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Diffstat (limited to 'llvm/lib/MC/ELFObjectWriter.cpp')
-rw-r--r--llvm/lib/MC/ELFObjectWriter.cpp185
1 files changed, 84 insertions, 101 deletions
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 69307b617552..e0ea44626b7f 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -116,21 +116,9 @@ struct ELFWriter {
/// Helper struct for containing some precomputed information on symbols.
struct ELFSymbolData {
const MCSymbolELF *Symbol;
- uint32_t SectionIndex;
StringRef Name;
-
- // Support lexicographic sorting.
- bool operator<(const ELFSymbolData &RHS) const {
- unsigned LHSType = Symbol->getType();
- unsigned RHSType = RHS.Symbol->getType();
- if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
- return false;
- if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
- return true;
- if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
- return SectionIndex < RHS.SectionIndex;
- return Name < RHS.Name;
- }
+ uint32_t SectionIndex;
+ uint32_t Order;
};
/// @}
@@ -154,9 +142,9 @@ struct ELFWriter {
// TargetObjectWriter wrappers.
bool is64Bit() const;
- bool hasRelocationAddend() const;
+ bool usesRela(const MCSectionELF &Sec) const;
- void align(unsigned Alignment);
+ uint64_t align(unsigned Alignment);
bool maybeWriteCompression(uint64_t Size,
SmallVectorImpl<char> &CompressedContents,
@@ -206,8 +194,6 @@ public:
MCSectionELF *createRelocationSection(MCContext &Ctx,
const MCSectionELF &Sec);
- const MCSectionELF *createStringTable(MCContext &Ctx);
-
void writeSectionHeader(const MCAsmLayout &Layout,
const SectionIndexMapTy &SectionIndexMap,
const SectionOffsetsTy &SectionOffsets);
@@ -236,6 +222,7 @@ class ELFObjectWriter : public MCObjectWriter {
DenseMap<const MCSymbolELF *, const MCSymbolELF *> Renames;
+ bool SeenGnuAbi = false;
bool EmitAddrsigSection = false;
std::vector<const MCSymbol *> AddrsigSyms;
@@ -251,6 +238,7 @@ public:
: TargetObjectWriter(std::move(MOTW)) {}
void reset() override {
+ SeenGnuAbi = false;
Relocations.clear();
Renames.clear();
MCObjectWriter::reset();
@@ -274,6 +262,8 @@ public:
void executePostLayoutBinding(MCAssembler &Asm,
const MCAsmLayout &Layout) override;
+ void markGnuAbi() override { SeenGnuAbi = true; }
+ bool seenGnuAbi() const { return SeenGnuAbi; }
void emitAddrsigSection() override { EmitAddrsigSection = true; }
void addAddrsigSymbol(const MCSymbol *Sym) override {
AddrsigSyms.push_back(Sym);
@@ -336,9 +326,10 @@ public:
} // end anonymous namespace
-void ELFWriter::align(unsigned Alignment) {
- uint64_t Padding = offsetToAlignment(W.OS.tell(), Align(Alignment));
- W.OS.write_zeros(Padding);
+uint64_t ELFWriter::align(unsigned Alignment) {
+ uint64_t Offset = W.OS.tell(), NewOffset = alignTo(Offset, Alignment);
+ W.OS.write_zeros(NewOffset - Offset);
+ return NewOffset;
}
unsigned ELFWriter::addToSectionTable(const MCSectionELF *Sec) {
@@ -401,8 +392,9 @@ bool ELFWriter::is64Bit() const {
return OWriter.TargetObjectWriter->is64Bit();
}
-bool ELFWriter::hasRelocationAddend() const {
- return OWriter.hasRelocationAddend();
+bool ELFWriter::usesRela(const MCSectionELF &Sec) const {
+ return OWriter.hasRelocationAddend() &&
+ Sec.getType() != ELF::SHT_LLVM_CALL_GRAPH_PROFILE;
}
// Emit the ELF header.
@@ -425,7 +417,10 @@ void ELFWriter::writeHeader(const MCAssembler &Asm) {
W.OS << char(ELF::EV_CURRENT); // e_ident[EI_VERSION]
// e_ident[EI_OSABI]
- W.OS << char(OWriter.TargetObjectWriter->getOSABI());
+ uint8_t OSABI = OWriter.TargetObjectWriter->getOSABI();
+ W.OS << char(OSABI == ELF::ELFOSABI_NONE && OWriter.seenGnuAbi()
+ ? int(ELF::ELFOSABI_GNU)
+ : OSABI);
// e_ident[EI_ABIVERSION]
W.OS << char(OWriter.TargetObjectWriter->getABIVersion());
@@ -457,7 +452,7 @@ void ELFWriter::writeHeader(const MCAssembler &Asm) {
// e_shnum = # of section header ents
W.write<uint16_t>(0);
- // e_shstrndx = Section # of '.shstrtab'
+ // e_shstrndx = Section # of '.strtab'
assert(StringTableIndex < ELF::SHN_LORESERVE);
W.write<uint16_t>(StringTableIndex);
}
@@ -614,23 +609,26 @@ void ELFWriter::computeSymbolTable(
// Symbol table
unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
MCSectionELF *SymtabSection =
- Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize, "");
+ Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize);
SymtabSection->setAlignment(is64Bit() ? Align(8) : Align(4));
SymbolTableIndex = addToSectionTable(SymtabSection);
- align(SymtabSection->getAlignment());
- uint64_t SecStart = W.OS.tell();
+ uint64_t SecStart = align(SymtabSection->getAlignment());
// The first entry is the undefined symbol entry.
Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
std::vector<ELFSymbolData> LocalSymbolData;
std::vector<ELFSymbolData> ExternalSymbolData;
+ MutableArrayRef<std::pair<std::string, size_t>> FileNames =
+ Asm.getFileNames();
+ for (const std::pair<std::string, size_t> &F : FileNames)
+ StrTabBuilder.add(F.first);
// Add the data for the symbols.
bool HasLargeSectionIndex = false;
- for (const MCSymbol &S : Asm.symbols()) {
- const auto &Symbol = cast<MCSymbolELF>(S);
+ for (auto It : llvm::enumerate(Asm.symbols())) {
+ const auto &Symbol = cast<MCSymbolELF>(It.value());
bool Used = Symbol.isUsedInReloc();
bool WeakrefUsed = Symbol.isWeakrefUsedInReloc();
bool isSignature = Symbol.isSignature();
@@ -646,6 +644,7 @@ void ELFWriter::computeSymbolTable(
ELFSymbolData MSD;
MSD.Symbol = cast<MCSymbolELF>(&Symbol);
+ MSD.Order = It.index();
bool Local = Symbol.getBinding() == ELF::STB_LOCAL;
assert(Local || !Symbol.isTemporary());
@@ -711,39 +710,41 @@ void ELFWriter::computeSymbolTable(
if (HasLargeSectionIndex) {
MCSectionELF *SymtabShndxSection =
- Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 4, "");
+ Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0, 4);
SymtabShndxSectionIndex = addToSectionTable(SymtabShndxSection);
SymtabShndxSection->setAlignment(Align(4));
}
- ArrayRef<std::string> FileNames = Asm.getFileNames();
- for (const std::string &Name : FileNames)
- StrTabBuilder.add(Name);
-
StrTabBuilder.finalize();
- // File symbols are emitted first and handled separately from normal symbols,
- // i.e. a non-STT_FILE symbol with the same name may appear.
- for (const std::string &Name : FileNames)
- Writer.writeSymbol(StrTabBuilder.getOffset(Name),
- ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, ELF::STV_DEFAULT,
- ELF::SHN_ABS, true);
-
- // Symbols are required to be in lexicographic order.
- array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
- array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
-
- // Set the symbol indices. Local symbols must come before all other
- // symbols with non-local bindings.
- unsigned Index = FileNames.size() + 1;
+ // Make the first STT_FILE precede previous local symbols.
+ unsigned Index = 1;
+ auto FileNameIt = FileNames.begin();
+ if (!FileNames.empty())
+ FileNames[0].second = 0;
for (ELFSymbolData &MSD : LocalSymbolData) {
+ // Emit STT_FILE symbols before their associated local symbols.
+ for (; FileNameIt != FileNames.end() && FileNameIt->second <= MSD.Order;
+ ++FileNameIt) {
+ Writer.writeSymbol(StrTabBuilder.getOffset(FileNameIt->first),
+ ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, ELF::STV_DEFAULT,
+ ELF::SHN_ABS, true);
+ ++Index;
+ }
+
unsigned StringIndex = MSD.Symbol->getType() == ELF::STT_SECTION
? 0
: StrTabBuilder.getOffset(MSD.Name);
MSD.Symbol->setIndex(Index++);
writeSymbol(Writer, StringIndex, MSD, Layout);
}
+ for (; FileNameIt != FileNames.end(); ++FileNameIt) {
+ Writer.writeSymbol(StrTabBuilder.getOffset(FileNameIt->first),
+ ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, ELF::STV_DEFAULT,
+ ELF::SHN_ABS, true);
+ ++Index;
+ }
// Write the symbol table entries.
LastLocalSymbolIndex = Index;
@@ -785,11 +786,12 @@ MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
return nullptr;
const StringRef SectionName = Sec.getName();
- std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
+ bool Rela = usesRela(Sec);
+ std::string RelaSectionName = Rela ? ".rela" : ".rel";
RelaSectionName += SectionName;
unsigned EntrySize;
- if (hasRelocationAddend())
+ if (Rela)
EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
else
EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
@@ -799,8 +801,8 @@ MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
Flags = ELF::SHF_GROUP;
MCSectionELF *RelaSection = Ctx.createELFRelSection(
- RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
- Flags, EntrySize, Sec.getGroup(), &Sec);
+ RelaSectionName, Rela ? ELF::SHT_RELA : ELF::SHT_REL, Flags, EntrySize,
+ Sec.getGroup(), &Sec);
RelaSection->setAlignment(is64Bit() ? Align(8) : Align(4));
return RelaSection;
}
@@ -925,6 +927,7 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
// Sort the relocation entries. MIPS needs this.
OWriter.TargetObjectWriter->sortRelocs(Asm, Relocs);
+ const bool Rela = usesRela(Sec);
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
const ELFRelocationEntry &Entry = Relocs[e - i - 1];
unsigned Index = Entry.Symbol ? Entry.Symbol->getIndex() : 0;
@@ -943,7 +946,7 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
ERE64.setSymbolAndType(Index, Entry.Type);
write(ERE64.r_info);
}
- if (hasRelocationAddend())
+ if (Rela)
write(Entry.Addend);
} else {
write(uint32_t(Entry.Offset));
@@ -952,7 +955,7 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
ERE32.setSymbolAndType(Index, Entry.Type);
write(ERE32.r_info);
- if (hasRelocationAddend())
+ if (Rela)
write(uint32_t(Entry.Addend));
if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
@@ -977,12 +980,6 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
}
}
-const MCSectionELF *ELFWriter::createStringTable(MCContext &Ctx) {
- const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1];
- StrTabBuilder.write(W.OS);
- return StrtabSection;
-}
-
void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
uint32_t GroupSymbolIndex, uint64_t Offset,
uint64_t Size, const MCSectionELF &Section) {
@@ -1097,10 +1094,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
if (Mode == DwoOnly && !isDwoSection(Section))
continue;
- align(Section.getAlignment());
-
// Remember the offset into the file for this section.
- uint64_t SecStart = W.OS.tell();
+ const uint64_t SecStart = align(Section.getAlignment());
const MCSymbolELF *SignatureSymbol = Section.getGroup();
writeSectionData(Asm, Section, Layout);
@@ -1111,10 +1106,10 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
if (SignatureSymbol) {
- Asm.registerSymbol(*SignatureSymbol);
unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
if (!GroupIdx) {
- MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
+ MCSectionELF *Group =
+ Ctx.createELFGroupSection(SignatureSymbol, Section.isComdat());
GroupIdx = addToSectionTable(Group);
Group->setAlignment(Align(4));
Groups.push_back(Group);
@@ -1135,23 +1130,13 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
OWriter.TargetObjectWriter->addTargetSectionFlags(Ctx, Section);
}
- MCSectionELF *CGProfileSection = nullptr;
- if (!Asm.CGProfile.empty()) {
- CGProfileSection = Ctx.getELFSection(".llvm.call-graph-profile",
- ELF::SHT_LLVM_CALL_GRAPH_PROFILE,
- ELF::SHF_EXCLUDE, 16, "");
- SectionIndexMap[CGProfileSection] = addToSectionTable(CGProfileSection);
- }
-
for (MCSectionELF *Group : Groups) {
- align(Group->getAlignment());
-
// Remember the offset into the file for this section.
- uint64_t SecStart = W.OS.tell();
+ const uint64_t SecStart = align(Group->getAlignment());
const MCSymbol *SignatureSymbol = Group->getGroup();
assert(SignatureSymbol);
- write(uint32_t(ELF::GRP_COMDAT));
+ write(uint32_t(Group->isComdat() ? unsigned(ELF::GRP_COMDAT) : 0));
for (const MCSectionELF *Member : GroupMembers[SignatureSymbol]) {
uint32_t SecIndex = SectionIndexMap.lookup(Member);
write(SecIndex);
@@ -1178,10 +1163,8 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
SectionOffsets);
for (MCSectionELF *RelSection : Relocations) {
- align(RelSection->getAlignment());
-
// Remember the offset into the file for this section.
- uint64_t SecStart = W.OS.tell();
+ const uint64_t SecStart = align(RelSection->getAlignment());
writeRelocations(Asm,
cast<MCSectionELF>(*RelSection->getLinkedToSection()));
@@ -1198,28 +1181,13 @@ uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
}
}
- if (CGProfileSection) {
- uint64_t SecStart = W.OS.tell();
- for (const MCAssembler::CGProfileEntry &CGPE : Asm.CGProfile) {
- W.write<uint32_t>(CGPE.From->getSymbol().getIndex());
- W.write<uint32_t>(CGPE.To->getSymbol().getIndex());
- W.write<uint64_t>(CGPE.Count);
- }
- uint64_t SecEnd = W.OS.tell();
- SectionOffsets[CGProfileSection] = std::make_pair(SecStart, SecEnd);
- }
-
{
uint64_t SecStart = W.OS.tell();
- const MCSectionELF *Sec = createStringTable(Ctx);
- uint64_t SecEnd = W.OS.tell();
- SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd);
+ StrTabBuilder.write(W.OS);
+ SectionOffsets[StrtabSection] = std::make_pair(SecStart, W.OS.tell());
}
- uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
- align(NaturalAlignment);
-
- const uint64_t SectionHeaderOffset = W.OS.tell();
+ const uint64_t SectionHeaderOffset = align(is64Bit() ? 8 : 4);
// ... then the section header table ...
writeSectionHeader(Layout, SectionIndexMap, SectionOffsets);
@@ -1282,7 +1250,7 @@ void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
Alias->setVisibility(Symbol.getVisibility());
Alias->setOther(Symbol.getOther());
- if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
+ if (!Symbol.isUndefined() && S.KeepOriginalSym)
continue;
if (Symbol.isUndefined() && Rest.startswith("@@") &&
@@ -1397,6 +1365,17 @@ bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
if (TargetObjectWriter->getEMachine() == ELF::EM_386 &&
Type == ELF::R_386_GOTOFF)
return true;
+
+ // ld.lld handles R_MIPS_HI16/R_MIPS_LO16 separately, not as a whole, so
+ // it doesn't know that an R_MIPS_HI16 with implicit addend 1 and an
+ // R_MIPS_LO16 with implicit addend -32768 represents 32768, which is in
+ // range of a MergeInputSection. We could introduce a new RelExpr member
+ // (like R_RISCV_PC_INDIRECT for R_RISCV_PCREL_HI20 / R_RISCV_PCREL_LO12)
+ // but the complexity is unnecessary given that GNU as keeps the original
+ // symbol for this case as well.
+ if (TargetObjectWriter->getEMachine() == ELF::EM_MIPS &&
+ !hasRelocationAddend())
+ return true;
}
// Most TLS relocations use a got, so they need the symbol. Even those that
@@ -1476,7 +1455,11 @@ void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
return;
unsigned Type = TargetObjectWriter->getRelocType(Ctx, Target, Fixup, IsPCRel);
- bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
+ const auto *Parent = cast<MCSectionELF>(Fragment->getParent());
+ // Emiting relocation with sybmol for CG Profile to help with --cg-profile.
+ bool RelocateWithSymbol =
+ shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type) ||
+ (Parent->getType() == ELF::SHT_LLVM_CALL_GRAPH_PROFILE);
uint64_t Addend = 0;
FixedValue = !RelocateWithSymbol && SymA && !SymA->isUndefined()
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-27 22:26:44 +0000