[llvm] r203962 - Correctly handle an ELF symbol defined with "a = b + expr".
Rafael Espindola
rafael.espindola at gmail.com
Fri Mar 14 13:09:05 PDT 2014
Author: rafael
Date: Fri Mar 14 15:09:04 2014
New Revision: 203962
URL: http://llvm.org/viewvc/llvm-project?rev=203962&view=rev
Log:
Correctly handle an ELF symbol defined with "a = b + expr".
We were marking the symbol as absolute instead of computing b's offset + the
expression value.
This fixes pr19126.
Added:
llvm/trunk/test/MC/ELF/offset.s
Modified:
llvm/trunk/include/llvm/MC/MCSymbol.h
llvm/trunk/lib/MC/ELFObjectWriter.cpp
llvm/trunk/lib/MC/MCSymbol.cpp
Modified: llvm/trunk/include/llvm/MC/MCSymbol.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCSymbol.h?rev=203962&r1=203961&r2=203962&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCSymbol.h (original)
+++ llvm/trunk/include/llvm/MC/MCSymbol.h Fri Mar 14 15:09:04 2014
@@ -18,6 +18,7 @@
#include "llvm/Support/Compiler.h"
namespace llvm {
+ class MCAsmLayout;
class MCExpr;
class MCSection;
class MCContext;
@@ -145,6 +146,11 @@ namespace llvm {
// itself.
const MCSymbol &AliasedSymbol() const;
+ // If this symbol is not a variable, return itself. If it is a variable,
+ // evaluate it and check if it is of the form Base + ConstantOffset. If so,
+ // return Base, if not, return nullptr.
+ const MCSymbol *getBaseSymbol(const MCAsmLayout &Layout) const;
+
void setVariableValue(const MCExpr *Value);
/// @}
Modified: llvm/trunk/lib/MC/ELFObjectWriter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/ELFObjectWriter.cpp?rev=203962&r1=203961&r2=203962&view=diff
==============================================================================
--- llvm/trunk/lib/MC/ELFObjectWriter.cpp (original)
+++ llvm/trunk/lib/MC/ELFObjectWriter.cpp Fri Mar 14 15:09:04 2014
@@ -271,6 +271,7 @@ class ELFObjectWriter : public MCObjectW
/// \param RevGroupMap - Maps a signature symbol to the group section.
/// \param NumRegularSections - Number of non-relocation sections.
void ComputeSymbolTable(MCAssembler &Asm,
+ const MCAsmLayout &Layout,
const SectionIndexMapTy &SectionIndexMap,
RevGroupMapTy RevGroupMap,
unsigned NumRegularSections);
@@ -462,33 +463,43 @@ void ELFObjectWriter::WriteSymbolEntry(M
}
}
-uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
+uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &OrigData,
const MCAsmLayout &Layout) {
- if (Data.isCommon() && Data.isExternal())
- return Data.getCommonAlignment();
-
- const MCSymbol &Symbol = Data.getSymbol();
+ MCSymbolData *Data = &OrigData;
+ if (Data->isCommon() && Data->isExternal())
+ return Data->getCommonAlignment();
+
+ const MCSymbol *Symbol = &Data->getSymbol();
+
+ uint64_t Res = 0;
+ if (Symbol->isVariable()) {
+ const MCExpr *Expr = Symbol->getVariableValue();
+ MCValue Value;
+ if (!Expr->EvaluateAsRelocatable(Value, &Layout))
+ return 0;
+ if (Value.getSymB())
+ return 0;
+ Res = Value.getConstant();
+
+ const MCSymbolRefExpr *A = Value.getSymA();
+ if (!A)
+ return Res;
- if (Symbol.isAbsolute() && Symbol.isVariable()) {
- if (const MCExpr *Value = Symbol.getVariableValue()) {
- int64_t IntValue;
- if (Value->EvaluateAsAbsolute(IntValue, Layout))
- return (uint64_t)IntValue;
- }
+ Symbol = &A->getSymbol();
+ Data = &Layout.getAssembler().getSymbolData(*Symbol);
}
- if (!Symbol.isInSection())
+ if (!Symbol->isInSection())
return 0;
+ if (!Data->getFragment())
+ return 0;
- if (Data.getFragment()) {
- if (Data.getFlags() & ELF_Other_ThumbFunc)
- return Layout.getSymbolOffset(&Data)+1;
- else
- return Layout.getSymbolOffset(&Data);
- }
+ Res += Layout.getSymbolOffset(Data);
+ if (Data->getFlags() & ELF_Other_ThumbFunc)
+ ++Res;
- return 0;
+ return Res;
}
void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
@@ -586,7 +597,7 @@ void ELFObjectWriter::WriteSymbol(MCData
uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift);
Other |= Visibility;
- uint64_t Value = SymbolValue(Data, Layout);
+ uint64_t Value = SymbolValue(OrigData, Layout);
uint64_t Size = 0;
assert(!(Data.isCommon() && !Data.isExternal()));
@@ -897,10 +908,11 @@ void ELFObjectWriter::ComputeIndexMap(MC
}
}
-void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
- const SectionIndexMapTy &SectionIndexMap,
- RevGroupMapTy RevGroupMap,
- unsigned NumRegularSections) {
+void
+ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
+ const SectionIndexMapTy &SectionIndexMap,
+ RevGroupMapTy RevGroupMap,
+ unsigned NumRegularSections) {
// FIXME: Is this the correct place to do this?
// FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
if (NeedsGOT) {
@@ -948,33 +960,33 @@ void ELFObjectWriter::ComputeSymbolTable
ELFSymbolData MSD;
MSD.SymbolData = it;
- const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
+ const MCSymbol *BaseSymbol = Symbol.getBaseSymbol(Layout);
// 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) {
- MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
+ assert(BaseSymbol);
+ MCSymbolData &SD = Asm.getSymbolData(*BaseSymbol);
MCELF::SetBinding(*it, ELF::STB_GLOBAL);
MCELF::SetBinding(SD, ELF::STB_GLOBAL);
}
- if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
- MCELF::SetBinding(*it, ELF::STB_WEAK);
-
- if (it->isCommon()) {
+ if (!BaseSymbol) {
+ MSD.SectionIndex = ELF::SHN_ABS;
+ } else if (it->isCommon()) {
assert(!Local);
MSD.SectionIndex = ELF::SHN_COMMON;
- } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
- MSD.SectionIndex = ELF::SHN_ABS;
- } else if (RefSymbol.isUndefined()) {
+ } else if (BaseSymbol->isUndefined()) {
if (isSignature && !Used)
MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
else
MSD.SectionIndex = ELF::SHN_UNDEF;
+ if (!Used && WeakrefUsed)
+ MCELF::SetBinding(*it, ELF::STB_WEAK);
} else {
const MCSectionELF &Section =
- static_cast<const MCSectionELF&>(RefSymbol.getSection());
+ static_cast<const MCSectionELF&>(BaseSymbol->getSection());
MSD.SectionIndex = SectionIndexMap.lookup(&Section);
if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
NeedsSymtabShndx = true;
@@ -1560,8 +1572,8 @@ void ELFObjectWriter::WriteObject(MCAsse
unsigned NumRegularSections = NumUserSections + NumIndexedSections;
// Compute symbol table information.
- ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections);
-
+ ComputeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
+ NumRegularSections);
WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
Modified: llvm/trunk/lib/MC/MCSymbol.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCSymbol.cpp?rev=203962&r1=203961&r2=203962&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCSymbol.cpp (original)
+++ llvm/trunk/lib/MC/MCSymbol.cpp Fri Mar 14 15:09:04 2014
@@ -9,6 +9,7 @@
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCValue.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
@@ -51,6 +52,22 @@ const MCSymbol &MCSymbol::AliasedSymbol(
return *S;
}
+const MCSymbol *MCSymbol::getBaseSymbol(const MCAsmLayout &Layout) const {
+ if (!isVariable())
+ return this;
+
+ const MCExpr *Expr = getVariableValue();
+ MCValue Value;
+ if (!Expr->EvaluateAsRelocatable(Value, &Layout))
+ return nullptr;
+
+ if (Value.getSymB())
+ return nullptr;
+ if (const MCSymbolRefExpr *A = Value.getSymA())
+ return &A->getSymbol();
+ return nullptr;
+}
+
void MCSymbol::setVariableValue(const MCExpr *Value) {
assert(!IsUsed && "Cannot set a variable that has already been used.");
assert(Value && "Invalid variable value!");
Added: llvm/trunk/test/MC/ELF/offset.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/ELF/offset.s?rev=203962&view=auto
==============================================================================
--- llvm/trunk/test/MC/ELF/offset.s (added)
+++ llvm/trunk/test/MC/ELF/offset.s Fri Mar 14 15:09:04 2014
@@ -0,0 +1,58 @@
+// RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -t - | FileCheck %s
+
+// Test that a variable declared with "var = other_var + cst" is in the same
+// section as other_var and its value is the value of other_var + cst.
+
+ .data
+ .globl sym_a
+ .byte 42
+sym_a:
+
+// CHECK: Symbol {
+// CHECK: Name: sym_a
+// CHECK-NEXT: Value: 0x1
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Binding: Global
+// CHECK-NEXT: Type: None
+// CHECK-NEXT: Other: 0
+// CHECK-NEXT: Section: .data
+// CHECK-NEXT: }
+
+ .long 42
+ .globl sym_b
+sym_b:
+ .globl sym_c
+sym_c = sym_a
+// CHECK: Symbol {
+// CHECK: Name: sym_c
+// CHECK-NEXT: Value: 0x1
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Binding: Global
+// CHECK-NEXT: Type: None
+// CHECK-NEXT: Other: 0
+// CHECK-NEXT: Section: .data
+// CHECK-NEXT: }
+
+ .globl sym_d
+sym_d = sym_a + 1
+// CHECK: Symbol {
+// CHECK: Name: sym_d
+// CHECK-NEXT: Value: 0x2
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Binding: Global
+// CHECK-NEXT: Type: None
+// CHECK-NEXT: Other: 0
+// CHECK-NEXT: Section: .data
+// CHECK-NEXT: }
+
+ .globl sym_e
+sym_e = sym_a + (sym_b - sym_a) * 3
+// CHECK: Symbol {
+// CHECK: Name: sym_e
+// CHECK-NEXT: Value: 0xD
+// CHECK-NEXT: Size: 0
+// CHECK-NEXT: Binding: Global
+// CHECK-NEXT: Type: None
+// CHECK-NEXT: Other: 0
+// CHECK-NEXT: Section: .data
+// CHECK-NEXT: }
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