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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 "LinkerScript.h"
#include "SymbolTable.h"
#include "Target.h"
#include "lld/Core/Parallel.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/MathExtras.h"
#include <map>
using namespace llvm;
using namespace llvm::dwarf;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
static bool isAlpha(char C) {
return ('a' <= C && C <= 'z') || ('A' <= C && C <= 'Z') || C == '_';
}
static bool isAlnum(char C) { return isAlpha(C) || ('0' <= C && C <= '9'); }
// Returns true if S is valid as a C language identifier.
bool elf::isValidCIdentifier(StringRef S) {
return !S.empty() && isAlpha(S[0]) &&
std::all_of(S.begin() + 1, S.end(), isAlnum);
}
template <class ELFT>
OutputSectionBase<ELFT>::OutputSectionBase(StringRef Name, uint32_t Type,
uintX_t Flags)
: Name(Name) {
memset(&Header, 0, sizeof(Elf_Shdr));
Header.sh_type = Type;
Header.sh_flags = Flags;
}
template <class ELFT>
void OutputSectionBase<ELFT>::writeHeaderTo(Elf_Shdr *Shdr) {
*Shdr = Header;
}
template <class ELFT>
GotPltSection<ELFT>::GotPltSection()
: OutputSectionBase<ELFT>(".got.plt", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE) {
this->Header.sh_addralign = sizeof(uintX_t);
}
template <class ELFT> void GotPltSection<ELFT>::addEntry(SymbolBody &Sym) {
Sym.GotPltIndex = Target->GotPltHeaderEntriesNum + Entries.size();
Entries.push_back(&Sym);
}
template <class ELFT> bool GotPltSection<ELFT>::empty() const {
return Entries.empty();
}
template <class ELFT> void GotPltSection<ELFT>::finalize() {
this->Header.sh_size =
(Target->GotPltHeaderEntriesNum + Entries.size()) * sizeof(uintX_t);
}
template <class ELFT> void GotPltSection<ELFT>::writeTo(uint8_t *Buf) {
Target->writeGotPltHeader(Buf);
Buf += Target->GotPltHeaderEntriesNum * sizeof(uintX_t);
for (const SymbolBody *B : Entries) {
Target->writeGotPlt(Buf, B->getPltVA<ELFT>());
Buf += sizeof(uintX_t);
}
}
template <class ELFT>
GotSection<ELFT>::GotSection()
: OutputSectionBase<ELFT>(".got", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE) {
if (Config->EMachine == EM_MIPS)
this->Header.sh_flags |= SHF_MIPS_GPREL;
this->Header.sh_addralign = sizeof(uintX_t);
}
template <class ELFT> void GotSection<ELFT>::addEntry(SymbolBody &Sym) {
if (Config->EMachine == EM_MIPS) {
// For "true" local symbols which can be referenced from the same module
// only compiler creates two instructions for address loading:
//
// lw $8, 0($gp) # R_MIPS_GOT16
// addi $8, $8, 0 # R_MIPS_LO16
//
// The first instruction loads high 16 bits of the symbol address while
// the second adds an offset. That allows to reduce number of required
// GOT entries because only one global offset table entry is necessary
// for every 64 KBytes of local data. So for local symbols we need to
// allocate number of GOT entries to hold all required "page" addresses.
//
// All global symbols (hidden and regular) considered by compiler uniformly.
// It always generates a single `lw` instruction and R_MIPS_GOT16 relocation
// to load address of the symbol. So for each such symbol we need to
// allocate dedicated GOT entry to store its address.
//
// If a symbol is preemptible we need help of dynamic linker to get its
// final address. The corresponding GOT entries are allocated in the
// "global" part of GOT. Entries for non preemptible global symbol allocated
// in the "local" part of GOT.
//
// See "Global Offset Table" in Chapter 5:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
if (Sym.isLocal()) {
// At this point we do not know final symbol value so to reduce number
// of allocated GOT entries do the following trick. Save all output
// sections referenced by GOT relocations. Then later in the `finalize`
// method calculate number of "pages" required to cover all saved output
// section and allocate appropriate number of GOT entries.
auto *OutSec = cast<DefinedRegular<ELFT>>(&Sym)->Section->OutSec;
MipsOutSections.insert(OutSec);
return;
}
if (!Sym.isPreemptible()) {
// In case of non-local symbols require an entry in the local part
// of MIPS GOT, we set GotIndex to 1 just to accent that this symbol
// has the GOT entry and escape creation more redundant GOT entries.
// FIXME (simon): We can try to store such symbols in the `Entries`
// container. But in that case we have to sort out that container
// and update GotIndex assigned to symbols.
Sym.GotIndex = 1;
++MipsLocalEntries;
return;
}
// All preemptible symbols with MIPS GOT entries should be represented
// in the dynamic symbols table.
Sym.MustBeInDynSym = true;
}
Sym.GotIndex = Entries.size();
Entries.push_back(&Sym);
}
template <class ELFT> bool GotSection<ELFT>::addDynTlsEntry(SymbolBody &Sym) {
if (Sym.hasGlobalDynIndex())
return false;
Sym.GlobalDynIndex = Target->GotHeaderEntriesNum + Entries.size();
// Global Dynamic TLS entries take two GOT slots.
Entries.push_back(&Sym);
Entries.push_back(nullptr);
return true;
}
// Reserves TLS entries for a TLS module ID and a TLS block offset.
// In total it takes two GOT slots.
template <class ELFT> bool GotSection<ELFT>::addTlsIndex() {
if (TlsIndexOff != uint32_t(-1))
return false;
TlsIndexOff = Entries.size() * sizeof(uintX_t);
Entries.push_back(nullptr);
Entries.push_back(nullptr);
return true;
}
template <class ELFT>
typename GotSection<ELFT>::uintX_t
GotSection<ELFT>::getMipsLocalFullAddr(const SymbolBody &B) {
return getMipsLocalEntryAddr(B.getVA<ELFT>());
}
template <class ELFT>
typename GotSection<ELFT>::uintX_t
GotSection<ELFT>::getMipsLocalPageAddr(uintX_t EntryValue) {
// Initialize the entry by the %hi(EntryValue) expression
// but without right-shifting.
return getMipsLocalEntryAddr((EntryValue + 0x8000) & ~0xffff);
}
template <class ELFT>
typename GotSection<ELFT>::uintX_t
GotSection<ELFT>::getMipsLocalEntryAddr(uintX_t EntryValue) {
size_t NewIndex = Target->GotHeaderEntriesNum + MipsLocalGotPos.size();
auto P = MipsLocalGotPos.insert(std::make_pair(EntryValue, NewIndex));
assert(!P.second || MipsLocalGotPos.size() <= MipsLocalEntries);
return this->getVA() + P.first->second * sizeof(uintX_t);
}
template <class ELFT>
typename GotSection<ELFT>::uintX_t
GotSection<ELFT>::getGlobalDynAddr(const SymbolBody &B) const {
return this->getVA() + B.GlobalDynIndex * 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 {
return Target->GotHeaderEntriesNum + MipsLocalEntries;
}
template <class ELFT> void GotSection<ELFT>::finalize() {
for (const OutputSectionBase<ELFT> *OutSec : MipsOutSections) {
// Calculate an upper bound of MIPS GOT entries required to store page
// addresses of local symbols. We assume the worst case - each 64kb
// page of the output section has at least one GOT relocation against it.
// Add 0x8000 to the section's size because the page address stored
// in the GOT entry is calculated as (value + 0x8000) & ~0xffff.
MipsLocalEntries += (OutSec->getSize() + 0x8000 + 0xfffe) / 0xffff;
}
this->Header.sh_size =
(Target->GotHeaderEntriesNum + MipsLocalEntries + Entries.size()) *
sizeof(uintX_t);
}
template <class ELFT> void GotSection<ELFT>::writeTo(uint8_t *Buf) {
Target->writeGotHeader(Buf);
for (std::pair<uintX_t, size_t> &L : MipsLocalGotPos) {
uint8_t *Entry = Buf + L.second * sizeof(uintX_t);
write<uintX_t, ELFT::TargetEndianness, sizeof(uintX_t)>(Entry, L.first);
}
Buf += Target->GotHeaderEntriesNum * sizeof(uintX_t);
Buf += MipsLocalEntries * 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 && B->isPreemptible())
continue; // The dynamic linker will take care of it.
uintX_t VA = B->getVA<ELFT>();
write<uintX_t, ELFT::TargetEndianness, sizeof(uintX_t)>(Entry, VA);
}
}
template <class ELFT>
PltSection<ELFT>::PltSection()
: OutputSectionBase<ELFT>(".plt", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR) {
this->Header.sh_addralign = 16;
}
template <class ELFT> void PltSection<ELFT>::writeTo(uint8_t *Buf) {
size_t Off = 0;
if (Target->UseLazyBinding) {
// At beginning of PLT, we have code to call the dynamic linker
// to resolve dynsyms at runtime. Write such code.
Target->writePltZero(Buf);
Off += Target->PltZeroSize;
}
for (auto &I : Entries) {
const SymbolBody *B = I.first;
unsigned RelOff = I.second;
uint64_t Got =
Target->UseLazyBinding ? B->getGotPltVA<ELFT>() : B->getGotVA<ELFT>();
uint64_t Plt = this->getVA() + Off;
Target->writePlt(Buf + Off, Got, Plt, B->PltIndex, RelOff);
Off += Target->PltEntrySize;
}
}
template <class ELFT> void PltSection<ELFT>::addEntry(SymbolBody &Sym) {
Sym.PltIndex = Entries.size();
unsigned RelOff = Target->UseLazyBinding
? Out<ELFT>::RelaPlt->getRelocOffset()
: Out<ELFT>::RelaDyn->getRelocOffset();
Entries.push_back(std::make_pair(&Sym, RelOff));
}
template <class ELFT> void PltSection<ELFT>::finalize() {
this->Header.sh_size =
Target->PltZeroSize + Entries.size() * Target->PltEntrySize;
}
template <class ELFT>
RelocationSection<ELFT>::RelocationSection(StringRef Name)
: OutputSectionBase<ELFT>(Name, Config->Rela ? SHT_RELA : SHT_REL,
SHF_ALLOC) {
this->Header.sh_entsize = Config->Rela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
this->Header.sh_addralign = sizeof(uintX_t);
}
template <class ELFT>
void RelocationSection<ELFT>::addReloc(const DynamicReloc<ELFT> &Reloc) {
SymbolBody *Sym = Reloc.Sym;
if (!Reloc.UseSymVA && Sym)
Sym->MustBeInDynSym = true;
Relocs.push_back(Reloc);
}
template <class ELFT>
typename ELFT::uint DynamicReloc<ELFT>::getOffset() const {
switch (OKind) {
case Off_GTlsIndex:
return Out<ELFT>::Got->getGlobalDynAddr(*Sym);
case Off_GTlsOffset:
return Out<ELFT>::Got->getGlobalDynAddr(*Sym) + sizeof(uintX_t);
case Off_LTlsIndex:
return Out<ELFT>::Got->getTlsIndexVA();
case Off_Sec:
return OffsetSec->getOffset(OffsetInSec) + OffsetSec->OutSec->getVA();
case Off_Bss:
return cast<SharedSymbol<ELFT>>(Sym)->OffsetInBss + Out<ELFT>::Bss->getVA();
case Off_Got:
return Sym->getGotVA<ELFT>();
case Off_GotPlt:
return Sym->getGotPltVA<ELFT>();
}
llvm_unreachable("invalid offset kind");
}
template <class ELFT> void RelocationSection<ELFT>::writeTo(uint8_t *Buf) {
for (const DynamicReloc<ELFT> &Rel : Relocs) {
auto *P = reinterpret_cast<Elf_Rela *>(Buf);
Buf += Config->Rela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
SymbolBody *Sym = Rel.Sym;
if (Config->Rela)
P->r_addend = Rel.UseSymVA ? Sym->getVA<ELFT>(Rel.Addend) : Rel.Addend;
P->r_offset = Rel.getOffset();
uint32_t SymIdx = (!Rel.UseSymVA && Sym) ? Sym->DynsymIndex : 0;
P->setSymbolAndType(SymIdx, Rel.Type, Config->Mips64EL);
}
}
template <class ELFT> unsigned RelocationSection<ELFT>::getRelocOffset() {
return this->Header.sh_entsize * Relocs.size();
}
template <class ELFT> void RelocationSection<ELFT>::finalize() {
this->Header.sh_link = Static ? Out<ELFT>::SymTab->SectionIndex
: Out<ELFT>::DynSymTab->SectionIndex;
this->Header.sh_size = Relocs.size() * this->Header.sh_entsize;
}
template <class ELFT>
InterpSection<ELFT>::InterpSection()
: OutputSectionBase<ELFT>(".interp", SHT_PROGBITS, SHF_ALLOC) {
this->Header.sh_size = Config->DynamicLinker.size() + 1;
this->Header.sh_addralign = 1;
}
template <class ELFT> void InterpSection<ELFT>::writeTo(uint8_t *Buf) {
StringRef S = Config->DynamicLinker;
memcpy(Buf, S.data(), S.size());
}
template <class ELFT>
HashTableSection<ELFT>::HashTableSection()
: OutputSectionBase<ELFT>(".hash", SHT_HASH, 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 (const std::pair<SymbolBody *, unsigned> &P :
Out<ELFT>::DynSymTab->getSymbols()) {
SymbolBody *Body = P.first;
StringRef Name = Body->getName();
unsigned I = Body->DynsymIndex;
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", SHT_GNU_HASH, SHF_ALLOC) {
this->Header.sh_entsize = ELFT::Is64Bits ? 0 : 4;
this->Header.sh_addralign = sizeof(uintX_t);
}
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 = Symbols.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 (Symbols.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() - Symbols.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 SymbolData &Sym : Symbols) {
size_t Pos = (Sym.Hash / C) & (MaskWords - 1);
uintX_t V = (uintX_t(1) << (Sym.Hash % C)) |
(uintX_t(1) << ((Sym.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 SymbolData &Sym : Symbols) {
int Bucket = Sym.Hash % NBuckets;
assert(PrevBucket <= Bucket);
if (Bucket != PrevBucket) {
Buckets[Bucket] = Sym.Body->DynsymIndex;
PrevBucket = Bucket;
if (I > 0)
Values[I - 1] |= 1;
}
Values[I] = Sym.Hash & ~1;
++I;
}
if (I > 0)
Values[I - 1] |= 1;
}
static bool includeInGnuHashTable(SymbolBody *B) {
// Assume that includeInDynsym() is already checked.
return !B->isUndefined();
}
// Add symbols to this symbol hash table. Note that this function
// destructively sort a given vector -- which is needed because
// GNU-style hash table places some sorting requirements.
template <class ELFT>
void GnuHashTableSection<ELFT>::addSymbols(
std::vector<std::pair<SymbolBody *, size_t>> &V) {
auto Mid = std::stable_partition(V.begin(), V.end(),
[](std::pair<SymbolBody *, size_t> &P) {
return !includeInGnuHashTable(P.first);
});
if (Mid == V.end())
return;
for (auto I = Mid, E = V.end(); I != E; ++I) {
SymbolBody *B = I->first;
size_t StrOff = I->second;
Symbols.push_back({B, StrOff, hashGnu(B->getName())});
}
unsigned NBuckets = calcNBuckets(Symbols.size());
std::stable_sort(Symbols.begin(), Symbols.end(),
[&](const SymbolData &L, const SymbolData &R) {
return L.Hash % NBuckets < R.Hash % NBuckets;
});
V.erase(Mid, V.end());
for (const SymbolData &Sym : Symbols)
V.push_back({Sym.Body, Sym.STName});
}
template <class ELFT>
DynamicSection<ELFT>::DynamicSection(SymbolTable<ELFT> &SymTab)
: OutputSectionBase<ELFT>(".dynamic", SHT_DYNAMIC, SHF_ALLOC | SHF_WRITE),
SymTab(SymTab) {
Elf_Shdr &Header = this->Header;
Header.sh_addralign = sizeof(uintX_t);
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 = 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;
auto Add = [=](Entry E) { Entries.push_back(E); };
// Add strings. We know that these are the last strings to be added to
// DynStrTab and doing this here allows this function to set DT_STRSZ.
if (!Config->RPath.empty())
Add({Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH,
Out<ELFT>::DynStrTab->addString(Config->RPath)});
for (const std::unique_ptr<SharedFile<ELFT>> &F : SymTab.getSharedFiles())
if (F->isNeeded())
Add({DT_NEEDED, Out<ELFT>::DynStrTab->addString(F->getSoName())});
if (!Config->SoName.empty())
Add({DT_SONAME, Out<ELFT>::DynStrTab->addString(Config->SoName)});
Out<ELFT>::DynStrTab->finalize();
if (Out<ELFT>::RelaDyn->hasRelocs()) {
bool IsRela = Config->Rela;
Add({IsRela ? DT_RELA : DT_REL, Out<ELFT>::RelaDyn});
Add({IsRela ? DT_RELASZ : DT_RELSZ, Out<ELFT>::RelaDyn->getSize()});
Add({IsRela ? DT_RELAENT : DT_RELENT,
uintX_t(IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel))});
}
if (Out<ELFT>::RelaPlt && Out<ELFT>::RelaPlt->hasRelocs()) {
Add({DT_JMPREL, Out<ELFT>::RelaPlt});
Add({DT_PLTRELSZ, Out<ELFT>::RelaPlt->getSize()});
Add({Config->EMachine == EM_MIPS ? DT_MIPS_PLTGOT : DT_PLTGOT,
Out<ELFT>::GotPlt});
Add({DT_PLTREL, uint64_t(Config->Rela ? DT_RELA : DT_REL)});
}
Add({DT_SYMTAB, Out<ELFT>::DynSymTab});
Add({DT_SYMENT, sizeof(Elf_Sym)});
Add({DT_STRTAB, Out<ELFT>::DynStrTab});
Add({DT_STRSZ, Out<ELFT>::DynStrTab->getSize()});
if (Out<ELFT>::GnuHashTab)
Add({DT_GNU_HASH, Out<ELFT>::GnuHashTab});
if (Out<ELFT>::HashTab)
Add({DT_HASH, Out<ELFT>::HashTab});
if (PreInitArraySec) {
Add({DT_PREINIT_ARRAY, PreInitArraySec});
Add({DT_PREINIT_ARRAYSZ, PreInitArraySec->getSize()});
}
if (InitArraySec) {
Add({DT_INIT_ARRAY, InitArraySec});
Add({DT_INIT_ARRAYSZ, (uintX_t)InitArraySec->getSize()});
}
if (FiniArraySec) {
Add({DT_FINI_ARRAY, FiniArraySec});
Add({DT_FINI_ARRAYSZ, (uintX_t)FiniArraySec->getSize()});
}
if (SymbolBody *B = SymTab.find(Config->Init))
Add({DT_INIT, B});
if (SymbolBody *B = SymTab.find(Config->Fini))
Add({DT_FINI, B});
uint32_t DtFlags = 0;
uint32_t DtFlags1 = 0;
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)
Add({DT_FLAGS, DtFlags});
if (DtFlags1)
Add({DT_FLAGS_1, DtFlags1});
if (!Config->Entry.empty())
Add({DT_DEBUG, (uint64_t)0});
if (Config->EMachine == EM_MIPS) {
Add({DT_MIPS_RLD_VERSION, 1});
Add({DT_MIPS_FLAGS, RHF_NOTPOT});
Add({DT_MIPS_BASE_ADDRESS, (uintX_t)Target->getVAStart()});
Add({DT_MIPS_SYMTABNO, Out<ELFT>::DynSymTab->getNumSymbols()});
Add({DT_MIPS_LOCAL_GOTNO, Out<ELFT>::Got->getMipsLocalEntriesNum()});
if (const SymbolBody *B = Out<ELFT>::Got->getMipsFirstGlobalEntry())
Add({DT_MIPS_GOTSYM, B->DynsymIndex});
else
Add({DT_MIPS_GOTSYM, Out<ELFT>::DynSymTab->getNumSymbols()});
Add({DT_PLTGOT, Out<ELFT>::Got});
if (Out<ELFT>::MipsRldMap)
Add({DT_MIPS_RLD_MAP, Out<ELFT>::MipsRldMap});
}
// +1 for DT_NULL
Header.sh_size = (Entries.size() + 1) * Header.sh_entsize;
}
template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *Buf) {
auto *P = reinterpret_cast<Elf_Dyn *>(Buf);
for (const Entry &E : Entries) {
P->d_tag = E.Tag;
switch (E.Kind) {
case Entry::SecAddr:
P->d_un.d_ptr = E.OutSec->getVA();
break;
case Entry::SymAddr:
P->d_un.d_ptr = E.Sym->template getVA<ELFT>();
break;
case Entry::PlainInt:
P->d_un.d_val = E.Val;
break;
}
++P;
}
}
template <class ELFT>
EhFrameHeader<ELFT>::EhFrameHeader()
: OutputSectionBase<ELFT>(".eh_frame_hdr", llvm::ELF::SHT_PROGBITS,
SHF_ALLOC) {
// It's a 4 bytes of header + pointer to the contents of the .eh_frame section
// + the number of FDE pointers in the table.
this->Header.sh_size = 12;
}
// We have to get PC values of FDEs. They depend on relocations
// which are target specific, so we run this code after performing
// all relocations. We read the values from ouput buffer according to the
// encoding given for FDEs. Return value is an offset to the initial PC value
// for the FDE.
template <class ELFT>
typename EhFrameHeader<ELFT>::uintX_t
EhFrameHeader<ELFT>::getFdePc(uintX_t EhVA, const FdeData &F) {
const endianness E = ELFT::TargetEndianness;
uint8_t Size = F.Enc & 0x7;
if (Size == DW_EH_PE_absptr)
Size = sizeof(uintX_t) == 8 ? DW_EH_PE_udata8 : DW_EH_PE_udata4;
uint64_t PC;
switch (Size) {
case DW_EH_PE_udata2:
PC = read16<E>(F.PCRel);
break;
case DW_EH_PE_udata4:
PC = read32<E>(F.PCRel);
break;
case DW_EH_PE_udata8:
PC = read64<E>(F.PCRel);
break;
default:
fatal("unknown FDE size encoding");
}
switch (F.Enc & 0x70) {
case DW_EH_PE_absptr:
return PC;
case DW_EH_PE_pcrel:
return PC + EhVA + F.Off + 8;
default:
fatal("unknown FDE size relative encoding");
}
}
template <class ELFT> void EhFrameHeader<ELFT>::writeTo(uint8_t *Buf) {
const endianness E = ELFT::TargetEndianness;
const uint8_t Header[] = {1, DW_EH_PE_pcrel | DW_EH_PE_sdata4,
DW_EH_PE_udata4,
DW_EH_PE_datarel | DW_EH_PE_sdata4};
memcpy(Buf, Header, sizeof(Header));
uintX_t EhVA = Sec->getVA();
uintX_t VA = this->getVA();
uintX_t EhOff = EhVA - VA - 4;
write32<E>(Buf + 4, EhOff);
write32<E>(Buf + 8, this->FdeList.size());
Buf += 12;
// InitialPC -> Offset in .eh_frame, sorted by InitialPC.
std::map<uintX_t, size_t> PcToOffset;
for (const FdeData &F : FdeList)
PcToOffset[getFdePc(EhVA, F)] = F.Off;
for (auto &I : PcToOffset) {
// The first four bytes are an offset to the initial PC value for the FDE.
write32<E>(Buf, I.first - VA);
// The last four bytes are an offset to the FDE data itself.
write32<E>(Buf + 4, EhVA + I.second - VA);
Buf += 8;
}
}
template <class ELFT>
void EhFrameHeader<ELFT>::assignEhFrame(EHOutputSection<ELFT> *Sec) {
assert((!this->Sec || this->Sec == Sec) &&
"multiple .eh_frame sections not supported for .eh_frame_hdr");
Live = Config->EhFrameHdr;
this->Sec = Sec;
}
template <class ELFT>
void EhFrameHeader<ELFT>::addFde(uint8_t Enc, size_t Off, uint8_t *PCRel) {
if (Live && (Enc & 0xF0) == DW_EH_PE_datarel)
fatal("DW_EH_PE_datarel encoding unsupported for FDEs by .eh_frame_hdr");
FdeList.push_back(FdeData{Enc, Off, PCRel});
}
template <class ELFT> void EhFrameHeader<ELFT>::reserveFde() {
// Each FDE entry is 8 bytes long:
// The first four bytes are an offset to the initial PC value for the FDE. The
// last four byte are an offset to the FDE data itself.
this->Header.sh_size += 8;
}
template <class ELFT>
OutputSection<ELFT>::OutputSection(StringRef Name, uint32_t Type, uintX_t Flags)
: OutputSectionBase<ELFT>(Name, Type, Flags) {
if (Type == SHT_RELA)
this->Header.sh_entsize = sizeof(Elf_Rela);
else if (Type == SHT_REL)
this->Header.sh_entsize = sizeof(Elf_Rel);
}
template <class ELFT> void OutputSection<ELFT>::finalize() {
uint32_t Type = this->Header.sh_type;
if (Type != SHT_RELA && Type != SHT_REL)
return;
this->Header.sh_link = Out<ELFT>::SymTab->SectionIndex;
// sh_info for SHT_REL[A] sections should contain the section header index of
// the section to which the relocation applies.
InputSectionBase<ELFT> *S = Sections[0]->getRelocatedSection();
this->Header.sh_info = S->OutSec->SectionIndex;
}
template <class ELFT>
void OutputSection<ELFT>::addSection(InputSectionBase<ELFT> *C) {
assert(C->Live);
auto *S = cast<InputSection<ELFT>>(C);
Sections.push_back(S);
S->OutSec = this;
this->updateAlign(S->Align);
}
// If an input string is in the form of "foo.N" where N is a number,
// return N. Otherwise, returns 65536, which is one greater than the
// lowest priority.
static int getPriority(StringRef S) {
size_t Pos = S.rfind('.');
if (Pos == StringRef::npos)
return 65536;
int V;
if (S.substr(Pos + 1).getAsInteger(10, V))
return 65536;
return V;
}
// This function is called after we sort input sections
// and scan relocations to setup sections' offsets.
template <class ELFT> void OutputSection<ELFT>::assignOffsets() {
uintX_t Off = this->Header.sh_size;
for (InputSection<ELFT> *S : Sections) {
Off = alignTo(Off, S->Align);
S->OutSecOff = Off;
Off += S->getSize();
}
this->Header.sh_size = Off;
}
// Sorts input sections by section name suffixes, so that .foo.N comes
// before .foo.M if N < M. Used to sort .{init,fini}_array.N sections.
// We want to keep the original order if the priorities are the same
// because the compiler keeps the original initialization order in a
// translation unit and we need to respect that.
// For more detail, read the section of the GCC's manual about init_priority.
template <class ELFT> void OutputSection<ELFT>::sortInitFini() {
// Sort sections by priority.
typedef std::pair<int, InputSection<ELFT> *> Pair;
auto Comp = [](const Pair &A, const Pair &B) { return A.first < B.first; };
std::vector<Pair> V;
for (InputSection<ELFT> *S : Sections)
V.push_back({getPriority(S->getSectionName()), S});
std::stable_sort(V.begin(), V.end(), Comp);
Sections.clear();
for (Pair &P : V)
Sections.push_back(P.second);
}
// Returns true if S matches /Filename.?\.o$/.
static bool isCrtBeginEnd(StringRef S, StringRef Filename) {
if (!S.endswith(".o"))
return false;
S = S.drop_back(2);
if (S.endswith(Filename))
return true;
return !S.empty() && S.drop_back().endswith(Filename);
}
static bool isCrtbegin(StringRef S) { return isCrtBeginEnd(S, "crtbegin"); }
static bool isCrtend(StringRef S) { return isCrtBeginEnd(S, "crtend"); }
// .ctors and .dtors are sorted by this priority from highest to lowest.
//
// 1. The section was contained in crtbegin (crtbegin contains
// some sentinel value in its .ctors and .dtors so that the runtime
// can find the beginning of the sections.)
//
// 2. The section has an optional priority value in the form of ".ctors.N"
// or ".dtors.N" where N is a number. Unlike .{init,fini}_array,
// they are compared as string rather than number.
//
// 3. The section is just ".ctors" or ".dtors".
//
// 4. The section was contained in crtend, which contains an end marker.
//
// In an ideal world, we don't need this function because .init_array and
// .ctors are duplicate features (and .init_array is newer.) However, there
// are too many real-world use cases of .ctors, so we had no choice to
// support that with this rather ad-hoc semantics.
template <class ELFT>
static bool compCtors(const InputSection<ELFT> *A,
const InputSection<ELFT> *B) {
bool BeginA = isCrtbegin(A->getFile()->getName());
bool BeginB = isCrtbegin(B->getFile()->getName());
if (BeginA != BeginB)
return BeginA;
bool EndA = isCrtend(A->getFile()->getName());
bool EndB = isCrtend(B->getFile()->getName());
if (EndA != EndB)
return EndB;
StringRef X = A->getSectionName();
StringRef Y = B->getSectionName();
assert(X.startswith(".ctors") || X.startswith(".dtors"));
assert(Y.startswith(".ctors") || Y.startswith(".dtors"));
X = X.substr(6);
Y = Y.substr(6);
if (X.empty() && Y.empty())
return false;
return X < Y;
}
// Sorts input sections by the special rules for .ctors and .dtors.
// Unfortunately, the rules are different from the one for .{init,fini}_array.
// Read the comment above.
template <class ELFT> void OutputSection<ELFT>::sortCtorsDtors() {
std::stable_sort(Sections.begin(), Sections.end(), compCtors<ELFT>);
}
static void fill(uint8_t *Buf, size_t Size, ArrayRef<uint8_t> A) {
size_t I = 0;
for (; I + A.size() < Size; I += A.size())
memcpy(Buf + I, A.data(), A.size());
memcpy(Buf + I, A.data(), Size - I);
}
template <class ELFT> void OutputSection<ELFT>::writeTo(uint8_t *Buf) {
ArrayRef<uint8_t> Filler = Script->getFiller(this->Name);
if (!Filler.empty())
fill(Buf, this->getSize(), Filler);
if (Config->Threads) {
parallel_for_each(Sections.begin(), Sections.end(),
[=](InputSection<ELFT> *C) { C->writeTo(Buf); });
} else {
for (InputSection<ELFT> *C : Sections)
C->writeTo(Buf);
}
}
template <class ELFT>
EHOutputSection<ELFT>::EHOutputSection(StringRef Name, uint32_t Type,
uintX_t Flags)
: OutputSectionBase<ELFT>(Name, Type, Flags) {
Out<ELFT>::EhFrameHdr->assignEhFrame(this);
}
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) {}
// Read a byte and advance D by one byte.
static uint8_t readByte(ArrayRef<uint8_t> &D) {
if (D.empty())
fatal("corrupted or unsupported CIE information");
uint8_t B = D.front();
D = D.slice(1);
return B;
}
static void skipLeb128(ArrayRef<uint8_t> &D) {
while (!D.empty()) {
uint8_t Val = D.front();
D = D.slice(1);
if ((Val & 0x80) == 0)
return;
}
fatal("corrupted or unsupported CIE information");
}
template <class ELFT> static size_t getAugPSize(unsigned Enc) {
switch (Enc & 0x0f) {
case DW_EH_PE_absptr:
case DW_EH_PE_signed:
return ELFT::Is64Bits ? 8 : 4;
case DW_EH_PE_udata2:
case DW_EH_PE_sdata2:
return 2;
case DW_EH_PE_udata4:
case DW_EH_PE_sdata4:
return 4;
case DW_EH_PE_udata8:
case DW_EH_PE_sdata8:
return 8;
}
fatal("unknown FDE encoding");
}
template <class ELFT> static void skipAugP(ArrayRef<uint8_t> &D) {
uint8_t Enc = readByte(D);
if ((Enc & 0xf0) == DW_EH_PE_aligned)
fatal("DW_EH_PE_aligned encoding is not supported");
size_t Size = getAugPSize<ELFT>(Enc);
if (Size >= D.size())
fatal("corrupted CIE");
D = D.slice(Size);
}
template <class ELFT>
uint8_t EHOutputSection<ELFT>::getFdeEncoding(ArrayRef<uint8_t> D) {
if (D.size() < 8)
fatal("CIE too small");
D = D.slice(8);
uint8_t Version = readByte(D);
if (Version != 1 && Version != 3)
fatal("FDE version 1 or 3 expected, but got " + Twine((unsigned)Version));
const unsigned char *AugEnd = std::find(D.begin() + 1, D.end(), '\0');
if (AugEnd == D.end())
fatal("corrupted CIE");
StringRef Aug(reinterpret_cast<const char *>(D.begin()), AugEnd - D.begin());
D = D.slice(Aug.size() + 1);
// Code alignment factor should always be 1 for .eh_frame.
if (readByte(D) != 1)
fatal("CIE code alignment must be 1");
// Skip data alignment factor.
skipLeb128(D);
// Skip the return address register. In CIE version 1 this is a single
// byte. In CIE version 3 this is an unsigned LEB128.
if (Version == 1)
readByte(D);
else
skipLeb128(D);
// We only care about an 'R' value, but other records may precede an 'R'
// record. Records are not in TLV (type-length-value) format, so we need
// to teach the linker how to skip records for each type.
for (char C : Aug) {
if (C == 'R')
return readByte(D);
if (C == 'z') {
skipLeb128(D);
continue;
}
if (C == 'P') {
skipAugP<ELFT>(D);
continue;
}
if (C == 'L') {
readByte(D);
continue;
}
fatal("unknown .eh_frame augmentation string: " + Aug);
}
return DW_EH_PE_absptr;
}
template <class ELFT>
static typename ELFT::uint readEntryLength(ArrayRef<uint8_t> D) {
const endianness E = ELFT::TargetEndianness;
if (D.size() < 4)
fatal("CIE/FDE too small");
// First 4 bytes of CIE/FDE is the size of the record.
// If it is 0xFFFFFFFF, the next 8 bytes contain the size instead.
uint64_t V = read32<E>(D.data());
if (V < UINT32_MAX) {
uint64_t Len = V + 4;
if (Len > D.size())
fatal("CIE/FIE ends past the end of the section");
return Len;
}
if (D.size() < 12)
fatal("CIE/FDE too small");
V = read64<E>(D.data() + 4);
uint64_t Len = V + 12;
if (Len < V || D.size() < Len)
fatal("CIE/FIE ends past the end of the section");
return Len;
}
template <class ELFT>
template <class RelTy>
void EHOutputSection<ELFT>::addSectionAux(EHInputSection<ELFT> *S,
iterator_range<const RelTy *> Rels) {
const endianness E = ELFT::TargetEndianness;
S->OutSec = this;
this->updateAlign(S->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()) {
unsigned Index = S->Offsets.size();
S->Offsets.push_back(std::make_pair(Offset, -1));
uintX_t Length = readEntryLength<ELFT>(D);
// If CIE/FDE data length is zero then Length is 4, this
// shall be considered a terminator and processing shall end.
if (Length == 4)
break;
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);
if (Config->EhFrameHdr)
C.FdeEncoding = getFdeEncoding(D);
SymbolBody *Personality = nullptr;
if (HasReloc) {
uint32_t SymIndex = RelI->getSymbol(Config->Mips64EL);
Personality = &S->getFile()->getSymbolBody(SymIndex).repl();
}
std::pair<StringRef, SymbolBody *> CieInfo(Entry, Personality);
auto P = CieMap.insert(std::make_pair(CieInfo, Cies.size()));
if (P.second) {
Cies.push_back(C);
this->Header.sh_size += alignTo(Length, sizeof(uintX_t));
}
OffsetToIndex[Offset] = P.first->second;
} else {
if (!HasReloc)
fatal("FDE doesn't reference another section");
InputSectionBase<ELFT> *Target = S->getRelocTarget(*RelI);
if (Target && Target->Live) {
uint32_t CieOffset = Offset + 4 - ID;
auto I = OffsetToIndex.find(CieOffset);
if (I == OffsetToIndex.end())
fatal("invalid CIE reference");
Cies[I->second].Fdes.push_back(EHRegion<ELFT>(S, Index));
Out<ELFT>::EhFrameHdr->reserveFde();
this->Header.sh_size += alignTo(Length, sizeof(uintX_t));
}
}
Offset = NextOffset;
D = D.slice(Length);
}
}
template <class ELFT>
void EHOutputSection<ELFT>::addSection(InputSectionBase<ELFT> *C) {
auto *S = cast<EHInputSection<ELFT>>(C);
const Elf_Shdr *RelSec = S->RelocSection;
if (!RelSec) {
addSectionAux(S, make_range<const Elf_Rela *>(nullptr, nullptr));
return;
}
ELFFile<ELFT> &Obj = S->getFile()->getObj();
if (RelSec->sh_type == SHT_RELA)
addSectionAux(S, Obj.relas(RelSec));
else
addSectionAux(S, Obj.rels(RelSec));
}
template <class ELFT>
static typename ELFT::uint writeAlignedCieOrFde(StringRef Data, uint8_t *Buf) {
typedef typename ELFT::uint uintX_t;
const endianness E = ELFT::TargetEndianness;
uint64_t Len = alignTo(Data.size(), sizeof(uintX_t));
write32<E>(Buf, Len - 4);
memcpy(Buf + 4, Data.data() + 4, Data.size() - 4);
return Len;
}
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;
uintX_t CIELen = writeAlignedCieOrFde<ELFT>(C.data(), Buf + Offset);
C.S->Offsets[C.Index].second = Offset;
Offset += CIELen;
for (const EHRegion<ELFT> &F : C.Fdes) {
uintX_t Len = writeAlignedCieOrFde<ELFT>(F.data(), Buf + Offset);
write32<E>(Buf + Offset + 4, Offset + 4 - CieOffset); // Pointer
F.S->Offsets[F.Index].second = Offset;
Out<ELFT>::EhFrameHdr->addFde(C.FdeEncoding, Offset, Buf + Offset + 8);
Offset += Len;
}
}
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 Type,
uintX_t Flags, uintX_t Alignment)
: OutputSectionBase<ELFT>(Name, Type, Flags),
Builder(llvm::StringTableBuilder::RAW, Alignment) {}
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(InputSectionBase<ELFT> *C) {
auto *S = cast<MergeInputSection<ELFT>>(C);
S->OutSec = this;
this->updateAlign(S->Align);
ArrayRef<uint8_t> D = S->getSectionData();
StringRef Data((const char *)D.data(), D.size());
uintX_t EntSize = S->getSectionHdr()->sh_entsize;
this->Header.sh_entsize = EntSize;
// If this is of type string, the contents are null-terminated strings.
if (this->Header.sh_flags & SHF_STRINGS) {
uintX_t Offset = 0;
while (!Data.empty()) {
size_t End = findNull(Data, EntSize);
if (End == StringRef::npos)
fatal("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;
}
return;
}
// If this is not of type string, every entry has the same size.
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(I, OutputOffset));
}
}
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, SHT_STRTAB,
Dynamic ? (uintX_t)SHF_ALLOC : 0),
Dynamic(Dynamic) {
this->Header.sh_addralign = 1;
}
// Adds a string to the string table. If HashIt is true we hash and check for
// duplicates. It is optional because the name of global symbols are already
// uniqued and hashing them again has a big cost for a small value: uniquing
// them with some other string that happens to be the same.
template <class ELFT>
unsigned StringTableSection<ELFT>::addString(StringRef S, bool HashIt) {
if (HashIt) {
auto R = StringMap.insert(std::make_pair(S, Size));
if (!R.second)
return R.first->second;
}
unsigned Ret = Size;
Size += S.size() + 1;
Strings.push_back(S);
return Ret;
}
template <class ELFT> void StringTableSection<ELFT>::writeTo(uint8_t *Buf) {
// ELF string tables start with NUL byte, so advance the pointer by one.
++Buf;
for (StringRef S : Strings) {
memcpy(Buf, S.data(), S.size());
Buf += S.size() + 1;
}
}
template <class ELFT>
SymbolTableSection<ELFT>::SymbolTableSection(
SymbolTable<ELFT> &Table, StringTableSection<ELFT> &StrTabSec)
: OutputSectionBase<ELFT>(StrTabSec.isDynamic() ? ".dynsym" : ".symtab",
StrTabSec.isDynamic() ? SHT_DYNSYM : SHT_SYMTAB,
StrTabSec.isDynamic() ? (uintX_t)SHF_ALLOC : 0),
StrTabSec(StrTabSec), Table(Table) {
this->Header.sh_entsize = sizeof(Elf_Sym);
this->Header.sh_addralign = sizeof(uintX_t);
}
// 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(const std::pair<SymbolBody *, unsigned> &L,
const std::pair<SymbolBody *, unsigned> &R) {
// Sort entries related to non-local preemptible symbols by GOT indexes.
// All other entries go to the first part of GOT in arbitrary order.
bool LIsInLocalGot = !L.first->isInGot() || !L.first->isPreemptible();
bool RIsInLocalGot = !R.first->isInGot() || !R.first->isPreemptible();
if (LIsInLocalGot || RIsInLocalGot)
return !RIsInLocalGot;
return L.first->GotIndex < R.first->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 (Config->Relocatable) {
size_t I = NumLocals;
for (const std::pair<SymbolBody *, size_t> &P : Symbols)
P.first->DynsymIndex = ++I;
return;
}
if (!StrTabSec.isDynamic()) {
std::stable_sort(Symbols.begin(), Symbols.end(),
[](const std::pair<SymbolBody *, unsigned> &L,
const std::pair<SymbolBody *, unsigned> &R) {
return getSymbolBinding(L.first) == STB_LOCAL &&
getSymbolBinding(R.first) != 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 (const std::pair<SymbolBody *, size_t> &P : Symbols)
P.first->DynsymIndex = ++I;
}
template <class ELFT>
void SymbolTableSection<ELFT>::addSymbol(SymbolBody *B) {
Symbols.push_back({B, StrTabSec.addString(B->getName(), false)});
}
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()) {
for (const std::pair<const DefinedRegular<ELFT> *, size_t> &P :
File->KeptLocalSyms) {
const DefinedRegular<ELFT> &Body = *P.first;
InputSectionBase<ELFT> *Section = Body.Section;
auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
if (!Section) {
ESym->st_shndx = SHN_ABS;
ESym->st_value = Body.Value;
} else {
const OutputSectionBase<ELFT> *OutSec = Section->OutSec;
ESym->st_shndx = OutSec->SectionIndex;
ESym->st_value = OutSec->getVA() + Section->getOffset(Body);
}
ESym->st_name = P.second;
ESym->st_size = Body.template getSize<ELFT>();
ESym->setBindingAndType(Body.Binding, Body.Type);
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 (const std::pair<SymbolBody *, size_t> &P : Symbols) {
SymbolBody *Body = P.first;
size_t StrOff = P.second;
uint8_t Type = Body->Type;
uintX_t Size = Body->getSize<ELFT>();
ESym->setBindingAndType(getSymbolBinding(Body), Type);
ESym->st_size = Size;
ESym->st_name = StrOff;
ESym->setVisibility(Body->getVisibility());
ESym->st_value = Body->getVA<ELFT>();
if (const OutputSectionBase<ELFT> *OutSec = getOutputSection(Body))
ESym->st_shndx = OutSec->SectionIndex;
else if (isa<DefinedRegular<ELFT>>(Body))
ESym->st_shndx = SHN_ABS;
// On MIPS we need to mark symbol which has a PLT entry and requires pointer
// equality by STO_MIPS_PLT flag. That is necessary to help dynamic linker
// distinguish such symbols and MIPS lazy-binding stubs.
// https://sourceware.org/ml/binutils/2008-07/txt00000.txt
if (Config->EMachine == EM_MIPS && Body->isInPlt() &&
Body->NeedsCopyOrPltAddr)
ESym->st_other |= STO_MIPS_PLT;
++ESym;
}
}
template <class ELFT>
const OutputSectionBase<ELFT> *
SymbolTableSection<ELFT>::getOutputSection(SymbolBody *Sym) {
switch (Sym->kind()) {
case SymbolBody::DefinedSyntheticKind:
return &cast<DefinedSynthetic<ELFT>>(Sym)->Section;
case SymbolBody::DefinedRegularKind: {
auto &D = cast<DefinedRegular<ELFT>>(Sym->repl());
if (D.Section)
return D.Section->OutSec;
break;
}
case SymbolBody::DefinedCommonKind:
return Out<ELFT>::Bss;
case SymbolBody::SharedKind:
if (cast<SharedSymbol<ELFT>>(Sym)->needsCopy())
return Out<ELFT>::Bss;
break;
case SymbolBody::UndefinedElfKind:
case SymbolBody::UndefinedKind:
case SymbolBody::LazyKind:
break;
case SymbolBody::DefinedBitcodeKind:
llvm_unreachable("should have been replaced");
}
return nullptr;
}
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 (isa<DefinedSynthetic<ELFT>>(Body))
return STB_LOCAL;
return Body->Binding;
}
template <class ELFT>
BuildIdSection<ELFT>::BuildIdSection()
: OutputSectionBase<ELFT>(".note.gnu.build-id", SHT_NOTE, SHF_ALLOC) {
// 16 bytes for the note section header and 8 bytes for FNV1 hash.
this->Header.sh_size = 24;
}
template <class ELFT> void BuildIdSection<ELFT>::writeTo(uint8_t *Buf) {
const endianness E = ELFT::TargetEndianness;
write32<E>(Buf, 4); // Name size
write32<E>(Buf + 4, sizeof(Hash)); // Content size
write32<E>(Buf + 8, NT_GNU_BUILD_ID); // Type
memcpy(Buf + 12, "GNU", 4); // Name string
HashBuf = Buf + 16;
}
template <class ELFT> void BuildIdSection<ELFT>::update(ArrayRef<uint8_t> Buf) {
// 64-bit FNV1 hash
const uint64_t Prime = 0x100000001b3;
for (uint8_t B : Buf) {
Hash *= Prime;
Hash ^= B;
}
}
template <class ELFT> void BuildIdSection<ELFT>::writeBuildId() {
const endianness E = ELFT::TargetEndianness;
write64<E>(HashBuf, Hash);
}
template <class ELFT>
MipsReginfoOutputSection<ELFT>::MipsReginfoOutputSection()
: OutputSectionBase<ELFT>(".reginfo", SHT_MIPS_REGINFO, SHF_ALLOC) {
this->Header.sh_addralign = 4;
this->Header.sh_entsize = sizeof(Elf_Mips_RegInfo);
this->Header.sh_size = sizeof(Elf_Mips_RegInfo);
}
template <class ELFT>
void MipsReginfoOutputSection<ELFT>::writeTo(uint8_t *Buf) {
auto *R = reinterpret_cast<Elf_Mips_RegInfo *>(Buf);
R->ri_gp_value = getMipsGpAddr<ELFT>();
R->ri_gprmask = GprMask;
}
template <class ELFT>
void MipsReginfoOutputSection<ELFT>::addSection(InputSectionBase<ELFT> *C) {
// Copy input object file's .reginfo gprmask to output.
auto *S = cast<MipsReginfoInputSection<ELFT>>(C);
GprMask |= S->Reginfo->ri_gprmask;
}
namespace lld {
namespace elf {
template class OutputSectionBase<ELF32LE>;
template class OutputSectionBase<ELF32BE>;
template class OutputSectionBase<ELF64LE>;
template class OutputSectionBase<ELF64BE>;
template class EhFrameHeader<ELF32LE>;
template class EhFrameHeader<ELF32BE>;
template class EhFrameHeader<ELF64LE>;
template class EhFrameHeader<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 MipsReginfoOutputSection<ELF32LE>;
template class MipsReginfoOutputSection<ELF32BE>;
template class MipsReginfoOutputSection<ELF64LE>;
template class MipsReginfoOutputSection<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 class BuildIdSection<ELF32LE>;
template class BuildIdSection<ELF32BE>;
template class BuildIdSection<ELF64LE>;
template class BuildIdSection<ELF64BE>;
}
}
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