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aa2db889847114c6348c113e6215560ff2346cc2
llvm/lld/ELF/Writer.cpp
Rui Ueyama aa2db88984 ELF: Make error() to always set HasError. 
Previously, it checked for the EC parameter and set HasError
only when there was an error. But in most places we called
error only when error had occurred, so this behavior was confusing.

llvm-svn: 275517
2016-07-15 01:38:54 +00:00

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44 KiB
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//===- Writer.cpp ---------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Writer.h"
#include "Config.h"
#include "LinkerScript.h"
#include "OutputSections.h"
#include "Relocations.h"
#include "Strings.h"
#include "SymbolTable.h"
#include "Target.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace lld;
using namespace lld::elf;
namespace {
// The writer writes a SymbolTable result to a file.
template <class ELFT> class Writer {
public:
typedef typename ELFT::uint uintX_t;
typedef typename ELFT::Shdr Elf_Shdr;
typedef typename ELFT::Ehdr Elf_Ehdr;
typedef typename ELFT::Phdr Elf_Phdr;
typedef typename ELFT::Sym Elf_Sym;
typedef typename ELFT::SymRange Elf_Sym_Range;
typedef typename ELFT::Rela Elf_Rela;
Writer(SymbolTable<ELFT> &S) : Symtab(S) {}
void run();
private:
// This describes a program header entry.
// Each contains type, access flags and range of output sections that will be
// placed in it.
struct Phdr {
Phdr(unsigned Type, unsigned Flags) {
H.p_type = Type;
H.p_flags = Flags;
}
Elf_Phdr H = {};
OutputSectionBase<ELFT> *First = nullptr;
OutputSectionBase<ELFT> *Last = nullptr;
};
void copyLocalSymbols();
void addReservedSymbols();
void createSections();
void addPredefinedSections();
bool needsGot();
void createPhdrs();
void assignAddresses();
void assignFileOffsets();
void setPhdrs();
void fixHeaders();
void fixSectionAlignments();
void fixAbsoluteSymbols();
void openFile();
void writeHeader();
void writeSections();
void writeBuildId();
bool needsInterpSection() const {
return !Symtab.getSharedFiles().empty() && !Config->DynamicLinker.empty();
}
bool isOutputDynamic() const {
return !Symtab.getSharedFiles().empty() || Config->Pic;
}
void addCommonSymbols(std::vector<DefinedCommon *> &Syms);
std::unique_ptr<llvm::FileOutputBuffer> Buffer;
BumpPtrAllocator Alloc;
std::vector<OutputSectionBase<ELFT> *> OutputSections;
std::vector<std::unique_ptr<OutputSectionBase<ELFT>>> OwningSections;
void addRelIpltSymbols();
void addStartEndSymbols();
void addStartStopSymbols(OutputSectionBase<ELFT> *Sec);
SymbolTable<ELFT> &Symtab;
std::vector<Phdr> Phdrs;
uintX_t FileSize;
uintX_t SectionHeaderOff;
};
} // anonymous namespace
template <class ELFT>
StringRef elf::getOutputSectionName(InputSectionBase<ELFT> *S) {
StringRef Dest = Script<ELFT>::X->getOutputSection(S);
if (!Dest.empty())
return Dest;
StringRef Name = S->getSectionName();
for (StringRef V : {".text.", ".rodata.", ".data.rel.ro.", ".data.", ".bss.",
".init_array.", ".fini_array.", ".ctors.", ".dtors.",
".tbss.", ".gcc_except_table.", ".tdata."})
if (Name.startswith(V))
return V.drop_back();
return Name;
}
template <class ELFT>
void elf::reportDiscarded(InputSectionBase<ELFT> *IS,
const std::unique_ptr<elf::ObjectFile<ELFT>> &File) {
if (!Config->PrintGcSections || !IS || IS->Live)
return;
errs() << "removing unused section from '" << IS->getSectionName()
<< "' in file '" << File->getName() << "'\n";
}
template <class ELFT> void elf::writeResult(SymbolTable<ELFT> *Symtab) {
typedef typename ELFT::uint uintX_t;
typedef typename ELFT::Ehdr Elf_Ehdr;
// Create singleton output sections.
OutputSection<ELFT> Bss(".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
DynamicSection<ELFT> Dynamic;
EhOutputSection<ELFT> EhFrame;
GotSection<ELFT> Got;
InterpSection<ELFT> Interp;
PltSection<ELFT> Plt;
RelocationSection<ELFT> RelaDyn(Config->Rela ? ".rela.dyn" : ".rel.dyn",
Config->ZCombreloc);
StringTableSection<ELFT> DynStrTab(".dynstr", true);
StringTableSection<ELFT> ShStrTab(".shstrtab", false);
SymbolTableSection<ELFT> DynSymTab(DynStrTab);
VersionTableSection<ELFT> VerSym;
VersionNeedSection<ELFT> VerNeed;
OutputSectionBase<ELFT> ElfHeader("", 0, SHF_ALLOC);
ElfHeader.setSize(sizeof(Elf_Ehdr));
OutputSectionBase<ELFT> ProgramHeaders("", 0, SHF_ALLOC);
ProgramHeaders.updateAlignment(sizeof(uintX_t));
// Instantiate optional output sections if they are needed.
std::unique_ptr<BuildIdSection<ELFT>> BuildId;
std::unique_ptr<EhFrameHeader<ELFT>> EhFrameHdr;
std::unique_ptr<GnuHashTableSection<ELFT>> GnuHashTab;
std::unique_ptr<GotPltSection<ELFT>> GotPlt;
std::unique_ptr<HashTableSection<ELFT>> HashTab;
std::unique_ptr<RelocationSection<ELFT>> RelaPlt;
std::unique_ptr<StringTableSection<ELFT>> StrTab;
std::unique_ptr<SymbolTableSection<ELFT>> SymTabSec;
std::unique_ptr<OutputSection<ELFT>> MipsRldMap;
std::unique_ptr<VersionDefinitionSection<ELFT>> VerDef;
if (Config->BuildId == BuildIdKind::Fnv1)
BuildId.reset(new BuildIdFnv1<ELFT>);
else if (Config->BuildId == BuildIdKind::Md5)
BuildId.reset(new BuildIdMd5<ELFT>);
else if (Config->BuildId == BuildIdKind::Sha1)
BuildId.reset(new BuildIdSha1<ELFT>);
else if (Config->BuildId == BuildIdKind::Hexstring)
BuildId.reset(new BuildIdHexstring<ELFT>);
if (Config->EhFrameHdr)
EhFrameHdr.reset(new EhFrameHeader<ELFT>);
if (Config->GnuHash)
GnuHashTab.reset(new GnuHashTableSection<ELFT>);
if (Config->SysvHash)
HashTab.reset(new HashTableSection<ELFT>);
StringRef S = Config->Rela ? ".rela.plt" : ".rel.plt";
GotPlt.reset(new GotPltSection<ELFT>);
RelaPlt.reset(new RelocationSection<ELFT>(S, false /*Sort*/));
if (!Config->StripAll) {
StrTab.reset(new StringTableSection<ELFT>(".strtab", false));
SymTabSec.reset(new SymbolTableSection<ELFT>(*StrTab));
}
if (Config->EMachine == EM_MIPS && !Config->Shared) {
// This is a MIPS specific section to hold a space within the data segment
// of executable file which is pointed to by the DT_MIPS_RLD_MAP entry.
// See "Dynamic section" in Chapter 5 in the following document:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
MipsRldMap.reset(new OutputSection<ELFT>(".rld_map", SHT_PROGBITS,
SHF_ALLOC | SHF_WRITE));
MipsRldMap->setSize(sizeof(uintX_t));
MipsRldMap->updateAlignment(sizeof(uintX_t));
}
if (!Config->SymbolVersions.empty())
VerDef.reset(new VersionDefinitionSection<ELFT>());
Out<ELFT>::Bss = &Bss;
Out<ELFT>::BuildId = BuildId.get();
Out<ELFT>::DynStrTab = &DynStrTab;
Out<ELFT>::DynSymTab = &DynSymTab;
Out<ELFT>::Dynamic = &Dynamic;
Out<ELFT>::EhFrame = &EhFrame;
Out<ELFT>::EhFrameHdr = EhFrameHdr.get();
Out<ELFT>::GnuHashTab = GnuHashTab.get();
Out<ELFT>::Got = &Got;
Out<ELFT>::GotPlt = GotPlt.get();
Out<ELFT>::HashTab = HashTab.get();
Out<ELFT>::Interp = &Interp;
Out<ELFT>::Plt = &Plt;
Out<ELFT>::RelaDyn = &RelaDyn;
Out<ELFT>::RelaPlt = RelaPlt.get();
Out<ELFT>::ShStrTab = &ShStrTab;
Out<ELFT>::StrTab = StrTab.get();
Out<ELFT>::SymTab = SymTabSec.get();
Out<ELFT>::VerDef = VerDef.get();
Out<ELFT>::VerSym = &VerSym;
Out<ELFT>::VerNeed = &VerNeed;
Out<ELFT>::MipsRldMap = MipsRldMap.get();
Out<ELFT>::Opd = nullptr;
Out<ELFT>::OpdBuf = nullptr;
Out<ELFT>::TlsPhdr = nullptr;
Out<ELFT>::ElfHeader = &ElfHeader;
Out<ELFT>::ProgramHeaders = &ProgramHeaders;
Writer<ELFT>(*Symtab).run();
}
// The main function of the writer.
template <class ELFT> void Writer<ELFT>::run() {
if (!Config->DiscardAll)
copyLocalSymbols();
addReservedSymbols();
createSections();
if (HasError)
return;
if (Config->Relocatable) {
assignFileOffsets();
} else {
createPhdrs();
fixHeaders();
if (ScriptConfig->DoLayout) {
Script<ELFT>::X->assignAddresses(OutputSections);
} else {
fixSectionAlignments();
assignAddresses();
}
assignFileOffsets();
setPhdrs();
fixAbsoluteSymbols();
}
openFile();
if (HasError)
return;
writeHeader();
writeSections();
writeBuildId();
if (HasError)
return;
check(Buffer->commit());
}
template <class ELFT>
static void reportUndefined(SymbolTable<ELFT> &Symtab, SymbolBody *Sym) {
if (Config->UnresolvedSymbols == UnresolvedPolicy::Ignore)
return;
if (Config->Shared && Sym->symbol()->Visibility == STV_DEFAULT &&
Config->UnresolvedSymbols != UnresolvedPolicy::NoUndef)
return;
std::string Msg = "undefined symbol: " + Sym->getName().str();
if (InputFile *File = Sym->getSourceFile<ELFT>())
Msg += " in " + getFilename(File);
if (Config->UnresolvedSymbols == UnresolvedPolicy::Warn)
warning(Msg);
else
error(Msg);
}
template <class ELFT>
static bool shouldKeepInSymtab(InputSectionBase<ELFT> *Sec, StringRef SymName,
const SymbolBody &B) {
if (B.isFile())
return false;
// We keep sections in symtab for relocatable output.
if (B.isSection())
return Config->Relocatable;
// If sym references a section in a discarded group, don't keep it.
if (Sec == &InputSection<ELFT>::Discarded)
return false;
if (Config->DiscardNone)
return true;
// In ELF assembly .L symbols are normally discarded by the assembler.
// If the assembler fails to do so, the linker discards them if
// * --discard-locals is used.
// * The symbol is in a SHF_MERGE section, which is normally the reason for
// the assembler keeping the .L symbol.
if (!SymName.startswith(".L") && !SymName.empty())
return true;
if (Config->DiscardLocals)
return false;
return !(Sec->getSectionHdr()->sh_flags & SHF_MERGE);
}
template <class ELFT> static bool includeInSymtab(const SymbolBody &B) {
if (!B.isLocal() && !B.symbol()->IsUsedInRegularObj)
return false;
if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B)) {
// Always include absolute symbols.
if (!D->Section)
return true;
// Exclude symbols pointing to garbage-collected sections.
if (!D->Section->Live)
return false;
if (auto *S = dyn_cast<MergeInputSection<ELFT>>(D->Section))
if (!S->getSectionPiece(D->Value)->Live)
return false;
}
return true;
}
// Local symbols are not in the linker's symbol table. This function scans
// each object file's symbol table to copy local symbols to the output.
template <class ELFT> void Writer<ELFT>::copyLocalSymbols() {
if (!Out<ELFT>::SymTab)
return;
for (const std::unique_ptr<elf::ObjectFile<ELFT>> &F :
Symtab.getObjectFiles()) {
const char *StrTab = F->getStringTable().data();
for (SymbolBody *B : F->getLocalSymbols()) {
auto *DR = dyn_cast<DefinedRegular<ELFT>>(B);
// No reason to keep local undefined symbol in symtab.
if (!DR)
continue;
if (!includeInSymtab<ELFT>(*B))
continue;
StringRef SymName(StrTab + B->getNameOffset());
InputSectionBase<ELFT> *Sec = DR->Section;
if (!shouldKeepInSymtab<ELFT>(Sec, SymName, *B))
continue;
++Out<ELFT>::SymTab->NumLocals;
if (Config->Relocatable)
B->DynsymIndex = Out<ELFT>::SymTab->NumLocals;
F->KeptLocalSyms.push_back(
std::make_pair(DR, Out<ELFT>::SymTab->StrTabSec.addString(SymName)));
}
}
}
// PPC64 has a number of special SHT_PROGBITS+SHF_ALLOC+SHF_WRITE sections that
// we would like to make sure appear is a specific order to maximize their
// coverage by a single signed 16-bit offset from the TOC base pointer.
// Conversely, the special .tocbss section should be first among all SHT_NOBITS
// sections. This will put it next to the loaded special PPC64 sections (and,
// thus, within reach of the TOC base pointer).
static int getPPC64SectionRank(StringRef SectionName) {
return StringSwitch<int>(SectionName)
.Case(".tocbss", 0)
.Case(".branch_lt", 2)
.Case(".toc", 3)
.Case(".toc1", 4)
.Case(".opd", 5)
.Default(1);
}
template <class ELFT> static bool isRelroSection(OutputSectionBase<ELFT> *Sec) {
if (!Config->ZRelro)
return false;
typename ELFT::uint Flags = Sec->getFlags();
if (!(Flags & SHF_ALLOC) || !(Flags & SHF_WRITE))
return false;
if (Flags & SHF_TLS)
return true;
uint32_t Type = Sec->getType();
if (Type == SHT_INIT_ARRAY || Type == SHT_FINI_ARRAY ||
Type == SHT_PREINIT_ARRAY)
return true;
if (Sec == Out<ELFT>::GotPlt)
return Config->ZNow;
if (Sec == Out<ELFT>::Dynamic || Sec == Out<ELFT>::Got)
return true;
StringRef S = Sec->getName();
return S == ".data.rel.ro" || S == ".ctors" || S == ".dtors" || S == ".jcr" ||
S == ".eh_frame";
}
// Output section ordering is determined by this function.
template <class ELFT>
static bool compareSections(OutputSectionBase<ELFT> *A,
OutputSectionBase<ELFT> *B) {
typedef typename ELFT::uint uintX_t;
int Comp = Script<ELFT>::X->compareSections(A->getName(), B->getName());
if (Comp != 0)
return Comp < 0;
uintX_t AFlags = A->getFlags();
uintX_t BFlags = B->getFlags();
// Allocatable sections go first to reduce the total PT_LOAD size and
// so debug info doesn't change addresses in actual code.
bool AIsAlloc = AFlags & SHF_ALLOC;
bool BIsAlloc = BFlags & SHF_ALLOC;
if (AIsAlloc != BIsAlloc)
return AIsAlloc;
// We don't have any special requirements for the relative order of
// two non allocatable sections.
if (!AIsAlloc)
return false;
// We want the read only sections first so that they go in the PT_LOAD
// covering the program headers at the start of the file.
bool AIsWritable = AFlags & SHF_WRITE;
bool BIsWritable = BFlags & SHF_WRITE;
if (AIsWritable != BIsWritable)
return BIsWritable;
// For a corresponding reason, put non exec sections first (the program
// header PT_LOAD is not executable).
bool AIsExec = AFlags & SHF_EXECINSTR;
bool BIsExec = BFlags & SHF_EXECINSTR;
if (AIsExec != BIsExec)
return BIsExec;
// If we got here we know that both A and B are in the same PT_LOAD.
// The TLS initialization block needs to be a single contiguous block in a R/W
// PT_LOAD, so stick TLS sections directly before R/W sections. The TLS NOBITS
// sections are placed here as they don't take up virtual address space in the
// PT_LOAD.
bool AIsTls = AFlags & SHF_TLS;
bool BIsTls = BFlags & SHF_TLS;
if (AIsTls != BIsTls)
return AIsTls;
// The next requirement we have is to put nobits sections last. The
// reason is that the only thing the dynamic linker will see about
// them is a p_memsz that is larger than p_filesz. Seeing that it
// zeros the end of the PT_LOAD, so that has to correspond to the
// nobits sections.
bool AIsNoBits = A->getType() == SHT_NOBITS;
bool BIsNoBits = B->getType() == SHT_NOBITS;
if (AIsNoBits != BIsNoBits)
return BIsNoBits;
// We place RelRo section before plain r/w ones.
bool AIsRelRo = isRelroSection(A);
bool BIsRelRo = isRelroSection(B);
if (AIsRelRo != BIsRelRo)
return AIsRelRo;
// Some architectures have additional ordering restrictions for sections
// within the same PT_LOAD.
if (Config->EMachine == EM_PPC64)
return getPPC64SectionRank(A->getName()) <
getPPC64SectionRank(B->getName());
return false;
}
// Until this function is called, common symbols do not belong to any section.
// This function adds them to end of BSS section.
template <class ELFT>
void Writer<ELFT>::addCommonSymbols(std::vector<DefinedCommon *> &Syms) {
if (Syms.empty())
return;
// Sort the common symbols by alignment as an heuristic to pack them better.
std::stable_sort(Syms.begin(), Syms.end(),
[](const DefinedCommon *A, const DefinedCommon *B) {
return A->Alignment > B->Alignment;
});
uintX_t Off = Out<ELFT>::Bss->getSize();
for (DefinedCommon *C : Syms) {
Off = alignTo(Off, C->Alignment);
Out<ELFT>::Bss->updateAlignment(C->Alignment);
C->OffsetInBss = Off;
Off += C->Size;
}
Out<ELFT>::Bss->setSize(Off);
}
template <class ELFT>
static Symbol *addOptionalSynthetic(SymbolTable<ELFT> &Table, StringRef Name,
OutputSectionBase<ELFT> *Sec,
typename ELFT::uint Val) {
SymbolBody *S = Table.find(Name);
if (!S)
return nullptr;
if (!S->isUndefined() && !S->isShared())
return S->symbol();
return Table.addSynthetic(Name, Sec, Val);
}
// The beginning and the ending of .rel[a].plt section are marked
// with __rel[a]_iplt_{start,end} symbols if it is a statically linked
// executable. The runtime needs these symbols in order to resolve
// all IRELATIVE relocs on startup. For dynamic executables, we don't
// need these symbols, since IRELATIVE relocs are resolved through GOT
// and PLT. For details, see http://www.airs.com/blog/archives/403.
template <class ELFT> void Writer<ELFT>::addRelIpltSymbols() {
if (isOutputDynamic() || !Out<ELFT>::RelaPlt)
return;
StringRef S = Config->Rela ? "__rela_iplt_start" : "__rel_iplt_start";
addOptionalSynthetic(Symtab, S, Out<ELFT>::RelaPlt, 0);
S = Config->Rela ? "__rela_iplt_end" : "__rel_iplt_end";
addOptionalSynthetic(Symtab, S, Out<ELFT>::RelaPlt,
DefinedSynthetic<ELFT>::SectionEnd);
}
// The linker is expected to define some symbols depending on
// the linking result. This function defines such symbols.
template <class ELFT> void Writer<ELFT>::addReservedSymbols() {
if (Config->EMachine == EM_MIPS) {
// Define _gp for MIPS. st_value of _gp symbol will be updated by Writer
// so that it points to an absolute address which is relative to GOT.
// See "Global Data Symbols" in Chapter 6 in the following document:
// ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
Symtab.addSynthetic("_gp", Out<ELFT>::Got, MipsGPOffset);
// On MIPS O32 ABI, _gp_disp is a magic symbol designates offset between
// start of function and 'gp' pointer into GOT.
Symbol *Sym =
addOptionalSynthetic(Symtab, "_gp_disp", Out<ELFT>::Got, MipsGPOffset);
if (Sym)
ElfSym<ELFT>::MipsGpDisp = Sym->body();
// The __gnu_local_gp is a magic symbol equal to the current value of 'gp'
// pointer. This symbol is used in the code generated by .cpload pseudo-op
// in case of using -mno-shared option.
// https://sourceware.org/ml/binutils/2004-12/msg00094.html
addOptionalSynthetic(Symtab, "__gnu_local_gp", Out<ELFT>::Got,
MipsGPOffset);
}
// In the assembly for 32 bit x86 the _GLOBAL_OFFSET_TABLE_ symbol
// is magical and is used to produce a R_386_GOTPC relocation.
// The R_386_GOTPC relocation value doesn't actually depend on the
// symbol value, so it could use an index of STN_UNDEF which, according
// to the spec, means the symbol value is 0.
// Unfortunately both gas and MC keep the _GLOBAL_OFFSET_TABLE_ symbol in
// the object file.
// The situation is even stranger on x86_64 where the assembly doesn't
// need the magical symbol, but gas still puts _GLOBAL_OFFSET_TABLE_ as
// an undefined symbol in the .o files.
// Given that the symbol is effectively unused, we just create a dummy
// hidden one to avoid the undefined symbol error.
if (!Config->Relocatable)
Symtab.addIgnored("_GLOBAL_OFFSET_TABLE_");
// __tls_get_addr is defined by the dynamic linker for dynamic ELFs. For
// static linking the linker is required to optimize away any references to
// __tls_get_addr, so it's not defined anywhere. Create a hidden definition
// to avoid the undefined symbol error.
if (!isOutputDynamic())
Symtab.addIgnored("__tls_get_addr");
auto Define = [this](StringRef S, DefinedRegular<ELFT> *&Sym1,
DefinedRegular<ELFT> *&Sym2) {
Sym1 = Symtab.addIgnored(S, STV_DEFAULT);
// The name without the underscore is not a reserved name,
// so it is defined only when there is a reference against it.
assert(S.startswith("_"));
S = S.substr(1);
if (SymbolBody *B = Symtab.find(S))
if (B->isUndefined())
Sym2 = Symtab.addAbsolute(S, STV_DEFAULT);
};
Define("_end", ElfSym<ELFT>::End, ElfSym<ELFT>::End2);
Define("_etext", ElfSym<ELFT>::Etext, ElfSym<ELFT>::Etext2);
Define("_edata", ElfSym<ELFT>::Edata, ElfSym<ELFT>::Edata2);
}
// Sort input sections by section name suffixes for
// __attribute__((init_priority(N))).
template <class ELFT> static void sortInitFini(OutputSectionBase<ELFT> *S) {
if (S)
reinterpret_cast<OutputSection<ELFT> *>(S)->sortInitFini();
}
// Sort input sections by the special rule for .ctors and .dtors.
template <class ELFT> static void sortCtorsDtors(OutputSectionBase<ELFT> *S) {
if (S)
reinterpret_cast<OutputSection<ELFT> *>(S)->sortCtorsDtors();
}
// Create output section objects and add them to OutputSections.
template <class ELFT> void Writer<ELFT>::createSections() {
// Create output sections for input object file sections.
std::vector<OutputSectionBase<ELFT> *> RegularSections;
OutputSectionFactory<ELFT> Factory;
for (const std::unique_ptr<elf::ObjectFile<ELFT>> &F :
Symtab.getObjectFiles()) {
for (InputSectionBase<ELFT> *C : F->getSections()) {
if (isDiscarded(C)) {
reportDiscarded(C, F);
continue;
}
OutputSectionBase<ELFT> *Sec;
bool IsNew;
std::tie(Sec, IsNew) = Factory.create(C, getOutputSectionName(C));
if (IsNew) {
OwningSections.emplace_back(Sec);
OutputSections.push_back(Sec);
RegularSections.push_back(Sec);
}
Sec->addSection(C);
}
}
// If we have a .opd section (used under PPC64 for function descriptors),
// store a pointer to it here so that we can use it later when processing
// relocations.
Out<ELFT>::Opd = Factory.lookup(".opd", SHT_PROGBITS, SHF_WRITE | SHF_ALLOC);
Out<ELFT>::Dynamic->PreInitArraySec = Factory.lookup(
".preinit_array", SHT_PREINIT_ARRAY, SHF_WRITE | SHF_ALLOC);
Out<ELFT>::Dynamic->InitArraySec =
Factory.lookup(".init_array", SHT_INIT_ARRAY, SHF_WRITE | SHF_ALLOC);
Out<ELFT>::Dynamic->FiniArraySec =
Factory.lookup(".fini_array", SHT_FINI_ARRAY, SHF_WRITE | SHF_ALLOC);
// Sort section contents for __attribute__((init_priority(N)).
sortInitFini(Out<ELFT>::Dynamic->InitArraySec);
sortInitFini(Out<ELFT>::Dynamic->FiniArraySec);
sortCtorsDtors(Factory.lookup(".ctors", SHT_PROGBITS, SHF_WRITE | SHF_ALLOC));
sortCtorsDtors(Factory.lookup(".dtors", SHT_PROGBITS, SHF_WRITE | SHF_ALLOC));
// The linker needs to define SECNAME_start, SECNAME_end and SECNAME_stop
// symbols for sections, so that the runtime can get the start and end
// addresses of each section by section name. Add such symbols.
if (!Config->Relocatable) {
addStartEndSymbols();
for (OutputSectionBase<ELFT> *Sec : RegularSections)
addStartStopSymbols(Sec);
}
// Add _DYNAMIC symbol. Unlike GNU gold, our _DYNAMIC symbol has no type.
// It should be okay as no one seems to care about the type.
// Even the author of gold doesn't remember why gold behaves that way.
// https://sourceware.org/ml/binutils/2002-03/msg00360.html
if (isOutputDynamic())
Symtab.addSynthetic("_DYNAMIC", Out<ELFT>::Dynamic, 0);
// Define __rel[a]_iplt_{start,end} symbols if needed.
addRelIpltSymbols();
// Add scripted symbols with zero values now.
// Real values will be assigned later
Script<ELFT>::X->addScriptedSymbols();
if (!Out<ELFT>::EhFrame->empty()) {
OutputSections.push_back(Out<ELFT>::EhFrame);
Out<ELFT>::EhFrame->finalize();
}
// Scan relocations. This must be done after every symbol is declared so that
// we can correctly decide if a dynamic relocation is needed.
for (const std::unique_ptr<elf::ObjectFile<ELFT>> &F :
Symtab.getObjectFiles()) {
for (InputSectionBase<ELFT> *C : F->getSections()) {
if (isDiscarded(C))
continue;
if (auto *S = dyn_cast<InputSection<ELFT>>(C)) {
scanRelocations(*S);
continue;
}
if (auto *S = dyn_cast<EhInputSection<ELFT>>(C))
if (S->RelocSection)
scanRelocations(*S, *S->RelocSection);
}
}
for (OutputSectionBase<ELFT> *Sec : OutputSections)
Sec->assignOffsets();
// Now that we have defined all possible symbols including linker-
// synthesized ones. Visit all symbols to give the finishing touches.
std::vector<DefinedCommon *> CommonSymbols;
for (Symbol *S : Symtab.getSymbols()) {
SymbolBody *Body = S->body();
// We only report undefined symbols in regular objects. This means that we
// will accept an undefined reference in bitcode if it can be optimized out.
if (S->IsUsedInRegularObj && Body->isUndefined() && !S->isWeak())
reportUndefined<ELFT>(Symtab, Body);
if (auto *C = dyn_cast<DefinedCommon>(Body))
CommonSymbols.push_back(C);
if (!includeInSymtab<ELFT>(*Body))
continue;
if (Out<ELFT>::SymTab)
Out<ELFT>::SymTab->addSymbol(Body);
if (isOutputDynamic() && S->includeInDynsym()) {
Out<ELFT>::DynSymTab->addSymbol(Body);
if (auto *SS = dyn_cast<SharedSymbol<ELFT>>(Body))
if (SS->File->isNeeded())
Out<ELFT>::VerNeed->addSymbol(SS);
}
}
// Do not proceed if there was an undefined symbol.
if (HasError)
return;
addCommonSymbols(CommonSymbols);
// So far we have added sections from input object files.
// This function adds linker-created Out<ELFT>::* sections.
addPredefinedSections();
std::stable_sort(OutputSections.begin(), OutputSections.end(),
compareSections<ELFT>);
unsigned I = 1;
for (OutputSectionBase<ELFT> *Sec : OutputSections) {
Sec->SectionIndex = I++;
Sec->setSHName(Out<ELFT>::ShStrTab->addString(Sec->getName()));
}
// Finalizers fix each section's size.
// .dynsym is finalized early since that may fill up .gnu.hash.
if (isOutputDynamic())
Out<ELFT>::DynSymTab->finalize();
// Fill other section headers. The dynamic table is finalized
// at the end because some tags like RELSZ depend on result
// of finalizing other sections. The dynamic string table is
// finalized once the .dynamic finalizer has added a few last
// strings. See DynamicSection::finalize()
for (OutputSectionBase<ELFT> *Sec : OutputSections)
if (Sec != Out<ELFT>::DynStrTab && Sec != Out<ELFT>::Dynamic)
Sec->finalize();
if (isOutputDynamic())
Out<ELFT>::Dynamic->finalize();
// Now that all output offsets are fixed. Finalize mergeable sections
// to fix their maps from input offsets to output offsets.
for (OutputSectionBase<ELFT> *Sec : OutputSections)
Sec->finalizePieces();
}
template <class ELFT> bool Writer<ELFT>::needsGot() {
if (!Out<ELFT>::Got->empty())
return true;
// We add the .got section to the result for dynamic MIPS target because
// its address and properties are mentioned in the .dynamic section.
if (Config->EMachine == EM_MIPS)
return true;
// If we have a relocation that is relative to GOT (such as GOTOFFREL),
// we need to emit a GOT even if it's empty.
return Out<ELFT>::Got->HasGotOffRel;
}
// This function add Out<ELFT>::* sections to OutputSections.
template <class ELFT> void Writer<ELFT>::addPredefinedSections() {
auto Add = [&](OutputSectionBase<ELFT> *C) {
if (C)
OutputSections.push_back(C);
};
// A core file does not usually contain unmodified segments except
// the first page of the executable. Add the build ID section to beginning of
// the file so that the section is included in the first page.
if (Out<ELFT>::BuildId)
OutputSections.insert(OutputSections.begin(), Out<ELFT>::BuildId);
// Add .interp at first because some loaders want to see that section
// on the first page of the executable file when loaded into memory.
if (needsInterpSection())
OutputSections.insert(OutputSections.begin(), Out<ELFT>::Interp);
// This order is not the same as the final output order
// because we sort the sections using their attributes below.
Add(Out<ELFT>::SymTab);
Add(Out<ELFT>::ShStrTab);
Add(Out<ELFT>::StrTab);
if (isOutputDynamic()) {
Add(Out<ELFT>::DynSymTab);
bool HasVerNeed = Out<ELFT>::VerNeed->getNeedNum() != 0;
if (Out<ELFT>::VerDef || HasVerNeed)
Add(Out<ELFT>::VerSym);
Add(Out<ELFT>::VerDef);
if (HasVerNeed)
Add(Out<ELFT>::VerNeed);
Add(Out<ELFT>::GnuHashTab);
Add(Out<ELFT>::HashTab);
Add(Out<ELFT>::Dynamic);
Add(Out<ELFT>::DynStrTab);
if (Out<ELFT>::RelaDyn->hasRelocs())
Add(Out<ELFT>::RelaDyn);
Add(Out<ELFT>::MipsRldMap);
}
// We always need to add rel[a].plt to output if it has entries.
// Even during static linking it can contain R_[*]_IRELATIVE relocations.
if (Out<ELFT>::RelaPlt && Out<ELFT>::RelaPlt->hasRelocs()) {
Add(Out<ELFT>::RelaPlt);
Out<ELFT>::RelaPlt->Static = !isOutputDynamic();
}
if (needsGot())
Add(Out<ELFT>::Got);
if (Out<ELFT>::GotPlt && !Out<ELFT>::GotPlt->empty())
Add(Out<ELFT>::GotPlt);
if (!Out<ELFT>::Plt->empty())
Add(Out<ELFT>::Plt);
if (!Out<ELFT>::EhFrame->empty())
Add(Out<ELFT>::EhFrameHdr);
if (Out<ELFT>::Bss->getSize() > 0)
Add(Out<ELFT>::Bss);
}
// The linker is expected to define SECNAME_start and SECNAME_end
// symbols for a few sections. This function defines them.
template <class ELFT> void Writer<ELFT>::addStartEndSymbols() {
auto Define = [&](StringRef Start, StringRef End,
OutputSectionBase<ELFT> *OS) {
if (OS) {
this->Symtab.addSynthetic(Start, OS, 0);
this->Symtab.addSynthetic(End, OS, DefinedSynthetic<ELFT>::SectionEnd);
} else {
addOptionalSynthetic(this->Symtab, Start,
(OutputSectionBase<ELFT> *)nullptr, 0);
addOptionalSynthetic(this->Symtab, End,
(OutputSectionBase<ELFT> *)nullptr, 0);
}
};
Define("__preinit_array_start", "__preinit_array_end",
Out<ELFT>::Dynamic->PreInitArraySec);
Define("__init_array_start", "__init_array_end",
Out<ELFT>::Dynamic->InitArraySec);
Define("__fini_array_start", "__fini_array_end",
Out<ELFT>::Dynamic->FiniArraySec);
}
// If a section name is valid as a C identifier (which is rare because of
// the leading '.'), linkers are expected to define __start_<secname> and
// __stop_<secname> symbols. They are at beginning and end of the section,
// respectively. This is not requested by the ELF standard, but GNU ld and
// gold provide the feature, and used by many programs.
template <class ELFT>
void Writer<ELFT>::addStartStopSymbols(OutputSectionBase<ELFT> *Sec) {
StringRef S = Sec->getName();
if (!isValidCIdentifier(S))
return;
StringSaver Saver(Alloc);
StringRef Start = Saver.save("__start_" + S);
StringRef Stop = Saver.save("__stop_" + S);
if (SymbolBody *B = Symtab.find(Start))
if (B->isUndefined())
Symtab.addSynthetic(Start, Sec, 0);
if (SymbolBody *B = Symtab.find(Stop))
if (B->isUndefined())
Symtab.addSynthetic(Stop, Sec, DefinedSynthetic<ELFT>::SectionEnd);
}
template <class ELFT> static bool needsPtLoad(OutputSectionBase<ELFT> *Sec) {
if (!(Sec->getFlags() & SHF_ALLOC))
return false;
// Don't allocate VA space for TLS NOBITS sections. The PT_TLS PHDR is
// responsible for allocating space for them, not the PT_LOAD that
// contains the TLS initialization image.
if (Sec->getFlags() & SHF_TLS && Sec->getType() == SHT_NOBITS)
return false;
return true;
}
static uint32_t toPhdrFlags(uint64_t Flags) {
uint32_t Ret = PF_R;
if (Flags & SHF_WRITE)
Ret |= PF_W;
if (Flags & SHF_EXECINSTR)
Ret |= PF_X;
return Ret;
}
// Decide which program headers to create and which sections to include in each
// one.
template <class ELFT> void Writer<ELFT>::createPhdrs() {
auto AddHdr = [this](unsigned Type, unsigned Flags) {
return &*Phdrs.emplace(Phdrs.end(), Type, Flags);
};
auto AddSec = [](Phdr &Hdr, OutputSectionBase<ELFT> *Sec) {
Hdr.Last = Sec;
if (!Hdr.First)
Hdr.First = Sec;
Hdr.H.p_align = std::max<uintX_t>(Hdr.H.p_align, Sec->getAlignment());
};
// The first phdr entry is PT_PHDR which describes the program header itself.
Phdr &Hdr = *AddHdr(PT_PHDR, PF_R);
AddSec(Hdr, Out<ELFT>::ProgramHeaders);
// PT_INTERP must be the second entry if exists.
if (needsInterpSection()) {
Phdr &Hdr = *AddHdr(PT_INTERP, toPhdrFlags(Out<ELFT>::Interp->getFlags()));
AddSec(Hdr, Out<ELFT>::Interp);
}
// Add the first PT_LOAD segment for regular output sections.
uintX_t Flags = PF_R;
Phdr *Load = AddHdr(PT_LOAD, Flags);
AddSec(*Load, Out<ELFT>::ElfHeader);
AddSec(*Load, Out<ELFT>::ProgramHeaders);
Phdr TlsHdr(PT_TLS, PF_R);
Phdr RelRo(PT_GNU_RELRO, PF_R);
Phdr Note(PT_NOTE, PF_R);
for (OutputSectionBase<ELFT> *Sec : OutputSections) {
if (!(Sec->getFlags() & SHF_ALLOC))
break;
// If we meet TLS section then we create TLS header
// and put all TLS sections inside for futher use when
// assign addresses.
if (Sec->getFlags() & SHF_TLS)
AddSec(TlsHdr, Sec);
if (!needsPtLoad<ELFT>(Sec))
continue;
// If flags changed then we want new load segment.
uintX_t NewFlags = toPhdrFlags(Sec->getFlags());
if (Flags != NewFlags) {
Load = AddHdr(PT_LOAD, NewFlags);
Flags = NewFlags;
}
AddSec(*Load, Sec);
if (isRelroSection(Sec))
AddSec(RelRo, Sec);
if (Sec->getType() == SHT_NOTE)
AddSec(Note, Sec);
}
// Add the TLS segment unless it's empty.
if (TlsHdr.First)
Phdrs.push_back(std::move(TlsHdr));
// Add an entry for .dynamic.
if (isOutputDynamic()) {
Phdr &H = *AddHdr(PT_DYNAMIC, toPhdrFlags(Out<ELFT>::Dynamic->getFlags()));
AddSec(H, Out<ELFT>::Dynamic);
}
// PT_GNU_RELRO includes all sections that should be marked as
// read-only by dynamic linker after proccessing relocations.
if (RelRo.First)
Phdrs.push_back(std::move(RelRo));
// PT_GNU_EH_FRAME is a special section pointing on .eh_frame_hdr.
if (!Out<ELFT>::EhFrame->empty() && Out<ELFT>::EhFrameHdr) {
Phdr &Hdr = *AddHdr(PT_GNU_EH_FRAME,
toPhdrFlags(Out<ELFT>::EhFrameHdr->getFlags()));
AddSec(Hdr, Out<ELFT>::EhFrameHdr);
}
// PT_GNU_STACK is a special section to tell the loader to make the
// pages for the stack non-executable.
if (!Config->ZExecStack)
AddHdr(PT_GNU_STACK, PF_R | PF_W);
if (Note.First)
Phdrs.push_back(std::move(Note));
Out<ELFT>::ProgramHeaders->setSize(sizeof(Elf_Phdr) * Phdrs.size());
}
// The first section of each PT_LOAD and the first section after PT_GNU_RELRO
// have to be page aligned so that the dynamic linker can set the permissions.
template <class ELFT> void Writer<ELFT>::fixSectionAlignments() {
for (const Phdr &P : Phdrs)
if (P.H.p_type == PT_LOAD)
P.First->PageAlign = true;
for (const Phdr &P : Phdrs) {
if (P.H.p_type != PT_GNU_RELRO)
continue;
// Find the first section after PT_GNU_RELRO. If it is in a PT_LOAD we
// have to align it to a page.
auto End = OutputSections.end();
auto I = std::find(OutputSections.begin(), End, P.Last);
if (I == End || (I + 1) == End)
continue;
OutputSectionBase<ELFT> *Sec = *(I + 1);
if (needsPtLoad(Sec))
Sec->PageAlign = true;
}
}
// We should set file offsets and VAs for elf header and program headers
// sections. These are special, we do not include them into output sections
// list, but have them to simplify the code.
template <class ELFT> void Writer<ELFT>::fixHeaders() {
uintX_t BaseVA = ScriptConfig->DoLayout ? 0 : Config->ImageBase;
Out<ELFT>::ElfHeader->setVA(BaseVA);
uintX_t Off = Out<ELFT>::ElfHeader->getSize();
Out<ELFT>::ProgramHeaders->setVA(Off + BaseVA);
}
// Assign VAs (addresses at run-time) to output sections.
template <class ELFT> void Writer<ELFT>::assignAddresses() {
uintX_t VA = Config->ImageBase + Out<ELFT>::ElfHeader->getSize() +
Out<ELFT>::ProgramHeaders->getSize();
uintX_t ThreadBssOffset = 0;
for (OutputSectionBase<ELFT> *Sec : OutputSections) {
uintX_t Alignment = Sec->getAlignment();
if (Sec->PageAlign)
Alignment = std::max<uintX_t>(Alignment, Target->PageSize);
// We only assign VAs to allocated sections.
if (needsPtLoad<ELFT>(Sec)) {
VA = alignTo(VA, Alignment);
Sec->setVA(VA);
VA += Sec->getSize();
} else if (Sec->getFlags() & SHF_TLS && Sec->getType() == SHT_NOBITS) {
uintX_t TVA = VA + ThreadBssOffset;
TVA = alignTo(TVA, Alignment);
Sec->setVA(TVA);
ThreadBssOffset = TVA - VA + Sec->getSize();
}
}
}
// Adjusts the file alignment for a given output section and returns
// its new file offset. The file offset must be the same with its
// virtual address (modulo the page size) so that the loader can load
// executables without any address adjustment.
template <class ELFT, class uintX_t>
static uintX_t getFileAlignment(uintX_t Off, OutputSectionBase<ELFT> *Sec) {
uintX_t Alignment = Sec->getAlignment();
if (Sec->PageAlign)
Alignment = std::max<uintX_t>(Alignment, Target->PageSize);
Off = alignTo(Off, Alignment);
// Relocatable output does not have program headers
// and does not need any other offset adjusting.
if (Config->Relocatable || !(Sec->getFlags() & SHF_ALLOC))
return Off;
return alignTo(Off, Target->PageSize, Sec->getVA());
}
// Assign file offsets to output sections.
template <class ELFT> void Writer<ELFT>::assignFileOffsets() {
uintX_t Off = 0;
auto Set = [&](OutputSectionBase<ELFT> *Sec) {
if (Sec->getType() == SHT_NOBITS) {
Sec->setFileOffset(Off);
return;
}
Off = getFileAlignment<ELFT>(Off, Sec);
Sec->setFileOffset(Off);
Off += Sec->getSize();
};
Set(Out<ELFT>::ElfHeader);
Set(Out<ELFT>::ProgramHeaders);
for (OutputSectionBase<ELFT> *Sec : OutputSections)
Set(Sec);
SectionHeaderOff = alignTo(Off, sizeof(uintX_t));
FileSize = SectionHeaderOff + (OutputSections.size() + 1) * sizeof(Elf_Shdr);
}
// Finalize the program headers. We call this function after we assign
// file offsets and VAs to all sections.
template <class ELFT> void Writer<ELFT>::setPhdrs() {
for (Phdr &P : Phdrs) {
Elf_Phdr &H = P.H;
OutputSectionBase<ELFT> *First = P.First;
OutputSectionBase<ELFT> *Last = P.Last;
if (First) {
H.p_filesz = Last->getFileOff() - First->getFileOff();
if (Last->getType() != SHT_NOBITS)
H.p_filesz += Last->getSize();
H.p_memsz = Last->getVA() + Last->getSize() - First->getVA();
H.p_offset = First->getFileOff();
H.p_vaddr = First->getVA();
}
if (H.p_type == PT_LOAD)
H.p_align = Target->PageSize;
else if (H.p_type == PT_GNU_RELRO)
H.p_align = 1;
H.p_paddr = H.p_vaddr;
// The TLS pointer goes after PT_TLS. At least glibc will align it,
// so round up the size to make sure the offsets are correct.
if (H.p_type == PT_TLS) {
Out<ELFT>::TlsPhdr = &H;
H.p_memsz = alignTo(H.p_memsz, H.p_align);
}
}
}
static uint32_t getMipsEFlags(bool Is64Bits) {
// FIXME: In fact ELF flags depends on ELF flags of input object files
// and selected emulation. For now just use hard coded values.
if (Is64Bits)
return EF_MIPS_CPIC | EF_MIPS_PIC | EF_MIPS_ARCH_64R2;
uint32_t V = EF_MIPS_CPIC | EF_MIPS_ABI_O32 | EF_MIPS_ARCH_32R2;
if (Config->Shared)
V |= EF_MIPS_PIC;
return V;
}
template <class ELFT> static typename ELFT::uint getEntryAddr() {
if (Symbol *S = Config->EntrySym)
return S->body()->getVA<ELFT>();
if (Config->EntryAddr != uint64_t(-1))
return Config->EntryAddr;
return 0;
}
template <class ELFT> static uint8_t getELFEncoding() {
if (ELFT::TargetEndianness == llvm::support::little)
return ELFDATA2LSB;
return ELFDATA2MSB;
}
static uint16_t getELFType() {
if (Config->Pic)
return ET_DYN;
if (Config->Relocatable)
return ET_REL;
return ET_EXEC;
}
// This function is called after we have assigned address and size
// to each section. This function fixes some predefined absolute
// symbol values that depend on section address and size.
template <class ELFT> void Writer<ELFT>::fixAbsoluteSymbols() {
auto Set = [](DefinedRegular<ELFT> *S1, DefinedRegular<ELFT> *S2, uintX_t V) {
if (S1)
S1->Value = V;
if (S2)
S2->Value = V;
};
// _etext is the first location after the last read-only loadable segment.
// _edata is the first location after the last read-write loadable segment.
// _end is the first location after the uninitialized data region.
for (Phdr &P : Phdrs) {
Elf_Phdr &H = P.H;
if (H.p_type != PT_LOAD)
continue;
Set(ElfSym<ELFT>::End, ElfSym<ELFT>::End2, H.p_vaddr + H.p_memsz);
uintX_t Val = H.p_vaddr + H.p_filesz;
if (H.p_flags & PF_W)
Set(ElfSym<ELFT>::Edata, ElfSym<ELFT>::Edata2, Val);
else
Set(ElfSym<ELFT>::Etext, ElfSym<ELFT>::Etext2, Val);
}
}
template <class ELFT> void Writer<ELFT>::writeHeader() {
uint8_t *Buf = Buffer->getBufferStart();
memcpy(Buf, "\177ELF", 4);
auto &FirstObj = cast<ELFFileBase<ELFT>>(*Config->FirstElf);
// Write the ELF header.
auto *EHdr = reinterpret_cast<Elf_Ehdr *>(Buf);
EHdr->e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
EHdr->e_ident[EI_DATA] = getELFEncoding<ELFT>();
EHdr->e_ident[EI_VERSION] = EV_CURRENT;
EHdr->e_ident[EI_OSABI] = FirstObj.getOSABI();
EHdr->e_type = getELFType();
EHdr->e_machine = FirstObj.EMachine;
EHdr->e_version = EV_CURRENT;
EHdr->e_entry = getEntryAddr<ELFT>();
EHdr->e_shoff = SectionHeaderOff;
EHdr->e_ehsize = sizeof(Elf_Ehdr);
EHdr->e_phnum = Phdrs.size();
EHdr->e_shentsize = sizeof(Elf_Shdr);
EHdr->e_shnum = OutputSections.size() + 1;
EHdr->e_shstrndx = Out<ELFT>::ShStrTab->SectionIndex;
if (Config->EMachine == EM_MIPS)
EHdr->e_flags = getMipsEFlags(ELFT::Is64Bits);
if (!Config->Relocatable) {
EHdr->e_phoff = sizeof(Elf_Ehdr);
EHdr->e_phentsize = sizeof(Elf_Phdr);
}
// Write the program header table.
auto *HBuf = reinterpret_cast<Elf_Phdr *>(Buf + EHdr->e_phoff);
for (Phdr &P : Phdrs)
*HBuf++ = P.H;
// Write the section header table. Note that the first table entry is null.
auto *SHdrs = reinterpret_cast<Elf_Shdr *>(Buf + EHdr->e_shoff);
for (OutputSectionBase<ELFT> *Sec : OutputSections)
Sec->writeHeaderTo(++SHdrs);
}
template <class ELFT> void Writer<ELFT>::openFile() {
ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
FileOutputBuffer::create(Config->OutputFile, FileSize,
FileOutputBuffer::F_executable);
if (auto EC = BufferOrErr.getError())
error(EC, "failed to open " + Config->OutputFile);
else
Buffer = std::move(*BufferOrErr);
}
// Write section contents to a mmap'ed file.
template <class ELFT> void Writer<ELFT>::writeSections() {
uint8_t *Buf = Buffer->getBufferStart();
// PPC64 needs to process relocations in the .opd section before processing
// relocations in code-containing sections.
if (OutputSectionBase<ELFT> *Sec = Out<ELFT>::Opd) {
Out<ELFT>::OpdBuf = Buf + Sec->getFileOff();
Sec->writeTo(Buf + Sec->getFileOff());
}
for (OutputSectionBase<ELFT> *Sec : OutputSections)
if (Sec != Out<ELFT>::Opd)
Sec->writeTo(Buf + Sec->getFileOff());
}
template <class ELFT> void Writer<ELFT>::writeBuildId() {
BuildIdSection<ELFT> *S = Out<ELFT>::BuildId;
if (!S)
return;
// Compute a hash of all sections except .debug_* sections.
// We skip debug sections because they tend to be very large
// and their contents are very likely to be the same as long as
// other sections are the same.
uint8_t *Start = Buffer->getBufferStart();
uint8_t *Last = Start;
std::vector<ArrayRef<uint8_t>> Regions;
for (OutputSectionBase<ELFT> *Sec : OutputSections) {
uint8_t *End = Start + Sec->getFileOff();
if (!Sec->getName().startswith(".debug_"))
Regions.push_back({Last, End});
Last = End;
}
Regions.push_back({Last, Start + FileSize});
S->writeBuildId(Regions);
}
template void elf::writeResult<ELF32LE>(SymbolTable<ELF32LE> *Symtab);
template void elf::writeResult<ELF32BE>(SymbolTable<ELF32BE> *Symtab);
template void elf::writeResult<ELF64LE>(SymbolTable<ELF64LE> *Symtab);
template void elf::writeResult<ELF64BE>(SymbolTable<ELF64BE> *Symtab);
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