[llvm] r219829 - Correctly handle references to section symbols.
Rafael Espindola
rafael.espindola at gmail.com
Wed Oct 15 11:55:31 PDT 2014
Author: rafael
Date: Wed Oct 15 13:55:30 2014
New Revision: 219829
URL: http://llvm.org/viewvc/llvm-project?rev=219829&view=rev
Log:
Correctly handle references to section symbols.
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.
Added:
llvm/trunk/test/MC/ELF/section-sym-err.s
llvm/trunk/test/MC/ELF/section-sym.s
Modified:
llvm/trunk/include/llvm/MC/MCContext.h
llvm/trunk/lib/MC/ELFObjectWriter.cpp
llvm/trunk/lib/MC/MCContext.cpp
llvm/trunk/lib/MC/MCELFStreamer.cpp
llvm/trunk/test/MC/ELF/comdat.s
llvm/trunk/tools/llvm-readobj/ELFDumper.cpp
Modified: llvm/trunk/include/llvm/MC/MCContext.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCContext.h?rev=219829&r1=219828&r2=219829&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCContext.h (original)
+++ llvm/trunk/include/llvm/MC/MCContext.h Wed Oct 15 13:55:30 2014
@@ -73,6 +73,10 @@ namespace llvm {
/// Symbols - Bindings of names to symbols.
SymbolTable Symbols;
+ /// ELF sections can have a corresponding symbol. This maps one to the
+ /// other.
+ DenseMap<const MCSectionELF*, MCSymbol*> SectionSymbols;
+
/// A maping from a local label number and an instance count to a symbol.
/// For example, in the assembly
/// 1:
@@ -231,6 +235,8 @@ namespace llvm {
MCSymbol *GetOrCreateSymbol(StringRef Name);
MCSymbol *GetOrCreateSymbol(const Twine &Name);
+ MCSymbol *getOrCreateSectionSymbol(const MCSectionELF &Section);
+
/// LookupSymbol - Get the symbol for \p Name, or null.
MCSymbol *LookupSymbol(StringRef Name) const;
MCSymbol *LookupSymbol(const Twine &Name) const;
Modified: llvm/trunk/lib/MC/ELFObjectWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/ELFObjectWriter.cpp?rev=219829&r1=219828&r2=219829&view=diff
==============================================================================
--- llvm/trunk/lib/MC/ELFObjectWriter.cpp (original)
+++ llvm/trunk/lib/MC/ELFObjectWriter.cpp Wed Oct 15 13:55:30 2014
@@ -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 MCObjectW
// 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(M
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(c
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(MCAs
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(MCAs
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(MCAs
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::WriteRelocationsFr
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);
Modified: llvm/trunk/lib/MC/MCContext.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCContext.cpp?rev=219829&r1=219828&r2=219829&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCContext.cpp (original)
+++ llvm/trunk/lib/MC/MCContext.cpp Wed Oct 15 13:55:30 2014
@@ -113,6 +113,23 @@ MCSymbol *MCContext::GetOrCreateSymbol(S
return Sym;
}
+MCSymbol *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
+ MCSymbol *&Sym = SectionSymbols[&Section];
+ if (Sym)
+ return Sym;
+
+ StringRef Name = Section.getSectionName();
+ StringMapEntry<bool> *NameEntry = &UsedNames.GetOrCreateValue(Name);
+ NameEntry->setValue(true);
+ Sym = new (*this) MCSymbol(NameEntry->getKey(), /*isTemporary*/ false);
+
+ StringMapEntry<MCSymbol*> &Entry = Symbols.GetOrCreateValue(Name);
+ if (!Entry.getValue())
+ Entry.setValue(Sym);
+
+ return Sym;
+}
+
MCSymbol *MCContext::CreateSymbol(StringRef Name) {
// Determine whether this is an assembler temporary or normal label, if used.
bool isTemporary = false;
Modified: llvm/trunk/lib/MC/MCELFStreamer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCELFStreamer.cpp?rev=219829&r1=219828&r2=219829&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCELFStreamer.cpp (original)
+++ llvm/trunk/lib/MC/MCELFStreamer.cpp Wed Oct 15 13:55:30 2014
@@ -92,10 +92,19 @@ void MCELFStreamer::ChangeSection(const
MCSectionData *CurSection = getCurrentSectionData();
if (CurSection && CurSection->isBundleLocked())
report_fatal_error("Unterminated .bundle_lock when changing a section");
- const MCSymbol *Grp = static_cast<const MCSectionELF *>(Section)->getGroup();
+
+ MCAssembler &Asm = getAssembler();
+ auto *SectionELF = static_cast<const MCSectionELF *>(Section);
+ const MCSymbol *Grp = SectionELF->getGroup();
if (Grp)
- getAssembler().getOrCreateSymbolData(*Grp);
+ Asm.getOrCreateSymbolData(*Grp);
+
this->MCObjectStreamer::ChangeSection(Section, Subsection);
+ MCSymbol *SectionSymbol = getContext().getOrCreateSectionSymbol(*SectionELF);
+ if (SectionSymbol->isUndefined()) {
+ EmitLabel(SectionSymbol);
+ MCELF::SetType(Asm.getSymbolData(*SectionSymbol), ELF::STT_SECTION);
+ }
}
void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
Modified: llvm/trunk/test/MC/ELF/comdat.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/comdat.s?rev=219829&r1=219828&r2=219829&view=diff
==============================================================================
--- llvm/trunk/test/MC/ELF/comdat.s (original)
+++ llvm/trunk/test/MC/ELF/comdat.s Wed Oct 15 13:55:30 2014
@@ -41,7 +41,7 @@
// CHECK-NEXT: Offset: 0x54
// CHECK-NEXT: Size: 12
// CHECK-NEXT: Link: 13
-// CHECK-NEXT: Info: 13
+// CHECK-NEXT: Info: 10
// CHECK-NEXT: AddressAlignment: 4
// CHECK-NEXT: EntrySize: 4
// CHECK-NEXT: }
Added: llvm/trunk/test/MC/ELF/section-sym-err.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/section-sym-err.s?rev=219829&view=auto
==============================================================================
--- llvm/trunk/test/MC/ELF/section-sym-err.s (added)
+++ llvm/trunk/test/MC/ELF/section-sym-err.s Wed Oct 15 13:55:30 2014
@@ -0,0 +1,6 @@
+// RUN: not llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o %t.o 2>&1 | FileCheck %s
+
+.section foo
+foo:
+
+// CHECK: error: invalid symbol redefinition
Added: llvm/trunk/test/MC/ELF/section-sym.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/section-sym.s?rev=219829&view=auto
==============================================================================
--- llvm/trunk/test/MC/ELF/section-sym.s (added)
+++ llvm/trunk/test/MC/ELF/section-sym.s Wed Oct 15 13:55:30 2014
@@ -0,0 +1,91 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -s -t -r --expand-relocs | FileCheck %s
+
+.section foo, "aG", @progbits, f1, comdat
+.section foo, "G", @progbits, f2, comdat
+.section bar
+.long foo
+
+// Test that the relocation points to the first section foo.
+
+// The first seciton foo has index 6
+// CHECK: Section {
+// CHECK: Index: 6
+// CHECK-NEXT: Name: foo (28)
+// CHECK-NEXT: Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT: Flags [ (0x202)
+// CHECK-NEXT: SHF_ALLOC (0x2)
+// CHECK-NEXT: SHF_GROUP (0x200)
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address: 0x0
+// CHECK-NEXT: Offset: 0x50
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Link: 0
+// CHECK-NEXT: Info: 0
+// CHECK-NEXT: AddressAlignment: 1
+// CHECK-NEXT: EntrySize: 0
+// CHECK-NEXT: }
+// CHECK-NEXT: Section {
+// CHECK-NEXT: Index: 7
+// CHECK-NEXT: Name: foo (28)
+// CHECK-NEXT: Type: SHT_PROGBITS (0x1)
+// CHECK-NEXT: Flags [ (0x200)
+// CHECK-NEXT: SHF_GROUP (0x200)
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address: 0x0
+// CHECK-NEXT: Offset: 0x50
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Link: 0
+// CHECK-NEXT: Info: 0
+// CHECK-NEXT: AddressAlignment: 1
+// CHECK-NEXT: EntrySize: 0
+// CHECK-NEXT: }
+
+// The relocation points to symbol 6
+// CHECK: Relocations [
+// CHECK-NEXT: Section (9) .relabar {
+// CHECK-NEXT: Relocation {
+// CHECK-NEXT: Offset: 0x0
+// CHECK-NEXT: Type: R_X86_64_32 (10)
+// CHECK-NEXT: Symbol: foo (6)
+// CHECK-NEXT: Addend: 0x0
+// CHECK-NEXT: }
+// CHECK-NEXT: }
+// CHECK-NEXT: ]
+
+
+// The symbol 6 corresponds section 6
+// CHECK: Symbols [
+
+// symbol 0
+// CHECK-NOT: Name
+// CHECK: Name:
+
+// symbol 1
+// CHECK-NOT: Name
+// CHECK: Name: f1
+
+// symbol 2
+// CHECK-NOT: Name
+// CHECK: Name: f2
+
+// symbol 3
+// CHECK-NOT: Name
+// CHECK: Name: .text
+
+// symbol 4
+// CHECK-NOT: Name
+// CHECK: Name: .data
+
+// symbol 5
+// CHECK-NOT: Name
+// CHECK: Name: .bss
+
+// symbol 6
+// CHECK-NOT: Name
+// CHECK: Name: foo
+// CHECK: Section: foo (0x6)
+
+// symbol 7
+// CHECK-NOT: Name
+// CHECK: Name: foo
+// CHECK: Section: foo (0x7)
Modified: llvm/trunk/tools/llvm-readobj/ELFDumper.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-readobj/ELFDumper.cpp?rev=219829&r1=219828&r2=219829&view=diff
==============================================================================
--- llvm/trunk/tools/llvm-readobj/ELFDumper.cpp (original)
+++ llvm/trunk/tools/llvm-readobj/ELFDumper.cpp Wed Oct 15 13:55:30 2014
@@ -676,7 +676,8 @@ void ELFDumper<ELFT>::printRelocation(co
DictScope Group(W, "Relocation");
W.printHex("Offset", Rel.r_offset);
W.printNumber("Type", RelocName, (int)Rel.getType(Obj->isMips64EL()));
- W.printString("Symbol", SymbolName.size() > 0 ? SymbolName : "-");
+ W.printNumber("Symbol", SymbolName.size() > 0 ? SymbolName : "-",
+ Rel.getSymbol(Obj->isMips64EL()));
W.printHex("Addend", Rel.r_addend);
} else {
raw_ostream& OS = W.startLine();
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