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