3::closure::ImageArray*)((char*)this + arrayAddrOffset);
        return otherImageArray->imageForNum(imageNum);
    }

    return nullptr;
}




const dyld3::closure::LaunchClosure* DyldSharedCache::findClosure(const char* executablePath) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    uintptr_t      slide                = (uintptr_t)this - (uintptr_t)(mappings[0].address);
    const uint8_t* executableTrieStart  = (uint8_t*)(this->header.progClosuresTrieAddr + slide);
    const uint8_t* executableTrieEnd    = executableTrieStart + this->header.progClosuresTrieSize;
    const uint8_t* closuresStart        = (uint8_t*)(this->header.progClosuresAddr + slide);

    Diagnostics diag;
    const uint8_t* imageNode = dyld3::MachOLoaded::trieWalk(diag, executableTrieStart, executableTrieEnd, executablePath);
    if ( (imageNode == NULL) && (strncmp(executablePath, "/System/", 8) == 0) ) {
        // anything in /System/ should have a closure.  Perhaps it was launched via symlink path
        char realPath[PATH_MAX];
        if ( realpath(executablePath, realPath) != NULL )
            imageNode = dyld3::MachOLoaded::trieWalk(diag, executableTrieStart, executableTrieEnd, realPath);
    }
    if ( imageNode != NULL ) {
        uint32_t closureOffset = (uint32_t)dyld3::MachOFile::read_uleb128(diag, imageNode, executableTrieEnd);
        if ( closureOffset < this->header.progClosuresSize )
            return (dyld3::closure::LaunchClosure*)((uint8_t*)closuresStart + closureOffset);
    }

    return nullptr;
}

#if !BUILDING_LIBDYLD && !BUILDING_DYLD
void DyldSharedCache::forEachLaunchClosure(void (^handler)(const char* executableRuntimePath, const dyld3::closure::LaunchClosure* closure)) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    uintptr_t      slide                = (uintptr_t)this - (uintptr_t)(mappings[0].address);
    const uint8_t* executableTrieStart  = (uint8_t*)(this->header.progClosuresTrieAddr + slide);
    const uint8_t* executableTrieEnd    = executableTrieStart + this->header.progClosuresTrieSize;
    const uint8_t* closuresStart        = (uint8_t*)(this->header.progClosuresAddr + slide);

    std::vector<DylibIndexTrie::Entry> closureEntries;
    if ( Trie<DylibIndex>::parseTrie(executableTrieStart, executableTrieEnd, closureEntries) ) {
        for (DylibIndexTrie::Entry& entry : closureEntries ) {
            uint32_t offset = entry.info.index;
            if ( offset < this->header.progClosuresSize )
                handler(entry.name.c_str(), (const dyld3::closure::LaunchClosure*)(closuresStart+offset));
        }
    }
}

void DyldSharedCache::forEachDlopenImage(void (^handler)(const char* runtimePath, const dyld3::closure::Image* image)) const
{
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    uintptr_t      slide           = (uintptr_t)this - (uintptr_t)(mappings[0].address);
    const uint8_t* otherTrieStart  = (uint8_t*)(this->header.otherTrieAddr + slide);
    const uint8_t* otherTrieEnd    = otherTrieStart + this->header.otherTrieSize;

    std::vector<DylibIndexTrie::Entry> otherEntries;
    if ( Trie<DylibIndex>::parseTrie(otherTrieStart, otherTrieEnd, otherEntries) ) {
        for (const DylibIndexTrie::Entry& entry : otherEntries ) {
            dyld3::closure::ImageNum imageNum = entry.info.index;
            uint64_t arrayAddrOffset = header.otherImageArrayAddr - mappings[0].address;
            const dyld3::closure::ImageArray* otherImageArray = (dyld3::closure::ImageArray*)((char*)this + arrayAddrOffset);
            handler(entry.name.c_str(), otherImageArray->imageForNum(imageNum));
        }
    }
}
#endif

const dyld3::closure::ImageArray* DyldSharedCache::cachedDylibsImageArray() const
{
    // check for old cache without imagesArray
    if ( header.mappingOffset < 0x100 )
        return nullptr;

    if ( header.dylibsImageArrayAddr == 0 )
        return nullptr;
        
    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    uint64_t arrayAddrOffset = header.dylibsImageArrayAddr - mappings[0].address;
    return (dyld3::closure::ImageArray*)((char*)this + arrayAddrOffset);
}

const dyld3::closure::ImageArray* DyldSharedCache::otherOSImageArray() const
{
    // check for old cache without imagesArray
    if ( header.mappingOffset < sizeof(dyld_cache_header) )
        return nullptr;

    if ( header.otherImageArrayAddr == 0 )
        return nullptr;

    const dyld_cache_mapping_info* mappings = (dyld_cache_mapping_info*)((char*)this + header.mappingOffset);
    uint64_t arrayAddrOffset = header.otherImageArrayAddr - mappings[0].address;
    return (dyld3::closure::ImageArray*)((char*)this + arrayAddrOffset);
}