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 (phdr->p_align == 8
92 ? ELF_T_NHDR8
93 : ELF_T_NHDR)),
94 phdr->p_vaddr,
95 build_id_bits,
96 build_id_elfaddr,
97 build_id_len);
98 }
99 }
100 else
101 do
102 {
103 GElf_Shdr shdr_mem;
104 GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
105 if (likely (shdr != NULL) && shdr->sh_type == SHT_NOTE)
106 {
107 /* Determine the right sh_addr in this module. */
108 GElf_Addr vaddr = 0;
109 if (!(shdr->sh_flags & SHF_ALLOC))
110 vaddr = NO_VADDR;
111 else if (mod == NULL || e_type != ET_REL)
112 vaddr = shdr->sh_addr;
113 else if (__libdwfl_relocate_value (mod, elf, &shstrndx,
114 elf_ndxscn (scn), &vaddr))
115 vaddr = NO_VADDR;
116 result = check_notes (elf_getdata (scn, NULL), vaddr,
117 build_id_bits,
118 build_id_elfaddr,
119 build_id_len);
120 }
121 }
122 while (result == 0 && (scn = elf_nextscn (elf, scn)) != NULL);
123
124 return result;
125 }
126
127 int
128 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)129 __libdwfl_find_elf_build_id (Dwfl_Module *mod, Elf *elf,
130 const void **build_id_bits,
131 GElf_Addr *build_id_elfaddr, int *build_id_len)
132 {
133 GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (elf, &ehdr_mem);
134 if (unlikely (ehdr == NULL))
135 {
136 __libdwfl_seterrno (DWFL_E_LIBELF);
137 return -1;
138 }
139 // MOD->E_TYPE is zero here.
140 assert (ehdr->e_type != ET_REL || mod != NULL);
141
142 return find_elf_build_id (mod, ehdr->e_type, elf,
143 build_id_bits, build_id_elfaddr, build_id_len);
144 }
145
146 ssize_t
dwelf_elf_gnu_build_id(Elf * elf,const void ** build_idp)147 dwelf_elf_gnu_build_id (Elf *elf, const void **build_idp)
148 {
149 GElf_Addr build_id_elfaddr;
150 int build_id_len;
151 int result = find_elf_build_id (NULL, ET_NONE, elf, build_idp,
152 &build_id_elfaddr, &build_id_len);
153 if (result > 0)
154 return build_id_len;
155
156 return result;
157 }
158 INTDEF(dwelf_elf_gnu_build_id)
159