mirrors/llvm-project
0
0
Fork 0
mirror of https://github.com/llvm/llvm-project.git synced 2025-04-25 11:16:06 +00:00
Code Issues Projects Releases Wiki Activity
llvm-project/lld/COFF/Writer.cpp
Rui Ueyama d157088adb COFF: Fix the order of the DLL import entry. 
There are some DLLs whose initializers depends on other DLLs'
initializers. The initialization order matters for them.

MSVC linker uses the order of the libraries from the command line.
LLD used ASCII-betical order. So they were incompatible.
This patch makes LLD compatible with MSVC.

llvm-svn: 245201
2015-08-17 08:30:31 +00:00

820 lines
27 KiB
C++
Raw Blame History

//===- Writer.cpp ---------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Config.h"
#include "DLL.h"
#include "Error.h"
#include "InputFiles.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "Writer.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cstdio>
#include <map>
#include <memory>
#include <utility>
using namespace llvm;
using namespace llvm::COFF;
using namespace llvm::object;
using namespace llvm::support;
using namespace llvm::support::endian;
using namespace lld;
using namespace lld::coff;
static const int PageSize = 4096;
static const int SectorSize = 512;
static const int DOSStubSize = 64;
static const int NumberfOfDataDirectory = 16;
namespace {
// The writer writes a SymbolTable result to a file.
class Writer {
public:
Writer(SymbolTable *T) : Symtab(T) {}
void run();
private:
void markLive();
void dedupCOMDATs();
void createSections();
void createMiscChunks();
void createImportTables();
void createExportTable();
void assignAddresses();
void removeEmptySections();
void createSymbolAndStringTable();
void openFile(StringRef OutputPath);
template <typename PEHeaderTy> void writeHeader();
void fixSafeSEHSymbols();
void writeSections();
void sortExceptionTable();
void applyRelocations();
llvm::Optional<coff_symbol16> createSymbol(Defined *D);
size_t addEntryToStringTable(StringRef Str);
OutputSection *findSection(StringRef Name);
OutputSection *createSection(StringRef Name);
void addBaserels(OutputSection *Dest);
void addBaserelBlocks(OutputSection *Dest, std::vector<Baserel> &V);
uint32_t getSizeOfInitializedData();
std::map<StringRef, std::vector<DefinedImportData *>> binImports();
SymbolTable *Symtab;
std::unique_ptr<llvm::FileOutputBuffer> Buffer;
llvm::SpecificBumpPtrAllocator<OutputSection> CAlloc;
llvm::SpecificBumpPtrAllocator<BaserelChunk> BAlloc;
std::vector<OutputSection *> OutputSections;
std::vector<char> Strtab;
std::vector<llvm::object::coff_symbol16> OutputSymtab;
IdataContents Idata;
DelayLoadContents DelayIdata;
EdataContents Edata;
std::unique_ptr<SEHTableChunk> SEHTable;
uint64_t FileSize;
uint32_t PointerToSymbolTable = 0;
uint64_t SizeOfImage;
uint64_t SizeOfHeaders;
std::vector<std::unique_ptr<Chunk>> Chunks;
};
} // anonymous namespace
namespace lld {
namespace coff {
void writeResult(SymbolTable *T) { Writer(T).run(); }
// OutputSection represents a section in an output file. It's a
// container of chunks. OutputSection and Chunk are 1:N relationship.
// Chunks cannot belong to more than one OutputSections. The writer
// creates multiple OutputSections and assign them unique,
// non-overlapping file offsets and RVAs.
class OutputSection {
public:
OutputSection(StringRef N) : Name(N), Header({}) {}
void setRVA(uint64_t);
void setFileOffset(uint64_t);
void addChunk(Chunk *C);
StringRef getName() { return Name; }
std::vector<Chunk *> &getChunks() { return Chunks; }
void addPermissions(uint32_t C);
uint32_t getPermissions() { return Header.Characteristics & PermMask; }
uint32_t getCharacteristics() { return Header.Characteristics; }
uint64_t getRVA() { return Header.VirtualAddress; }
uint64_t getFileOff() { return Header.PointerToRawData; }
void writeHeaderTo(uint8_t *Buf);
// Returns the size of this section in an executable memory image.
// This may be smaller than the raw size (the raw size is multiple
// of disk sector size, so there may be padding at end), or may be
// larger (if that's the case, the loader reserves spaces after end
// of raw data).
uint64_t getVirtualSize() { return Header.VirtualSize; }
// Returns the size of the section in the output file.
uint64_t getRawSize() { return Header.SizeOfRawData; }
// Set offset into the string table storing this section name.
// Used only when the name is longer than 8 bytes.
void setStringTableOff(uint32_t V) { StringTableOff = V; }
// N.B. The section index is one based.
uint32_t SectionIndex = 0;
private:
StringRef Name;
coff_section Header;
uint32_t StringTableOff = 0;
std::vector<Chunk *> Chunks;
};
void OutputSection::setRVA(uint64_t RVA) {
Header.VirtualAddress = RVA;
for (Chunk *C : Chunks)
C->setRVA(C->getRVA() + RVA);
}
void OutputSection::setFileOffset(uint64_t Off) {
// If a section has no actual data (i.e. BSS section), we want to
// set 0 to its PointerToRawData. Otherwise the output is rejected
// by the loader.
if (Header.SizeOfRawData == 0)
return;
Header.PointerToRawData = Off;
}
void OutputSection::addChunk(Chunk *C) {
Chunks.push_back(C);
C->setOutputSection(this);
uint64_t Off = Header.VirtualSize;
Off = RoundUpToAlignment(Off, C->getAlign());
C->setRVA(Off);
C->setOutputSectionOff(Off);
Off += C->getSize();
Header.VirtualSize = Off;
if (C->hasData())
Header.SizeOfRawData = RoundUpToAlignment(Off, SectorSize);
}
void OutputSection::addPermissions(uint32_t C) {
Header.Characteristics |= C & PermMask;
}
// Write the section header to a given buffer.
void OutputSection::writeHeaderTo(uint8_t *Buf) {
auto *Hdr = reinterpret_cast<coff_section *>(Buf);
*Hdr = Header;
if (StringTableOff) {
// If name is too long, write offset into the string table as a name.
sprintf(Hdr->Name, "/%d", StringTableOff);
} else {
assert(!Config->Debug || Name.size() <= COFF::NameSize);
strncpy(Hdr->Name, Name.data(),
std::min(Name.size(), (size_t)COFF::NameSize));
}
}
uint64_t Defined::getSecrel() {
if (auto *D = dyn_cast<DefinedRegular>(this))
return getRVA() - D->getChunk()->getOutputSection()->getRVA();
error("SECREL relocation points to a non-regular symbol");
}
uint64_t Defined::getSectionIndex() {
if (auto *D = dyn_cast<DefinedRegular>(this))
return D->getChunk()->getOutputSection()->SectionIndex;
error("SECTION relocation points to a non-regular symbol");
}
bool Defined::isExecutable() {
const auto X = IMAGE_SCN_MEM_EXECUTE;
if (auto *D = dyn_cast<DefinedRegular>(this))
return D->getChunk()->getOutputSection()->getPermissions() & X;
return isa<DefinedImportThunk>(this);
}
} // namespace coff
} // namespace lld
// The main function of the writer.
void Writer::run() {
markLive();
dedupCOMDATs();
createSections();
createMiscChunks();
createImportTables();
createExportTable();
if (Config->Relocatable)
createSection(".reloc");
assignAddresses();
removeEmptySections();
createSymbolAndStringTable();
openFile(Config->OutputFile);
if (Config->is64()) {
writeHeader<pe32plus_header>();
} else {
writeHeader<pe32_header>();
}
fixSafeSEHSymbols();
writeSections();
sortExceptionTable();
error(Buffer->commit(), "Failed to write the output file");
}
// Set live bit on for each reachable chunk. Unmarked (unreachable)
// COMDAT chunks will be ignored in the next step, so that they don't
// come to the final output file.
void Writer::markLive() {
if (!Config->DoGC)
return;
// We build up a worklist of sections which have been marked as live. We only
// push into the worklist when we discover an unmarked section, and we mark
// as we push, so sections never appear twice in the list.
SmallVector<SectionChunk *, 256> Worklist;
for (Undefined *U : Config->GCRoot) {
auto *D = dyn_cast<DefinedRegular>(U->repl());
if (!D || D->isLive())
continue;
D->markLive();
Worklist.push_back(D->getChunk());
}
for (Chunk *C : Symtab->getChunks()) {
auto *SC = dyn_cast<SectionChunk>(C);
if (!SC || SC->isCOMDAT() || SC->isLive())
continue;
SC->markLive();
Worklist.push_back(SC);
}
while (!Worklist.empty()) {
SectionChunk *SC = Worklist.pop_back_val();
assert(SC->isLive() && "We mark as live when pushing onto the worklist!");
// Mark all symbols listed in the relocation table for this section.
for (SymbolBody *S : SC->symbols())
if (auto *D = dyn_cast<DefinedRegular>(S->repl()))
if (!D->isLive()) {
D->markLive();
Worklist.push_back(D->getChunk());
}
// Mark associative sections if any.
for (SectionChunk *ChildSC : SC->children())
if (!ChildSC->isLive()) {
ChildSC->markLive();
Worklist.push_back(ChildSC);
}
}
}
// Merge identical COMDAT sections.
void Writer::dedupCOMDATs() {
if (Config->ICF)
doICF(Symtab->getChunks());
}
static StringRef getOutputSection(StringRef Name) {
StringRef S = Name.split('$').first;
auto It = Config->Merge.find(S);
if (It == Config->Merge.end())
return S;
return It->second;
}
// Create output section objects and add them to OutputSections.
void Writer::createSections() {
// First, bin chunks by name.
std::map<StringRef, std::vector<Chunk *>> Map;
for (Chunk *C : Symtab->getChunks()) {
if (Config->DoGC) {
auto *SC = dyn_cast<SectionChunk>(C);
if (SC && !SC->isLive()) {
if (Config->Verbose)
SC->printDiscardedMessage();
continue;
}
}
Map[C->getSectionName()].push_back(C);
}
// Then create an OutputSection for each section.
// '$' and all following characters in input section names are
// discarded when determining output section. So, .text$foo
// contributes to .text, for example. See PE/COFF spec 3.2.
SmallDenseMap<StringRef, OutputSection *> Sections;
for (auto Pair : Map) {
StringRef Name = getOutputSection(Pair.first);
OutputSection *&Sec = Sections[Name];
if (!Sec) {
Sec = new (CAlloc.Allocate()) OutputSection(Name);
OutputSections.push_back(Sec);
}
std::vector<Chunk *> &Chunks = Pair.second;
for (Chunk *C : Chunks) {
Sec->addChunk(C);
Sec->addPermissions(C->getPermissions());
}
}
}
void Writer::createMiscChunks() {
// Create thunks for locally-dllimported symbols.
if (!Symtab->LocalImportChunks.empty()) {
OutputSection *Sec = createSection(".rdata");
for (Chunk *C : Symtab->LocalImportChunks)
Sec->addChunk(C);
}
// Create SEH table. x86-only.
if (Config->Machine != I386)
return;
std::set<Defined *> Handlers;
for (lld::coff::ObjectFile *File : Symtab->ObjectFiles) {
if (!File->SEHCompat)
return;
for (SymbolBody *B : File->SEHandlers)
Handlers.insert(cast<Defined>(B->repl()));
}
SEHTable.reset(new SEHTableChunk(Handlers));
createSection(".rdata")->addChunk(SEHTable.get());
}
// Create .idata section for the DLL-imported symbol table.
// The format of this section is inherently Windows-specific.
// IdataContents class abstracted away the details for us,
// so we just let it create chunks and add them to the section.
void Writer::createImportTables() {
if (Symtab->ImportFiles.empty())
return;
// Initialize DLLOrder so that import entries are ordered in
// the same order as in the command line. (That affects DLL
// initialization order, and this ordering is MSVC-compatible.)
for (ImportFile *File : Symtab->ImportFiles)
if (Config->DLLOrder.count(File->DLLName) == 0)
Config->DLLOrder[File->DLLName] = Config->DLLOrder.size();
OutputSection *Text = createSection(".text");
for (ImportFile *File : Symtab->ImportFiles) {
if (DefinedImportThunk *Thunk = File->ThunkSym)
Text->addChunk(Thunk->getChunk());
if (Config->DelayLoads.count(File->DLLName)) {
DelayIdata.add(File->ImpSym);
} else {
Idata.add(File->ImpSym);
}
}
if (!Idata.empty()) {
OutputSection *Sec = createSection(".idata");
for (Chunk *C : Idata.getChunks())
Sec->addChunk(C);
}
if (!DelayIdata.empty()) {
Defined *Helper = cast<Defined>(Config->DelayLoadHelper->repl());
DelayIdata.create(Helper);
OutputSection *Sec = createSection(".didat");
for (Chunk *C : DelayIdata.getChunks())
Sec->addChunk(C);
Sec = createSection(".data");
for (Chunk *C : DelayIdata.getDataChunks())
Sec->addChunk(C);
Sec = createSection(".text");
for (std::unique_ptr<Chunk> &C : DelayIdata.getCodeChunks())
Sec->addChunk(C.get());
}
}
void Writer::createExportTable() {
if (Config->Exports.empty())
return;
OutputSection *Sec = createSection(".edata");
for (std::unique_ptr<Chunk> &C : Edata.Chunks)
Sec->addChunk(C.get());
}
// The Windows loader doesn't seem to like empty sections,
// so we remove them if any.
void Writer::removeEmptySections() {
auto IsEmpty = [](OutputSection *S) { return S->getVirtualSize() == 0; };
OutputSections.erase(
std::remove_if(OutputSections.begin(), OutputSections.end(), IsEmpty),
OutputSections.end());
uint32_t Idx = 1;
for (OutputSection *Sec : OutputSections)
Sec->SectionIndex = Idx++;
}
size_t Writer::addEntryToStringTable(StringRef Str) {
assert(Str.size() > COFF::NameSize);
size_t OffsetOfEntry = Strtab.size() + 4; // +4 for the size field
Strtab.insert(Strtab.end(), Str.begin(), Str.end());
Strtab.push_back('\0');
return OffsetOfEntry;
}
Optional<coff_symbol16> Writer::createSymbol(Defined *Def) {
if (auto *D = dyn_cast<DefinedRegular>(Def))
if (!D->isLive())
return None;
coff_symbol16 Sym;
StringRef Name = Def->getName();
if (Name.size() > COFF::NameSize) {
Sym.Name.Offset.Zeroes = 0;
Sym.Name.Offset.Offset = addEntryToStringTable(Name);
} else {
memset(Sym.Name.ShortName, 0, COFF::NameSize);
memcpy(Sym.Name.ShortName, Name.data(), Name.size());
}
if (auto *D = dyn_cast<DefinedCOFF>(Def)) {
COFFSymbolRef Ref = D->getCOFFSymbol();
Sym.Type = Ref.getType();
Sym.StorageClass = Ref.getStorageClass();
} else {
Sym.Type = IMAGE_SYM_TYPE_NULL;
Sym.StorageClass = IMAGE_SYM_CLASS_EXTERNAL;
}
Sym.NumberOfAuxSymbols = 0;
switch (Def->kind()) {
case SymbolBody::DefinedAbsoluteKind:
case SymbolBody::DefinedRelativeKind:
Sym.Value = Def->getRVA();
Sym.SectionNumber = IMAGE_SYM_ABSOLUTE;
break;
default: {
uint64_t RVA = Def->getRVA();
OutputSection *Sec = nullptr;
for (OutputSection *S : OutputSections) {
if (S->getRVA() > RVA)
break;
Sec = S;
}
Sym.Value = RVA - Sec->getRVA();
Sym.SectionNumber = Sec->SectionIndex;
break;
}
}
return Sym;
}
void Writer::createSymbolAndStringTable() {
if (!Config->Debug)
return;
// Name field in the section table is 8 byte long. Longer names need
// to be written to the string table. First, construct string table.
for (OutputSection *Sec : OutputSections) {
StringRef Name = Sec->getName();
if (Name.size() <= COFF::NameSize)
continue;
Sec->setStringTableOff(addEntryToStringTable(Name));
}
for (lld::coff::ObjectFile *File : Symtab->ObjectFiles)
for (SymbolBody *B : File->getSymbols())
if (auto *D = dyn_cast<Defined>(B))
if (Optional<coff_symbol16> Sym = createSymbol(D))
OutputSymtab.push_back(*Sym);
for (ImportFile *File : Symtab->ImportFiles)
for (SymbolBody *B : File->getSymbols())
if (Optional<coff_symbol16> Sym = createSymbol(cast<Defined>(B)))
OutputSymtab.push_back(*Sym);
OutputSection *LastSection = OutputSections.back();
// We position the symbol table to be adjacent to the end of the last section.
uint64_t FileOff =
LastSection->getFileOff() +
RoundUpToAlignment(LastSection->getRawSize(), SectorSize);
if (!OutputSymtab.empty()) {
PointerToSymbolTable = FileOff;
FileOff += OutputSymtab.size() * sizeof(coff_symbol16);
}
if (!Strtab.empty())
FileOff += Strtab.size() + 4;
FileSize = RoundUpToAlignment(FileOff, SectorSize);
}
// Visits all sections to assign incremental, non-overlapping RVAs and
// file offsets.
void Writer::assignAddresses() {
SizeOfHeaders = DOSStubSize + sizeof(PEMagic) + sizeof(coff_file_header) +
sizeof(data_directory) * NumberfOfDataDirectory +
sizeof(coff_section) * OutputSections.size();
SizeOfHeaders +=
Config->is64() ? sizeof(pe32plus_header) : sizeof(pe32_header);
SizeOfHeaders = RoundUpToAlignment(SizeOfHeaders, SectorSize);
uint64_t RVA = 0x1000; // The first page is kept unmapped.
FileSize = SizeOfHeaders;
// Move DISCARDABLE (or non-memory-mapped) sections to the end of file because
// the loader cannot handle holes.
std::stable_partition(
OutputSections.begin(), OutputSections.end(), [](OutputSection *S) {
return (S->getPermissions() & IMAGE_SCN_MEM_DISCARDABLE) == 0;
});
for (OutputSection *Sec : OutputSections) {
if (Sec->getName() == ".reloc")
addBaserels(Sec);
Sec->setRVA(RVA);
Sec->setFileOffset(FileSize);
RVA += RoundUpToAlignment(Sec->getVirtualSize(), PageSize);
FileSize += RoundUpToAlignment(Sec->getRawSize(), SectorSize);
}
SizeOfImage = SizeOfHeaders + RoundUpToAlignment(RVA - 0x1000, PageSize);
}
template <typename PEHeaderTy> void Writer::writeHeader() {
// Write DOS stub
uint8_t *Buf = Buffer->getBufferStart();
auto *DOS = reinterpret_cast<dos_header *>(Buf);
Buf += DOSStubSize;
DOS->Magic[0] = 'M';
DOS->Magic[1] = 'Z';
DOS->AddressOfRelocationTable = sizeof(dos_header);
DOS->AddressOfNewExeHeader = DOSStubSize;
// Write PE magic
memcpy(Buf, PEMagic, sizeof(PEMagic));
Buf += sizeof(PEMagic);
// Write COFF header
auto *COFF = reinterpret_cast<coff_file_header *>(Buf);
Buf += sizeof(*COFF);
COFF->Machine = Config->Machine;
COFF->NumberOfSections = OutputSections.size();
COFF->Characteristics = IMAGE_FILE_EXECUTABLE_IMAGE;
if (Config->LargeAddressAware)
COFF->Characteristics |= IMAGE_FILE_LARGE_ADDRESS_AWARE;
if (!Config->is64())
COFF->Characteristics |= IMAGE_FILE_32BIT_MACHINE;
if (Config->DLL)
COFF->Characteristics |= IMAGE_FILE_DLL;
if (!Config->Relocatable)
COFF->Characteristics |= IMAGE_FILE_RELOCS_STRIPPED;
COFF->SizeOfOptionalHeader =
sizeof(PEHeaderTy) + sizeof(data_directory) * NumberfOfDataDirectory;
// Write PE header
auto *PE = reinterpret_cast<PEHeaderTy *>(Buf);
Buf += sizeof(*PE);
PE->Magic = Config->is64() ? PE32Header::PE32_PLUS : PE32Header::PE32;
PE->ImageBase = Config->ImageBase;
PE->SectionAlignment = PageSize;
PE->FileAlignment = SectorSize;
PE->MajorImageVersion = Config->MajorImageVersion;
PE->MinorImageVersion = Config->MinorImageVersion;
PE->MajorOperatingSystemVersion = Config->MajorOSVersion;
PE->MinorOperatingSystemVersion = Config->MinorOSVersion;
PE->MajorSubsystemVersion = Config->MajorOSVersion;
PE->MinorSubsystemVersion = Config->MinorOSVersion;
PE->Subsystem = Config->Subsystem;
PE->SizeOfImage = SizeOfImage;
PE->SizeOfHeaders = SizeOfHeaders;
if (!Config->NoEntry) {
Defined *Entry = cast<Defined>(Config->Entry->repl());
PE->AddressOfEntryPoint = Entry->getRVA();
// Pointer to thumb code must have the LSB set, so adjust it.
if (Config->Machine == ARMNT)
PE->AddressOfEntryPoint |= 1;
}
PE->SizeOfStackReserve = Config->StackReserve;
PE->SizeOfStackCommit = Config->StackCommit;
PE->SizeOfHeapReserve = Config->HeapReserve;
PE->SizeOfHeapCommit = Config->HeapCommit;
if (Config->DynamicBase)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_DYNAMIC_BASE;
if (Config->HighEntropyVA)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_HIGH_ENTROPY_VA;
if (!Config->AllowBind)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NO_BIND;
if (Config->NxCompat)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NX_COMPAT;
if (!Config->AllowIsolation)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_NO_ISOLATION;
if (Config->TerminalServerAware)
PE->DLLCharacteristics |= IMAGE_DLL_CHARACTERISTICS_TERMINAL_SERVER_AWARE;
PE->NumberOfRvaAndSize = NumberfOfDataDirectory;
if (OutputSection *Text = findSection(".text")) {
PE->BaseOfCode = Text->getRVA();
PE->SizeOfCode = Text->getRawSize();
}
PE->SizeOfInitializedData = getSizeOfInitializedData();
// Write data directory
auto *Dir = reinterpret_cast<data_directory *>(Buf);
Buf += sizeof(*Dir) * NumberfOfDataDirectory;
if (OutputSection *Sec = findSection(".edata")) {
Dir[EXPORT_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[EXPORT_TABLE].Size = Sec->getVirtualSize();
}
if (!Idata.empty()) {
Dir[IMPORT_TABLE].RelativeVirtualAddress = Idata.getDirRVA();
Dir[IMPORT_TABLE].Size = Idata.getDirSize();
Dir[IAT].RelativeVirtualAddress = Idata.getIATRVA();
Dir[IAT].Size = Idata.getIATSize();
}
if (!DelayIdata.empty()) {
Dir[DELAY_IMPORT_DESCRIPTOR].RelativeVirtualAddress =
DelayIdata.getDirRVA();
Dir[DELAY_IMPORT_DESCRIPTOR].Size = DelayIdata.getDirSize();
}
if (OutputSection *Sec = findSection(".rsrc")) {
Dir[RESOURCE_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[RESOURCE_TABLE].Size = Sec->getVirtualSize();
}
if (OutputSection *Sec = findSection(".reloc")) {
Dir[BASE_RELOCATION_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[BASE_RELOCATION_TABLE].Size = Sec->getVirtualSize();
}
if (OutputSection *Sec = findSection(".pdata")) {
Dir[EXCEPTION_TABLE].RelativeVirtualAddress = Sec->getRVA();
Dir[EXCEPTION_TABLE].Size = Sec->getVirtualSize();
}
if (Symbol *Sym = Symtab->findUnderscore("_tls_used")) {
if (Defined *B = dyn_cast<Defined>(Sym->Body)) {
Dir[TLS_TABLE].RelativeVirtualAddress = B->getRVA();
Dir[TLS_TABLE].Size = 40;
}
}
if (Symbol *Sym = Symtab->findUnderscore("_load_config_used")) {
if (Defined *B = dyn_cast<Defined>(Sym->Body)) {
Dir[LOAD_CONFIG_TABLE].RelativeVirtualAddress = B->getRVA();
Dir[LOAD_CONFIG_TABLE].Size = Config->is64() ? 112 : 64;
}
}
// Write section table
for (OutputSection *Sec : OutputSections) {
Sec->writeHeaderTo(Buf);
Buf += sizeof(coff_section);
}
if (OutputSymtab.empty())
return;
COFF->PointerToSymbolTable = PointerToSymbolTable;
uint32_t NumberOfSymbols = OutputSymtab.size();
COFF->NumberOfSymbols = NumberOfSymbols;
auto *SymbolTable = reinterpret_cast<coff_symbol16 *>(
Buffer->getBufferStart() + COFF->PointerToSymbolTable);
for (size_t I = 0; I != NumberOfSymbols; ++I)
SymbolTable[I] = OutputSymtab[I];
// Create the string table, it follows immediately after the symbol table.
// The first 4 bytes is length including itself.
Buf = reinterpret_cast<uint8_t *>(&SymbolTable[NumberOfSymbols]);
write32le(Buf, Strtab.size() + 4);
memcpy(Buf + 4, Strtab.data(), Strtab.size());
}
void Writer::openFile(StringRef Path) {
ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
FileOutputBuffer::create(Path, FileSize, FileOutputBuffer::F_executable);
error(BufferOrErr, Twine("failed to open ") + Path);
Buffer = std::move(*BufferOrErr);
}
void Writer::fixSafeSEHSymbols() {
if (!SEHTable)
return;
Config->SEHTable->setRVA(SEHTable->getRVA());
Config->SEHCount->setVA(SEHTable->getSize() / 4);
}
// Write section contents to a mmap'ed file.
void Writer::writeSections() {
uint8_t *Buf = Buffer->getBufferStart();
for (OutputSection *Sec : OutputSections) {
uint8_t *SecBuf = Buf + Sec->getFileOff();
// Fill gaps between functions in .text with INT3 instructions
// instead of leaving as NUL bytes (which can be interpreted as
// ADD instructions).
if (Sec->getPermissions() & IMAGE_SCN_CNT_CODE)
memset(SecBuf, 0xCC, Sec->getRawSize());
for (Chunk *C : Sec->getChunks())
C->writeTo(SecBuf);
}
}
// Sort .pdata section contents according to PE/COFF spec 5.5.
void Writer::sortExceptionTable() {
OutputSection *Sec = findSection(".pdata");
if (!Sec)
return;
// We assume .pdata contains function table entries only.
uint8_t *Begin = Buffer->getBufferStart() + Sec->getFileOff();
uint8_t *End = Begin + Sec->getVirtualSize();
if (Config->Machine == AMD64) {
struct Entry { ulittle32_t Begin, End, Unwind; };
std::sort((Entry *)Begin, (Entry *)End,
[](const Entry &A, const Entry &B) { return A.Begin < B.Begin; });
return;
}
if (Config->Machine == ARMNT) {
struct Entry { ulittle32_t Begin, Unwind; };
std::sort((Entry *)Begin, (Entry *)End,
[](const Entry &A, const Entry &B) { return A.Begin < B.Begin; });
return;
}
errs() << "warning: don't know how to handle .pdata.\n";
}
OutputSection *Writer::findSection(StringRef Name) {
for (OutputSection *Sec : OutputSections)
if (Sec->getName() == Name)
return Sec;
return nullptr;
}
uint32_t Writer::getSizeOfInitializedData() {
uint32_t Res = 0;
for (OutputSection *S : OutputSections)
if (S->getPermissions() & IMAGE_SCN_CNT_INITIALIZED_DATA)
Res += S->getRawSize();
return Res;
}
// Returns an existing section or create a new one if not found.
OutputSection *Writer::createSection(StringRef Name) {
if (auto *Sec = findSection(Name))
return Sec;
const auto DATA = IMAGE_SCN_CNT_INITIALIZED_DATA;
const auto BSS = IMAGE_SCN_CNT_UNINITIALIZED_DATA;
const auto CODE = IMAGE_SCN_CNT_CODE;
const auto DISCARDABLE = IMAGE_SCN_MEM_DISCARDABLE;
const auto R = IMAGE_SCN_MEM_READ;
const auto W = IMAGE_SCN_MEM_WRITE;
const auto X = IMAGE_SCN_MEM_EXECUTE;
uint32_t Perms = StringSwitch<uint32_t>(Name)
.Case(".bss", BSS | R | W)
.Case(".data", DATA | R | W)
.Case(".didat", DATA | R)
.Case(".edata", DATA | R)
.Case(".idata", DATA | R)
.Case(".rdata", DATA | R)
.Case(".reloc", DATA | DISCARDABLE | R)
.Case(".text", CODE | R | X)
.Default(0);
if (!Perms)
llvm_unreachable("unknown section name");
auto Sec = new (CAlloc.Allocate()) OutputSection(Name);
Sec->addPermissions(Perms);
OutputSections.push_back(Sec);
return Sec;
}
// Dest is .reloc section. Add contents to that section.
void Writer::addBaserels(OutputSection *Dest) {
std::vector<Baserel> V;
for (OutputSection *Sec : OutputSections) {
if (Sec == Dest)
continue;
// Collect all locations for base relocations.
for (Chunk *C : Sec->getChunks())
C->getBaserels(&V);
// Add the addresses to .reloc section.
if (!V.empty())
addBaserelBlocks(Dest, V);
V.clear();
}
}
// Add addresses to .reloc section. Note that addresses are grouped by page.
void Writer::addBaserelBlocks(OutputSection *Dest, std::vector<Baserel> &V) {
const uint32_t Mask = ~uint32_t(PageSize - 1);
uint32_t Page = V[0].RVA & Mask;
size_t I = 0, J = 1;
for (size_t E = V.size(); J < E; ++J) {
uint32_t P = V[J].RVA & Mask;
if (P == Page)
continue;
BaserelChunk *Buf = BAlloc.Allocate();
Dest->addChunk(new (Buf) BaserelChunk(Page, &V[I], &V[0] + J));
I = J;
Page = P;
}
if (I == J)
return;
BaserelChunk *Buf = BAlloc.Allocate();
Dest->addChunk(new (Buf) BaserelChunk(Page, &V[I], &V[0] + J));
}
Reference in New Issue View Git Blame Copy Permalink