llvm-project/lld/COFF/Chunks.cpp

353 lines
12 KiB
C++

//===- Chunks.cpp ---------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Chunks.h"
#include "Error.h"
#include "InputFiles.h"
#include "Symbols.h"
#include "llvm/Object/COFF.h"
#include "llvm/Support/COFF.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::COFF;
using llvm::support::ulittle32_t;
namespace lld {
namespace coff {
SectionChunk::SectionChunk(ObjectFile *F, const coff_section *H)
: Chunk(SectionKind), Repl(this), File(F), Header(H),
Relocs(File->getCOFFObj()->getRelocations(Header)),
NumRelocs(std::distance(Relocs.begin(), Relocs.end())) {
// Initialize SectionName.
File->getCOFFObj()->getSectionName(Header, SectionName);
Align = Header->getAlignment();
// Only COMDAT sections are subject of dead-stripping.
Live = !isCOMDAT();
}
static void add16(uint8_t *P, int16_t V) { write16le(P, read16le(P) + V); }
static void add32(uint8_t *P, int32_t V) { write32le(P, read32le(P) + V); }
static void add64(uint8_t *P, int64_t V) { write64le(P, read64le(P) + V); }
static void or16(uint8_t *P, uint16_t V) { write16le(P, read16le(P) | V); }
void SectionChunk::applyRelX64(uint8_t *Off, uint16_t Type, Defined *Sym,
uint64_t P) const {
uint64_t S = Sym->getRVA();
switch (Type) {
case IMAGE_REL_AMD64_ADDR32: add32(Off, S + Config->ImageBase); break;
case IMAGE_REL_AMD64_ADDR64: add64(Off, S + Config->ImageBase); break;
case IMAGE_REL_AMD64_ADDR32NB: add32(Off, S); break;
case IMAGE_REL_AMD64_REL32: add32(Off, S - P - 4); break;
case IMAGE_REL_AMD64_REL32_1: add32(Off, S - P - 5); break;
case IMAGE_REL_AMD64_REL32_2: add32(Off, S - P - 6); break;
case IMAGE_REL_AMD64_REL32_3: add32(Off, S - P - 7); break;
case IMAGE_REL_AMD64_REL32_4: add32(Off, S - P - 8); break;
case IMAGE_REL_AMD64_REL32_5: add32(Off, S - P - 9); break;
case IMAGE_REL_AMD64_SECTION: add16(Off, Sym->getSectionIndex()); break;
case IMAGE_REL_AMD64_SECREL: add32(Off, Sym->getSecrel()); break;
default:
fatal("unsupported relocation type");
}
}
void SectionChunk::applyRelX86(uint8_t *Off, uint16_t Type, Defined *Sym,
uint64_t P) const {
uint64_t S = Sym->getRVA();
switch (Type) {
case IMAGE_REL_I386_ABSOLUTE: break;
case IMAGE_REL_I386_DIR32: add32(Off, S + Config->ImageBase); break;
case IMAGE_REL_I386_DIR32NB: add32(Off, S); break;
case IMAGE_REL_I386_REL32: add32(Off, S - P - 4); break;
case IMAGE_REL_I386_SECTION: add16(Off, Sym->getSectionIndex()); break;
case IMAGE_REL_I386_SECREL: add32(Off, Sym->getSecrel()); break;
default:
fatal("unsupported relocation type");
}
}
static void applyMOV(uint8_t *Off, uint16_t V) {
write16le(Off, (read16le(Off) & 0xfbf0) | ((V & 0x800) >> 1) | ((V >> 12) & 0xf));
write16le(Off + 2, (read16le(Off + 2) & 0x8f00) | ((V & 0x700) << 4) | (V & 0xff));
}
static uint16_t readMOV(uint8_t *Off) {
uint16_t Opcode1 = read16le(Off);
uint16_t Opcode2 = read16le(Off + 2);
uint16_t Imm = (Opcode2 & 0x00ff) | ((Opcode2 >> 4) & 0x0700);
Imm |= ((Opcode1 << 1) & 0x0800) | ((Opcode1 & 0x000f) << 12);
return Imm;
}
static void applyMOV32T(uint8_t *Off, uint32_t V) {
uint16_t ImmW = readMOV(Off); // read MOVW operand
uint16_t ImmT = readMOV(Off + 4); // read MOVT operand
uint32_t Imm = ImmW | (ImmT << 16);
V += Imm; // add the immediate offset
applyMOV(Off, V); // set MOVW operand
applyMOV(Off + 4, V >> 16); // set MOVT operand
}
static void applyBranch20T(uint8_t *Off, int32_t V) {
uint32_t S = V < 0 ? 1 : 0;
uint32_t J1 = (V >> 19) & 1;
uint32_t J2 = (V >> 18) & 1;
or16(Off, (S << 10) | ((V >> 12) & 0x3f));
or16(Off + 2, (J1 << 13) | (J2 << 11) | ((V >> 1) & 0x7ff));
}
static void applyBranch24T(uint8_t *Off, int32_t V) {
if (!isInt<25>(V))
fatal("relocation out of range");
uint32_t S = V < 0 ? 1 : 0;
uint32_t J1 = ((~V >> 23) & 1) ^ S;
uint32_t J2 = ((~V >> 22) & 1) ^ S;
or16(Off, (S << 10) | ((V >> 12) & 0x3ff));
// Clear out the J1 and J2 bits which may be set.
write16le(Off + 2, (read16le(Off + 2) & 0xd000) | (J1 << 13) | (J2 << 11) | ((V >> 1) & 0x7ff));
}
void SectionChunk::applyRelARM(uint8_t *Off, uint16_t Type, Defined *Sym,
uint64_t P) const {
uint64_t S = Sym->getRVA();
// Pointer to thumb code must have the LSB set.
if (Sym->isExecutable())
S |= 1;
switch (Type) {
case IMAGE_REL_ARM_ADDR32: add32(Off, S + Config->ImageBase); break;
case IMAGE_REL_ARM_ADDR32NB: add32(Off, S); break;
case IMAGE_REL_ARM_MOV32T: applyMOV32T(Off, S + Config->ImageBase); break;
case IMAGE_REL_ARM_BRANCH20T: applyBranch20T(Off, S - P - 4); break;
case IMAGE_REL_ARM_BRANCH24T: applyBranch24T(Off, S - P - 4); break;
case IMAGE_REL_ARM_BLX23T: applyBranch24T(Off, S - P - 4); break;
default:
fatal("unsupported relocation type");
}
}
void SectionChunk::writeTo(uint8_t *Buf) const {
if (!hasData())
return;
// Copy section contents from source object file to output file.
ArrayRef<uint8_t> A = getContents();
memcpy(Buf + OutputSectionOff, A.data(), A.size());
// Apply relocations.
for (const coff_relocation &Rel : Relocs) {
uint8_t *Off = Buf + OutputSectionOff + Rel.VirtualAddress;
SymbolBody *Body = File->getSymbolBody(Rel.SymbolTableIndex)->repl();
Defined *Sym = cast<Defined>(Body);
uint64_t P = RVA + Rel.VirtualAddress;
switch (Config->Machine) {
case AMD64:
applyRelX64(Off, Rel.Type, Sym, P);
break;
case I386:
applyRelX86(Off, Rel.Type, Sym, P);
break;
case ARMNT:
applyRelARM(Off, Rel.Type, Sym, P);
break;
default:
llvm_unreachable("unknown machine type");
}
}
}
void SectionChunk::addAssociative(SectionChunk *Child) {
AssocChildren.push_back(Child);
}
static uint8_t getBaserelType(const coff_relocation &Rel) {
switch (Config->Machine) {
case AMD64:
if (Rel.Type == IMAGE_REL_AMD64_ADDR64)
return IMAGE_REL_BASED_DIR64;
return IMAGE_REL_BASED_ABSOLUTE;
case I386:
if (Rel.Type == IMAGE_REL_I386_DIR32)
return IMAGE_REL_BASED_HIGHLOW;
return IMAGE_REL_BASED_ABSOLUTE;
case ARMNT:
if (Rel.Type == IMAGE_REL_ARM_ADDR32)
return IMAGE_REL_BASED_HIGHLOW;
if (Rel.Type == IMAGE_REL_ARM_MOV32T)
return IMAGE_REL_BASED_ARM_MOV32T;
return IMAGE_REL_BASED_ABSOLUTE;
default:
llvm_unreachable("unknown machine type");
}
}
// Windows-specific.
// Collect all locations that contain absolute addresses, which need to be
// fixed by the loader if load-time relocation is needed.
// Only called when base relocation is enabled.
void SectionChunk::getBaserels(std::vector<Baserel> *Res) {
for (const coff_relocation &Rel : Relocs) {
uint8_t Ty = getBaserelType(Rel);
if (Ty == IMAGE_REL_BASED_ABSOLUTE)
continue;
SymbolBody *Body = File->getSymbolBody(Rel.SymbolTableIndex)->repl();
if (isa<DefinedAbsolute>(Body))
continue;
Res->emplace_back(RVA + Rel.VirtualAddress, Ty);
}
}
bool SectionChunk::hasData() const {
return !(Header->Characteristics & IMAGE_SCN_CNT_UNINITIALIZED_DATA);
}
uint32_t SectionChunk::getPermissions() const {
return Header->Characteristics & PermMask;
}
bool SectionChunk::isCOMDAT() const {
return Header->Characteristics & IMAGE_SCN_LNK_COMDAT;
}
void SectionChunk::printDiscardedMessage() const {
// Removed by dead-stripping. If it's removed by ICF, ICF already
// printed out the name, so don't repeat that here.
if (Sym && this == Repl)
llvm::outs() << "Discarded " << Sym->getName() << "\n";
}
StringRef SectionChunk::getDebugName() {
if (Sym)
return Sym->getName();
return "";
}
ArrayRef<uint8_t> SectionChunk::getContents() const {
ArrayRef<uint8_t> A;
File->getCOFFObj()->getSectionContents(Header, A);
return A;
}
void SectionChunk::replace(SectionChunk *Other) {
Other->Repl = Repl;
Other->Live = false;
}
CommonChunk::CommonChunk(const COFFSymbolRef S) : Sym(S) {
// Common symbols are aligned on natural boundaries up to 32 bytes.
// This is what MSVC link.exe does.
Align = std::min(uint64_t(32), NextPowerOf2(Sym.getValue()));
}
uint32_t CommonChunk::getPermissions() const {
return IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ |
IMAGE_SCN_MEM_WRITE;
}
void StringChunk::writeTo(uint8_t *Buf) const {
memcpy(Buf + OutputSectionOff, Str.data(), Str.size());
}
ImportThunkChunkX64::ImportThunkChunkX64(Defined *S) : ImpSymbol(S) {
// Intel Optimization Manual says that all branch targets
// should be 16-byte aligned. MSVC linker does this too.
Align = 16;
}
void ImportThunkChunkX64::writeTo(uint8_t *Buf) const {
memcpy(Buf + OutputSectionOff, ImportThunkX86, sizeof(ImportThunkX86));
// The first two bytes is a JMP instruction. Fill its operand.
write32le(Buf + OutputSectionOff + 2, ImpSymbol->getRVA() - RVA - getSize());
}
void ImportThunkChunkX86::getBaserels(std::vector<Baserel> *Res) {
Res->emplace_back(getRVA() + 2);
}
void ImportThunkChunkX86::writeTo(uint8_t *Buf) const {
memcpy(Buf + OutputSectionOff, ImportThunkX86, sizeof(ImportThunkX86));
// The first two bytes is a JMP instruction. Fill its operand.
write32le(Buf + OutputSectionOff + 2,
ImpSymbol->getRVA() + Config->ImageBase);
}
void ImportThunkChunkARM::getBaserels(std::vector<Baserel> *Res) {
Res->emplace_back(getRVA(), IMAGE_REL_BASED_ARM_MOV32T);
}
void ImportThunkChunkARM::writeTo(uint8_t *Buf) const {
memcpy(Buf + OutputSectionOff, ImportThunkARM, sizeof(ImportThunkARM));
// Fix mov.w and mov.t operands.
applyMOV32T(Buf + OutputSectionOff, ImpSymbol->getRVA() + Config->ImageBase);
}
void LocalImportChunk::getBaserels(std::vector<Baserel> *Res) {
Res->emplace_back(getRVA());
}
size_t LocalImportChunk::getSize() const {
return Config->is64() ? 8 : 4;
}
void LocalImportChunk::writeTo(uint8_t *Buf) const {
if (Config->is64()) {
write64le(Buf + OutputSectionOff, Sym->getRVA() + Config->ImageBase);
} else {
write32le(Buf + OutputSectionOff, Sym->getRVA() + Config->ImageBase);
}
}
void SEHTableChunk::writeTo(uint8_t *Buf) const {
ulittle32_t *Begin = reinterpret_cast<ulittle32_t *>(Buf + OutputSectionOff);
size_t Cnt = 0;
for (Defined *D : Syms)
Begin[Cnt++] = D->getRVA();
std::sort(Begin, Begin + Cnt);
}
// Windows-specific.
// This class represents a block in .reloc section.
BaserelChunk::BaserelChunk(uint32_t Page, Baserel *Begin, Baserel *End) {
// Block header consists of 4 byte page RVA and 4 byte block size.
// Each entry is 2 byte. Last entry may be padding.
Data.resize(alignTo((End - Begin) * 2 + 8, 4));
uint8_t *P = Data.data();
write32le(P, Page);
write32le(P + 4, Data.size());
P += 8;
for (Baserel *I = Begin; I != End; ++I) {
write16le(P, (I->Type << 12) | (I->RVA - Page));
P += 2;
}
}
void BaserelChunk::writeTo(uint8_t *Buf) const {
memcpy(Buf + OutputSectionOff, Data.data(), Data.size());
}
uint8_t Baserel::getDefaultType() {
switch (Config->Machine) {
case AMD64:
return IMAGE_REL_BASED_DIR64;
case I386:
return IMAGE_REL_BASED_HIGHLOW;
default:
llvm_unreachable("unknown machine type");
}
}
} // namespace coff
} // namespace lld