1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
|
// -*- mode: c++ -*-
// Copyright (c) 2011 Google Inc. All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// Original author: Ted Mielczarek <ted.mielczarek@gmail.com>
#include "common/linux/elf_symbols_to_module.h"
#include <elf.h>
#include <string.h>
#include "common/byte_cursor.h"
#include "common/module.h"
namespace google_breakpad {
class ELFSymbolIterator {
public:
// The contents of an ELF symbol, adjusted for the host's endianness,
// word size, and so on. Corresponds to the data in Elf32_Sym / Elf64_Sym.
struct Symbol {
// True if this iterator has reached the end of the symbol array. When
// this is set, the other members of this structure are not valid.
bool at_end;
// The number of this symbol within the list.
size_t index;
// The current symbol's name offset. This is the offset within the
// string table.
size_t name_offset;
// The current symbol's value, size, info and shndx fields.
uint64_t value;
uint64_t size;
unsigned char info;
uint16_t shndx;
};
// Create an ELFSymbolIterator walking the symbols in BUFFER. Treat the
// symbols as big-endian if BIG_ENDIAN is true, as little-endian
// otherwise. Assume each symbol has a 'value' field whose size is
// VALUE_SIZE.
//
ELFSymbolIterator(const ByteBuffer *buffer, bool big_endian,
size_t value_size)
: value_size_(value_size), cursor_(buffer, big_endian) {
// Actually, weird sizes could be handled just fine, but they're
// probably mistakes --- expressed in bits, say.
assert(value_size == 4 || value_size == 8);
symbol_.index = 0;
Fetch();
}
// Move to the next symbol. This function's behavior is undefined if
// at_end() is true when it is called.
ELFSymbolIterator &operator++() { Fetch(); symbol_.index++; return *this; }
// Dereferencing this iterator produces a reference to an Symbol structure
// that holds the current symbol's values. The symbol is owned by this
// SymbolIterator, and will be invalidated at the next call to operator++.
const Symbol &operator*() const { return symbol_; }
const Symbol *operator->() const { return &symbol_; }
private:
// Read the symbol at cursor_, and set symbol_ appropriately.
void Fetch() {
// Elf32_Sym and Elf64_Sym have different layouts.
unsigned char other;
if (value_size_ == 4) {
// Elf32_Sym
cursor_
.Read(4, false, &symbol_.name_offset)
.Read(4, false, &symbol_.value)
.Read(4, false, &symbol_.size)
.Read(1, false, &symbol_.info)
.Read(1, false, &other)
.Read(2, false, &symbol_.shndx);
} else {
// Elf64_Sym
cursor_
.Read(4, false, &symbol_.name_offset)
.Read(1, false, &symbol_.info)
.Read(1, false, &other)
.Read(2, false, &symbol_.shndx)
.Read(8, false, &symbol_.value)
.Read(8, false, &symbol_.size);
}
symbol_.at_end = !cursor_;
}
// The size of symbols' value field, in bytes.
size_t value_size_;
// A byte cursor traversing buffer_.
ByteCursor cursor_;
// Values for the symbol this iterator refers to.
Symbol symbol_;
};
const char *SymbolString(ptrdiff_t offset, ByteBuffer& strings) {
if (offset < 0 || (size_t) offset >= strings.Size()) {
// Return the null string.
offset = 0;
}
return reinterpret_cast<const char *>(strings.start + offset);
}
bool ELFSymbolsToModule(const uint8_t *symtab_section,
size_t symtab_size,
const uint8_t *string_section,
size_t string_size,
const bool big_endian,
size_t value_size,
Module *module) {
ByteBuffer symbols(symtab_section, symtab_size);
// Ensure that the string section is null-terminated.
if (string_section[string_size - 1] != '\0') {
const void* null_terminator = memrchr(string_section, '\0', string_size);
string_size = reinterpret_cast<const uint8_t*>(null_terminator)
- string_section;
}
ByteBuffer strings(string_section, string_size);
// The iterator walking the symbol table.
ELFSymbolIterator iterator(&symbols, big_endian, value_size);
while(!iterator->at_end) {
if (ELF32_ST_TYPE(iterator->info) == STT_FUNC &&
iterator->shndx != SHN_UNDEF) {
Module::Extern *ext = new Module::Extern;
ext->name = SymbolString(iterator->name_offset, strings);
ext->address = iterator->value;
module->AddExtern(ext);
}
++iterator;
}
return true;
}
} // namespace google_breakpad
|
