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
__libdw_filepath(const char * debugdir,const char * dir,const char * file)50 __libdw_filepath (const char *debugdir, const char *dir, const char *file)
51 {
52 if (file == NULL)
53 return NULL;
54
55 if (file[0] == '/')
56 return strdup (file);
57
58 if (dir != NULL && dir[0] == '/')
59 {
60 size_t dirlen = strlen (dir);
61 size_t filelen = strlen (file);
62 size_t len = dirlen + 1 + filelen + 1;
63 char *path = malloc (len);
64 if (path != NULL)
65 {
66 char *c = mempcpy (path, dir, dirlen);
67 if (dir[dirlen - 1] != '/')
68 *c++ = '/';
69 mempcpy (c, file, filelen + 1);
70 }
71 return path;
72 }
73
74 if (debugdir != NULL)
75 {
76 size_t debugdirlen = strlen (debugdir);
77 size_t dirlen = dir != NULL ? strlen (dir) : 0;
78 size_t filelen = strlen (file);
79 size_t len = debugdirlen + 1 + dirlen + 1 + filelen + 1;
80 char *path = malloc (len);
81 if (path != NULL)
82 {
83 char *c = mempcpy (path, debugdir, debugdirlen);
84 if (dirlen > 0)
85 {
86 c = mempcpy (c, dir, dirlen);
87 if (dir[dirlen - 1] != '/')
88 *c++ = '/';
89 }
90 mempcpy (c, file, filelen + 1);
91 return path;
92 }
93 }
94
95 return NULL;
96 }
97
98 static void
find_debug_altlink(Dwarf * dbg)99 find_debug_altlink (Dwarf *dbg)
100 {
101 const char *altname;
102 const void *build_id;
103 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 if (build_id_len <= 0)
109 return;
110
111 const uint8_t *id = (const uint8_t *) build_id;
112 size_t id_len = build_id_len;
113 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 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 sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1],
129 "%02" PRIx8 "/", (uint8_t) id[0]);
130 for (size_t i = 1; i < id_len; ++i)
131 sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
132 + 3 + (i - 1) * 2], "%02" PRIx8, (uint8_t) id[i]);
133 strcpy (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
134 + 3 + (id_len - 1) * 2], ".debug");
135
136 fd = TEMP_FAILURE_RETRY (open (id_path, O_RDONLY));
137 }
138
139 /* Fall back on (possible relative) alt file path. */
140 if (fd < 0)
141 {
142 char *altpath = __libdw_filepath (dbg->debugdir, NULL, altname);
143 if (altpath != NULL)
144 {
145 fd = TEMP_FAILURE_RETRY (open (altpath, O_RDONLY));
146 free (altpath);
147 }
148 }
149
150 if (fd >= 0)
151 {
152 Dwarf *alt = dwarf_begin (fd, O_RDONLY);
153 if (alt != NULL)
154 {
155 dbg->alt_dwarf = alt;
156 dbg->alt_fd = fd;
157 }
158 else
159 close (fd);
160 }
161 }
162
163 Dwarf *
dwarf_getalt(Dwarf * main)164 dwarf_getalt (Dwarf *main)
165 {
166 /* Only try once. */
167 if (main == NULL || main->alt_dwarf == (void *) -1)
168 return NULL;
169
170 if (main->alt_dwarf != NULL)
171 return main->alt_dwarf;
172
173 find_debug_altlink (main);
174
175 /* If we found nothing, make sure we don't try again. */
176 if (main->alt_dwarf == NULL)
177 {
178 main->alt_dwarf = (void *) -1;
179 return NULL;
180 }
181
182 return main->alt_dwarf;
183 }
184 INTDEF (dwarf_getalt)
185