elfutils.cc revision 7867fcbc885065ceb6afee36b824da9d0dd47fe8 
1// Copyright (c) 2012, Google Inc.
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3//
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17//
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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#include "common/linux/elfutils-inl.h"
37
38namespace google_breakpad {
39
40namespace {
41
42template<typename ElfClass>
43void FindElfClassSection(const char *elf_base,
44                         const char *section_name,
45                         typename ElfClass::Word section_type,
46                         const void **section_start,
47                         int *section_size) {
48  typedef typename ElfClass::Ehdr Ehdr;
49  typedef typename ElfClass::Shdr Shdr;
50
51  assert(elf_base);
52  assert(section_start);
53  assert(section_size);
54
55  assert(my_strncmp(elf_base, ELFMAG, SELFMAG) == 0);
56
57  const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
58  assert(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
59
60  const Shdr* sections =
61    GetOffset<ElfClass,Shdr>(elf_header, elf_header->e_shoff);
62  const Shdr* section_names = sections + elf_header->e_shstrndx;
63  const char* names =
64    GetOffset<ElfClass,char>(elf_header, section_names->sh_offset);
65  const char *names_end = names + section_names->sh_size;
66
67  const Shdr* section =
68    FindElfSectionByName<ElfClass>(section_name, section_type,
69                                   sections, names, names_end,
70                                   elf_header->e_shnum);
71
72  if (section != NULL && section->sh_size > 0) {
73    *section_start = elf_base + section->sh_offset;
74    *section_size = section->sh_size;
75  }
76}
77
78}  // namespace
79
80bool IsValidElf(const void* elf_base) {
81  return my_strncmp(reinterpret_cast<const char*>(elf_base),
82                    ELFMAG, SELFMAG) == 0;
83}
84
85int ElfClass(const void* elf_base) {
86  const ElfW(Ehdr)* elf_header =
87    reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
88
89  return elf_header->e_ident[EI_CLASS];
90}
91
92bool FindElfSection(const void *elf_mapped_base,
93                    const char *section_name,
94                    uint32_t section_type,
95                    const void **section_start,
96                    int *section_size,
97                    int *elfclass) {
98  assert(elf_mapped_base);
99  assert(section_start);
100  assert(section_size);
101
102  *section_start = NULL;
103  *section_size = 0;
104
105  if (!IsValidElf(elf_mapped_base))
106    return false;
107
108  int cls = ElfClass(elf_mapped_base);
109  if (elfclass) {
110    *elfclass = cls;
111  }
112
113  const char* elf_base =
114    static_cast<const char*>(elf_mapped_base);
115
116  if (cls == ELFCLASS32) {
117    FindElfClassSection<ElfClass32>(elf_base, section_name, section_type,
118                                    section_start, section_size);
119    return *section_start != NULL;
120  } else if (cls == ELFCLASS64) {
121    FindElfClassSection<ElfClass64>(elf_base, section_name, section_type,
122                                    section_start, section_size);
123    return *section_start != NULL;
124  }
125
126  return false;
127}
128
129}  // namespace google_breakpad
130