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1 | /* Return error detail for failing <dlfcn.h> functions. | |
2 | Copyright (C) 1995-2024 Free Software Foundation, Inc. | |
3 | This file is part of the GNU C Library. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
17 | <https://www.gnu.org/licenses/>. */ | |
18 | ||
19 | #include <dlfcn.h> | |
20 | #include <libintl.h> | |
21 | #include <stdbool.h> | |
22 | #include <stdio.h> | |
23 | #include <stdlib.h> | |
24 | #include <string.h> | |
25 | #include <libc-lock.h> | |
26 | #include <ldsodefs.h> | |
27 | #include <libc-symbols.h> | |
28 | #include <assert.h> | |
29 | #include <dlerror.h> | |
30 | ||
31 | char * | |
32 | __dlerror (void) | |
33 | { | |
34 | # ifdef SHARED | |
35 | if (GLRO (dl_dlfcn_hook) != NULL) | |
36 | return GLRO (dl_dlfcn_hook)->dlerror (); | |
37 | # endif | |
38 | ||
39 | struct dl_action_result *result = __libc_dlerror_result; | |
40 | ||
41 | /* No libdl function has been called. No error is possible. */ | |
42 | if (result == NULL) | |
43 | return NULL; | |
44 | ||
45 | /* For an early malloc failure, clear the error flag and return the | |
46 | error message. This marks the error as delivered. */ | |
47 | if (result == dl_action_result_malloc_failed) | |
48 | { | |
49 | __libc_dlerror_result = NULL; | |
50 | return (char *) "out of memory"; | |
51 | } | |
52 | ||
53 | /* Placeholder object. This can be observed in a recursive call, | |
54 | e.g. from an ELF constructor. */ | |
55 | if (result->errstring == NULL) | |
56 | return NULL; | |
57 | ||
58 | /* If we have already reported the error, we can free the result and | |
59 | return NULL. See __libc_dlerror_result_free. */ | |
60 | if (result->returned) | |
61 | { | |
62 | __libc_dlerror_result = NULL; | |
63 | dl_action_result_errstring_free (result); | |
64 | free (result); | |
65 | return NULL; | |
66 | } | |
67 | ||
68 | assert (result->errstring != NULL); | |
69 | ||
70 | /* Create the combined error message. */ | |
71 | char *buf; | |
72 | int n; | |
73 | if (result->errcode == 0) | |
74 | n = __asprintf (&buf, "%s%s%s", | |
75 | result->objname, | |
76 | result->objname[0] == '\0' ? "" : ": ", | |
77 | _(result->errstring)); | |
78 | else | |
79 | { | |
80 | __set_errno (result->errcode); | |
81 | n = __asprintf (&buf, "%s%s%s: %m", | |
82 | result->objname, | |
83 | result->objname[0] == '\0' ? "" : ": ", | |
84 | _(result->errstring)); | |
85 | /* Set errno again in case asprintf clobbered it. */ | |
86 | __set_errno (result->errcode); | |
87 | } | |
88 | ||
89 | /* Mark the error as delivered. */ | |
90 | result->returned = true; | |
91 | ||
92 | if (n >= 0) | |
93 | { | |
94 | /* Replace the error string with the newly allocated one. */ | |
95 | dl_action_result_errstring_free (result); | |
96 | result->errstring = buf; | |
97 | result->errstring_source = dl_action_result_errstring_local; | |
98 | return buf; | |
99 | } | |
100 | else | |
101 | /* We could not create the combined error message, so use the | |
102 | existing string as a fallback. */ | |
103 | return result->errstring; | |
104 | } | |
105 | versioned_symbol (libc, __dlerror, dlerror, GLIBC_2_34); | |
106 | ||
107 | #if OTHER_SHLIB_COMPAT (libdl, GLIBC_2_0, GLIBC_2_34) | |
108 | compat_symbol (libdl, __dlerror, dlerror, GLIBC_2_0); | |
109 | #endif | |
110 | ||
111 | int | |
112 | _dlerror_run (void (*operate) (void *), void *args) | |
113 | { | |
114 | struct dl_action_result *result = __libc_dlerror_result; | |
115 | if (result != NULL) | |
116 | { | |
117 | if (result == dl_action_result_malloc_failed) | |
118 | { | |
119 | /* Clear the previous error. */ | |
120 | __libc_dlerror_result = NULL; | |
121 | result = NULL; | |
122 | } | |
123 | else | |
124 | { | |
125 | /* There is an existing object. Free its error string, but | |
126 | keep the object. */ | |
127 | dl_action_result_errstring_free (result); | |
128 | /* Mark the object as not containing an error. This ensures | |
129 | that call to dlerror from, for example, an ELF | |
130 | constructor will not notice this result object. */ | |
131 | result->errstring = NULL; | |
132 | } | |
133 | } | |
134 | ||
135 | const char *objname; | |
136 | const char *errstring; | |
137 | bool malloced; | |
138 | int errcode = GLRO (dl_catch_error) (&objname, &errstring, &malloced, | |
139 | operate, args); | |
140 | ||
141 | /* ELF constructors or destructors may have indirectly altered the | |
142 | value of __libc_dlerror_result, therefore reload it. */ | |
143 | result = __libc_dlerror_result; | |
144 | ||
145 | if (errstring == NULL) | |
146 | { | |
147 | /* There is no error. We no longer need the result object if it | |
148 | does not contain an error. However, a recursive call may | |
149 | have added an error even if this call did not cause it. Keep | |
150 | the other error. */ | |
151 | if (result != NULL && result->errstring == NULL) | |
152 | { | |
153 | __libc_dlerror_result = NULL; | |
154 | free (result); | |
155 | } | |
156 | return 0; | |
157 | } | |
158 | else | |
159 | { | |
160 | /* A new error occurred. Check if a result object has to be | |
161 | allocated. */ | |
162 | if (result == NULL || result == dl_action_result_malloc_failed) | |
163 | { | |
164 | /* Allocating storage for the error message after the fact | |
165 | is not ideal. But this avoids an infinite recursion in | |
166 | case malloc itself calls libdl functions (without | |
167 | triggering errors). */ | |
168 | result = malloc (sizeof (*result)); | |
169 | if (result == NULL) | |
170 | { | |
171 | /* Assume that the dlfcn failure was due to a malloc | |
172 | failure, too. */ | |
173 | if (malloced) | |
174 | dl_error_free ((char *) errstring); | |
175 | __libc_dlerror_result = dl_action_result_malloc_failed; | |
176 | return 1; | |
177 | } | |
178 | __libc_dlerror_result = result; | |
179 | } | |
180 | else | |
181 | /* Deallocate the existing error message from a recursive | |
182 | call, but reuse the result object. */ | |
183 | dl_action_result_errstring_free (result); | |
184 | ||
185 | result->errcode = errcode; | |
186 | result->objname = objname; | |
187 | result->errstring = (char *) errstring; | |
188 | result->returned = false; | |
189 | /* In case of an error, the malloced flag indicates whether the | |
190 | error string is constant or not. */ | |
191 | if (malloced) | |
192 | result->errstring_source = dl_action_result_errstring_rtld; | |
193 | else | |
194 | result->errstring_source = dl_action_result_errstring_constant; | |
195 | ||
196 | return 1; | |
197 | } | |
198 | } |