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llvm-project/lld/ELF/InputSection.cpp

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//===- InputSection.cpp ---------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "InputSection.h"
#include "Config.h"
#include "Error.h"
#include "InputFiles.h"
#include "OutputSections.h"
#include "Target.h"
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace lld;
using namespace lld::elf2;
template <class ELFT>
InputSectionBase<ELFT>::InputSectionBase(ObjectFile<ELFT> *File,
const Elf_Shdr *Header,
Kind SectionKind)
: Header(Header), File(File), SectionKind(SectionKind) {}
template <class ELFT> StringRef InputSectionBase<ELFT>::getSectionName() const {
ErrorOr<StringRef> Name = File->getObj().getSectionName(this->Header);
error(Name);
return *Name;
}
template <class ELFT>
ArrayRef<uint8_t> InputSectionBase<ELFT>::getSectionData() const {
ErrorOr<ArrayRef<uint8_t>> Ret =
this->File->getObj().getSectionContents(this->Header);
error(Ret);
return *Ret;
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t
InputSectionBase<ELFT>::getOffset(uintX_t Offset) {
switch (SectionKind) {
case Regular:
return cast<InputSection<ELFT>>(this)->OutSecOff + Offset;
case EHFrame:
return cast<EHInputSection<ELFT>>(this)->getOffset(Offset);
case Merge:
return cast<MergeInputSection<ELFT>>(this)->getOffset(Offset);
}
llvm_unreachable("Invalid section kind");
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t
InputSectionBase<ELFT>::getOffset(const Elf_Sym &Sym) {
return getOffset(Sym.st_value);
}
// Returns a section that Rel relocation is pointing to.
template <class ELFT>
InputSectionBase<ELFT> *
InputSectionBase<ELFT>::getRelocTarget(const Elf_Rel &Rel) {
// Global symbol
uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
if (SymbolBody *B = File->getSymbolBody(SymIndex))
if (auto *D = dyn_cast<DefinedRegular<ELFT>>(B->repl()))
return &D->Section;
// Local symbol
if (const Elf_Sym *Sym = File->getLocalSymbol(SymIndex))
if (InputSectionBase<ELFT> *Sec = File->getSection(*Sym))
return Sec;
return nullptr;
}
template <class ELFT>
InputSectionBase<ELFT> *
InputSectionBase<ELFT>::getRelocTarget(const Elf_Rela &Rel) {
return getRelocTarget(reinterpret_cast<const Elf_Rel &>(Rel));
}
template <class ELFT>
InputSection<ELFT>::InputSection(ObjectFile<ELFT> *F, const Elf_Shdr *Header)
: InputSectionBase<ELFT>(F, Header, Base::Regular) {}
template <class ELFT>
bool InputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
return S->SectionKind == Base::Regular;
}
template <class ELFT>
template <bool isRela>
uint8_t *
InputSectionBase<ELFT>::findMipsPairedReloc(uint8_t *Buf, uint32_t SymIndex,
uint32_t Type,
RelIteratorRange<isRela> Rels) {
// Some MIPS relocations use addend calculated from addend of the relocation
// itself and addend of paired relocation. ABI requires to compute such
// combined addend in case of REL relocation record format only.
// See p. 4-17 at ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
if (isRela || Config->EMachine != EM_MIPS)
return nullptr;
if (Type == R_MIPS_HI16)
Type = R_MIPS_LO16;
else if (Type == R_MIPS_PCHI16)
Type = R_MIPS_PCLO16;
else if (Type == R_MICROMIPS_HI16)
Type = R_MICROMIPS_LO16;
else
return nullptr;
for (const auto &RI : Rels) {
if (RI.getType(Config->Mips64EL) != Type)
continue;
if (RI.getSymbol(Config->Mips64EL) != SymIndex)
continue;
uintX_t Offset = getOffset(RI.r_offset);
if (Offset == (uintX_t)-1)
return nullptr;
return Buf + Offset;
}
return nullptr;
}
template <class ELFT>
static typename llvm::object::ELFFile<ELFT>::uintX_t
getSymSize(SymbolBody &Body) {
if (auto *SS = dyn_cast<Defined<ELFT>>(&Body))
return SS->Sym.st_size;
return 0;
}
template <class ELFT>
template <bool isRela>
void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd,
RelIteratorRange<isRela> Rels) {
typedef Elf_Rel_Impl<ELFT, isRela> RelType;
size_t Num = Rels.end() - Rels.begin();
for (size_t I = 0; I < Num; ++I) {
const RelType &RI = *(Rels.begin() + I);
uint32_t SymIndex = RI.getSymbol(Config->Mips64EL);
uint32_t Type = RI.getType(Config->Mips64EL);
uintX_t Offset = getOffset(RI.r_offset);
if (Offset == (uintX_t)-1)
continue;
uint8_t *BufLoc = Buf + Offset;
uintX_t AddrLoc = OutSec->getVA() + Offset;
auto NextRelocs = llvm::make_range(&RI, Rels.end());
if (Target->isTlsLocalDynamicReloc(Type) &&
!Target->isTlsOptimized(Type, nullptr)) {
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
Out<ELFT>::Got->getLocalTlsIndexVA() +
getAddend<ELFT>(RI));
continue;
}
// Handle relocations for local symbols -- they never get
// resolved so we don't allocate a SymbolBody.
const Elf_Shdr *SymTab = File->getSymbolTable();
if (SymIndex < SymTab->sh_info) {
uintX_t SymVA = getLocalRelTarget(*File, RI);
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA, 0,
findMipsPairedReloc(Buf, SymIndex, Type, NextRelocs));
continue;
}
SymbolBody &Body = *File->getSymbolBody(SymIndex)->repl();
if (Target->isTlsGlobalDynamicReloc(Type) &&
!Target->isTlsOptimized(Type, &Body)) {
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
Out<ELFT>::Got->getGlobalDynAddr(Body) +
getAddend<ELFT>(RI));
continue;
}
if (Target->isTlsOptimized(Type, &Body)) {
uintX_t SymVA = Target->relocNeedsGot(Type, Body)
? Out<ELFT>::Got->getEntryAddr(Body)
: getSymVA<ELFT>(Body);
// By optimizing TLS relocations, it is sometimes needed to skip
// relocations that immediately follow TLS relocations. This function
// knows how many slots we need to skip.
I += Target->relocateTlsOptimize(BufLoc, BufEnd, Type, AddrLoc, SymVA,
Body);
continue;
}
uintX_t SymVA = getSymVA<ELFT>(Body);
if (Target->relocNeedsPlt(Type, Body)) {
SymVA = Out<ELFT>::Plt->getEntryAddr(Body);
Type = Target->getPltRefReloc(Type);
} else if (Target->relocNeedsGot(Type, Body)) {
SymVA = Out<ELFT>::Got->getEntryAddr(Body);
if (Body.isTls())
Type = Target->getTlsGotReloc();
} else if (!Target->needsCopyRel(Type, Body) &&
isa<SharedSymbol<ELFT>>(Body)) {
continue;
} else if (Target->isTlsDynReloc(Type) ||
Target->isSizeDynReloc(Type, Body)) {
continue;
} else if (Config->EMachine == EM_MIPS) {
if (Type == R_MIPS_HI16 && &Body == Config->MipsGpDisp)
SymVA = getMipsGpAddr<ELFT>() - AddrLoc;
else if (Type == R_MIPS_LO16 && &Body == Config->MipsGpDisp)
SymVA = getMipsGpAddr<ELFT>() - AddrLoc + 4;
}
uintX_t A = getAddend<ELFT>(RI);
uintX_t Size = getSymSize<ELFT>(Body);
Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA + A, Size + A,
findMipsPairedReloc(Buf, SymIndex, Type, NextRelocs));
}
}
template <class ELFT> void InputSection<ELFT>::writeTo(uint8_t *Buf) {
if (this->Header->sh_type == SHT_NOBITS)
return;
// Copy section contents from source object file to output file.
ArrayRef<uint8_t> Data = this->getSectionData();
memcpy(Buf + OutSecOff, Data.data(), Data.size());
ELFFile<ELFT> &EObj = this->File->getObj();
uint8_t *BufEnd = Buf + OutSecOff + Data.size();
// Iterate over all relocation sections that apply to this section.
for (const Elf_Shdr *RelSec : this->RelocSections) {
if (RelSec->sh_type == SHT_RELA)
this->relocate(Buf, BufEnd, EObj.relas(RelSec));
else
this->relocate(Buf, BufEnd, EObj.rels(RelSec));
}
}
template <class ELFT>
SplitInputSection<ELFT>::SplitInputSection(
ObjectFile<ELFT> *File, const Elf_Shdr *Header,
typename InputSectionBase<ELFT>::Kind SectionKind)
: InputSectionBase<ELFT>(File, Header, SectionKind) {}
template <class ELFT>
EHInputSection<ELFT>::EHInputSection(ObjectFile<ELFT> *F,
const Elf_Shdr *Header)
: SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::EHFrame) {}
template <class ELFT>
bool EHInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
return S->SectionKind == InputSectionBase<ELFT>::EHFrame;
}
template <class ELFT>
typename EHInputSection<ELFT>::uintX_t
EHInputSection<ELFT>::getOffset(uintX_t Offset) {
std::pair<uintX_t, uintX_t> *I = this->getRangeAndSize(Offset).first;
uintX_t Base = I->second;
if (Base == uintX_t(-1))
return -1; // Not in the output
uintX_t Addend = Offset - I->first;
return Base + Addend;
}
template <class ELFT>
MergeInputSection<ELFT>::MergeInputSection(ObjectFile<ELFT> *F,
const Elf_Shdr *Header)
: SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::Merge) {}
template <class ELFT>
bool MergeInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
return S->SectionKind == InputSectionBase<ELFT>::Merge;
}
template <class ELFT>
std::pair<std::pair<typename ELFFile<ELFT>::uintX_t,
typename ELFFile<ELFT>::uintX_t> *,
typename ELFFile<ELFT>::uintX_t>
SplitInputSection<ELFT>::getRangeAndSize(uintX_t Offset) {
ArrayRef<uint8_t> D = this->getSectionData();
StringRef Data((const char *)D.data(), D.size());
uintX_t Size = Data.size();
if (Offset >= Size)
error("Entry is past the end of the section");
// Find the element this offset points to.
auto I = std::upper_bound(
Offsets.begin(), Offsets.end(), Offset,
[](const uintX_t &A, const std::pair<uintX_t, uintX_t> &B) {
return A < B.first;
});
uintX_t End = I == Offsets.end() ? Data.size() : I->first;
--I;
return std::make_pair(&*I, End);
}
template <class ELFT>
typename MergeInputSection<ELFT>::uintX_t
MergeInputSection<ELFT>::getOffset(uintX_t Offset) {
std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =
this->getRangeAndSize(Offset);
std::pair<uintX_t, uintX_t> *I = T.first;
uintX_t End = T.second;
uintX_t Start = I->first;
// Compute the Addend and if the Base is cached, return.
uintX_t Addend = Offset - Start;
uintX_t &Base = I->second;
if (Base != uintX_t(-1))
return Base + Addend;
// Map the base to the offset in the output section and cache it.
ArrayRef<uint8_t> D = this->getSectionData();
StringRef Data((const char *)D.data(), D.size());
StringRef Entry = Data.substr(Start, End - Start);
Base =
static_cast<MergeOutputSection<ELFT> *>(this->OutSec)->getOffset(Entry);
return Base + Addend;
}
namespace lld {
namespace elf2 {
template class InputSectionBase<object::ELF32LE>;
template class InputSectionBase<object::ELF32BE>;
template class InputSectionBase<object::ELF64LE>;
template class InputSectionBase<object::ELF64BE>;
template class InputSection<object::ELF32LE>;
template class InputSection<object::ELF32BE>;
template class InputSection<object::ELF64LE>;
template class InputSection<object::ELF64BE>;
template class EHInputSection<object::ELF32LE>;
template class EHInputSection<object::ELF32BE>;
template class EHInputSection<object::ELF64LE>;
template class EHInputSection<object::ELF64BE>;
template class MergeInputSection<object::ELF32LE>;
template class MergeInputSection<object::ELF32BE>;
template class MergeInputSection<object::ELF64LE>;
template class MergeInputSection<object::ELF64BE>;
}
}
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