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_H_
18#define ART_RUNTIME_ELF_FILE_H_
19
20#include <map>
21#include <vector>
22
23#include <llvm/Support/ELF.h>
24
25#include "base/unix_file/fd_file.h"
26#include "globals.h"
27#include "mem_map.h"
28#include "os.h"
29#include "UniquePtr.h"
30
31namespace art {
32
33// Used for compile time and runtime for ElfFile access. Because of
34// the need for use at runtime, cannot directly use LLVM classes such as
35// ELFObjectFile.
36class ElfFile {
37 public:
38  static ElfFile* Open(File* file, bool writable, bool program_header_only);
39  ~ElfFile();
40
41  // Load segments into memory based on PT_LOAD program headers
42
43  File& GetFile() const {
44    return *file_;
45  }
46
47  byte* Begin() {
48    return map_->Begin();
49  }
50
51  byte* End() {
52    return map_->End();
53  }
54
55  size_t Size() const {
56    return map_->Size();
57  }
58
59  ::llvm::ELF::Elf32_Ehdr& GetHeader();
60
61  ::llvm::ELF::Elf32_Word GetProgramHeaderNum();
62  ::llvm::ELF::Elf32_Phdr& GetProgramHeader(::llvm::ELF::Elf32_Word);
63  ::llvm::ELF::Elf32_Phdr* FindProgamHeaderByType(::llvm::ELF::Elf32_Word type);
64
65  ::llvm::ELF::Elf32_Word GetSectionHeaderNum();
66  ::llvm::ELF::Elf32_Shdr& GetSectionHeader(::llvm::ELF::Elf32_Word);
67  ::llvm::ELF::Elf32_Shdr* FindSectionByType(::llvm::ELF::Elf32_Word type);
68
69  ::llvm::ELF::Elf32_Shdr& GetSectionNameStringSection();
70
71  // Find .dynsym using .hash for more efficient lookup than FindSymbolAddress.
72  byte* FindDynamicSymbolAddress(const std::string& symbol_name);
73
74  static bool IsSymbolSectionType(::llvm::ELF::Elf32_Word section_type);
75  ::llvm::ELF::Elf32_Word GetSymbolNum(::llvm::ELF::Elf32_Shdr&);
76  ::llvm::ELF::Elf32_Sym& GetSymbol(::llvm::ELF::Elf32_Word section_type, ::llvm::ELF::Elf32_Word i);
77
78  // Find symbol in specified table, returning NULL if it is not found.
79  //
80  // If build_map is true, builds a map to speed repeated access. The
81  // map does not included untyped symbol values (aka STT_NOTYPE)
82  // since they can contain duplicates. If build_map is false, the map
83  // will be used if it was already created. Typically build_map
84  // should be set unless only a small number of symbols will be
85  // looked up.
86  ::llvm::ELF::Elf32_Sym* FindSymbolByName(::llvm::ELF::Elf32_Word section_type,
87                                           const std::string& symbol_name,
88                                           bool build_map);
89
90  // Find address of symbol in specified table, returning 0 if it is
91  // not found. See FindSymbolByName for an explanation of build_map.
92  ::llvm::ELF::Elf32_Addr FindSymbolAddress(::llvm::ELF::Elf32_Word section_type,
93                                            const std::string& symbol_name,
94                                            bool build_map);
95
96  // Lookup a string given string section and offset. Returns NULL for
97  // special 0 offset.
98  const char* GetString(::llvm::ELF::Elf32_Shdr&, ::llvm::ELF::Elf32_Word);
99
100  // Lookup a string by section type. Returns NULL for special 0 offset.
101  const char* GetString(::llvm::ELF::Elf32_Word section_type, ::llvm::ELF::Elf32_Word);
102
103  ::llvm::ELF::Elf32_Word GetDynamicNum();
104  ::llvm::ELF::Elf32_Dyn& GetDynamic(::llvm::ELF::Elf32_Word);
105  ::llvm::ELF::Elf32_Word FindDynamicValueByType(::llvm::ELF::Elf32_Sword type);
106
107  ::llvm::ELF::Elf32_Word GetRelNum(::llvm::ELF::Elf32_Shdr&);
108  ::llvm::ELF::Elf32_Rel& GetRel(::llvm::ELF::Elf32_Shdr&, ::llvm::ELF::Elf32_Word);
109
110  ::llvm::ELF::Elf32_Word GetRelaNum(::llvm::ELF::Elf32_Shdr&);
111  ::llvm::ELF::Elf32_Rela& GetRela(::llvm::ELF::Elf32_Shdr&, ::llvm::ELF::Elf32_Word);
112
113  // Returns the expected size when the file is loaded at runtime
114  size_t GetLoadedSize();
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(bool executable);
119
120 private:
121  ElfFile();
122
123  bool Setup(File* file, bool writable, bool program_header_only);
124
125  bool SetMap(MemMap* map);
126
127  byte* GetProgramHeadersStart();
128  byte* GetSectionHeadersStart();
129  ::llvm::ELF::Elf32_Phdr& GetDynamicProgramHeader();
130  ::llvm::ELF::Elf32_Dyn* GetDynamicSectionStart();
131  ::llvm::ELF::Elf32_Sym* GetSymbolSectionStart(::llvm::ELF::Elf32_Word section_type);
132  const char* GetStringSectionStart(::llvm::ELF::Elf32_Word section_type);
133  ::llvm::ELF::Elf32_Rel* GetRelSectionStart(::llvm::ELF::Elf32_Shdr&);
134  ::llvm::ELF::Elf32_Rela* GetRelaSectionStart(::llvm::ELF::Elf32_Shdr&);
135  ::llvm::ELF::Elf32_Word* GetHashSectionStart();
136  ::llvm::ELF::Elf32_Word GetHashBucketNum();
137  ::llvm::ELF::Elf32_Word GetHashChainNum();
138  ::llvm::ELF::Elf32_Word GetHashBucket(size_t i);
139  ::llvm::ELF::Elf32_Word GetHashChain(size_t i);
140
141  typedef std::map<std::string, ::llvm::ELF::Elf32_Sym*> SymbolTable;
142  SymbolTable** GetSymbolTable(::llvm::ELF::Elf32_Word section_type);
143
144  File* file_;
145  bool writable_;
146  bool program_header_only_;
147
148  // ELF header mapping. If program_header_only_ is false, will actually point to the entire elf file.
149  UniquePtr<MemMap> map_;
150  ::llvm::ELF::Elf32_Ehdr* header_;
151  std::vector<MemMap*> segments_;
152
153  // Pointer to start of first PT_LOAD program segment after Load() when program_header_only_ is true.
154  byte* base_address_;
155
156  // The program header should always available but use GetProgramHeadersStart() to be sure.
157  byte* program_headers_start_;
158
159  // Conditionally available values. Use accessors to ensure they exist if they are required.
160  byte* section_headers_start_;
161  ::llvm::ELF::Elf32_Phdr* dynamic_program_header_;
162  ::llvm::ELF::Elf32_Dyn* dynamic_section_start_;
163  ::llvm::ELF::Elf32_Sym* symtab_section_start_;
164  ::llvm::ELF::Elf32_Sym* dynsym_section_start_;
165  const char* strtab_section_start_;
166  const char* dynstr_section_start_;
167  ::llvm::ELF::Elf32_Word* hash_section_start_;
168
169  SymbolTable* symtab_symbol_table_;
170  SymbolTable* dynsym_symbol_table_;
171};
172
173}  // namespace art
174
175#endif  // ART_RUNTIME_ELF_FILE_H_
176