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android13/external/zucchini/disassembler_elf.cc

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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/zucchini/disassembler_elf.h"
#include <stddef.h>
#include <utility>
#include "base/logging.h"
#include "base/numerics/checked_math.h"
#include "base/numerics/safe_conversions.h"
#include "components/zucchini/abs32_utils.h"
#include "components/zucchini/algorithm.h"
#include "components/zucchini/arm_utils.h"
#include "components/zucchini/buffer_source.h"
namespace zucchini {
namespace {
constexpr uint64_t kElfImageBase = 0;
constexpr size_t kSizeBound = 0x7FFF0000;
// Threshold value for heuristics to detect THUMB2 code.
constexpr double kAArch32BitCondAlwaysDensityThreshold = 0.4;
// Bit fields for JudgeSection() return value.
enum SectionJudgement : int {
// Bit: Section does not invalidate ELF, but may or may not be useful.
SECTION_BIT_SAFE = 1 << 0,
// Bit: Section useful for AddressTranslator, to map between offsets and RVAs.
SECTION_BIT_USEFUL_FOR_ADDRESS_TRANSLATOR = 1 << 1,
// Bit: Section useful for |offset_bound|, to estimate ELF size.
SECTION_BIT_USEFUL_FOR_OFFSET_BOUND = 1 << 2,
// Bit: Section potentially useful for pointer extraction.
SECTION_BIT_MAYBE_USEFUL_FOR_POINTERS = 1 << 3,
// The following are verdicts from combining bits, to improve semantics.
// Default value: A section is malformed and invalidates ELF.
SECTION_IS_MALFORMED = 0,
// Section does not invalidate ELF, but is also not used for anything.
SECTION_IS_USELESS = SECTION_BIT_SAFE,
};
// Decides how a section affects ELF parsing, and returns a bit field composed
// from SectionJudgement values.
template <class TRAITS>
int JudgeSection(size_t image_size, const typename TRAITS::Elf_Shdr* section) {
// BufferRegion uses |size_t| this can be 32-bit in some cases. For Elf64
// |sh_addr|, |sh_offset| and |sh_size| are 64-bit this can result in
// overflows in the subsequent validation steps.
if (!base::IsValueInRangeForNumericType<size_t>(section->sh_addr) ||
!base::IsValueInRangeForNumericType<size_t>(section->sh_offset) ||
!base::IsValueInRangeForNumericType<size_t>(section->sh_size)) {
return SECTION_IS_MALFORMED;
}
// Examine RVA range: Reject if numerical overflow may happen.
if (!BufferRegion{static_cast<size_t>(section->sh_addr),
static_cast<size_t>(section->sh_size)}
.FitsIn(kSizeBound))
return SECTION_IS_MALFORMED;
// Examine offset range: If section takes up |image| data then be stricter.
size_t offset_bound =
(section->sh_type == elf::SHT_NOBITS) ? kSizeBound : image_size;
if (!BufferRegion{static_cast<size_t>(section->sh_offset),
static_cast<size_t>(section->sh_size)}
.FitsIn(offset_bound))
return SECTION_IS_MALFORMED;
// Empty sections don't contribute to offset-RVA mapping. For consistency, it
// should also not affect |offset_bounds|.
if (section->sh_size == 0)
return SECTION_IS_USELESS;
// Sections with |sh_addr == 0| are ignored because these tend to duplicates
// (can cause problems for lookup) and uninteresting. For consistency, it
// should also not affect |offset_bounds|.
if (section->sh_addr == 0)
return SECTION_IS_USELESS;
if (section->sh_type == elf::SHT_NOBITS) {
// Special case for .tbss sections: These should be ignored because they may
// have offset-RVA map that don't match other sections.
if (section->sh_flags & elf::SHF_TLS)
return SECTION_IS_USELESS;
// Section is useful for offset-RVA translation, but does not affect
// |offset_bounds| since it can have large virtual size (e.g., .bss).
return SECTION_BIT_SAFE | SECTION_BIT_USEFUL_FOR_ADDRESS_TRANSLATOR;
}
return SECTION_BIT_SAFE | SECTION_BIT_USEFUL_FOR_ADDRESS_TRANSLATOR |
SECTION_BIT_USEFUL_FOR_OFFSET_BOUND |
SECTION_BIT_MAYBE_USEFUL_FOR_POINTERS;
}
// Determines whether |section| is a reloc section.
template <class TRAITS>
bool IsRelocSection(const typename TRAITS::Elf_Shdr& section) {
DCHECK_GT(section.sh_size, 0U);
if (section.sh_type == elf::SHT_REL) {
// Also validate |section.sh_entsize|, which gets used later.
return section.sh_entsize == sizeof(typename TRAITS::Elf_Rel);
}
if (section.sh_type == elf::SHT_RELA)
return section.sh_entsize == sizeof(typename TRAITS::Elf_Rela);
return false;
}
// Determines whether |section| is a section with executable code.
template <class TRAITS>
bool IsExecSection(const typename TRAITS::Elf_Shdr& section) {
DCHECK_GT(section.sh_size, 0U);
return section.sh_type == elf::SHT_PROGBITS &&
(section.sh_flags & elf::SHF_EXECINSTR) != 0;
}
} // namespace
/******** Elf32Traits ********/
// static
constexpr Bitness Elf32Traits::kBitness;
constexpr elf::FileClass Elf32Traits::kIdentificationClass;
/******** Elf32IntelTraits ********/
// static
constexpr ExecutableType Elf32IntelTraits::kExeType;
const char Elf32IntelTraits::kExeTypeString[] = "ELF x86";
constexpr elf::MachineArchitecture Elf32IntelTraits::kMachineValue;
constexpr uint32_t Elf32IntelTraits::kRelType;
/******** ElfAArch32Traits ********/
// static
constexpr ExecutableType ElfAArch32Traits::kExeType;
const char ElfAArch32Traits::kExeTypeString[] = "ELF ARM";
constexpr elf::MachineArchitecture ElfAArch32Traits::kMachineValue;
constexpr uint32_t ElfAArch32Traits::kRelType;
/******** Elf64Traits ********/
// static
constexpr Bitness Elf64Traits::kBitness;
constexpr elf::FileClass Elf64Traits::kIdentificationClass;
/******** Elf64IntelTraits ********/
// static
constexpr ExecutableType Elf64IntelTraits::kExeType;
const char Elf64IntelTraits::kExeTypeString[] = "ELF x64";
constexpr elf::MachineArchitecture Elf64IntelTraits::kMachineValue;
constexpr uint32_t Elf64IntelTraits::kRelType;
/******** ElfAArch64Traits ********/
// static
constexpr ExecutableType ElfAArch64Traits::kExeType;
const char ElfAArch64Traits::kExeTypeString[] = "ELF ARM64";
constexpr elf::MachineArchitecture ElfAArch64Traits::kMachineValue;
constexpr uint32_t ElfAArch64Traits::kRelType;
/******** DisassemblerElf ********/
// static.
template <class TRAITS>
bool DisassemblerElf<TRAITS>::QuickDetect(ConstBufferView image) {
BufferSource source(image);
// Do not consume the bytes for the magic value, as they are part of the
// header.
if (!source.CheckNextBytes({0x7F, 'E', 'L', 'F'}))
return false;
auto* header = source.GetPointer<typename Traits::Elf_Ehdr>();
if (!header)
return false;
if (header->e_ident[elf::EI_CLASS] != Traits::kIdentificationClass)
return false;
if (header->e_ident[elf::EI_DATA] != 1) // Only ELFDATA2LSB is supported.
return false;
if (header->e_type != elf::ET_EXEC && header->e_type != elf::ET_DYN)
return false;
if (header->e_version != 1 || header->e_ident[elf::EI_VERSION] != 1)
return false;
if (header->e_machine != supported_architecture())
return false;
if (header->e_shentsize != sizeof(typename Traits::Elf_Shdr))
return false;
return true;
}
template <class TRAITS>
DisassemblerElf<TRAITS>::~DisassemblerElf() = default;
template <class TRAITS>
ExecutableType DisassemblerElf<TRAITS>::GetExeType() const {
return Traits::kExeType;
}
template <class TRAITS>
std::string DisassemblerElf<TRAITS>::GetExeTypeString() const {
return Traits::kExeTypeString;
}
// |num_equivalence_iterations_| = 2 for reloc -> abs32.
template <class TRAITS>
DisassemblerElf<TRAITS>::DisassemblerElf() : Disassembler(2) {}
template <class TRAITS>
bool DisassemblerElf<TRAITS>::Parse(ConstBufferView image) {
image_ = image;
if (!ParseHeader())
return false;
ParseSections();
return true;
}
template <class TRAITS>
std::unique_ptr<ReferenceReader> DisassemblerElf<TRAITS>::MakeReadRelocs(
offset_t lo,
offset_t hi) {
DCHECK_LE(lo, hi);
DCHECK_LE(hi, image_.size());
if (reloc_section_dims_.empty())
return std::make_unique<EmptyReferenceReader>();
return std::make_unique<RelocReaderElf>(
image_, Traits::kBitness, reloc_section_dims_,
supported_relocation_type(), lo, hi, translator_);
}
template <class TRAITS>
std::unique_ptr<ReferenceWriter> DisassemblerElf<TRAITS>::MakeWriteRelocs(
MutableBufferView image) {
return std::make_unique<RelocWriterElf>(image, Traits::kBitness, translator_);
}
template <class TRAITS>
bool DisassemblerElf<TRAITS>::ParseHeader() {
BufferSource source(image_);
// Ensure any offsets will fit within the |image_|'s bounds.
if (!base::IsValueInRangeForNumericType<offset_t>(image_.size()))
return false;
// Ensures |header_| is valid later on.
if (!QuickDetect(image_))
return false;
header_ = source.GetPointer<typename Traits::Elf_Ehdr>();
sections_count_ = header_->e_shnum;
source = std::move(BufferSource(image_).Skip(header_->e_shoff));
sections_ = source.GetArray<typename Traits::Elf_Shdr>(sections_count_);
if (!sections_)
return false;
offset_t section_table_end =
base::checked_cast<offset_t>(source.begin() - image_.begin());
segments_count_ = header_->e_phnum;
source = std::move(BufferSource(image_).Skip(header_->e_phoff));
segments_ = source.GetArray<typename Traits::Elf_Phdr>(segments_count_);
if (!segments_)
return false;
offset_t segment_table_end =
base::checked_cast<offset_t>(source.begin() - image_.begin());
// Check string section -- even though we've stopped using them.
elf::Elf32_Half string_section_id = header_->e_shstrndx;
if (string_section_id >= sections_count_)
return false;
size_t section_names_size = sections_[string_section_id].sh_size;
if (section_names_size > 0) {
// If nonempty, then last byte of string section must be null.
const char* section_names = nullptr;
source = std::move(
BufferSource(image_).Skip(sections_[string_section_id].sh_offset));
section_names = source.GetArray<char>(section_names_size);
if (!section_names || section_names[section_names_size - 1] != '\0')
return false;
}
// Establish bound on encountered offsets.
offset_t offset_bound = std::max(section_table_end, segment_table_end);
// Visits |segments_| to get estimate on |offset_bound|.
for (const typename Traits::Elf_Phdr* segment = segments_;
segment != segments_ + segments_count_; ++segment) {
// |image_.covers()| is a sufficient check except when size_t is 32 bit and
// parsing ELF64. In such cases a value-in-range check is needed on the
// segment. This fixes crbug/1035603.
offset_t segment_end;
base::CheckedNumeric<offset_t> checked_segment_end = segment->p_offset;
checked_segment_end += segment->p_filesz;
if (!checked_segment_end.AssignIfValid(&segment_end) ||
!image_.covers({static_cast<size_t>(segment->p_offset),
static_cast<size_t>(segment->p_filesz)})) {
return false;
}
offset_bound = std::max(offset_bound, segment_end);
}
// Visit and validate each section; add address translation data to |units|.
std::vector<AddressTranslator::Unit> units;
units.reserve(sections_count_);
section_judgements_.reserve(sections_count_);
for (int i = 0; i < sections_count_; ++i) {
const typename Traits::Elf_Shdr* section = &sections_[i];
int judgement = JudgeSection<Traits>(image_.size(), section);
section_judgements_.push_back(judgement);
if ((judgement & SECTION_BIT_SAFE) == 0)
return false;
uint32_t sh_size = base::checked_cast<uint32_t>(section->sh_size);
offset_t sh_offset = base::checked_cast<offset_t>(section->sh_offset);
rva_t sh_addr = base::checked_cast<rva_t>(section->sh_addr);
if ((judgement & SECTION_BIT_USEFUL_FOR_ADDRESS_TRANSLATOR) != 0) {
// Store mappings between RVA and offset.
units.push_back({sh_offset, sh_size, sh_addr, sh_size});
}
if ((judgement & SECTION_BIT_USEFUL_FOR_OFFSET_BOUND) != 0) {
offset_t section_end = base::checked_cast<offset_t>(sh_offset + sh_size);
offset_bound = std::max(offset_bound, section_end);
}
}
// Initialize |translator_| for offset-RVA translations. Any inconsistency
// (e.g., 2 offsets correspond to the same RVA) would invalidate the ELF file.
if (translator_.Initialize(std::move(units)) != AddressTranslator::kSuccess)
return false;
DCHECK_LE(offset_bound, image_.size());
image_.shrink(offset_bound);
return true;
}
template <class TRAITS>
void DisassemblerElf<TRAITS>::ExtractInterestingSectionHeaders() {
DCHECK(reloc_section_dims_.empty());
DCHECK(exec_headers_.empty());
for (elf::Elf32_Half i = 0; i < sections_count_; ++i) {
const typename Traits::Elf_Shdr* section = sections_ + i;
if ((section_judgements_[i] & SECTION_BIT_MAYBE_USEFUL_FOR_POINTERS) != 0) {
if (IsRelocSection<Traits>(*section))
reloc_section_dims_.emplace_back(*section);
else if (IsExecSection<Traits>(*section))
exec_headers_.push_back(section);
}
}
auto comp = [](const typename Traits::Elf_Shdr* a,
const typename Traits::Elf_Shdr* b) {
return a->sh_offset < b->sh_offset;
};
std::sort(reloc_section_dims_.begin(), reloc_section_dims_.end());
std::sort(exec_headers_.begin(), exec_headers_.end(), comp);
}
template <class TRAITS>
void DisassemblerElf<TRAITS>::GetAbs32FromRelocSections() {
constexpr int kAbs32Width = Traits::kVAWidth;
DCHECK(abs32_locations_.empty());
// Read reloc targets to get preliminary abs32 locations.
std::unique_ptr<ReferenceReader> relocs = MakeReadRelocs(0, offset_t(size()));
for (auto ref = relocs->GetNext(); ref.has_value(); ref = relocs->GetNext())
abs32_locations_.push_back(ref->target);
std::sort(abs32_locations_.begin(), abs32_locations_.end());
// Abs32 references must have targets translatable to offsets. Remove those
// that are unable to do so.
size_t num_untranslatable =
RemoveUntranslatableAbs32(image_, {Traits::kBitness, kElfImageBase},
translator_, &abs32_locations_);
LOG_IF(WARNING, num_untranslatable) << "Removed " << num_untranslatable
<< " untranslatable abs32 references.";
// Abs32 reference bodies must not overlap. If found, simply remove them.
size_t num_overlapping =
RemoveOverlappingAbs32Locations(kAbs32Width, &abs32_locations_);
LOG_IF(WARNING, num_overlapping)
<< "Removed " << num_overlapping
<< " abs32 references with overlapping bodies.";
abs32_locations_.shrink_to_fit();
}
template <class TRAITS>
void DisassemblerElf<TRAITS>::GetRel32FromCodeSections() {
for (const typename Traits::Elf_Shdr* section : exec_headers_)
ParseExecSection(*section);
PostProcessRel32();
}
template <class TRAITS>
void DisassemblerElf<TRAITS>::ParseSections() {
ExtractInterestingSectionHeaders();
GetAbs32FromRelocSections();
GetRel32FromCodeSections();
}
/******** DisassemblerElfIntel ********/
template <class TRAITS>
DisassemblerElfIntel<TRAITS>::DisassemblerElfIntel() = default;
template <class TRAITS>
DisassemblerElfIntel<TRAITS>::~DisassemblerElfIntel() = default;
template <class TRAITS>
std::vector<ReferenceGroup> DisassemblerElfIntel<TRAITS>::MakeReferenceGroups()
const {
return {
{ReferenceTypeTraits{sizeof(TRAITS::Elf_Rel::r_offset), TypeTag(kReloc),
PoolTag(kReloc)},
&DisassemblerElfIntel<TRAITS>::MakeReadRelocs,
&DisassemblerElfIntel<TRAITS>::MakeWriteRelocs},
{ReferenceTypeTraits{Traits::kVAWidth, TypeTag(kAbs32), PoolTag(kAbs32)},
&DisassemblerElfIntel<TRAITS>::MakeReadAbs32,
&DisassemblerElfIntel<TRAITS>::MakeWriteAbs32},
// N.B.: Rel32 |width| is 4 bytes, even for x64.
{ReferenceTypeTraits{4, TypeTag(kRel32), PoolTag(kRel32)},
&DisassemblerElfIntel<TRAITS>::MakeReadRel32,
&DisassemblerElfIntel<TRAITS>::MakeWriteRel32}};
}
template <class TRAITS>
void DisassemblerElfIntel<TRAITS>::ParseExecSection(
const typename TRAITS::Elf_Shdr& section) {
constexpr int kAbs32Width = Traits::kVAWidth;
// |this->| is needed to access protected members of templated base class. To
// reduce noise, use local references for these.
ConstBufferView& image_ = this->image_;
const AddressTranslator& translator_ = this->translator_;
auto& abs32_locations_ = this->abs32_locations_;
// Range of values was ensured in ParseHeader().
rva_t start_rva = base::checked_cast<rva_t>(section.sh_addr);
rva_t end_rva = base::checked_cast<rva_t>(start_rva + section.sh_size);
AddressTranslator::RvaToOffsetCache target_rva_checker(translator_);
ConstBufferView region(image_.begin() + section.sh_offset, section.sh_size);
Abs32GapFinder gap_finder(image_, region, abs32_locations_, kAbs32Width);
typename TRAITS::Rel32FinderUse rel_finder(image_, translator_);
// Iterate over gaps between abs32 references, to avoid collision.
while (gap_finder.FindNext()) {
rel_finder.SetRegion(gap_finder.GetGap());
while (rel_finder.FindNext()) {
auto rel32 = rel_finder.GetRel32();
if (target_rva_checker.IsValid(rel32.target_rva) &&
(rel32.can_point_outside_section ||
(start_rva <= rel32.target_rva && rel32.target_rva < end_rva))) {
rel_finder.Accept();
rel32_locations_.push_back(rel32.location);
}
}
}
}
template <class TRAITS>
void DisassemblerElfIntel<TRAITS>::PostProcessRel32() {
rel32_locations_.shrink_to_fit();
std::sort(rel32_locations_.begin(), rel32_locations_.end());
}
template <class TRAITS>
std::unique_ptr<ReferenceReader> DisassemblerElfIntel<TRAITS>::MakeReadAbs32(
offset_t lo,
offset_t hi) {
// TODO(huangs): Don't use Abs32RvaExtractorWin32 here; use new class that
// caters to different ELF architectures.
Abs32RvaExtractorWin32 abs_rva_extractor(
this->image_, AbsoluteAddress(TRAITS::kBitness, kElfImageBase),
this->abs32_locations_, lo, hi);
return std::make_unique<Abs32ReaderWin32>(std::move(abs_rva_extractor),
this->translator_);
}
template <class TRAITS>
std::unique_ptr<ReferenceWriter> DisassemblerElfIntel<TRAITS>::MakeWriteAbs32(
MutableBufferView image) {
return std::make_unique<Abs32WriterWin32>(
image, AbsoluteAddress(TRAITS::kBitness, kElfImageBase),
this->translator_);
}
template <class TRAITS>
std::unique_ptr<ReferenceReader> DisassemblerElfIntel<TRAITS>::MakeReadRel32(
offset_t lo,
offset_t hi) {
return std::make_unique<Rel32ReaderX86>(this->image_, lo, hi,
&rel32_locations_, this->translator_);
}
template <class TRAITS>
std::unique_ptr<ReferenceWriter> DisassemblerElfIntel<TRAITS>::MakeWriteRel32(
MutableBufferView image) {
return std::make_unique<Rel32WriterX86>(image, this->translator_);
}
// Explicit instantiation for supported classes.
template class DisassemblerElfIntel<Elf32IntelTraits>;
template class DisassemblerElfIntel<Elf64IntelTraits>;
template bool DisassemblerElf<Elf32IntelTraits>::QuickDetect(
ConstBufferView image);
template bool DisassemblerElf<Elf64IntelTraits>::QuickDetect(
ConstBufferView image);
/******** DisassemblerElfArm ********/
template <class Traits>
DisassemblerElfArm<Traits>::DisassemblerElfArm() = default;
template <class Traits>
DisassemblerElfArm<Traits>::~DisassemblerElfArm() = default;
template <class Traits>
bool DisassemblerElfArm<Traits>::IsTargetOffsetInExecSection(
offset_t offset) const {
// Executable sections can appear in large numbers in .o files and in
// pathological cases. Since this function may be called for each reference
// candidate, linear search may be too slow (so use binary search).
return IsTargetOffsetInElfSectionList(this->exec_headers_, offset);
}
template <class Traits>
void DisassemblerElfArm<Traits>::ParseExecSection(
const typename Traits::Elf_Shdr& section) {
ConstBufferView& image_ = this->image_;
const AddressTranslator& translator_ = this->translator_;
auto& abs32_locations_ = this->abs32_locations_;
ConstBufferView region(image_.begin() + section.sh_offset, section.sh_size);
Abs32GapFinder gap_finder(image_, region, abs32_locations_, Traits::kVAWidth);
std::unique_ptr<typename Traits::Rel32FinderUse> rel_finder =
MakeRel32Finder(section);
AddressTranslator::RvaToOffsetCache rva_to_offset(translator_);
while (gap_finder.FindNext()) {
rel_finder->SetRegion(gap_finder.GetGap());
while (rel_finder->FindNext()) {
auto rel32 = rel_finder->GetRel32();
offset_t target_offset = rva_to_offset.Convert(rel32.target_rva);
if (target_offset != kInvalidOffset) {
// For robustness, reject illegal offsets, which can arise from, e.g.,
// misidentify ARM vs. THUMB2 mode, or even misidentifying data as code!
if (IsTargetOffsetInExecSection(target_offset)) {
rel_finder->Accept();
rel32_locations_table_[rel32.type].push_back(rel32.location);
}
}
}
}
}
template <class Traits>
void DisassemblerElfArm<Traits>::PostProcessRel32() {
for (int type = 0; type < AArch32Rel32Translator::NUM_ADDR_TYPE; ++type) {
std::sort(rel32_locations_table_[type].begin(),
rel32_locations_table_[type].end());
rel32_locations_table_[type].shrink_to_fit();
}
}
template <class Traits>
std::unique_ptr<ReferenceReader> DisassemblerElfArm<Traits>::MakeReadAbs32(
offset_t lo,
offset_t hi) {
// TODO(huangs): Reconcile the use of Win32-specific classes in ARM code!
Abs32RvaExtractorWin32 abs_rva_extractor(this->image_,
AbsoluteAddress(Traits::kBitness, 0),
this->abs32_locations_, lo, hi);
return std::make_unique<Abs32ReaderWin32>(std::move(abs_rva_extractor),
this->translator_);
}
template <class Traits>
std::unique_ptr<ReferenceWriter> DisassemblerElfArm<Traits>::MakeWriteAbs32(
MutableBufferView image) {
return std::make_unique<Abs32WriterWin32>(
image, AbsoluteAddress(Traits::kBitness, 0), this->translator_);
}
template <class TRAITS>
template <class ADDR_TRAITS>
std::unique_ptr<ReferenceReader> DisassemblerElfArm<TRAITS>::MakeReadRel32(
offset_t lower,
offset_t upper) {
return std::make_unique<Rel32ReaderArm<ADDR_TRAITS>>(
this->translator_, this->image_,
this->rel32_locations_table_[ADDR_TRAITS::addr_type], lower, upper);
}
template <class TRAITS>
template <class ADDR_TRAITS>
std::unique_ptr<ReferenceWriter> DisassemblerElfArm<TRAITS>::MakeWriteRel32(
MutableBufferView image) {
return std::make_unique<Rel32WriterArm<ADDR_TRAITS>>(this->translator_,
image);
}
/******** DisassemblerElfAArch32 ********/
DisassemblerElfAArch32::DisassemblerElfAArch32() = default;
DisassemblerElfAArch32::~DisassemblerElfAArch32() = default;
std::vector<ReferenceGroup> DisassemblerElfAArch32::MakeReferenceGroups()
const {
return {
{ReferenceTypeTraits{sizeof(Traits::Elf_Rel::r_offset),
TypeTag(AArch32ReferenceType::kReloc),
PoolTag(ArmReferencePool::kPoolReloc)},
&DisassemblerElfAArch32::MakeReadRelocs,
&DisassemblerElfAArch32::MakeWriteRelocs},
{ReferenceTypeTraits{Traits::kVAWidth,
TypeTag(AArch32ReferenceType::kAbs32),
PoolTag(ArmReferencePool::kPoolAbs32)},
&DisassemblerElfAArch32::MakeReadAbs32,
&DisassemblerElfAArch32::MakeWriteAbs32},
{ReferenceTypeTraits{4, TypeTag(AArch32ReferenceType::kRel32_A24),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch32::MakeReadRel32<
AArch32Rel32Translator::AddrTraits_A24>,
&DisassemblerElfAArch32::MakeWriteRel32<
AArch32Rel32Translator::AddrTraits_A24>},
{ReferenceTypeTraits{2, TypeTag(AArch32ReferenceType::kRel32_T8),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch32::MakeReadRel32<
AArch32Rel32Translator::AddrTraits_T8>,
&DisassemblerElfAArch32::MakeWriteRel32<
AArch32Rel32Translator::AddrTraits_T8>},
{ReferenceTypeTraits{2, TypeTag(AArch32ReferenceType::kRel32_T11),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch32::MakeReadRel32<
AArch32Rel32Translator::AddrTraits_T11>,
&DisassemblerElfAArch32::MakeWriteRel32<
AArch32Rel32Translator::AddrTraits_T11>},
{ReferenceTypeTraits{4, TypeTag(AArch32ReferenceType::kRel32_T20),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch32::MakeReadRel32<
AArch32Rel32Translator::AddrTraits_T20>,
&DisassemblerElfAArch32::MakeWriteRel32<
AArch32Rel32Translator::AddrTraits_T20>},
{ReferenceTypeTraits{4, TypeTag(AArch32ReferenceType::kRel32_T24),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch32::MakeReadRel32<
AArch32Rel32Translator::AddrTraits_T24>,
&DisassemblerElfAArch32::MakeWriteRel32<
AArch32Rel32Translator::AddrTraits_T24>},
};
}
std::unique_ptr<DisassemblerElfAArch32::Traits::Rel32FinderUse>
DisassemblerElfAArch32::MakeRel32Finder(
const typename Traits::Elf_Shdr& section) {
return std::make_unique<Rel32FinderAArch32>(image_, translator_,
IsExecSectionThumb2(section));
}
bool DisassemblerElfAArch32::IsExecSectionThumb2(
const typename Traits::Elf_Shdr& section) const {
// ARM mode requires 4-byte alignment.
if (section.sh_addr % 4 != 0 || section.sh_size % 4 != 0)
return true;
const uint8_t* first = image_.begin() + section.sh_offset;
const uint8_t* end = first + section.sh_size;
// Each instruction in 32-bit ARM (little-endian) looks like
// ?? ?? ?? X?,
// where X specifies conditional execution. X = 0xE represents AL = "ALways
// execute", and tends to appear very often. We use this as our main indicator
// to discern 32-bit ARM mode from THUMB2 mode.
size_t num = 0;
size_t den = 0;
for (const uint8_t* cur = first; cur < end; cur += 4) {
// |cur[3]| is within bounds because |end - cur| is a multiple of 4.
uint8_t maybe_cond = cur[3] & 0xF0;
if (maybe_cond == 0xE0)
++num;
++den;
}
if (den > 0) {
LOG(INFO) << "Section scan: " << num << " / " << den << " => "
<< base::StringPrintf("%.2f", num * 100.0 / den) << "%";
}
return num < den * kAArch32BitCondAlwaysDensityThreshold;
}
/******** DisassemblerElfAArch64 ********/
DisassemblerElfAArch64::DisassemblerElfAArch64() = default;
DisassemblerElfAArch64::~DisassemblerElfAArch64() = default;
std::vector<ReferenceGroup> DisassemblerElfAArch64::MakeReferenceGroups()
const {
return {
{ReferenceTypeTraits{sizeof(Traits::Elf_Rel::r_offset),
TypeTag(AArch64ReferenceType::kReloc),
PoolTag(ArmReferencePool::kPoolReloc)},
&DisassemblerElfAArch64::MakeReadRelocs,
&DisassemblerElfAArch64::MakeWriteRelocs},
{ReferenceTypeTraits{Traits::kVAWidth,
TypeTag(AArch64ReferenceType::kAbs32),
PoolTag(ArmReferencePool::kPoolAbs32)},
&DisassemblerElfAArch64::MakeReadAbs32,
&DisassemblerElfAArch64::MakeWriteAbs32},
{ReferenceTypeTraits{4, TypeTag(AArch64ReferenceType::kRel32_Immd14),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch64::MakeReadRel32<
AArch64Rel32Translator::AddrTraits_Immd14>,
&DisassemblerElfAArch64::MakeWriteRel32<
AArch64Rel32Translator::AddrTraits_Immd14>},
{ReferenceTypeTraits{4, TypeTag(AArch64ReferenceType::kRel32_Immd19),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch64::MakeReadRel32<
AArch64Rel32Translator::AddrTraits_Immd19>,
&DisassemblerElfAArch64::MakeWriteRel32<
AArch64Rel32Translator::AddrTraits_Immd19>},
{ReferenceTypeTraits{4, TypeTag(AArch64ReferenceType::kRel32_Immd26),
PoolTag(ArmReferencePool::kPoolRel32)},
&DisassemblerElfAArch64::MakeReadRel32<
AArch64Rel32Translator::AddrTraits_Immd26>,
&DisassemblerElfAArch64::MakeWriteRel32<
AArch64Rel32Translator::AddrTraits_Immd26>},
};
}
std::unique_ptr<DisassemblerElfAArch64::Traits::Rel32FinderUse>
DisassemblerElfAArch64::MakeRel32Finder(
const typename Traits::Elf_Shdr& section) {
return std::make_unique<Rel32FinderAArch64>(image_, translator_);
}
// Explicit instantiation for supported classes.
template class DisassemblerElfArm<ElfAArch32Traits>;
template class DisassemblerElfArm<ElfAArch64Traits>;
template bool DisassemblerElf<ElfAArch32Traits>::QuickDetect(
ConstBufferView image);
template bool DisassemblerElf<ElfAArch64Traits>::QuickDetect(
ConstBufferView image);
} // namespace zucchini
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