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llvm-project/lld/ELF/OutputSections.cpp

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//===- OutputSections.cpp -------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "OutputSections.h"
#include "Config.h"
#include "SymbolTable.h"
#include "Target.h"
#include "llvm/Support/MathExtras.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf2;
template <class ELFT>
OutputSectionBase<ELFT>::OutputSectionBase(StringRef Name, uint32_t sh_type,
uintX_t sh_flags)
: Name(Name) {
memset(&Header, 0, sizeof(Elf_Shdr));
Header.sh_type = sh_type;
Header.sh_flags = sh_flags;
}
template <class ELFT>
GotPltSection<ELFT>::GotPltSection()
: OutputSectionBase<ELFT>(".got.plt", llvm::ELF::SHT_PROGBITS,
llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_WRITE) {
this->Header.sh_addralign = sizeof(uintX_t);
}
template <class ELFT> void GotPltSection<ELFT>::addEntry(SymbolBody *Sym) {
Sym->GotPltIndex = Target->getGotPltHeaderEntriesNum() + Entries.size();
Entries.push_back(Sym);
}
template <class ELFT> bool GotPltSection<ELFT>::empty() const {
return Entries.empty();
}
template <class ELFT>
typename GotPltSection<ELFT>::uintX_t
GotPltSection<ELFT>::getEntryAddr(const SymbolBody &B) const {
return this->getVA() + B.GotPltIndex * sizeof(uintX_t);
}
template <class ELFT> void GotPltSection<ELFT>::finalize() {
this->Header.sh_size =
(Target->getGotPltHeaderEntriesNum() + Entries.size()) * sizeof(uintX_t);
}
template <class ELFT> void GotPltSection<ELFT>::writeTo(uint8_t *Buf) {
Target->writeGotPltHeaderEntries(Buf);
Buf += Target->getGotPltHeaderEntriesNum() * sizeof(uintX_t);
for (const SymbolBody *B : Entries) {
Target->writeGotPltEntry(Buf, Out<ELFT>::Plt->getEntryAddr(*B));
Buf += sizeof(uintX_t);
}
}
template <class ELFT>
GotSection<ELFT>::GotSection()
: OutputSectionBase<ELFT>(".got", llvm::ELF::SHT_PROGBITS,
llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_WRITE) {
if (Config->EMachine == EM_MIPS)
this->Header.sh_flags |= llvm::ELF::SHF_MIPS_GPREL;
this->Header.sh_addralign = sizeof(uintX_t);
}
template <class ELFT> void GotSection<ELFT>::addEntry(SymbolBody *Sym) {
Sym->GotIndex = Target->getGotHeaderEntriesNum() + Entries.size();
Entries.push_back(Sym);
}
template <class ELFT> void GotSection<ELFT>::addDynTlsEntry(SymbolBody *Sym) {
Sym->GotIndex = Target->getGotHeaderEntriesNum() + Entries.size();
// Global Dynamic TLS entries take two GOT slots.
Entries.push_back(Sym);
Entries.push_back(nullptr);
}
template <class ELFT> uint32_t GotSection<ELFT>::addLocalModuleTlsIndex() {
Entries.push_back(nullptr);
Entries.push_back(nullptr);
return (Entries.size() - 2) * sizeof(uintX_t);
}
template <class ELFT>
typename GotSection<ELFT>::uintX_t
GotSection<ELFT>::getEntryAddr(const SymbolBody &B) const {
return this->getVA() + B.GotIndex * sizeof(uintX_t);
}
template <class ELFT>
const SymbolBody *GotSection<ELFT>::getMipsFirstGlobalEntry() const {
return Entries.empty() ? nullptr : Entries.front();
}
template <class ELFT>
unsigned GotSection<ELFT>::getMipsLocalEntriesNum() const {
// TODO: Update when the suppoort of GOT entries for local symbols is added.
return Target->getGotHeaderEntriesNum();
}
template <class ELFT> void GotSection<ELFT>::finalize() {
this->Header.sh_size =
(Target->getGotHeaderEntriesNum() + Entries.size()) * sizeof(uintX_t);
}
template <class ELFT> void GotSection<ELFT>::writeTo(uint8_t *Buf) {
Target->writeGotHeaderEntries(Buf);
Buf += Target->getGotHeaderEntriesNum() * sizeof(uintX_t);
for (const SymbolBody *B : Entries) {
uint8_t *Entry = Buf;
Buf += sizeof(uintX_t);
if (!B)
continue;
// MIPS has special rules to fill up GOT entries.
// See "Global Offset Table" in Chapter 5 in the following document
// for detailed description:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
// As the first approach, we can just store addresses for all symbols.
if (Config->EMachine != EM_MIPS && canBePreempted(B, false))
continue; // The dynamic linker will take care of it.
uintX_t VA = getSymVA<ELFT>(*B);
write<uintX_t, ELFT::TargetEndianness, sizeof(uintX_t)>(Entry, VA);
}
}
template <class ELFT>
PltSection<ELFT>::PltSection()
: OutputSectionBase<ELFT>(".plt", llvm::ELF::SHT_PROGBITS,
llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_EXECINSTR) {
this->Header.sh_addralign = 16;
}
template <class ELFT> void PltSection<ELFT>::writeTo(uint8_t *Buf) {
size_t Off = 0;
bool LazyReloc = Target->supportsLazyRelocations();
if (LazyReloc) {
// First write PLT[0] entry which is special.
Target->writePltZeroEntry(Buf, Out<ELFT>::GotPlt->getVA(), this->getVA());
Off += Target->getPltZeroEntrySize();
}
for (auto &I : Entries) {
const SymbolBody *E = I.first;
unsigned RelOff = I.second;
uint64_t GotVA =
LazyReloc ? Out<ELFT>::GotPlt->getVA() : Out<ELFT>::Got->getVA();
uint64_t GotE = LazyReloc ? Out<ELFT>::GotPlt->getEntryAddr(*E)
: Out<ELFT>::Got->getEntryAddr(*E);
uint64_t Plt = this->getVA() + Off;
Target->writePltEntry(Buf + Off, GotVA, GotE, Plt, E->PltIndex, RelOff);
Off += Target->getPltEntrySize();
}
}
template <class ELFT> void PltSection<ELFT>::addEntry(SymbolBody *Sym) {
Sym->PltIndex = Entries.size();
unsigned RelOff = Target->supportsLazyRelocations()
? Out<ELFT>::RelaPlt->getRelocOffset()
: Out<ELFT>::RelaDyn->getRelocOffset();
Entries.push_back(std::make_pair(Sym, RelOff));
}
template <class ELFT>
typename PltSection<ELFT>::uintX_t
PltSection<ELFT>::getEntryAddr(const SymbolBody &B) const {
return this->getVA() + Target->getPltZeroEntrySize() +
B.PltIndex * Target->getPltEntrySize();
}
template <class ELFT> void PltSection<ELFT>::finalize() {
this->Header.sh_size = Target->getPltZeroEntrySize() +
Entries.size() * Target->getPltEntrySize();
}
template <class ELFT>
RelocationSection<ELFT>::RelocationSection(StringRef Name, bool IsRela)
: OutputSectionBase<ELFT>(Name,
IsRela ? llvm::ELF::SHT_RELA : llvm::ELF::SHT_REL,
llvm::ELF::SHF_ALLOC),
IsRela(IsRela) {
this->Header.sh_entsize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
this->Header.sh_addralign = ELFT::Is64Bits ? 8 : 4;
}
// Applies corresponding symbol and type for dynamic tls relocation.
// Returns true if relocation was handled.
template <class ELFT>
bool RelocationSection<ELFT>::applyTlsDynamicReloc(SymbolBody *Body,
uint32_t Type, Elf_Rel *P,
Elf_Rel *N) {
if (Target->isTlsLocalDynamicReloc(Type)) {
P->setSymbolAndType(0, Target->getTlsModuleIndexReloc(), Config->Mips64EL);
P->r_offset =
Out<ELFT>::Got->getVA() + Out<ELFT>::LocalModuleTlsIndexOffset;
return true;
}
if (Body && Target->isTlsGlobalDynamicReloc(Type)) {
P->setSymbolAndType(Body->getDynamicSymbolTableIndex(),
Target->getTlsModuleIndexReloc(), Config->Mips64EL);
P->r_offset = Out<ELFT>::Got->getEntryAddr(*Body);
N->setSymbolAndType(Body->getDynamicSymbolTableIndex(),
Target->getTlsOffsetReloc(), Config->Mips64EL);
N->r_offset = Out<ELFT>::Got->getEntryAddr(*Body) + sizeof(uintX_t);
return true;
}
return false;
}
template <class ELFT> void RelocationSection<ELFT>::writeTo(uint8_t *Buf) {
const unsigned EntrySize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
for (const DynamicReloc<ELFT> &Rel : Relocs) {
auto *P = reinterpret_cast<Elf_Rel *>(Buf);
Buf += EntrySize;
// Skip placeholder for global dynamic TLS relocation pair. It was already
// handled by the previous relocation.
if (!Rel.C || !Rel.RI)
continue;
InputSectionBase<ELFT> &C = *Rel.C;
const Elf_Rel &RI = *Rel.RI;
uint32_t SymIndex = RI.getSymbol(Config->Mips64EL);
const ObjectFile<ELFT> &File = *C.getFile();
SymbolBody *Body = File.getSymbolBody(SymIndex);
if (Body)
Body = Body->repl();
uint32_t Type = RI.getType(Config->Mips64EL);
if (applyTlsDynamicReloc(Body, Type, P, reinterpret_cast<Elf_Rel *>(Buf)))
continue;
bool NeedsCopy = Body && Target->relocNeedsCopy(Type, *Body);
bool NeedsGot = Body && Target->relocNeedsGot(Type, *Body);
bool CanBePreempted = canBePreempted(Body, NeedsGot);
bool LazyReloc = Body && Target->supportsLazyRelocations() &&
Target->relocNeedsPlt(Type, *Body);
if (CanBePreempted) {
unsigned GotReloc =
Body->isTLS() ? Target->getTlsGotReloc() : Target->getGotReloc();
if (NeedsGot)
P->setSymbolAndType(Body->getDynamicSymbolTableIndex(),
LazyReloc ? Target->getPltReloc() : GotReloc,
Config->Mips64EL);
else
P->setSymbolAndType(Body->getDynamicSymbolTableIndex(),
NeedsCopy ? Target->getCopyReloc()
: Target->getDynReloc(Type),
Config->Mips64EL);
} else {
P->setSymbolAndType(0, Target->getRelativeReloc(), Config->Mips64EL);
}
if (NeedsGot) {
if (LazyReloc)
P->r_offset = Out<ELFT>::GotPlt->getEntryAddr(*Body);
else
P->r_offset = Out<ELFT>::Got->getEntryAddr(*Body);
} else if (NeedsCopy) {
P->r_offset = Out<ELFT>::Bss->getVA() +
dyn_cast<SharedSymbol<ELFT>>(Body)->OffsetInBSS;
} else {
P->r_offset = C.getOffset(RI.r_offset) + C.OutSec->getVA();
}
uintX_t OrigAddend = 0;
if (IsRela && !NeedsGot)
OrigAddend = static_cast<const Elf_Rela &>(RI).r_addend;
uintX_t Addend;
if (NeedsCopy)
Addend = 0;
else if (CanBePreempted)
Addend = OrigAddend;
else if (Body)
Addend = getSymVA<ELFT>(cast<ELFSymbolBody<ELFT>>(*Body)) + OrigAddend;
else if (IsRela)
Addend = getLocalRelTarget(File, static_cast<const Elf_Rela &>(RI));
else
Addend = getLocalRelTarget(File, RI);
if (IsRela)
static_cast<Elf_Rela *>(P)->r_addend = Addend;
}
}
template <class ELFT> unsigned RelocationSection<ELFT>::getRelocOffset() {
const unsigned EntrySize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
return EntrySize * Relocs.size();
}
template <class ELFT> void RelocationSection<ELFT>::finalize() {
this->Header.sh_link = Out<ELFT>::DynSymTab->SectionIndex;
this->Header.sh_size = Relocs.size() * this->Header.sh_entsize;
}
template <class ELFT>
InterpSection<ELFT>::InterpSection()
: OutputSectionBase<ELFT>(".interp", llvm::ELF::SHT_PROGBITS,
llvm::ELF::SHF_ALLOC) {
this->Header.sh_size = Config->DynamicLinker.size() + 1;
this->Header.sh_addralign = 1;
}
template <class ELFT>
void OutputSectionBase<ELFT>::writeHeaderTo(Elf_Shdr *SHdr) {
Header.sh_name = Out<ELFT>::ShStrTab->getOffset(Name);
*SHdr = Header;
}
template <class ELFT> void InterpSection<ELFT>::writeTo(uint8_t *Buf) {
memcpy(Buf, Config->DynamicLinker.data(), Config->DynamicLinker.size());
}
template <class ELFT>
HashTableSection<ELFT>::HashTableSection()
: OutputSectionBase<ELFT>(".hash", llvm::ELF::SHT_HASH,
llvm::ELF::SHF_ALLOC) {
this->Header.sh_entsize = sizeof(Elf_Word);
this->Header.sh_addralign = sizeof(Elf_Word);
}
static uint32_t hashSysv(StringRef Name) {
uint32_t H = 0;
for (char C : Name) {
H = (H << 4) + C;
uint32_t G = H & 0xf0000000;
if (G)
H ^= G >> 24;
H &= ~G;
}
return H;
}
template <class ELFT> void HashTableSection<ELFT>::finalize() {
this->Header.sh_link = Out<ELFT>::DynSymTab->SectionIndex;
unsigned NumEntries = 2; // nbucket and nchain.
NumEntries += Out<ELFT>::DynSymTab->getNumSymbols(); // The chain entries.
// Create as many buckets as there are symbols.
// FIXME: This is simplistic. We can try to optimize it, but implementing
// support for SHT_GNU_HASH is probably even more profitable.
NumEntries += Out<ELFT>::DynSymTab->getNumSymbols();
this->Header.sh_size = NumEntries * sizeof(Elf_Word);
}
template <class ELFT> void HashTableSection<ELFT>::writeTo(uint8_t *Buf) {
unsigned NumSymbols = Out<ELFT>::DynSymTab->getNumSymbols();
auto *P = reinterpret_cast<Elf_Word *>(Buf);
*P++ = NumSymbols; // nbucket
*P++ = NumSymbols; // nchain
Elf_Word *Buckets = P;
Elf_Word *Chains = P + NumSymbols;
for (SymbolBody *Body : Out<ELFT>::DynSymTab->getSymbols()) {
StringRef Name = Body->getName();
unsigned I = Body->getDynamicSymbolTableIndex();
uint32_t Hash = hashSysv(Name) % NumSymbols;
Chains[I] = Buckets[Hash];
Buckets[Hash] = I;
}
}
static uint32_t hashGnu(StringRef Name) {
uint32_t H = 5381;
for (uint8_t C : Name)
H = (H << 5) + H + C;
return H;
}
template <class ELFT>
GnuHashTableSection<ELFT>::GnuHashTableSection()
: OutputSectionBase<ELFT>(".gnu.hash", llvm::ELF::SHT_GNU_HASH,
llvm::ELF::SHF_ALLOC) {
this->Header.sh_entsize = ELFT::Is64Bits ? 0 : 4;
this->Header.sh_addralign = ELFT::Is64Bits ? 8 : 4;
}
template <class ELFT>
unsigned GnuHashTableSection<ELFT>::calcNBuckets(unsigned NumHashed) {
if (!NumHashed)
return 0;
// These values are prime numbers which are not greater than 2^(N-1) + 1.
// In result, for any particular NumHashed we return a prime number
// which is not greater than NumHashed.
static const unsigned Primes[] = {
1, 1, 3, 3, 7, 13, 31, 61, 127, 251,
509, 1021, 2039, 4093, 8191, 16381, 32749, 65521, 131071};
return Primes[std::min<unsigned>(Log2_32_Ceil(NumHashed),
array_lengthof(Primes) - 1)];
}
// Bloom filter estimation: at least 8 bits for each hashed symbol.
// GNU Hash table requirement: it should be a power of 2,
// the minimum value is 1, even for an empty table.
// Expected results for a 32-bit target:
// calcMaskWords(0..4) = 1
// calcMaskWords(5..8) = 2
// calcMaskWords(9..16) = 4
// For a 64-bit target:
// calcMaskWords(0..8) = 1
// calcMaskWords(9..16) = 2
// calcMaskWords(17..32) = 4
template <class ELFT>
unsigned GnuHashTableSection<ELFT>::calcMaskWords(unsigned NumHashed) {
if (!NumHashed)
return 1;
return NextPowerOf2((NumHashed - 1) / sizeof(Elf_Off));
}
template <class ELFT> void GnuHashTableSection<ELFT>::finalize() {
unsigned NumHashed = HashedSymbols.size();
NBuckets = calcNBuckets(NumHashed);
MaskWords = calcMaskWords(NumHashed);
// Second hash shift estimation: just predefined values.
Shift2 = ELFT::Is64Bits ? 6 : 5;
this->Header.sh_link = Out<ELFT>::DynSymTab->SectionIndex;
this->Header.sh_size = sizeof(Elf_Word) * 4 // Header
+ sizeof(Elf_Off) * MaskWords // Bloom Filter
+ sizeof(Elf_Word) * NBuckets // Hash Buckets
+ sizeof(Elf_Word) * NumHashed; // Hash Values
}
template <class ELFT> void GnuHashTableSection<ELFT>::writeTo(uint8_t *Buf) {
writeHeader(Buf);
if (HashedSymbols.empty())
return;
writeBloomFilter(Buf);
writeHashTable(Buf);
}
template <class ELFT>
void GnuHashTableSection<ELFT>::writeHeader(uint8_t *&Buf) {
auto *P = reinterpret_cast<Elf_Word *>(Buf);
*P++ = NBuckets;
*P++ = Out<ELFT>::DynSymTab->getNumSymbols() - HashedSymbols.size();
*P++ = MaskWords;
*P++ = Shift2;
Buf = reinterpret_cast<uint8_t *>(P);
}
template <class ELFT>
void GnuHashTableSection<ELFT>::writeBloomFilter(uint8_t *&Buf) {
unsigned C = sizeof(Elf_Off) * 8;
auto *Masks = reinterpret_cast<Elf_Off *>(Buf);
for (const HashedSymbolData &Item : HashedSymbols) {
size_t Pos = (Item.Hash / C) & (MaskWords - 1);
uintX_t V = (uintX_t(1) << (Item.Hash % C)) |
(uintX_t(1) << ((Item.Hash >> Shift2) % C));
Masks[Pos] |= V;
}
Buf += sizeof(Elf_Off) * MaskWords;
}
template <class ELFT>
void GnuHashTableSection<ELFT>::writeHashTable(uint8_t *Buf) {
Elf_Word *Buckets = reinterpret_cast<Elf_Word *>(Buf);
Elf_Word *Values = Buckets + NBuckets;
int PrevBucket = -1;
int I = 0;
for (const HashedSymbolData &Item : HashedSymbols) {
int Bucket = Item.Hash % NBuckets;
assert(PrevBucket <= Bucket);
if (Bucket != PrevBucket) {
Buckets[Bucket] = Item.Body->getDynamicSymbolTableIndex();
PrevBucket = Bucket;
if (I > 0)
Values[I - 1] |= 1;
}
Values[I] = Item.Hash & ~1;
++I;
}
if (I > 0)
Values[I - 1] |= 1;
}
static bool includeInGnuHashTable(SymbolBody *B) {
// Assume that includeInDynamicSymtab() is already checked.
return !B->isUndefined();
}
template <class ELFT>
void GnuHashTableSection<ELFT>::addSymbols(std::vector<SymbolBody *> &Symbols) {
std::vector<SymbolBody *> NotHashed;
NotHashed.reserve(Symbols.size());
HashedSymbols.reserve(Symbols.size());
for (SymbolBody *B : Symbols) {
if (includeInGnuHashTable(B))
HashedSymbols.push_back(HashedSymbolData{B, hashGnu(B->getName())});
else
NotHashed.push_back(B);
}
if (HashedSymbols.empty())
return;
unsigned NBuckets = calcNBuckets(HashedSymbols.size());
std::stable_sort(HashedSymbols.begin(), HashedSymbols.end(),
[&](const HashedSymbolData &L, const HashedSymbolData &R) {
return L.Hash % NBuckets < R.Hash % NBuckets;
});
Symbols = std::move(NotHashed);
for (const HashedSymbolData &Item : HashedSymbols)
Symbols.push_back(Item.Body);
}
template <class ELFT>
DynamicSection<ELFT>::DynamicSection(SymbolTable<ELFT> &SymTab)
: OutputSectionBase<ELFT>(".dynamic", llvm::ELF::SHT_DYNAMIC,
llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_WRITE),
SymTab(SymTab) {
Elf_Shdr &Header = this->Header;
Header.sh_addralign = ELFT::Is64Bits ? 8 : 4;
Header.sh_entsize = ELFT::Is64Bits ? 16 : 8;
// .dynamic section is not writable on MIPS.
// See "Special Section" in Chapter 4 in the following document:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
if (Config->EMachine == EM_MIPS)
Header.sh_flags = llvm::ELF::SHF_ALLOC;
}
template <class ELFT> void DynamicSection<ELFT>::finalize() {
if (this->Header.sh_size)
return; // Already finalized.
Elf_Shdr &Header = this->Header;
Header.sh_link = Out<ELFT>::DynStrTab->SectionIndex;
unsigned NumEntries = 0;
if (Out<ELFT>::RelaDyn->hasRelocs()) {
++NumEntries; // DT_RELA / DT_REL
++NumEntries; // DT_RELASZ / DT_RELSZ
++NumEntries; // DT_RELAENT / DT_RELENT
}
if (Out<ELFT>::RelaPlt && Out<ELFT>::RelaPlt->hasRelocs()) {
++NumEntries; // DT_JMPREL
++NumEntries; // DT_PLTRELSZ
++NumEntries; // DT_PLTGOT / DT_MIPS_PLTGOT
++NumEntries; // DT_PLTREL
}
++NumEntries; // DT_SYMTAB
++NumEntries; // DT_SYMENT
++NumEntries; // DT_STRTAB
++NumEntries; // DT_STRSZ
if (Out<ELFT>::GnuHashTab)
++NumEntries; // DT_GNU_HASH
if (Out<ELFT>::HashTab)
++NumEntries; // DT_HASH
if (!Config->RPath.empty()) {
++NumEntries; // DT_RUNPATH / DT_RPATH
Out<ELFT>::DynStrTab->add(Config->RPath);
}
if (!Config->SoName.empty()) {
++NumEntries; // DT_SONAME
Out<ELFT>::DynStrTab->add(Config->SoName);
}
if (PreInitArraySec)
NumEntries += 2;
if (InitArraySec)
NumEntries += 2;
if (FiniArraySec)
NumEntries += 2;
for (const std::unique_ptr<SharedFile<ELFT>> &F : SymTab.getSharedFiles()) {
if (!F->isNeeded())
continue;
Out<ELFT>::DynStrTab->add(F->getSoName());
++NumEntries;
}
if (Symbol *S = SymTab.getSymbols().lookup(Config->Init))
InitSym = dyn_cast<ELFSymbolBody<ELFT>>(S->Body);
if (Symbol *S = SymTab.getSymbols().lookup(Config->Fini))
FiniSym = dyn_cast<ELFSymbolBody<ELFT>>(S->Body);
if (InitSym)
++NumEntries; // DT_INIT
if (FiniSym)
++NumEntries; // DT_FINI
if (Config->Bsymbolic)
DtFlags |= DF_SYMBOLIC;
if (Config->ZNodelete)
DtFlags1 |= DF_1_NODELETE;
if (Config->ZNow) {
DtFlags |= DF_BIND_NOW;
DtFlags1 |= DF_1_NOW;
}
if (Config->ZOrigin) {
DtFlags |= DF_ORIGIN;
DtFlags1 |= DF_1_ORIGIN;
}
if (DtFlags)
++NumEntries; // DT_FLAGS
if (DtFlags1)
++NumEntries; // DT_FLAGS_1
if (Config->EMachine == EM_MIPS) {
++NumEntries; // DT_MIPS_RLD_VERSION
++NumEntries; // DT_MIPS_FLAGS
++NumEntries; // DT_MIPS_BASE_ADDRESS
++NumEntries; // DT_MIPS_SYMTABNO
++NumEntries; // DT_MIPS_LOCAL_GOTNO
++NumEntries; // DT_MIPS_GOTSYM;
++NumEntries; // DT_PLTGOT
if (Out<ELFT>::MipsRldMap)
++NumEntries; // DT_MIPS_RLD_MAP
}
++NumEntries; // DT_NULL
Header.sh_size = NumEntries * Header.sh_entsize;
}
template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *Buf) {
auto *P = reinterpret_cast<Elf_Dyn *>(Buf);
auto WritePtr = [&](int32_t Tag, uint64_t Val) {
P->d_tag = Tag;
P->d_un.d_ptr = Val;
++P;
};
auto WriteVal = [&](int32_t Tag, uint32_t Val) {
P->d_tag = Tag;
P->d_un.d_val = Val;
++P;
};
if (Out<ELFT>::RelaDyn->hasRelocs()) {
bool IsRela = Out<ELFT>::RelaDyn->isRela();
WritePtr(IsRela ? DT_RELA : DT_REL, Out<ELFT>::RelaDyn->getVA());
WriteVal(IsRela ? DT_RELASZ : DT_RELSZ, Out<ELFT>::RelaDyn->getSize());
WriteVal(IsRela ? DT_RELAENT : DT_RELENT,
IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel));
}
if (Out<ELFT>::RelaPlt && Out<ELFT>::RelaPlt->hasRelocs()) {
WritePtr(DT_JMPREL, Out<ELFT>::RelaPlt->getVA());
WriteVal(DT_PLTRELSZ, Out<ELFT>::RelaPlt->getSize());
// On MIPS, the address of the .got.plt section is stored in
// the DT_MIPS_PLTGOT entry because the DT_PLTGOT entry points to
// the .got section. See "Dynamic Section" in the following document:
// https://sourceware.org/ml/binutils/2008-07/txt00000.txt
WritePtr((Config->EMachine == EM_MIPS) ? DT_MIPS_PLTGOT : DT_PLTGOT,
Out<ELFT>::GotPlt->getVA());
WriteVal(DT_PLTREL, Out<ELFT>::RelaPlt->isRela() ? DT_RELA : DT_REL);
}
WritePtr(DT_SYMTAB, Out<ELFT>::DynSymTab->getVA());
WritePtr(DT_SYMENT, sizeof(Elf_Sym));
WritePtr(DT_STRTAB, Out<ELFT>::DynStrTab->getVA());
WriteVal(DT_STRSZ, Out<ELFT>::DynStrTab->data().size());
if (Out<ELFT>::GnuHashTab)
WritePtr(DT_GNU_HASH, Out<ELFT>::GnuHashTab->getVA());
if (Out<ELFT>::HashTab)
WritePtr(DT_HASH, Out<ELFT>::HashTab->getVA());
// If --enable-new-dtags is set, lld emits DT_RUNPATH
// instead of DT_RPATH. The two tags are functionally
// equivalent except for the following:
// - DT_RUNPATH is searched after LD_LIBRARY_PATH, while
// DT_RPATH is searched before.
// - DT_RUNPATH is used only to search for direct
// dependencies of the object it's contained in, while
// DT_RPATH is used for indirect dependencies as well.
if (!Config->RPath.empty())
WriteVal(Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH,
Out<ELFT>::DynStrTab->getOffset(Config->RPath));
if (!Config->SoName.empty())
WriteVal(DT_SONAME, Out<ELFT>::DynStrTab->getOffset(Config->SoName));
auto WriteArray = [&](int32_t T1, int32_t T2,
const OutputSectionBase<ELFT> *Sec) {
if (!Sec)
return;
WritePtr(T1, Sec->getVA());
WriteVal(T2, Sec->getSize());
};
WriteArray(DT_PREINIT_ARRAY, DT_PREINIT_ARRAYSZ, PreInitArraySec);
WriteArray(DT_INIT_ARRAY, DT_INIT_ARRAYSZ, InitArraySec);
WriteArray(DT_FINI_ARRAY, DT_FINI_ARRAYSZ, FiniArraySec);
for (const std::unique_ptr<SharedFile<ELFT>> &F : SymTab.getSharedFiles())
if (F->isNeeded())
WriteVal(DT_NEEDED, Out<ELFT>::DynStrTab->getOffset(F->getSoName()));
if (InitSym)
WritePtr(DT_INIT, getSymVA<ELFT>(*InitSym));
if (FiniSym)
WritePtr(DT_FINI, getSymVA<ELFT>(*FiniSym));
if (DtFlags)
WriteVal(DT_FLAGS, DtFlags);
if (DtFlags1)
WriteVal(DT_FLAGS_1, DtFlags1);
// See "Dynamic Section" in Chapter 5 in the following document
// for detailed description:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
if (Config->EMachine == EM_MIPS) {
WriteVal(DT_MIPS_RLD_VERSION, 1);
WriteVal(DT_MIPS_FLAGS, RHF_NOTPOT);
WritePtr(DT_MIPS_BASE_ADDRESS, Target->getVAStart());
WriteVal(DT_MIPS_SYMTABNO, Out<ELFT>::DynSymTab->getNumSymbols());
WriteVal(DT_MIPS_LOCAL_GOTNO, Out<ELFT>::Got->getMipsLocalEntriesNum());
if (const SymbolBody *B = Out<ELFT>::Got->getMipsFirstGlobalEntry())
WriteVal(DT_MIPS_GOTSYM, B->getDynamicSymbolTableIndex());
else
WriteVal(DT_MIPS_GOTSYM, Out<ELFT>::DynSymTab->getNumSymbols());
WritePtr(DT_PLTGOT, Out<ELFT>::Got->getVA());
if (Out<ELFT>::MipsRldMap)
WritePtr(DT_MIPS_RLD_MAP, Out<ELFT>::MipsRldMap->getVA());
}
WriteVal(DT_NULL, 0);
}
template <class ELFT>
OutputSection<ELFT>::OutputSection(StringRef Name, uint32_t sh_type,
uintX_t sh_flags)
: OutputSectionBase<ELFT>(Name, sh_type, sh_flags) {}
template <class ELFT>
void OutputSection<ELFT>::addSection(InputSection<ELFT> *C) {
Sections.push_back(C);
C->OutSec = this;
uint32_t Align = C->getAlign();
if (Align > this->Header.sh_addralign)
this->Header.sh_addralign = Align;
uintX_t Off = this->Header.sh_size;
Off = RoundUpToAlignment(Off, Align);
C->OutSecOff = Off;
Off += C->getSize();
this->Header.sh_size = Off;
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t lld::elf2::getSymVA(const SymbolBody &S) {
switch (S.kind()) {
case SymbolBody::DefinedSyntheticKind: {
auto &D = cast<DefinedSynthetic<ELFT>>(S);
return D.Section.getVA() + D.Sym.st_value;
}
case SymbolBody::DefinedAbsoluteKind:
return cast<DefinedAbsolute<ELFT>>(S).Sym.st_value;
case SymbolBody::DefinedRegularKind: {
const auto &DR = cast<DefinedRegular<ELFT>>(S);
InputSectionBase<ELFT> &SC = DR.Section;
if (DR.Sym.getType() == STT_TLS)
return SC.OutSec->getVA() + SC.getOffset(DR.Sym) -
Out<ELFT>::TlsPhdr->p_vaddr;
return SC.OutSec->getVA() + SC.getOffset(DR.Sym);
}
case SymbolBody::DefinedCommonKind:
return Out<ELFT>::Bss->getVA() + cast<DefinedCommon<ELFT>>(S).OffsetInBSS;
case SymbolBody::SharedKind: {
auto &SS = cast<SharedSymbol<ELFT>>(S);
if (SS.needsCopy())
return Out<ELFT>::Bss->getVA() + SS.OffsetInBSS;
return 0;
}
case SymbolBody::UndefinedKind:
return 0;
case SymbolBody::LazyKind:
assert(S.isUsedInRegularObj() && "Lazy symbol reached writer");
return 0;
}
llvm_unreachable("Invalid symbol kind");
}
// Returns a VA which a relocatin RI refers to. Used only for local symbols.
// For non-local symbols, use getSymVA instead.
template <class ELFT, bool IsRela>
typename ELFFile<ELFT>::uintX_t
lld::elf2::getLocalRelTarget(const ObjectFile<ELFT> &File,
const Elf_Rel_Impl<ELFT, IsRela> &RI) {
typedef typename ELFFile<ELFT>::Elf_Sym Elf_Sym;
typedef typename ELFFile<ELFT>::uintX_t uintX_t;
uintX_t Addend = getAddend<ELFT>(RI);
// PPC64 has a special relocation representing the TOC base pointer
// that does not have a corresponding symbol.
if (Config->EMachine == EM_PPC64 && RI.getType(false) == R_PPC64_TOC)
return getPPC64TocBase() + Addend;
const Elf_Sym *Sym =
File.getObj().getRelocationSymbol(&RI, File.getSymbolTable());
if (!Sym)
error("Unsupported relocation without symbol");
InputSectionBase<ELFT> *Section = File.getSection(*Sym);
if (Sym->getType() == STT_TLS)
return (Section->OutSec->getVA() + Section->getOffset(*Sym) + Addend) -
Out<ELFT>::TlsPhdr->p_vaddr;
// According to the ELF spec reference to a local symbol from outside
// the group are not allowed. Unfortunately .eh_frame breaks that rule
// and must be treated specially. For now we just replace the symbol with
// 0.
if (Section == &InputSection<ELFT>::Discarded || !Section->isLive())
return Addend;
uintX_t VA = Section->OutSec->getVA();
if (isa<InputSection<ELFT>>(Section))
return VA + Section->getOffset(*Sym) + Addend;
uintX_t Offset = Sym->st_value;
if (Sym->getType() == STT_SECTION) {
Offset += Addend;
Addend = 0;
}
return VA + cast<MergeInputSection<ELFT>>(Section)->getOffset(Offset) +
Addend;
}
// Returns true if a symbol can be replaced at load-time by a symbol
// with the same name defined in other ELF executable or DSO.
bool lld::elf2::canBePreempted(const SymbolBody *Body, bool NeedsGot) {
if (!Body)
return false; // Body is a local symbol.
if (Body->isShared())
return true;
if (Body->isUndefined()) {
if (!Body->isWeak())
return true;
// This is an horrible corner case. Ideally we would like to say that any
// undefined symbol can be preempted so that the dynamic linker has a
// chance of finding it at runtime.
//
// The problem is that the code sequence used to test for weak undef
// functions looks like
// if (func) func()
// If the code is -fPIC the first reference is a load from the got and
// everything works.
// If the code is not -fPIC there is no reasonable way to solve it:
// * A relocation writing to the text segment will fail (it is ro).
// * A copy relocation doesn't work for functions.
// * The trick of using a plt entry as the address would fail here since
// the plt entry would have a non zero address.
// Since we cannot do anything better, we just resolve the symbol to 0 and
// don't produce a dynamic relocation.
//
// As an extra hack, assume that if we are producing a shared library the
// user knows what he or she is doing and can handle a dynamic relocation.
return Config->Shared || NeedsGot;
}
if (!Config->Shared)
return false;
return Body->getVisibility() == STV_DEFAULT;
}
template <class ELFT> void OutputSection<ELFT>::writeTo(uint8_t *Buf) {
for (InputSection<ELFT> *C : Sections)
C->writeTo(Buf);
}
template <class ELFT>
EHOutputSection<ELFT>::EHOutputSection(StringRef Name, uint32_t sh_type,
uintX_t sh_flags)
: OutputSectionBase<ELFT>(Name, sh_type, sh_flags) {}
template <class ELFT>
EHRegion<ELFT>::EHRegion(EHInputSection<ELFT> *S, unsigned Index)
: S(S), Index(Index) {}
template <class ELFT> StringRef EHRegion<ELFT>::data() const {
ArrayRef<uint8_t> SecData = S->getSectionData();
ArrayRef<std::pair<uintX_t, uintX_t>> Offsets = S->Offsets;
size_t Start = Offsets[Index].first;
size_t End =
Index == Offsets.size() - 1 ? SecData.size() : Offsets[Index + 1].first;
return StringRef((const char *)SecData.data() + Start, End - Start);
}
template <class ELFT>
Cie<ELFT>::Cie(EHInputSection<ELFT> *S, unsigned Index)
: EHRegion<ELFT>(S, Index) {}
template <class ELFT>
template <bool IsRela>
void EHOutputSection<ELFT>::addSectionAux(
EHInputSection<ELFT> *S,
iterator_range<const Elf_Rel_Impl<ELFT, IsRela> *> Rels) {
const endianness E = ELFT::TargetEndianness;
S->OutSec = this;
uint32_t Align = S->getAlign();
if (Align > this->Header.sh_addralign)
this->Header.sh_addralign = Align;
Sections.push_back(S);
ArrayRef<uint8_t> SecData = S->getSectionData();
ArrayRef<uint8_t> D = SecData;
uintX_t Offset = 0;
auto RelI = Rels.begin();
auto RelE = Rels.end();
DenseMap<unsigned, unsigned> OffsetToIndex;
while (!D.empty()) {
if (D.size() < 4)
error("Truncated CIE/FDE length");
uint32_t Length = read32<E>(D.data());
Length += 4;
unsigned Index = S->Offsets.size();
S->Offsets.push_back(std::make_pair(Offset, -1));
if (Length > D.size())
error("CIE/FIE ends past the end of the section");
StringRef Entry((const char *)D.data(), Length);
while (RelI != RelE && RelI->r_offset < Offset)
++RelI;
uintX_t NextOffset = Offset + Length;
bool HasReloc = RelI != RelE && RelI->r_offset < NextOffset;
uint32_t ID = read32<E>(D.data() + 4);
if (ID == 0) {
// CIE
Cie<ELFT> C(S, Index);
StringRef Personality;
if (HasReloc) {
uint32_t SymIndex = RelI->getSymbol(Config->Mips64EL);
SymbolBody &Body = *S->getFile()->getSymbolBody(SymIndex)->repl();
Personality = Body.getName();
}
std::pair<StringRef, StringRef> CieInfo(Entry, Personality);
auto P = CieMap.insert(std::make_pair(CieInfo, Cies.size()));
if (P.second) {
Cies.push_back(C);
this->Header.sh_size += Length;
}
OffsetToIndex[Offset] = P.first->second;
} else {
if (!HasReloc)
error("FDE doesn't reference another section");
InputSectionBase<ELFT> *Target = S->getRelocTarget(*RelI);
if (Target != &InputSection<ELFT>::Discarded && Target->isLive()) {
uint32_t CieOffset = Offset + 4 - ID;
auto I = OffsetToIndex.find(CieOffset);
if (I == OffsetToIndex.end())
error("Invalid CIE reference");
Cies[I->second].Fdes.push_back(EHRegion<ELFT>(S, Index));
this->Header.sh_size += Length;
}
}
Offset = NextOffset;
D = D.slice(Length);
}
}
template <class ELFT>
void EHOutputSection<ELFT>::addSection(EHInputSection<ELFT> *S) {
const Elf_Shdr *RelSec = S->RelocSection;
if (!RelSec)
return addSectionAux(
S, make_range((const Elf_Rela *)nullptr, (const Elf_Rela *)nullptr));
ELFFile<ELFT> &Obj = S->getFile()->getObj();
if (RelSec->sh_type == SHT_RELA)
return addSectionAux(S, Obj.relas(RelSec));
return addSectionAux(S, Obj.rels(RelSec));
}
template <class ELFT> void EHOutputSection<ELFT>::writeTo(uint8_t *Buf) {
const endianness E = ELFT::TargetEndianness;
size_t Offset = 0;
for (const Cie<ELFT> &C : Cies) {
size_t CieOffset = Offset;
StringRef CieData = C.data();
memcpy(Buf + Offset, CieData.data(), CieData.size());
C.S->Offsets[C.Index].second = Offset;
Offset += CieData.size();
for (const EHRegion<ELFT> &F : C.Fdes) {
StringRef FdeData = F.data();
memcpy(Buf + Offset, FdeData.data(), 4); // Legnth
write32<E>(Buf + Offset + 4, Offset + 4 - CieOffset); // Pointer
memcpy(Buf + Offset + 8, FdeData.data() + 8, FdeData.size() - 8);
F.S->Offsets[F.Index].second = Offset;
Offset += FdeData.size();
}
}
for (EHInputSection<ELFT> *S : Sections) {
const Elf_Shdr *RelSec = S->RelocSection;
if (!RelSec)
continue;
ELFFile<ELFT> &EObj = S->getFile()->getObj();
if (RelSec->sh_type == SHT_RELA)
S->relocate(Buf, nullptr, EObj.relas(RelSec));
else
S->relocate(Buf, nullptr, EObj.rels(RelSec));
}
}
template <class ELFT>
MergeOutputSection<ELFT>::MergeOutputSection(StringRef Name, uint32_t sh_type,
uintX_t sh_flags)
: OutputSectionBase<ELFT>(Name, sh_type, sh_flags) {}
template <class ELFT> void MergeOutputSection<ELFT>::writeTo(uint8_t *Buf) {
if (shouldTailMerge()) {
StringRef Data = Builder.data();
memcpy(Buf, Data.data(), Data.size());
return;
}
for (const std::pair<StringRef, size_t> &P : Builder.getMap()) {
StringRef Data = P.first;
memcpy(Buf + P.second, Data.data(), Data.size());
}
}
static size_t findNull(StringRef S, size_t EntSize) {
// Optimize the common case.
if (EntSize == 1)
return S.find(0);
for (unsigned I = 0, N = S.size(); I != N; I += EntSize) {
const char *B = S.begin() + I;
if (std::all_of(B, B + EntSize, [](char C) { return C == 0; }))
return I;
}
return StringRef::npos;
}
template <class ELFT>
void MergeOutputSection<ELFT>::addSection(MergeInputSection<ELFT> *S) {
S->OutSec = this;
uint32_t Align = S->getAlign();
if (Align > this->Header.sh_addralign)
this->Header.sh_addralign = Align;
ArrayRef<uint8_t> D = S->getSectionData();
StringRef Data((const char *)D.data(), D.size());
uintX_t EntSize = S->getSectionHdr()->sh_entsize;
uintX_t Offset = 0;
if (this->Header.sh_flags & SHF_STRINGS) {
while (!Data.empty()) {
size_t End = findNull(Data, EntSize);
if (End == StringRef::npos)
error("String is not null terminated");
StringRef Entry = Data.substr(0, End + EntSize);
uintX_t OutputOffset = Builder.add(Entry);
if (shouldTailMerge())
OutputOffset = -1;
S->Offsets.push_back(std::make_pair(Offset, OutputOffset));
uintX_t Size = End + EntSize;
Data = Data.substr(Size);
Offset += Size;
}
} else {
for (unsigned I = 0, N = Data.size(); I != N; I += EntSize) {
StringRef Entry = Data.substr(I, EntSize);
size_t OutputOffset = Builder.add(Entry);
S->Offsets.push_back(std::make_pair(Offset, OutputOffset));
Offset += EntSize;
}
}
}
template <class ELFT>
unsigned MergeOutputSection<ELFT>::getOffset(StringRef Val) {
return Builder.getOffset(Val);
}
template <class ELFT> bool MergeOutputSection<ELFT>::shouldTailMerge() const {
return Config->Optimize >= 2 && this->Header.sh_flags & SHF_STRINGS;
}
template <class ELFT> void MergeOutputSection<ELFT>::finalize() {
if (shouldTailMerge())
Builder.finalize();
this->Header.sh_size = Builder.getSize();
}
template <class ELFT>
StringTableSection<ELFT>::StringTableSection(StringRef Name, bool Dynamic)
: OutputSectionBase<ELFT>(Name, llvm::ELF::SHT_STRTAB,
Dynamic ? (uintX_t)llvm::ELF::SHF_ALLOC : 0),
Dynamic(Dynamic) {
this->Header.sh_addralign = 1;
}
template <class ELFT> void StringTableSection<ELFT>::writeTo(uint8_t *Buf) {
StringRef Data = StrTabBuilder.data();
memcpy(Buf, Data.data(), Data.size());
}
template <class ELFT> bool lld::elf2::includeInSymtab(const SymbolBody &B) {
if (!B.isUsedInRegularObj())
return false;
// Don't include synthetic symbols like __init_array_start in every output.
if (auto *U = dyn_cast<DefinedAbsolute<ELFT>>(&B))
if (&U->Sym == &DefinedAbsolute<ELFT>::IgnoreUndef)
return false;
return true;
}
bool lld::elf2::includeInDynamicSymtab(const SymbolBody &B) {
uint8_t V = B.getVisibility();
if (V != STV_DEFAULT && V != STV_PROTECTED)
return false;
if (Config->ExportDynamic || Config->Shared)
return true;
return B.isUsedInDynamicReloc();
}
template <class ELFT>
bool lld::elf2::shouldKeepInSymtab(const ObjectFile<ELFT> &File,
StringRef SymName,
const typename ELFFile<ELFT>::Elf_Sym &Sym) {
if (Sym.getType() == STT_SECTION)
return false;
// If sym references a section in a discarded group, don't keep it.
if (File.getSection(Sym) == &InputSection<ELFT>::Discarded)
return false;
if (Config->DiscardNone)
return true;
// ELF defines dynamic locals as symbols which name starts with ".L".
return !(Config->DiscardLocals && SymName.startswith(".L"));
}
template <class ELFT>
SymbolTableSection<ELFT>::SymbolTableSection(
SymbolTable<ELFT> &Table, StringTableSection<ELFT> &StrTabSec)
: OutputSectionBase<ELFT>(
StrTabSec.isDynamic() ? ".dynsym" : ".symtab",
StrTabSec.isDynamic() ? llvm::ELF::SHT_DYNSYM : llvm::ELF::SHT_SYMTAB,
StrTabSec.isDynamic() ? (uintX_t)llvm::ELF::SHF_ALLOC : 0),
Table(Table), StrTabSec(StrTabSec) {
typedef OutputSectionBase<ELFT> Base;
typename Base::Elf_Shdr &Header = this->Header;
Header.sh_entsize = sizeof(Elf_Sym);
Header.sh_addralign = ELFT::Is64Bits ? 8 : 4;
}
// Orders symbols according to their positions in the GOT,
// in compliance with MIPS ABI rules.
// See "Global Offset Table" in Chapter 5 in the following document
// for detailed description:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
static bool sortMipsSymbols(SymbolBody *L, SymbolBody *R) {
if (!L->isInGot() || !R->isInGot())
return R->isInGot();
return L->GotIndex < R->GotIndex;
}
template <class ELFT> void SymbolTableSection<ELFT>::finalize() {
if (this->Header.sh_size)
return; // Already finalized.
this->Header.sh_size = getNumSymbols() * sizeof(Elf_Sym);
this->Header.sh_link = StrTabSec.SectionIndex;
this->Header.sh_info = NumLocals + 1;
if (!StrTabSec.isDynamic()) {
std::stable_sort(Symbols.begin(), Symbols.end(),
[](SymbolBody *L, SymbolBody *R) {
return getSymbolBinding(L) == STB_LOCAL &&
getSymbolBinding(R) != STB_LOCAL;
});
return;
}
if (Out<ELFT>::GnuHashTab)
// NB: It also sorts Symbols to meet the GNU hash table requirements.
Out<ELFT>::GnuHashTab->addSymbols(Symbols);
else if (Config->EMachine == EM_MIPS)
std::stable_sort(Symbols.begin(), Symbols.end(), sortMipsSymbols);
size_t I = 0;
for (SymbolBody *B : Symbols)
B->setDynamicSymbolTableIndex(++I);
}
template <class ELFT>
void SymbolTableSection<ELFT>::addLocalSymbol(StringRef Name) {
StrTabSec.add(Name);
++NumVisible;
++NumLocals;
}
template <class ELFT>
void SymbolTableSection<ELFT>::addSymbol(SymbolBody *Body) {
StrTabSec.add(Body->getName());
Symbols.push_back(Body);
++NumVisible;
}
template <class ELFT> void SymbolTableSection<ELFT>::writeTo(uint8_t *Buf) {
Buf += sizeof(Elf_Sym);
// All symbols with STB_LOCAL binding precede the weak and global symbols.
// .dynsym only contains global symbols.
if (!Config->DiscardAll && !StrTabSec.isDynamic())
writeLocalSymbols(Buf);
writeGlobalSymbols(Buf);
}
template <class ELFT>
void SymbolTableSection<ELFT>::writeLocalSymbols(uint8_t *&Buf) {
// Iterate over all input object files to copy their local symbols
// to the output symbol table pointed by Buf.
for (const std::unique_ptr<ObjectFile<ELFT>> &File : Table.getObjectFiles()) {
Elf_Sym_Range Syms = File->getLocalSymbols();
for (const Elf_Sym &Sym : Syms) {
ErrorOr<StringRef> SymNameOrErr = Sym.getName(File->getStringTable());
error(SymNameOrErr);
StringRef SymName = *SymNameOrErr;
if (!shouldKeepInSymtab<ELFT>(*File, SymName, Sym))
continue;
auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
uintX_t VA = 0;
if (Sym.st_shndx == SHN_ABS) {
ESym->st_shndx = SHN_ABS;
VA = Sym.st_value;
} else {
InputSectionBase<ELFT> *Section = File->getSection(Sym);
if (!Section->isLive())
continue;
const OutputSectionBase<ELFT> *OutSec = Section->OutSec;
ESym->st_shndx = OutSec->SectionIndex;
VA += OutSec->getVA() + Section->getOffset(Sym);
}
ESym->st_name = StrTabSec.getOffset(SymName);
ESym->st_size = Sym.st_size;
ESym->setBindingAndType(Sym.getBinding(), Sym.getType());
ESym->st_value = VA;
Buf += sizeof(*ESym);
}
}
}
template <class ELFT>
void SymbolTableSection<ELFT>::writeGlobalSymbols(uint8_t *Buf) {
// Write the internal symbol table contents to the output symbol table
// pointed by Buf.
auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
for (SymbolBody *Body : Symbols) {
const OutputSectionBase<ELFT> *OutSec = nullptr;
switch (Body->kind()) {
case SymbolBody::DefinedSyntheticKind:
OutSec = &cast<DefinedSynthetic<ELFT>>(Body)->Section;
break;
case SymbolBody::DefinedRegularKind: {
auto *Sym = cast<DefinedRegular<ELFT>>(Body->repl());
if (!Sym->Section.isLive())
continue;
OutSec = Sym->Section.OutSec;
break;
}
case SymbolBody::DefinedCommonKind:
OutSec = Out<ELFT>::Bss;
break;
case SymbolBody::SharedKind: {
if (cast<SharedSymbol<ELFT>>(Body)->needsCopy())
OutSec = Out<ELFT>::Bss;
break;
}
case SymbolBody::UndefinedKind:
case SymbolBody::DefinedAbsoluteKind:
case SymbolBody::LazyKind:
break;
}
StringRef Name = Body->getName();
ESym->st_name = StrTabSec.getOffset(Name);
unsigned char Type = STT_NOTYPE;
uintX_t Size = 0;
if (const auto *EBody = dyn_cast<ELFSymbolBody<ELFT>>(Body)) {
const Elf_Sym &InputSym = EBody->Sym;
Type = InputSym.getType();
Size = InputSym.st_size;
}
ESym->setBindingAndType(getSymbolBinding(Body), Type);
ESym->st_size = Size;
ESym->setVisibility(Body->getVisibility());
ESym->st_value = getSymVA<ELFT>(*Body);
if (isa<DefinedAbsolute<ELFT>>(Body))
ESym->st_shndx = SHN_ABS;
else if (OutSec)
ESym->st_shndx = OutSec->SectionIndex;
++ESym;
}
}
template <class ELFT>
uint8_t SymbolTableSection<ELFT>::getSymbolBinding(SymbolBody *Body) {
uint8_t Visibility = Body->getVisibility();
if (Visibility != STV_DEFAULT && Visibility != STV_PROTECTED)
return STB_LOCAL;
if (const auto *EBody = dyn_cast<ELFSymbolBody<ELFT>>(Body))
return EBody->Sym.getBinding();
return Body->isWeak() ? STB_WEAK : STB_GLOBAL;
}
namespace lld {
namespace elf2 {
template class OutputSectionBase<ELF32LE>;
template class OutputSectionBase<ELF32BE>;
template class OutputSectionBase<ELF64LE>;
template class OutputSectionBase<ELF64BE>;
template class GotPltSection<ELF32LE>;
template class GotPltSection<ELF32BE>;
template class GotPltSection<ELF64LE>;
template class GotPltSection<ELF64BE>;
template class GotSection<ELF32LE>;
template class GotSection<ELF32BE>;
template class GotSection<ELF64LE>;
template class GotSection<ELF64BE>;
template class PltSection<ELF32LE>;
template class PltSection<ELF32BE>;
template class PltSection<ELF64LE>;
template class PltSection<ELF64BE>;
template class RelocationSection<ELF32LE>;
template class RelocationSection<ELF32BE>;
template class RelocationSection<ELF64LE>;
template class RelocationSection<ELF64BE>;
template class InterpSection<ELF32LE>;
template class InterpSection<ELF32BE>;
template class InterpSection<ELF64LE>;
template class InterpSection<ELF64BE>;
template class GnuHashTableSection<ELF32LE>;
template class GnuHashTableSection<ELF32BE>;
template class GnuHashTableSection<ELF64LE>;
template class GnuHashTableSection<ELF64BE>;
template class HashTableSection<ELF32LE>;
template class HashTableSection<ELF32BE>;
template class HashTableSection<ELF64LE>;
template class HashTableSection<ELF64BE>;
template class DynamicSection<ELF32LE>;
template class DynamicSection<ELF32BE>;
template class DynamicSection<ELF64LE>;
template class DynamicSection<ELF64BE>;
template class OutputSection<ELF32LE>;
template class OutputSection<ELF32BE>;
template class OutputSection<ELF64LE>;
template class OutputSection<ELF64BE>;
template class EHOutputSection<ELF32LE>;
template class EHOutputSection<ELF32BE>;
template class EHOutputSection<ELF64LE>;
template class EHOutputSection<ELF64BE>;
template class MergeOutputSection<ELF32LE>;
template class MergeOutputSection<ELF32BE>;
template class MergeOutputSection<ELF64LE>;
template class MergeOutputSection<ELF64BE>;
template class StringTableSection<ELF32LE>;
template class StringTableSection<ELF32BE>;
template class StringTableSection<ELF64LE>;
template class StringTableSection<ELF64BE>;
template class SymbolTableSection<ELF32LE>;
template class SymbolTableSection<ELF32BE>;
template class SymbolTableSection<ELF64LE>;
template class SymbolTableSection<ELF64BE>;
template ELFFile<ELF32LE>::uintX_t getSymVA<ELF32LE>(const SymbolBody &);
template ELFFile<ELF32BE>::uintX_t getSymVA<ELF32BE>(const SymbolBody &);
template ELFFile<ELF64LE>::uintX_t getSymVA<ELF64LE>(const SymbolBody &);
template ELFFile<ELF64BE>::uintX_t getSymVA<ELF64BE>(const SymbolBody &);
template ELFFile<ELF32LE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF32LE> &,
const ELFFile<ELF32LE>::Elf_Rel &);
template ELFFile<ELF32BE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF32BE> &,
const ELFFile<ELF32BE>::Elf_Rel &);
template ELFFile<ELF64LE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF64LE> &,
const ELFFile<ELF64LE>::Elf_Rel &);
template ELFFile<ELF64BE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF64BE> &,
const ELFFile<ELF64BE>::Elf_Rel &);
template ELFFile<ELF32LE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF32LE> &,
const ELFFile<ELF32LE>::Elf_Rela &);
template ELFFile<ELF32BE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF32BE> &,
const ELFFile<ELF32BE>::Elf_Rela &);
template ELFFile<ELF64LE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF64LE> &,
const ELFFile<ELF64LE>::Elf_Rela &);
template ELFFile<ELF64BE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF64BE> &,
const ELFFile<ELF64BE>::Elf_Rela &);
template bool includeInSymtab<ELF32LE>(const SymbolBody &);
template bool includeInSymtab<ELF32BE>(const SymbolBody &);
template bool includeInSymtab<ELF64LE>(const SymbolBody &);
template bool includeInSymtab<ELF64BE>(const SymbolBody &);
template bool shouldKeepInSymtab<ELF32LE>(const ObjectFile<ELF32LE> &,
StringRef,
const ELFFile<ELF32LE>::Elf_Sym &);
template bool shouldKeepInSymtab<ELF32BE>(const ObjectFile<ELF32BE> &,
StringRef,
const ELFFile<ELF32BE>::Elf_Sym &);
template bool shouldKeepInSymtab<ELF64LE>(const ObjectFile<ELF64LE> &,
StringRef,
const ELFFile<ELF64LE>::Elf_Sym &);
template bool shouldKeepInSymtab<ELF64BE>(const ObjectFile<ELF64BE> &,
StringRef,
const ELFFile<ELF64BE>::Elf_Sym &);
}
}
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