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

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2004-2006 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#define __STDC_LIMIT_MACROS
#include <stdint.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 <libkern/OSAtomic.h>

#include "ImageLoader.h"


uint32_t                                                                ImageLoader::fgImagesUsedFromSharedCache = 0;
uint32_t                                                                ImageLoader::fgImagesWithUsedPrebinding = 0;
uint32_t                                                                ImageLoader::fgImagesRequiringNoFixups = 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::fgTotalBytesPreFetched = 0;
uint64_t                                                                ImageLoader::fgTotalLoadLibrariesTime;
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;
uintptr_t                                                               ImageLoader::fgNextPIEDylibAddress = 0;



ImageLoader::ImageLoader(const char* path, unsigned int libCount)
        : fPath(path), fDevice(0), fInode(0), fLastModified(0), 
        fPathHash(0), fDlopenReferenceCount(0), fStaticReferenceCount(0),
        fDynamicReferenceCount(0), fDynamicReferences(NULL), fInitializerRecursiveLock(NULL), 
        fDepth(0), fLoadOrder(0), fState(0), fLibraryCount(libCount), 
        fAllLibraryChecksumsAndLoadAddressesMatch(false), fLeaveMapped(false), fNeverUnload(false),
        fHideSymbols(false), fMatchByInstallName(false),
        fRegisteredDOF(false), fAllLazyPointersBound(false), fBeingRemoved(false), fAddFuncNotified(false),
        fPathOwnedByImage(false), fWeakSymbolsBound(false)
{
        if ( fPath != NULL )
                fPathHash = hash(fPath);
}


void ImageLoader::deleteImage(ImageLoader* image)
{
        // this cannot be done in destructor because libImage() is implemented
        // in a subclass
        for(unsigned int i=0; i < image->libraryCount(); ++i) {
                ImageLoader* lib = image->libImage(i);
                if ( lib != NULL )
                        lib->fStaticReferenceCount--;
        }
        delete image;
}


ImageLoader::~ImageLoader()
{
        if ( fPathOwnedByImage && (fPath != NULL) ) 
                delete [] fPath;
        if ( fDynamicReferences != NULL ) {
                for (std::set<const ImageLoader*>::iterator it = fDynamicReferences->begin(); it != fDynamicReferences->end(); ++it ) {
                        const_cast<ImageLoader*>(*it)->fDynamicReferenceCount--;
                }
                delete fDynamicReferences;
        }
}

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);  // note: can throw exception
}

void ImageLoader::addDynamicReference(const ImageLoader* target)
{
        if ( fDynamicReferences == NULL )
                fDynamicReferences = new std::set<const ImageLoader*>();
        if ( fDynamicReferences->count(target) == 0 ) { 
                fDynamicReferences->insert(target);
                const_cast<ImageLoader*>(target)->fDynamicReferenceCount++;
        }
        //dyld::log("dyld: addDynamicReference() from %s to %s, fDynamicReferences->size()=%lu\n", this->getPath(), target->getPath(), fDynamicReferences->size());
}

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);
}

void ImageLoader::setPathUnowned(const char* path)
{
        if ( fPathOwnedByImage && (fPath != NULL) ) {
                delete [] fPath;
        }
        fPath = path;
        fPathOwnedByImage = false;  
        fPathHash = hash(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::getShortName() const
{
        // try to return leaf name
        if ( fPath != NULL ) {
                const char* s = strrchr(fPath, '/');
                if ( s != NULL ) 
                        return &s[1];
        }
        return 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
{
        if ( ! this->isLinked() )
                return false;
        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 ( (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;
        }
}


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;
}


// 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, 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) ) {
                        const ImageLoader::Symbol* sym = dependentImage->findExportedSymbol(name, false, 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; 
                        const ImageLoader::Symbol* 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();
        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();
        const ImageLoader* dontSearchImages[imageCount];
        const ImageLoader** cur = &dontSearchImages[0];
        return this->findExportedSymbolInDependentImagesExcept(name, &dontSearchImages[0], cur, &dontSearchImages[imageCount], foundIn);
}


void ImageLoader::link(const LinkContext& context, bool forceLazysBound, bool preflightOnly, const RPathChain& loaderRPaths)
{
        //dyld::log("ImageLoader::link(%s) refCount=%d, neverUnload=%d\n", this->getPath(), fStaticReferenceCount, fNeverUnload);
        
        uint64_t t0 = mach_absolute_time();
        this->recursiveLoadLibraries(context, preflightOnly, loaderRPaths);
        context.notifyBatch(dyld_image_state_dependents_mapped);
        
        // we only do the loading step for preflights
        if ( preflightOnly )
                return;
                
        uint64_t t1 = mach_absolute_time();
        context.clearAllDepths();
        this->recursiveUpdateDepth(context.imageCount());

        uint64_t t2 = mach_absolute_time();
        this->recursiveRebase(context);
        context.notifyBatch(dyld_image_state_rebased);
        
        uint64_t t3 = mach_absolute_time();
        this->recursiveBind(context, forceLazysBound);

        uint64_t t4 = mach_absolute_time();
        this->weakBind(context);
        context.notifyBatch(dyld_image_state_bound);

        uint64_t t5 = mach_absolute_time();     
        std::vector<DOFInfo> dofs;
        this->recursiveGetDOFSections(context, dofs);
        context.registerDOFs(dofs);
        uint64_t t6 = mach_absolute_time();     

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


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


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

void ImageLoader::runInitializers(const LinkContext& context)
{
        uint64_t t1 = mach_absolute_time();
        mach_port_t this_thread = mach_thread_self();
        this->recursiveInitialization(context, this_thread);
        context.notifyBatch(dyld_image_state_initialized);
        mach_port_deallocate(mach_task_self(), this_thread);
        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
                this->doBindJustLazies(context);
        }
}


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


unsigned int ImageLoader::recursiveUpdateDepth(unsigned int maxDepth)
{
        // 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 ) {
                                unsigned int d = dependentImage->recursiveUpdateDepth(maxDepth);
                                if ( d < minDependentDepth )
                                        minDependentDepth = d;
                        }
                }
        
                // make me less deep then all my dependents
                fDepth = minDependentDepth - 1;
        }
        
        return fDepth;
}


void ImageLoader::recursiveLoadLibraries(const LinkContext& context, bool preflightOnly, const RPathChain& loaderRPaths)
{
        if ( fState < dyld_image_state_dependents_mapped ) {
                // break cycles
                fState = dyld_image_state_dependents_mapped;
                
                // get list of libraries this image needs
                //dyld::log("ImageLoader::recursiveLoadLibraries() %ld = %d*%ld\n", fLibrariesCount*sizeof(DependentLibrary), fLibrariesCount, sizeof(DependentLibrary));
                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;
                        bool depLibReRequired = false;
                        bool depLibCheckSumsMatch = false;
                        DependentLibraryInfo& requiredLibInfo = libraryInfos[i];
#if DYLD_SHARED_CACHE_SUPPORT
                        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);
                                continue;
                        }
#endif
                        try {
                                dependentLib = context.loadLibrary(requiredLibInfo.name, true, this->getPath(), &thisRPaths);
                                if ( dependentLib == this ) {
                                        // found circular reference, perhaps DYLD_LIBARY_PATH is causing this rdar://problem/3684168 
                                        dependentLib = context.loadLibrary(requiredLibInfo.name, false, NULL, NULL);
                                        if ( dependentLib != this )
                                                dyld::warn("DYLD_ setting caused circular dependency in %s\n", this->getPath());
                                }
                                if ( fNeverUnload )
                                        dependentLib->setNeverUnload();
                                dependentLib->fStaticReferenceCount += 1;
                                LibraryInfo actualInfo = dependentLib->doGetLibraryInfo();
                                depLibReRequired = requiredLibInfo.required;
                                depLibCheckSumsMatch = ( actualInfo.checksum == requiredLibInfo.info.checksum );
                                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
                                if ( actualInfo.minVersion < requiredLibInfo.info.minVersion ) {
                                        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 or slid
                                if ( !depLibCheckSumsMatch || (dependentLib->getSlide() != 0) )
                                        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;
                                        dyld::throwf("Library not loaded: %s\n  Referenced from: %s\n  Reason: %s", requiredLibInfo.name, this->getPath(), msg);
                                }
                                // 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);
                }
                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);
                        }
                }
                
                // 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::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);
                }
                catch (const char* msg) {
                        // this image is not rebased
                        fState = dyld_image_state_dependents_mapped;
                        throw;
                }
        }
}




void ImageLoader::recursiveBind(const LinkContext& context, bool forceLazysBound)
{
        // 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 )
                                        dependentImage->recursiveBind(context, forceLazysBound);
                        }
                        // bind this image
                        this->doBind(context, forceLazysBound); 
                        // mark if lazys are also bound
                        if ( forceLazysBound || this->usablePrebinding(context) )
                                fAllLazyPointersBound = true;
                                
                        context.notifySingle(dyld_image_state_bound, this);
                }
                catch (const char* msg) {
                        // restore state
                        fState = dyld_image_state_rebased;
                        throw;
                }
        }
}

void ImageLoader::weakBind(const LinkContext& context)
{
        if ( context.verboseWeakBind )
                dyld::log("dyld: weak bind start:\n");
        // get set of ImageLoaders that participate in coalecsing
        ImageLoader* imagesNeedingCoalescing[fgImagesRequiringCoalescing];
        int count = context.getCoalescedImages(imagesNeedingCoalescing);
        
        // count how many have not already had weakbinding done
        int countNotYetWeakBound = 0;
        int countOfImagesWithWeakDefinitions = 0;
        for(int i=0; i < count; ++i) {
                if ( ! imagesNeedingCoalescing[i]->fWeakSymbolsBound )
                        ++countNotYetWeakBound;
                if ( imagesNeedingCoalescing[i]->hasCoalescedExports() )
                        ++countOfImagesWithWeakDefinitions;
        }

        // don't need to do any coalescing if only one image has overrides, or all have already been done
        if ( (countOfImagesWithWeakDefinitions > 1) && (countNotYetWeakBound > 0) ) {
                // 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);
                        sortedIts[i] = &iterators[i];
                        if ( context.verboseWeakBind )
                                dyld::log("dyld: weak bind load order %d/%d for %s\n", i, count, imagesNeedingCoalescing[i]->getPath());
                }
                
                // 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;
                                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->getPath());
                                                if ( iterators[i].weakSymbol ) {
                                                        if ( targetAddr == 0 ) {
                                                                targetAddr = iterators[i].image->getAddressCoalIterator(iterators[i], context);
                                                                if ( targetAddr != 0 )
                                                                        targetImage = iterators[i].image;
                                                        }
                                                }
                                                else {
                                                        targetAddr = iterators[i].image->getAddressCoalIterator(iterators[i], context);
                                                        if ( targetAddr != 0 ) {
                                                                targetImage = iterators[i].image;
                                                                // strong implementation found, stop searching
                                                                break;
                                                        }
                                                }
                                        }
                                }
                                if ( context.verboseWeakBind )
                                        dyld::log("dyld: weak binding all uses of %s to copy from %s\n", nameToCoalesce, targetImage->getShortName());
                                
                                // tell each to bind to this symbol (unless already bound)
                                if ( targetAddr != 0 ) {
                                        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->getShortName(), targetAddr, targetImage->getShortName());
                                                        if ( ! iterators[i].image->fWeakSymbolsBound )
                                                                iterators[i].image->updateUsesCoalIterator(iterators[i], targetAddr, targetImage, context);
                                                        iterators[i].symbolMatches = false; 
                                                }
                                        }
                                }
                                
                        }
                }
                
                // mark all as having all weak symbols bound
                for(int i=0; i < count; ++i) {
                        imagesNeedingCoalescing[i]->fWeakSymbolsBound = true;
                }
        }
        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::recursiveSpinLock(recursive_lock& rlock)
{
        // try to set image's ivar fInitializerRecursiveLock to point to this lock_info
        // keep trying until success (spin)
        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;
        }
        ++(fInitializerRecursiveLock->count); 
}

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


void ImageLoader::recursiveInitialization(const LinkContext& context, mach_port_t this_thread)
{
        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
                                if ( (dependentImage != NULL) && (dependentImage->fDepth >= fDepth) )
                                        dependentImage->recursiveInitialization(context, this_thread);
                        }
                        
                        // record termination order
                        if ( this->needsTermination() )
                                context.terminationRecorder(this);
                        
                        // let objc know we are about to initalize this image
                        fState = dyld_image_state_dependents_initialized;
                        oldState = fState;
                        context.notifySingle(dyld_image_state_dependents_initialized, this);

                        // initialize this image
                        this->doInitialization(context);

                        // let anyone know we finished initalizing this image
                        fState = dyld_image_state_initialized;
                        oldState = fState;
                        context.notifySingle(dyld_image_state_initialized, this);
                }
                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 ) {
                        sUnitsPerSecond = 1000000000ULL * timeBaseInfo.denom / timeBaseInfo.numer;
                }
        }
        if ( partTime < sUnitsPerSecond ) {
                uint32_t milliSecondsTimesHundred = (partTime*100000)/sUnitsPerSecond;
                uint32_t milliSeconds = milliSecondsTimesHundred/100;
                uint32_t percentTimesTen = (partTime*1000)/totalTime;
                uint32_t percent = percentTimesTen/10;
                dyld::log("%s: %u.%02u milliseconds (%u.%u%%)\n", msg, milliSeconds, milliSecondsTimesHundred-milliSeconds*100, percent, percentTimesTen-percent*10);
        }
        else {
                uint32_t secondsTimeTen = (partTime*10)/sUnitsPerSecond;
                uint32_t seconds = secondsTimeTen/10;
                uint32_t percentTimesTen = (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)
{
        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, %u needed no fixups)\n", imageCount, fgImagesUsedFromSharedCache, fgImagesRequiringNoFixups);
        dyld::log("total segments mapped: %u, into %llu pages with %llu pages pre-fetched\n", fgTotalSegmentsMapped, fgTotalBytesMapped/4096, fgTotalBytesPreFetched/4096);
        printTime("total images loading time", fgTotalLoadLibrariesTime, 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);
        dyld::log("total bindings lazily fixed up: %s of %s\n", commatize(fgTotalLazyBindFixups, commaNum1), commatize(fgTotalPossibleLazyBindFixups, commaNum2));
        printTime("total initializer time", fgTotalInitTime, 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);
        }
}