1 /* 2 * Copyright (C) 2012 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_ELF_FILE_IMPL_H_ 18 #define ART_RUNTIME_ELF_FILE_IMPL_H_ 19 20 #include <map> 21 #include <memory> 22 #include <type_traits> 23 #include <vector> 24 25 // Explicitly include our own elf.h to avoid Linux and other dependencies. 26 #include "./elf.h" 27 #include "mem_map.h" 28 29 namespace art { 30 31 template <typename ElfTypes> 32 class ElfFileImpl { 33 public: 34 using Elf_Addr = typename ElfTypes::Addr; 35 using Elf_Off = typename ElfTypes::Off; 36 using Elf_Half = typename ElfTypes::Half; 37 using Elf_Word = typename ElfTypes::Word; 38 using Elf_Sword = typename ElfTypes::Sword; 39 using Elf_Ehdr = typename ElfTypes::Ehdr; 40 using Elf_Shdr = typename ElfTypes::Shdr; 41 using Elf_Sym = typename ElfTypes::Sym; 42 using Elf_Rel = typename ElfTypes::Rel; 43 using Elf_Rela = typename ElfTypes::Rela; 44 using Elf_Phdr = typename ElfTypes::Phdr; 45 using Elf_Dyn = typename ElfTypes::Dyn; 46 47 static ElfFileImpl* Open(File* file, 48 bool writable, 49 bool program_header_only, 50 bool low_4gb, 51 std::string* error_msg, 52 uint8_t* requested_base = nullptr); 53 static ElfFileImpl* Open(File* file, 54 int mmap_prot, 55 int mmap_flags, 56 bool low_4gb, 57 std::string* error_msg); 58 ~ElfFileImpl(); 59 60 const std::string& GetFilePath() const { 61 return file_path_; 62 } 63 64 uint8_t* Begin() const { 65 return map_->Begin(); 66 } 67 68 uint8_t* End() const { 69 return map_->End(); 70 } 71 72 size_t Size() const { 73 return map_->Size(); 74 } 75 76 Elf_Ehdr& GetHeader() const; 77 78 Elf_Word GetProgramHeaderNum() const; 79 Elf_Phdr* GetProgramHeader(Elf_Word) const; 80 81 Elf_Word GetSectionHeaderNum() const; 82 Elf_Shdr* GetSectionHeader(Elf_Word) const; 83 Elf_Shdr* FindSectionByType(Elf_Word type) const; 84 Elf_Shdr* FindSectionByName(const std::string& name) const; 85 86 Elf_Shdr* GetSectionNameStringSection() const; 87 88 // Find .dynsym using .hash for more efficient lookup than FindSymbolAddress. 89 const uint8_t* FindDynamicSymbolAddress(const std::string& symbol_name) const; 90 91 static bool IsSymbolSectionType(Elf_Word section_type); 92 Elf_Word GetSymbolNum(Elf_Shdr&) const; 93 Elf_Sym* GetSymbol(Elf_Word section_type, Elf_Word i) const; 94 95 // Find address of symbol in specified table, returning 0 if it is 96 // not found. See FindSymbolByName for an explanation of build_map. 97 Elf_Addr FindSymbolAddress(Elf_Word section_type, 98 const std::string& symbol_name, 99 bool build_map); 100 101 // Lookup a string given string section and offset. Returns null for special 0 offset. 102 const char* GetString(Elf_Shdr&, Elf_Word) const; 103 104 Elf_Word GetDynamicNum() const; 105 Elf_Dyn& GetDynamic(Elf_Word) const; 106 107 Elf_Word GetRelNum(Elf_Shdr&) const; 108 Elf_Rel& GetRel(Elf_Shdr&, Elf_Word) const; 109 110 Elf_Word GetRelaNum(Elf_Shdr&) const; 111 Elf_Rela& GetRela(Elf_Shdr&, Elf_Word) const; 112 113 // Retrieves the expected size when the file is loaded at runtime. Returns true if successful. 114 bool GetLoadedSize(size_t* size, std::string* error_msg) const; 115 116 // Load segments into memory based on PT_LOAD program headers. 117 // executable is true at run time, false at compile time. 118 bool Load(File* file, bool executable, bool low_4gb, std::string* error_msg); 119 120 bool Fixup(Elf_Addr base_address); 121 bool FixupDynamic(Elf_Addr base_address); 122 bool FixupSectionHeaders(Elf_Addr base_address); 123 bool FixupProgramHeaders(Elf_Addr base_address); 124 bool FixupSymbols(Elf_Addr base_address, bool dynamic); 125 bool FixupRelocations(Elf_Addr base_address); 126 bool FixupDebugSections(Elf_Addr base_address_delta); 127 bool ApplyOatPatchesTo(const char* target_section_name, Elf_Addr base_address_delta); 128 static void ApplyOatPatches(const uint8_t* patches, const uint8_t* patches_end, Elf_Addr delta, 129 uint8_t* to_patch, const uint8_t* to_patch_end); 130 131 bool Strip(File* file, std::string* error_msg); 132 133 private: 134 ElfFileImpl(File* file, bool writable, bool program_header_only, uint8_t* requested_base); 135 136 bool Setup(File* file, int prot, int flags, bool low_4gb, std::string* error_msg); 137 138 bool SetMap(File* file, MemMap* map, std::string* error_msg); 139 140 uint8_t* GetProgramHeadersStart() const; 141 uint8_t* GetSectionHeadersStart() const; 142 Elf_Phdr& GetDynamicProgramHeader() const; 143 Elf_Dyn* GetDynamicSectionStart() const; 144 Elf_Sym* GetSymbolSectionStart(Elf_Word section_type) const; 145 const char* GetStringSectionStart(Elf_Word section_type) const; 146 Elf_Rel* GetRelSectionStart(Elf_Shdr&) const; 147 Elf_Rela* GetRelaSectionStart(Elf_Shdr&) const; 148 Elf_Word* GetHashSectionStart() const; 149 Elf_Word GetHashBucketNum() const; 150 Elf_Word GetHashChainNum() const; 151 Elf_Word GetHashBucket(size_t i, bool* ok) const; 152 Elf_Word GetHashChain(size_t i, bool* ok) const; 153 154 typedef std::map<std::string, Elf_Sym*> SymbolTable; 155 SymbolTable** GetSymbolTable(Elf_Word section_type); 156 157 bool ValidPointer(const uint8_t* start) const; 158 159 const Elf_Sym* FindDynamicSymbol(const std::string& symbol_name) const; 160 161 // Check that certain sections and their dependencies exist. 162 bool CheckSectionsExist(File* file, std::string* error_msg) const; 163 164 // Check that the link of the first section links to the second section. 165 bool CheckSectionsLinked(const uint8_t* source, const uint8_t* target) const; 166 167 // Check whether the offset is in range, and set to target to Begin() + offset if OK. 168 bool CheckAndSet(Elf32_Off offset, const char* label, uint8_t** target, std::string* error_msg); 169 170 // Find symbol in specified table, returning null if it is not found. 171 // 172 // If build_map is true, builds a map to speed repeated access. The 173 // map does not included untyped symbol values (aka STT_NOTYPE) 174 // since they can contain duplicates. If build_map is false, the map 175 // will be used if it was already created. Typically build_map 176 // should be set unless only a small number of symbols will be 177 // looked up. 178 Elf_Sym* FindSymbolByName(Elf_Word section_type, 179 const std::string& symbol_name, 180 bool build_map); 181 182 Elf_Phdr* FindProgamHeaderByType(Elf_Word type) const; 183 184 Elf_Dyn* FindDynamicByType(Elf_Sword type) const; 185 Elf_Word FindDynamicValueByType(Elf_Sword type) const; 186 187 // Lookup a string by section type. Returns null for special 0 offset. 188 const char* GetString(Elf_Word section_type, Elf_Word) const; 189 190 const std::string file_path_; 191 const bool writable_; 192 const bool program_header_only_; 193 194 // ELF header mapping. If program_header_only_ is false, will 195 // actually point to the entire elf file. 196 std::unique_ptr<MemMap> map_; 197 Elf_Ehdr* header_; 198 std::vector<MemMap*> segments_; 199 200 // Pointer to start of first PT_LOAD program segment after Load() 201 // when program_header_only_ is true. 202 uint8_t* base_address_; 203 204 // The program header should always available but use GetProgramHeadersStart() to be sure. 205 uint8_t* program_headers_start_; 206 207 // Conditionally available values. Use accessors to ensure they exist if they are required. 208 uint8_t* section_headers_start_; 209 Elf_Phdr* dynamic_program_header_; 210 Elf_Dyn* dynamic_section_start_; 211 Elf_Sym* symtab_section_start_; 212 Elf_Sym* dynsym_section_start_; 213 char* strtab_section_start_; 214 char* dynstr_section_start_; 215 Elf_Word* hash_section_start_; 216 217 SymbolTable* symtab_symbol_table_; 218 SymbolTable* dynsym_symbol_table_; 219 220 // Override the 'base' p_vaddr in the first LOAD segment with this value (if non-null). 221 uint8_t* requested_base_; 222 223 DISALLOW_COPY_AND_ASSIGN(ElfFileImpl); 224 }; 225 226 } // namespace art 227 228 #endif // ART_RUNTIME_ELF_FILE_IMPL_H_ 229
