dyld-851.27.tar.gz

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

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2004-2010 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#define __STDC_LIMIT_MACROS
#include <stdint.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <mach/mach.h>
#include <mach-o/fat.h> 
#include <sys/types.h>
#include <sys/stat.h> 
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <libkern/OSAtomic.h>
#include <string_view>

#include <atomic>

#include "Tracing.h"

#include "ImageLoader.h"


uint32_t                                                                ImageLoader::fgImagesUsedFromSharedCache = 0;
uint32_t                                                                ImageLoader::fgImagesWithUsedPrebinding = 0;
uint32_t                                                                ImageLoader::fgImagesRequiringCoalescing = 0;
uint32_t                                                                ImageLoader::fgImagesHasWeakDefinitions = 0;
uint32_t                                                                ImageLoader::fgTotalRebaseFixups = 0;
uint32_t                                                                ImageLoader::fgTotalBindFixups = 0;
uint32_t                                                                ImageLoader::fgTotalBindSymbolsResolved = 0;
uint32_t                                                                ImageLoader::fgTotalBindImageSearches = 0;
uint32_t                                                                ImageLoader::fgTotalLazyBindFixups = 0;
uint32_t                                                                ImageLoader::fgTotalPossibleLazyBindFixups = 0;
uint32_t                                                                ImageLoader::fgTotalSegmentsMapped = 0;
uint64_t                                                                ImageLoader::fgTotalBytesMapped = 0;
uint64_t                                                                ImageLoader::fgTotalLoadLibrariesTime;
uint64_t                                                                ImageLoader::fgTotalObjCSetupTime = 0;
uint64_t                                                                ImageLoader::fgTotalDebuggerPausedTime = 0;
uint64_t                                                                ImageLoader::fgTotalRebindCacheTime = 0;
uint64_t                                                                ImageLoader::fgTotalRebaseTime;
uint64_t                                                                ImageLoader::fgTotalBindTime;
uint64_t                                                                ImageLoader::fgTotalWeakBindTime;
uint64_t                                                                ImageLoader::fgTotalDOF;
uint64_t                                                                ImageLoader::fgTotalInitTime;
uint16_t                                                                ImageLoader::fgLoadOrdinal = 0;
uint32_t                                                                ImageLoader::fgSymbolTrieSearchs = 0;
std::vector<ImageLoader::InterposeTuple>ImageLoader::fgInterposingTuples;
uintptr_t                                                               ImageLoader::fgNextPIEDylibAddress = 0;



ImageLoader::ImageLoader(const char* path, unsigned int libCount)
        : fPath(path), fRealPath(NULL), fDevice(0), fInode(0), fLastModified(0),
        fPathHash(0), fDlopenReferenceCount(0), fInitializerRecursiveLock(NULL), 
        fLoadOrder(fgLoadOrdinal++), fDepth(0), fObjCMappedNotified(false), fState(0), fLibraryCount(libCount),
        fMadeReadOnly(false), fAllLibraryChecksumsAndLoadAddressesMatch(false), fLeaveMapped(false), fNeverUnload(false),
        fHideSymbols(false), fMatchByInstallName(false),
        fInterposed(false), fRegisteredDOF(false), fAllLazyPointersBound(false), 
    fBeingRemoved(false), fAddFuncNotified(false),
        fPathOwnedByImage(false), fIsReferencedDownward(false), 
        fWeakSymbolsBound(false)
{
#if __x86_64__
        fAotPath = NULL;
#endif
        if ( fPath != NULL )
                fPathHash = hash(fPath);
        if ( libCount > 512 )
                dyld::throwf("too many dependent dylibs in %s", path);
}


void ImageLoader::deleteImage(ImageLoader* image)
{
        delete image;
}


ImageLoader::~ImageLoader()
{
        if ( fRealPath != NULL ) 
                delete [] fRealPath;
        if ( fPathOwnedByImage && (fPath != NULL) ) 
                delete [] fPath;
#if __x86_64__
        if ( fAotPath != NULL )
                delete [] fAotPath;
#endif
}

void ImageLoader::setFileInfo(dev_t device, ino_t inode, time_t modDate)
{
        fDevice = device;
        fInode = inode;
        fLastModified = modDate;
}

void ImageLoader::setMapped(const LinkContext& context)
{
        fState = dyld_image_state_mapped;
        context.notifySingle(dyld_image_state_mapped, this, NULL);  // note: can throw exception
}

int ImageLoader::compare(const ImageLoader* right) const
{
        if ( this->fDepth == right->fDepth ) {
                if ( this->fLoadOrder == right->fLoadOrder )
                        return 0;
                else if ( this->fLoadOrder < right->fLoadOrder )
                        return -1;
                else
                        return 1;
        }
        else {
                if ( this->fDepth < right->fDepth )
                        return -1;
                else
                        return 1;
        }
}

void ImageLoader::setPath(const char* path)
{
        if ( fPathOwnedByImage && (fPath != NULL) )
                delete [] fPath;
        fPath = new char[strlen(path)+1];
        strcpy((char*)fPath, path);
        fPathOwnedByImage = true;  // delete fPath when this image is destructed
        fPathHash = hash(fPath);
        if ( fRealPath != NULL ) {
                delete [] fRealPath;
                fRealPath = NULL;
        }
}

void ImageLoader::setPathUnowned(const char* path)
{
        if ( fPathOwnedByImage && (fPath != NULL) ) {
                delete [] fPath;
        }
        fPath = path;
        fPathOwnedByImage = false;
        fPathHash = hash(fPath);
}

void ImageLoader::setPaths(const char* path, const char* realPath)
{
        this->setPath(path);
        fRealPath = new char[strlen(realPath)+1];
        strcpy((char*)fRealPath, realPath);
}


const char* ImageLoader::getRealPath() const
{
        if ( fRealPath != NULL )
                return fRealPath;
        else
                return fPath;
}

uint32_t ImageLoader::hash(const char* path)
{
        // this does not need to be a great hash
        // it is just used to reduce the number of strcmp() calls
        // of existing images when loading a new image
        uint32_t h = 0;
        for (const char* s=path; *s != '\0'; ++s)
                h = h*5 + *s;
        return h;
}

bool ImageLoader::matchInstallPath() const
{
        return fMatchByInstallName;
}

void ImageLoader::setMatchInstallPath(bool match)
{
        fMatchByInstallName = match;
}

bool ImageLoader::statMatch(const struct stat& stat_buf) const
{
        return ( (this->fDevice == stat_buf.st_dev) && (this->fInode == stat_buf.st_ino) );     
}

const char* ImageLoader::shortName(const char* fullName)
{
        // try to return leaf name
        if ( fullName != NULL ) {
                const char* s = strrchr(fullName, '/');
                if ( s != NULL ) 
                        return &s[1];
        }
        return fullName;
}

const char* ImageLoader::getShortName() const
{
        return shortName(fPath);
}

void ImageLoader::setLeaveMapped()
{
        fLeaveMapped = true;
}

void ImageLoader::setHideExports(bool hide)
{
        fHideSymbols = hide;
}

bool ImageLoader::hasHiddenExports() const
{
        return fHideSymbols;
}

bool ImageLoader::isLinked() const
{
        return (fState >= dyld_image_state_bound);
}

time_t ImageLoader::lastModified() const
{
        return fLastModified;
}

bool ImageLoader::containsAddress(const void* addr) const
{
        for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                const uint8_t* start = (const uint8_t*)segActualLoadAddress(i);
                const uint8_t* end = (const uint8_t*)segActualEndAddress(i);
                if ( (start <= addr) && (addr < end) && !segUnaccessible(i) )
                        return true;
        }
        return false;
}

bool ImageLoader::overlapsWithAddressRange(const void* start, const void* end) const
{
        for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                const uint8_t* segStart = (const uint8_t*)segActualLoadAddress(i);
                const uint8_t* segEnd = (const uint8_t*)segActualEndAddress(i);
                if ( strcmp(segName(i), "__UNIXSTACK") == 0 ) {
                        // __UNIXSTACK never slides.  This is the only place that cares
                        // and checking for that segment name in segActualLoadAddress()
                        // is too expensive.
                        segStart -= getSlide();
                        segEnd -= getSlide();
                }
                if ( (start <= segStart) && (segStart < end) )
                        return true;
                if ( (start <= segEnd) && (segEnd < end) )
                        return true;
                if ( (segStart < start) && (end < segEnd) )
                        return true;
        }
        return false;
}

void ImageLoader::getMappedRegions(MappedRegion*& regions) const
{
        for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
                MappedRegion region;
                region.address = segActualLoadAddress(i);
                region.size = segSize(i);
                *regions++ = region;
        }
}



bool ImageLoader::dependsOn(ImageLoader* image) {
        for(unsigned int i=0; i < libraryCount(); ++i) {
                if ( libImage(i) == image )
                        return true;
        }
        return false;
}


static bool notInImgageList(const ImageLoader* image, const ImageLoader** dsiStart, const ImageLoader** dsiCur)
{
        for (const ImageLoader** p = dsiStart; p < dsiCur; ++p)
                if ( *p == image )
                        return false;
        return true;
}

bool ImageLoader::findExportedSymbolAddress(const LinkContext& context, const char* symbolName,
                                                                                        const ImageLoader* requestorImage, int requestorOrdinalOfDef,
                                                                                        bool runResolver, const ImageLoader** foundIn, uintptr_t* address) const
{
        const Symbol* sym = this->findExportedSymbol(symbolName, true, foundIn);
        if ( sym != NULL ) {
                *address = (*foundIn)->getExportedSymbolAddress(sym, context, requestorImage, runResolver);
                return true;
        }
        return false;
}


// private method that handles circular dependencies by only search any image once
const ImageLoader::Symbol* ImageLoader::findExportedSymbolInDependentImagesExcept(const char* name, 
                        const ImageLoader** dsiStart, const ImageLoader**& dsiCur, const ImageLoader** dsiEnd, const ImageLoader** foundIn) const
{
        const ImageLoader::Symbol* sym;
        // search self
        if ( notInImgageList(this, dsiStart, dsiCur) ) {
                sym = this->findExportedSymbol(name, false, this->getPath(), foundIn);
                if ( sym != NULL )
                        return sym;
                *dsiCur++ = this;
        }

        // search directly dependent libraries
        for(unsigned int i=0; i < libraryCount(); ++i) {
                ImageLoader* dependentImage = libImage(i);
                if ( (dependentImage != NULL) && notInImgageList(dependentImage, dsiStart, dsiCur) ) {
                        sym = dependentImage->findExportedSymbol(name, false, libPath(i), foundIn);
                        if ( sym != NULL )
                                return sym;
                }
        }
        
        // search indirectly dependent libraries
        for(unsigned int i=0; i < libraryCount(); ++i) {
                ImageLoader* dependentImage = libImage(i);
                if ( (dependentImage != NULL) && notInImgageList(dependentImage, dsiStart, dsiCur) ) {
                        *dsiCur++ = dependentImage; 
                        sym = dependentImage->findExportedSymbolInDependentImagesExcept(name, dsiStart, dsiCur, dsiEnd, foundIn);
                        if ( sym != NULL )
                                return sym;
                }
        }

        return NULL;
}


const ImageLoader::Symbol* ImageLoader::findExportedSymbolInDependentImages(const char* name, const LinkContext& context, const ImageLoader** foundIn) const
{
        unsigned int imageCount = context.imageCount()+2;
        const ImageLoader* dontSearchImages[imageCount];
        dontSearchImages[0] = this; // don't search this image
        const ImageLoader** cur = &dontSearchImages[1];
        return this->findExportedSymbolInDependentImagesExcept(name, &dontSearchImages[0], cur, &dontSearchImages[imageCount], foundIn);
}

const ImageLoader::Symbol* ImageLoader::findExportedSymbolInImageOrDependentImages(const char* name, const LinkContext& context, const ImageLoader** foundIn) const
{
        unsigned int imageCount = context.imageCount()+2;
        const ImageLoader* dontSearchImages[imageCount];
        const ImageLoader** cur = &dontSearchImages[0];
        return this->findExportedSymbolInDependentImagesExcept(name, &dontSearchImages[0], cur, &dontSearchImages[imageCount], foundIn);
}

// this is called by initializeMainExecutable() to interpose on the initial set of images
void ImageLoader::applyInterposing(const LinkContext& context)
{
        dyld3::ScopedTimer timer(DBG_DYLD_TIMING_APPLY_INTERPOSING, 0, 0, 0);
        if ( fgInterposingTuples.size() != 0 )
                this->recursiveApplyInterposing(context);
}


uintptr_t ImageLoader::interposedAddress(const LinkContext& context, uintptr_t address, const ImageLoader* inImage, const ImageLoader* onlyInImage)
{
        //dyld::log("interposedAddress(0x%08llX), tupleCount=%lu\n", (uint64_t)address, fgInterposingTuples.size());
        for (std::vector<InterposeTuple>::iterator it=fgInterposingTuples.begin(); it != fgInterposingTuples.end(); it++) {
                //dyld::log("    interposedAddress: replacee=0x%08llX, replacement=0x%08llX, neverImage=%p, onlyImage=%p, inImage=%p\n", 
                //                              (uint64_t)it->replacee, (uint64_t)it->replacement,  it->neverImage, it->onlyImage, inImage);
                // replace all references to 'replacee' with 'replacement'
                if ( (address == it->replacee) && (it->neverImage != inImage) && ((it->onlyImage == NULL) || (it->onlyImage == inImage)) ) {
                        if ( context.verboseInterposing ) {
                                dyld::log("dyld interposing: replace 0x%lX with 0x%lX\n", it->replacee, it->replacement);
                        }
                        return it->replacement;
                }
        }
        return address;
}

void ImageLoader::applyInterposingToDyldCache(const LinkContext& context) {
        if (!context.dyldCache)
                return;
        if (!context.dyldCache->header.builtFromChainedFixups)
                return;
        if (fgInterposingTuples.empty())
                return;

        // make the cache writable for this block
        DyldSharedCache::DataConstScopedWriter patcher(context.dyldCache, mach_task_self(), (context.verboseMapping ? &dyld::log : nullptr));

        // For each of the interposed addresses, see if any of them are in the shared cache.  If so, find
        // that image and apply its patch table to all uses.
        uintptr_t cacheStart = (uintptr_t)context.dyldCache;
        for (std::vector<InterposeTuple>::iterator it=fgInterposingTuples.begin(); it != fgInterposingTuples.end(); it++) {
                if ( context.verboseInterposing )
                        dyld::log("dyld: interpose: Trying to interpose address 0x%08llx\n", (uint64_t)it->replacee);
                uint32_t imageIndex;
                uint32_t cacheOffsetOfReplacee = (uint32_t)(it->replacee - cacheStart);
                if (!context.dyldCache->addressInText(cacheOffsetOfReplacee, &imageIndex))
                        continue;
                dyld3::closure::ImageNum imageInCache = imageIndex+1;
                if ( context.verboseInterposing )
                        dyld::log("dyld: interpose: Found shared cache image %d for 0x%08llx\n", imageInCache, (uint64_t)it->replacee);
                context.dyldCache->forEachPatchableExport(imageIndex, ^(uint32_t cacheOffsetOfImpl, const char* exportName) {
                        // Skip patching anything other than this symbol
                        if (cacheOffsetOfImpl != cacheOffsetOfReplacee)
                                return;
                        if ( context.verboseInterposing ) {
                                const dyld3::closure::Image* image = context.dyldCache->cachedDylibsImageArray()->imageForNum(imageInCache);
                                dyld::log("dyld: interpose: Patching uses of symbol %s in shared cache binary at %s\n", exportName, image->path());
                        }
                        uintptr_t newLoc = it->replacement;
                        context.dyldCache->forEachPatchableUseOfExport(imageIndex, cacheOffsetOfImpl, ^(dyld_cache_patchable_location patchLocation) {
                                uintptr_t* loc = (uintptr_t*)(cacheStart+patchLocation.cacheOffset);
#if __has_feature(ptrauth_calls)
                                if ( patchLocation.authenticated ) {
                                        dyld3::MachOLoaded::ChainedFixupPointerOnDisk ptr = *(dyld3::MachOLoaded::ChainedFixupPointerOnDisk*)loc;
                                        ptr.arm64e.authRebase.auth      = true;
                                        ptr.arm64e.authRebase.addrDiv   = patchLocation.usesAddressDiversity;
                                        ptr.arm64e.authRebase.diversity = patchLocation.discriminator;
                                        ptr.arm64e.authRebase.key       = patchLocation.key;
                                        *loc = ptr.arm64e.signPointer(loc, newLoc + DyldSharedCache::getAddend(patchLocation));
                                        if ( context.verboseInterposing )
                                                dyld::log("dyld: interpose: *%p = %p (JOP: diversity 0x%04X, addr-div=%d, key=%s)\n",
                                                                  loc, (void*)*loc, patchLocation.discriminator, patchLocation.usesAddressDiversity, DyldSharedCache::keyName(patchLocation));
                                        return;
                                }
#endif
                                if ( context.verboseInterposing )
                                        dyld::log("dyld: interpose: *%p = 0x%0llX (dyld cache patch) to %s\n", loc, newLoc + DyldSharedCache::getAddend(patchLocation), exportName);
                                *loc = newLoc + (uintptr_t)DyldSharedCache::getAddend(patchLocation);
                        });
                });
        }
}

void ImageLoader::addDynamicInterposingTuples(const struct dyld_interpose_tuple array[], size_t count)
{
        for(size_t i=0; i < count; ++i) {
                ImageLoader::InterposeTuple tuple;
                tuple.replacement               = (uintptr_t)array[i].replacement;
                tuple.neverImage                = NULL;
                tuple.onlyImage             = this;
                tuple.replacee                  = (uintptr_t)array[i].replacee;
                // chain to any existing interpositions
                for (std::vector<InterposeTuple>::iterator it=fgInterposingTuples.begin(); it != fgInterposingTuples.end(); it++) {
                        if ( (it->replacee == tuple.replacee) && (it->onlyImage == this) ) {
                                tuple.replacee = it->replacement;
                        }
                }
                ImageLoader::fgInterposingTuples.push_back(tuple);
        }
}

// <rdar://problem/29099600> dyld should tell the kernel when it is doing root fix-ups
void ImageLoader::vmAccountingSetSuspended(const LinkContext& context, bool suspend)
{
#if TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
        static bool sVmAccountingSuspended = false;
        if ( suspend == sVmAccountingSuspended )
                return;
    if ( context.verboseBind )
        dyld::log("set vm.footprint_suspend=%d\n", suspend);
    int newValue = suspend ? 1 : 0;
    int oldValue = 0;
    size_t newlen = sizeof(newValue);
    size_t oldlen = sizeof(oldValue);
    int ret = sysctlbyname("vm.footprint_suspend", &oldValue, &oldlen, &newValue, newlen);
    if ( context.verboseBind && (ret != 0) )
                dyld::log("vm.footprint_suspend => %d, errno=%d\n", ret, errno);
        sVmAccountingSuspended = suspend;
#endif
}


void ImageLoader::link(const LinkContext& context, bool forceLazysBound, bool preflightOnly, bool neverUnload, const RPathChain& loaderRPaths, const char* imagePath)
{
        //dyld::log("ImageLoader::link(%s) refCount=%d, neverUnload=%d\n", imagePath, fDlopenReferenceCount, fNeverUnload);
        
        // clear error strings
        (*context.setErrorStrings)(0, NULL, NULL, NULL);

        uint64_t t0 = mach_absolute_time();
        this->recursiveLoadLibraries(context, preflightOnly, loaderRPaths, imagePath);
        context.notifyBatch(dyld_image_state_dependents_mapped, preflightOnly);

        // we only do the loading step for preflights
        if ( preflightOnly )
                return;

        uint64_t t1 = mach_absolute_time();
        context.clearAllDepths();
        this->updateDepth(context.imageCount());

        __block uint64_t t2, t3, t4, t5;
        {
                dyld3::ScopedTimer(DBG_DYLD_TIMING_APPLY_FIXUPS, 0, 0, 0);
                t2 = mach_absolute_time();
                this->recursiveRebaseWithAccounting(context);
                context.notifyBatch(dyld_image_state_rebased, false);

                t3 = mach_absolute_time();
                if ( !context.linkingMainExecutable )
                        this->recursiveBindWithAccounting(context, forceLazysBound, neverUnload);

                t4 = mach_absolute_time();
                if ( !context.linkingMainExecutable )
                        this->weakBind(context);
                t5 = mach_absolute_time();
        }

        // interpose any dynamically loaded images
        if ( !context.linkingMainExecutable && (fgInterposingTuples.size() != 0) ) {
                dyld3::ScopedTimer timer(DBG_DYLD_TIMING_APPLY_INTERPOSING, 0, 0, 0);
                this->recursiveApplyInterposing(context);
        }

        // now that all fixups are done, make __DATA_CONST segments read-only
        if ( !context.linkingMainExecutable )
                this->recursiveMakeDataReadOnly(context);

    if ( !context.linkingMainExecutable )
        context.notifyBatch(dyld_image_state_bound, false);
        uint64_t t6 = mach_absolute_time();

        if ( context.registerDOFs != NULL ) {
                std::vector<DOFInfo> dofs;
                this->recursiveGetDOFSections(context, dofs);
                context.registerDOFs(dofs);
        }
        uint64_t t7 = mach_absolute_time();

        // clear error strings
        (*context.setErrorStrings)(0, NULL, NULL, NULL);

        fgTotalLoadLibrariesTime += t1 - t0;
        fgTotalRebaseTime += t3 - t2;
        fgTotalBindTime += t4 - t3;
        fgTotalWeakBindTime += t5 - t4;
        fgTotalDOF += t7 - t6;
        
        // done with initial dylib loads
        fgNextPIEDylibAddress = 0;
}


void ImageLoader::printReferenceCounts()
{
        dyld::log("      dlopen=%d for %s\n", fDlopenReferenceCount, getPath() );
}


bool ImageLoader::decrementDlopenReferenceCount() 
{
        if ( fDlopenReferenceCount == 0 )
                return true;
        --fDlopenReferenceCount;
        return false;
}


// <rdar://problem/14412057> upward dylib initializers can be run too soon
// To handle dangling dylibs which are upward linked but not downward, all upward linked dylibs
// have their initialization postponed until after the recursion through downward dylibs
// has completed.
void ImageLoader::processInitializers(const LinkContext& context, mach_port_t thisThread,
                                                                         InitializerTimingList& timingInfo, ImageLoader::UninitedUpwards& images)
{
        uint32_t maxImageCount = context.imageCount()+2;
        ImageLoader::UninitedUpwards upsBuffer[maxImageCount];
        ImageLoader::UninitedUpwards& ups = upsBuffer[0];
        ups.count = 0;
        // Calling recursive init on all images in images list, building a new list of
        // uninitialized upward dependencies.
        for (uintptr_t i=0; i < images.count; ++i) {
                images.imagesAndPaths[i].first->recursiveInitialization(context, thisThread, images.imagesAndPaths[i].second, timingInfo, ups);
        }
        // If any upward dependencies remain, init them.
        if ( ups.count > 0 )
                processInitializers(context, thisThread, timingInfo, ups);
}


void ImageLoader::runInitializers(const LinkContext& context, InitializerTimingList& timingInfo)
{
        uint64_t t1 = mach_absolute_time();
        mach_port_t thisThread = mach_thread_self();
        ImageLoader::UninitedUpwards up;
        up.count = 1;
        up.imagesAndPaths[0] = { this, this->getPath() };
        processInitializers(context, thisThread, timingInfo, up);
        context.notifyBatch(dyld_image_state_initialized, false);
        mach_port_deallocate(mach_task_self(), thisThread);
        uint64_t t2 = mach_absolute_time();
        fgTotalInitTime += (t2 - t1);
}


void ImageLoader::bindAllLazyPointers(const LinkContext& context, bool recursive)
{
        if ( ! fAllLazyPointersBound ) {
                fAllLazyPointersBound = true;

                if ( recursive ) {
                        // bind lower level libraries first
                        for(unsigned int i=0; i < libraryCount(); ++i) {
                                ImageLoader* dependentImage = libImage(i);
                                if ( dependentImage != NULL )
                                        dependentImage->bindAllLazyPointers(context, recursive);
                        }
                }
                // bind lazies in this image
                DyldSharedCache::DataConstLazyScopedWriter patcher(context.dyldCache, mach_task_self(), context.verboseMapping ? &dyld::log : nullptr);
                this->doBindJustLazies(context, patcher);
        }
}


bool ImageLoader::allDependentLibrariesAsWhenPreBound() const
{
        return fAllLibraryChecksumsAndLoadAddressesMatch;
}


void ImageLoader::markedUsedRecursive(const std::vector<DynamicReference>& dynamicReferences)
{
        // already visited here
        if ( fMarkedInUse )
                return;
        fMarkedInUse = true;
        
        // clear mark on all statically dependent dylibs
        for(unsigned int i=0; i < libraryCount(); ++i) {
                ImageLoader* dependentImage = libImage(i);
                if ( dependentImage != NULL ) {
                        dependentImage->markedUsedRecursive(dynamicReferences);
                }
        }
        
        // clear mark on all dynamically dependent dylibs
        for (std::vector<ImageLoader::DynamicReference>::const_iterator it=dynamicReferences.begin(); it != dynamicReferences.end(); ++it) {
                if ( it->from == this )
                        it->to->markedUsedRecursive(dynamicReferences);
        }
        
}

unsigned int ImageLoader::updateDepth(unsigned int maxDepth)
{
        STACK_ALLOC_ARRAY(ImageLoader*, danglingUpwards, maxDepth);
        unsigned int depth = this->recursiveUpdateDepth(maxDepth, danglingUpwards);
        for (auto& danglingUpward : danglingUpwards) {
                if ( danglingUpward->fDepth != 0)
                        continue;
                danglingUpward->recursiveUpdateDepth(maxDepth, danglingUpwards);
        }
        return depth;
}

unsigned int ImageLoader::recursiveUpdateDepth(unsigned int maxDepth, dyld3::Array<ImageLoader*>& danglingUpwards)
{
        // the purpose of this phase is to make the images sortable such that 
        // in a sort list of images, every image that an image depends on
        // occurs in the list before it.
        if ( fDepth == 0 ) {
                // break cycles
                fDepth = maxDepth;
                
                // get depth of dependents
                unsigned int minDependentDepth = maxDepth;
                for(unsigned int i=0; i < libraryCount(); ++i) {
                        ImageLoader* dependentImage = libImage(i);
                        if ( dependentImage != NULL ) {
                                if ( libIsUpward(i) ) {
                                        if ( dependentImage->fDepth == 0) {
                                                if ( !danglingUpwards.contains(dependentImage) )
                                                        danglingUpwards.push_back(dependentImage);
                                        }
                                } else {
                                        unsigned int d = dependentImage->recursiveUpdateDepth(maxDepth, danglingUpwards);
                                        if ( d < minDependentDepth )
                                                minDependentDepth = d;
                                }
                        }
                        // <rdar://problem/60878811> make sure need to re-bind propagates up
                        if ( dependentImage != NULL ) {
                                if ( fAllLibraryChecksumsAndLoadAddressesMatch && !dependentImage->fAllLibraryChecksumsAndLoadAddressesMatch ) {
                                        fAllLibraryChecksumsAndLoadAddressesMatch = false;
                                }
                        }
                }
                // make me less deep then all my dependents
                fDepth = minDependentDepth - 1;

        }
        return fDepth;
}


void ImageLoader::recursiveLoadLibraries(const LinkContext& context, bool preflightOnly, const RPathChain& loaderRPaths, const char* loadPath)
{
        if ( fState < dyld_image_state_dependents_mapped ) {
                // break cycles
                fState = dyld_image_state_dependents_mapped;
                
                // get list of libraries this image needs
                DependentLibraryInfo libraryInfos[fLibraryCount]; 
                this->doGetDependentLibraries(libraryInfos);
                
                // get list of rpaths that this image adds
                std::vector<const char*> rpathsFromThisImage;
                this->getRPaths(context, rpathsFromThisImage);
                const RPathChain thisRPaths(&loaderRPaths, &rpathsFromThisImage);
                
                // try to load each
                bool canUsePrelinkingInfo = true; 
                for(unsigned int i=0; i < fLibraryCount; ++i){
                        ImageLoader* dependentLib;
                        bool depLibReExported = false;
                        DependentLibraryInfo& requiredLibInfo = libraryInfos[i];
                        if ( preflightOnly && context.inSharedCache(requiredLibInfo.name) ) {
                                // <rdar://problem/5910137> dlopen_preflight() on image in shared cache leaves it loaded but not objc initialized
                                // in preflight mode, don't even load dylib that are in the shared cache because they will never be unloaded
                                setLibImage(i, NULL, false, false);
                                continue;
                        }
                        try {
                                unsigned cacheIndex;
                                dependentLib = context.loadLibrary(requiredLibInfo.name, true, this->getPath(), &thisRPaths, cacheIndex);
                                if ( dependentLib == this ) {
                                        // found circular reference, perhaps DYLD_LIBARY_PATH is causing this rdar://problem/3684168 
                                        dependentLib = context.loadLibrary(requiredLibInfo.name, false, NULL, NULL, cacheIndex);
                                        if ( dependentLib != this )
                                                dyld::warn("DYLD_ setting caused circular dependency in %s\n", this->getPath());
                                }
                                if ( fNeverUnload )
                                        dependentLib->setNeverUnload();
                                if ( requiredLibInfo.upward ) {
                                }
                                else { 
                                        dependentLib->fIsReferencedDownward = true;
                                }
                                LibraryInfo actualInfo = dependentLib->doGetLibraryInfo(requiredLibInfo.info);
                                depLibReExported = requiredLibInfo.reExported;
                                if ( ! depLibReExported ) {
                                        // for pre-10.5 binaries that did not use LC_REEXPORT_DYLIB
                                        depLibReExported = dependentLib->isSubframeworkOf(context, this) || this->hasSubLibrary(context, dependentLib);
                                }
                                // check found library version is compatible
                                // <rdar://problem/89200806> 0xFFFFFFFF is wildcard that matches any version
                                if ( (requiredLibInfo.info.minVersion != 0xFFFFFFFF) && (actualInfo.minVersion < requiredLibInfo.info.minVersion)
                                                && ((dyld3::MachOFile*)(dependentLib->machHeader()))->enforceCompatVersion() ) {
                                        // record values for possible use by CrashReporter or Finder
                                        dyld::throwf("Incompatible library version: %s requires version %d.%d.%d or later, but %s provides version %d.%d.%d",
                                                        this->getShortName(), requiredLibInfo.info.minVersion >> 16, (requiredLibInfo.info.minVersion >> 8) & 0xff, requiredLibInfo.info.minVersion & 0xff,
                                                        dependentLib->getShortName(), actualInfo.minVersion >> 16, (actualInfo.minVersion >> 8) & 0xff, actualInfo.minVersion & 0xff);
                                }
                                // prebinding for this image disabled if any dependent library changed
                                //if ( !depLibCheckSumsMatch )
                                //      canUsePrelinkingInfo = false;
                                // prebinding for this image disabled unless both this and dependent are in the shared cache
                                if ( !dependentLib->inSharedCache() || !this->inSharedCache() )
                                        canUsePrelinkingInfo = false;
                                        
                                //if ( context.verbosePrebinding ) {
                                //      if ( !requiredLib.checksumMatches )
                                //              fprintf(stderr, "dyld: checksum mismatch, (%u v %u) for %s referencing %s\n", 
                                //                      requiredLibInfo.info.checksum, actualInfo.checksum, this->getPath(),    dependentLib->getPath());               
                                //      if ( dependentLib->getSlide() != 0 )
                                //              fprintf(stderr, "dyld: dependent library slid for %s referencing %s\n", this->getPath(), dependentLib->getPath());              
                                //}
                        }
                        catch (const char* msg) {
                                //if ( context.verbosePrebinding )
                                //      fprintf(stderr, "dyld: exception during processing for %s referencing %s\n", this->getPath(), dependentLib->getPath());         
                                if ( requiredLibInfo.required ) {
                                        fState = dyld_image_state_mapped;
                                        // record values for possible use by CrashReporter or Finder
                                        if ( strstr(msg, "Incompatible library version") != NULL )
                                                (*context.setErrorStrings)(DYLD_EXIT_REASON_DYLIB_WRONG_VERSION, this->getPath(), requiredLibInfo.name, NULL);
                                        else if ( strstr(msg, "architecture") != NULL )
                                                (*context.setErrorStrings)(DYLD_EXIT_REASON_DYLIB_WRONG_ARCH, this->getPath(), requiredLibInfo.name, NULL);
                                        else if ( strstr(msg, "file system sandbox") != NULL )
                                                (*context.setErrorStrings)(DYLD_EXIT_REASON_FILE_SYSTEM_SANDBOX, this->getPath(), requiredLibInfo.name, NULL);
                                        else if ( strstr(msg, "code signature") != NULL )
                                                (*context.setErrorStrings)(DYLD_EXIT_REASON_CODE_SIGNATURE, this->getPath(), requiredLibInfo.name, NULL);
                                        else if ( strstr(msg, "malformed") != NULL )
                                                (*context.setErrorStrings)(DYLD_EXIT_REASON_MALFORMED_MACHO, this->getPath(), requiredLibInfo.name, NULL);
                                        else
                                                (*context.setErrorStrings)(DYLD_EXIT_REASON_DYLIB_MISSING, this->getPath(), requiredLibInfo.name, NULL);
                                        const char* newMsg = dyld::mkstringf("Library not loaded: %s\n  Referenced from: %s\n  Reason: %s", requiredLibInfo.name, this->getRealPath(), msg);
                                        free((void*)msg);       // our free() will do nothing if msg is a string literal
                                        throw newMsg;
                                }
                                free((void*)msg);       // our free() will do nothing if msg is a string literal
                                // ok if weak library not found
                                dependentLib = NULL;
                                canUsePrelinkingInfo = false;  // this disables all prebinding, we may want to just slam import vectors for this lib to zero
                        }
                        setLibImage(i, dependentLib, depLibReExported, requiredLibInfo.upward);
                }
                fAllLibraryChecksumsAndLoadAddressesMatch = canUsePrelinkingInfo;

                // tell each to load its dependents
                for(unsigned int i=0; i < libraryCount(); ++i) {
                        ImageLoader* dependentImage = libImage(i);
                        if ( dependentImage != NULL ) {
                                dependentImage->recursiveLoadLibraries(context, preflightOnly, thisRPaths, libraryInfos[i].name);
                        }
                }
                // do deep prebind check
                if ( fAllLibraryChecksumsAndLoadAddressesMatch ) {
                        for(unsigned int i=0; i < libraryCount(); ++i){
                                ImageLoader* dependentImage = libImage(i);
                                if ( dependentImage != NULL ) {
                                        if ( !dependentImage->allDependentLibrariesAsWhenPreBound() )
                                                fAllLibraryChecksumsAndLoadAddressesMatch = false;
                                }
                        }
                }

                // free rpaths (getRPaths() malloc'ed each string)
                for(std::vector<const char*>::iterator it=rpathsFromThisImage.begin(); it != rpathsFromThisImage.end(); ++it) {
                        const char* str = *it;
                        free((void*)str);
                }
                
        }
}


void ImageLoader::recursiveRebaseWithAccounting(const LinkContext& context)
{
        this->recursiveRebase(context);
        vmAccountingSetSuspended(context, false);
}

void ImageLoader::recursiveRebase(const LinkContext& context)
{ 
        if ( fState < dyld_image_state_rebased ) {
                // break cycles
                fState = dyld_image_state_rebased;
                
                try {
                        // rebase lower level libraries first
                        for(unsigned int i=0; i < libraryCount(); ++i) {
                                ImageLoader* dependentImage = libImage(i);
                                if ( dependentImage != NULL )
                                        dependentImage->recursiveRebase(context);
                        }
                                
                        // rebase this image
                        doRebase(context);
                        
                        // notify
                        context.notifySingle(dyld_image_state_rebased, this, NULL);
                }
                catch (const char* msg) {
                        // this image is not rebased
                        fState = dyld_image_state_dependents_mapped;
            CRSetCrashLogMessage2(NULL);
                        throw;
                }
        }
}

void ImageLoader::recursiveApplyInterposing(const LinkContext& context)
{ 
        if ( ! fInterposed ) {
                // break cycles
                fInterposed = true;
                
                try {
                        // interpose lower level libraries first
                        for(unsigned int i=0; i < libraryCount(); ++i) {
                                ImageLoader* dependentImage = libImage(i);
                                if ( dependentImage != NULL )
                                        dependentImage->recursiveApplyInterposing(context);
                        }
                                
                        // interpose this image
                        doInterpose(context);
                }
                catch (const char* msg) {
                        // this image is not interposed
                        fInterposed = false;
                        throw;
                }
        }
}

void ImageLoader::recursiveMakeDataReadOnly(const LinkContext& context)
{
        if ( ! fMadeReadOnly ) {
                // break cycles
                fMadeReadOnly = true;

                try {
                        // handle lower level libraries first
                        for(unsigned int i=0; i < libraryCount(); ++i) {
                                ImageLoader* dependentImage = libImage(i);
                                if ( dependentImage != NULL )
                                        dependentImage->recursiveMakeDataReadOnly(context);
                        }

                        // if this image has __DATA_CONST, make that segment read-only
                        makeDataReadOnly();
                }
                catch (const char* msg) {
                        fMadeReadOnly = false;
                        throw;
                }
        }
}


void ImageLoader::recursiveBindWithAccounting(const LinkContext& context, bool forceLazysBound, bool neverUnload)
{
        this->recursiveBind(context, forceLazysBound, neverUnload, nullptr);
        vmAccountingSetSuspended(context, false);
}

void ImageLoader::recursiveBind(const LinkContext& context, bool forceLazysBound, bool neverUnload, const ImageLoader* parent)
{
        // Normally just non-lazy pointers are bound immediately.
        // The exceptions are:
        //   1) DYLD_BIND_AT_LAUNCH will cause lazy pointers to be bound immediately
        //   2) some API's (e.g. RTLD_NOW) can cause lazy pointers to be bound immediately
        if ( fState < dyld_image_state_bound ) {
                // break cycles
                fState = dyld_image_state_bound;
        
                try {
                        // bind lower level libraries first
                        for(unsigned int i=0; i < libraryCount(); ++i) {
                                ImageLoader* dependentImage = libImage(i);
                                if ( dependentImage != NULL )  {
                                        const ImageLoader* reExportParent = nullptr;
                                        if ( libReExported(i) )
                                                reExportParent = this;
                                        dependentImage->recursiveBind(context, forceLazysBound, neverUnload, reExportParent);
                                }
                        }
                        // bind this image
                        this->doBind(context, forceLazysBound, parent);
                        // mark if lazys are also bound
                        if ( forceLazysBound || this->usablePrebinding(context) )
                                fAllLazyPointersBound = true;
                        // mark as never-unload if requested
                        if ( neverUnload )
                                this->setNeverUnload();
                                
                        context.notifySingle(dyld_image_state_bound, this, NULL);
                }
                catch (const char* msg) {
                        // restore state
                        fState = dyld_image_state_rebased;
            CRSetCrashLogMessage2(NULL);
                        throw;
                }
        }
}



// These are mangled symbols for all the variants of operator new and delete
// which a main executable can define (non-weak) and override the
// weak-def implementation in the OS.
static const char* const sTreatAsWeak[] = {
    "__Znwm", "__ZnwmRKSt9nothrow_t",
    "__Znam", "__ZnamRKSt9nothrow_t",
    "__ZdlPv", "__ZdlPvRKSt9nothrow_t", "__ZdlPvm",
    "__ZdaPv", "__ZdaPvRKSt9nothrow_t", "__ZdaPvm",
    "__ZnwmSt11align_val_t", "__ZnwmSt11align_val_tRKSt9nothrow_t",
    "__ZnamSt11align_val_t", "__ZnamSt11align_val_tRKSt9nothrow_t",
    "__ZdlPvSt11align_val_t", "__ZdlPvSt11align_val_tRKSt9nothrow_t", "__ZdlPvmSt11align_val_t",
    "__ZdaPvSt11align_val_t", "__ZdaPvSt11align_val_tRKSt9nothrow_t", "__ZdaPvmSt11align_val_t"
};

size_t ImageLoader::HashCString::hash(const char* v) {
    // FIXME: Use hash<string_view> when it has the correct visibility markup
    return std::hash<std::string_view>{}(v);
}

bool ImageLoader::EqualCString::equal(const char* s1, const char* s2) {
    return strcmp(s1, s2) == 0;
}

void ImageLoader::weakBind(const LinkContext& context)
{

        if (!context.useNewWeakBind) {
                weakBindOld(context);
                return;
        }

        if ( context.verboseWeakBind )
                dyld::log("dyld: weak bind start:\n");
        uint64_t t1 = mach_absolute_time();

        // get set of ImageLoaders that participate in coalecsing
        ImageLoader* imagesNeedingCoalescing[fgImagesRequiringCoalescing];
        unsigned imageIndexes[fgImagesRequiringCoalescing];
        int count = context.getCoalescedImages(imagesNeedingCoalescing, imageIndexes);
        
        // count how many have not already had weakbinding done
        int countNotYetWeakBound = 0;
        int countOfImagesWithWeakDefinitionsNotInSharedCache = 0;
        for(int i=0; i < count; ++i) {
                if ( ! imagesNeedingCoalescing[i]->weakSymbolsBound(imageIndexes[i]) )
                        ++countNotYetWeakBound;
                if ( ! imagesNeedingCoalescing[i]->inSharedCache() )
                        ++countOfImagesWithWeakDefinitionsNotInSharedCache;
        }

        // don't need to do any coalescing if only one image has overrides, or all have already been done
        if ( (countOfImagesWithWeakDefinitionsNotInSharedCache > 0) && (countNotYetWeakBound > 0) ) {
                if (!context.weakDefMapInitialized) {
                        // Initialize the weak def map as the link context doesn't run static initializers
                        new (&context.weakDefMap) dyld3::Map<const char*, std::pair<const ImageLoader*, uintptr_t>, ImageLoader::HashCString, ImageLoader::EqualCString>();
                        context.weakDefMapInitialized = true;
                }

                // We might have to patch the shared cache __DATA_CONST.  In that case, we'll create just a single
                // patcher when needed.
                DyldSharedCache::DataConstLazyScopedWriter patcher(context.dyldCache, mach_task_self(), context.verboseMapping ? &dyld::log : nullptr);

#if TARGET_OS_OSX
          // only do alternate algorithm for dlopen(). Use traditional algorithm for launch
          if ( !context.linkingMainExecutable ) {
                  // Don't take the memory hit of weak defs on the launch path until we hit a dlopen with more weak symbols to bind
                  if (!context.weakDefMapProcessedLaunchDefs) {
                          context.weakDefMapProcessedLaunchDefs = true;

                          // Walk the nlist for all binaries from launch and fill in the map with any other weak defs
                          for (int i=0; i < count; ++i) {
                                  const ImageLoader* image = imagesNeedingCoalescing[i];
                                  // skip images without defs.  We've processed launch time refs already
                                  if ( !image->hasCoalescedExports() )
                                          continue;
                                  // Only process binaries which have had their weak symbols bound, ie, not the new ones we are processing now
                                  // from this dlopen
                                  if ( !image->weakSymbolsBound(imageIndexes[i]) )
                                          continue;

                                  Diagnostics diag;
                                  const dyld3::MachOAnalyzer* ma = (const dyld3::MachOAnalyzer*)image->machHeader();
                                  ma->forEachWeakDef(diag, ^(const char *symbolName, uint64_t imageOffset, bool isFromExportTrie) {
                                          uintptr_t targetAddr = (uintptr_t)ma + (uintptr_t)imageOffset;
                                          if ( isFromExportTrie ) {
                                                  // Avoid duplicating the string if we already have the symbol name
                                                  if ( context.weakDefMap.find(symbolName) != context.weakDefMap.end() )
                                                          return;
                                                  symbolName = strdup(symbolName);
                                          }
                                          context.weakDefMap.insert({ symbolName, { image, targetAddr } });
                                  });
                          }
                  }

                  // Walk the nlist for all binaries in dlopen and fill in the map with any other weak defs
                  for (int i=0; i < count; ++i) {
                          const ImageLoader* image = imagesNeedingCoalescing[i];
                          if ( image->weakSymbolsBound(imageIndexes[i]) )
                                  continue;
                          // skip images without defs.  We'll process refs later
                          if ( !image->hasCoalescedExports() )
                                  continue;
                          Diagnostics diag;
                          const dyld3::MachOAnalyzer* ma = (const dyld3::MachOAnalyzer*)image->machHeader();
                          ma->forEachWeakDef(diag, ^(const char *symbolName, uint64_t imageOffset, bool isFromExportTrie) {
                                  uintptr_t targetAddr = (uintptr_t)ma + (uintptr_t)imageOffset;
                                  if ( isFromExportTrie ) {
                                          // Avoid duplicating the string if we already have the symbol name
                                          if ( context.weakDefMap.find(symbolName) != context.weakDefMap.end() )
                                                  return;
                                          symbolName = strdup(symbolName);
                                  }
                                  context.weakDefMap.insert({ symbolName, { image, targetAddr } });
                          });
                  }
                // for all images that need weak binding
                for (int i=0; i < count; ++i) {
                        ImageLoader* imageBeingFixedUp = imagesNeedingCoalescing[i];
                        if ( imageBeingFixedUp->weakSymbolsBound(imageIndexes[i]) )
                                continue; // weak binding already completed
                        bool imageBeingFixedUpInCache = imageBeingFixedUp->inSharedCache();

                        if ( context.verboseWeakBind )
                                dyld::log("dyld: checking for weak symbols in %s\n", imageBeingFixedUp->getPath());
                        // for all symbols that need weak binding in this image
                        ImageLoader::CoalIterator coalIterator;
                        imageBeingFixedUp->initializeCoalIterator(coalIterator, i, imageIndexes[i]);
                        while ( !imageBeingFixedUp->incrementCoalIterator(coalIterator) ) {
                                const char*         nameToCoalesce = coalIterator.symbolName;
                                uintptr_t           targetAddr     = 0;
                                const ImageLoader*  targetImage;
                                // Seatch the map for a previous definition to use
                                auto weakDefIt = context.weakDefMap.find(nameToCoalesce);
                                if ( (weakDefIt != context.weakDefMap.end()) && (weakDefIt->second.first != nullptr) ) {
                                        // Found a previous defition
                                        targetImage = weakDefIt->second.first;
                                        targetAddr = weakDefIt->second.second;
                                } else {
                                        // scan all images looking for definition to use
                                        for (int j=0; j < count; ++j) {
                                                const ImageLoader* anImage = imagesNeedingCoalescing[j];
                                                bool anImageInCache = anImage->inSharedCache();
                                                // <rdar://problem/47986398> Don't look at images in dyld cache because cache is
                                                //  already coalesced.  Only images outside cache can potentially override something in cache.
                                                if ( anImageInCache && imageBeingFixedUpInCache )
                                                        continue;

                                                //dyld::log("looking for %s in %s\n", nameToCoalesce, anImage->getPath());
                                                const ImageLoader* foundIn;
                                                const Symbol* sym = anImage->findExportedSymbol(nameToCoalesce, false, &foundIn);
                                                if ( sym != NULL ) {
                                                        targetAddr = foundIn->getExportedSymbolAddress(sym, context);
                                                        targetImage = foundIn;
                                                        if ( context.verboseWeakBind )
                                                                dyld::log("dyld:   found weak %s at 0x%lX in %s\n", nameToCoalesce, targetAddr, foundIn->getPath());
                                                        break;
                                                }
                                        }
                                }
                                if ( (targetAddr != 0) && (coalIterator.image != targetImage) ) {
                                        if ( coalIterator.image->inSharedCache() )
                                                patcher.makeWriteable();
                                        coalIterator.image->updateUsesCoalIterator(coalIterator, targetAddr, (ImageLoader*)targetImage, 0, context);
                                        if (weakDefIt == context.weakDefMap.end()) {
                                                if (targetImage->neverUnload()) {
                                                        // Add never unload defs to the map for next time
                                                        context.weakDefMap.insert({ nameToCoalesce, { targetImage, targetAddr } });
                                                        if ( context.verboseWeakBind ) {
                                                                dyld::log("dyld: weak binding adding %s to map\n", nameToCoalesce);
                                                        }
                                                } else {
                                                        // Add a placeholder for unloadable symbols which makes us fall back to the regular search
                                                        context.weakDefMap.insert({ nameToCoalesce, { targetImage, targetAddr } });
                                                        if ( context.verboseWeakBind ) {
                                                                dyld::log("dyld: weak binding adding unloadable placeholder %s to map\n", nameToCoalesce);
                                                        }
                                                }
                                        }
                                        if ( context.verboseWeakBind )
                                                dyld::log("dyld:     adjusting uses of %s in %s to use definition from %s\n", nameToCoalesce, coalIterator.image->getPath(), targetImage->getPath());
                                }
                        }
                        imageBeingFixedUp->setWeakSymbolsBound(imageIndexes[i]);
                }
          }
          else
#endif // TARGET_OS_OSX
          {
                // make symbol iterators for each
                ImageLoader::CoalIterator iterators[count];
                ImageLoader::CoalIterator* sortedIts[count];
                for(int i=0; i < count; ++i) {
                        imagesNeedingCoalescing[i]->initializeCoalIterator(iterators[i], i, imageIndexes[i]);
                        sortedIts[i] = &iterators[i];
                        if ( context.verboseWeakBind )
                                dyld::log("dyld: weak bind load order %d/%d for %s\n", i, count, imagesNeedingCoalescing[i]->getIndexedPath(imageIndexes[i]));
                }
                
                // walk all symbols keeping iterators in sync by 
                // only ever incrementing the iterator with the lowest symbol 
                int doneCount = 0;
                while ( doneCount != count ) {
                        //for(int i=0; i < count; ++i)
                        //      dyld::log("sym[%d]=%s ", sortedIts[i]->loadOrder, sortedIts[i]->symbolName);
                        //dyld::log("\n");
                        // increment iterator with lowest symbol
                        if ( sortedIts[0]->image->incrementCoalIterator(*sortedIts[0]) )
                                ++doneCount; 
                        // re-sort iterators
                        for(int i=1; i < count; ++i) {
                                int result = strcmp(sortedIts[i-1]->symbolName, sortedIts[i]->symbolName);
                                if ( result == 0 )
                                        sortedIts[i-1]->symbolMatches = true;
                                if ( result > 0 ) {
                                        // new one is bigger then next, so swap
                                        ImageLoader::CoalIterator* temp = sortedIts[i-1];
                                        sortedIts[i-1] = sortedIts[i];
                                        sortedIts[i] = temp;
                                }
                                if ( result < 0 )
                                        break;
                        }
                        // process all matching symbols just before incrementing the lowest one that matches
                        if ( sortedIts[0]->symbolMatches && !sortedIts[0]->done ) {
                                const char* nameToCoalesce = sortedIts[0]->symbolName;
                                // pick first symbol in load order (and non-weak overrides weak)
                                uintptr_t targetAddr = 0;
                                ImageLoader* targetImage = NULL;
                                unsigned targetImageIndex = 0;
                                for(int i=0; i < count; ++i) {
                                        if ( strcmp(iterators[i].symbolName, nameToCoalesce) == 0 ) {
                                                if ( context.verboseWeakBind )
                                                        dyld::log("dyld: weak bind, found %s weak=%d in %s \n", nameToCoalesce, iterators[i].weakSymbol, iterators[i].image->getIndexedPath((unsigned)iterators[i].imageIndex));
                                                if ( iterators[i].weakSymbol ) {
                                                        if ( targetAddr == 0 ) {
                                                                targetAddr = iterators[i].image->getAddressCoalIterator(iterators[i], context);
                                                                if ( targetAddr != 0 ) {
                                                                        targetImage = iterators[i].image;
                                                                        targetImageIndex = (unsigned)iterators[i].imageIndex;
                                                                }
                                                        }
                                                }
                                                else {
                                                        targetAddr = iterators[i].image->getAddressCoalIterator(iterators[i], context);
                                                        if ( targetAddr != 0 ) {
                                                                targetImage = iterators[i].image;
                                                                targetImageIndex = (unsigned)iterators[i].imageIndex;
                                                                // strong implementation found, stop searching
                                                                break;
                                                        }
                                                }
                                        }
                                }
                                // tell each to bind to this symbol (unless already bound)
                                if ( targetAddr != 0 ) {
                                        if ( context.verboseWeakBind ) {
                                                dyld::log("dyld: weak binding all uses of %s to copy from %s\n",
                                                                        nameToCoalesce, targetImage->getIndexedShortName(targetImageIndex));
                                        }
                                        for(int i=0; i < count; ++i) {
                                                if ( strcmp(iterators[i].symbolName, nameToCoalesce) == 0 ) {
                                                        if ( context.verboseWeakBind ) {
                                                                dyld::log("dyld: weak bind, setting all uses of %s in %s to 0x%lX from %s\n",
                                                                                        nameToCoalesce, iterators[i].image->getIndexedShortName((unsigned)iterators[i].imageIndex),
                                                                                        targetAddr, targetImage->getIndexedShortName(targetImageIndex));
                                                        }
                                                        if ( ! iterators[i].image->weakSymbolsBound(imageIndexes[i]) ) {
                                                                if ( iterators[i].image->inSharedCache() )
                                                                        patcher.makeWriteable();
                                                                iterators[i].image->updateUsesCoalIterator(iterators[i], targetAddr, targetImage, targetImageIndex, context);
                                                        }
                                                        iterators[i].symbolMatches = false; 
                                                }
                                        }
                                        if (targetImage->neverUnload()) {
                                                // Add never unload defs to the map for next time
                                                context.weakDefMap.insert({ nameToCoalesce, { targetImage, targetAddr } });
                                                if ( context.verboseWeakBind ) {
                                                        dyld::log("dyld: weak binding adding %s to map\n",
                                                                                nameToCoalesce);
                                                }
                                        }
                                }

                        }
                }

                for (int i=0; i < count; ++i) {
                        if ( imagesNeedingCoalescing[i]->weakSymbolsBound(imageIndexes[i]) )
                                continue;       // skip images already processed

                        if ( imagesNeedingCoalescing[i]->usesChainedFixups() ) {
                                // during binding of references to weak-def symbols, the dyld cache was patched
                                // but if main executable has non-weak override of operator new or delete it needs is handled here
                                for (const char* weakSymbolName : sTreatAsWeak) {
                                        const ImageLoader* dummy;
                                        imagesNeedingCoalescing[i]->resolveWeak(context, weakSymbolName, true, false, &dummy, patcher);
                                }
                        }
#if __arm64e__
                        else {
                                // support traditional arm64 app on an arm64e device
                                // look for weak def symbols in this image which may override the cache
                                ImageLoader::CoalIterator coaler;
                                imagesNeedingCoalescing[i]->initializeCoalIterator(coaler, i, 0);
                                imagesNeedingCoalescing[i]->incrementCoalIterator(coaler);
                                while ( !coaler.done ) {
                                        const ImageLoader* dummy;
                                        // a side effect of resolveWeak() is to patch cache
                                        imagesNeedingCoalescing[i]->resolveWeak(context, coaler.symbolName, true, false, &dummy, patcher);
                                        imagesNeedingCoalescing[i]->incrementCoalIterator(coaler);
                                }
                        }
#endif
                }

                // mark all as having all weak symbols bound
                for(int i=0; i < count; ++i) {
                        imagesNeedingCoalescing[i]->setWeakSymbolsBound(imageIndexes[i]);
                }
          }
        }

        uint64_t t2 = mach_absolute_time();
        fgTotalWeakBindTime += t2  - t1;
        
        if ( context.verboseWeakBind )
                dyld::log("dyld: weak bind end\n");
}


void ImageLoader::weakBindOld(const LinkContext& context)
{
        if ( context.verboseWeakBind )
                dyld::log("dyld: weak bind start:\n");
        uint64_t t1 = mach_absolute_time();
        // get set of ImageLoaders that participate in coalecsing
        ImageLoader* imagesNeedingCoalescing[fgImagesRequiringCoalescing];
        unsigned imageIndexes[fgImagesRequiringCoalescing];
        int count = context.getCoalescedImages(imagesNeedingCoalescing, imageIndexes);

        // count how many have not already had weakbinding done
        int countNotYetWeakBound = 0;
        int countOfImagesWithWeakDefinitionsNotInSharedCache = 0;
        for(int i=0; i < count; ++i) {
                if ( ! imagesNeedingCoalescing[i]->weakSymbolsBound(imageIndexes[i]) )
                        ++countNotYetWeakBound;
                if ( ! imagesNeedingCoalescing[i]->inSharedCache() )
                        ++countOfImagesWithWeakDefinitionsNotInSharedCache;
        }

        // don't need to do any coalescing if only one image has overrides, or all have already been done
        if ( (countOfImagesWithWeakDefinitionsNotInSharedCache > 0) && (countNotYetWeakBound > 0) ) {
                // We might have to patch the shared cache __DATA_CONST.  In that case, we'll create just a single
                // patcher when needed.
                DyldSharedCache::DataConstLazyScopedWriter patcher(context.dyldCache, mach_task_self(), context.verboseMapping ? &dyld::log : nullptr);

#if TARGET_OS_OSX
          // only do alternate algorithm for dlopen(). Use traditional algorithm for launch
          if ( !context.linkingMainExecutable ) {
                // for all images that need weak binding
                for (int i=0; i < count; ++i) {
                        ImageLoader* imageBeingFixedUp = imagesNeedingCoalescing[i];
                        if ( imageBeingFixedUp->weakSymbolsBound(imageIndexes[i]) )
                                continue; // weak binding already completed
                        bool imageBeingFixedUpInCache = imageBeingFixedUp->inSharedCache();

                        if ( context.verboseWeakBind )
                                dyld::log("dyld: checking for weak symbols in %s\n", imageBeingFixedUp->getPath());
                        // for all symbols that need weak binding in this image
                        ImageLoader::CoalIterator coalIterator;
                        imageBeingFixedUp->initializeCoalIterator(coalIterator, i, imageIndexes[i]);
                        while ( !imageBeingFixedUp->incrementCoalIterator(coalIterator) ) {
                                const char*         nameToCoalesce = coalIterator.symbolName;
                                uintptr_t           targetAddr     = 0;
                                const ImageLoader*  targetImage;
                                // scan all images looking for definition to use
                                for (int j=0; j < count; ++j) {
                                        const ImageLoader* anImage = imagesNeedingCoalescing[j];
                                        bool anImageInCache = anImage->inSharedCache();
                                        // <rdar://problem/47986398> Don't look at images in dyld cache because cache is
                                        //  already coalesced.  Only images outside cache can potentially override something in cache.
                                        if ( anImageInCache && imageBeingFixedUpInCache )
                                                continue;

                                        //dyld::log("looking for %s in %s\n", nameToCoalesce, anImage->getPath());
                                        const ImageLoader* foundIn;
                                        const Symbol* sym = anImage->findExportedSymbol(nameToCoalesce, false, &foundIn);
                                        if ( sym != NULL ) {
                                                if ( (foundIn->getExportedSymbolInfo(sym) & ImageLoader::kWeakDefinition) == 0 ) {
                                                        // found non-weak def, use it and stop looking
                                                        targetAddr = foundIn->getExportedSymbolAddress(sym, context);
                                                        targetImage = foundIn;
                                                        if ( context.verboseWeakBind )
                                                                dyld::log("dyld:   found strong %s at 0x%lX in %s\n", nameToCoalesce, targetAddr, foundIn->getPath());
                                                        break;
                                                }
                                                else {
                                                        // found weak-def, only use if no weak found yet
                                                        if ( targetAddr == 0 ) {
                                                                targetAddr = foundIn->getExportedSymbolAddress(sym, context);
                                                                targetImage = foundIn;
                                                                if ( context.verboseWeakBind )
                                                                        dyld::log("dyld:   found weak %s at 0x%lX in %s\n", nameToCoalesce, targetAddr, foundIn->getPath());
                                                        }
                                                }
                                        }
                                }
                                if ( (targetAddr != 0) && (coalIterator.image != targetImage) ) {
                                        if ( coalIterator.image->inSharedCache() )
                                                patcher.makeWriteable();
                                        coalIterator.image->updateUsesCoalIterator(coalIterator, targetAddr, (ImageLoader*)targetImage, 0, context);
                                        if ( context.verboseWeakBind )
                                                dyld::log("dyld:     adjusting uses of %s in %s to use definition from %s\n", nameToCoalesce, coalIterator.image->getPath(), targetImage->getPath());
                                }
                        }
                        imageBeingFixedUp->setWeakSymbolsBound(imageIndexes[i]);
                }
          }
          else
#endif // TARGET_OS_OSX
          {
                // make symbol iterators for each
                ImageLoader::CoalIterator iterators[count];
                ImageLoader::CoalIterator* sortedIts[count];
                for(int i=0; i < count; ++i) {
                        imagesNeedingCoalescing[i]->initializeCoalIterator(iterators[i], i, imageIndexes[i]);
                        sortedIts[i] = &iterators[i];
                        if ( context.verboseWeakBind )
                                dyld::log("dyld: weak bind load order %d/%d for %s\n", i, count, imagesNeedingCoalescing[i]->getIndexedPath(imageIndexes[i]));
                }

                // walk all symbols keeping iterators in sync by
                // only ever incrementing the iterator with the lowest symbol
                int doneCount = 0;
                while ( doneCount != count ) {
                        //for(int i=0; i < count; ++i)
                        //      dyld::log("sym[%d]=%s ", sortedIts[i]->loadOrder, sortedIts[i]->symbolName);
                        //dyld::log("\n");
                        // increment iterator with lowest symbol
                        if ( sortedIts[0]->image->incrementCoalIterator(*sortedIts[0]) )
                                ++doneCount;
                        // re-sort iterators
                        for(int i=1; i < count; ++i) {
                                int result = strcmp(sortedIts[i-1]->symbolName, sortedIts[i]->symbolName);
                                if ( result == 0 )
                                        sortedIts[i-1]->symbolMatches = true;
                                if ( result > 0 ) {
                                        // new one is bigger then next, so swap
                                        ImageLoader::CoalIterator* temp = sortedIts[i-1];
                                        sortedIts[i-1] = sortedIts[i];
                                        sortedIts[i] = temp;
                                }
                                if ( result < 0 )
                                        break;
                        }
                        // process all matching symbols just before incrementing the lowest one that matches
                        if ( sortedIts[0]->symbolMatches && !sortedIts[0]->done ) {
                                const char* nameToCoalesce = sortedIts[0]->symbolName;
                                // pick first symbol in load order (and non-weak overrides weak)
                                uintptr_t targetAddr = 0;
                                ImageLoader* targetImage = NULL;
                                unsigned targetImageIndex = 0;
                                for(int i=0; i < count; ++i) {
                                        if ( strcmp(iterators[i].symbolName, nameToCoalesce) == 0 ) {
                                                if ( context.verboseWeakBind )
                                                        dyld::log("dyld: weak bind, found %s weak=%d in %s \n", nameToCoalesce, iterators[i].weakSymbol, iterators[i].image->getIndexedPath((unsigned)iterators[i].imageIndex));
                                                if ( iterators[i].weakSymbol ) {
                                                        if ( targetAddr == 0 ) {
                                                                targetAddr = iterators[i].image->getAddressCoalIterator(iterators[i], context);
                                                                if ( targetAddr != 0 ) {
                                                                        targetImage = iterators[i].image;
                                                                        targetImageIndex = (unsigned)iterators[i].imageIndex;
                                                                }
                                                        }
                                                }
                                                else {
                                                        targetAddr = iterators[i].image->getAddressCoalIterator(iterators[i], context);
                                                        if ( targetAddr != 0 ) {
                                                                targetImage = iterators[i].image;
                                                                targetImageIndex = (unsigned)iterators[i].imageIndex;
                                                                // strong implementation found, stop searching
                                                                break;
                                                        }
                                                }
                                        }
                                }
                                // tell each to bind to this symbol (unless already bound)
                                if ( targetAddr != 0 ) {
                                        if ( context.verboseWeakBind ) {
                                                dyld::log("dyld: weak binding all uses of %s to copy from %s\n",
                                                                        nameToCoalesce, targetImage->getIndexedShortName(targetImageIndex));
                                        }
                                        for(int i=0; i < count; ++i) {
                                                if ( strcmp(iterators[i].symbolName, nameToCoalesce) == 0 ) {
                                                        if ( context.verboseWeakBind ) {
                                                                dyld::log("dyld: weak bind, setting all uses of %s in %s to 0x%lX from %s\n",
                                                                                        nameToCoalesce, iterators[i].image->getIndexedShortName((unsigned)iterators[i].imageIndex),
                                                                                        targetAddr, targetImage->getIndexedShortName(targetImageIndex));
                                                        }
                                                        if ( ! iterators[i].image->weakSymbolsBound(imageIndexes[i]) ) {
                                                                if ( iterators[i].image->inSharedCache() )
                                                                        patcher.makeWriteable();
                                                                iterators[i].image->updateUsesCoalIterator(iterators[i], targetAddr, targetImage, targetImageIndex, context);
                                                        }
                                                        iterators[i].symbolMatches = false;
                                                }
                                        }
                                }

                        }
                }

                for (int i=0; i < count; ++i) {
                        if ( imagesNeedingCoalescing[i]->weakSymbolsBound(imageIndexes[i]) )
                                continue;       // skip images already processed

                        if ( imagesNeedingCoalescing[i]->usesChainedFixups() ) {
                                // during binding of references to weak-def symbols, the dyld cache was patched
                                // but if main executable has non-weak override of operator new or delete it needs is handled here
                                for (const char* weakSymbolName : sTreatAsWeak) {
                                        const ImageLoader* dummy;
                                        imagesNeedingCoalescing[i]->resolveWeak(context, weakSymbolName, true, false, &dummy, patcher);
                                }
                        }
#if __arm64e__
                        else {
                                // support traditional arm64 app on an arm64e device
                                // look for weak def symbols in this image which may override the cache
                                patcher.makeWriteable();
                                ImageLoader::CoalIterator coaler;
                                imagesNeedingCoalescing[i]->initializeCoalIterator(coaler, i, 0);
                                imagesNeedingCoalescing[i]->incrementCoalIterator(coaler);
                                while ( !coaler.done ) {
                                        const ImageLoader* dummy;
                                        // a side effect of resolveWeak() is to patch cache
                                        imagesNeedingCoalescing[i]->resolveWeak(context, coaler.symbolName, true, false, &dummy, patcher);
                                        imagesNeedingCoalescing[i]->incrementCoalIterator(coaler);
                                }
                        }
#endif
                }

                // mark all as having all weak symbols bound
                for(int i=0; i < count; ++i) {
                        imagesNeedingCoalescing[i]->setWeakSymbolsBound(imageIndexes[i]);
                }
          }
        }

        uint64_t t2 = mach_absolute_time();
        fgTotalWeakBindTime += t2  - t1;

        if ( context.verboseWeakBind )
                dyld::log("dyld: weak bind end\n");
}



void ImageLoader::recursiveGetDOFSections(const LinkContext& context, std::vector<DOFInfo>& dofs)
{
        if ( ! fRegisteredDOF ) {
                // break cycles
                fRegisteredDOF = true;
                
                // gather lower level libraries first
                for(unsigned int i=0; i < libraryCount(); ++i) {
                        ImageLoader* dependentImage = libImage(i);
                        if ( dependentImage != NULL )
                                dependentImage->recursiveGetDOFSections(context, dofs);
                }
                this->doGetDOFSections(context, dofs);
        }
}

void ImageLoader::setNeverUnloadRecursive() {
        if ( ! fNeverUnload ) {
                // break cycles
                fNeverUnload = true;
                
                // gather lower level libraries first
                for(unsigned int i=0; i < libraryCount(); ++i) {
                        ImageLoader* dependentImage = libImage(i);
                        if ( dependentImage != NULL )
                                dependentImage->setNeverUnloadRecursive();
                }
        }
}

void ImageLoader::recursiveSpinLock(recursive_lock& rlock)
{
        // try to set image's ivar fInitializerRecursiveLock to point to this lock_info
        // keep trying until success (spin)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
        while ( ! OSAtomicCompareAndSwapPtrBarrier(NULL, &rlock, (void**)&fInitializerRecursiveLock) ) {
                // if fInitializerRecursiveLock already points to a different lock_info, if it is for
                // the same thread we are on, the increment the lock count, otherwise continue to spin
                if ( (fInitializerRecursiveLock != NULL) && (fInitializerRecursiveLock->thread == rlock.thread) )
                        break;
        }
#pragma clang diagnostic pop
        ++(fInitializerRecursiveLock->count);
}

void ImageLoader::recursiveSpinUnLock()
{
        if ( --(fInitializerRecursiveLock->count) == 0 )
                fInitializerRecursiveLock = NULL;
}

void ImageLoader::InitializerTimingList::addTime(const char* name, uint64_t time)
{
        for (int i=0; i < count; ++i) {
                if ( strcmp(images[i].shortName, name) == 0 ) {
                        images[i].initTime += time;
                        return;
                }
        }
        images[count].initTime = time;
        images[count].shortName = name;
        ++count;
}

void ImageLoader::recursiveInitialization(const LinkContext& context, mach_port_t this_thread, const char* pathToInitialize,
                                                                                  InitializerTimingList& timingInfo, UninitedUpwards& uninitUps)
{
        recursive_lock lock_info(this_thread);
        recursiveSpinLock(lock_info);

        if ( fState < dyld_image_state_dependents_initialized-1 ) {
                uint8_t oldState = fState;
                // break cycles
                fState = dyld_image_state_dependents_initialized-1;
                try {
                        // initialize lower level libraries first
                        for(unsigned int i=0; i < libraryCount(); ++i) {
                                ImageLoader* dependentImage = libImage(i);
                                if ( dependentImage != NULL ) {
                                        // don't try to initialize stuff "above" me yet
                                        if ( libIsUpward(i) ) {
                                                uninitUps.imagesAndPaths[uninitUps.count] = { dependentImage, libPath(i) };
                                                uninitUps.count++;
                                        }
                                        else if ( dependentImage->fDepth >= fDepth ) {
                                                dependentImage->recursiveInitialization(context, this_thread, libPath(i), timingInfo, uninitUps);
                                        }
                }
                        }
                        
                        // record termination order
                        if ( this->needsTermination() )
                                context.terminationRecorder(this);

                        // let objc know we are about to initialize this image
                        uint64_t t1 = mach_absolute_time();
                        fState = dyld_image_state_dependents_initialized;
                        oldState = fState;
                        context.notifySingle(dyld_image_state_dependents_initialized, this, &timingInfo);
                        
                        // initialize this image
                        bool hasInitializers = this->doInitialization(context);

                        // let anyone know we finished initializing this image
                        fState = dyld_image_state_initialized;
                        oldState = fState;
                        context.notifySingle(dyld_image_state_initialized, this, NULL);
                        
                        if ( hasInitializers ) {
                                uint64_t t2 = mach_absolute_time();
                                timingInfo.addTime(this->getShortName(), t2-t1);
                        }
                }
                catch (const char* msg) {
                        // this image is not initialized
                        fState = oldState;
                        recursiveSpinUnLock();
                        throw;
                }
        }
        
        recursiveSpinUnLock();
}


static void printTime(const char* msg, uint64_t partTime, uint64_t totalTime)
{
        static uint64_t sUnitsPerSecond = 0;
        if ( sUnitsPerSecond == 0 ) {
                struct mach_timebase_info timeBaseInfo;
                if ( mach_timebase_info(&timeBaseInfo) != KERN_SUCCESS )
                        return;
                sUnitsPerSecond = 1000000000ULL * timeBaseInfo.denom / timeBaseInfo.numer;
        }
        if ( partTime < sUnitsPerSecond ) {
                uint32_t milliSecondsTimesHundred = (uint32_t)((partTime*100000)/sUnitsPerSecond);
                uint32_t milliSeconds = (uint32_t)(milliSecondsTimesHundred/100);
                uint32_t percentTimesTen = (uint32_t)((partTime*1000)/totalTime);
                uint32_t percent = percentTimesTen/10;
                if ( milliSeconds >= 100 )
                        dyld::log("%s: %u.%02u milliseconds (%u.%u%%)\n", msg, milliSeconds, milliSecondsTimesHundred-milliSeconds*100, percent, percentTimesTen-percent*10);
                else if ( milliSeconds >= 10 )
                        dyld::log("%s:  %u.%02u milliseconds (%u.%u%%)\n", msg, milliSeconds, milliSecondsTimesHundred-milliSeconds*100, percent, percentTimesTen-percent*10);
                else
                        dyld::log("%s:   %u.%02u milliseconds (%u.%u%%)\n", msg, milliSeconds, milliSecondsTimesHundred-milliSeconds*100, percent, percentTimesTen-percent*10);
        }
        else {
                uint32_t secondsTimeTen = (uint32_t)((partTime*10)/sUnitsPerSecond);
                uint32_t seconds = secondsTimeTen/10;
                uint32_t percentTimesTen = (uint32_t)((partTime*1000)/totalTime);
                uint32_t percent = percentTimesTen/10;
                dyld::log("%s: %u.%u seconds (%u.%u%%)\n", msg, seconds, secondsTimeTen-seconds*10, percent, percentTimesTen-percent*10);
        }
}

static char* commatize(uint64_t in, char* out)
{
        uint64_t div10 = in / 10;
        uint8_t delta = in - div10*10;
        char* s = &out[32];
        int digitCount = 1;
        *s = '\0';
        *(--s) = '0' + delta;
        in = div10;
        while ( in != 0 ) {
                if ( (digitCount % 3) == 0 )
                        *(--s) = ',';
                div10 = in / 10;
                delta = in - div10*10;
                *(--s) = '0' + delta;
                in = div10;
                ++digitCount;
        }
        return s;
}


void ImageLoader::printStatistics(unsigned int imageCount, const InitializerTimingList& timingInfo)
{
        uint64_t totalTime = fgTotalLoadLibrariesTime  + fgTotalRebaseTime + fgTotalBindTime + fgTotalWeakBindTime + fgTotalDOF + fgTotalInitTime;

        uint64_t totalDyldTime = totalTime - fgTotalDebuggerPausedTime - fgTotalRebindCacheTime;
        printTime("Total pre-main time", totalDyldTime, totalDyldTime);
        printTime("         dylib loading time", fgTotalLoadLibrariesTime-fgTotalDebuggerPausedTime, totalDyldTime);
        printTime("        rebase/binding time", fgTotalRebaseTime+fgTotalBindTime+fgTotalWeakBindTime-fgTotalRebindCacheTime, totalDyldTime);
        printTime("            ObjC setup time", fgTotalObjCSetupTime, totalDyldTime);
        printTime("           initializer time", fgTotalInitTime-fgTotalObjCSetupTime, totalDyldTime);
        dyld::log("           slowest intializers :\n");
        for (uintptr_t i=0; i < timingInfo.count; ++i) {
                uint64_t t = timingInfo.images[i].initTime;
                if ( t*50 < totalDyldTime )
                        continue;
                dyld::log("%30s ", timingInfo.images[i].shortName);
                if ( strncmp(timingInfo.images[i].shortName, "libSystem.", 10) == 0 )
                        t -= fgTotalObjCSetupTime;
                        printTime("", t, totalDyldTime);
        }
        dyld::log("\n");
}

void ImageLoader::printStatisticsDetails(unsigned int imageCount, const InitializerTimingList& timingInfo)
{
        uint64_t totalTime = fgTotalLoadLibrariesTime  + fgTotalRebaseTime + fgTotalBindTime + fgTotalWeakBindTime + fgTotalDOF + fgTotalInitTime;
        char commaNum1[40];
        char commaNum2[40];

        printTime("  total time", totalTime, totalTime);
        dyld::log("  total images loaded:  %d (%u from dyld shared cache)\n", imageCount, fgImagesUsedFromSharedCache);
        dyld::log("  total segments mapped: %u, into %llu pages\n", fgTotalSegmentsMapped, fgTotalBytesMapped/4096);
        printTime("  total images loading time", fgTotalLoadLibrariesTime, totalTime);
        printTime("  total load time in ObjC", fgTotalObjCSetupTime, totalTime);
        printTime("  total debugger pause time", fgTotalDebuggerPausedTime, totalTime);
        printTime("  total dtrace DOF registration time", fgTotalDOF, totalTime);
        dyld::log("  total rebase fixups:  %s\n", commatize(fgTotalRebaseFixups, commaNum1));
        printTime("  total rebase fixups time", fgTotalRebaseTime, totalTime);
        dyld::log("  total binding fixups: %s\n", commatize(fgTotalBindFixups, commaNum1));
        if ( fgTotalBindSymbolsResolved != 0 ) {
                uint32_t avgTimesTen = (fgTotalBindImageSearches * 10) / fgTotalBindSymbolsResolved;
                uint32_t avgInt = fgTotalBindImageSearches / fgTotalBindSymbolsResolved;
                uint32_t avgTenths = avgTimesTen - (avgInt*10);
                dyld::log("total binding symbol lookups: %s, average images searched per symbol: %u.%u\n", 
                                commatize(fgTotalBindSymbolsResolved, commaNum1), avgInt, avgTenths);
        }
        printTime("  total binding fixups time", fgTotalBindTime, totalTime);
        printTime("  total weak binding fixups time", fgTotalWeakBindTime, totalTime);
        printTime("  total redo shared cached bindings time", fgTotalRebindCacheTime, totalTime);
        dyld::log("  total bindings lazily fixed up: %s of %s\n", commatize(fgTotalLazyBindFixups, commaNum1), commatize(fgTotalPossibleLazyBindFixups, commaNum2));
        printTime("  total time in initializers and ObjC +load", fgTotalInitTime-fgTotalObjCSetupTime, totalTime);
        for (uintptr_t i=0; i < timingInfo.count; ++i) {
                uint64_t t = timingInfo.images[i].initTime;
                if ( t*1000 < totalTime )
                        continue;
                dyld::log("%42s ", timingInfo.images[i].shortName);
                if ( strncmp(timingInfo.images[i].shortName, "libSystem.", 10) == 0 )
                        t -= fgTotalObjCSetupTime;
                printTime("", t, totalTime);
        }
        
}


//
// copy path and add suffix to result
//
//  /path/foo.dylib             _debug   =>   /path/foo_debug.dylib     
//  foo.dylib                   _debug   =>   foo_debug.dylib
//  foo                         _debug   =>   foo_debug
//  /path/bar                   _debug   =>   /path/bar_debug  
//  /path/bar.A.dylib   _debug   =>   /path/bar.A_debug.dylib
//
void ImageLoader::addSuffix(const char* path, const char* suffix, char* result)
{
        strcpy(result, path);
        
        char* start = strrchr(result, '/');
        if ( start != NULL )
                start++;
        else
                start = result;
                
        char* dot = strrchr(start, '.');
        if ( dot != NULL ) {
                strcpy(dot, suffix);
                strcat(&dot[strlen(suffix)], &path[dot-result]);
        }
        else {
                strcat(result, suffix);
        }
}


//
// This function is the hotspot of symbol lookup.  It was pulled out of findExportedSymbol()
// to enable it to be re-written in assembler if needed.
//
const uint8_t* ImageLoader::trieWalk(const uint8_t* start, const uint8_t* end, const char* s)
{
        //dyld::log("trieWalk(%p, %p, %s)\n", start, end, s);
        ++fgSymbolTrieSearchs;
        const uint8_t* p = start;
        while ( p != NULL ) {
                uintptr_t terminalSize = *p++;
                if ( terminalSize > 127 ) {
                        // except for re-export-with-rename, all terminal sizes fit in one byte
                        --p;
                        terminalSize = read_uleb128(p, end);
                }
                if ( (*s == '\0') && (terminalSize != 0) ) {
                        //dyld::log("trieWalk(%p) returning %p\n", start, p);
                        return p;
                }
                const uint8_t* children = p + terminalSize;
                if ( children > end ) {
                        dyld::log("trieWalk() malformed trie node, terminalSize=0x%lx extends past end of trie\n", terminalSize);
                        return NULL;
                }
                //dyld::log("trieWalk(%p) sym=%s, terminalSize=%lu, children=%p\n", start, s, terminalSize, children);
                uint8_t childrenRemaining = *children++;
                p = children;
                uintptr_t nodeOffset = 0;
                for (; childrenRemaining > 0; --childrenRemaining) {
                        const char* ss = s;
                        //dyld::log("trieWalk(%p) child str=%s\n", start, (char*)p);
                        bool wrongEdge = false;
                        // scan whole edge to get to next edge
                        // if edge is longer than target symbol name, don't read past end of symbol name
                        char c = *p;
                        while ( c != '\0' ) {
                                if ( !wrongEdge ) {
                                        if ( c != *ss )
                                                wrongEdge = true;
                                        ++ss;
                                }
                                ++p;
                                c = *p;
                        }
                        if ( wrongEdge ) {
                                // advance to next child
                                ++p; // skip over zero terminator
                                // skip over uleb128 until last byte is found
                                while ( (*p & 0x80) != 0 )
                                        ++p;
                                ++p; // skip over last byte of uleb128
                                if ( p > end ) {
                                        dyld::log("trieWalk() malformed trie node, child node extends past end of trie\n");
                                        return NULL;
                                }
                        }
                        else {
                                // the symbol so far matches this edge (child)
                                // so advance to the child's node
                                ++p;
                                nodeOffset = read_uleb128(p, end);
                                if ( (nodeOffset == 0) || ( &start[nodeOffset] > end) ) {
                                        dyld::log("trieWalk() malformed trie child, nodeOffset=0x%lx out of range\n", nodeOffset);
                                        return NULL;
                                }
                                s = ss;
                                //dyld::log("trieWalk() found matching edge advancing to node 0x%lx\n", nodeOffset);
                                break;
                        }
                }
                if ( nodeOffset != 0 )
                        p = &start[nodeOffset];
                else
                        p = NULL;
        }
        //dyld::log("trieWalk(%p) return NULL\n", start);
        return NULL;
}


        
uintptr_t ImageLoader::read_uleb128(const uint8_t*& p, const uint8_t* end)
{
        uint64_t result = 0;
        int              bit = 0;
        do {
                if (p == end)
                        dyld::throwf("malformed uleb128");

                uint64_t slice = *p & 0x7f;

                if (bit > 63)
                        dyld::throwf("uleb128 too big for uint64, bit=%d, result=0x%0llX", bit, result);
                else {
                        result |= (slice << bit);
                        bit += 7;
                }
        } while (*p++ & 0x80);
        return (uintptr_t)result;
}


intptr_t ImageLoader::read_sleb128(const uint8_t*& p, const uint8_t* end)
{
        int64_t result = 0;
        int bit = 0;
        uint8_t byte;
        do {
                if (p == end)
                        throw "malformed sleb128";
                byte = *p++;
                result |= (((int64_t)(byte & 0x7f)) << bit);
                bit += 7;
        } while (byte & 0x80);
        // sign extend negative numbers
        if ( ((byte & 0x40) != 0) && (bit < 64) )
                result |= (~0ULL) << bit;
        return (intptr_t)result;
}

void ImageLoader::forEachReExportDependent( void (^callback)(const ImageLoader*, bool& stop)) const
{
        bool stop = false;
        for (unsigned int i=0; i < libraryCount(); ++i) {
                if ( libReExported(i) ) {
                        if ( ImageLoader* dependentImage = libImage(i) ) {
                                callback(dependentImage, stop);
                        }
                }
                if (stop)
                        break;
        }
}


VECTOR_NEVER_DESTRUCTED_IMPL(ImageLoader::InterposeTuple);
VECTOR_NEVER_DESTRUCTED_IMPL(ImagePair);