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--- dyld/dyld-44.2/src/ImageLoaderMachO.cpp
+++ dyld/dyld-45.1/src/ImageLoaderMachO.cpp
@@ -38,6 +38,10 @@
#include <mach-o/ppc/reloc.h>
#endif
+#ifndef S_ATTR_SELF_MODIFYING_CODE
+ #define S_ATTR_SELF_MODIFYING_CODE 0x04000000
+#endif
+
#include "ImageLoaderMachO.h"
#include "mach-o/dyld_gdb.h"
@@ -72,9 +76,11 @@
struct macho_routines_command : public routines_command {};
#endif
+ #define POINTER_RELOC GENERIC_RELOC_VANILLA
uint32_t ImageLoaderMachO::fgHintedBinaryTreeSearchs = 0;
uint32_t ImageLoaderMachO::fgUnhintedBinaryTreeSearchs = 0;
+uint32_t ImageLoaderMachO::fgCountOfImagesWithWeakExports = 0;
//#define LINKEDIT_USAGE_DEBUG 1
@@ -176,6 +182,12 @@
this->parseLoadCmds();
}
+ImageLoaderMachO::~ImageLoaderMachO()
+{
+ // keep count of images with weak exports
+ if ( this->hasCoalescedExports() )
+ --fgCountOfImagesWithWeakExports;
+}
@@ -188,7 +200,8 @@
const struct load_command* cmd = cmds;
for (unsigned long i = 0; i < cmd_count; ++i) {
if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
- fSegments.push_back(new SegmentMachO((struct macho_segment_command*)cmd, this, fileData));
+ if ( (((struct macho_segment_command*)cmd)->vmsize != 0) || !fIsSplitSeg )
+ fSegments.push_back(new SegmentMachO((struct macho_segment_command*)cmd, this, fileData));
}
cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
}
@@ -398,6 +411,8 @@
}
sNextAltLoadAddress += 0x00100000; // skip ahead 1MB and try again
if ( (sNextAltLoadAddress & 0xF0000000) == 0x90000000 )
+ sNextAltLoadAddress = 0xB0000000;
+ if ( (sNextAltLoadAddress & 0xF0000000) == 0xF0000000 )
throw "can't map split seg anywhere";
foundRoom = false;
break;
@@ -894,6 +909,10 @@
fMachOData = (uint8_t*)(seg->getActualLoadAddress());
}
}
+
+ // keep count of prebound images with weak exports
+ if ( this->hasCoalescedExports() )
+ ++fgCountOfImagesWithWeakExports;
// walk load commands (mapped in at start of __TEXT segment)
const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
@@ -1176,19 +1195,25 @@
return info;
}
+uintptr_t ImageLoaderMachO::getFirstWritableSegmentAddress()
+{
+ // in split segment libraries r_address is offset from first writable segment
+ for (std::vector<class Segment*>::iterator it=fSegments.begin(); it != fSegments.end(); ++it) {
+ if ( (*it)->writeable() ) {
+ return (*it)->getActualLoadAddress();
+ }
+ }
+ throw "no writable segment";
+}
uintptr_t ImageLoaderMachO::getRelocBase()
{
+#if __ppc__ || __i386__
if ( fIsSplitSeg ) {
// in split segment libraries r_address is offset from first writable segment
- const unsigned int segmentCount = fSegments.size();
- for(unsigned int i=0; i < segmentCount; ++i){
- Segment* seg = fSegments[i];
- if ( seg->writeable() ) {
- return seg->getActualLoadAddress();
- }
- }
- }
+ return getFirstWritableSegmentAddress();
+ }
+#endif
// in non-split segment libraries r_address is offset from first segment
return fSegments[0]->getActualLoadAddress();
@@ -1265,6 +1290,7 @@
const relocation_info* const relocsStart = (struct relocation_info*)(&fLinkEditBase[fDynamicInfo->locreloff]);
const relocation_info* const relocsEnd = &relocsStart[fDynamicInfo->nlocrel];
for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
+ #if __ppc__ || __ppc64__ || __i386__
if ( (reloc->r_address & R_SCATTERED) == 0 ) {
if ( reloc->r_symbolnum == R_ABS ) {
// ignore absolute relocations
@@ -1328,6 +1354,7 @@
throw "bad local scattered relocation length";
}
}
+ #endif
}
// if there were __TEXT fixups, restore write protection
@@ -1497,6 +1524,7 @@
}
}
+
return NULL;
}
@@ -1769,6 +1797,34 @@
}
}
+// returns if 'addr' is within the address range of section 'sectionIndex'
+// fSlide is not used. 'addr' is assumed to be a prebound address in this image
+bool ImageLoaderMachO::isAddrInSection(uintptr_t addr, uint8_t sectionIndex)
+{
+ uint8_t currentSectionIndex = 1;
+ const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
+ const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
+ const struct load_command* cmd = cmds;
+ for (unsigned long i = 0; i < cmd_count; ++i) {
+ if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
+ const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
+ if ( (currentSectionIndex <= sectionIndex) && (sectionIndex < currentSectionIndex+seg->nsects) ) {
+ // 'sectionIndex' is in this segment, get section info
+ const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
+ const struct macho_section* const section = §ionsStart[sectionIndex-currentSectionIndex];
+ return ( (section->addr <= addr) && (addr < section->addr+section->size) );
+ }
+ else {
+ // 'sectionIndex' not in this segment, skip to next segment
+ currentSectionIndex += seg->nsects;
+ }
+ }
+ cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
+ }
+
+ return false;
+}
+
void ImageLoaderMachO::doBindExternalRelocations(const LinkContext& context, bool onlyCoalescedSymbols)
{
const uintptr_t relocBase = this->getRelocBase();
@@ -1790,7 +1846,7 @@
for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
if (reloc->r_length == RELOC_SIZE) {
switch(reloc->r_type) {
- case GENERIC_RELOC_VANILLA:
+ case POINTER_RELOC:
{
const struct macho_nlist* undefinedSymbol = &fSymbolTable[reloc->r_symbolnum];
// if only processing coalesced symbols and this one does not require coalesceing, skip to next
@@ -1805,10 +1861,24 @@
#endif
if ( prebound ) {
// we are doing relocations, so prebinding was not usable
- // in a prebound executable, the n_value field is set to the address where the symbol was found when prebound
+ // in a prebound executable, the n_value field of an undefined symbol is set to the address where the symbol was found when prebound
// so, subtracting that gives the initial displacement which we need to add to the newly found symbol address
- // if mach-o relocation structs had an "addend" field this would not be necessary.
- value -= undefinedSymbol->n_value;
+ // if mach-o relocation structs had an "addend" field this complication would not be necessary.
+ if ( ((undefinedSymbol->n_type & N_TYPE) == N_SECT) && ((undefinedSymbol->n_desc & N_WEAK_DEF) != 0) ) {
+ // weak symbols need special casing, since *location may have been prebound to a definition in another image.
+ // If *location is currently prebound to somewhere in the same section as the weak definition, we assume
+ // that we can subtract off the weak symbol address to get the addend.
+ // If prebound elsewhere, we've lost the addend and have to assume it is zero.
+ // The prebinding to elsewhere only happens with 10.4+ update_prebinding which only operates on a small set of Apple dylibs
+ if ( (value == undefinedSymbol->n_value) || this->isAddrInSection(value, undefinedSymbol->n_sect) )
+ value -= undefinedSymbol->n_value;
+ else
+ value = 0;
+ }
+ else {
+ // is undefined or non-weak symbol, so do subtraction to get addend
+ value -= undefinedSymbol->n_value;
+ }
}
// if undefinedSymbol is same as last time, then symbolAddr and image will resolve to the same too
if ( undefinedSymbol != lastUndefinedSymbol ) {
@@ -1837,10 +1907,14 @@
*location = value - ((uintptr_t)location + 4);
}
else {
- *location = value;
+ // don't dirty page if prebound value was correct
+ if ( !prebound || (*location != value) )
+ *location = value;
}
#else
- *location = value;
+ // don't dirty page if prebound value was correct
+ if ( !prebound || (*location != value) )
+ *location = value;
#endif
}
break;
@@ -1878,6 +1952,40 @@
{
Segment* seg = fSegments[0];
return (const void*)seg->getActualLoadAddress();
+}
+
+uintptr_t ImageLoaderMachO::bindIndirectSymbol(uintptr_t* ptrToBind, const struct macho_section* sect, const char* symbolName, uintptr_t targetAddr, ImageLoader* targetImage, const LinkContext& context)
+{
+ if ( context.verboseBind ) {
+ const char* path = NULL;
+ if ( targetImage != NULL )
+ path = targetImage->getShortName();
+ fprintf(stderr, "dyld: bind: %s:%s$%s = %s:%s, *0x%08lx = 0x%08lx\n",
+ this->getShortName(), symbolName, (((sect->flags & SECTION_TYPE)==S_NON_LAZY_SYMBOL_POINTERS) ? "non_lazy_ptr" : "lazy_ptr"),
+ path, symbolName, (uintptr_t)ptrToBind, targetAddr);
+ }
+ if ( context.bindingHandler != NULL ) {
+ const char* path = NULL;
+ if ( targetImage != NULL )
+ path = targetImage->getShortName();
+ targetAddr = (uintptr_t)context.bindingHandler(path, symbolName, (void *)targetAddr);
+ }
+#if __i386__
+ // i386 has special self-modifying stubs that change from "CALL rel32" to "JMP rel32"
+ if ( ((sect->flags & SECTION_TYPE) == S_SYMBOL_STUBS) && ((sect->flags & S_ATTR_SELF_MODIFYING_CODE) != 0) && (sect->reserved2 == 5) ) {
+ uint8_t* const jmpTableEntryToPatch = (uint8_t*)ptrToBind;
+ uint32_t rel32 = targetAddr - (((uint32_t)ptrToBind)+5);
+ //fprintf(stderr, "rewriting stub at %p\n", jmpTableEntryToPatch);
+ jmpTableEntryToPatch[0] = 0xE9; // JMP rel32
+ jmpTableEntryToPatch[1] = rel32 & 0xFF;
+ jmpTableEntryToPatch[2] = (rel32 >> 8) & 0xFF;
+ jmpTableEntryToPatch[3] = (rel32 >> 16) & 0xFF;
+ jmpTableEntryToPatch[4] = (rel32 >> 24) & 0xFF;
+ }
+ else
+#endif
+ *ptrToBind = targetAddr;
+ return targetAddr;
}
@@ -1898,38 +2006,39 @@
const struct macho_section* const sectionsEnd = §ionsStart[seg->nsects];
for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
const uint8_t type = sect->flags & SECTION_TYPE;
+ uint32_t symbolIndex = INDIRECT_SYMBOL_LOCAL;
if ( type == S_LAZY_SYMBOL_POINTERS ) {
const uint32_t pointerCount = sect->size / sizeof(uintptr_t);
uintptr_t* const symbolPointers = (uintptr_t*)(sect->addr + fSlide);
if ( (lazyPointer >= symbolPointers) && (lazyPointer < &symbolPointers[pointerCount]) ) {
const uint32_t indirectTableOffset = sect->reserved1;
const uint32_t lazyIndex = lazyPointer - symbolPointers;
- uint32_t symbolIndex = indirectTable[indirectTableOffset + lazyIndex];
- if ( symbolIndex != INDIRECT_SYMBOL_ABS && symbolIndex != INDIRECT_SYMBOL_LOCAL ) {
- ImageLoader *image = NULL;
- const char *path = NULL;
- uintptr_t symbolAddr = this->resolveUndefined(context, &fSymbolTable[symbolIndex], twoLevel, &image);
- if ( context.verboseBind ) {
- if(NULL == path && NULL != image) {
- path = image->getShortName();
- }
- fprintf(stderr, "dyld: bind: %s:%s$%s = %s:%s, *0x%08lx = 0x%08lx\n",
- this->getShortName(), &fStrings[fSymbolTable[symbolIndex].n_un.n_strx], "lazy_ptr",
- path, &fStrings[fSymbolTable[symbolIndex].n_un.n_strx], (uintptr_t)&symbolPointers[lazyIndex], symbolAddr);
- }
- if ( NULL != context.bindingHandler ) {
- if(NULL == path && NULL != image) {
- path = image->getPath();
- }
- symbolAddr = (uintptr_t)context.bindingHandler(path, &fStrings[fSymbolTable[symbolIndex].n_un.n_strx], (void *)symbolAddr);
- }
- symbolPointers[lazyIndex] = symbolAddr;
- // update stats
- fgTotalLazyBindFixups++;
- return symbolPointers[lazyIndex];
- }
+ symbolIndex = indirectTable[indirectTableOffset + lazyIndex];
}
}
+ #if __i386__
+ else if ( (type == S_SYMBOL_STUBS) && (sect->flags & S_ATTR_SELF_MODIFYING_CODE) && (sect->reserved2 == 5) ) {
+ // 5 bytes stubs on i386 are new "fast stubs"
+ uint8_t* const jmpTableBase = (uint8_t*)(sect->addr + fSlide);
+ uint8_t* const jmpTableEnd = jmpTableBase + sect->size;
+ // initial CALL instruction in jump table leaves pointer to next entry, so back up
+ uint8_t* const jmpTableEntryToPatch = ((uint8_t*)lazyPointer) - 5;
+ lazyPointer = (uintptr_t*)jmpTableEntryToPatch;
+ if ( (jmpTableEntryToPatch >= jmpTableBase) && (jmpTableEntryToPatch < jmpTableEnd) ) {
+ const uint32_t indirectTableOffset = sect->reserved1;
+ const uint32_t entryIndex = (jmpTableEntryToPatch - jmpTableBase)/5;
+ symbolIndex = indirectTable[indirectTableOffset + entryIndex];
+ }
+ }
+ #endif
+ if ( symbolIndex != INDIRECT_SYMBOL_ABS && symbolIndex != INDIRECT_SYMBOL_LOCAL ) {
+ const char* symbolName = &fStrings[fSymbolTable[symbolIndex].n_un.n_strx];
+ ImageLoader* image = NULL;
+ uintptr_t symbolAddr = this->resolveUndefined(context, &fSymbolTable[symbolIndex], twoLevel, &image);
+ symbolAddr = this->bindIndirectSymbol(lazyPointer, sect, symbolName, symbolAddr, image, context);
+ ++fgTotalLazyBindFixups;
+ return symbolAddr;
+ }
}
}
break;
@@ -1938,6 +2047,7 @@
}
throw "lazy pointer not found";
}
+
@@ -1958,26 +2068,37 @@
const struct macho_section* const sectionsEnd = §ionsStart[seg->nsects];
for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
const uint8_t type = sect->flags & SECTION_TYPE;
- const uint32_t pointerCount = sect->size / sizeof(uintptr_t);
+ uint32_t elementSize = sizeof(uintptr_t);
+ uint32_t elementCount = sect->size / elementSize;
if ( type == S_NON_LAZY_SYMBOL_POINTERS ) {
if ( (bindness == kLazyOnly) || (bindness == kLazyOnlyNoDependents) )
continue;
}
else if ( type == S_LAZY_SYMBOL_POINTERS ) {
// process each symbol pointer in this section
- fgTotalPossibleLazyBindFixups += pointerCount;
+ fgTotalPossibleLazyBindFixups += elementCount;
if ( bindness == kNonLazyOnly )
continue;
}
+ #if __i386__
+ else if ( (type == S_SYMBOL_STUBS) && (sect->flags & S_ATTR_SELF_MODIFYING_CODE) && (sect->reserved2 == 5) ) {
+ // process each jmp entry in this section
+ elementCount = sect->size / 5;
+ elementSize = 5;
+ fgTotalPossibleLazyBindFixups += elementCount;
+ if ( bindness == kNonLazyOnly )
+ continue;
+ }
+ #endif
else {
continue;
}
const uint32_t indirectTableOffset = sect->reserved1;
- uintptr_t* const symbolPointers = (uintptr_t*)(sect->addr + fSlide);
- for (uint32_t j=0; j < pointerCount; ++j) {
+ uint8_t* ptrToBind = (uint8_t*)(sect->addr + fSlide);
+ for (uint32_t j=0; j < elementCount; ++j, ptrToBind += elementSize) {
uint32_t symbolIndex = indirectTable[indirectTableOffset + j];
if ( symbolIndex == INDIRECT_SYMBOL_LOCAL) {
- symbolPointers[j] += this->fSlide;
+ *((uintptr_t*)ptrToBind) += this->fSlide;
}
else if ( symbolIndex == INDIRECT_SYMBOL_ABS) {
// do nothing since already has absolute address
@@ -2015,27 +2136,13 @@
continue;
uintptr_t symbolAddr;
symbolAddr = resolveUndefined(context, sym, twoLevel, &image);
- if ( context.verboseBind ) {
- const char *path = NULL;
- if(NULL != image) {
- path = image->getShortName();
- }
- const char *typeName;
- if ( type == S_LAZY_SYMBOL_POINTERS ) {
- typeName = "lazy_ptr";
- }
- else {
- typeName = "non_lazy_ptr";
- }
- fprintf(stderr, "dyld: bind: %s:%s$%s = %s:%s, *0x%08lx = 0x%08lx\n",
- this->getShortName(), &fStrings[sym->n_un.n_strx], typeName,
- path, &fStrings[sym->n_un.n_strx], (uintptr_t)&symbolPointers[j], symbolAddr);
- }
- symbolPointers[j] = symbolAddr;
+
+ // update pointer
+ symbolAddr = this->bindIndirectSymbol((uintptr_t*)ptrToBind, sect, &fStrings[sym->n_un.n_strx], symbolAddr, image, context);
}
}
// update stats
- fgTotalBindFixups += pointerCount;
+ fgTotalBindFixups += elementCount;
}
}
break;
@@ -2074,9 +2181,10 @@
// These are defined in dyldStartup.s
extern "C" void stub_binding_helper();
extern "C" bool dyld_func_lookup(const char* name, uintptr_t* address);
-
-
-void ImageLoaderMachO::setupLazyPointerHandler()
+extern "C" void fast_stub_binding_helper_interface();
+
+
+void ImageLoaderMachO::setupLazyPointerHandler(const LinkContext& context)
{
if ( fDATAdyld != NULL ) {
struct DATAdyld* dd = (struct DATAdyld*)(fDATAdyld->addr + fSlide);
@@ -2095,6 +2203,42 @@
// save = dd->stubBindHelper;
#endif
}
+#if __i386__
+ if ( ! this->usablePrebinding(context) || !this->usesTwoLevelNameSpace() ) {
+ // reset all "fast" stubs
+ const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
+ const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
+ const struct load_command* cmd = cmds;
+ for (uint32_t i = 0; i < cmd_count; ++i) {
+ switch (cmd->cmd) {
+ case LC_SEGMENT_COMMAND:
+ {
+ const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
+ const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
+ const struct macho_section* const sectionsEnd = §ionsStart[seg->nsects];
+ for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
+ const uint8_t type = sect->flags & SECTION_TYPE;
+ if ( (type == S_SYMBOL_STUBS) && (sect->flags & S_ATTR_SELF_MODIFYING_CODE) && (sect->reserved2 == 5) ) {
+ // reset each jmp entry in this section
+ uint8_t* start = (uint8_t*)(sect->addr + this->fSlide);
+ uint8_t* end = start + sect->size;
+ uintptr_t dyldHandler = (uintptr_t)&fast_stub_binding_helper_interface;
+ for (uint8_t* entry = start; entry < end; entry += 5) {
+ uint32_t rel32 = dyldHandler - (((uint32_t)entry)+5);
+ entry[0] = 0xE8; // CALL rel32
+ entry[1] = rel32 & 0xFF;
+ entry[2] = (rel32 >> 8) & 0xFF;
+ entry[3] = (rel32 >> 16) & 0xFF;
+ entry[4] = (rel32 >> 24) & 0xFF;
+ }
+ }
+ }
+ }
+ }
+ cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
+ }
+ }
+#endif
}
bool ImageLoaderMachO::usablePrebinding(const LinkContext& context) const
@@ -2121,13 +2265,13 @@
void ImageLoaderMachO::doBind(const LinkContext& context, BindingLaziness bindness)
{
// set dyld entry points in image
- this->setupLazyPointerHandler();
+ this->setupLazyPointerHandler(context);
// if prebound and loaded at prebound address, and all libraries are same as when this was prebound, then no need to bind
// note: flat-namespace binaries need to be imports rebound (even if correctly prebound)
if ( this->usablePrebinding(context) && this->usesTwoLevelNameSpace() ) {
- // if image has coalesced symbols, then these need to be rebound
- if ( this->needsCoalescing() ) {
+ // if image has coalesced symbols, then these need to be rebound, unless this is the only image with weak symbols
+ if ( this->needsCoalescing() && (fgCountOfImagesWithWeakExports > 1) ) {
this->doBindExternalRelocations(context, true);
this->doBindIndirectSymbolPointers(context, kLazyAndNonLazy, true);
}
@@ -2232,6 +2376,7 @@
ImageLoader::printStatistics(imageCount);
fprintf(stderr, "total hinted binary tree searches: %d\n", fgHintedBinaryTreeSearchs);
fprintf(stderr, "total unhinted binary tree searches: %d\n", fgUnhintedBinaryTreeSearchs);
+ fprintf(stderr, "total images with weak exports: %d\n", fgCountOfImagesWithWeakExports);
#if LINKEDIT_USAGE_DEBUG
fprintf(stderr, "linkedit pages accessed (%lu):\n", sLinkEditPageBuckets.size());