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llvm-project/lld/lib/ReaderWriter/MachO/WriterMachO.cpp

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//===- lib/ReaderWriter/MachO/WriterMachO.cpp -----------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "lld/ReaderWriter/Writer.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/system_error.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Triple.h"
#include "lld/Core/DefinedAtom.h"
#include "lld/Core/File.h"
#include "lld/Core/InputFiles.h"
#include "lld/Core/Reference.h"
#include "lld/Core/SharedLibraryAtom.h"
#include "lld/ReaderWriter/MachOTargetInfo.h"
#include <vector>
#include <map>
#include <string.h>
#include "MachOFormat.hpp"
#include "ReferenceKinds.h"
#include "ExecutableAtoms.hpp"
namespace lld {
namespace mach_o {
class LoadCommandPaddingChunk;
class SymbolStringsChunk;
class MachOWriter;
//
// A mach-o file consists of some meta data (header and load commands),
// then atom content (e.g. function instructions), then more meta data
// (symbol table, etc). Before you can write a mach-o file, you need to
// compute what will be the file offsets and "addresses" of various things
// in the file.
//
// The design here is to break up what will be the mach-o file into chunks.
// Each Chunk has an object to manage its size and content. There is a
// chunk for the mach_header, one for the load commands, and one for each
// part of the LINKEDIT segment. There is also one chunk for each traditional
// mach-o section. The MachOWriter manages the list of chunks. And
// asks each to determine its size in the correct order. Many chunks
// cannot be sized until other chunks are sized (e.g. the dyld info
// in the LINKEDIT cannot be sized until all atoms have been assigned
// addresses).
//
// Once all chunks have a size, the MachOWriter iterates through them and
// asks each to write out their content.
//
//
// A Chunk is an abstrace contiguous range of a generated
// mach-o executable file.
//
class Chunk {
public:
virtual ~Chunk() { }
virtual StringRef segmentName() const = 0;
virtual bool occupiesNoDiskSpace();
virtual void write(uint8_t *fileBuffer) = 0;
void assignFileOffset(uint64_t &curOff, uint64_t &curAddr);
virtual const char* info() = 0;
uint64_t size() const;
uint64_t address() const;
uint64_t fileOffset() const;
uint64_t align2() const;
static uint64_t alignTo(uint64_t value, uint8_t align2);
protected:
Chunk();
uint64_t _size;
uint64_t _address;
uint64_t _fileOffset;
uint32_t _align2;
};
//
// A SectionChunk represents a set of Atoms assigned to a specific
// mach-o section (which is a subrange of a mach-o segment).
// For example, there is one SectionChunk for the __TEXT,__text section.
//
class SectionChunk : public Chunk {
public:
static SectionChunk* make(DefinedAtom::ContentType,
MachOWriter &writer);
virtual StringRef segmentName() const;
virtual bool occupiesNoDiskSpace();
virtual void write(uint8_t *fileBuffer);
virtual const char* info();
StringRef sectionName();
uint32_t flags() const;
uint32_t permissions();
void appendAtom(const DefinedAtom*);
struct AtomInfo {
const DefinedAtom *atom;
uint64_t offsetInSection;
};
const std::vector<AtomInfo>& atoms() const;
private:
SectionChunk(StringRef seg,
StringRef sect,
uint32_t flags,
MachOWriter &writer);
StringRef _segmentName;
StringRef _sectionName;
MachOWriter &_writer;
uint32_t _flags;
uint32_t _permissions;
std::vector<AtomInfo> _atoms;
};
//
// A MachHeaderChunk represents the mach_header struct at the start
// of a mach-o executable file.
//
class MachHeaderChunk : public Chunk {
public:
MachHeaderChunk(const MachOTargetInfo &ti,
const File &file);
virtual StringRef segmentName() const;
virtual void write(uint8_t *fileBuffer);
virtual const char* info();
void recordLoadCommand(load_command*);
uint64_t loadCommandsSize();
private:
uint32_t magic(uint32_t cpuType);
mach_header _mh;
};
//
// A LoadCommandsChunk represents the variable length list of
// of load commands in a mach-o executable file right after the
// mach_header.
//
class LoadCommandsChunk : public Chunk {
public:
LoadCommandsChunk(MachHeaderChunk&,
const MachOTargetInfo &,
MachOWriter&);
virtual StringRef segmentName() const;
virtual void write(uint8_t *fileBuffer);
virtual const char* info();
void computeSize(const lld::File &file);
void addSection(SectionChunk*);
void updateLoadCommandContent(const lld::File &file);
private:
friend LoadCommandPaddingChunk;
void addLoadCommand(load_command* lc);
void setMachOSection(SectionChunk *chunk,
segment_command *seg, uint32_t index);
uint32_t permissionsFromSections(
const SmallVector<SectionChunk*,16> &);
bool use64BitMachO() const;
struct ChunkSegInfo {
SectionChunk *chunk;
segment_command *segment;
section_64 *section;
};
MachHeaderChunk &_mh;
const MachOTargetInfo &_targetInfo;
MachOWriter &_writer;
segment_command *_linkEditSegment;
symtab_command *_symbolTableLoadCommand;
entry_point_command *_entryPointLoadCommand;
thread_command *_threadLoadCommand;
dyld_info_command *_dyldInfoLoadCommand;
std::vector<load_command*> _loadCmds;
std::vector<ChunkSegInfo> _sectionInfo;
llvm::StringMap<uint32_t> _dylibNamesToOrdinal;
};
//
// A LoadCommandPaddingChunk represents the padding space between the last
// load commmand and the first section (usually __text) in the __TEXT
// segment.
//
class LoadCommandPaddingChunk : public Chunk {
public:
LoadCommandPaddingChunk(LoadCommandsChunk&);
virtual StringRef segmentName() const;
virtual void write(uint8_t *fileBuffer);
virtual const char* info();
void computeSize();
private:
LoadCommandsChunk& _loadCommandsChunk;
};
//
// LinkEditChunk is the base class for all chunks in the
// __LINKEDIT segment at the end of a mach-o executable.
//
class LinkEditChunk : public Chunk {
public:
LinkEditChunk();
virtual StringRef segmentName() const;
virtual void computeSize(const lld::File &file,
const std::vector<SectionChunk*>&) = 0;
};
//
// A DyldInfoChunk represents the bytes for any of the dyld info areas
// in the __LINKEDIT segment at the end of a mach-o executable.
//
class DyldInfoChunk : public LinkEditChunk {
public:
DyldInfoChunk(MachOWriter &);
virtual void write(uint8_t *fileBuffer);
protected:
void append_byte(uint8_t);
void append_uleb128(uint64_t);
void append_string(StringRef);
MachOWriter &_writer;
std::vector<uint8_t> _bytes;
};
//
// A BindingInfoChunk represents the bytes containing binding info
// in the __LINKEDIT segment at the end of a mach-o executable.
//
class BindingInfoChunk : public DyldInfoChunk {
public:
BindingInfoChunk(MachOWriter &);
virtual void computeSize(const lld::File &file,
const std::vector<SectionChunk*>&);
virtual const char* info();
};
//
// A LazyBindingInfoChunk represents the bytes containing lazy binding info
// in the __LINKEDIT segment at the end of a mach-o executable.
//
class LazyBindingInfoChunk : public DyldInfoChunk {
public:
LazyBindingInfoChunk(MachOWriter &);
virtual void computeSize(const lld::File &file,
const std::vector<SectionChunk*>&);
virtual const char* info();
private:
void updateHelper(const DefinedAtom *, uint32_t );
};
//
// A SymbolTableChunk represents the array of nlist structs in the
// __LINKEDIT segment at the end of a mach-o executable.
//
class SymbolTableChunk : public LinkEditChunk {
public:
SymbolTableChunk(SymbolStringsChunk&, MachOWriter&);
virtual void write(uint8_t *fileBuffer);
virtual void computeSize(const lld::File &file,
const std::vector<SectionChunk*>&);
virtual const char* info();
uint32_t count();
private:
uint8_t nType(const DefinedAtom*);
MachOWriter &_writer;
SymbolStringsChunk &_stringsChunk;
std::vector<nlist> _globalDefinedsymbols;
std::vector<nlist> _localDefinedsymbols;
std::vector<nlist> _undefinedsymbols;
};
//
// A SymbolStringsChunk represents the strings pointed to
// by nlist structs in the __LINKEDIT segment at the end
// of a mach-o executable.
//
class SymbolStringsChunk : public LinkEditChunk {
public:
SymbolStringsChunk();
virtual void write(uint8_t *fileBuffer);
virtual void computeSize(const lld::File &file,
const std::vector<SectionChunk*>&);
virtual const char* info();
uint32_t stringIndex(StringRef);
private:
std::vector<char> _strings;
};
//
// A MachOWriter manages all the Chunks that comprise a mach-o executable.
//
class MachOWriter : public Writer {
public:
MachOWriter(const MachOTargetInfo &ti);
virtual error_code writeFile(const lld::File &file, StringRef path);
virtual void addFiles(InputFiles&);
uint64_t addressOfAtom(const Atom *atom);
void findSegment(StringRef segmentName, uint32_t *segIndex,
uint64_t *segStartAddr, uint64_t *segEndAddr);
const std::vector<Chunk*> chunks() { return _chunks; }
mach_o::KindHandler &kindHandler() { return _referenceKindHandler; }
bool use64BitMachO() const;
private:
friend LoadCommandsChunk;
friend LazyBindingInfoChunk;
friend BindingInfoChunk;
void build(const lld::File &file);
void createChunks(const lld::File &file);
void buildAtomToAddressMap();
void assignFileOffsets();
void addLinkEditChunk(LinkEditChunk *chunk);
void buildLinkEdit(const lld::File &file);
void assignLinkEditFileOffsets();
void dump();
typedef llvm::DenseMap<const Atom*, uint64_t> AtomToAddress;
const MachOTargetInfo &_targetInfo;
mach_o::KindHandler &_referenceKindHandler;
CRuntimeFile _cRuntimeFile;
LoadCommandsChunk *_loadCommandsChunk;
LoadCommandPaddingChunk *_paddingChunk;
AtomToAddress _atomToAddress;
std::vector<Chunk*> _chunks;
std::vector<SectionChunk*> _sectionChunks;
std::vector<LinkEditChunk*> _linkEditChunks;
BindingInfoChunk *_bindingInfo;
LazyBindingInfoChunk *_lazyBindingInfo;
SymbolTableChunk *_symbolTableChunk;
SymbolStringsChunk *_stringsChunk;
const DefinedAtom *_entryAtom;
uint64_t _linkEditStartOffset;
uint64_t _linkEditStartAddress;
};
//===----------------------------------------------------------------------===//
// Chunk
//===----------------------------------------------------------------------===//
Chunk::Chunk()
: _size(0), _address(0), _fileOffset(0), _align2(0) {
}
bool Chunk::occupiesNoDiskSpace() {
return false;
}
uint64_t Chunk::size() const {
return _size;
}
uint64_t Chunk::align2() const {
return _align2;
}
uint64_t Chunk::address() const {
return _address;
}
uint64_t Chunk::fileOffset() const {
return _fileOffset;
}
uint64_t Chunk::alignTo(uint64_t value, uint8_t align2) {
uint64_t align = 1 << align2;
return ( (value + (align-1)) & (-align) );
}
void Chunk::assignFileOffset(uint64_t &curOffset, uint64_t &curAddress) {
if ( this->occupiesNoDiskSpace() ) {
// FileOffset does not change, but address space does change.
uint64_t alignedAddress = alignTo(curAddress, _align2);
_address = alignedAddress;
curAddress = alignedAddress + _size;
}
else {
// FileOffset and address both move by _size amount after alignment.
uint64_t alignPadding = alignTo(curAddress, _align2) - curAddress;
_fileOffset = curOffset + alignPadding;
_address = curAddress + alignPadding;
curOffset = _fileOffset + _size;
curAddress = _address + _size;
}
DEBUG_WITH_TYPE("WriterMachO-layout", llvm::dbgs()
<< " fileOffset="
<< llvm::format("0x%08X", _fileOffset)
<< " address="
<< llvm::format("0x%016X", _address)
<< " info=" << this->info() << "\n");
}
//===----------------------------------------------------------------------===//
// SectionChunk
//===----------------------------------------------------------------------===//
SectionChunk::SectionChunk(StringRef seg, StringRef sect,
uint32_t flags, MachOWriter &writer)
: _segmentName(seg), _sectionName(sect), _writer(writer),
_flags(flags), _permissions(0) {
}
SectionChunk* SectionChunk::make(DefinedAtom::ContentType type,
MachOWriter &writer) {
switch ( type ) {
case DefinedAtom::typeCode:
return new SectionChunk("__TEXT", "__text",
S_REGULAR | S_ATTR_PURE_INSTRUCTIONS, writer);
break;
case DefinedAtom::typeCString:
return new SectionChunk("__TEXT", "__cstring",
S_CSTRING_LITERALS, writer);
break;
case DefinedAtom::typeStub:
return new SectionChunk("__TEXT", "__stubs",
S_SYMBOL_STUBS | S_ATTR_PURE_INSTRUCTIONS, writer);
break;
case DefinedAtom::typeStubHelper:
return new SectionChunk("__TEXT", "__stub_helper",
S_REGULAR | S_ATTR_PURE_INSTRUCTIONS, writer);
break;
case DefinedAtom::typeLazyPointer:
return new SectionChunk("__DATA", "__la_symbol_ptr",
S_LAZY_SYMBOL_POINTERS, writer);
break;
case DefinedAtom::typeGOT:
return new SectionChunk("__DATA", "__got",
S_NON_LAZY_SYMBOL_POINTERS, writer);
break;
default:
assert(0 && "TO DO: add support for more sections");
break;
}
return nullptr;
}
bool SectionChunk::occupiesNoDiskSpace() {
return ( (_flags & SECTION_TYPE) == S_ZEROFILL );
}
StringRef SectionChunk::segmentName() const {
return _segmentName;
}
StringRef SectionChunk::sectionName() {
return _sectionName;
}
uint32_t SectionChunk::flags() const {
return _flags;
}
uint32_t SectionChunk::permissions() {
return _permissions;
}
const char* SectionChunk::info() {
return _sectionName.data();
}
const std::vector<SectionChunk::AtomInfo>& SectionChunk::atoms() const {
return _atoms;
}
void SectionChunk::appendAtom(const DefinedAtom *atom) {
// Figure out offset for atom in this section given alignment constraints.
uint64_t offset = _size;
DefinedAtom::Alignment atomAlign = atom->alignment();
uint64_t align2 = 1 << atomAlign.powerOf2;
uint64_t requiredModulus = atomAlign.modulus;
uint64_t currentModulus = (offset % align2);
if ( currentModulus != requiredModulus ) {
if ( requiredModulus > currentModulus )
offset += requiredModulus-currentModulus;
else
offset += align2+requiredModulus-currentModulus;
}
// Record max alignment of any atom in this section.
if ( align2 > _align2 )
_align2 = align2;
// Assign atom to this section with this offset.
SectionChunk::AtomInfo ai = {atom, offset};
_atoms.push_back(ai);
// Update section size to include this atom.
_size = offset + atom->size();
// Update permissions
DefinedAtom::ContentPermissions perms = atom->permissions();
if ( (perms & DefinedAtom::permR__) == DefinedAtom::permR__ )
_permissions |= VM_PROT_READ;
if ( (perms & DefinedAtom::permRW_) == DefinedAtom::permRW_ )
_permissions |= VM_PROT_WRITE;
if ( (perms & DefinedAtom::permR_X) == DefinedAtom::permR_X )
_permissions |= VM_PROT_EXECUTE;
}
void SectionChunk::write(uint8_t *chunkBuffer) {
// Each section's content is just its atoms' content.
for (const AtomInfo &atomInfo : _atoms ) {
// Copy raw content of atom to file buffer.
ArrayRef<uint8_t> content = atomInfo.atom->rawContent();
uint64_t contentSize = content.size();
if ( contentSize == 0 )
continue;
uint8_t* atomContent = chunkBuffer + atomInfo.offsetInSection;
::memcpy(atomContent, content.data(), contentSize);
// Apply fixups to file buffer
for (const Reference *ref : *atomInfo.atom) {
uint32_t offset = ref->offsetInAtom();
uint64_t targetAddress = 0;
if ( ref->target() != nullptr )
targetAddress = _writer.addressOfAtom(ref->target());
uint64_t fixupAddress = _writer.addressOfAtom(atomInfo.atom) + offset;
_writer.kindHandler().applyFixup(ref->kind(), ref->addend(),
&atomContent[offset], fixupAddress, targetAddress);
}
}
}
//===----------------------------------------------------------------------===//
// MachHeaderChunk
//===----------------------------------------------------------------------===//
MachHeaderChunk::MachHeaderChunk(const MachOTargetInfo &ti, const File &file) {
// Set up mach_header based on options
_mh.magic = this->magic(ti.getCPUType());
_mh.cputype = ti.getCPUType();
_mh.cpusubtype = ti.getCPUSubType();
_mh.filetype = ti.outputFileType();
_mh.ncmds = 0;
_mh.sizeofcmds = 0;
_mh.flags = 0;
_mh.reserved = 0;
_size = _mh.size();
}
StringRef MachHeaderChunk::segmentName() const {
return StringRef("__TEXT");
}
void MachHeaderChunk::write(uint8_t *chunkBuffer) {
_mh.copyTo(chunkBuffer);
}
const char* MachHeaderChunk::info() {
return "mach_header";
}
void MachHeaderChunk::recordLoadCommand(load_command* lc) {
_mh.recordLoadCommand(lc);
}
uint64_t MachHeaderChunk::loadCommandsSize() {
return _mh.sizeofcmds;
}
uint32_t MachHeaderChunk::magic(uint32_t cpuType) {
switch ( cpuType ) {
case CPU_TYPE_ARM:
case CPU_TYPE_I386:
return MH_MAGIC;
case CPU_TYPE_X86_64:
return MH_MAGIC_64;
}
llvm_unreachable("file CPU type not supported");
return 0;
}
//===----------------------------------------------------------------------===//
// LoadCommandsChunk
//===----------------------------------------------------------------------===//
LoadCommandsChunk::LoadCommandsChunk(MachHeaderChunk &mh,
const MachOTargetInfo &ti,
MachOWriter& writer)
: _mh(mh), _targetInfo(ti), _writer(writer),
_linkEditSegment(nullptr), _symbolTableLoadCommand(nullptr),
_entryPointLoadCommand(nullptr), _threadLoadCommand(nullptr),
_dyldInfoLoadCommand(nullptr) {
}
StringRef LoadCommandsChunk::segmentName() const {
return StringRef("__TEXT");
}
void LoadCommandsChunk::write(uint8_t *chunkBuffer) {
uint8_t* p = chunkBuffer;
for ( load_command* lc : _loadCmds ) {
assert( ((uintptr_t)p & 0x3) == 0);
lc->copyTo(p);
p += lc->cmdsize;
}
}
const char* LoadCommandsChunk::info() {
return "load commands";
}
void LoadCommandsChunk::setMachOSection(SectionChunk *chunk,
segment_command *seg, uint32_t index) {
for (ChunkSegInfo &entry : _sectionInfo) {
if ( entry.chunk == chunk ) {
entry.section = &(seg->sections[index]);
entry.segment = seg;
return;
}
}
assert(0 && "setMachOSection() chunk not found");
}
uint32_t LoadCommandsChunk::permissionsFromSections(
const SmallVector<SectionChunk*,16> &sections) {
uint32_t result = 0;
for (SectionChunk *chunk : sections) {
result |= chunk->permissions();
}
return result;
}
void LoadCommandsChunk::computeSize(const lld::File &file) {
const bool is64 = _writer.use64BitMachO();
// Main executables have a __PAGEZERO segment.
uint64_t pageZeroSize = _targetInfo.pageZeroSize();
if ( pageZeroSize != 0 ) {
assert(is64 || (pageZeroSize < 0xFFFFFFFF));
segment_command* pzSegCmd = new segment_command(0, is64);
strcpy(pzSegCmd->segname, "__PAGEZERO");
pzSegCmd->vmaddr = 0;
pzSegCmd->vmsize = pageZeroSize;
pzSegCmd->fileoff = 0;
pzSegCmd->filesize = 0;
pzSegCmd->maxprot = 0;
pzSegCmd->initprot = 0;
pzSegCmd->nsects = 0;
pzSegCmd->flags = 0;
this->addLoadCommand(pzSegCmd);
}
// Add other segment load commands
StringRef lastSegName = StringRef("__TEXT");
SmallVector<SectionChunk*,16> sections;
for (ChunkSegInfo &entry : _sectionInfo) {
StringRef entryName = entry.chunk->segmentName();
if ( !lastSegName.equals(entryName) ) {
// Start of new segment, so create load command for all previous sections.
segment_command* segCmd = new segment_command(sections.size(), is64);
strncpy(segCmd->segname, lastSegName.data(), 16);
segCmd->initprot = this->permissionsFromSections(sections);
segCmd->maxprot = VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE;
this->addLoadCommand(segCmd);
unsigned int index = 0;
for (SectionChunk *chunk : sections) {
this->setMachOSection(chunk, segCmd, index);
++index;
}
// Reset to begin new segment.
sections.clear();
lastSegName = entryName;
}
sections.push_back(entry.chunk);
}
// Add last segment load command.
segment_command* segCmd = new segment_command(sections.size(), is64);
strncpy(segCmd->segname, lastSegName.data(), 16);
segCmd->initprot = this->permissionsFromSections(sections);;
segCmd->maxprot = VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE;
this->addLoadCommand(segCmd);
unsigned int index = 0;
for (SectionChunk *chunk : sections) {
this->setMachOSection(chunk, segCmd, index);
++index;
}
// Add LINKEDIT segment load command
_linkEditSegment = new segment_command(0, is64);
strcpy(_linkEditSegment->segname, "__LINKEDIT");
_linkEditSegment->initprot = VM_PROT_READ;
_linkEditSegment->maxprot = VM_PROT_READ;
this->addLoadCommand(_linkEditSegment);
// Add dyld load command.
this->addLoadCommand(new dylinker_command("/usr/lib/dyld", is64));
// Add dylib load commands.
for (const SharedLibraryAtom* shlibAtom : file.sharedLibrary() ) {
StringRef installName = shlibAtom->loadName();
if ( _dylibNamesToOrdinal.count(installName) == 0 ) {
uint32_t ord = _dylibNamesToOrdinal.size();
_dylibNamesToOrdinal[installName] = ord;
}
}
for (llvm::StringMap<uint32_t>::iterator it=_dylibNamesToOrdinal.begin(),
end=_dylibNamesToOrdinal.end(); it != end; ++it) {
this->addLoadCommand(new dylib_command(it->first(), is64));
}
// Add symbol table load command
_symbolTableLoadCommand = new symtab_command(is64);
this->addLoadCommand(_symbolTableLoadCommand);
// Add dyld info load command
_dyldInfoLoadCommand = new dyld_info_command(is64);
this->addLoadCommand(_dyldInfoLoadCommand);
// Add entry point load command to main executables
if (_targetInfo.addEntryPointLoadCommand()) {
_entryPointLoadCommand = new entry_point_command(is64);
this->addLoadCommand(_entryPointLoadCommand);
} else if (_targetInfo.addUnixThreadLoadCommand()) {
_threadLoadCommand = new thread_command(_targetInfo.getCPUType(), is64);
this->addLoadCommand(_threadLoadCommand);
}
// Compute total size.
_size = _mh.loadCommandsSize();
}
void LoadCommandsChunk::updateLoadCommandContent(const lld::File &file) {
// Update segment/section information in segment load commands
segment_command *lastSegment = nullptr;
for (ChunkSegInfo &entry : _sectionInfo) {
// Set section info.
::strncpy(entry.section->sectname, entry.chunk->sectionName().data(), 16);
::strncpy(entry.section->segname, entry.chunk->segmentName().data(), 16);
entry.section->addr = entry.chunk->address();
entry.section->size = entry.chunk->size();
entry.section->offset = entry.chunk->fileOffset();
entry.section->align = entry.chunk->align2();
entry.section->reloff = 0;
entry.section->nreloc = 0;
entry.section->flags = entry.chunk->flags();
// Adjust segment info if needed.
if ( entry.segment != lastSegment ) {
// This is first section in segment.
if ( strcmp(entry.segment->segname, "__TEXT") == 0 ) {
// __TEXT segment is special need mach_header section.
entry.segment->vmaddr = _writer._chunks.front()->address();
entry.segment->fileoff = _writer._chunks.front()->fileOffset();
}
else {
entry.segment->vmaddr = entry.chunk->address();
entry.segment->fileoff = entry.chunk->fileOffset();
}
lastSegment = entry.segment;
}
uint64_t sectionEndAddr = entry.section->addr + entry.section->size;
if ( entry.segment->vmaddr + entry.segment->vmsize < sectionEndAddr) {
uint64_t sizeToEndOfSection = sectionEndAddr - entry.segment->vmaddr;
entry.segment->vmsize = alignTo(sizeToEndOfSection, 12);
// zero-fill sections do not increase the segment's filesize
if ( ! entry.chunk->occupiesNoDiskSpace() ) {
entry.segment->filesize = alignTo(sizeToEndOfSection, 12);
}
}
}
uint64_t linkEditSize = _writer._stringsChunk->fileOffset()
+ _writer._stringsChunk->size()
- _writer._linkEditStartOffset;
_linkEditSegment->vmaddr = _writer._linkEditStartAddress;
_linkEditSegment->vmsize = alignTo(linkEditSize,12);
_linkEditSegment->fileoff = _writer._linkEditStartOffset;
_linkEditSegment->filesize = linkEditSize;
// Update dyld_info load command.
_dyldInfoLoadCommand->bind_off = _writer._bindingInfo->fileOffset();
_dyldInfoLoadCommand->bind_size = _writer._bindingInfo->size();
_dyldInfoLoadCommand->lazy_bind_off = _writer._lazyBindingInfo->fileOffset();
_dyldInfoLoadCommand->lazy_bind_size = _writer._lazyBindingInfo->size();
// Update symbol table load command.
_symbolTableLoadCommand->symoff = _writer._symbolTableChunk->fileOffset();
_symbolTableLoadCommand->nsyms = _writer._symbolTableChunk->count();
_symbolTableLoadCommand->stroff = _writer._stringsChunk->fileOffset();
_symbolTableLoadCommand->strsize = _writer._stringsChunk->size();
// Update entry point
if ( _entryPointLoadCommand != nullptr ) {
const Atom *mainAtom = _writer._entryAtom;
assert(mainAtom != nullptr);
uint32_t entryOffset = _writer.addressOfAtom(mainAtom) - _mh.address();
_entryPointLoadCommand->entryoff = entryOffset;
}
else if ( _threadLoadCommand != nullptr ) {
const Atom *startAtom = _writer._entryAtom;
assert(startAtom != nullptr);
_threadLoadCommand->setPC(_writer.addressOfAtom(startAtom));
}
}
void LoadCommandsChunk::addSection(SectionChunk* chunk) {
LoadCommandsChunk::ChunkSegInfo csi = {chunk, nullptr, nullptr};
_sectionInfo.push_back(csi);
}
void LoadCommandsChunk::addLoadCommand(load_command* lc) {
_mh.recordLoadCommand(lc);
_loadCmds.push_back(lc);
}
//===----------------------------------------------------------------------===//
// LoadCommandPaddingChunk
//===----------------------------------------------------------------------===//
LoadCommandPaddingChunk::LoadCommandPaddingChunk(LoadCommandsChunk& lcc)
: _loadCommandsChunk(lcc) {
}
StringRef LoadCommandPaddingChunk::segmentName() const {
return StringRef("__TEXT");
}
void LoadCommandPaddingChunk::write(uint8_t *chunkBuffer) {
// Zero fill padding.
}
const char* LoadCommandPaddingChunk::info() {
return "padding";
}
// Segments are page sized. Normally, any extra space not used by atoms
// is put at the end of the last page. But the __TEXT segment is special.
// Any extra space is put between the load commands and the first section.
// The padding is put there to allow the load commands to be
// post-processed which might potentially grow them.
void LoadCommandPaddingChunk::computeSize() {
// Layout __TEXT sections backwards from end of page to get padding up front.
uint64_t addr = 0;
std::vector<LoadCommandsChunk::ChunkSegInfo>& sects
= _loadCommandsChunk._sectionInfo;
for (auto it=sects.rbegin(), end=sects.rend(); it != end; ++it) {
LoadCommandsChunk::ChunkSegInfo &entry = *it;
if ( !entry.chunk->segmentName().equals("__TEXT") )
continue;
addr -= entry.chunk->size();
addr = addr & (0 - (1 << entry.chunk->align2()));
}
// Subtract out size of mach_header and all load commands.
addr -= _loadCommandsChunk._mh.size();
addr -= _loadCommandsChunk.size();
// Modulo page size to get padding needed between load commands
// and first section.
_size = (addr % 4096);
}
//===----------------------------------------------------------------------===//
// LinkEditChunk
//===----------------------------------------------------------------------===//
LinkEditChunk::LinkEditChunk() {
_align2 = 3;
}
StringRef LinkEditChunk::segmentName() const {
return StringRef("__LINKEDIT");
}
//===----------------------------------------------------------------------===//
// DyldInfoChunk
//===----------------------------------------------------------------------===//
DyldInfoChunk::DyldInfoChunk(MachOWriter &writer)
: _writer(writer) {
}
void DyldInfoChunk::write(uint8_t *chunkBuffer) {
::memcpy(chunkBuffer, &_bytes[0], _bytes.size());
}
void DyldInfoChunk::append_byte(uint8_t b) {
_bytes.push_back(b);
}
void DyldInfoChunk::append_string(StringRef str) {
_bytes.insert(_bytes.end(), str.begin(), str.end());
_bytes.push_back('\0');
}
void DyldInfoChunk::append_uleb128(uint64_t value) {
uint8_t byte;
do {
byte = value & 0x7F;
value &= ~0x7F;
if ( value != 0 )
byte |= 0x80;
_bytes.push_back(byte);
value = value >> 7;
} while( byte >= 0x80 );
}
//===----------------------------------------------------------------------===//
// BindingInfoChunk
//===----------------------------------------------------------------------===//
BindingInfoChunk::BindingInfoChunk(MachOWriter &writer)
: DyldInfoChunk(writer) {
}
const char* BindingInfoChunk::info() {
return "binding info";
}
void BindingInfoChunk::computeSize(const lld::File &file,
const std::vector<SectionChunk*> &chunks) {
for (const SectionChunk *chunk : chunks ) {
// skip lazy pointer section
if ( chunk->flags() == S_LAZY_SYMBOL_POINTERS )
continue;
// skip code sections
if ( chunk->flags() == (S_REGULAR | S_ATTR_PURE_INSTRUCTIONS) )
continue;
uint64_t segStartAddr = 0;
uint64_t segEndAddr = 0;
uint32_t segIndex = 0;
_writer.findSegment(chunk->segmentName(),
&segIndex, &segStartAddr, &segEndAddr);
for (const SectionChunk::AtomInfo &info : chunk->atoms() ) {
const DefinedAtom* atom = info.atom;
StringRef targetName;
int ordinal;
// look for fixups pointing to shlib atoms
for (const Reference *ref : *atom ) {
const Atom *target = ref->target();
if ( target != nullptr ) {
const SharedLibraryAtom *shlTarget
= dyn_cast<SharedLibraryAtom>(target);
if ( shlTarget != nullptr ) {
assert(_writer.kindHandler().isPointer(ref->kind()));
targetName = shlTarget->name();
ordinal = 1; // FIXME
}
}
}
if ( targetName.empty() )
continue;
// write location of fixup
this->append_byte(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB | segIndex);
uint64_t address = _writer.addressOfAtom(atom);
this->append_uleb128(address - segStartAddr);
// write ordinal
if ( ordinal <= 0 ) {
// special lookups are encoded as negative numbers in BindingInfo
this->append_byte(BIND_OPCODE_SET_DYLIB_SPECIAL_IMM
| (ordinal & BIND_IMMEDIATE_MASK) );
}
else if ( ordinal <= 15 ) {
// small ordinals are encoded in opcode
this->append_byte(BIND_OPCODE_SET_DYLIB_ORDINAL_IMM | ordinal);
}
else {
this->append_byte(BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB);
this->append_uleb128(ordinal);
}
// write binding type
this->append_byte(BIND_OPCODE_SET_TYPE_IMM | BIND_TYPE_POINTER);
// write symbol name and flags
int flags = 0;
this->append_byte(BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM | flags);
this->append_string(targetName);
// write do bind
this->append_byte(BIND_OPCODE_DO_BIND);
this->append_byte(BIND_OPCODE_DONE);
}
}
_size = _bytes.size();
}
//===----------------------------------------------------------------------===//
// LazyBindingInfoChunk
//===----------------------------------------------------------------------===//
LazyBindingInfoChunk::LazyBindingInfoChunk(MachOWriter &writer)
: DyldInfoChunk(writer) {
}
const char* LazyBindingInfoChunk::info() {
return "lazy binding info";
}
//
// Called when lazy-binding-info is being laid out in __LINKEDIT. We need
// to find the helper atom which contains the instruction which loads an
// immediate value that is the offset into the lazy-binding-info, and set
// that immediate value to be the offset parameter.
void LazyBindingInfoChunk::updateHelper(const DefinedAtom *lazyPointerAtom,
uint32_t offset) {
for (const Reference *ref : *lazyPointerAtom ) {
if ( ! _writer.kindHandler().isPointer(ref->kind() ) )
continue;
const Atom *targ = ref->target();
const DefinedAtom *helperAtom = dyn_cast<DefinedAtom>(targ);
assert(helperAtom != nullptr);
// Found helper atom. Search it for Reference that is lazy immediate value.
for (const Reference *href : *helperAtom ) {
if ( _writer.kindHandler().isLazyImmediate(href->kind()) ) {
(const_cast<Reference*>(href))->setAddend(offset);
return;
}
}
}
assert(0 && "could not update helper lazy immediate value");
}
void LazyBindingInfoChunk::computeSize(const lld::File &file,
const std::vector<SectionChunk*> &chunks) {
for (const SectionChunk *chunk : chunks ) {
if ( chunk->flags() != S_LAZY_SYMBOL_POINTERS )
continue;
uint64_t segStartAddr = 0;
uint64_t segEndAddr = 0;
uint32_t segIndex = 0;
_writer.findSegment(chunk->segmentName(),
&segIndex, &segStartAddr, &segEndAddr);
for (const SectionChunk::AtomInfo &info : chunk->atoms() ) {
const DefinedAtom *lazyPointerAtom = info.atom;
assert(lazyPointerAtom->contentType() == DefinedAtom::typeLazyPointer);
// Update help to have offset of the lazy binding info.
this->updateHelper(lazyPointerAtom, _bytes.size());
// Write location of fixup.
this->append_byte(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB | segIndex);
uint64_t address = _writer.addressOfAtom(lazyPointerAtom);
this->append_uleb128(address - segStartAddr);
// write ordinal
int ordinal = 1;
if ( ordinal <= 0 ) {
// special lookups are encoded as negative numbers in BindingInfo
this->append_byte(BIND_OPCODE_SET_DYLIB_SPECIAL_IMM
| (ordinal & BIND_IMMEDIATE_MASK) );
}
else if ( ordinal <= 15 ) {
// small ordinals are encoded in opcode
this->append_byte(BIND_OPCODE_SET_DYLIB_ORDINAL_IMM | ordinal);
}
else {
this->append_byte(BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB);
this->append_uleb128(ordinal);
}
// write symbol name and flags
int flags = 0;
StringRef name;
for (const Reference *ref : *lazyPointerAtom ) {
if ( _writer.kindHandler().isLazyTarget(ref->kind()) ) {
const Atom *shlib = ref->target();
assert(shlib != nullptr);
name = shlib->name();
}
}
assert(!name.empty());
this->append_byte(BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM | flags);
this->append_string(name);
// write do bind
this->append_byte(BIND_OPCODE_DO_BIND);
this->append_byte(BIND_OPCODE_DONE);
}
}
_size = _bytes.size();
}
//===----------------------------------------------------------------------===//
// SymbolTableChunk
//===----------------------------------------------------------------------===//
SymbolTableChunk::SymbolTableChunk(SymbolStringsChunk &str, MachOWriter &wrtr)
: _writer(wrtr), _stringsChunk(str) {
}
void SymbolTableChunk::write(uint8_t *chunkBuffer) {
const bool is64 = _writer.use64BitMachO();
const unsigned nlistSize = nlist::size(is64);
uint8_t *p = chunkBuffer;
for ( nlist &sym : _globalDefinedsymbols ) {
sym.copyTo(p, is64);
p += nlistSize;
}
for ( nlist &sym : _localDefinedsymbols ) {
sym.copyTo(p, is64);
p += nlistSize;
}
for ( nlist &sym : _undefinedsymbols ) {
sym.copyTo(p, is64);
p += nlistSize;
}
}
const char* SymbolTableChunk::info() {
return "symbol tables ";
}
uint32_t SymbolTableChunk::count() {
return _globalDefinedsymbols.size()
+ _localDefinedsymbols.size()
+ _undefinedsymbols.size();
}
uint8_t SymbolTableChunk::nType(const DefinedAtom *atom) {
uint8_t result = N_SECT;
switch ( atom->scope() ) {
case DefinedAtom::scopeTranslationUnit:
break;
case DefinedAtom::scopeLinkageUnit:
result |= N_EXT | N_PEXT;
break;
case DefinedAtom::scopeGlobal:
result |= N_EXT;
break;
}
return result;
}
void SymbolTableChunk::computeSize(const lld::File &file,
const std::vector<SectionChunk*> &chunks) {
// Add symbols for definitions
unsigned int sectionIndex = 1;
for (const SectionChunk *chunk : chunks ) {
for (const SectionChunk::AtomInfo &info : chunk->atoms() ) {
if ( info.atom->name().empty() )
continue;
uint64_t atomAddress = chunk->address() + info.offsetInSection;
nlist sym;
sym.n_strx = _stringsChunk.stringIndex(info.atom->name());
sym.n_type = this->nType(info.atom);
sym.n_sect = sectionIndex;
sym.n_value = atomAddress;
if ( info.atom->scope() == DefinedAtom::scopeGlobal )
_globalDefinedsymbols.push_back(sym);
else
_localDefinedsymbols.push_back(sym);
}
++sectionIndex;
}
// Add symbols for undefined/sharedLibrary symbols
for (const SharedLibraryAtom* atom : file.sharedLibrary() ) {
nlist sym;
sym.n_strx = _stringsChunk.stringIndex(atom->name());
sym.n_type = N_UNDF;
sym.n_sect = 0;
sym.n_value = 0;
_undefinedsymbols.push_back(sym);
}
_size = nlist::size(_writer.use64BitMachO()) * this->count();
}
//===----------------------------------------------------------------------===//
// SymbolStringsChunk
//===----------------------------------------------------------------------===//
SymbolStringsChunk::SymbolStringsChunk() {
// mach-o reserves the first byte in the string pool so that
// zero is never a valid string index.
_strings.push_back('\0');
}
void SymbolStringsChunk::write(uint8_t *chunkBuffer) {
::memcpy(chunkBuffer, &_strings[0], _strings.size());
}
const char* SymbolStringsChunk::info() {
return "symbol strings ";
}
void SymbolStringsChunk::computeSize(const lld::File &file,
const std::vector<SectionChunk*>&) {
_size = _strings.size();
}
uint32_t SymbolStringsChunk::stringIndex(StringRef str) {
uint32_t result = _strings.size();
_strings.insert(_strings.end(), str.begin(), str.end());
_strings.push_back('\0');
return result;
}
//===----------------------------------------------------------------------===//
// MachOWriter
//===----------------------------------------------------------------------===//
MachOWriter::MachOWriter(const MachOTargetInfo &ti)
: _targetInfo(ti),
_referenceKindHandler(ti.kindHandler()),
_cRuntimeFile(ti),
_bindingInfo(nullptr), _lazyBindingInfo(nullptr),
_symbolTableChunk(nullptr), _stringsChunk(nullptr), _entryAtom(nullptr),
_linkEditStartOffset(0), _linkEditStartAddress(0) {
}
void MachOWriter::build(const lld::File &file) {
// Create objects for each chunk.
this->createChunks(file);
// Now that SectionChunks have sizes, load commands can be laid out
_loadCommandsChunk->computeSize(file);
// Now that load commands are sized, padding can be computed
_paddingChunk->computeSize();
// Now that all chunks (except linkedit) have sizes, assign file offsets
this->assignFileOffsets();
// Now chunks have file offsets each atom can be assigned an address
this->buildAtomToAddressMap();
// Now that atoms have address, symbol table can be build
this->buildLinkEdit(file);
// Assign file offsets to linkedit chunks
this->assignLinkEditFileOffsets();
// Finally, update load commands to reflect linkEdit layout
_loadCommandsChunk->updateLoadCommandContent(file);
}
void MachOWriter::createChunks(const lld::File &file) {
// Assign atoms to chunks, creating new chunks as needed
std::map<DefinedAtom::ContentType, SectionChunk*> map;
for (const DefinedAtom* atom : file.defined() ) {
assert( atom->sectionChoice() == DefinedAtom::sectionBasedOnContent );
DefinedAtom::ContentType type = atom->contentType();
auto pos = map.find(type);
if ( pos == map.end() ) {
SectionChunk *chunk = SectionChunk::make(type, *this);
map[type] = chunk;
chunk->appendAtom(atom);
}
else {
pos->second->appendAtom(atom);
}
}
// Sort Chunks so ones in same segment are contiguous.
// Make chunks in __TEXT for mach_header and load commands at start.
MachHeaderChunk *mhc = new MachHeaderChunk(_targetInfo, file);
_chunks.push_back(mhc);
_loadCommandsChunk = new LoadCommandsChunk(*mhc, _targetInfo, *this);
_chunks.push_back(_loadCommandsChunk);
_paddingChunk = new LoadCommandPaddingChunk(*_loadCommandsChunk);
_chunks.push_back(_paddingChunk);
for (auto it=map.begin(); it != map.end(); ++it) {
_chunks.push_back(it->second);
_sectionChunks.push_back(it->second);
_loadCommandsChunk->addSection(it->second);
}
// Make LINKEDIT chunks.
_bindingInfo = new BindingInfoChunk(*this);
_lazyBindingInfo = new LazyBindingInfoChunk(*this);
_stringsChunk = new SymbolStringsChunk();
_symbolTableChunk = new SymbolTableChunk(*_stringsChunk, *this);
this->addLinkEditChunk(_bindingInfo);
this->addLinkEditChunk(_lazyBindingInfo);
this->addLinkEditChunk(_symbolTableChunk);
this->addLinkEditChunk(_stringsChunk);
}
void MachOWriter::addLinkEditChunk(LinkEditChunk *chunk) {
_linkEditChunks.push_back(chunk);
_chunks.push_back(chunk);
}
void MachOWriter::buildAtomToAddressMap() {
DEBUG_WITH_TYPE("WriterMachO-layout", llvm::dbgs()
<< "assign atom addresses:\n");
const bool lookForEntry = _targetInfo.outputTypeHasEntry();
for (SectionChunk *chunk : _sectionChunks ) {
for (const SectionChunk::AtomInfo &info : chunk->atoms() ) {
_atomToAddress[info.atom] = chunk->address() + info.offsetInSection;
if ( lookForEntry
&& (info.atom->contentType() == DefinedAtom::typeCode)
&& (info.atom->size() != 0)
&& info.atom->name() == _targetInfo.entrySymbolName()) {
_entryAtom = info.atom;
}
DEBUG_WITH_TYPE("WriterMachO-layout", llvm::dbgs()
<< " address="
<< llvm::format("0x%016X", _atomToAddress[info.atom])
<< " atom=" << info.atom
<< " name=" << info.atom->name() << "\n");
}
}
}
//void MachOWriter::dump() {
// for ( Chunk *chunk : _chunks ) {
// fprintf(stderr, "size=0x%08llX, fileOffset=0x%08llX, address=0x%08llX %s\n",
// chunk->size(), chunk->fileOffset(),chunk->address(), chunk->info());
// }
//}
void MachOWriter::assignFileOffsets() {
DEBUG_WITH_TYPE("WriterMachO-layout", llvm::dbgs()
<< "assign file offsets:\n");
uint64_t offset = 0;
uint64_t address = _targetInfo.pageZeroSize();
for ( Chunk *chunk : _chunks ) {
if ( chunk->segmentName().equals("__LINKEDIT") ) {
_linkEditStartOffset = Chunk::alignTo(offset, 12);
_linkEditStartAddress = Chunk::alignTo(address, 12);
break;
}
chunk->assignFileOffset(offset, address);
}
}
void MachOWriter::assignLinkEditFileOffsets() {
DEBUG_WITH_TYPE("WriterMachO-layout", llvm::dbgs()
<< "assign LINKEDIT file offsets:\n");
uint64_t offset = _linkEditStartOffset;
uint64_t address = _linkEditStartAddress;
for ( Chunk *chunk : _linkEditChunks ) {
chunk->assignFileOffset(offset, address);
}
}
void MachOWriter::buildLinkEdit(const lld::File &file) {
for (LinkEditChunk *chunk : _linkEditChunks) {
chunk->computeSize(file, _sectionChunks);
}
}
uint64_t MachOWriter::addressOfAtom(const Atom *atom) {
return _atomToAddress[atom];
}
void MachOWriter::findSegment(StringRef segmentName, uint32_t *segIndex,
uint64_t *segStartAddr, uint64_t *segEndAddr) {
const uint64_t kInvalidAddress = (uint64_t)(-1);
StringRef lastSegName("__TEXT");
*segIndex = 0;
if ( _targetInfo.pageZeroSize() != 0 ) {
*segIndex = 1;
}
*segStartAddr = kInvalidAddress;
*segEndAddr = kInvalidAddress;
for (SectionChunk *chunk : _sectionChunks ) {
if ( ! lastSegName.equals(chunk->segmentName()) ) {
*segIndex += 1;
lastSegName = chunk->segmentName();
}
if ( chunk->segmentName().equals(segmentName) ) {
uint64_t chunkEndAddr = chunk->address() + chunk->size();
if ( *segStartAddr == kInvalidAddress ) {
*segStartAddr = chunk->address();
*segEndAddr = chunkEndAddr;
}
else if ( *segEndAddr < chunkEndAddr ) {
*segEndAddr = chunkEndAddr;
}
}
}
}
bool MachOWriter::use64BitMachO() const {
switch (_targetInfo.arch()) {
case MachOTargetInfo::arch_x86_64:
return true;
case MachOTargetInfo::arch_x86:
case MachOTargetInfo::arch_armv6:
case MachOTargetInfo::arch_armv7:
case MachOTargetInfo::arch_armv7s:
return false;
default:
llvm_unreachable("Unknown mach-o arch");
}
}
//
// Creates a mach-o final linked image from the given atom graph and writes
// it to the supplied output stream.
//
error_code MachOWriter::writeFile(const lld::File &file, StringRef path) {
this->build(file);
// FIXME: re-enable when FileOutputBuffer is in LLVMSupport.a
uint64_t totalSize = _chunks.back()->fileOffset() + _chunks.back()->size();
OwningPtr<llvm::FileOutputBuffer> buffer;
error_code ec = llvm::FileOutputBuffer::create(path,
totalSize, buffer,
llvm::FileOutputBuffer::F_executable);
if ( ec )
return ec;
DEBUG_WITH_TYPE("WriterMachO-layout", llvm::dbgs() << "writeFile:\n");
for ( Chunk *chunk : _chunks ) {
DEBUG_WITH_TYPE("WriterMachO-layout", llvm::dbgs()
<< " fileOffset="
<< llvm::format("0x%08X", chunk->fileOffset())
<< " chunk="
<< chunk->info()
<< "\n");
chunk->write(buffer->getBufferStart()+chunk->fileOffset());
}
return buffer->commit();
}
void MachOWriter::addFiles(InputFiles &inputFiles) {
inputFiles.prependFile(_cRuntimeFile);
}
} // namespace mach_o
std::unique_ptr<Writer> createWriterMachO(const MachOTargetInfo &ti) {
return std::unique_ptr<Writer>(new lld::mach_o::MachOWriter(ti));
}
} // namespace lld
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