Line data Source code
1 : /* Find an ELF file for a module from its build ID.
2 : Copyright (C) 2007-2010, 2014, 2015 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 "libdwflP.h"
34 : #include <inttypes.h>
35 : #include <fcntl.h>
36 : #include <unistd.h>
37 : #include "system.h"
38 :
39 :
40 : int
41 : internal_function
42 107 : __libdwfl_open_by_build_id (Dwfl_Module *mod, bool debug, char **file_name,
43 : const size_t id_len, const uint8_t *id)
44 : {
45 : /* We don't handle very short or really large build-ids. We need at
46 : at least 3 and allow for up to 64 (normally ids are 20 long). */
47 : #define MIN_BUILD_ID_BYTES 3
48 : #define MAX_BUILD_ID_BYTES 64
49 107 : if (id_len < MIN_BUILD_ID_BYTES || id_len > MAX_BUILD_ID_BYTES)
50 : {
51 0 : __libdwfl_seterrno (DWFL_E_WRONG_ID_ELF);
52 0 : return -1;
53 : }
54 :
55 : /* Search debuginfo_path directories' .build-id/ subdirectories. */
56 :
57 : char id_name[sizeof "/.build-id/" + 1 + MAX_BUILD_ID_BYTES * 2
58 : + sizeof ".debug" - 1];
59 : strcpy (id_name, "/.build-id/");
60 214 : int n = snprintf (&id_name[sizeof "/.build-id/" - 1],
61 107 : 4, "%02" PRIx8 "/", (uint8_t) id[0]);
62 107 : assert (n == 3);
63 2033 : for (size_t i = 1; i < id_len; ++i)
64 : {
65 4066 : n = snprintf (&id_name[sizeof "/.build-id/" - 1 + 3 + (i - 1) * 2],
66 2033 : 3, "%02" PRIx8, (uint8_t) id[i]);
67 2033 : assert (n == 2);
68 : }
69 107 : if (debug)
70 93 : strcpy (&id_name[sizeof "/.build-id/" - 1 + 3 + (id_len - 1) * 2],
71 : ".debug");
72 :
73 107 : const Dwfl_Callbacks *const cb = mod->dwfl->callbacks;
74 107 : char *path = strdup ((cb->debuginfo_path ? *cb->debuginfo_path : NULL)
75 : ?: DEFAULT_DEBUGINFO_PATH);
76 107 : if (path == NULL)
77 : return -1;
78 :
79 : int fd = -1;
80 : char *dir;
81 : char *paths = path;
82 843 : while (fd < 0 && (dir = strsep (&paths, ":")) != NULL)
83 : {
84 319 : if (dir[0] == '+' || dir[0] == '-')
85 0 : ++dir;
86 :
87 : /* Only absolute directory names are useful to us. */
88 319 : if (dir[0] != '/')
89 212 : continue;
90 :
91 107 : size_t dirlen = strlen (dir);
92 107 : char *name = malloc (dirlen + sizeof id_name);
93 107 : if (unlikely (name == NULL))
94 : break;
95 107 : memcpy (mempcpy (name, dir, dirlen), id_name, sizeof id_name);
96 :
97 107 : fd = TEMP_FAILURE_RETRY (open (name, O_RDONLY));
98 107 : if (fd >= 0)
99 : {
100 9 : if (*file_name != NULL)
101 0 : free (*file_name);
102 9 : *file_name = realpath (name, NULL);
103 9 : if (*file_name == NULL)
104 : {
105 0 : *file_name = name;
106 0 : name = NULL;
107 : }
108 : }
109 107 : free (name);
110 : }
111 :
112 107 : free (path);
113 :
114 : /* If we simply found nothing, clear errno. If we had some other error
115 : with the file, report that. Possibly this should treat other errors
116 : like ENOENT too. But ignoring all errors could mask some that should
117 : be reported. */
118 107 : if (fd < 0 && errno == ENOENT)
119 98 : errno = 0;
120 :
121 107 : return fd;
122 : }
123 :
124 : int
125 : internal_function
126 101 : __libdwfl_open_mod_by_build_id (Dwfl_Module *mod, bool debug, char **file_name)
127 : {
128 : /* If *FILE_NAME was primed into the module, leave it there
129 : as the fallback when we have nothing to offer. */
130 101 : errno = 0;
131 101 : if (mod->build_id_len <= 0)
132 : return -1;
133 :
134 101 : const size_t id_len = mod->build_id_len;
135 101 : const uint8_t *id = mod->build_id_bits;
136 :
137 101 : return __libdwfl_open_by_build_id (mod, debug, file_name, id_len, id);
138 : }
139 :
140 : int
141 26 : dwfl_build_id_find_elf (Dwfl_Module *mod,
142 : void **userdata __attribute__ ((unused)),
143 : const char *modname __attribute__ ((unused)),
144 : Dwarf_Addr base __attribute__ ((unused)),
145 : char **file_name, Elf **elfp)
146 : {
147 26 : *elfp = NULL;
148 26 : if (mod->is_executable
149 12 : && mod->dwfl->user_core != NULL
150 12 : && mod->dwfl->user_core->executable_for_core != NULL)
151 : {
152 : /* When dwfl_core_file_report was called with a non-NULL executable file
153 : name this callback will replace the Dwfl_Module main.name with the
154 : recorded executable file when MOD was identified as main executable
155 : (which then triggers opening and reporting of the executable). */
156 12 : const char *executable = mod->dwfl->user_core->executable_for_core;
157 12 : int fd = open (executable, O_RDONLY);
158 12 : if (fd >= 0)
159 : {
160 12 : *file_name = strdup (executable);
161 12 : if (*file_name != NULL)
162 : return fd;
163 : else
164 0 : close (fd);
165 : }
166 : }
167 14 : int fd = __libdwfl_open_mod_by_build_id (mod, false, file_name);
168 14 : if (fd >= 0)
169 : {
170 0 : Dwfl_Error error = __libdw_open_file (&fd, elfp, true, false);
171 0 : if (error != DWFL_E_NOERROR)
172 0 : __libdwfl_seterrno (error);
173 0 : else if (__libdwfl_find_build_id (mod, false, *elfp) == 2)
174 : {
175 : /* This is a backdoor signal to short-circuit the ID refresh. */
176 0 : mod->main.valid = true;
177 0 : return fd;
178 : }
179 : else
180 : {
181 : /* This file does not contain the ID it should! */
182 0 : elf_end (*elfp);
183 0 : *elfp = NULL;
184 0 : close (fd);
185 0 : fd = -1;
186 : }
187 0 : free (*file_name);
188 0 : *file_name = NULL;
189 : }
190 14 : else if (errno == 0 && mod->build_id_len > 0)
191 : /* Setting this with no file yet loaded is a marker that
192 : the build ID is authoritative even if we also know a
193 : putative *FILE_NAME. */
194 14 : mod->main.valid = true;
195 :
196 14 : return fd;
197 : }
198 : INTDEF (dwfl_build_id_find_elf)
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