src/elf_file.h

/*
 * 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
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ART_SRC_ELF_FILE_H_
#define ART_SRC_ELF_FILE_H_

#include <vector>

#include <llvm/Support/ELF.h>

#include "base/unix_file/fd_file.h"
#include "globals.h"
#include "mem_map.h"
#include "os.h"
#include "UniquePtr.h"

namespace art {

// 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 {
 public:
  static ElfFile* Open(File* file, bool writable, bool program_header_only);
  ~ElfFile();

  // Load segments into memory based on PT_LOAD program headers

  File& GetFile() const {
    return *file_;
  }

  byte* Begin() {
    return map_->Begin();
  }

  byte* End() {
    return map_->End();
  }

  size_t Size() const {
    return map_->Size();
  }

  llvm::ELF::Elf32_Ehdr& GetHeader();

  llvm::ELF::Elf32_Word GetProgramHeaderNum();
  llvm::ELF::Elf32_Phdr& GetProgramHeader(llvm::ELF::Elf32_Word);
  llvm::ELF::Elf32_Phdr* FindProgamHeaderByType(llvm::ELF::Elf32_Word type);

  llvm::ELF::Elf32_Word GetSectionHeaderNum();
  llvm::ELF::Elf32_Shdr& GetSectionHeader(llvm::ELF::Elf32_Word);
  llvm::ELF::Elf32_Shdr* FindSectionByType(llvm::ELF::Elf32_Word type);

  byte* FindDynamicSymbolAddress(const std::string& symbol_name);

  static bool IsSymbolSectionType(llvm::ELF::Elf32_Word section_type);
  llvm::ELF::Elf32_Word GetSymbolNum(llvm::ELF::Elf32_Shdr&);
  llvm::ELF::Elf32_Sym& GetSymbol(llvm::ELF::Elf32_Word section_type, llvm::ELF::Elf32_Word i);
  llvm::ELF::Elf32_Sym* FindSymbolByName(llvm::ELF::Elf32_Word section_type,
                                         const std::string& symbol_name);
  llvm::ELF::Elf32_Addr FindSymbolAddress(llvm::ELF::Elf32_Word section_type,
                                          const std::string& symbol_name);

  char* GetString(llvm::ELF::Elf32_Shdr&, llvm::ELF::Elf32_Word);

  llvm::ELF::Elf32_Word GetDynamicNum();
  llvm::ELF::Elf32_Dyn& GetDynamic(llvm::ELF::Elf32_Word);

  // Returns the expected size when the file is loaded at runtime
  size_t GetLoadedSize();

  // Load segments into memory based on PT_LOAD program headers
  bool Load();

 private:
  ElfFile();

  bool Setup(File* file, bool writable, bool program_header_only);

  bool SetMap(MemMap* map);

  byte* GetProgramHeadersStart();
  byte* GetSectionHeadersStart();
  llvm::ELF::Elf32_Phdr& GetDynamicProgramHeader();
  llvm::ELF::Elf32_Dyn* GetDynamicSectionStart();
  llvm::ELF::Elf32_Sym* GetSymbolSectionStart(llvm::ELF::Elf32_Word section_type);
  char* GetSymbolStringSectionStart(llvm::ELF::Elf32_Word section_type);
  llvm::ELF::Elf32_Word* GetHashSectionStart();
  llvm::ELF::Elf32_Word GetHashBucketNum();
  llvm::ELF::Elf32_Word GetHashChainNum();
  llvm::ELF::Elf32_Word GetHashBucket(size_t i);
  llvm::ELF::Elf32_Word GetHashChain(size_t i);

  File* file_;
  bool writable_;
  bool program_header_only_;
  UniquePtr<MemMap> map_;
  llvm::ELF::Elf32_Ehdr* header_;
  std::vector<MemMap*> segments_;
  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_;
  llvm::ELF::Elf32_Phdr* dynamic_program_header_;
  llvm::ELF::Elf32_Dyn* dynamic_section_start_;
  llvm::ELF::Elf32_Sym* symtab_section_start_;
  llvm::ELF::Elf32_Sym* dynsym_section_start_;
  char* strtab_section_start_;
  char* dynstr_section_start_;
  llvm::ELF::Elf32_Word* hash_section_start_;

};

}  // namespace art

#endif  // ART_SRC_ELF_FILE_H_