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llvm-mirror/lib/Object/ELFObjectFile.cpp
Chandler Carruth ae65e281f3 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00

396 lines
11 KiB
C++

//===- 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;
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;
std::error_code EC = getBuildAttributes(Attributes);
if (EC)
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;
std::error_code EC = getBuildAttributes(Attributes);
if (EC)
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 {};
StringRef PltContents;
if (Plt->getContents(PltContents))
return {};
ArrayRef<uint8_t> PltBytes((const uint8_t *)PltContents.data(),
Plt->getSize());
auto PltEntries = MIA->findPltEntries(Plt->getAddress(), PltBytes,
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;
}