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 extern "C" { 32 struct JITCodeEntry; 33 } 34 35 template <typename ElfTypes> 36 class ElfFileImpl { 37 public: 38 using Elf_Addr = typename ElfTypes::Addr; 39 using Elf_Off = typename ElfTypes::Off; 40 using Elf_Half = typename ElfTypes::Half; 41 using Elf_Word = typename ElfTypes::Word; 42 using Elf_Sword = typename ElfTypes::Sword; 43 using Elf_Ehdr = typename ElfTypes::Ehdr; 44 using Elf_Shdr = typename ElfTypes::Shdr; 45 using Elf_Sym = typename ElfTypes::Sym; 46 using Elf_Rel = typename ElfTypes::Rel; 47 using Elf_Rela = typename ElfTypes::Rela; 48 using Elf_Phdr = typename ElfTypes::Phdr; 49 using Elf_Dyn = typename ElfTypes::Dyn; 50 51 static ElfFileImpl* Open(File* file, 52 bool writable, 53 bool program_header_only, 54 bool low_4gb, 55 std::string* error_msg, 56 uint8_t* requested_base = nullptr); 57 static ElfFileImpl* Open(File* file, 58 int mmap_prot, 59 int mmap_flags, 60 bool low_4gb, 61 std::string* error_msg); 62 ~ElfFileImpl(); 63 64 const File& GetFile() const { 65 return *file_; 66 } 67 68 uint8_t* Begin() const { 69 return map_->Begin(); 70 } 71 72 uint8_t* End() const { 73 return map_->End(); 74 } 75 76 size_t Size() const { 77 return map_->Size(); 78 } 79 80 Elf_Ehdr& GetHeader() const; 81 82 Elf_Word GetProgramHeaderNum() const; 83 Elf_Phdr* GetProgramHeader(Elf_Word) const; 84 85 Elf_Word GetSectionHeaderNum() const; 86 Elf_Shdr* GetSectionHeader(Elf_Word) const; 87 Elf_Shdr* FindSectionByType(Elf_Word type) const; 88 Elf_Shdr* FindSectionByName(const std::string& name) const; 89 90 Elf_Shdr* GetSectionNameStringSection() const; 91 92 // Find .dynsym using .hash for more efficient lookup than FindSymbolAddress. 93 const uint8_t* FindDynamicSymbolAddress(const std::string& symbol_name) const; 94 95 static bool IsSymbolSectionType(Elf_Word section_type); 96 Elf_Word GetSymbolNum(Elf_Shdr&) const; 97 Elf_Sym* GetSymbol(Elf_Word section_type, Elf_Word i) const; 98 99 // Find address of symbol in specified table, returning 0 if it is 100 // not found. See FindSymbolByName for an explanation of build_map. 101 Elf_Addr FindSymbolAddress(Elf_Word section_type, 102 const std::string& symbol_name, 103 bool build_map); 104 105 // Lookup a string given string section and offset. Returns null for special 0 offset. 106 const char* GetString(Elf_Shdr&, Elf_Word) const; 107 108 Elf_Word GetDynamicNum() const; 109 Elf_Dyn& GetDynamic(Elf_Word) const; 110 111 Elf_Word GetRelNum(Elf_Shdr&) const; 112 Elf_Rel& GetRel(Elf_Shdr&, Elf_Word) const; 113 114 Elf_Word GetRelaNum(Elf_Shdr&) const; 115 Elf_Rela& GetRela(Elf_Shdr&, Elf_Word) const; 116 117 // Retrieves the expected size when the file is loaded at runtime. Returns true if successful. 118 bool GetLoadedSize(size_t* size, std::string* error_msg) const; 119 120 // Load segments into memory based on PT_LOAD program headers. 121 // executable is true at run time, false at compile time. 122 bool Load(bool executable, bool low_4gb, std::string* error_msg); 123 124 bool Fixup(Elf_Addr base_address); 125 bool FixupDynamic(Elf_Addr base_address); 126 bool FixupSectionHeaders(Elf_Addr base_address); 127 bool FixupProgramHeaders(Elf_Addr base_address); 128 bool FixupSymbols(Elf_Addr base_address, bool dynamic); 129 bool FixupRelocations(Elf_Addr base_address); 130 bool FixupDebugSections(Elf_Addr base_address_delta); 131 bool ApplyOatPatchesTo(const char* target_section_name, Elf_Addr base_address_delta); 132 static void ApplyOatPatches(const uint8_t* patches, const uint8_t* patches_end, Elf_Addr delta, 133 uint8_t* to_patch, const uint8_t* to_patch_end); 134 135 bool Strip(std::string* error_msg); 136 137 private: 138 ElfFileImpl(File* file, bool writable, bool program_header_only, uint8_t* requested_base); 139 140 bool Setup(int prot, int flags, bool low_4gb, std::string* error_msg); 141 142 bool SetMap(MemMap* map, std::string* error_msg); 143 144 uint8_t* GetProgramHeadersStart() const; 145 uint8_t* GetSectionHeadersStart() const; 146 Elf_Phdr& GetDynamicProgramHeader() const; 147 Elf_Dyn* GetDynamicSectionStart() const; 148 Elf_Sym* GetSymbolSectionStart(Elf_Word section_type) const; 149 const char* GetStringSectionStart(Elf_Word section_type) const; 150 Elf_Rel* GetRelSectionStart(Elf_Shdr&) const; 151 Elf_Rela* GetRelaSectionStart(Elf_Shdr&) const; 152 Elf_Word* GetHashSectionStart() const; 153 Elf_Word GetHashBucketNum() const; 154 Elf_Word GetHashChainNum() const; 155 Elf_Word GetHashBucket(size_t i, bool* ok) const; 156 Elf_Word GetHashChain(size_t i, bool* ok) const; 157 158 typedef std::map<std::string, Elf_Sym*> SymbolTable; 159 SymbolTable** GetSymbolTable(Elf_Word section_type); 160 161 bool ValidPointer(const uint8_t* start) const; 162 163 const Elf_Sym* FindDynamicSymbol(const std::string& symbol_name) const; 164 165 // Check that certain sections and their dependencies exist. 166 bool CheckSectionsExist(std::string* error_msg) const; 167 168 // Check that the link of the first section links to the second section. 169 bool CheckSectionsLinked(const uint8_t* source, const uint8_t* target) const; 170 171 // Check whether the offset is in range, and set to target to Begin() + offset if OK. 172 bool CheckAndSet(Elf32_Off offset, const char* label, uint8_t** target, std::string* error_msg); 173 174 // Find symbol in specified table, returning null if it is not found. 175 // 176 // If build_map is true, builds a map to speed repeated access. The 177 // map does not included untyped symbol values (aka STT_NOTYPE) 178 // since they can contain duplicates. If build_map is false, the map 179 // will be used if it was already created. Typically build_map 180 // should be set unless only a small number of symbols will be 181 // looked up. 182 Elf_Sym* FindSymbolByName(Elf_Word section_type, 183 const std::string& symbol_name, 184 bool build_map); 185 186 Elf_Phdr* FindProgamHeaderByType(Elf_Word type) const; 187 188 Elf_Dyn* FindDynamicByType(Elf_Sword type) const; 189 Elf_Word FindDynamicValueByType(Elf_Sword type) const; 190 191 // Lookup a string by section type. Returns null for special 0 offset. 192 const char* GetString(Elf_Word section_type, Elf_Word) const; 193 194 const File* const file_; 195 const bool writable_; 196 const bool program_header_only_; 197 198 // ELF header mapping. If program_header_only_ is false, will 199 // actually point to the entire elf file. 200 std::unique_ptr<MemMap> map_; 201 Elf_Ehdr* header_; 202 std::vector<MemMap*> segments_; 203 204 // Pointer to start of first PT_LOAD program segment after Load() 205 // when program_header_only_ is true. 206 uint8_t* base_address_; 207 208 // The program header should always available but use GetProgramHeadersStart() to be sure. 209 uint8_t* program_headers_start_; 210 211 // Conditionally available values. Use accessors to ensure they exist if they are required. 212 uint8_t* section_headers_start_; 213 Elf_Phdr* dynamic_program_header_; 214 Elf_Dyn* dynamic_section_start_; 215 Elf_Sym* symtab_section_start_; 216 Elf_Sym* dynsym_section_start_; 217 char* strtab_section_start_; 218 char* dynstr_section_start_; 219 Elf_Word* hash_section_start_; 220 221 SymbolTable* symtab_symbol_table_; 222 SymbolTable* dynsym_symbol_table_; 223 224 // Override the 'base' p_vaddr in the first LOAD segment with this value (if non-null). 225 uint8_t* requested_base_; 226 227 DISALLOW_COPY_AND_ASSIGN(ElfFileImpl); 228 }; 229 230 } // namespace art 231 232 #endif // ART_RUNTIME_ELF_FILE_IMPL_H_ 233
