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 computed symbol offset directly
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76414 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/ELFWriter.cpp b/lib/CodeGen/ELFWriter.cpp
index 527adb8..f04efd5 100644
--- a/lib/CodeGen/ELFWriter.cpp
+++ b/lib/CodeGen/ELFWriter.cpp
@@ -145,7 +145,7 @@
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::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 @@
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 @@
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 @@
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 @@
} 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);
}
}