[llvm] r264649 - Handle section vs global name conflict.
Evgeniy Stepanov via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 28 13:36:29 PDT 2016
Author: eugenis
Date: Mon Mar 28 15:36:28 2016
New Revision: 264649
URL: http://llvm.org/viewvc/llvm-project?rev=264649&view=rev
Log:
Handle section vs global name conflict.
This is a fix for PR26941.
When there is both a section and a global definition with the same
name, the global wins.
Section symbols are not added to the symbol table; section references
are left undefined and fixed up in the object writer unless they've
been satisfied by some other definition.
Added:
llvm/trunk/test/MC/ELF/section-sym-redefine.s
Removed:
llvm/trunk/test/MC/ELF/section-sym-err.s
Modified:
llvm/trunk/include/llvm/MC/MCContext.h
llvm/trunk/lib/MC/ELFObjectWriter.cpp
llvm/trunk/lib/MC/MCContext.cpp
Modified: llvm/trunk/include/llvm/MC/MCContext.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCContext.h?rev=264649&r1=264648&r2=264649&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCContext.h (original)
+++ llvm/trunk/include/llvm/MC/MCContext.h Mon Mar 28 15:36:28 2016
@@ -96,7 +96,9 @@ namespace llvm {
DenseMap<std::pair<unsigned, unsigned>, MCSymbol *> LocalSymbols;
/// Keeps tracks of names that were used both for used declared and
- /// artificial symbols.
+ /// artificial symbols. The value is "true" if the name has been used for a
+ /// non-section symbol (there can be at most one of those, plus an unlimited
+ /// number of section symbols with the same name).
StringMap<bool, BumpPtrAllocator &> UsedNames;
/// The next ID to dole out to an unnamed assembler temporary symbol with
Modified: llvm/trunk/lib/MC/ELFObjectWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/ELFObjectWriter.cpp?rev=264649&r1=264648&r2=264649&view=diff
==============================================================================
--- llvm/trunk/lib/MC/ELFObjectWriter.cpp (original)
+++ llvm/trunk/lib/MC/ELFObjectWriter.cpp Mon Mar 28 15:36:28 2016
@@ -375,9 +375,24 @@ uint64_t ELFObjectWriter::SymbolValue(co
void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
const MCAsmLayout &Layout) {
+ // Section symbols are used as definitions for undefined symbols with matching
+ // names. If there are multiple sections with the same name, the first one is
+ // used.
+ for (const MCSection &Sec : Asm) {
+ const MCSymbol *Begin = Sec.getBeginSymbol();
+ if (!Begin)
+ continue;
+
+ const MCSymbol *Alias = Asm.getContext().lookupSymbol(Begin->getName());
+ if (!Alias || !Alias->isUndefined())
+ continue;
+
+ Renames.insert(
+ std::make_pair(cast<MCSymbolELF>(Alias), cast<MCSymbolELF>(Begin)));
+ }
+
// The presence of symbol versions causes undefined symbols and
// versions declared with @@@ to be renamed.
-
for (const MCSymbol &A : Asm.symbols()) {
const auto &Alias = cast<MCSymbolELF>(A);
// Not an alias.
Modified: llvm/trunk/lib/MC/MCContext.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCContext.cpp?rev=264649&r1=264648&r2=264649&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCContext.cpp (original)
+++ llvm/trunk/lib/MC/MCContext.cpp Mon Mar 28 15:36:28 2016
@@ -124,19 +124,9 @@ MCSymbolELF *MCContext::getOrCreateSecti
return Sym;
StringRef Name = Section.getSectionName();
-
- MCSymbol *&OldSym = Symbols[Name];
- if (OldSym && OldSym->isUndefined()) {
- Sym = cast<MCSymbolELF>(OldSym);
- return Sym;
- }
-
- auto NameIter = UsedNames.insert(std::make_pair(Name, true)).first;
+ auto NameIter = UsedNames.insert(std::make_pair(Name, false)).first;
Sym = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
- if (!OldSym)
- OldSym = Sym;
-
return Sym;
}
@@ -192,9 +182,12 @@ MCSymbol *MCContext::createSymbol(String
raw_svector_ostream(NewName) << NextUniqueID++;
}
auto NameEntry = UsedNames.insert(std::make_pair(NewName, true));
- if (NameEntry.second) {
- // Ok, we found a name. Have the MCSymbol object itself refer to the copy
- // of the string that is embedded in the UsedNames entry.
+ if (NameEntry.second || !NameEntry.first->second) {
+ // Ok, we found a name.
+ // Mark it as used for a non-section symbol.
+ NameEntry.first->second = true;
+ // Have the MCSymbol object itself refer to the copy of the string that is
+ // embedded in the UsedNames entry.
return createSymbolImpl(&*NameEntry.first, IsTemporary);
}
assert(IsTemporary && "Cannot rename non-temporary symbols");
Removed: 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=264648&view=auto
==============================================================================
--- llvm/trunk/test/MC/ELF/section-sym-err.s (original)
+++ llvm/trunk/test/MC/ELF/section-sym-err.s (removed)
@@ -1,6 +0,0 @@
-// 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-redefine.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/section-sym-redefine.s?rev=264649&view=auto
==============================================================================
--- llvm/trunk/test/MC/ELF/section-sym-redefine.s (added)
+++ llvm/trunk/test/MC/ELF/section-sym-redefine.s Mon Mar 28 15:36:28 2016
@@ -0,0 +1,138 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -t -r --expand-relocs | FileCheck %s
+
+// Local symbol overriding section.
+.section x1,"a", at progbits
+.local x1
+.comm x1,4,4
+.long x1 // reloc: .bss + 0
+
+// Section declared after local. Local symbol wins.
+.local x2
+.comm x2,4,4
+.section x2,"a", at progbits
+.long x2 // reloc: .bss + 4
+
+// No overriding symbol.
+.section x3,"a", at progbits
+.long x3 // reloc: x3(section) + 0
+
+// Global vs section.
+.section x4,"a", at progbits
+.long 0
+.globl x4
+.section foo, "a", @progbits
+x4:
+.long 0
+.long x4 // reloc: x4(global) + 0
+
+// Global vs implicit section
+.globl .data
+.data:
+.long 42
+.long .data // reloc: .data(global) + 0
+
+// CHECK: Relocations [
+// CHECK: Section (4) .relax1 {
+// CHECK: Relocation {
+// CHECK: Offset: 0x0
+// CHECK: Type: R_X86_64_32 (10)
+// CHECK: Symbol: .bss (3)
+// CHECK: Addend: 0x0
+// CHECK: }
+// CHECK: }
+// CHECK: Section (7) .relax2 {
+// CHECK: Relocation {
+// CHECK: Offset: 0x0
+// CHECK: Type: R_X86_64_32 (10)
+// CHECK: Symbol: .bss (3)
+// CHECK: Addend: 0x4
+// CHECK: }
+// CHECK: }
+// CHECK: Section (9) .relax3 {
+// CHECK: Relocation {
+// CHECK: Offset: 0x0
+// CHECK: Type: R_X86_64_32 (10)
+// CHECK: Symbol: x3 (4)
+// CHECK: Addend: 0x0
+// CHECK: }
+// CHECK: }
+// CHECK: Section (12) .relafoo {
+// CHECK: Relocation {
+// CHECK: Offset: 0x4
+// CHECK: Type: R_X86_64_32 (10)
+// CHECK: Symbol: x4 (6)
+// CHECK: Addend: 0x0
+// CHECK: }
+// CHECK: Relocation {
+// CHECK: Offset: 0xC
+// CHECK: Type: R_X86_64_32 (10)
+// CHECK: Symbol: .data (5)
+// CHECK: Addend: 0x0
+// CHECK: }
+// CHECK: }
+// CHECK: ]
+// CHECK: Symbols [
+// CHECK: Symbol {
+// CHECK: Name: (0)
+// CHECK: Value: 0x0
+// CHECK: Size: 0
+// CHECK: Binding: Local (0x0)
+// CHECK: Type: None (0x0)
+// CHECK: Other: 0
+// CHECK: Section: Undefined (0x0)
+// CHECK: }
+// CHECK: Symbol {
+// CHECK: Name: x1 (67)
+// CHECK: Value: 0x0
+// CHECK: Size: 4
+// CHECK: Binding: Local (0x0)
+// CHECK: Type: Object (0x1)
+// CHECK: Other: 0
+// CHECK: Section: .bss (0x5)
+// CHECK: }
+// CHECK: Symbol {
+// CHECK: Name: x2 (59)
+// CHECK: Value: 0x4
+// CHECK: Size: 4
+// CHECK: Binding: Local (0x0)
+// CHECK: Type: Object (0x1)
+// CHECK: Other: 0
+// CHECK: Section: .bss (0x5)
+// CHECK: }
+// CHECK: Symbol {
+// CHECK: Name: (0)
+// CHECK: Value: 0x0
+// CHECK: Size: 0
+// CHECK: Binding: Local (0x0)
+// CHECK: Type: Section (0x3)
+// CHECK: Other: 0
+// CHECK: Section: .bss (0x5)
+// CHECK: }
+// CHECK: Symbol {
+// CHECK: Name: (0)
+// CHECK: Value: 0x0
+// CHECK: Size: 0
+// CHECK: Binding: Local (0x0)
+// CHECK: Type: Section (0x3)
+// CHECK: Other: 0
+// CHECK: Section: x3 (0x8)
+// CHECK: }
+// CHECK: Symbol {
+// CHECK: Name: .data (37)
+// CHECK: Value: 0x8
+// CHECK: Size: 0
+// CHECK: Binding: Global (0x1)
+// CHECK: Type: None (0x0)
+// CHECK: Other: 0
+// CHECK: Section: foo (0xB)
+// CHECK: }
+// CHECK: Symbol {
+// CHECK: Name: x4 (43)
+// CHECK: Value: 0x0
+// CHECK: Size: 0
+// CHECK: Binding: Global (0x1)
+// CHECK: Type: None (0x0)
+// CHECK: Other: 0
+// CHECK: Section: foo (0xB)
+// CHECK: }
+// CHECK: ]
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