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llvm-project/llvm/lib/Object/ELFObjectFile.cpp

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//===- ELFObjectFile.cpp - ELF object file implementation -----------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Part of the ELFObjectFile class implementation.
//
//===----------------------------------------------------------------------===//
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/ADT/Triple.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/MC/MCInstrAnalysis.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Object/ELF.h"
#include "llvm/Object/ELFTypes.h"
#include "llvm/Object/Error.h"
#include "llvm/Support/ARMAttributeParser.h"
#include "llvm/Support/ARMBuildAttributes.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/TargetRegistry.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <memory>
#include <string>
#include <system_error>
#include <utility>
using namespace llvm;
using namespace object;
const EnumEntry<unsigned> llvm::object::ElfSymbolTypes[NumElfSymbolTypes] = {
{"None", "NOTYPE", ELF::STT_NOTYPE},
{"Object", "OBJECT", ELF::STT_OBJECT},
{"Function", "FUNC", ELF::STT_FUNC},
{"Section", "SECTION", ELF::STT_SECTION},
{"File", "FILE", ELF::STT_FILE},
{"Common", "COMMON", ELF::STT_COMMON},
{"TLS", "TLS", ELF::STT_TLS},
{"GNU_IFunc", "IFUNC", ELF::STT_GNU_IFUNC}};
ELFObjectFileBase::ELFObjectFileBase(unsigned int Type, MemoryBufferRef Source)
: ObjectFile(Type, Source) {}
template <class ELFT>
static Expected<std::unique_ptr<ELFObjectFile<ELFT>>>
createPtr(MemoryBufferRef Object) {
auto Ret = ELFObjectFile<ELFT>::create(Object);
if (Error E = Ret.takeError())
return std::move(E);
return make_unique<ELFObjectFile<ELFT>>(std::move(*Ret));
}
Expected<std::unique_ptr<ObjectFile>>
ObjectFile::createELFObjectFile(MemoryBufferRef Obj) {
std::pair<unsigned char, unsigned char> Ident =
getElfArchType(Obj.getBuffer());
std::size_t MaxAlignment =
1ULL << countTrailingZeros(uintptr_t(Obj.getBufferStart()));
if (MaxAlignment < 2)
return createError("Insufficient alignment");
if (Ident.first == ELF::ELFCLASS32) {
if (Ident.second == ELF::ELFDATA2LSB)
return createPtr<ELF32LE>(Obj);
else if (Ident.second == ELF::ELFDATA2MSB)
return createPtr<ELF32BE>(Obj);
else
return createError("Invalid ELF data");
} else if (Ident.first == ELF::ELFCLASS64) {
if (Ident.second == ELF::ELFDATA2LSB)
return createPtr<ELF64LE>(Obj);
else if (Ident.second == ELF::ELFDATA2MSB)
return createPtr<ELF64BE>(Obj);
else
return createError("Invalid ELF data");
}
return createError("Invalid ELF class");
}
SubtargetFeatures ELFObjectFileBase::getMIPSFeatures() const {
SubtargetFeatures Features;
unsigned PlatformFlags = getPlatformFlags();
switch (PlatformFlags & ELF::EF_MIPS_ARCH) {
case ELF::EF_MIPS_ARCH_1:
break;
case ELF::EF_MIPS_ARCH_2:
Features.AddFeature("mips2");
break;
case ELF::EF_MIPS_ARCH_3:
Features.AddFeature("mips3");
break;
case ELF::EF_MIPS_ARCH_4:
Features.AddFeature("mips4");
break;
case ELF::EF_MIPS_ARCH_5:
Features.AddFeature("mips5");
break;
case ELF::EF_MIPS_ARCH_32:
Features.AddFeature("mips32");
break;
case ELF::EF_MIPS_ARCH_64:
Features.AddFeature("mips64");
break;
case ELF::EF_MIPS_ARCH_32R2:
Features.AddFeature("mips32r2");
break;
case ELF::EF_MIPS_ARCH_64R2:
Features.AddFeature("mips64r2");
break;
case ELF::EF_MIPS_ARCH_32R6:
Features.AddFeature("mips32r6");
break;
case ELF::EF_MIPS_ARCH_64R6:
Features.AddFeature("mips64r6");
break;
default:
llvm_unreachable("Unknown EF_MIPS_ARCH value");
}
switch (PlatformFlags & ELF::EF_MIPS_MACH) {
case ELF::EF_MIPS_MACH_NONE:
// No feature associated with this value.
break;
case ELF::EF_MIPS_MACH_OCTEON:
Features.AddFeature("cnmips");
break;
default:
llvm_unreachable("Unknown EF_MIPS_ARCH value");
}
if (PlatformFlags & ELF::EF_MIPS_ARCH_ASE_M16)
Features.AddFeature("mips16");
if (PlatformFlags & ELF::EF_MIPS_MICROMIPS)
Features.AddFeature("micromips");
return Features;
}
SubtargetFeatures ELFObjectFileBase::getARMFeatures() const {
SubtargetFeatures Features;
ARMAttributeParser Attributes;
if (Error E = getBuildAttributes(Attributes))
return SubtargetFeatures();
// both ARMv7-M and R have to support thumb hardware div
bool isV7 = false;
if (Attributes.hasAttribute(ARMBuildAttrs::CPU_arch))
isV7 = Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch)
== ARMBuildAttrs::v7;
if (Attributes.hasAttribute(ARMBuildAttrs::CPU_arch_profile)) {
switch(Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch_profile)) {
case ARMBuildAttrs::ApplicationProfile:
Features.AddFeature("aclass");
break;
case ARMBuildAttrs::RealTimeProfile:
Features.AddFeature("rclass");
if (isV7)
Features.AddFeature("hwdiv");
break;
case ARMBuildAttrs::MicroControllerProfile:
Features.AddFeature("mclass");
if (isV7)
Features.AddFeature("hwdiv");
break;
}
}
if (Attributes.hasAttribute(ARMBuildAttrs::THUMB_ISA_use)) {
switch(Attributes.getAttributeValue(ARMBuildAttrs::THUMB_ISA_use)) {
default:
break;
case ARMBuildAttrs::Not_Allowed:
Features.AddFeature("thumb", false);
Features.AddFeature("thumb2", false);
break;
case ARMBuildAttrs::AllowThumb32:
Features.AddFeature("thumb2");
break;
}
}
if (Attributes.hasAttribute(ARMBuildAttrs::FP_arch)) {
switch(Attributes.getAttributeValue(ARMBuildAttrs::FP_arch)) {
default:
break;
case ARMBuildAttrs::Not_Allowed:
Features.AddFeature("vfp2", false);
Features.AddFeature("vfp3", false);
Features.AddFeature("vfp4", false);
break;
case ARMBuildAttrs::AllowFPv2:
Features.AddFeature("vfp2");
break;
case ARMBuildAttrs::AllowFPv3A:
case ARMBuildAttrs::AllowFPv3B:
Features.AddFeature("vfp3");
break;
case ARMBuildAttrs::AllowFPv4A:
case ARMBuildAttrs::AllowFPv4B:
Features.AddFeature("vfp4");
break;
}
}
if (Attributes.hasAttribute(ARMBuildAttrs::Advanced_SIMD_arch)) {
switch(Attributes.getAttributeValue(ARMBuildAttrs::Advanced_SIMD_arch)) {
default:
break;
case ARMBuildAttrs::Not_Allowed:
Features.AddFeature("neon", false);
Features.AddFeature("fp16", false);
break;
case ARMBuildAttrs::AllowNeon:
Features.AddFeature("neon");
break;
case ARMBuildAttrs::AllowNeon2:
Features.AddFeature("neon");
Features.AddFeature("fp16");
break;
}
}
if (Attributes.hasAttribute(ARMBuildAttrs::DIV_use)) {
switch(Attributes.getAttributeValue(ARMBuildAttrs::DIV_use)) {
default:
break;
case ARMBuildAttrs::DisallowDIV:
Features.AddFeature("hwdiv", false);
Features.AddFeature("hwdiv-arm", false);
break;
case ARMBuildAttrs::AllowDIVExt:
Features.AddFeature("hwdiv");
Features.AddFeature("hwdiv-arm");
break;
}
}
return Features;
}
SubtargetFeatures ELFObjectFileBase::getRISCVFeatures() const {
SubtargetFeatures Features;
unsigned PlatformFlags = getPlatformFlags();
if (PlatformFlags & ELF::EF_RISCV_RVC) {
Features.AddFeature("c");
}
return Features;
}
SubtargetFeatures ELFObjectFileBase::getFeatures() const {
switch (getEMachine()) {
case ELF::EM_MIPS:
return getMIPSFeatures();
case ELF::EM_ARM:
return getARMFeatures();
case ELF::EM_RISCV:
return getRISCVFeatures();
default:
return SubtargetFeatures();
}
}
// FIXME Encode from a tablegen description or target parser.
void ELFObjectFileBase::setARMSubArch(Triple &TheTriple) const {
if (TheTriple.getSubArch() != Triple::NoSubArch)
return;
ARMAttributeParser Attributes;
if (Error E = getBuildAttributes(Attributes))
return;
std::string Triple;
// Default to ARM, but use the triple if it's been set.
if (TheTriple.isThumb())
Triple = "thumb";
else
Triple = "arm";
if (Attributes.hasAttribute(ARMBuildAttrs::CPU_arch)) {
switch(Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch)) {
case ARMBuildAttrs::v4:
Triple += "v4";
break;
case ARMBuildAttrs::v4T:
Triple += "v4t";
break;
case ARMBuildAttrs::v5T:
Triple += "v5t";
break;
case ARMBuildAttrs::v5TE:
Triple += "v5te";
break;
case ARMBuildAttrs::v5TEJ:
Triple += "v5tej";
break;
case ARMBuildAttrs::v6:
Triple += "v6";
break;
case ARMBuildAttrs::v6KZ:
Triple += "v6kz";
break;
case ARMBuildAttrs::v6T2:
Triple += "v6t2";
break;
case ARMBuildAttrs::v6K:
Triple += "v6k";
break;
case ARMBuildAttrs::v7:
Triple += "v7";
break;
case ARMBuildAttrs::v6_M:
Triple += "v6m";
break;
case ARMBuildAttrs::v6S_M:
Triple += "v6sm";
break;
case ARMBuildAttrs::v7E_M:
Triple += "v7em";
break;
}
}
if (!isLittleEndian())
Triple += "eb";
TheTriple.setArchName(Triple);
}
std::vector<std::pair<DataRefImpl, uint64_t>>
ELFObjectFileBase::getPltAddresses() const {
std::string Err;
const auto Triple = makeTriple();
const auto *T = TargetRegistry::lookupTarget(Triple.str(), Err);
if (!T)
return {};
uint64_t JumpSlotReloc = 0;
switch (Triple.getArch()) {
case Triple::x86:
JumpSlotReloc = ELF::R_386_JUMP_SLOT;
break;
case Triple::x86_64:
JumpSlotReloc = ELF::R_X86_64_JUMP_SLOT;
break;
case Triple::aarch64:
JumpSlotReloc = ELF::R_AARCH64_JUMP_SLOT;
break;
default:
return {};
}
std::unique_ptr<const MCInstrInfo> MII(T->createMCInstrInfo());
std::unique_ptr<const MCInstrAnalysis> MIA(
T->createMCInstrAnalysis(MII.get()));
if (!MIA)
return {};
Optional<SectionRef> Plt = None, RelaPlt = None, GotPlt = None;
for (const SectionRef &Section : sections()) {
StringRef Name;
if (Section.getName(Name))
continue;
if (Name == ".plt")
Plt = Section;
else if (Name == ".rela.plt" || Name == ".rel.plt")
RelaPlt = Section;
else if (Name == ".got.plt")
GotPlt = Section;
}
if (!Plt || !RelaPlt || !GotPlt)
return {};
Expected<StringRef> PltContents = Plt->getContents();
if (!PltContents) {
consumeError(PltContents.takeError());
return {};
}
auto PltEntries = MIA->findPltEntries(Plt->getAddress(),
arrayRefFromStringRef(*PltContents),
GotPlt->getAddress(), Triple);
// Build a map from GOT entry virtual address to PLT entry virtual address.
DenseMap<uint64_t, uint64_t> GotToPlt;
for (const auto &Entry : PltEntries)
GotToPlt.insert(std::make_pair(Entry.second, Entry.first));
// Find the relocations in the dynamic relocation table that point to
// locations in the GOT for which we know the corresponding PLT entry.
std::vector<std::pair<DataRefImpl, uint64_t>> Result;
for (const auto &Relocation : RelaPlt->relocations()) {
if (Relocation.getType() != JumpSlotReloc)
continue;
auto PltEntryIter = GotToPlt.find(Relocation.getOffset());
if (PltEntryIter != GotToPlt.end())
Result.push_back(std::make_pair(
Relocation.getSymbol()->getRawDataRefImpl(), PltEntryIter->second));
}
return Result;
}
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