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llvm-project/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp

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//===-- X86ELFObjectWriter.cpp - X86 ELF Writer ---------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/X86FixupKinds.h"
#include "MCTargetDesc/X86MCTargetDesc.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>
#include <cstdint>
using namespace llvm;
namespace {
class X86ELFObjectWriter : public MCELFObjectTargetWriter {
public:
X86ELFObjectWriter(bool IsELF64, uint8_t OSABI, uint16_t EMachine);
~X86ELFObjectWriter() override = default;
protected:
unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup, bool IsPCRel) const override;
};
} // end anonymous namespace
X86ELFObjectWriter::X86ELFObjectWriter(bool IsELF64, uint8_t OSABI,
uint16_t EMachine)
: MCELFObjectTargetWriter(IsELF64, OSABI, EMachine,
// Only i386 and IAMCU use Rel instead of RelA.
/*HasRelocationAddend*/
(EMachine != ELF::EM_386) &&
(EMachine != ELF::EM_IAMCU)) {}
enum X86_64RelType { RT64_NONE, RT64_64, RT64_32, RT64_32S, RT64_16, RT64_8 };
static X86_64RelType getType64(MCFixupKind Kind,
MCSymbolRefExpr::VariantKind &Modifier,
bool &IsPCRel) {
switch (unsigned(Kind)) {
default:
llvm_unreachable("Unimplemented");
case FK_NONE:
return RT64_NONE;
case X86::reloc_global_offset_table8:
Modifier = MCSymbolRefExpr::VK_GOT;
IsPCRel = true;
return RT64_64;
case FK_Data_8:
return RT64_64;
case X86::reloc_signed_4byte:
case X86::reloc_signed_4byte_relax:
if (Modifier == MCSymbolRefExpr::VK_None && !IsPCRel)
return RT64_32S;
return RT64_32;
case X86::reloc_global_offset_table:
Modifier = MCSymbolRefExpr::VK_GOT;
IsPCRel = true;
return RT64_32;
case FK_Data_4:
case FK_PCRel_4:
case X86::reloc_riprel_4byte:
case X86::reloc_riprel_4byte_relax:
case X86::reloc_riprel_4byte_relax_rex:
case X86::reloc_riprel_4byte_movq_load:
return RT64_32;
case X86::reloc_branch_4byte_pcrel:
Modifier = MCSymbolRefExpr::VK_PLT;
return RT64_32;
case FK_PCRel_2:
case FK_Data_2:
return RT64_16;
case FK_PCRel_1:
case FK_Data_1:
return RT64_8;
}
}
static void checkIs32(MCContext &Ctx, SMLoc Loc, X86_64RelType Type) {
if (Type != RT64_32)
Ctx.reportError(Loc,
"32 bit reloc applied to a field with a different size");
}
static void checkIs64(MCContext &Ctx, SMLoc Loc, X86_64RelType Type) {
if (Type != RT64_64)
Ctx.reportError(Loc,
"64 bit reloc applied to a field with a different size");
}
static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc,
MCSymbolRefExpr::VariantKind Modifier,
X86_64RelType Type, bool IsPCRel,
MCFixupKind Kind) {
switch (Modifier) {
default:
llvm_unreachable("Unimplemented");
case MCSymbolRefExpr::VK_None:
case MCSymbolRefExpr::VK_X86_ABS8:
switch (Type) {
case RT64_NONE:
if (Modifier == MCSymbolRefExpr::VK_None)
return ELF::R_X86_64_NONE;
llvm_unreachable("Unimplemented");
case RT64_64:
return IsPCRel ? ELF::R_X86_64_PC64 : ELF::R_X86_64_64;
case RT64_32:
return IsPCRel ? ELF::R_X86_64_PC32 : ELF::R_X86_64_32;
case RT64_32S:
return ELF::R_X86_64_32S;
case RT64_16:
return IsPCRel ? ELF::R_X86_64_PC16 : ELF::R_X86_64_16;
case RT64_8:
return IsPCRel ? ELF::R_X86_64_PC8 : ELF::R_X86_64_8;
}
llvm_unreachable("unexpected relocation type!");
case MCSymbolRefExpr::VK_GOT:
switch (Type) {
case RT64_64:
return IsPCRel ? ELF::R_X86_64_GOTPC64 : ELF::R_X86_64_GOT64;
case RT64_32:
return IsPCRel ? ELF::R_X86_64_GOTPC32 : ELF::R_X86_64_GOT32;
case RT64_32S:
case RT64_16:
case RT64_8:
case RT64_NONE:
llvm_unreachable("Unimplemented");
}
llvm_unreachable("unexpected relocation type!");
case MCSymbolRefExpr::VK_GOTOFF:
assert(Type == RT64_64);
assert(!IsPCRel);
return ELF::R_X86_64_GOTOFF64;
case MCSymbolRefExpr::VK_TPOFF:
assert(!IsPCRel);
switch (Type) {
case RT64_64:
return ELF::R_X86_64_TPOFF64;
case RT64_32:
return ELF::R_X86_64_TPOFF32;
case RT64_32S:
case RT64_16:
case RT64_8:
case RT64_NONE:
llvm_unreachable("Unimplemented");
}
llvm_unreachable("unexpected relocation type!");
case MCSymbolRefExpr::VK_DTPOFF:
assert(!IsPCRel);
switch (Type) {
case RT64_64:
return ELF::R_X86_64_DTPOFF64;
case RT64_32:
return ELF::R_X86_64_DTPOFF32;
case RT64_32S:
case RT64_16:
case RT64_8:
case RT64_NONE:
llvm_unreachable("Unimplemented");
}
llvm_unreachable("unexpected relocation type!");
case MCSymbolRefExpr::VK_SIZE:
assert(!IsPCRel);
switch (Type) {
case RT64_64:
return ELF::R_X86_64_SIZE64;
case RT64_32:
return ELF::R_X86_64_SIZE32;
case RT64_32S:
case RT64_16:
case RT64_8:
case RT64_NONE:
llvm_unreachable("Unimplemented");
}
llvm_unreachable("unexpected relocation type!");
case MCSymbolRefExpr::VK_TLSCALL:
return ELF::R_X86_64_TLSDESC_CALL;
case MCSymbolRefExpr::VK_TLSDESC:
return ELF::R_X86_64_GOTPC32_TLSDESC;
case MCSymbolRefExpr::VK_TLSGD:
checkIs32(Ctx, Loc, Type);
return ELF::R_X86_64_TLSGD;
case MCSymbolRefExpr::VK_GOTTPOFF:
checkIs32(Ctx, Loc, Type);
return ELF::R_X86_64_GOTTPOFF;
case MCSymbolRefExpr::VK_TLSLD:
checkIs32(Ctx, Loc, Type);
return ELF::R_X86_64_TLSLD;
case MCSymbolRefExpr::VK_PLT:
checkIs32(Ctx, Loc, Type);
return ELF::R_X86_64_PLT32;
case MCSymbolRefExpr::VK_GOTPCREL:
checkIs32(Ctx, Loc, Type);
// Older versions of ld.bfd/ld.gold/lld
// do not support GOTPCRELX/REX_GOTPCRELX,
// and we want to keep back-compatibility.
if (!Ctx.getAsmInfo()->canRelaxRelocations())
return ELF::R_X86_64_GOTPCREL;
switch (unsigned(Kind)) {
default:
return ELF::R_X86_64_GOTPCREL;
case X86::reloc_riprel_4byte_relax:
return ELF::R_X86_64_GOTPCRELX;
case X86::reloc_riprel_4byte_relax_rex:
case X86::reloc_riprel_4byte_movq_load:
return ELF::R_X86_64_REX_GOTPCRELX;
}
llvm_unreachable("unexpected relocation type!");
case MCSymbolRefExpr::VK_GOTPCREL_NORELAX:
checkIs32(Ctx, Loc, Type);
return ELF::R_X86_64_GOTPCREL;
case MCSymbolRefExpr::VK_X86_PLTOFF:
checkIs64(Ctx, Loc, Type);
return ELF::R_X86_64_PLTOFF64;
}
}
enum X86_32RelType { RT32_NONE, RT32_32, RT32_16, RT32_8 };
static X86_32RelType getType32(X86_64RelType T) {
switch (T) {
case RT64_NONE:
return RT32_NONE;
case RT64_64:
llvm_unreachable("Unimplemented");
case RT64_32:
case RT64_32S:
return RT32_32;
case RT64_16:
return RT32_16;
case RT64_8:
return RT32_8;
}
llvm_unreachable("unexpected relocation type!");
}
static unsigned getRelocType32(MCContext &Ctx,
MCSymbolRefExpr::VariantKind Modifier,
X86_32RelType Type, bool IsPCRel,
MCFixupKind Kind) {
switch (Modifier) {
default:
llvm_unreachable("Unimplemented");
case MCSymbolRefExpr::VK_None:
case MCSymbolRefExpr::VK_X86_ABS8:
switch (Type) {
case RT32_NONE:
if (Modifier == MCSymbolRefExpr::VK_None)
return ELF::R_386_NONE;
llvm_unreachable("Unimplemented");
case RT32_32:
return IsPCRel ? ELF::R_386_PC32 : ELF::R_386_32;
case RT32_16:
return IsPCRel ? ELF::R_386_PC16 : ELF::R_386_16;
case RT32_8:
return IsPCRel ? ELF::R_386_PC8 : ELF::R_386_8;
}
llvm_unreachable("unexpected relocation type!");
case MCSymbolRefExpr::VK_GOT:
assert(Type == RT32_32);
if (IsPCRel)
return ELF::R_386_GOTPC;
// Older versions of ld.bfd/ld.gold/lld do not support R_386_GOT32X and we
// want to maintain compatibility.
if (!Ctx.getAsmInfo()->canRelaxRelocations())
return ELF::R_386_GOT32;
return Kind == MCFixupKind(X86::reloc_signed_4byte_relax)
? ELF::R_386_GOT32X
: ELF::R_386_GOT32;
case MCSymbolRefExpr::VK_GOTOFF:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_GOTOFF;
case MCSymbolRefExpr::VK_TLSCALL:
return ELF::R_386_TLS_DESC_CALL;
case MCSymbolRefExpr::VK_TLSDESC:
return ELF::R_386_TLS_GOTDESC;
case MCSymbolRefExpr::VK_TPOFF:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_LE_32;
case MCSymbolRefExpr::VK_DTPOFF:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_LDO_32;
case MCSymbolRefExpr::VK_TLSGD:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_GD;
case MCSymbolRefExpr::VK_GOTTPOFF:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_IE_32;
case MCSymbolRefExpr::VK_PLT:
assert(Type == RT32_32);
return ELF::R_386_PLT32;
case MCSymbolRefExpr::VK_INDNTPOFF:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_IE;
case MCSymbolRefExpr::VK_NTPOFF:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_LE;
case MCSymbolRefExpr::VK_GOTNTPOFF:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_GOTIE;
case MCSymbolRefExpr::VK_TLSLDM:
assert(Type == RT32_32);
assert(!IsPCRel);
return ELF::R_386_TLS_LDM;
}
}
unsigned X86ELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const {
MCFixupKind Kind = Fixup.getKind();
if (Kind >= FirstLiteralRelocationKind)
return Kind - FirstLiteralRelocationKind;
MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
X86_64RelType Type = getType64(Kind, Modifier, IsPCRel);
if (getEMachine() == ELF::EM_X86_64)
return getRelocType64(Ctx, Fixup.getLoc(), Modifier, Type, IsPCRel, Kind);
assert((getEMachine() == ELF::EM_386 || getEMachine() == ELF::EM_IAMCU) &&
"Unsupported ELF machine type.");
return getRelocType32(Ctx, Modifier, getType32(Type), IsPCRel, Kind);
}
std::unique_ptr<MCObjectTargetWriter>
llvm::createX86ELFObjectWriter(bool IsELF64, uint8_t OSABI, uint16_t EMachine) {
return std::make_unique<X86ELFObjectWriter>(IsELF64, OSABI, EMachine);
}
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