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llvm-project/lld/ELF/OutputSections.cpp
Rui Ueyama 15ef5e174b ELF2: Make singleton output sections globally accessible. 
Previously, output sections that are handled specially by the linker
(e.g. PLT or GOT) were created by Writer and passed to other classes
that need them. The problem was that because these special sections
are required by so many classes, the plumbing work became too much
burden.

This patch is to simply make them accessible from anywhere in the
linker to eliminate the plumbing work once and for all.

http://reviews.llvm.org/D13486

llvm-svn: 249590
2015-10-07 19:18:16 +00:00

781 lines
28 KiB
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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"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf2;
template <> DynamicSection<ELF32BE> *Out<ELF32BE>::Dynamic = nullptr;
template <> DynamicSection<ELF32LE> *Out<ELF32LE>::Dynamic = nullptr;
template <> DynamicSection<ELF64BE> *Out<ELF64BE>::Dynamic = nullptr;
template <> DynamicSection<ELF64LE> *Out<ELF64LE>::Dynamic = nullptr;
template <> GotSection<ELF32BE> *Out<ELF32BE>::Got = nullptr;
template <> GotSection<ELF32LE> *Out<ELF32LE>::Got = nullptr;
template <> GotSection<ELF64BE> *Out<ELF64BE>::Got = nullptr;
template <> GotSection<ELF64LE> *Out<ELF64LE>::Got = nullptr;
template <> HashTableSection<ELF32BE> *Out<ELF32BE>::HashTab = nullptr;
template <> HashTableSection<ELF32LE> *Out<ELF32LE>::HashTab = nullptr;
template <> HashTableSection<ELF64BE> *Out<ELF64BE>::HashTab = nullptr;
template <> HashTableSection<ELF64LE> *Out<ELF64LE>::HashTab = nullptr;
template <> InterpSection<false> *Out<ELF32BE>::Interp = nullptr;
template <> InterpSection<false> *Out<ELF32LE>::Interp = nullptr;
template <> InterpSection<true> *Out<ELF64BE>::Interp = nullptr;
template <> InterpSection<true> *Out<ELF64LE>::Interp = nullptr;
template <> OutputSection<ELF32BE> *Out<ELF32BE>::Bss = nullptr;
template <> OutputSection<ELF32LE> *Out<ELF32LE>::Bss = nullptr;
template <> OutputSection<ELF64BE> *Out<ELF64BE>::Bss = nullptr;
template <> OutputSection<ELF64LE> *Out<ELF64LE>::Bss = nullptr;
template <> PltSection<ELF32BE> *Out<ELF32BE>::Plt = nullptr;
template <> PltSection<ELF32LE> *Out<ELF32LE>::Plt = nullptr;
template <> PltSection<ELF64BE> *Out<ELF64BE>::Plt = nullptr;
template <> PltSection<ELF64LE> *Out<ELF64LE>::Plt = nullptr;
template <> RelocationSection<ELF32BE> *Out<ELF32BE>::RelaDyn = nullptr;
template <> RelocationSection<ELF32LE> *Out<ELF32LE>::RelaDyn = nullptr;
template <> RelocationSection<ELF64BE> *Out<ELF64BE>::RelaDyn = nullptr;
template <> RelocationSection<ELF64LE> *Out<ELF64LE>::RelaDyn = nullptr;
template <> StringTableSection<false> *Out<ELF32BE>::DynStrTab = nullptr;
template <> StringTableSection<false> *Out<ELF32LE>::DynStrTab = nullptr;
template <> StringTableSection<true> *Out<ELF64BE>::DynStrTab = nullptr;
template <> StringTableSection<true> *Out<ELF64LE>::DynStrTab = nullptr;
template <> StringTableSection<false> *Out<ELF32BE>::StrTab = nullptr;
template <> StringTableSection<false> *Out<ELF32LE>::StrTab = nullptr;
template <> StringTableSection<true> *Out<ELF64BE>::StrTab = nullptr;
template <> StringTableSection<true> *Out<ELF64LE>::StrTab = nullptr;
template <> SymbolTableSection<ELF32BE> *Out<ELF32BE>::DynSymTab = nullptr;
template <> SymbolTableSection<ELF32LE> *Out<ELF32LE>::DynSymTab = nullptr;
template <> SymbolTableSection<ELF64BE> *Out<ELF64BE>::DynSymTab = nullptr;
template <> SymbolTableSection<ELF64LE> *Out<ELF64LE>::DynSymTab = nullptr;
template <> SymbolTableSection<ELF32BE> *Out<ELF32BE>::SymTab = nullptr;
template <> SymbolTableSection<ELF32LE> *Out<ELF32LE>::SymTab = nullptr;
template <> SymbolTableSection<ELF64BE> *Out<ELF64BE>::SymTab = nullptr;
template <> SymbolTableSection<ELF64LE> *Out<ELF64LE>::SymTab = nullptr;
template <bool Is64Bits>
OutputSectionBase<Is64Bits>::OutputSectionBase(StringRef Name, uint32_t sh_type,
uintX_t sh_flags)
: Name(Name) {
memset(&Header, 0, sizeof(HeaderT));
Header.sh_type = sh_type;
Header.sh_flags = sh_flags;
}
template <class ELFT>
GotSection<ELFT>::GotSection()
: OutputSectionBase<ELFT::Is64Bits>(".got", llvm::ELF::SHT_PROGBITS,
llvm::ELF::SHF_ALLOC |
llvm::ELF::SHF_WRITE) {
this->Header.sh_addralign = this->getAddrSize();
}
template <class ELFT> void GotSection<ELFT>::addEntry(SymbolBody *Sym) {
Sym->setGotIndex(Entries.size());
Entries.push_back(Sym);
}
template <class ELFT>
typename GotSection<ELFT>::uintX_t
GotSection<ELFT>::getEntryAddr(const SymbolBody &B) const {
return this->getVA() + B.getGotIndex() * this->getAddrSize();
}
template <class ELFT> void GotSection<ELFT>::writeTo(uint8_t *Buf) {
for (const SymbolBody *B : Entries) {
uint8_t *Entry = Buf;
Buf += sizeof(uintX_t);
if (canBePreempted(B))
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::Is64Bits>(".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) {
uintptr_t Start = reinterpret_cast<uintptr_t>(Buf);
for (const SymbolBody *E : Entries) {
uint64_t GotEntryAddr = Out<ELFT>::Got->getEntryAddr(*E);
uintptr_t InstPos = reinterpret_cast<uintptr_t>(Buf);
uint64_t PltEntryAddr = (InstPos - Start) + this->getVA();
Target->writePltEntry(Buf, GotEntryAddr, PltEntryAddr);
Buf += 8;
}
}
template <class ELFT> void PltSection<ELFT>::addEntry(SymbolBody *Sym) {
Sym->setPltIndex(Entries.size());
Entries.push_back(Sym);
}
template <class ELFT>
typename PltSection<ELFT>::uintX_t
PltSection<ELFT>::getEntryAddr(const SymbolBody &B) const {
return this->getVA() + B.getPltIndex() * EntrySize;
}
template <class ELFT>
RelocationSection<ELFT>::RelocationSection(bool IsRela)
: OutputSectionBase<ELFT::Is64Bits>(IsRela ? ".rela.dyn" : ".rel.dyn",
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;
}
template <class ELFT> void RelocationSection<ELFT>::writeTo(uint8_t *Buf) {
const unsigned EntrySize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
bool IsMips64EL = Relocs[0].C.getFile()->getObj().isMips64EL();
for (const DynamicReloc<ELFT> &Rel : Relocs) {
auto *P = reinterpret_cast<Elf_Rel *>(Buf);
Buf += EntrySize;
const InputSection<ELFT> &C = Rel.C;
const Elf_Rel &RI = Rel.RI;
OutputSection<ELFT> *OutSec = C.getOutputSection();
uint32_t SymIndex = RI.getSymbol(IsMips64EL);
const ObjectFile<ELFT> &File = *C.getFile();
const SymbolBody *Body = File.getSymbolBody(SymIndex);
const ELFFile<ELFT> &Obj = File.getObj();
uint32_t Type = RI.getType(IsMips64EL);
bool CanBePreempted = canBePreempted(Body);
uintX_t Addend = 0;
if (!CanBePreempted) {
if (IsRela) {
if (Body)
Addend += getSymVA<ELFT>(cast<ELFSymbolBody<ELFT>>(*Body));
else
Addend += getLocalSymVA(
Obj.getRelocationSymbol(&RI, File.getSymbolTable()), File);
}
P->setSymbolAndType(0, Target->getRelativeReloc(), IsMips64EL);
}
if (Body && Target->relocNeedsGot(Type, *Body)) {
P->r_offset = Out<ELFT>::Got->getEntryAddr(*Body);
if (CanBePreempted)
P->setSymbolAndType(Body->getDynamicSymbolTableIndex(),
Target->getGotReloc(), IsMips64EL);
} else {
if (IsRela)
Addend += static_cast<const Elf_Rela &>(RI).r_addend;
P->r_offset = RI.r_offset + C.getOutputSectionOff() + OutSec->getVA();
if (CanBePreempted)
P->setSymbolAndType(Body->getDynamicSymbolTableIndex(), Type,
IsMips64EL);
}
if (IsRela)
static_cast<Elf_Rela *>(P)->r_addend = Addend;
}
}
template <class ELFT> void RelocationSection<ELFT>::finalize() {
this->Header.sh_link = Out<ELFT>::DynSymTab->getSectionIndex();
this->Header.sh_size = Relocs.size() * this->Header.sh_entsize;
}
template <bool Is64Bits>
InterpSection<Is64Bits>::InterpSection()
: OutputSectionBase<Is64Bits>(".interp", llvm::ELF::SHT_PROGBITS,
llvm::ELF::SHF_ALLOC) {
this->Header.sh_size = Config->DynamicLinker.size() + 1;
this->Header.sh_addralign = 1;
}
template <bool Is64Bits>
template <endianness E>
void OutputSectionBase<Is64Bits>::writeHeaderTo(
typename ELFFile<ELFType<E, Is64Bits>>::Elf_Shdr *SHdr) {
SHdr->sh_name = Header.sh_name;
SHdr->sh_type = Header.sh_type;
SHdr->sh_flags = Header.sh_flags;
SHdr->sh_addr = Header.sh_addr;
SHdr->sh_offset = Header.sh_offset;
SHdr->sh_size = Header.sh_size;
SHdr->sh_link = Header.sh_link;
SHdr->sh_info = Header.sh_info;
SHdr->sh_addralign = Header.sh_addralign;
SHdr->sh_entsize = Header.sh_entsize;
}
template <bool Is64Bits> void InterpSection<Is64Bits>::writeTo(uint8_t *Buf) {
memcpy(Buf, Config->DynamicLinker.data(), Config->DynamicLinker.size());
}
template <class ELFT>
HashTableSection<ELFT>::HashTableSection()
: OutputSectionBase<ELFT::Is64Bits>(".hash", llvm::ELF::SHT_HASH,
llvm::ELF::SHF_ALLOC) {
this->Header.sh_entsize = sizeof(Elf_Word);
this->Header.sh_addralign = sizeof(Elf_Word);
}
template <class ELFT> void HashTableSection<ELFT>::addSymbol(SymbolBody *S) {
StringRef Name = S->getName();
Out<ELFT>::DynSymTab->addSymbol(Name);
Hashes.push_back(hash(Name));
S->setDynamicSymbolTableIndex(Hashes.size());
}
template <class ELFT> void HashTableSection<ELFT>::finalize() {
this->Header.sh_link = Out<ELFT>::DynSymTab->getSectionIndex();
assert(Out<ELFT>::DynSymTab->getNumSymbols() == Hashes.size() + 1);
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 (unsigned I = 1; I < NumSymbols; ++I) {
uint32_t Hash = Hashes[I - 1] % NumSymbols;
Chains[I] = Buckets[Hash];
Buckets[Hash] = I;
}
}
template <class ELFT>
DynamicSection<ELFT>::DynamicSection(SymbolTable &SymTab)
: OutputSectionBase<ELFT::Is64Bits>(".dynamic", llvm::ELF::SHT_DYNAMIC,
llvm::ELF::SHF_ALLOC |
llvm::ELF::SHF_WRITE),
SymTab(SymTab) {
typename Base::HeaderT &Header = this->Header;
Header.sh_addralign = ELFT::Is64Bits ? 8 : 4;
Header.sh_entsize = ELFT::Is64Bits ? 16 : 8;
}
template <class ELFT> void DynamicSection<ELFT>::finalize() {
if (this->Header.sh_size)
return; // Already finalized.
typename Base::HeaderT &Header = this->Header;
Header.sh_link = Out<ELFT>::DynStrTab->getSectionIndex();
unsigned NumEntries = 0;
if (Out<ELFT>::RelaDyn->hasRelocs()) {
++NumEntries; // DT_RELA / DT_REL
++NumEntries; // DT_RELASZ / DT_RELSZ
++NumEntries; // DT_RELAENT / DT_RELENT
}
++NumEntries; // DT_SYMTAB
++NumEntries; // DT_SYMENT
++NumEntries; // DT_STRTAB
++NumEntries; // DT_STRSZ
++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;
const std::vector<std::unique_ptr<SharedFileBase>> &SharedFiles =
SymTab.getSharedFiles();
for (const std::unique_ptr<SharedFileBase> &File : SharedFiles)
Out<ELFT>::DynStrTab->add(File->getSoName());
NumEntries += SharedFiles.size();
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->ZNow)
++NumEntries; // DT_FLAGS_1
++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));
}
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());
WritePtr(DT_HASH, Out<ELFT>::HashTab->getVA());
if (!Config->RPath.empty())
// 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.
WriteVal(Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH,
Out<ELFT>::DynStrTab->getFileOff(Config->RPath));
if (!Config->SoName.empty())
WriteVal(DT_SONAME, Out<ELFT>::DynStrTab->getFileOff(Config->SoName));
auto WriteArray = [&](int32_t T1, int32_t T2,
const OutputSection<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);
const std::vector<std::unique_ptr<SharedFileBase>> &SharedFiles =
SymTab.getSharedFiles();
for (const std::unique_ptr<SharedFileBase> &File : SharedFiles)
WriteVal(DT_NEEDED, Out<ELFT>::DynStrTab->getFileOff(File->getSoName()));
if (InitSym)
WritePtr(DT_INIT, getSymVA<ELFT>(*InitSym));
if (FiniSym)
WritePtr(DT_FINI, getSymVA<ELFT>(*FiniSym));
if (Config->ZNow)
WriteVal(DT_FLAGS_1, DF_1_NOW);
WriteVal(DT_NULL, 0);
}
template <class ELFT>
OutputSection<ELFT>::OutputSection(StringRef Name, uint32_t sh_type,
uintX_t sh_flags)
: OutputSectionBase<ELFT::Is64Bits>(Name, sh_type, sh_flags) {}
template <class ELFT>
void OutputSection<ELFT>::addSection(InputSection<ELFT> *C) {
Sections.push_back(C);
C->setOutputSection(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->setOutputSectionOff(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);
const InputSection<ELFT> *SC = &DR.Section;
OutputSection<ELFT> *OS = SC->getOutputSection();
return OS->getVA() + SC->getOutputSectionOff() + DR.Sym.st_value;
}
case SymbolBody::DefinedCommonKind:
return Out<ELFT>::Bss->getVA() + cast<DefinedCommon<ELFT>>(S).OffsetInBSS;
case SymbolBody::SharedKind:
case SymbolBody::UndefinedKind:
return 0;
case SymbolBody::LazyKind:
assert(S.isUsedInRegularObj() && "Lazy symbol reached writer");
return 0;
}
llvm_unreachable("Invalid symbol kind");
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t
lld::elf2::getLocalSymVA(const typename ELFFile<ELFT>::Elf_Sym *Sym,
const ObjectFile<ELFT> &File) {
uint32_t SecIndex = Sym->st_shndx;
if (SecIndex == SHN_XINDEX)
SecIndex = File.getObj().getExtendedSymbolTableIndex(
Sym, File.getSymbolTable(), File.getSymbolTableShndx());
ArrayRef<InputSection<ELFT> *> Sections = File.getSections();
InputSection<ELFT> *Section = Sections[SecIndex];
OutputSection<ELFT> *OutSec = Section->getOutputSection();
return OutSec->getVA() + Section->getOutputSectionOff() + Sym->st_value;
}
bool lld::elf2::canBePreempted(const SymbolBody *Body) {
if (!Body)
return false;
if (Body->isShared())
return true;
if (Body->isUndefined() && !Body->isWeak())
return true;
if (!Config->Shared)
return false;
return Body->getMostConstrainingVisibility() == STV_DEFAULT;
}
template <class ELFT> void OutputSection<ELFT>::writeTo(uint8_t *Buf) {
for (InputSection<ELFT> *C : Sections)
C->writeTo(Buf);
}
template <bool Is64Bits>
StringTableSection<Is64Bits>::StringTableSection(bool Dynamic)
: OutputSectionBase<Is64Bits>(Dynamic ? ".dynstr" : ".strtab",
llvm::ELF::SHT_STRTAB,
Dynamic ? (uintX_t)llvm::ELF::SHF_ALLOC : 0),
Dynamic(Dynamic) {
this->Header.sh_addralign = 1;
}
template <bool Is64Bits>
void StringTableSection<Is64Bits>::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.getMostConstrainingVisibility();
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(StringRef SymName,
const typename ELFFile<ELFT>::Elf_Sym &Sym) {
if (Sym.getType() == STT_SECTION)
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 &Table, StringTableSection<ELFT::Is64Bits> &StrTabSec)
: OutputSectionBase<ELFT::Is64Bits>(
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::Is64Bits> Base;
typename Base::HeaderT &Header = this->Header;
Header.sh_entsize = sizeof(Elf_Sym);
Header.sh_addralign = ELFT::Is64Bits ? 8 : 4;
}
template <class ELFT> void SymbolTableSection<ELFT>::finalize() {
this->Header.sh_size = getNumSymbols() * sizeof(Elf_Sym);
this->Header.sh_link = StrTabSec.getSectionIndex();
this->Header.sh_info = NumLocals + 1;
}
template <class ELFT>
void SymbolTableSection<ELFT>::addSymbol(StringRef Name, bool isLocal) {
StrTabSec.add(Name);
++NumVisible;
if (isLocal)
++NumLocals;
}
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<ObjectFileBase> &FileB : Table.getObjectFiles()) {
auto &File = cast<ObjectFile<ELFT>>(*FileB);
Elf_Sym_Range Syms = File.getLocalSymbols();
for (const Elf_Sym &Sym : Syms) {
ErrorOr<StringRef> SymName = Sym.getName(File.getStringTable());
if (SymName && !shouldKeepInSymtab<ELFT>(*SymName, Sym))
continue;
auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
Buf += sizeof(*ESym);
ESym->st_name = (SymName) ? StrTabSec.getFileOff(*SymName) : 0;
ESym->st_size = Sym.st_size;
ESym->setBindingAndType(Sym.getBinding(), Sym.getType());
uint32_t SecIndex = Sym.st_shndx;
uintX_t VA = Sym.st_value;
if (SecIndex == SHN_ABS) {
ESym->st_shndx = SHN_ABS;
} else {
if (SecIndex == SHN_XINDEX)
SecIndex = File.getObj().getExtendedSymbolTableIndex(
&Sym, File.getSymbolTable(), File.getSymbolTableShndx());
ArrayRef<InputSection<ELFT> *> Sections = File.getSections();
const InputSection<ELFT> *Section = Sections[SecIndex];
const OutputSection<ELFT> *OutSec = Section->getOutputSection();
ESym->st_shndx = OutSec->getSectionIndex();
VA += OutSec->getVA() + Section->getOutputSectionOff();
}
ESym->st_value = VA;
}
}
}
template <class ELFT>
void SymbolTableSection<ELFT>::writeGlobalSymbols(uint8_t *&Buf) {
// Write the internal symbol table contents to the output symbol table
// pointed by Buf.
uint8_t *Start = Buf;
for (const std::pair<StringRef, Symbol *> &P : Table.getSymbols()) {
StringRef Name = P.first;
Symbol *Sym = P.second;
SymbolBody *Body = Sym->Body;
if (!includeInSymtab<ELFT>(*Body))
continue;
if (StrTabSec.isDynamic() && !includeInDynamicSymtab(*Body))
continue;
auto *ESym = reinterpret_cast<Elf_Sym *>(Buf);
Buf += sizeof(*ESym);
ESym->st_name = StrTabSec.getFileOff(Name);
const OutputSection<ELFT> *OutSec = nullptr;
const InputSection<ELFT> *Section = nullptr;
switch (Body->kind()) {
case SymbolBody::DefinedSyntheticKind:
OutSec = &cast<DefinedSynthetic<ELFT>>(Body)->Section;
break;
case SymbolBody::DefinedRegularKind:
Section = &cast<DefinedRegular<ELFT>>(Body)->Section;
break;
case SymbolBody::DefinedCommonKind:
OutSec = Out<ELFT>::Bss;
break;
case SymbolBody::UndefinedKind:
case SymbolBody::DefinedAbsoluteKind:
case SymbolBody::SharedKind:
case SymbolBody::LazyKind:
break;
}
unsigned char Binding = Body->isWeak() ? STB_WEAK : STB_GLOBAL;
unsigned char Type = STT_NOTYPE;
uintX_t Size = 0;
if (const auto *EBody = dyn_cast<ELFSymbolBody<ELFT>>(Body)) {
const Elf_Sym &InputSym = EBody->Sym;
Binding = InputSym.getBinding();
Type = InputSym.getType();
Size = InputSym.st_size;
}
unsigned char Visibility = Body->getMostConstrainingVisibility();
if (Visibility != STV_DEFAULT && Visibility != STV_PROTECTED)
Binding = STB_LOCAL;
ESym->setBindingAndType(Binding, Type);
ESym->st_size = Size;
ESym->setVisibility(Visibility);
ESym->st_value = getSymVA<ELFT>(*Body);
if (Section)
OutSec = Section->getOutputSection();
if (isa<DefinedAbsolute<ELFT>>(Body))
ESym->st_shndx = SHN_ABS;
else if (OutSec)
ESym->st_shndx = OutSec->getSectionIndex();
}
if (!StrTabSec.isDynamic())
std::stable_sort(
reinterpret_cast<Elf_Sym *>(Start), reinterpret_cast<Elf_Sym *>(Buf),
[](const Elf_Sym &A, const Elf_Sym &B) -> bool {
return A.getBinding() == STB_LOCAL && B.getBinding() != STB_LOCAL;
});
}
namespace lld {
namespace elf2 {
template class OutputSectionBase<false>;
template class OutputSectionBase<true>;
template void OutputSectionBase<false>::writeHeaderTo<support::little>(
ELFFile<ELFType<support::little, false>>::Elf_Shdr *SHdr);
template void OutputSectionBase<true>::writeHeaderTo<support::little>(
ELFFile<ELFType<support::little, true>>::Elf_Shdr *SHdr);
template void OutputSectionBase<false>::writeHeaderTo<support::big>(
ELFFile<ELFType<support::big, false>>::Elf_Shdr *SHdr);
template void OutputSectionBase<true>::writeHeaderTo<support::big>(
ELFFile<ELFType<support::big, true>>::Elf_Shdr *SHdr);
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<false>;
template class InterpSection<true>;
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 StringTableSection<false>;
template class StringTableSection<true>;
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
getLocalSymVA(const ELFFile<ELF32LE>::Elf_Sym *, const ObjectFile<ELF32LE> &);
template ELFFile<ELF32BE>::uintX_t
getLocalSymVA(const ELFFile<ELF32BE>::Elf_Sym *, const ObjectFile<ELF32BE> &);
template ELFFile<ELF64LE>::uintX_t
getLocalSymVA(const ELFFile<ELF64LE>::Elf_Sym *, const ObjectFile<ELF64LE> &);
template ELFFile<ELF64BE>::uintX_t
getLocalSymVA(const ELFFile<ELF64BE>::Elf_Sym *, const ObjectFile<ELF64BE> &);
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>(StringRef,
const ELFFile<ELF32LE>::Elf_Sym &);
template bool shouldKeepInSymtab<ELF32BE>(StringRef,
const ELFFile<ELF32BE>::Elf_Sym &);
template bool shouldKeepInSymtab<ELF64LE>(StringRef,
const ELFFile<ELF64LE>::Elf_Sym &);
template bool shouldKeepInSymtab<ELF64BE>(StringRef,
const ELFFile<ELF64BE>::Elf_Sym &);
}
}
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