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* Copyright (C) 2012 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <map>
#include <memory>
#include <type_traits>
#include <vector>
// Explicitly include our own elf.h to avoid Linux and other dependencies.
#include "./elf.h"
#include "mem_map.h"
namespace art {
extern "C" {
struct JITCodeEntry;
template <typename ElfTypes>
class ElfFileImpl {
using Elf_Addr = typename ElfTypes::Addr;
using Elf_Off = typename ElfTypes::Off;
using Elf_Half = typename ElfTypes::Half;
using Elf_Word = typename ElfTypes::Word;
using Elf_Sword = typename ElfTypes::Sword;
using Elf_Ehdr = typename ElfTypes::Ehdr;
using Elf_Shdr = typename ElfTypes::Shdr;
using Elf_Sym = typename ElfTypes::Sym;
using Elf_Rel = typename ElfTypes::Rel;
using Elf_Rela = typename ElfTypes::Rela;
using Elf_Phdr = typename ElfTypes::Phdr;
using Elf_Dyn = typename ElfTypes::Dyn;
static ElfFileImpl* Open(File* file, bool writable, bool program_header_only,
std::string* error_msg, uint8_t* requested_base = nullptr);
static ElfFileImpl* Open(File* file, int mmap_prot, int mmap_flags, std::string* error_msg);
const File& GetFile() const {
return *file_;
uint8_t* Begin() const {
return map_->Begin();
uint8_t* End() const {
return map_->End();
size_t Size() const {
return map_->Size();
Elf_Ehdr& GetHeader() const;
Elf_Word GetProgramHeaderNum() const;
Elf_Phdr* GetProgramHeader(Elf_Word) const;
Elf_Word GetSectionHeaderNum() const;
Elf_Shdr* GetSectionHeader(Elf_Word) const;
Elf_Shdr* FindSectionByType(Elf_Word type) const;
Elf_Shdr* FindSectionByName(const std::string& name) const;
Elf_Shdr* GetSectionNameStringSection() const;
// Find .dynsym using .hash for more efficient lookup than FindSymbolAddress.
const uint8_t* FindDynamicSymbolAddress(const std::string& symbol_name) const;
static bool IsSymbolSectionType(Elf_Word section_type);
Elf_Word GetSymbolNum(Elf_Shdr&) const;
Elf_Sym* GetSymbol(Elf_Word section_type, Elf_Word i) const;
// Find address of symbol in specified table, returning 0 if it is
// not found. See FindSymbolByName for an explanation of build_map.
Elf_Addr FindSymbolAddress(Elf_Word section_type,
const std::string& symbol_name,
bool build_map);
// Lookup a string given string section and offset. Returns null for special 0 offset.
const char* GetString(Elf_Shdr&, Elf_Word) const;
Elf_Word GetDynamicNum() const;
Elf_Dyn& GetDynamic(Elf_Word) const;
Elf_Word GetRelNum(Elf_Shdr&) const;
Elf_Rel& GetRel(Elf_Shdr&, Elf_Word) const;
Elf_Word GetRelaNum(Elf_Shdr&) const;
Elf_Rela& GetRela(Elf_Shdr&, Elf_Word) const;
// Returns the expected size when the file is loaded at runtime
size_t GetLoadedSize() const;
// Load segments into memory based on PT_LOAD program headers.
// executable is true at run time, false at compile time.
bool Load(bool executable, std::string* error_msg);
bool Fixup(Elf_Addr base_address);
bool FixupDynamic(Elf_Addr base_address);
bool FixupSectionHeaders(Elf_Addr base_address);
bool FixupProgramHeaders(Elf_Addr base_address);
bool FixupSymbols(Elf_Addr base_address, bool dynamic);
bool FixupRelocations(Elf_Addr base_address);
bool FixupDebugSections(typename std::make_signed<Elf_Off>::type base_address_delta);
bool ApplyOatPatchesTo(const char* target_section_name,
typename std::make_signed<Elf_Off>::type base_address_delta);
static bool ApplyOatPatches(const uint8_t* patches, const uint8_t* patches_end,
const char* target_section_name,
typename std::make_signed<Elf_Off>::type delta,
uint8_t* to_patch, const uint8_t* to_patch_end);
bool Strip(std::string* error_msg);
ElfFileImpl(File* file, bool writable, bool program_header_only, uint8_t* requested_base);
bool Setup(int prot, int flags, std::string* error_msg);
bool SetMap(MemMap* map, std::string* error_msg);
uint8_t* GetProgramHeadersStart() const;
uint8_t* GetSectionHeadersStart() const;
Elf_Phdr& GetDynamicProgramHeader() const;
Elf_Dyn* GetDynamicSectionStart() const;
Elf_Sym* GetSymbolSectionStart(Elf_Word section_type) const;
const char* GetStringSectionStart(Elf_Word section_type) const;
Elf_Rel* GetRelSectionStart(Elf_Shdr&) const;
Elf_Rela* GetRelaSectionStart(Elf_Shdr&) const;
Elf_Word* GetHashSectionStart() const;
Elf_Word GetHashBucketNum() const;
Elf_Word GetHashChainNum() const;
Elf_Word GetHashBucket(size_t i, bool* ok) const;
Elf_Word GetHashChain(size_t i, bool* ok) const;
typedef std::map<std::string, Elf_Sym*> SymbolTable;
SymbolTable** GetSymbolTable(Elf_Word section_type);
bool ValidPointer(const uint8_t* start) const;
const Elf_Sym* FindDynamicSymbol(const std::string& symbol_name) const;
// Check that certain sections and their dependencies exist.
bool CheckSectionsExist(std::string* error_msg) const;
// Check that the link of the first section links to the second section.
bool CheckSectionsLinked(const uint8_t* source, const uint8_t* target) const;
// Check whether the offset is in range, and set to target to Begin() + offset if OK.
bool CheckAndSet(Elf32_Off offset, const char* label, uint8_t** target, std::string* error_msg);
// Find symbol in specified table, returning null if it is not found.
// If build_map is true, builds a map to speed repeated access. The
// map does not included untyped symbol values (aka STT_NOTYPE)
// since they can contain duplicates. If build_map is false, the map
// will be used if it was already created. Typically build_map
// should be set unless only a small number of symbols will be
// looked up.
Elf_Sym* FindSymbolByName(Elf_Word section_type,
const std::string& symbol_name,
bool build_map);
Elf_Phdr* FindProgamHeaderByType(Elf_Word type) const;
Elf_Dyn* FindDynamicByType(Elf_Sword type) const;
Elf_Word FindDynamicValueByType(Elf_Sword type) const;
// Lookup a string by section type. Returns null for special 0 offset.
const char* GetString(Elf_Word section_type, Elf_Word) const;
const File* const file_;
const bool writable_;
const bool program_header_only_;
// ELF header mapping. If program_header_only_ is false, will
// actually point to the entire elf file.
std::unique_ptr<MemMap> map_;
Elf_Ehdr* header_;
std::vector<MemMap*> segments_;
// Pointer to start of first PT_LOAD program segment after Load()
// when program_header_only_ is true.
uint8_t* base_address_;
// The program header should always available but use GetProgramHeadersStart() to be sure.
uint8_t* program_headers_start_;
// Conditionally available values. Use accessors to ensure they exist if they are required.
uint8_t* section_headers_start_;
Elf_Phdr* dynamic_program_header_;
Elf_Dyn* dynamic_section_start_;
Elf_Sym* symtab_section_start_;
Elf_Sym* dynsym_section_start_;
char* strtab_section_start_;
char* dynstr_section_start_;
Elf_Word* hash_section_start_;
SymbolTable* symtab_symbol_table_;
SymbolTable* dynsym_symbol_table_;
// Support for GDB JIT
uint8_t* jit_elf_image_;
JITCodeEntry* jit_gdb_entry_;
std::unique_ptr<ElfFileImpl<ElfTypes>> gdb_file_mapping_;
void GdbJITSupport();
// Override the 'base' p_vaddr in the first LOAD segment with this value (if non-null).
uint8_t* requested_base_;
} // namespace art