src/mesa/drivers/dri/common/megadriver_stub.c

   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 are only defined when _GNU_SOURCE is
  32  * defined.)
  33  */
  34 #ifdef _GNU_SOURCE
  35
  36 #define MEGADRIVER_STUB_MAX_EXTENSIONS 10
  37 #define LIB_PATH_SUFFIX "_dri.so"
  38 #define LIB_PATH_SUFFIX_LENGTH (sizeof(LIB_PATH_SUFFIX)-1)
  39
  40 /* This is the table of extensions that the loader will dlsym() for.
  41  *
  42  * Initially it is empty for the megadriver stub, but the library
  43  * constructor may initialize it based on the name of the library that
  44  * is being loaded.
  45  */
  46 PUBLIC const __DRIextension *
  47 __driDriverExtensions[MEGADRIVER_STUB_MAX_EXTENSIONS] = {
  48    NULL
  49 };
  50
  51 /**
  52  * This is a constructor function for the megadriver dynamic library.
  53  *
  54  * When the driver is dlopen'ed, this function will run. It will
  55  * search for the name of the foo_dri.so file that was opened using
  56  * the dladdr function.
  57  *
  58  * After finding foo's name, it will call __driDriverGetExtensions_foo
  59  * and use the return to update __driDriverExtensions to enable
  60  * compatibility with older DRI driver loaders.
  61  */
  62 __attribute__((constructor)) static void
  63 megadriver_stub_init(void)
  64 {
  65    Dl_info info;
  66    char *driver_name;
  67    size_t name_len;
  68    char *get_extensions_name;
  69    const __DRIextension **(*get_extensions)(void);
  70    const __DRIextension **extensions;
  71    int i;
  72
  73    /* Call dladdr on __driDriverExtensions. We are really
  74     * interested in the returned info.dli_fname so we can
  75     * figure out the path name of the library being loaded.
  76     */
  77    i = dladdr((void*) __driDriverExtensions, &info);
  78    if (i == 0)
  79       return;
  80
  81    /* Search for the last '/' character in the path. */
  82    driver_name = strrchr(info.dli_fname, '/');
  83    if (driver_name != NULL) {
  84       /* Skip '/' character */
  85       driver_name++;
  86    } else {
  87       /* Try using the start of the path */
  88       driver_name = (char*) info.dli_fname;
  89    }
  90
  91    /* Make sure the path ends with _dri.so */
  92    name_len = strlen(driver_name);
  93    i = name_len - LIB_PATH_SUFFIX_LENGTH;
  94    if (i < 0 || strcmp(driver_name + i, LIB_PATH_SUFFIX) != 0)
  95       return;
  96
  97    /* Duplicate the string so we can modify it.
  98     * So far we've been using info.dli_fname.
  99     */
 100    driver_name = strdup(driver_name);
 101    if (!driver_name)
 102       return;
 103
 104    /* The path ends with _dri.so. Chop this part of the
 105     * string off. Then we'll have the driver's final name.
 106     */
 107    driver_name[i] = '\0';
 108
 109    i = asprintf(&get_extensions_name, "%s_%s",
 110                 __DRI_DRIVER_GET_EXTENSIONS, driver_name);
 111    free(driver_name);
 112    if (i == -1)
 113       return;
 114
 115    /* dlsym to get the driver's get extensions function. We
 116     * don't have the dlopen handle, so we have to use
 117     * RTLD_DEFAULT. It seems unlikely that the symbol will
 118     * be found in another library, but this isn't optimal.
 119     */
 120    get_extensions = dlsym(RTLD_DEFAULT, get_extensions_name);
 121    free(get_extensions_name);
 122    if (!get_extensions)
 123       return;
 124
 125    /* Use the newer DRI loader entrypoint to find extensions.
 126     * We will then expose these extensions via the older
 127     * __driDriverExtensions symbol.
 128     */
 129    extensions = get_extensions();
 130
 131    /* Copy the extensions into the __driDriverExtensions array
 132     * we declared.
 133     */
 134    for (i = 0; i < ARRAY_SIZE(__driDriverExtensions); i++) {
 135       __driDriverExtensions[i] = extensions[i];
 136       if (extensions[i] == NULL)
 137          break;
 138    }
 139
 140    /* If the driver had more extensions than we reserved, then
 141     * bail out.
 142     */
 143    if (i == ARRAY_SIZE(__driDriverExtensions)) {
 144       __driDriverExtensions[0] = NULL;
 145       fprintf(stderr, "Megadriver stub did not reserve enough extension "
 146               "slots.\n");
 147       return;
 148    }
 149 }
 150
 151 #endif /* _GNU_SOURCE */
 152
 153 static const
 154 __DRIconfig **stub_error_init_screen(__DRIscreen *psp)
 155 {
 156    fprintf(stderr, "An updated DRI driver loader (libGL.so or X Server) is "
 157            "required for this Mesa driver.\n");
 158    return NULL;
 159 }
 160
 161 /**
 162  * This is a stub driDriverAPI that is referenced by dri_util.c but should
 163  * never be used.
 164  */
 165 const struct __DriverAPIRec driDriverAPI = {
 166    .InitScreen = stub_error_init_screen,
 167 };