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
29namespace art {
30
31extern "C" {
32  struct JITCodeEntry;
33}
34
35template <typename ElfTypes>
36class 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 std::string& GetFilePath() const {
65    return file_path_;
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(File* file, 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(File* file, 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(File* file, int prot, int flags, bool low_4gb, std::string* error_msg);
141
142  bool SetMap(File* file, 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(File* file, 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 std::string file_path_;
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