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 #include "common/linux/elfutils-inl.h"
37
38 namespace google_breakpad {
39
40 namespace {
41
42 template<typename ElfClass>
FindElfClassSection(const char * elf_base,const char * section_name,typename ElfClass::Word section_type,const void ** section_start,size_t * section_size)43 void FindElfClassSection(const char *elf_base,
44 const char *section_name,
45 typename ElfClass::Word section_type,
46 const void **section_start,
47 size_t *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 template<typename ElfClass>
FindElfClassSegment(const char * elf_base,typename ElfClass::Word segment_type,const void ** segment_start,size_t * segment_size)79 void FindElfClassSegment(const char *elf_base,
80 typename ElfClass::Word segment_type,
81 const void **segment_start,
82 size_t *segment_size) {
83 typedef typename ElfClass::Ehdr Ehdr;
84 typedef typename ElfClass::Phdr Phdr;
85
86 assert(elf_base);
87 assert(segment_start);
88 assert(segment_size);
89
90 assert(my_strncmp(elf_base, ELFMAG, SELFMAG) == 0);
91
92 const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
93 assert(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
94
95 const Phdr* phdrs =
96 GetOffset<ElfClass, Phdr>(elf_header, elf_header->e_phoff);
97
98 for (int i = 0; i < elf_header->e_phnum; ++i) {
99 if (phdrs[i].p_type == segment_type) {
100 *segment_start = elf_base + phdrs[i].p_offset;
101 *segment_size = phdrs[i].p_filesz;
102 return;
103 }
104 }
105 }
106
107 } // namespace
108
IsValidElf(const void * elf_base)109 bool IsValidElf(const void* elf_base) {
110 return my_strncmp(reinterpret_cast<const char*>(elf_base),
111 ELFMAG, SELFMAG) == 0;
112 }
113
ElfClass(const void * elf_base)114 int ElfClass(const void* elf_base) {
115 const ElfW(Ehdr)* elf_header =
116 reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
117
118 return elf_header->e_ident[EI_CLASS];
119 }
120
FindElfSection(const void * elf_mapped_base,const char * section_name,uint32_t section_type,const void ** section_start,size_t * section_size,int * elfclass)121 bool FindElfSection(const void *elf_mapped_base,
122 const char *section_name,
123 uint32_t section_type,
124 const void **section_start,
125 size_t *section_size,
126 int *elfclass) {
127 assert(elf_mapped_base);
128 assert(section_start);
129 assert(section_size);
130
131 *section_start = NULL;
132 *section_size = 0;
133
134 if (!IsValidElf(elf_mapped_base))
135 return false;
136
137 int cls = ElfClass(elf_mapped_base);
138 if (elfclass) {
139 *elfclass = cls;
140 }
141
142 const char* elf_base =
143 static_cast<const char*>(elf_mapped_base);
144
145 if (cls == ELFCLASS32) {
146 FindElfClassSection<ElfClass32>(elf_base, section_name, section_type,
147 section_start, section_size);
148 return *section_start != NULL;
149 } else if (cls == ELFCLASS64) {
150 FindElfClassSection<ElfClass64>(elf_base, section_name, section_type,
151 section_start, section_size);
152 return *section_start != NULL;
153 }
154
155 return false;
156 }
157
FindElfSegment(const void * elf_mapped_base,uint32_t segment_type,const void ** segment_start,size_t * segment_size,int * elfclass)158 bool FindElfSegment(const void *elf_mapped_base,
159 uint32_t segment_type,
160 const void **segment_start,
161 size_t *segment_size,
162 int *elfclass) {
163 assert(elf_mapped_base);
164 assert(segment_start);
165 assert(segment_size);
166
167 *segment_start = NULL;
168 *segment_size = 0;
169
170 if (!IsValidElf(elf_mapped_base))
171 return false;
172
173 int cls = ElfClass(elf_mapped_base);
174 if (elfclass) {
175 *elfclass = cls;
176 }
177
178 const char* elf_base =
179 static_cast<const char*>(elf_mapped_base);
180
181 if (cls == ELFCLASS32) {
182 FindElfClassSegment<ElfClass32>(elf_base, segment_type,
183 segment_start, segment_size);
184 return *segment_start != NULL;
185 } else if (cls == ELFCLASS64) {
186 FindElfClassSegment<ElfClass64>(elf_base, segment_type,
187 segment_start, segment_size);
188 return *segment_start != NULL;
189 }
190
191 return false;
192 }
193
194 } // namespace google_breakpad
195