1 /*
2 * Copyright © 2016 Intel Corporation
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 */
23
24 #ifdef HAVE_DL_ITERATE_PHDR
25 #include <dlfcn.h>
26 #include <link.h>
27 #include <stddef.h>
28 #include <string.h>
29
30 #include "build_id.h"
31
32 #ifndef NT_GNU_BUILD_ID
33 #define NT_GNU_BUILD_ID 3
34 #endif
35
36 #ifndef ElfW
37 #define ElfW(type) Elf_##type
38 #endif
39
40 #define ALIGN(val, align) (((val) + (align) - 1) & ~((align) - 1))
41
42 struct build_id_note {
43 ElfW(Nhdr) nhdr;
44
45 char name[4]; /* Note name for build-id is "GNU\0" */
46 uint8_t build_id[0];
47 };
48
49 struct callback_data {
50 /* Base address of shared object, taken from Dl_info::dli_fbase */
51 const void *dli_fbase;
52
53 struct build_id_note *note;
54 };
55
56 static int
build_id_find_nhdr_callback(struct dl_phdr_info * info,size_t size,void * data_)57 build_id_find_nhdr_callback(struct dl_phdr_info *info, size_t size, void *data_)
58 {
59 struct callback_data *data = data_;
60
61 /* Calculate address where shared object is mapped into the process space.
62 * (Using the base address and the virtual address of the first LOAD segment)
63 */
64 void *map_start = NULL;
65 for (unsigned i = 0; i < info->dlpi_phnum; i++) {
66 if (info->dlpi_phdr[i].p_type == PT_LOAD) {
67 map_start = (void *)(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
68 break;
69 }
70 }
71
72 if (map_start != data->dli_fbase)
73 return 0;
74
75 for (unsigned i = 0; i < info->dlpi_phnum; i++) {
76 if (info->dlpi_phdr[i].p_type != PT_NOTE)
77 continue;
78
79 struct build_id_note *note = (void *)(info->dlpi_addr +
80 info->dlpi_phdr[i].p_vaddr);
81 ptrdiff_t len = info->dlpi_phdr[i].p_filesz;
82
83 while (len >= sizeof(struct build_id_note)) {
84 if (note->nhdr.n_type == NT_GNU_BUILD_ID &&
85 note->nhdr.n_descsz != 0 &&
86 note->nhdr.n_namesz == 4 &&
87 memcmp(note->name, "GNU", 4) == 0) {
88 data->note = note;
89 return 1;
90 }
91
92 size_t offset = sizeof(ElfW(Nhdr)) +
93 ALIGN(note->nhdr.n_namesz, 4) +
94 ALIGN(note->nhdr.n_descsz, 4);
95 note = (struct build_id_note *)((char *)note + offset);
96 len -= offset;
97 }
98 }
99
100 return 0;
101 }
102
103 const struct build_id_note *
build_id_find_nhdr_for_addr(const void * addr)104 build_id_find_nhdr_for_addr(const void *addr)
105 {
106 Dl_info info;
107
108 if (!dladdr(addr, &info))
109 return NULL;
110
111 if (!info.dli_fbase)
112 return NULL;
113
114 struct callback_data data = {
115 .dli_fbase = info.dli_fbase,
116 .note = NULL,
117 };
118
119 if (!dl_iterate_phdr(build_id_find_nhdr_callback, &data))
120 return NULL;
121
122 return data.note;
123 }
124
125 unsigned
build_id_length(const struct build_id_note * note)126 build_id_length(const struct build_id_note *note)
127 {
128 return note->nhdr.n_descsz;
129 }
130
131 const uint8_t *
build_id_data(const struct build_id_note * note)132 build_id_data(const struct build_id_note *note)
133 {
134 return note->build_id;
135 }
136
137 #endif
138