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For PC relative relocations where symbols are defined in the same section they

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are referenced, ignore the relocation entry and patch the relocatable field with
the computed symbol offset directly


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76414 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bruno Cardoso Lopes
2009-07-20 08:52:02 +00:00
parent 1488670076
commit 0a38dc5fda
5 changed files with 114 additions and 43 deletions
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80
lib/CodeGen/ELFWriter.cpp
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@ -145,7 +145,7 @@ bool ELFWriter::doInitialization(Module &M) {
return false;
}
/// Get jump table section on the section name returned by TAI
// Get jump table section on the section name returned by TAI
ELFSection &ELFWriter::getJumpTableSection() {
unsigned Align = TM.getTargetData()->getPointerABIAlignment();
return getSection(TAI->getJumpTableDataSection(),
@ -153,7 +153,7 @@ ELFSection &ELFWriter::getJumpTableSection() {
ELFSection::SHF_ALLOC, Align);
}
/// Get a constant pool section based on the section name returned by TAI
// Get a constant pool section based on the section name returned by TAI
ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
std::string CstPoolName =
TAI->SelectSectionForMachineConst(CPE.getType())->getName();
@ -163,6 +163,19 @@ ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
CPE.getAlignment());
}
// Return the relocation section of section 'S'. 'RelA' is true
// if the relocation section contains entries with addends.
ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
unsigned SectionHeaderTy = TEW->hasRelocationAddend() ?
ELFSection::SHT_RELA : ELFSection::SHT_REL;
std::string RelSName(".rel");
if (TEW->hasRelocationAddend())
RelSName.append("a");
RelSName.append(S.getName());
return getSection(RelSName, SectionHeaderTy, 0, TEW->getPrefELFAlignment());
}
// getGlobalELFVisibility - Returns the ELF specific visibility type
unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
switch (GV->getVisibility()) {
@ -474,20 +487,32 @@ bool ELFWriter::doFinalization(Module &M) {
return false;
}
// RelocateField - Patch relocatable field with 'Offset' in 'BO'
// using a 'Value' of known 'Size'
void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
int64_t Value, unsigned Size) {
if (Size == 32)
BO.fixWord32(Value, Offset);
else if (Size == 64)
BO.fixWord64(Value, Offset);
else
llvm_unreachable("don't know howto patch relocatable field");
}
/// EmitRelocations - Emit relocations
void ELFWriter::EmitRelocations() {
// True if the target uses the relocation entry to hold the addend,
// otherwise the addend is written directly to the relocatable field.
bool HasRelA = TEW->hasRelocationAddend();
// Create Relocation sections for each section which needs it.
for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
ELFSection &S = *SectionList[i];
// This section does not have relocations
if (!S.hasRelocations()) continue;
// Get the relocation section for section 'S'
bool HasRelA = TEW->hasRelocationAddend();
ELFSection &RelSec = getRelocSection(S.getName(), HasRelA,
TEW->getPrefELFAlignment());
ELFSection &RelSec = getRelocSection(S);
// 'Link' - Section hdr idx of the associated symbol table
// 'Info' - Section hdr idx of the section to which the relocation applies
@ -502,18 +527,15 @@ void ELFWriter::EmitRelocations() {
MRE = Relos.end(); MRI != MRE; ++MRI) {
MachineRelocation &MR = *MRI;
// Holds the relocatable field address as an offset from the
// beginning of the section where it lives
unsigned Offset = MR.getMachineCodeOffset();
// Relocatable field offset from the section start
unsigned RelOffset = MR.getMachineCodeOffset();
// Symbol index in the symbol table
unsigned SymIdx = 0;
// Target specific ELF relocation type
// Target specific relocation field type and size
unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
// Constant addend used to compute the value to be stored
// into the relocatable field
unsigned RelTySize = TEW->getRelocationTySize(RelType);
int64_t Addend = 0;
// There are several machine relocations types, and each one of
@ -533,29 +555,33 @@ void ELFWriter::EmitRelocations() {
} else {
// Get the symbol index for the section symbol
unsigned SectionIdx = MR.getConstantVal();
SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
Addend = (uint64_t)MR.getResultPointer();
// For pc relative relocations where symbols are defined in the same
// section they are referenced, ignore the relocation entry and patch
// the relocatable field with the symbol offset directly.
if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
int64_t Value = TEW->computeRelocation(Addend, RelOffset, RelType);
RelocateField(S, RelOffset, Value, RelTySize);
continue;
}
// Handle Jump Table Index relocation
if ((SectionIdx == getJumpTableSection().SectionIdx) &&
TEW->hasCustomJumpTableIndexRelTy())
TEW->hasCustomJumpTableIndexRelTy()) {
RelType = TEW->getJumpTableIndexRelTy();
SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
Addend = (uint64_t)MR.getResultPointer();
RelTySize = TEW->getRelocationTySize(RelType);
}
}
// The target without addend on the relocation symbol must be
// patched in the relocation place itself to contain the addend
if (!HasRelA) {
if (TEW->getRelocationTySize(RelType) == 32)
S.fixWord32(Addend, Offset);
else if (TEW->getRelocationTySize(RelType) == 64)
S.fixWord64(Addend, Offset);
else
llvm_unreachable("don't know howto patch relocatable field");
}
if (!HasRelA)
RelocateField(S, RelOffset, Addend, RelTySize);
// Get the relocation entry and emit to the relocation section
ELFRelocation Rel(Offset, SymIdx, RelType, HasRelA, Addend);
ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
EmitRelocation(RelSec, Rel, HasRelA);
}
}