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Correctly handle references to section symbols.

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When processing assembly like

.long .text

we were creating a new undefined symbol .text. GAS on the other hand would
handle that as a reference to the .text section.

This patch implements that by creating the section symbols earlier so that
they are visible during asm parsing.

The patch also updates llvm-readobj to print the symbol number in the relocation
dump so that the test can differentiate between two sections with the same name.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219829 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola
2014-10-15 18:55:30 +00:00
parent 1338612c55
commit ad04f5db82
8 changed files with 160 additions and 52 deletions
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74
lib/MC/ELFObjectWriter.cpp
View File

@ -81,23 +81,13 @@ public:
struct ELFRelocationEntry {
uint64_t Offset; // Where is the relocation.
bool UseSymbol; // Relocate with a symbol, not the section.
union {
const MCSymbol *Symbol; // The symbol to relocate with.
const MCSectionData *Section; // The section to relocate with.
};
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), UseSymbol(true), Symbol(Symbol), Type(Type),
Addend(Addend) {}
ELFRelocationEntry(uint64_t Offset, const MCSectionData *Section,
unsigned Type, uint64_t Addend)
: Offset(Offset), UseSymbol(false), Section(Section), Type(Type),
Addend(Addend) {}
: Offset(Offset), Symbol(Symbol), Type(Type), Addend(Addend) {}
};
class ELFObjectWriter : public MCObjectWriter {
@ -137,6 +127,14 @@ class ELFObjectWriter : public MCObjectWriter {
// Support lexicographic sorting.
bool operator<(const ELFSymbolData &RHS) const {
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;
}
};
@ -651,22 +649,6 @@ void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
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;
@ -882,8 +864,11 @@ void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
if (!RelocateWithSymbol) {
const MCSection *SecA =
(SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr;
const MCSectionData *SecAD = SecA ? &Asm.getSectionData(*SecA) : nullptr;
ELFRelocationEntry Rec(FixupOffset, SecAD, Type, Addend);
auto *ELFSec = cast_or_null<MCSectionELF>(SecA);
MCSymbol *SectionSymbol =
ELFSec ? Asm.getContext().GetOrCreateSymbol(ELFSec->getSectionName())
: nullptr;
ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend);
Relocations[FixupSection].push_back(Rec);
return;
}
@ -1061,7 +1046,10 @@ ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
Buf += Name.substr(Pos + Skip);
Name = Buf;
}
MSD.Name = StrTabBuilder.add(Name);
// 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);
@ -1079,9 +1067,11 @@ ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
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 = StrTabBuilder.getOffset(MSD.Name);
for (ELFSymbolData& MSD : ExternalSymbolData)
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);
@ -1097,8 +1087,6 @@ ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
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)
@ -1354,18 +1342,8 @@ void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
const ELFRelocationEntry &Entry = Relocs[e - i - 1];
unsigned Index;
if (Entry.UseSymbol) {
Index = getSymbolIndexInSymbolTable(Asm, Entry.Symbol);
} else {
const MCSectionData *Sec = Entry.Section;
if (Sec)
Index = Sec->getOrdinal() + FileSymbolData.size() +
LocalSymbolData.size() + 1;
else
Index = 0;
}
unsigned Index =
Entry.Symbol ? getSymbolIndexInSymbolTable(Asm, Entry.Symbol) : 0;
if (is64Bit()) {
write(*F, Entry.Offset);