elfutils.cc revision c71d9b4e80f47028a86b0392ba3b7c8d66590664 
1// Copyright (c) 2012, Google Inc.
2// All rights reserved.
3//
4// Redistribution and use in source and binary forms, with or without
5// modification, are permitted provided that the following conditions are
6// met:
7//
8//     * Redistributions of source code must retain the above copyright
9// notice, this list of conditions and the following disclaimer.
10//     * Redistributions in binary form must reproduce the above
11// copyright notice, this list of conditions and the following disclaimer
12// in the documentation and/or other materials provided with the
13// distribution.
14//     * Neither the name of Google Inc. nor the names of its
15// contributors may be used to endorse or promote products derived from
16// this software without specific prior written permission.
17//
18// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30#include "common/linux/elfutils.h"
31
32#include <assert.h>
33#include <string.h>
34
35#include "common/linux/linux_libc_support.h"
36
37namespace google_breakpad {
38
39namespace {
40
41template<typename ElfClass>
42void FindElfClassSection(const char *elf_base,
43                         const char *section_name,
44                         uint32_t section_type,
45                         const void **section_start,
46                         int *section_size) {
47  typedef typename ElfClass::Ehdr Ehdr;
48  typedef typename ElfClass::Shdr Shdr;
49
50  assert(elf_base);
51  assert(section_start);
52  assert(section_size);
53
54  assert(my_strncmp(elf_base, ELFMAG, SELFMAG) == 0);
55
56  int name_len = my_strlen(section_name);
57
58  const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
59  assert(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
60
61  const Shdr* sections =
62      reinterpret_cast<const Shdr*>(elf_base + elf_header->e_shoff);
63  const Shdr* string_section = sections + elf_header->e_shstrndx;
64
65  const Shdr* section = NULL;
66  for (int i = 0; i < elf_header->e_shnum; ++i) {
67    if (sections[i].sh_type == section_type) {
68      const char* current_section_name = (char*)(elf_base +
69                                                 string_section->sh_offset +
70                                                 sections[i].sh_name);
71      if (!my_strncmp(current_section_name, section_name, name_len)) {
72        section = &sections[i];
73        break;
74      }
75    }
76  }
77  if (section != NULL && section->sh_size > 0) {
78    *section_start = elf_base + section->sh_offset;
79    *section_size = section->sh_size;
80  }
81}
82
83}  // namespace
84
85bool FindElfSection(const void *elf_mapped_base,
86                    const char *section_name,
87                    uint32_t section_type,
88                    const void **section_start,
89                    int *section_size,
90                    int *elfclass) {
91  assert(elf_mapped_base);
92  assert(section_start);
93  assert(section_size);
94
95  *section_start = NULL;
96  *section_size = 0;
97
98  const char* elf_base =
99    static_cast<const char*>(elf_mapped_base);
100  const ElfW(Ehdr)* elf_header =
101    reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
102  if (my_strncmp(elf_base, ELFMAG, SELFMAG) != 0)
103    return false;
104
105  if (elfclass) {
106    *elfclass = elf_header->e_ident[EI_CLASS];
107  }
108
109  if (elf_header->e_ident[EI_CLASS] == ELFCLASS32) {
110    FindElfClassSection<ElfClass32>(elf_base, section_name, section_type,
111                                    section_start, section_size);
112    return *section_start != NULL;
113  } else if (elf_header->e_ident[EI_CLASS] == ELFCLASS64) {
114    FindElfClassSection<ElfClass64>(elf_base, section_name, section_type,
115                                    section_start, section_size);
116    return *section_start != NULL;
117  }
118
119  return false;
120}
121
122}  // namespace google_breakpad
123