Line data Source code
1 : /* Retrieves the DWARF descriptor for debugaltlink data.
2 : Copyright (C) 2014, 2018 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 "libdwP.h"
34 : #include "libelfP.h"
35 : #include "libdwelfP.h"
36 : #include "system.h"
37 :
38 : #include <inttypes.h>
39 : #include <fcntl.h>
40 : #include <limits.h>
41 : #include <stdlib.h>
42 : #include <stdio.h>
43 : #include <string.h>
44 : #include <sys/types.h>
45 : #include <sys/stat.h>
46 :
47 :
48 : char *
49 : internal_function
50 52 : __libdw_filepath (const char *debugdir, const char *dir, const char *file)
51 : {
52 52 : if (file == NULL)
53 : return NULL;
54 :
55 52 : if (file[0] == '/')
56 0 : return strdup (file);
57 :
58 52 : if (dir != NULL && dir[0] == '/')
59 : {
60 1 : size_t dirlen = strlen (dir);
61 1 : size_t filelen = strlen (file);
62 1 : size_t len = dirlen + 1 + filelen + 1;
63 1 : char *path = malloc (len);
64 1 : if (path != NULL)
65 : {
66 1 : char *c = mempcpy (path, dir, dirlen);
67 1 : if (dir[dirlen - 1] != '/')
68 1 : *c++ = '/';
69 1 : mempcpy (c, file, filelen + 1);
70 : }
71 1 : return path;
72 : }
73 :
74 51 : if (debugdir != NULL)
75 : {
76 51 : size_t debugdirlen = strlen (debugdir);
77 51 : size_t dirlen = dir != NULL ? strlen (dir) : 0;
78 51 : size_t filelen = strlen (file);
79 51 : size_t len = debugdirlen + 1 + dirlen + 1 + filelen + 1;
80 51 : char *path = malloc (len);
81 51 : if (path != NULL)
82 : {
83 51 : char *c = mempcpy (path, debugdir, debugdirlen);
84 51 : if (dirlen > 0)
85 : {
86 0 : c = mempcpy (c, dir, dirlen);
87 0 : if (dir[dirlen - 1] != '/')
88 0 : *c++ = '/';
89 : }
90 51 : mempcpy (c, file, filelen + 1);
91 51 : return path;
92 : }
93 : }
94 :
95 : return NULL;
96 : }
97 :
98 : static void
99 23 : find_debug_altlink (Dwarf *dbg)
100 : {
101 : const char *altname;
102 : const void *build_id;
103 23 : ssize_t build_id_len = INTUSE(dwelf_dwarf_gnu_debugaltlink) (dbg,
104 : &altname,
105 : &build_id);
106 :
107 : /* Couldn't even get the debugaltlink. It probably doesn't exist. */
108 23 : if (build_id_len <= 0)
109 21 : return;
110 :
111 2 : const uint8_t *id = (const uint8_t *) build_id;
112 2 : size_t id_len = build_id_len;
113 2 : int fd = -1;
114 :
115 : /* We only look in the standard path. And relative to the dbg file. */
116 : #define DEBUGINFO_PATH "/usr/lib/debug"
117 :
118 : /* We don't handle very short or really large build-ids. We need at
119 : at least 3 and allow for up to 64 (normally ids are 20 long). */
120 : #define MIN_BUILD_ID_BYTES 3
121 : #define MAX_BUILD_ID_BYTES 64
122 2 : if (id_len >= MIN_BUILD_ID_BYTES && id_len <= MAX_BUILD_ID_BYTES)
123 : {
124 : /* Note sizeof a string literal includes the trailing zero. */
125 : char id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
126 : + 2 + 1 + (MAX_BUILD_ID_BYTES - 1) * 2 + sizeof ".debug"];
127 : sprintf (&id_path[0], "%s%s", DEBUGINFO_PATH, "/.build-id/");
128 2 : sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1],
129 2 : "%02" PRIx8 "/", (uint8_t) id[0]);
130 40 : for (size_t i = 1; i < id_len; ++i)
131 76 : sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
132 76 : + 3 + (i - 1) * 2], "%02" PRIx8, (uint8_t) id[i]);
133 2 : strcpy (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
134 2 : + 3 + (id_len - 1) * 2], ".debug");
135 :
136 2 : fd = TEMP_FAILURE_RETRY (open (id_path, O_RDONLY));
137 : }
138 :
139 : /* Fall back on (possible relative) alt file path. */
140 2 : if (fd < 0)
141 : {
142 2 : char *altpath = __libdw_filepath (dbg->debugdir, NULL, altname);
143 2 : if (altpath != NULL)
144 : {
145 2 : fd = TEMP_FAILURE_RETRY (open (altpath, O_RDONLY));
146 2 : free (altpath);
147 : }
148 : }
149 :
150 2 : if (fd >= 0)
151 : {
152 2 : Dwarf *alt = dwarf_begin (fd, O_RDONLY);
153 2 : if (alt != NULL)
154 : {
155 2 : dbg->alt_dwarf = alt;
156 2 : dbg->alt_fd = fd;
157 : }
158 : else
159 0 : close (fd);
160 : }
161 : }
162 :
163 : Dwarf *
164 1047 : dwarf_getalt (Dwarf *main)
165 : {
166 : /* Only try once. */
167 1047 : if (main == NULL || main->alt_dwarf == (void *) -1)
168 : return NULL;
169 :
170 899 : if (main->alt_dwarf != NULL)
171 : return main->alt_dwarf;
172 :
173 23 : find_debug_altlink (main);
174 :
175 : /* If we found nothing, make sure we don't try again. */
176 23 : if (main->alt_dwarf == NULL)
177 : {
178 21 : main->alt_dwarf = (void *) -1;
179 21 : return NULL;
180 : }
181 :
182 : return main->alt_dwarf;
183 : }
184 : INTDEF (dwarf_getalt)
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