runtime/elf_file.h - platform/art - Git at Google

 /*
  * 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_RUNTIME_ELF_FILE_H_
 #define ART_RUNTIME_ELF_FILE_H_

 #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 {
  public:
   static ElfFile* Open(File* file, bool writable, bool program_header_only, std::string* error_msg,
                        uint8_t* requested_base = nullptr);  // TODO: move arg to before 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);
   ~ElfFile();

   // Load segments into memory based on PT_LOAD program headers

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

   // The start of the memory map address range for this ELF file.
   byte* Begin() const {
     return map_->Begin();
   }

   // The end of the memory map address range for this ELF file.
   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_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;

   Elf32_Word GetSymbolNum(Elf32_Shdr&) const;
   Elf32_Sym* GetSymbol(Elf32_Word section_type, Elf32_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.
   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;

   Elf32_Word GetDynamicNum() const;
   Elf32_Dyn& GetDynamic(Elf32_Word) 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);

  private:
   ElfFile(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);

   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, bool* ok) const;
   Elf32_Word GetHashChain(size_t i, bool* ok) const;

   typedef std::map<std::string, Elf32_Sym*> SymbolTable;
   SymbolTable** GetSymbolTable(Elf32_Word section_type);

   bool ValidPointer(const byte* start) const;

   const Elf32_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 byte* source, const byte* 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, byte** target, std::string* error_msg);

   // 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);

   Elf32_Phdr* FindProgamHeaderByType(Elf32_Word type) const;

   Elf32_Dyn* FindDynamicByType(Elf32_Sword type) const;
   Elf32_Word FindDynamicValueByType(Elf32_Sword type) const;

   // Lookup a string by section type. Returns nullptr for special 0 offset.
   const char* GetString(Elf32_Word section_type, Elf32_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_;
   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();

   // When not-null, override the base vaddr we memory map LOAD segments into.
   uint8_t* requested_base_;
 };

 }  // namespace art

 #endif  // ART_RUNTIME_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_RUNTIME_ELF_FILE_H_
	#define ART_RUNTIME_ELF_FILE_H_

	#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 {
	public:
	static ElfFile* Open(File* file, bool writable, bool program_header_only, std::string* error_msg,
	uint8_t* requested_base = nullptr); // TODO: move arg to before 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);
	~ElfFile();

	// Load segments into memory based on PT_LOAD program headers

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

	// The start of the memory map address range for this ELF file.
	byte* Begin() const {
	return map_->Begin();
	}

	// The end of the memory map address range for this ELF file.
	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_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;

	Elf32_Word GetSymbolNum(Elf32_Shdr&) const;
	Elf32_Sym* GetSymbol(Elf32_Word section_type, Elf32_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.
	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;

	Elf32_Word GetDynamicNum() const;
	Elf32_Dyn& GetDynamic(Elf32_Word) 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);

	private:
	ElfFile(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);

	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, bool* ok) const;
	Elf32_Word GetHashChain(size_t i, bool* ok) const;

	typedef std::map<std::string, Elf32_Sym*> SymbolTable;
	SymbolTable** GetSymbolTable(Elf32_Word section_type);

	bool ValidPointer(const byte* start) const;

	const Elf32_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 byte* source, const byte* 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, byte** target, std::string* error_msg);

	// 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);

	Elf32_Phdr* FindProgamHeaderByType(Elf32_Word type) const;

	Elf32_Dyn* FindDynamicByType(Elf32_Sword type) const;
	Elf32_Word FindDynamicValueByType(Elf32_Sword type) const;

	// Lookup a string by section type. Returns nullptr for special 0 offset.
	const char* GetString(Elf32_Word section_type, Elf32_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_;
	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();

	// When not-null, override the base vaddr we memory map LOAD segments into.
	uint8_t* requested_base_;
	};

	} // namespace art

	#endif // ART_RUNTIME_ELF_FILE_H_