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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 = §ions_[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);
- }
- template <class TRAITS>
- template <class ADDR_TRAITS>
- std::unique_ptr<ReferenceMixer> DisassemblerElfArm<TRAITS>::MakeMixRel32(
- ConstBufferView src_image,
- ConstBufferView dst_image) {
- return std::make_unique<Rel32MixerArm<ADDR_TRAITS>>(src_image, dst_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>,
- &DisassemblerElfAArch32::MakeMixRel32<
- AArch32Rel32Translator::AddrTraits_A24>},
- {ReferenceTypeTraits{2, TypeTag(AArch32ReferenceType::kRel32_T8),
- PoolTag(ArmReferencePool::kPoolRel32)},
- &DisassemblerElfAArch32::MakeReadRel32<
- AArch32Rel32Translator::AddrTraits_T8>,
- &DisassemblerElfAArch32::MakeWriteRel32<
- AArch32Rel32Translator::AddrTraits_T8>,
- &DisassemblerElfAArch32::MakeMixRel32<
- AArch32Rel32Translator::AddrTraits_T8>},
- {ReferenceTypeTraits{2, TypeTag(AArch32ReferenceType::kRel32_T11),
- PoolTag(ArmReferencePool::kPoolRel32)},
- &DisassemblerElfAArch32::MakeReadRel32<
- AArch32Rel32Translator::AddrTraits_T11>,
- &DisassemblerElfAArch32::MakeWriteRel32<
- AArch32Rel32Translator::AddrTraits_T11>,
- &DisassemblerElfAArch32::MakeMixRel32<
- AArch32Rel32Translator::AddrTraits_T11>},
- {ReferenceTypeTraits{4, TypeTag(AArch32ReferenceType::kRel32_T20),
- PoolTag(ArmReferencePool::kPoolRel32)},
- &DisassemblerElfAArch32::MakeReadRel32<
- AArch32Rel32Translator::AddrTraits_T20>,
- &DisassemblerElfAArch32::MakeWriteRel32<
- AArch32Rel32Translator::AddrTraits_T20>,
- &DisassemblerElfAArch32::MakeMixRel32<
- AArch32Rel32Translator::AddrTraits_T20>},
- {ReferenceTypeTraits{4, TypeTag(AArch32ReferenceType::kRel32_T24),
- PoolTag(ArmReferencePool::kPoolRel32)},
- &DisassemblerElfAArch32::MakeReadRel32<
- AArch32Rel32Translator::AddrTraits_T24>,
- &DisassemblerElfAArch32::MakeWriteRel32<
- AArch32Rel32Translator::AddrTraits_T24>,
- &DisassemblerElfAArch32::MakeMixRel32<
- 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>,
- &DisassemblerElfAArch32::MakeMixRel32<
- AArch64Rel32Translator::AddrTraits_Immd14>},
- {ReferenceTypeTraits{4, TypeTag(AArch64ReferenceType::kRel32_Immd19),
- PoolTag(ArmReferencePool::kPoolRel32)},
- &DisassemblerElfAArch64::MakeReadRel32<
- AArch64Rel32Translator::AddrTraits_Immd19>,
- &DisassemblerElfAArch64::MakeWriteRel32<
- AArch64Rel32Translator::AddrTraits_Immd19>,
- &DisassemblerElfAArch32::MakeMixRel32<
- AArch64Rel32Translator::AddrTraits_Immd19>},
- {ReferenceTypeTraits{4, TypeTag(AArch64ReferenceType::kRel32_Immd26),
- PoolTag(ArmReferencePool::kPoolRel32)},
- &DisassemblerElfAArch64::MakeReadRel32<
- AArch64Rel32Translator::AddrTraits_Immd26>,
- &DisassemblerElfAArch64::MakeWriteRel32<
- AArch64Rel32Translator::AddrTraits_Immd26>,
- &DisassemblerElfAArch32::MakeMixRel32<
- 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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