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//===- MachOWriter.cpp ------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "MachOWriter.h"
#include "MachOLayoutBuilder.h"
#include "Object.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/Object/MachO.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/ErrorHandling.h"
#include <memory>
namespace llvm {
namespace objcopy {
namespace macho {
size_t MachOWriter::headerSize() const {
return Is64Bit ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header);
}
size_t MachOWriter::loadCommandsSize() const { return O.Header.SizeOfCmds; }
size_t MachOWriter::symTableSize() const {
return O.SymTable.Symbols.size() *
(Is64Bit ? sizeof(MachO::nlist_64) : sizeof(MachO::nlist));
}
size_t MachOWriter::totalSize() const {
// Going from tail to head and looking for an appropriate "anchor" to
// calculate the total size assuming that all the offsets are either valid
// ("true") or 0 (0 indicates that the corresponding part is missing).
SmallVector<size_t, 7> Ends;
if (O.SymTabCommandIndex) {
const MachO::symtab_command &SymTabCommand =
O.LoadCommands[*O.SymTabCommandIndex]
.MachOLoadCommand.symtab_command_data;
if (SymTabCommand.symoff)
Ends.push_back(SymTabCommand.symoff + symTableSize());
if (SymTabCommand.stroff)
Ends.push_back(SymTabCommand.stroff + SymTabCommand.strsize);
}
if (O.DyLdInfoCommandIndex) {
const MachO::dyld_info_command &DyLdInfoCommand =
O.LoadCommands[*O.DyLdInfoCommandIndex]
.MachOLoadCommand.dyld_info_command_data;
if (DyLdInfoCommand.rebase_off) {
assert((DyLdInfoCommand.rebase_size == O.Rebases.Opcodes.size()) &&
"Incorrect rebase opcodes size");
Ends.push_back(DyLdInfoCommand.rebase_off + DyLdInfoCommand.rebase_size);
}
if (DyLdInfoCommand.bind_off) {
assert((DyLdInfoCommand.bind_size == O.Binds.Opcodes.size()) &&
"Incorrect bind opcodes size");
Ends.push_back(DyLdInfoCommand.bind_off + DyLdInfoCommand.bind_size);
}
if (DyLdInfoCommand.weak_bind_off) {
assert((DyLdInfoCommand.weak_bind_size == O.WeakBinds.Opcodes.size()) &&
"Incorrect weak bind opcodes size");
Ends.push_back(DyLdInfoCommand.weak_bind_off +
DyLdInfoCommand.weak_bind_size);
}
if (DyLdInfoCommand.lazy_bind_off) {
assert((DyLdInfoCommand.lazy_bind_size == O.LazyBinds.Opcodes.size()) &&
"Incorrect lazy bind opcodes size");
Ends.push_back(DyLdInfoCommand.lazy_bind_off +
DyLdInfoCommand.lazy_bind_size);
}
if (DyLdInfoCommand.export_off) {
assert((DyLdInfoCommand.export_size == O.Exports.Trie.size()) &&
"Incorrect trie size");
Ends.push_back(DyLdInfoCommand.export_off + DyLdInfoCommand.export_size);
}
}
if (O.DySymTabCommandIndex) {
const MachO::dysymtab_command &DySymTabCommand =
O.LoadCommands[*O.DySymTabCommandIndex]
.MachOLoadCommand.dysymtab_command_data;
if (DySymTabCommand.indirectsymoff)
Ends.push_back(DySymTabCommand.indirectsymoff +
sizeof(uint32_t) * O.IndirectSymTable.Symbols.size());
}
if (O.CodeSignatureCommandIndex) {
const MachO::linkedit_data_command &LinkEditDataCommand =
O.LoadCommands[*O.CodeSignatureCommandIndex]
.MachOLoadCommand.linkedit_data_command_data;
if (LinkEditDataCommand.dataoff)
Ends.push_back(LinkEditDataCommand.dataoff +
LinkEditDataCommand.datasize);
}
if (O.DataInCodeCommandIndex) {
const MachO::linkedit_data_command &LinkEditDataCommand =
O.LoadCommands[*O.DataInCodeCommandIndex]
.MachOLoadCommand.linkedit_data_command_data;
if (LinkEditDataCommand.dataoff)
Ends.push_back(LinkEditDataCommand.dataoff +
LinkEditDataCommand.datasize);
}
if (O.FunctionStartsCommandIndex) {
const MachO::linkedit_data_command &LinkEditDataCommand =
O.LoadCommands[*O.FunctionStartsCommandIndex]
.MachOLoadCommand.linkedit_data_command_data;
if (LinkEditDataCommand.dataoff)
Ends.push_back(LinkEditDataCommand.dataoff +
LinkEditDataCommand.datasize);
}
// Otherwise, use the last section / reloction.
for (const LoadCommand &LC : O.LoadCommands)
for (const std::unique_ptr<Section> &S : LC.Sections) {
if (!S->hasValidOffset()) {
assert((S->Offset == 0) && "Skipped section's offset must be zero");
assert((S->isVirtualSection() || S->Size == 0) &&
"Non-zero-fill sections with zero offset must have zero size");
continue;
}
assert((S->Offset != 0) &&
"Non-zero-fill section's offset cannot be zero");
Ends.push_back(S->Offset + S->Size);
if (S->RelOff)
Ends.push_back(S->RelOff +
S->NReloc * sizeof(MachO::any_relocation_info));
}
if (!Ends.empty())
return *std::max_element(Ends.begin(), Ends.end());
// Otherwise, we have only Mach header and load commands.
return headerSize() + loadCommandsSize();
}
void MachOWriter::writeHeader() {
MachO::mach_header_64 Header;
Header.magic = O.Header.Magic;
Header.cputype = O.Header.CPUType;
Header.cpusubtype = O.Header.CPUSubType;
Header.filetype = O.Header.FileType;
Header.ncmds = O.Header.NCmds;
Header.sizeofcmds = O.Header.SizeOfCmds;
Header.flags = O.Header.Flags;
Header.reserved = O.Header.Reserved;
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(Header);
auto HeaderSize =
Is64Bit ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header);
memcpy(B.getBufferStart(), &Header, HeaderSize);
}
void MachOWriter::writeLoadCommands() {
uint8_t *Begin = B.getBufferStart() + headerSize();
for (const LoadCommand &LC : O.LoadCommands) {
// Construct a load command.
MachO::macho_load_command MLC = LC.MachOLoadCommand;
switch (MLC.load_command_data.cmd) {
case MachO::LC_SEGMENT:
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(MLC.segment_command_data);
memcpy(Begin, &MLC.segment_command_data, sizeof(MachO::segment_command));
Begin += sizeof(MachO::segment_command);
for (const std::unique_ptr<Section> &Sec : LC.Sections)
writeSectionInLoadCommand<MachO::section>(*Sec, Begin);
continue;
case MachO::LC_SEGMENT_64:
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(MLC.segment_command_64_data);
memcpy(Begin, &MLC.segment_command_64_data,
sizeof(MachO::segment_command_64));
Begin += sizeof(MachO::segment_command_64);
for (const std::unique_ptr<Section> &Sec : LC.Sections)
writeSectionInLoadCommand<MachO::section_64>(*Sec, Begin);
continue;
}
#define HANDLE_LOAD_COMMAND(LCName, LCValue, LCStruct) \
case MachO::LCName: \
assert(sizeof(MachO::LCStruct) + LC.Payload.size() == \
MLC.load_command_data.cmdsize); \
if (IsLittleEndian != sys::IsLittleEndianHost) \
MachO::swapStruct(MLC.LCStruct##_data); \
memcpy(Begin, &MLC.LCStruct##_data, sizeof(MachO::LCStruct)); \
Begin += sizeof(MachO::LCStruct); \
if (!LC.Payload.empty()) \
memcpy(Begin, LC.Payload.data(), LC.Payload.size()); \
Begin += LC.Payload.size(); \
break;
// Copy the load command as it is.
switch (MLC.load_command_data.cmd) {
default:
assert(sizeof(MachO::load_command) + LC.Payload.size() ==
MLC.load_command_data.cmdsize);
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(MLC.load_command_data);
memcpy(Begin, &MLC.load_command_data, sizeof(MachO::load_command));
Begin += sizeof(MachO::load_command);
if (!LC.Payload.empty())
memcpy(Begin, LC.Payload.data(), LC.Payload.size());
Begin += LC.Payload.size();
break;
#include "llvm/BinaryFormat/MachO.def"
}
}
}
template <typename StructType>
void MachOWriter::writeSectionInLoadCommand(const Section &Sec, uint8_t *&Out) {
StructType Temp;
assert(Sec.Segname.size() <= sizeof(Temp.segname) && "too long segment name");
assert(Sec.Sectname.size() <= sizeof(Temp.sectname) &&
"too long section name");
memset(&Temp, 0, sizeof(StructType));
memcpy(Temp.segname, Sec.Segname.data(), Sec.Segname.size());
memcpy(Temp.sectname, Sec.Sectname.data(), Sec.Sectname.size());
Temp.addr = Sec.Addr;
Temp.size = Sec.Size;
Temp.offset = Sec.Offset;
Temp.align = Sec.Align;
Temp.reloff = Sec.RelOff;
Temp.nreloc = Sec.NReloc;
Temp.flags = Sec.Flags;
Temp.reserved1 = Sec.Reserved1;
Temp.reserved2 = Sec.Reserved2;
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(Temp);
memcpy(Out, &Temp, sizeof(StructType));
Out += sizeof(StructType);
}
void MachOWriter::writeSections() {
for (const LoadCommand &LC : O.LoadCommands)
for (const std::unique_ptr<Section> &Sec : LC.Sections) {
if (!Sec->hasValidOffset()) {
assert((Sec->Offset == 0) && "Skipped section's offset must be zero");
assert((Sec->isVirtualSection() || Sec->Size == 0) &&
"Non-zero-fill sections with zero offset must have zero size");
continue;
}
assert(Sec->Offset && "Section offset can not be zero");
assert((Sec->Size == Sec->Content.size()) && "Incorrect section size");
memcpy(B.getBufferStart() + Sec->Offset, Sec->Content.data(),
Sec->Content.size());
for (size_t Index = 0; Index < Sec->Relocations.size(); ++Index) {
RelocationInfo RelocInfo = Sec->Relocations[Index];
if (!RelocInfo.Scattered) {
const uint32_t SymbolNum = RelocInfo.Extern
? (*RelocInfo.Symbol)->Index
: (*RelocInfo.Sec)->Index;
RelocInfo.setPlainRelocationSymbolNum(SymbolNum, IsLittleEndian);
}
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(
reinterpret_cast<MachO::any_relocation_info &>(RelocInfo.Info));
memcpy(B.getBufferStart() + Sec->RelOff +
Index * sizeof(MachO::any_relocation_info),
&RelocInfo.Info, sizeof(RelocInfo.Info));
}
}
}
template <typename NListType>
void writeNListEntry(const SymbolEntry &SE, bool IsLittleEndian, char *&Out,
uint32_t Nstrx) {
NListType ListEntry;
ListEntry.n_strx = Nstrx;
ListEntry.n_type = SE.n_type;
ListEntry.n_sect = SE.n_sect;
ListEntry.n_desc = SE.n_desc;
ListEntry.n_value = SE.n_value;
if (IsLittleEndian != sys::IsLittleEndianHost)
MachO::swapStruct(ListEntry);
memcpy(Out, reinterpret_cast<const char *>(&ListEntry), sizeof(NListType));
Out += sizeof(NListType);
}
void MachOWriter::writeStringTable() {
if (!O.SymTabCommandIndex)
return;
const MachO::symtab_command &SymTabCommand =
O.LoadCommands[*O.SymTabCommandIndex]
.MachOLoadCommand.symtab_command_data;
uint8_t *StrTable = (uint8_t *)B.getBufferStart() + SymTabCommand.stroff;
LayoutBuilder.getStringTableBuilder().write(StrTable);
}
void MachOWriter::writeSymbolTable() {
if (!O.SymTabCommandIndex)
return;
const MachO::symtab_command &SymTabCommand =
O.LoadCommands[*O.SymTabCommandIndex]
.MachOLoadCommand.symtab_command_data;
char *SymTable = (char *)B.getBufferStart() + SymTabCommand.symoff;
for (auto Iter = O.SymTable.Symbols.begin(), End = O.SymTable.Symbols.end();
Iter != End; Iter++) {
SymbolEntry *Sym = Iter->get();
uint32_t Nstrx = LayoutBuilder.getStringTableBuilder().getOffset(Sym->Name);
if (Is64Bit)
writeNListEntry<MachO::nlist_64>(*Sym, IsLittleEndian, SymTable, Nstrx);
else
writeNListEntry<MachO::nlist>(*Sym, IsLittleEndian, SymTable, Nstrx);
}
}
void MachOWriter::writeRebaseInfo() {
if (!O.DyLdInfoCommandIndex)
return;
const MachO::dyld_info_command &DyLdInfoCommand =
O.LoadCommands[*O.DyLdInfoCommandIndex]
.MachOLoadCommand.dyld_info_command_data;
char *Out = (char *)B.getBufferStart() + DyLdInfoCommand.rebase_off;
assert((DyLdInfoCommand.rebase_size == O.Rebases.Opcodes.size()) &&
"Incorrect rebase opcodes size");
memcpy(Out, O.Rebases.Opcodes.data(), O.Rebases.Opcodes.size());
}
void MachOWriter::writeBindInfo() {
if (!O.DyLdInfoCommandIndex)
return;
const MachO::dyld_info_command &DyLdInfoCommand =
O.LoadCommands[*O.DyLdInfoCommandIndex]
.MachOLoadCommand.dyld_info_command_data;
char *Out = (char *)B.getBufferStart() + DyLdInfoCommand.bind_off;
assert((DyLdInfoCommand.bind_size == O.Binds.Opcodes.size()) &&
"Incorrect bind opcodes size");
memcpy(Out, O.Binds.Opcodes.data(), O.Binds.Opcodes.size());
}
void MachOWriter::writeWeakBindInfo() {
if (!O.DyLdInfoCommandIndex)
return;
const MachO::dyld_info_command &DyLdInfoCommand =
O.LoadCommands[*O.DyLdInfoCommandIndex]
.MachOLoadCommand.dyld_info_command_data;
char *Out = (char *)B.getBufferStart() + DyLdInfoCommand.weak_bind_off;
assert((DyLdInfoCommand.weak_bind_size == O.WeakBinds.Opcodes.size()) &&
"Incorrect weak bind opcodes size");
memcpy(Out, O.WeakBinds.Opcodes.data(), O.WeakBinds.Opcodes.size());
}
void MachOWriter::writeLazyBindInfo() {
if (!O.DyLdInfoCommandIndex)
return;
const MachO::dyld_info_command &DyLdInfoCommand =
O.LoadCommands[*O.DyLdInfoCommandIndex]
.MachOLoadCommand.dyld_info_command_data;
char *Out = (char *)B.getBufferStart() + DyLdInfoCommand.lazy_bind_off;
assert((DyLdInfoCommand.lazy_bind_size == O.LazyBinds.Opcodes.size()) &&
"Incorrect lazy bind opcodes size");
memcpy(Out, O.LazyBinds.Opcodes.data(), O.LazyBinds.Opcodes.size());
}
void MachOWriter::writeExportInfo() {
if (!O.DyLdInfoCommandIndex)
return;
const MachO::dyld_info_command &DyLdInfoCommand =
O.LoadCommands[*O.DyLdInfoCommandIndex]
.MachOLoadCommand.dyld_info_command_data;
char *Out = (char *)B.getBufferStart() + DyLdInfoCommand.export_off;
assert((DyLdInfoCommand.export_size == O.Exports.Trie.size()) &&
"Incorrect export trie size");
memcpy(Out, O.Exports.Trie.data(), O.Exports.Trie.size());
}
void MachOWriter::writeIndirectSymbolTable() {
if (!O.DySymTabCommandIndex)
return;
const MachO::dysymtab_command &DySymTabCommand =
O.LoadCommands[*O.DySymTabCommandIndex]
.MachOLoadCommand.dysymtab_command_data;
uint32_t *Out =
(uint32_t *)(B.getBufferStart() + DySymTabCommand.indirectsymoff);
for (const IndirectSymbolEntry &Sym : O.IndirectSymTable.Symbols) {
uint32_t Entry = (Sym.Symbol) ? (*Sym.Symbol)->Index : Sym.OriginalIndex;
if (IsLittleEndian != sys::IsLittleEndianHost)
sys::swapByteOrder(Entry);
*Out++ = Entry;
}
}
void MachOWriter::writeLinkData(Optional<size_t> LCIndex, const LinkData &LD) {
if (!LCIndex)
return;
const MachO::linkedit_data_command &LinkEditDataCommand =
O.LoadCommands[*LCIndex].MachOLoadCommand.linkedit_data_command_data;
char *Out = (char *)B.getBufferStart() + LinkEditDataCommand.dataoff;
assert((LinkEditDataCommand.datasize == LD.Data.size()) &&
"Incorrect data size");
memcpy(Out, LD.Data.data(), LD.Data.size());
}
void MachOWriter::writeCodeSignatureData() {
return writeLinkData(O.CodeSignatureCommandIndex, O.CodeSignature);
}
void MachOWriter::writeDataInCodeData() {
return writeLinkData(O.DataInCodeCommandIndex, O.DataInCode);
}
void MachOWriter::writeFunctionStartsData() {
return writeLinkData(O.FunctionStartsCommandIndex, O.FunctionStarts);
}
void MachOWriter::writeTail() {
typedef void (MachOWriter::*WriteHandlerType)(void);
typedef std::pair<uint64_t, WriteHandlerType> WriteOperation;
SmallVector<WriteOperation, 7> Queue;
if (O.SymTabCommandIndex) {
const MachO::symtab_command &SymTabCommand =
O.LoadCommands[*O.SymTabCommandIndex]
.MachOLoadCommand.symtab_command_data;
if (SymTabCommand.symoff)
Queue.push_back({SymTabCommand.symoff, &MachOWriter::writeSymbolTable});
if (SymTabCommand.stroff)
Queue.push_back({SymTabCommand.stroff, &MachOWriter::writeStringTable});
}
if (O.DyLdInfoCommandIndex) {
const MachO::dyld_info_command &DyLdInfoCommand =
O.LoadCommands[*O.DyLdInfoCommandIndex]
.MachOLoadCommand.dyld_info_command_data;
if (DyLdInfoCommand.rebase_off)
Queue.push_back(
{DyLdInfoCommand.rebase_off, &MachOWriter::writeRebaseInfo});
if (DyLdInfoCommand.bind_off)
Queue.push_back({DyLdInfoCommand.bind_off, &MachOWriter::writeBindInfo});
if (DyLdInfoCommand.weak_bind_off)
Queue.push_back(
{DyLdInfoCommand.weak_bind_off, &MachOWriter::writeWeakBindInfo});
if (DyLdInfoCommand.lazy_bind_off)
Queue.push_back(
{DyLdInfoCommand.lazy_bind_off, &MachOWriter::writeLazyBindInfo});
if (DyLdInfoCommand.export_off)
Queue.push_back(
{DyLdInfoCommand.export_off, &MachOWriter::writeExportInfo});
}
if (O.DySymTabCommandIndex) {
const MachO::dysymtab_command &DySymTabCommand =
O.LoadCommands[*O.DySymTabCommandIndex]
.MachOLoadCommand.dysymtab_command_data;
if (DySymTabCommand.indirectsymoff)
Queue.emplace_back(DySymTabCommand.indirectsymoff,
&MachOWriter::writeIndirectSymbolTable);
}
if (O.CodeSignatureCommandIndex) {
const MachO::linkedit_data_command &LinkEditDataCommand =
O.LoadCommands[*O.CodeSignatureCommandIndex]
.MachOLoadCommand.linkedit_data_command_data;
if (LinkEditDataCommand.dataoff)
Queue.emplace_back(LinkEditDataCommand.dataoff,
&MachOWriter::writeCodeSignatureData);
}
if (O.DataInCodeCommandIndex) {
const MachO::linkedit_data_command &LinkEditDataCommand =
O.LoadCommands[*O.DataInCodeCommandIndex]
.MachOLoadCommand.linkedit_data_command_data;
if (LinkEditDataCommand.dataoff)
Queue.emplace_back(LinkEditDataCommand.dataoff,
&MachOWriter::writeDataInCodeData);
}
if (O.FunctionStartsCommandIndex) {
const MachO::linkedit_data_command &LinkEditDataCommand =
O.LoadCommands[*O.FunctionStartsCommandIndex]
.MachOLoadCommand.linkedit_data_command_data;
if (LinkEditDataCommand.dataoff)
Queue.emplace_back(LinkEditDataCommand.dataoff,
&MachOWriter::writeFunctionStartsData);
}
llvm::sort(Queue, [](const WriteOperation &LHS, const WriteOperation &RHS) {
return LHS.first < RHS.first;
});
for (auto WriteOp : Queue)
(this->*WriteOp.second)();
}
Error MachOWriter::finalize() { return LayoutBuilder.layout(); }
Error MachOWriter::write() {
if (Error E = B.allocate(totalSize()))
return E;
memset(B.getBufferStart(), 0, totalSize());
writeHeader();
writeLoadCommands();
writeSections();
writeTail();
return B.commit();
}
} // end namespace macho
} // end namespace objcopy
} // end namespace llvm