1 /*
2 * virmodule.c: APIs for dlopen'ing extension modules
3 *
4 * Copyright (C) 2012-2018 Red Hat, Inc.
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; If not, see
18 * <http://www.gnu.org/licenses/>.
19 *
20 */
21
22 #include <config.h>
23
24 #include "internal.h"
25 #include "virmodule.h"
26 #include "virerror.h"
27 #include "virfile.h"
28 #include "virlog.h"
29 #include "virutil.h"
30
31 #define VIR_FROM_THIS VIR_FROM_NONE
32
33 VIR_LOG_INIT("util.module");
34
35 #ifdef WITH_DLFCN_H
36 # include <dlfcn.h>
37
38 static void *
virModuleLoadFile(const char * file)39 virModuleLoadFile(const char *file)
40 {
41 void *handle = NULL;
42 int flags = RTLD_NOW | RTLD_GLOBAL;
43
44 # ifdef RTLD_NODELETE
45 flags |= RTLD_NODELETE;
46 # endif
47
48 VIR_DEBUG("Load module file '%s'", file);
49
50 virUpdateSelfLastChanged(file);
51
52 if (!(handle = dlopen(file, flags))) {
53 virReportError(VIR_ERR_INTERNAL_ERROR,
54 _("Failed to load module '%s': %s"), file, dlerror());
55 return NULL;
56 }
57
58 return handle;
59 }
60
61
62 static void *
virModuleLoadFunc(void * handle,const char * file,const char * funcname)63 virModuleLoadFunc(void *handle,
64 const char *file,
65 const char *funcname)
66 {
67 void *regsym;
68
69 VIR_DEBUG("Lookup function '%s'", funcname);
70
71 if (!(regsym = dlsym(handle, funcname))) {
72 virReportError(VIR_ERR_INTERNAL_ERROR,
73 _("Failed to find symbol '%s' in module '%s': %s"),
74 funcname, file, dlerror());
75 return NULL;
76 }
77
78 return regsym;
79 }
80
81
82 /**
83 * virModuleLoad:
84 * @path: filename of module to load
85 * @regfunc: name of the function that registers the module
86 * @required: true if module must exist on disk, false to silently skip
87 *
88 * Loads a loadable module named @path and calls the
89 * registration function @regfunc. The module will never
90 * be unloaded because unloading is not safe in a multi-threaded
91 * application.
92 *
93 * The module is automatically looked up in the appropriate place (git or
94 * installed directory).
95 *
96 * Returns 0 on success, 1 if the module was not found and -1 on any error.
97 */
98 int
virModuleLoad(const char * path,const char * regfunc,bool required)99 virModuleLoad(const char *path,
100 const char *regfunc,
101 bool required)
102 {
103 void *rethandle = NULL;
104 int (*regsym)(void);
105 int ret = -1;
106
107 if (!virFileExists(path)) {
108 if (required) {
109 virReportSystemError(errno,
110 _("Failed to find module '%s'"), path);
111 return -1;
112 } else {
113 VIR_INFO("Module '%s' does not exist", path);
114 return 1;
115 }
116 }
117
118 if (!(rethandle = virModuleLoadFile(path)))
119 goto cleanup;
120
121 if (!(regsym = virModuleLoadFunc(rethandle, path, regfunc)))
122 goto cleanup;
123
124 if ((*regsym)() < 0) {
125 /* regsym() should report an error itself, but lets
126 * just make sure */
127 if (virGetLastErrorCode() == VIR_ERR_OK) {
128 virReportError(VIR_ERR_INTERNAL_ERROR,
129 _("Failed to execute symbol '%s' in module '%s'"),
130 regfunc, path);
131 }
132 goto cleanup;
133 }
134
135 rethandle = NULL;
136 ret = 0;
137
138 cleanup:
139 if (rethandle)
140 dlclose(rethandle);
141 return ret;
142 }
143
144 #else /* ! WITH_DLFCN_H */
145 int
virModuleLoad(const char * path,const char * regfunc G_GNUC_UNUSED,bool required)146 virModuleLoad(const char *path,
147 const char *regfunc G_GNUC_UNUSED,
148 bool required)
149 {
150 VIR_DEBUG("dlopen not available on this platform");
151 if (required) {
152 virReportSystemError(ENOSYS,
153 _("Failed to find module '%s'"), path);
154 return -1;
155 } else {
156 /* Since we have no dlopen(), but definition we have no
157 * loadable modules on disk, so we can reasonably
158 * return '1' instead of an error.
159 */
160 return 1;
161 }
162 }
163 #endif /* ! WITH_DLFCN_H */
164