#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCValue.h"
+#include "llvm/MC/StringTableBuilder.h"
+#include "llvm/Support/Compression.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/ELF.h"
uint8_t other, uint32_t shndx, bool Reserved);
};
+struct ELFRelocationEntry {
+ uint64_t Offset; // Where is the relocation.
+ const MCSymbol *Symbol; // The symbol to relocate with.
+ unsigned Type; // The type of the relocation.
+ uint64_t Addend; // The addend to use.
+
+ ELFRelocationEntry(uint64_t Offset, const MCSymbol *Symbol, unsigned Type,
+ uint64_t Addend)
+ : Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend) {}
+};
+
class ELFObjectWriter : public MCObjectWriter {
FragmentWriter FWriter;
static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
- static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
+ static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolData &Data,
bool Used, bool Renamed);
- static bool isLocal(const MCSymbolData &Data, bool isSignature,
- bool isUsedInReloc);
+ static bool isLocal(const MCSymbolData &Data, bool isUsedInReloc);
static bool IsELFMetaDataSection(const MCSectionData &SD);
static uint64_t DataSectionSize(const MCSectionData &SD);
static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
MCSymbolData *SymbolData;
uint64_t StringIndex;
uint32_t SectionIndex;
+ StringRef Name;
// Support lexicographic sorting.
bool operator<(const ELFSymbolData &RHS) const {
- return SymbolData->getSymbol().getName() <
- RHS.SymbolData->getSymbol().getName();
+ unsigned LHSType = MCELF::GetType(*SymbolData);
+ unsigned RHSType = MCELF::GetType(*RHS.SymbolData);
+ 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;
}
};
SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
DenseMap<const MCSymbol *, const MCSymbol *> Renames;
- llvm::DenseMap<const MCSectionData*,
- std::vector<ELFRelocationEntry> > Relocations;
- DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
+ llvm::DenseMap<const MCSectionData *, std::vector<ELFRelocationEntry>>
+ Relocations;
+ StringTableBuilder ShStrTabBuilder;
/// @}
/// @name Symbol Table Data
/// @{
- SmallString<256> StringTable;
+ StringTableBuilder StrTabBuilder;
std::vector<uint64_t> FileSymbolData;
std::vector<ELFSymbolData> LocalSymbolData;
std::vector<ELFSymbolData> ExternalSymbolData;
unsigned ShstrtabIndex;
- const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
- const MCValue &Target,
- const MCFragment &F,
- const MCFixup &Fixup,
- bool IsPCRel) const;
-
// TargetObjectWriter wrappers.
- const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
- const MCValue &Target,
- const MCFragment &F,
- const MCFixup &Fixup,
- bool IsPCRel) const {
- return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
- }
- const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
- const MCFixup &Fixup,
- bool IsPCRel) const {
- return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup,
- IsPCRel);
- }
-
bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
bool hasRelocationAddend() const {
return TargetObjectWriter->hasRelocationAddend();
}
unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
- bool IsPCRel, bool IsRelocWithSymbol,
- int64_t Addend) const {
- return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel,
- IsRelocWithSymbol);
+ bool IsPCRel) const {
+ return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel);
}
public:
const MCAsmLayout &Layout,
SectionIndexMapTy &SectionIndexMap);
+ bool shouldRelocateWithSymbol(const MCAssembler &Asm,
+ const MCSymbolRefExpr *RefA,
+ const MCSymbolData *SD, uint64_t C,
+ unsigned Type) const;
+
void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment, const MCFixup &Fixup,
- MCValue Target, uint64_t &FixedValue) override;
+ MCValue Target, bool &IsPCRel,
+ uint64_t &FixedValue) override;
uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
const MCSymbol *S);
/// \param NumRegularSections - Number of non-relocation sections.
void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
const SectionIndexMapTy &SectionIndexMap,
- RevGroupMapTy RevGroupMap,
+ const RevGroupMapTy &RevGroupMap,
unsigned NumRegularSections);
void ComputeIndexMap(MCAssembler &Asm,
void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
RelMapTy &RelMap);
+ void CompressDebugSections(MCAssembler &Asm, MCAsmLayout &Layout);
+
void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
const RelMapTy &RelMap);
Write16(ShstrtabIndex);
}
-uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &OrigData,
+uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
const MCAsmLayout &Layout) {
- MCSymbolData *Data = &OrigData;
- if (Data->isCommon() && Data->isExternal())
- return Data->getCommonAlignment();
-
- const MCSymbol *Symbol = &Data->getSymbol();
- bool IsThumbFunc = OrigData.getFlags() & ELF_Other_ThumbFunc;
+ if (Data.isCommon() && Data.isExternal())
+ return Data.getCommonAlignment();
- uint64_t Res = 0;
- if (Symbol->isVariable()) {
- const MCExpr *Expr = Symbol->getVariableValue();
- MCValue Value;
- if (!Expr->EvaluateAsRelocatable(Value, &Layout))
- llvm_unreachable("Invalid expression");
+ uint64_t Res;
+ if (!Layout.getSymbolOffset(&Data, Res))
+ return 0;
- assert(!Value.getSymB());
-
- Res = Value.getConstant();
-
- if (const MCSymbolRefExpr *A = Value.getSymA()) {
- Symbol = &A->getSymbol();
- Data = &Layout.getAssembler().getSymbolData(*Symbol);
- } else {
- Symbol = 0;
- Data = 0;
- }
- }
-
- if (IsThumbFunc)
+ if (Layout.getAssembler().isThumbFunc(&Data.getSymbol()))
Res |= 1;
- if (!Symbol || !Symbol->isInSection())
- return Res;
-
- Res += Layout.getSymbolOffset(Data);
-
return Res;
}
// The presence of symbol versions causes undefined symbols and
// versions declared with @@@ to be renamed.
- for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
- ie = Asm.symbol_end(); it != ie; ++it) {
- const MCSymbol &Alias = it->getSymbol();
- const MCSymbol &Symbol = Alias.AliasedSymbol();
- MCSymbolData &SD = Asm.getSymbolData(Symbol);
+ for (MCSymbolData &OriginalData : Asm.symbols()) {
+ const MCSymbol &Alias = OriginalData.getSymbol();
// Not an alias.
- if (&Symbol == &Alias)
+ if (!Alias.isVariable())
+ continue;
+ auto *Ref = dyn_cast<MCSymbolRefExpr>(Alias.getVariableValue());
+ if (!Ref)
continue;
+ const MCSymbol &Symbol = Ref->getSymbol();
+ MCSymbolData &SD = Asm.getSymbolData(Symbol);
StringRef AliasName = Alias.getName();
size_t Pos = AliasName.find('@');
// Aliases defined with .symvar copy the binding from the symbol they alias.
// This is the first place we are able to copy this information.
- it->setExternal(SD.isExternal());
- MCELF::SetBinding(*it, MCELF::GetBinding(SD));
+ OriginalData.setExternal(SD.isExternal());
+ MCELF::SetBinding(OriginalData, MCELF::GetBinding(SD));
StringRef Rest = AliasName.substr(Pos);
if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
return Type;
}
-static const MCSymbol *getBaseSymbol(const MCAsmLayout &Layout,
- const MCSymbol &Symbol) {
- if (!Symbol.isVariable())
- return &Symbol;
-
- const MCExpr *Expr = Symbol.getVariableValue();
- MCValue Value;
- if (!Expr->EvaluateAsRelocatable(Value, &Layout))
- llvm_unreachable("Invalid Expression");
- assert(!Value.getSymB());
- const MCSymbolRefExpr *A = Value.getSymA();
- if (!A)
- return nullptr;
- return getBaseSymbol(Layout, A->getSymbol());
-}
-
void ELFObjectWriter::WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
const MCAsmLayout &Layout) {
MCSymbolData &OrigData = *MSD.SymbolData;
- const MCSymbol *Base = getBaseSymbol(Layout, OrigData.getSymbol());
+ assert((!OrigData.getFragment() ||
+ (&OrigData.getFragment()->getParent()->getSection() ==
+ &OrigData.getSymbol().getSection())) &&
+ "The symbol's section doesn't match the fragment's symbol");
+ const MCSymbol *Base = Layout.getBaseSymbol(OrigData.getSymbol());
// This has to be in sync with when computeSymbolTable uses SHN_ABS or
// SHN_COMMON.
BaseSD = &Layout.getAssembler().getSymbolData(*Base);
Type = mergeTypeForSet(Type, MCELF::GetType(*BaseSD));
}
- if (OrigData.getFlags() & ELF_Other_ThumbFunc)
- Type = ELF::STT_FUNC;
uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
// Other and Visibility share the same byte with Visibility using the lower
Other |= Visibility;
uint64_t Value = SymbolValue(OrigData, Layout);
- if (OrigData.getFlags() & ELF_Other_ThumbFunc)
- Value |= 1;
uint64_t Size = 0;
const MCExpr *ESize = OrigData.getSize();
SectionIndexMapTy &SectionIndexMap) {
// The string table must be emitted first because we need the index
// into the string table for all the symbol names.
- assert(StringTable.size() && "Missing string table");
// FIXME: Make sure the start of the symbol table is aligned.
WriteSymbol(Writer, MSD, Layout);
}
- // Write out a symbol table entry for each regular section.
- for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
- ++i) {
- const MCSectionELF &Section =
- static_cast<const MCSectionELF&>(i->getSection());
- if (Section.getType() == ELF::SHT_RELA ||
- Section.getType() == ELF::SHT_REL ||
- Section.getType() == ELF::SHT_STRTAB ||
- Section.getType() == ELF::SHT_SYMTAB ||
- Section.getType() == ELF::SHT_SYMTAB_SHNDX)
- continue;
- Writer.writeSymbol(0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT,
- SectionIndexMap.lookup(&Section), false);
- LastLocalSymbolIndex++;
- }
-
for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
ELFSymbolData &MSD = ExternalSymbolData[i];
MCSymbolData &Data = *MSD.SymbolData;
}
}
-const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
- const MCValue &Target,
- const MCFragment &F,
- const MCFixup &Fixup,
- bool IsPCRel) const {
- const MCSymbol &Symbol = Target.getSymA()->getSymbol();
- const MCSymbol &ASymbol = Symbol.AliasedSymbol();
- const MCSymbol *Renamed = Renames.lookup(&Symbol);
- const MCSymbolData &SD = Asm.getSymbolData(Symbol);
-
- if (ASymbol.isUndefined()) {
- if (Renamed)
- return Renamed;
- return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
- }
+// It is always valid to create a relocation with a symbol. It is preferable
+// to use a relocation with a section if that is possible. Using the section
+// allows us to omit some local symbols from the symbol table.
+bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
+ const MCSymbolRefExpr *RefA,
+ const MCSymbolData *SD,
+ uint64_t C,
+ unsigned Type) const {
+ // A PCRel relocation to an absolute value has no symbol (or section). We
+ // represent that with a relocation to a null section.
+ if (!RefA)
+ return false;
- if (SD.isExternal()) {
- if (Renamed)
- return Renamed;
- return &Symbol;
- }
+ MCSymbolRefExpr::VariantKind Kind = RefA->getKind();
+ switch (Kind) {
+ default:
+ break;
+ // The .odp creation emits a relocation against the symbol ".TOC." which
+ // create a R_PPC64_TOC relocation. However the relocation symbol name
+ // in final object creation should be NULL, since the symbol does not
+ // really exist, it is just the reference to TOC base for the current
+ // object file. Since the symbol is undefined, returning false results
+ // in a relocation with a null section which is the desired result.
+ case MCSymbolRefExpr::VK_PPC_TOCBASE:
+ return false;
- const MCSectionELF &Section =
- static_cast<const MCSectionELF&>(ASymbol.getSection());
- const SectionKind secKind = Section.getKind();
+ // These VariantKind cause the relocation to refer to something other than
+ // the symbol itself, like a linker generated table. Since the address of
+ // symbol is not relevant, we cannot replace the symbol with the
+ // section and patch the difference in the addend.
+ case MCSymbolRefExpr::VK_GOT:
+ case MCSymbolRefExpr::VK_PLT:
+ case MCSymbolRefExpr::VK_GOTPCREL:
+ case MCSymbolRefExpr::VK_Mips_GOT:
+ case MCSymbolRefExpr::VK_PPC_GOT_LO:
+ case MCSymbolRefExpr::VK_PPC_GOT_HI:
+ case MCSymbolRefExpr::VK_PPC_GOT_HA:
+ return true;
+ }
- if (secKind.isBSS())
- return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
+ // An undefined symbol is not in any section, so the relocation has to point
+ // to the symbol itself.
+ const MCSymbol &Sym = SD->getSymbol();
+ if (Sym.isUndefined())
+ return true;
- if (secKind.isThreadLocal()) {
- if (Renamed)
- return Renamed;
- return &Symbol;
+ unsigned Binding = MCELF::GetBinding(*SD);
+ switch(Binding) {
+ default:
+ llvm_unreachable("Invalid Binding");
+ case ELF::STB_LOCAL:
+ break;
+ case ELF::STB_WEAK:
+ // If the symbol is weak, it might be overridden by a symbol in another
+ // file. The relocation has to point to the symbol so that the linker
+ // can update it.
+ return true;
+ case ELF::STB_GLOBAL:
+ // Global ELF symbols can be preempted by the dynamic linker. The relocation
+ // has to point to the symbol for a reason analogous to the STB_WEAK case.
+ return true;
}
- MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
- const MCSectionELF &Sec2 =
- static_cast<const MCSectionELF&>(F.getParent()->getSection());
-
- if (&Sec2 != &Section &&
- (Kind == MCSymbolRefExpr::VK_PLT ||
- Kind == MCSymbolRefExpr::VK_GOTPCREL ||
- Kind == MCSymbolRefExpr::VK_GOTOFF)) {
- if (Renamed)
- return Renamed;
- return &Symbol;
- }
+ // If a relocation points to a mergeable section, we have to be careful.
+ // If the offset is zero, a relocation with the section will encode the
+ // same information. With a non-zero offset, the situation is different.
+ // For example, a relocation can point 42 bytes past the end of a string.
+ // If we change such a relocation to use the section, the linker would think
+ // that it pointed to another string and subtracting 42 at runtime will
+ // produce the wrong value.
+ auto &Sec = cast<MCSectionELF>(Sym.getSection());
+ unsigned Flags = Sec.getFlags();
+ if (Flags & ELF::SHF_MERGE) {
+ if (C != 0)
+ return true;
- if (Section.getFlags() & ELF::SHF_MERGE) {
- if (Target.getConstant() == 0)
- return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
- if (Renamed)
- return Renamed;
- return &Symbol;
+ // It looks like gold has a bug (http://sourceware.org/PR16794) and can
+ // only handle section relocations to mergeable sections if using RELA.
+ if (!hasRelocationAddend())
+ return true;
}
- return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
+ // Most TLS relocations use a got, so they need the symbol. Even those that
+ // are just an offset (@tpoff), require a symbol in gold versions before
+ // 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
+ // http://sourceware.org/PR16773.
+ if (Flags & ELF::SHF_TLS)
+ return true;
+
+ // If the symbol is a thumb function the final relocation must set the lowest
+ // bit. With a symbol that is done by just having the symbol have that bit
+ // set, so we would lose the bit if we relocated with the section.
+ // FIXME: We could use the section but add the bit to the relocation value.
+ if (Asm.isThumbFunc(&Sym))
+ return true;
+ if (TargetObjectWriter->needsRelocateWithSymbol(*SD, Type))
+ return true;
+ return false;
}
+static const MCSymbol *getWeakRef(const MCSymbolRefExpr &Ref) {
+ const MCSymbol &Sym = Ref.getSymbol();
+
+ if (Ref.getKind() == MCSymbolRefExpr::VK_WEAKREF)
+ return &Sym;
+
+ if (!Sym.isVariable())
+ return nullptr;
+
+ const MCExpr *Expr = Sym.getVariableValue();
+ const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
+ if (!Inner)
+ return nullptr;
+
+ if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
+ return &Inner->getSymbol();
+ return nullptr;
+}
void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFragment *Fragment,
const MCFixup &Fixup,
MCValue Target,
+ bool &IsPCRel,
uint64_t &FixedValue) {
- int64_t Addend = 0;
- int Index = 0;
- int64_t Value = Target.getConstant();
- const MCSymbol *RelocSymbol = NULL;
-
- bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
- if (!Target.isAbsolute()) {
- const MCSymbol &Symbol = Target.getSymA()->getSymbol();
- const MCSymbol &ASymbol = Symbol.AliasedSymbol();
- RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
-
- if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
- const MCSymbol &SymbolB = RefB->getSymbol();
- MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
- IsPCRel = true;
-
- if (!SDB.getFragment())
- Asm.getContext().FatalError(
- Fixup.getLoc(),
- Twine("symbol '") + SymbolB.getName() +
- "' can not be undefined in a subtraction expression");
-
- // Offset of the symbol in the section
- int64_t a = Layout.getSymbolOffset(&SDB);
-
- // Offset of the relocation in the section
- int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
- Value += b - a;
- }
+ const MCSectionData *FixupSection = Fragment->getParent();
+ uint64_t C = Target.getConstant();
+ uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
+
+ if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
+ assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&
+ "Should not have constructed this");
+
+ // Let A, B and C being the components of Target and R be the location of
+ // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
+ // If it is pcrel, we want to compute (A - B + C - R).
+
+ // In general, ELF has no relocations for -B. It can only represent (A + C)
+ // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
+ // replace B to implement it: (A - R - K + C)
+ if (IsPCRel)
+ Asm.getContext().FatalError(
+ Fixup.getLoc(),
+ "No relocation available to represent this relative expression");
+
+ const MCSymbol &SymB = RefB->getSymbol();
+
+ if (SymB.isUndefined())
+ Asm.getContext().FatalError(
+ Fixup.getLoc(),
+ Twine("symbol '") + SymB.getName() +
+ "' can not be undefined in a subtraction expression");
+
+ assert(!SymB.isAbsolute() && "Should have been folded");
+ const MCSection &SecB = SymB.getSection();
+ if (&SecB != &FixupSection->getSection())
+ Asm.getContext().FatalError(
+ Fixup.getLoc(), "Cannot represent a difference across sections");
+
+ const MCSymbolData &SymBD = Asm.getSymbolData(SymB);
+ uint64_t SymBOffset = Layout.getSymbolOffset(&SymBD);
+ uint64_t K = SymBOffset - FixupOffset;
+ IsPCRel = true;
+ C -= K;
+ }
- if (!RelocSymbol) {
- MCSymbolData &SD = Asm.getSymbolData(ASymbol);
- MCFragment *F = SD.getFragment();
+ // We either rejected the fixup or folded B into C at this point.
+ const MCSymbolRefExpr *RefA = Target.getSymA();
+ const MCSymbol *SymA = RefA ? &RefA->getSymbol() : nullptr;
+ const MCSymbolData *SymAD = SymA ? &Asm.getSymbolData(*SymA) : nullptr;
- if (F) {
- Index = F->getParent()->getOrdinal() + 1;
- // Offset of the symbol in the section
- Value += Layout.getSymbolOffset(&SD);
- } else {
- Index = 0;
- }
- } else {
- if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_WEAKREF)
- WeakrefUsedInReloc.insert(RelocSymbol);
- else
- UsedInReloc.insert(RelocSymbol);
- Index = -1;
- }
- Addend = Value;
- if (hasRelocationAddend())
- Value = 0;
+ unsigned Type = GetRelocType(Target, Fixup, IsPCRel);
+ bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymAD, C, Type);
+ if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
+ C += Layout.getSymbolOffset(SymAD);
+
+ uint64_t Addend = 0;
+ if (hasRelocationAddend()) {
+ Addend = C;
+ C = 0;
}
- FixedValue = Value;
- unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
- (RelocSymbol != 0), Addend);
- MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
- MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
+ FixedValue = C;
+
+ // FIXME: What is this!?!?
+ MCSymbolRefExpr::VariantKind Modifier =
+ RefA ? RefA->getKind() : MCSymbolRefExpr::VK_None;
if (RelocNeedsGOT(Modifier))
NeedsGOT = true;
- uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
- Fixup.getOffset();
+ if (!RelocateWithSymbol) {
+ const MCSection *SecA =
+ (SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr;
+ auto *ELFSec = cast_or_null<MCSectionELF>(SecA);
+ MCSymbol *SectionSymbol =
+ ELFSec ? Asm.getContext().getOrCreateSectionSymbol(*ELFSec)
+ : nullptr;
+ ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend);
+ Relocations[FixupSection].push_back(Rec);
+ return;
+ }
- if (!hasRelocationAddend())
- Addend = 0;
+ if (SymA) {
+ if (const MCSymbol *R = Renames.lookup(SymA))
+ SymA = R;
- if (is64Bit())
- assert(isInt<64>(Addend));
- else
- assert(isInt<32>(Addend));
-
- ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
- Relocations[Fragment->getParent()].push_back(ERE);
+ if (const MCSymbol *WeakRef = getWeakRef(*RefA))
+ WeakrefUsedInReloc.insert(WeakRef);
+ else
+ UsedInReloc.insert(SymA);
+ }
+ ELFRelocationEntry Rec(FixupOffset, SymA, Type, Addend);
+ Relocations[FixupSection].push_back(Rec);
+ return;
}
uint64_t
ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
const MCSymbol *S) {
- MCSymbolData &SD = Asm.getSymbolData(*S);
+ const MCSymbolData &SD = Asm.getSymbolData(*S);
return SD.getIndex();
}
-bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
- const MCSymbolData &Data,
- bool Used, bool Renamed) {
+bool ELFObjectWriter::isInSymtab(const MCAsmLayout &Layout,
+ const MCSymbolData &Data, bool Used,
+ bool Renamed) {
const MCSymbol &Symbol = Data.getSymbol();
if (Symbol.isVariable()) {
const MCExpr *Expr = Symbol.getVariableValue();
if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
return true;
- const MCSymbol &A = Symbol.AliasedSymbol();
- if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
- return false;
+ if (Symbol.isVariable()) {
+ const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
+ if (Base && Base->isUndefined())
+ return false;
+ }
bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
return true;
}
-bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
- bool isUsedInReloc) {
+bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isUsedInReloc) {
if (Data.isExternal())
return false;
const MCSymbol &Symbol = Data.getSymbol();
- const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
-
- if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
- if (isSignature && !isUsedInReloc)
- return true;
+ if (Symbol.isDefined())
+ return true;
+ if (isUsedInReloc)
return false;
- }
return true;
}
void
ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
const SectionIndexMapTy &SectionIndexMap,
- RevGroupMapTy RevGroupMap,
+ const RevGroupMapTy &RevGroupMap,
unsigned NumRegularSections) {
// FIXME: Is this the correct place to do this?
// FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
MCELF::SetBinding(Data, ELF::STB_GLOBAL);
}
- // Index 0 is always the empty string.
- StringMap<uint64_t> StringIndexMap;
- StringTable += '\x00';
-
- // FIXME: We could optimize suffixes in strtab in the same way we
- // optimize them in shstrtab.
-
- for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(),
- ie = Asm.file_names_end();
- it != ie;
- ++it) {
- StringRef Name = *it;
- uint64_t &Entry = StringIndexMap[Name];
- if (!Entry) {
- Entry = StringTable.size();
- StringTable += Name;
- StringTable += '\x00';
- }
- FileSymbolData.push_back(Entry);
- }
-
// Add the data for the symbols.
- for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
- ie = Asm.symbol_end(); it != ie; ++it) {
- const MCSymbol &Symbol = it->getSymbol();
+ for (MCSymbolData &SD : Asm.symbols()) {
+ const MCSymbol &Symbol = SD.getSymbol();
bool Used = UsedInReloc.count(&Symbol);
bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
bool isSignature = RevGroupMap.count(&Symbol);
- if (!isInSymtab(Asm, *it,
+ if (!isInSymtab(Layout, SD,
Used || WeakrefUsed || isSignature,
Renames.count(&Symbol)))
continue;
ELFSymbolData MSD;
- MSD.SymbolData = it;
- const MCSymbol *BaseSymbol = getBaseSymbol(Layout, Symbol);
+ MSD.SymbolData = &SD;
+ const MCSymbol *BaseSymbol = Layout.getBaseSymbol(Symbol);
// Undefined symbols are global, but this is the first place we
// are able to set it.
- bool Local = isLocal(*it, isSignature, Used);
- if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
+ bool Local = isLocal(SD, Used);
+ if (!Local && MCELF::GetBinding(SD) == ELF::STB_LOCAL) {
assert(BaseSymbol);
- MCSymbolData &SD = Asm.getSymbolData(*BaseSymbol);
- MCELF::SetBinding(*it, ELF::STB_GLOBAL);
+ MCSymbolData &BaseData = Asm.getSymbolData(*BaseSymbol);
MCELF::SetBinding(SD, ELF::STB_GLOBAL);
+ MCELF::SetBinding(BaseData, ELF::STB_GLOBAL);
}
if (!BaseSymbol) {
MSD.SectionIndex = ELF::SHN_ABS;
- } else if (it->isCommon()) {
+ } else if (SD.isCommon()) {
assert(!Local);
MSD.SectionIndex = ELF::SHN_COMMON;
} else if (BaseSymbol->isUndefined()) {
if (isSignature && !Used)
- MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
+ MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap.lookup(&Symbol));
else
MSD.SectionIndex = ELF::SHN_UNDEF;
if (!Used && WeakrefUsed)
- MCELF::SetBinding(*it, ELF::STB_WEAK);
+ MCELF::SetBinding(SD, ELF::STB_WEAK);
} else {
const MCSectionELF &Section =
static_cast<const MCSectionELF&>(BaseSymbol->getSection());
// @@ in defined ones.
StringRef Name = Symbol.getName();
SmallString<32> Buf;
-
size_t Pos = Name.find("@@@");
if (Pos != StringRef::npos) {
Buf += Name.substr(0, Pos);
Name = Buf;
}
- uint64_t &Entry = StringIndexMap[Name];
- if (!Entry) {
- Entry = StringTable.size();
- StringTable += Name;
- StringTable += '\x00';
- }
- MSD.StringIndex = Entry;
+ // Sections have their own string table
+ if (MCELF::GetType(SD) != ELF::STT_SECTION)
+ MSD.Name = StrTabBuilder.add(Name);
+
if (MSD.SectionIndex == ELF::SHN_UNDEF)
UndefinedSymbolData.push_back(MSD);
else if (Local)
ExternalSymbolData.push_back(MSD);
}
+ for (auto i = Asm.file_names_begin(), e = Asm.file_names_end(); i != e; ++i)
+ StrTabBuilder.add(*i);
+
+ StrTabBuilder.finalize(StringTableBuilder::ELF);
+
+ for (auto i = Asm.file_names_begin(), e = Asm.file_names_end(); i != e; ++i)
+ FileSymbolData.push_back(StrTabBuilder.getOffset(*i));
+
+ for (ELFSymbolData &MSD : LocalSymbolData)
+ MSD.StringIndex = MCELF::GetType(*MSD.SymbolData) == ELF::STT_SECTION
+ ? 0
+ : StrTabBuilder.getOffset(MSD.Name);
+ for (ELFSymbolData &MSD : ExternalSymbolData)
+ MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name);
+ for (ELFSymbolData& MSD : UndefinedSymbolData)
+ MSD.StringIndex = StrTabBuilder.getOffset(MSD.Name);
+
// Symbols are required to be in lexicographic order.
array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
LocalSymbolData[i].SymbolData->setIndex(Index++);
- Index += NumRegularSections;
-
for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
ExternalSymbolData[i].SymbolData->setIndex(Index++);
for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
}
}
+static SmallVector<char, 128>
+getUncompressedData(MCAsmLayout &Layout,
+ MCSectionData::FragmentListType &Fragments) {
+ SmallVector<char, 128> UncompressedData;
+ for (const MCFragment &F : Fragments) {
+ const SmallVectorImpl<char> *Contents;
+ switch (F.getKind()) {
+ case MCFragment::FT_Data:
+ Contents = &cast<MCDataFragment>(F).getContents();
+ break;
+ case MCFragment::FT_Dwarf:
+ Contents = &cast<MCDwarfLineAddrFragment>(F).getContents();
+ break;
+ case MCFragment::FT_DwarfFrame:
+ Contents = &cast<MCDwarfCallFrameFragment>(F).getContents();
+ break;
+ default:
+ llvm_unreachable(
+ "Not expecting any other fragment types in a debug_* section");
+ }
+ UncompressedData.append(Contents->begin(), Contents->end());
+ }
+ return UncompressedData;
+}
+
+// Include the debug info compression header:
+// "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
+// useful for consumers to preallocate a buffer to decompress into.
+static bool
+prependCompressionHeader(uint64_t Size,
+ SmallVectorImpl<char> &CompressedContents) {
+ static const StringRef Magic = "ZLIB";
+ if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
+ return false;
+ if (sys::IsLittleEndianHost)
+ sys::swapByteOrder(Size);
+ CompressedContents.insert(CompressedContents.begin(),
+ Magic.size() + sizeof(Size), 0);
+ std::copy(Magic.begin(), Magic.end(), CompressedContents.begin());
+ std::copy(reinterpret_cast<char *>(&Size),
+ reinterpret_cast<char *>(&Size + 1),
+ CompressedContents.begin() + Magic.size());
+ return true;
+}
+
+// Return a single fragment containing the compressed contents of the whole
+// section. Null if the section was not compressed for any reason.
+static std::unique_ptr<MCDataFragment>
+getCompressedFragment(MCAsmLayout &Layout,
+ MCSectionData::FragmentListType &Fragments) {
+ std::unique_ptr<MCDataFragment> CompressedFragment(new MCDataFragment());
+
+ // Gather the uncompressed data from all the fragments, recording the
+ // alignment fragment, if seen, and any fixups.
+ SmallVector<char, 128> UncompressedData =
+ getUncompressedData(Layout, Fragments);
+
+ SmallVectorImpl<char> &CompressedContents = CompressedFragment->getContents();
+
+ zlib::Status Success = zlib::compress(
+ StringRef(UncompressedData.data(), UncompressedData.size()),
+ CompressedContents);
+ if (Success != zlib::StatusOK)
+ return nullptr;
+
+ if (!prependCompressionHeader(UncompressedData.size(), CompressedContents))
+ return nullptr;
+
+ return CompressedFragment;
+}
+
+typedef DenseMap<const MCSectionData *, std::vector<MCSymbolData *>>
+DefiningSymbolMap;
+
+static void UpdateSymbols(const MCAsmLayout &Layout,
+ const std::vector<MCSymbolData *> &Symbols,
+ MCFragment &NewFragment) {
+ for (MCSymbolData *Sym : Symbols) {
+ Sym->setOffset(Sym->getOffset() +
+ Layout.getFragmentOffset(Sym->getFragment()));
+ Sym->setFragment(&NewFragment);
+ }
+}
+
+static void CompressDebugSection(MCAssembler &Asm, MCAsmLayout &Layout,
+ const DefiningSymbolMap &DefiningSymbols,
+ const MCSectionELF &Section,
+ MCSectionData &SD) {
+ StringRef SectionName = Section.getSectionName();
+ MCSectionData::FragmentListType &Fragments = SD.getFragmentList();
+
+ std::unique_ptr<MCDataFragment> CompressedFragment =
+ getCompressedFragment(Layout, Fragments);
+
+ // Leave the section as-is if the fragments could not be compressed.
+ if (!CompressedFragment)
+ return;
+
+ // Update the fragment+offsets of any symbols referring to fragments in this
+ // section to refer to the new fragment.
+ auto I = DefiningSymbols.find(&SD);
+ if (I != DefiningSymbols.end())
+ UpdateSymbols(Layout, I->second, *CompressedFragment);
+
+ // Invalidate the layout for the whole section since it will have new and
+ // different fragments now.
+ Layout.invalidateFragmentsFrom(&Fragments.front());
+ Fragments.clear();
+
+ // Complete the initialization of the new fragment
+ CompressedFragment->setParent(&SD);
+ CompressedFragment->setLayoutOrder(0);
+ Fragments.push_back(CompressedFragment.release());
+
+ // Rename from .debug_* to .zdebug_*
+ Asm.getContext().renameELFSection(&Section,
+ (".z" + SectionName.drop_front(1)).str());
+}
+
+void ELFObjectWriter::CompressDebugSections(MCAssembler &Asm,
+ MCAsmLayout &Layout) {
+ if (!Asm.getContext().getAsmInfo()->compressDebugSections())
+ return;
+
+ DefiningSymbolMap DefiningSymbols;
+
+ for (MCSymbolData &SD : Asm.symbols())
+ if (MCFragment *F = SD.getFragment())
+ DefiningSymbols[F->getParent()].push_back(&SD);
+
+ for (MCSectionData &SD : Asm) {
+ const MCSectionELF &Section =
+ static_cast<const MCSectionELF &>(SD.getSection());
+ StringRef SectionName = Section.getSectionName();
+
+ // Compressing debug_frame requires handling alignment fragments which is
+ // more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
+ // for writing to arbitrary buffers) for little benefit.
+ if (!SectionName.startswith(".debug_") || SectionName == ".debug_frame")
+ continue;
+
+ CompressDebugSection(Asm, Layout, DefiningSymbols, Section, SD);
+ }
+}
+
void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
const RelMapTy &RelMap) {
for (MCAssembler::const_iterator it = Asm.begin(),
WriteWord(EntrySize); // sh_entsize
}
+// ELF doesn't require relocations to be in any order. We sort by the r_offset,
+// just to match gnu as for easier comparison. The use type is an arbitrary way
+// of making the sort deterministic.
+static int cmpRel(const ELFRelocationEntry *AP, const ELFRelocationEntry *BP) {
+ const ELFRelocationEntry &A = *AP;
+ const ELFRelocationEntry &B = *BP;
+ if (A.Offset != B.Offset)
+ return B.Offset - A.Offset;
+ if (B.Type != A.Type)
+ return A.Type - B.Type;
+ llvm_unreachable("ELFRelocs might be unstable!");
+}
+
+static void sortRelocs(const MCAssembler &Asm,
+ std::vector<ELFRelocationEntry> &Relocs) {
+ array_pod_sort(Relocs.begin(), Relocs.end(), cmpRel);
+}
+
void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
MCDataFragment *F,
const MCSectionData *SD) {
std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
- // Sort the relocation entries. Most targets just sort by r_offset, but some
- // (e.g., MIPS) have additional constraints.
- TargetObjectWriter->sortRelocs(Asm, Relocs);
+ sortRelocs(Asm, Relocs);
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
- ELFRelocationEntry entry = Relocs[e - i - 1];
+ const ELFRelocationEntry &Entry = Relocs[e - i - 1];
+ unsigned Index =
+ Entry.Symbol ? getSymbolIndexInSymbolTable(Asm, Entry.Symbol) : 0;
- if (!entry.Index)
- ;
- // FIXME: this is most likely a bug if index overflows.
- else if (entry.Index < 0)
- entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
- else
- entry.Index += FileSymbolData.size() + LocalSymbolData.size();
if (is64Bit()) {
- write(*F, entry.r_offset);
+ write(*F, Entry.Offset);
if (TargetObjectWriter->isN64()) {
- write(*F, uint32_t(entry.Index));
+ write(*F, uint32_t(Index));
- write(*F, TargetObjectWriter->getRSsym(entry.Type));
- write(*F, TargetObjectWriter->getRType3(entry.Type));
- write(*F, TargetObjectWriter->getRType2(entry.Type));
- write(*F, TargetObjectWriter->getRType(entry.Type));
- }
- else {
+ write(*F, TargetObjectWriter->getRSsym(Entry.Type));
+ write(*F, TargetObjectWriter->getRType3(Entry.Type));
+ write(*F, TargetObjectWriter->getRType2(Entry.Type));
+ write(*F, TargetObjectWriter->getRType(Entry.Type));
+ } else {
struct ELF::Elf64_Rela ERE64;
- ERE64.setSymbolAndType(entry.Index, entry.Type);
+ ERE64.setSymbolAndType(Index, Entry.Type);
write(*F, ERE64.r_info);
}
if (hasRelocationAddend())
- write(*F, entry.r_addend);
+ write(*F, Entry.Addend);
} else {
- write(*F, uint32_t(entry.r_offset));
+ write(*F, uint32_t(Entry.Offset));
struct ELF::Elf32_Rela ERE32;
- ERE32.setSymbolAndType(entry.Index, entry.Type);
+ ERE32.setSymbolAndType(Index, Entry.Type);
write(*F, ERE32.r_info);
if (hasRelocationAddend())
- write(*F, uint32_t(entry.r_addend));
+ write(*F, uint32_t(Entry.Addend));
}
}
}
-static int compareBySuffix(const MCSectionELF *const *a,
- const MCSectionELF *const *b) {
- const StringRef &NameA = (*a)->getSectionName();
- const StringRef &NameB = (*b)->getSectionName();
- const unsigned sizeA = NameA.size();
- const unsigned sizeB = NameB.size();
- const unsigned len = std::min(sizeA, sizeB);
- for (unsigned int i = 0; i < len; ++i) {
- char ca = NameA[sizeA - i - 1];
- char cb = NameB[sizeB - i - 1];
- if (ca != cb)
- return cb - ca;
- }
-
- return sizeB - sizeA;
-}
-
void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
MCAsmLayout &Layout,
SectionIndexMapTy &SectionIndexMap,
WriteSymbolTable(F, Asm, Layout, SectionIndexMap);
F = new MCDataFragment(&StrtabSD);
- F->getContents().append(StringTable.begin(), StringTable.end());
+ F->getContents().append(StrTabBuilder.data().begin(),
+ StrTabBuilder.data().end());
F = new MCDataFragment(&ShstrtabSD);
- std::vector<const MCSectionELF*> Sections;
- for (MCAssembler::const_iterator it = Asm.begin(),
- ie = Asm.end(); it != ie; ++it) {
+ // Section header string table.
+ for (auto it = Asm.begin(), ie = Asm.end(); it != ie; ++it) {
const MCSectionELF &Section =
static_cast<const MCSectionELF&>(it->getSection());
- Sections.push_back(&Section);
- }
- array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
-
- // Section header string table.
- //
- // The first entry of a string table holds a null character so skip
- // section 0.
- uint64_t Index = 1;
- F->getContents().push_back('\x00');
-
- for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
- const MCSectionELF &Section = *Sections[I];
-
- StringRef Name = Section.getSectionName();
- if (I != 0) {
- StringRef PreviousName = Sections[I - 1]->getSectionName();
- if (PreviousName.endswith(Name)) {
- SectionStringTableIndex[&Section] = Index - Name.size() - 1;
- continue;
- }
- }
- // Remember the index into the string table so we can write it
- // into the sh_name field of the section header table.
- SectionStringTableIndex[&Section] = Index;
-
- Index += Name.size() + 1;
- F->getContents().append(Name.begin(), Name.end());
- F->getContents().push_back('\x00');
+ ShStrTabBuilder.add(Section.getSectionName());
}
+ ShStrTabBuilder.finalize(StringTableBuilder::ELF);
+ F->getContents().append(ShStrTabBuilder.data().begin(),
+ ShStrTabBuilder.data().end());
}
void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
RevGroupMapTy &RevGroupMap,
SectionIndexMapTy &SectionIndexMap,
const RelMapTy &RelMap) {
- // Create the .note.GNU-stack section if needed.
MCContext &Ctx = Asm.getContext();
- if (Asm.getNoExecStack()) {
- const MCSectionELF *GnuStackSection =
- Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
- SectionKind::getReadOnly());
- Asm.getOrCreateSectionData(*GnuStackSection);
- }
// Build the groups
for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
switch(Section.getType()) {
case ELF::SHT_DYNAMIC:
- sh_link = SectionStringTableIndex[&Section];
+ sh_link = ShStrTabBuilder.getOffset(Section.getSectionName());
sh_info = 0;
break;
case ELF::SHT_X86_64_UNWIND:
case ELF::SHT_MIPS_REGINFO:
case ELF::SHT_MIPS_OPTIONS:
+ case ELF::SHT_MIPS_ABIFLAGS:
// Nothing to do.
break;
break;
default:
- assert(0 && "FIXME: sh_type value not supported!");
- break;
+ llvm_unreachable("FIXME: sh_type value not supported!");
}
if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
}
}
- WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
+ WriteSecHdrEntry(ShStrTabBuilder.getOffset(Section.getSectionName()),
+ Section.getType(),
Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
Alignment, Section.getEntrySize());
}
unsigned NumUserSections = Asm.size();
+ CompressDebugSections(Asm, const_cast<MCAsmLayout &>(Layout));
+
DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
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