aboutsummaryrefslogtreecommitdiff
path: root/lib/MC/ELFObjectWriter.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'lib/MC/ELFObjectWriter.cpp')
-rw-r--r--lib/MC/ELFObjectWriter.cpp127
1 files changed, 107 insertions, 20 deletions
diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index 23c6d4c1e4..ce227f00c2 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -25,6 +25,8 @@
#include "llvm/Support/ELF.h"
#include "llvm/Target/TargetAsmBackend.h"
#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/ADT/Statistic.h"
#include "../Target/X86/X86FixupKinds.h"
#include "../Target/ARM/ARMFixupKinds.h"
@@ -32,6 +34,16 @@
#include <vector>
using namespace llvm;
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "reloc-info"
+
+// Emulate the wierd behavior of GNU-as for relocation types
+namespace llvm {
+cl::opt<bool>
+ForceARMElfPIC("arm-elf-force-pic", cl::Hidden, cl::init(false),
+ cl::desc("Force ELF emitter to emit PIC style relocations"));
+}
+
bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
const MCFixupKindInfo &FKI =
Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
@@ -319,7 +331,9 @@ void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
const MCValue &Target,
- const MCFragment &F) const {
+ const MCFragment &F,
+ const MCFixup &Fixup,
+ bool IsPCRel) const {
const MCSymbol &Symbol = Target.getSymA()->getSymbol();
const MCSymbol &ASymbol = Symbol.AliasedSymbol();
const MCSymbol *Renamed = Renames.lookup(&Symbol);
@@ -342,7 +356,7 @@ const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
const SectionKind secKind = Section.getKind();
if (secKind.isBSS())
- return ExplicitRelSym(Asm, Target, F, true);
+ return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
if (secKind.isThreadLocal()) {
if (Renamed)
@@ -365,13 +379,14 @@ const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
if (Section.getFlags() & ELF::SHF_MERGE) {
if (Target.getConstant() == 0)
- return NULL;
+ return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
if (Renamed)
return Renamed;
return &Symbol;
}
- return ExplicitRelSym(Asm, Target, F, false);
+ return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
+
}
@@ -390,7 +405,7 @@ void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
if (!Target.isAbsolute()) {
const MCSymbol &Symbol = Target.getSymA()->getSymbol();
const MCSymbol &ASymbol = Symbol.AliasedSymbol();
- RelocSymbol = SymbolToReloc(Asm, Target, *Fragment);
+ RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
const MCSymbol &SymbolB = RefB->getSymbol();
@@ -1261,32 +1276,93 @@ void ARMELFObjectWriter::WriteEFlags() {
// In ARM, _MergedGlobals and other most symbols get emitted directly.
// I.e. not as an offset to a section symbol.
-// This code is a first-cut approximation of what ARM/gcc does.
+// This code is an approximation of what ARM/gcc does.
+
+STATISTIC(PCRelCount, "Total number of PIC Relocations");
+STATISTIC(NonPCRelCount, "Total number of non-PIC relocations");
const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
const MCValue &Target,
const MCFragment &F,
- bool IsBSS) const {
+ const MCFixup &Fixup,
+ bool IsPCRel) const {
const MCSymbol &Symbol = Target.getSymA()->getSymbol();
bool EmitThisSym = false;
- if (IsBSS) {
- EmitThisSym = StringSwitch<bool>(Symbol.getName())
- .Case("_MergedGlobals", true)
- .Default(false);
+ const MCSectionELF &Section =
+ static_cast<const MCSectionELF&>(Symbol.getSection());
+ const SectionKind secKind = Section.getKind();
+ const MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
+ MCSymbolRefExpr::VariantKind Kind2;
+ Kind2 = Target.getSymB() ? Target.getSymB()->getKind() :
+ MCSymbolRefExpr::VK_None;
+ bool InNormalSection = true;
+ unsigned RelocType = 0;
+ RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel);
+
+ DEBUG(dbgs() << "considering symbol "
+ << Section.getSectionName() << "/"
+ << Symbol.getName() << "/"
+ << " Rel:" << (unsigned)RelocType
+ << " Kind: " << (int)Kind << "/" << (int)Kind2
+ << " Tmp:"
+ << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/"
+ << Symbol.isVariable() << "/" << Symbol.isTemporary()
+ << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n");
+
+ if (IsPCRel || ForceARMElfPIC) { ++PCRelCount;
+ switch (RelocType) {
+ default:
+ // Most relocation types are emitted as explicit symbols
+ InNormalSection =
+ StringSwitch<bool>(Section.getSectionName())
+ .Case(".data.rel.ro.local", false)
+ .Case(".data.rel", false)
+ .Case(".bss", false)
+ .Default(true);
+ EmitThisSym = true;
+ break;
+ case ELF::R_ARM_ABS32:
+ // But things get strange with R_ARM_ABS32
+ // In this case, most things that go in .rodata show up
+ // as section relative relocations
+ InNormalSection =
+ StringSwitch<bool>(Section.getSectionName())
+ .Case(".data.rel.ro.local", false)
+ .Case(".data.rel", false)
+ .Case(".rodata", false)
+ .Case(".bss", false)
+ .Default(true);
+ EmitThisSym = false;
+ break;
+ }
} else {
- EmitThisSym = StringSwitch<bool>(Symbol.getName())
- .Case("_MergedGlobals", true)
- .StartsWith(".L.str", true)
- .Default(false);
+ NonPCRelCount++;
+ InNormalSection =
+ StringSwitch<bool>(Section.getSectionName())
+ .Case(".data.rel.ro.local", false)
+ .Case(".rodata", false)
+ .Case(".data.rel", false)
+ .Case(".bss", false)
+ .Default(true);
+
+ switch (RelocType) {
+ default: EmitThisSym = true; break;
+ case ELF::R_ARM_ABS32: EmitThisSym = false; break;
+ }
}
+
if (EmitThisSym)
return &Symbol;
- if (! Symbol.isTemporary())
+ if (! Symbol.isTemporary() && InNormalSection) {
return &Symbol;
+ }
return NULL;
}
+// Need to examine the Fixup when determining whether to
+// emit the relocation as an explicit symbol or as a section relative
+// offset
unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel,
@@ -1295,6 +1371,20 @@ unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
+ unsigned Type = GetRelocTypeInner(Target, Fixup, IsPCRel);
+
+ if (RelocNeedsGOT(Modifier))
+ NeedsGOT = true;
+
+ return Type;
+}
+
+unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
+ const MCFixup &Fixup,
+ bool IsPCRel) const {
+ MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
+ MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
+
unsigned Type = 0;
if (IsPCRel) {
switch ((unsigned)Fixup.getKind()) {
@@ -1303,7 +1393,7 @@ unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
switch (Modifier) {
default: llvm_unreachable("Unsupported Modifier");
case MCSymbolRefExpr::VK_None:
- Type = ELF::R_ARM_BASE_PREL;
+ Type = ELF::R_ARM_REL32;
break;
case MCSymbolRefExpr::VK_ARM_TLSGD:
assert(0 && "unimplemented");
@@ -1399,9 +1489,6 @@ unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
}
}
- if (RelocNeedsGOT(Modifier))
- NeedsGOT = true;
-
return Type;
}
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2025-04-26 02:49:28 +0000