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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 <vector>
#include "base/unix_file/fd_file.h"
#include "globals.h"
#include "elf_utils.h"
#include "mem_map.h"
#include "os.h"
namespace art {
// Interface to GDB JIT for backtrace information.
extern "C" {
struct JITCodeEntry;
// Used for compile time and runtime for ElfFile access. Because of
// the need for use at runtime, cannot directly use LLVM classes such as
// ELFObjectFile.
class ElfFile {
static ElfFile* Open(File* file, bool writable, bool program_header_only, std::string* error_msg);
// Open with specific mmap flags, Always maps in the whole file, not just the
// program header sections.
static ElfFile* Open(File* file, int mmap_prot, int mmap_flags, std::string* error_msg);
// Load segments into memory based on PT_LOAD program headers
const File& GetFile() const {
return *file_;
byte* Begin() const {
return map_->Begin();
byte* End() const {
return map_->End();
size_t Size() const {
return map_->Size();
Elf32_Ehdr& GetHeader() const;
Elf32_Word GetProgramHeaderNum() const;
Elf32_Phdr& GetProgramHeader(Elf32_Word) const;
Elf32_Phdr* FindProgamHeaderByType(Elf32_Word type) const;
Elf32_Word GetSectionHeaderNum() const;
Elf32_Shdr& GetSectionHeader(Elf32_Word) const;
Elf32_Shdr* FindSectionByType(Elf32_Word type) const;
Elf32_Shdr* FindSectionByName(const std::string& name) const;
Elf32_Shdr& GetSectionNameStringSection() const;
// Find .dynsym using .hash for more efficient lookup than FindSymbolAddress.
const byte* FindDynamicSymbolAddress(const std::string& symbol_name) const;
const Elf32_Sym* FindDynamicSymbol(const std::string& symbol_name) const;
static bool IsSymbolSectionType(Elf32_Word section_type);
Elf32_Word GetSymbolNum(Elf32_Shdr&) const;
Elf32_Sym& GetSymbol(Elf32_Word section_type, Elf32_Word i) const;
// Find symbol in specified table, returning nullptr 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.
Elf32_Sym* FindSymbolByName(Elf32_Word section_type,
const std::string& symbol_name,
bool build_map);
// Find address of symbol in specified table, returning 0 if it is
// not found. See FindSymbolByName for an explanation of build_map.
Elf32_Addr FindSymbolAddress(Elf32_Word section_type,
const std::string& symbol_name,
bool build_map);
// Lookup a string given string section and offset. Returns nullptr for
// special 0 offset.
const char* GetString(Elf32_Shdr&, Elf32_Word) const;
// Lookup a string by section type. Returns nullptr for special 0 offset.
const char* GetString(Elf32_Word section_type, Elf32_Word) const;
Elf32_Word GetDynamicNum() const;
Elf32_Dyn& GetDynamic(Elf32_Word) const;
Elf32_Word FindDynamicValueByType(Elf32_Sword type) const;
Elf32_Word GetRelNum(Elf32_Shdr&) const;
Elf32_Rel& GetRel(Elf32_Shdr&, Elf32_Word) const;
Elf32_Word GetRelaNum(Elf32_Shdr&) const;
Elf32_Rela& GetRela(Elf32_Shdr&, Elf32_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);
ElfFile(File* file, bool writable, bool program_header_only);
bool Setup(int prot, int flags, std::string* error_msg);
bool SetMap(MemMap* map, std::string* error_msg);
byte* GetProgramHeadersStart() const;
byte* GetSectionHeadersStart() const;
Elf32_Phdr& GetDynamicProgramHeader() const;
Elf32_Dyn* GetDynamicSectionStart() const;
Elf32_Sym* GetSymbolSectionStart(Elf32_Word section_type) const;
const char* GetStringSectionStart(Elf32_Word section_type) const;
Elf32_Rel* GetRelSectionStart(Elf32_Shdr&) const;
Elf32_Rela* GetRelaSectionStart(Elf32_Shdr&) const;
Elf32_Word* GetHashSectionStart() const;
Elf32_Word GetHashBucketNum() const;
Elf32_Word GetHashChainNum() const;
Elf32_Word GetHashBucket(size_t i) const;
Elf32_Word GetHashChain(size_t i) const;
typedef std::map<std::string, Elf32_Sym*> SymbolTable;
SymbolTable** GetSymbolTable(Elf32_Word section_type);
bool ValidPointer(const byte* start) 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_;
Elf32_Ehdr* header_;
std::vector<MemMap*> segments_;
// Pointer to start of first PT_LOAD program segment after Load()
// when program_header_only_ is true.
byte* base_address_;
// The program header should always available but use GetProgramHeadersStart() to be sure.
byte* program_headers_start_;
// Conditionally available values. Use accessors to ensure they exist if they are required.
byte* section_headers_start_;
Elf32_Phdr* dynamic_program_header_;
Elf32_Dyn* dynamic_section_start_;
Elf32_Sym* symtab_section_start_;
Elf32_Sym* dynsym_section_start_;
char* strtab_section_start_;
char* dynstr_section_start_;
Elf32_Word* hash_section_start_;
SymbolTable* symtab_symbol_table_;
SymbolTable* dynsym_symbol_table_;
// Support for GDB JIT
byte* jit_elf_image_;
JITCodeEntry* jit_gdb_entry_;
std::unique_ptr<ElfFile> gdb_file_mapping_;
void GdbJITSupport();
} // namespace art