1 /* Returns the build id if found in a NT_GNU_BUILD_ID note.
2 Copyright (C) 2014 Red Hat, Inc.
3 This file is part of elfutils.
4
5 This file is free software; you can redistribute it and/or modify
6 it under the terms of either
7
8 * the GNU Lesser General Public License as published by the Free
9 Software Foundation; either version 3 of the License, or (at
10 your option) any later version
11
12 or
13
14 * the GNU General Public License as published by the Free
15 Software Foundation; either version 2 of the License, or (at
16 your option) any later version
17
18 or both in parallel, as here.
19
20 elfutils is distributed in the hope that it will be useful, but
21 WITHOUT ANY WARRANTY; without even the implied warranty of
22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 General Public License for more details.
24
25 You should have received copies of the GNU General Public License and
26 the GNU Lesser General Public License along with this program. If
27 not, see <http://www.gnu.org/licenses/>. */
28
29 #ifdef HAVE_CONFIG_H
30 # include <config.h>
31 #endif
32
33 #include "libdwelfP.h"
34 #include "libdwflP.h"
35
36 #define NO_VADDR ((GElf_Addr) -1l)
37
38 static int
check_notes(Elf_Data * data,GElf_Addr data_elfaddr,const void ** build_id_bits,GElf_Addr * build_id_elfaddr,int * build_id_len)39 check_notes (Elf_Data *data, GElf_Addr data_elfaddr,
40 const void **build_id_bits, GElf_Addr *build_id_elfaddr,
41 int *build_id_len)
42 {
43 size_t pos = 0;
44 GElf_Nhdr nhdr;
45 size_t name_pos;
46 size_t desc_pos;
47 while ((pos = gelf_getnote (data, pos, &nhdr, &name_pos, &desc_pos)) > 0)
48 if (nhdr.n_type == NT_GNU_BUILD_ID
49 && nhdr.n_namesz == sizeof "GNU"
50 && !memcmp (data->d_buf + name_pos, "GNU", sizeof "GNU"))
51 {
52 *build_id_bits = data->d_buf + desc_pos;
53 *build_id_elfaddr = (data_elfaddr == NO_VADDR
54 ? 0 : data_elfaddr + desc_pos);
55 *build_id_len = nhdr.n_descsz;
56 return 1;
57 }
58 return 0;
59 }
60
61 /* Defined here for reuse. The dwelf interface doesn't care about the
62 address of the note, but libdwfl does. */
63 static int
find_elf_build_id(Dwfl_Module * mod,int e_type,Elf * elf,const void ** build_id_bits,GElf_Addr * build_id_elfaddr,int * build_id_len)64 find_elf_build_id (Dwfl_Module *mod, int e_type, Elf *elf,
65 const void **build_id_bits, GElf_Addr *build_id_elfaddr,
66 int *build_id_len)
67 {
68 size_t shstrndx = SHN_UNDEF;
69 int result = 0;
70
71 Elf_Scn *scn = elf_nextscn (elf, NULL);
72
73 if (scn == NULL)
74 {
75 /* No sections, have to look for phdrs. */
76 size_t phnum;
77 if (unlikely (elf_getphdrnum (elf, &phnum) != 0))
78 {
79 if (mod != NULL)
80 __libdwfl_seterrno (DWFL_E_LIBELF);
81 return -1;
82 }
83 for (size_t i = 0; result == 0 && i < phnum; ++i)
84 {
85 GElf_Phdr phdr_mem;
86 GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem);
87 if (likely (phdr != NULL) && phdr->p_type == PT_NOTE)
88 result = check_notes (elf_getdata_rawchunk (elf,
89 phdr->p_offset,
90 phdr->p_filesz,
91 ELF_T_NHDR),
92 phdr->p_vaddr,
93 build_id_bits,
94 build_id_elfaddr,
95 build_id_len);
96 }
97 }
98 else
99 do
100 {
101 GElf_Shdr shdr_mem;
102 GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
103 if (likely (shdr != NULL) && shdr->sh_type == SHT_NOTE)
104 {
105 /* Determine the right sh_addr in this module. */
106 GElf_Addr vaddr = 0;
107 if (!(shdr->sh_flags & SHF_ALLOC))
108 vaddr = NO_VADDR;
109 else if (mod == NULL || e_type != ET_REL)
110 vaddr = shdr->sh_addr;
111 else if (__libdwfl_relocate_value (mod, elf, &shstrndx,
112 elf_ndxscn (scn), &vaddr))
113 vaddr = NO_VADDR;
114 result = check_notes (elf_getdata (scn, NULL), vaddr,
115 build_id_bits,
116 build_id_elfaddr,
117 build_id_len);
118 }
119 }
120 while (result == 0 && (scn = elf_nextscn (elf, scn)) != NULL);
121
122 return result;
123 }
124
125 int
126 internal_function
__libdwfl_find_elf_build_id(Dwfl_Module * mod,Elf * elf,const void ** build_id_bits,GElf_Addr * build_id_elfaddr,int * build_id_len)127 __libdwfl_find_elf_build_id (Dwfl_Module *mod, Elf *elf,
128 const void **build_id_bits,
129 GElf_Addr *build_id_elfaddr, int *build_id_len)
130 {
131 GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (elf, &ehdr_mem);
132 if (unlikely (ehdr == NULL))
133 {
134 __libdwfl_seterrno (DWFL_E_LIBELF);
135 return -1;
136 }
137 // MOD->E_TYPE is zero here.
138 assert (ehdr->e_type != ET_REL || mod != NULL);
139
140 return find_elf_build_id (mod, ehdr->e_type, elf,
141 build_id_bits, build_id_elfaddr, build_id_len);
142 }
143
144 ssize_t
dwelf_elf_gnu_build_id(Elf * elf,const void ** build_idp)145 dwelf_elf_gnu_build_id (Elf *elf, const void **build_idp)
146 {
147 GElf_Addr build_id_elfaddr;
148 int build_id_len;
149 int result = find_elf_build_id (NULL, ET_NONE, elf, build_idp,
150 &build_id_elfaddr, &build_id_len);
151 if (result > 0)
152 return build_id_len;
153
154 return result;
155 }
156 INTDEF(dwelf_elf_gnu_build_id)
157