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1 /*
2  * Copyright © 2013 Intel Corporation
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a
5  * copy of this software and associated documentation files (the "Software"),
6  * to deal in the Software without restriction, including without limitation
7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8  * and/or sell copies of the Software, and to permit persons to whom the
9  * Software is furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice (including the next
12  * paragraph) shall be included in all copies or substantial portions of the
13  * Software.
14  *
15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21  * IN THE SOFTWARE.
22  */
23 
24 #include <stdio.h>
25 #include "dri_util.h"
26 #include <dlfcn.h>
27 #include "main/macros.h"
28 
29 /* We need GNU extensions to dlfcn.h in order to provide backward
30  * compatibility for the older DRI driver loader mechanism. (dladdr,
31  * Dl_info, and RTLD_DEFAULT)
32  */
33 #if defined(RTLD_DEFAULT) && defined(HAVE_DLADDR)
34 
35 #define MEGADRIVER_STUB_MAX_EXTENSIONS 10
36 #define LIB_PATH_SUFFIX "_dri.so"
37 #define LIB_PATH_SUFFIX_LENGTH (sizeof(LIB_PATH_SUFFIX)-1)
38 
39 /* This is the table of extensions that the loader will dlsym() for.
40  *
41  * Initially it is empty for the megadriver stub, but the library
42  * constructor may initialize it based on the name of the library that
43  * is being loaded.
44  */
45 PUBLIC const __DRIextension *
46 __driDriverExtensions[MEGADRIVER_STUB_MAX_EXTENSIONS] = {
47    NULL
48 };
49 
50 /**
51  * This is a constructor function for the megadriver dynamic library.
52  *
53  * When the driver is dlopen'ed, this function will run. It will
54  * search for the name of the foo_dri.so file that was opened using
55  * the dladdr function.
56  *
57  * After finding foo's name, it will call __driDriverGetExtensions_foo
58  * and use the return to update __driDriverExtensions to enable
59  * compatibility with older DRI driver loaders.
60  */
61 __attribute__((constructor)) static void
megadriver_stub_init(void)62 megadriver_stub_init(void)
63 {
64    Dl_info info;
65    char *driver_name;
66    size_t name_len;
67    char *get_extensions_name;
68    const __DRIextension **(*get_extensions)(void);
69    const __DRIextension **extensions;
70    int i;
71 
72    /* Call dladdr on __driDriverExtensions. We are really
73     * interested in the returned info.dli_fname so we can
74     * figure out the path name of the library being loaded.
75     */
76    i = dladdr((void*) __driDriverExtensions, &info);
77    if (i == 0)
78       return;
79 
80    /* Search for the last '/' character in the path. */
81    driver_name = strrchr(info.dli_fname, '/');
82    if (driver_name != NULL) {
83       /* Skip '/' character */
84       driver_name++;
85    } else {
86       /* Try using the start of the path */
87       driver_name = (char*) info.dli_fname;
88    }
89 
90    /* Make sure the path ends with _dri.so */
91    name_len = strlen(driver_name);
92    i = name_len - LIB_PATH_SUFFIX_LENGTH;
93    if (i < 0 || strcmp(driver_name + i, LIB_PATH_SUFFIX) != 0)
94       return;
95 
96    /* Duplicate the string so we can modify it.
97     * So far we've been using info.dli_fname.
98     */
99    driver_name = strdup(driver_name);
100    if (!driver_name)
101       return;
102 
103    /* The path ends with _dri.so. Chop this part of the
104     * string off. Then we'll have the driver's final name.
105     */
106    driver_name[i] = '\0';
107 
108    i = asprintf(&get_extensions_name, "%s_%s",
109                 __DRI_DRIVER_GET_EXTENSIONS, driver_name);
110    free(driver_name);
111    if (i == -1)
112       return;
113 
114    /* dlsym to get the driver's get extensions function. We
115     * don't have the dlopen handle, so we have to use
116     * RTLD_DEFAULT. It seems unlikely that the symbol will
117     * be found in another library, but this isn't optimal.
118     */
119    get_extensions = dlsym(RTLD_DEFAULT, get_extensions_name);
120    free(get_extensions_name);
121    if (!get_extensions)
122       return;
123 
124    /* Use the newer DRI loader entrypoint to find extensions.
125     * We will then expose these extensions via the older
126     * __driDriverExtensions symbol.
127     */
128    extensions = get_extensions();
129 
130    /* Copy the extensions into the __driDriverExtensions array
131     * we declared.
132     */
133    for (i = 0; i < ARRAY_SIZE(__driDriverExtensions); i++) {
134       __driDriverExtensions[i] = extensions[i];
135       if (extensions[i] == NULL)
136          break;
137    }
138 
139    /* If the driver had more extensions than we reserved, then
140     * bail out.
141     */
142    if (i == ARRAY_SIZE(__driDriverExtensions)) {
143       __driDriverExtensions[0] = NULL;
144       fprintf(stderr, "Megadriver stub did not reserve enough extension "
145               "slots.\n");
146       return;
147    }
148 }
149 
150 #endif /* RTLD_DEFAULT && HAVE_DLADDR */
151 
152 static const
stub_error_init_screen(__DRIscreen * psp)153 __DRIconfig **stub_error_init_screen(__DRIscreen *psp)
154 {
155    fprintf(stderr, "An updated DRI driver loader (libGL.so or X Server) is "
156            "required for this Mesa driver.\n");
157    return NULL;
158 }
159 
160 /**
161  * This is a stub driDriverAPI that is referenced by dri_util.c but should
162  * never be used.
163  */
164 const struct __DriverAPIRec driDriverAPI = {
165    .InitScreen = stub_error_init_screen,
166 };
167