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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
     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 };
    167