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)
  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
  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
 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 };