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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include <hardware/hardware.h>
     18 
     19 #include <cutils/properties.h>
     20 
     21 #include <dlfcn.h>
     22 #include <string.h>
     23 #include <pthread.h>
     24 #include <errno.h>
     25 #include <limits.h>
     26 
     27 #define LOG_TAG "HAL"
     28 #include <utils/Log.h>
     29 
     30 /** Base path of the hal modules */
     31 #define HAL_LIBRARY_PATH1 "/system/lib/hw"
     32 #define HAL_LIBRARY_PATH2 "/vendor/lib/hw"
     33 
     34 /**
     35  * There are a set of variant filename for modules. The form of the filename
     36  * is "<MODULE_ID>.variant.so" so for the led module the Dream variants
     37  * of base "ro.product.board", "ro.board.platform" and "ro.arch" would be:
     38  *
     39  * led.trout.so
     40  * led.msm7k.so
     41  * led.ARMV6.so
     42  * led.default.so
     43  */
     44 
     45 static const char *variant_keys[] = {
     46     "ro.hardware",  /* This goes first so that it can pick up a different
     47                        file on the emulator. */
     48     "ro.product.board",
     49     "ro.board.platform",
     50     "ro.arch"
     51 };
     52 
     53 static const int HAL_VARIANT_KEYS_COUNT =
     54     (sizeof(variant_keys)/sizeof(variant_keys[0]));
     55 
     56 /**
     57  * Load the file defined by the variant and if successful
     58  * return the dlopen handle and the hmi.
     59  * @return 0 = success, !0 = failure.
     60  */
     61 static int load(const char *id,
     62         const char *path,
     63         const struct hw_module_t **pHmi)
     64 {
     65     int status;
     66     void *handle;
     67     struct hw_module_t *hmi;
     68 
     69     /*
     70      * load the symbols resolving undefined symbols before
     71      * dlopen returns. Since RTLD_GLOBAL is not or'd in with
     72      * RTLD_NOW the external symbols will not be global
     73      */
     74     handle = dlopen(path, RTLD_NOW);
     75     if (handle == NULL) {
     76         char const *err_str = dlerror();
     77         LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
     78         status = -EINVAL;
     79         goto done;
     80     }
     81 
     82     /* Get the address of the struct hal_module_info. */
     83     const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
     84     hmi = (struct hw_module_t *)dlsym(handle, sym);
     85     if (hmi == NULL) {
     86         LOGE("load: couldn't find symbol %s", sym);
     87         status = -EINVAL;
     88         goto done;
     89     }
     90 
     91     /* Check that the id matches */
     92     if (strcmp(id, hmi->id) != 0) {
     93         LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
     94         status = -EINVAL;
     95         goto done;
     96     }
     97 
     98     hmi->dso = handle;
     99 
    100     /* success */
    101     status = 0;
    102 
    103     done:
    104     if (status != 0) {
    105         hmi = NULL;
    106         if (handle != NULL) {
    107             dlclose(handle);
    108             handle = NULL;
    109         }
    110     } else {
    111         LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
    112                 id, path, *pHmi, handle);
    113     }
    114 
    115     *pHmi = hmi;
    116 
    117     return status;
    118 }
    119 
    120 int hw_get_module(const char *id, const struct hw_module_t **module)
    121 {
    122     int status;
    123     int i;
    124     const struct hw_module_t *hmi = NULL;
    125     char prop[PATH_MAX];
    126     char path[PATH_MAX];
    127 
    128     /*
    129      * Here we rely on the fact that calling dlopen multiple times on
    130      * the same .so will simply increment a refcount (and not load
    131      * a new copy of the library).
    132      * We also assume that dlopen() is thread-safe.
    133      */
    134 
    135     /* Loop through the configuration variants looking for a module */
    136     for (i=0 ; i<HAL_VARIANT_KEYS_COUNT+1 ; i++) {
    137         if (i < HAL_VARIANT_KEYS_COUNT) {
    138             if (property_get(variant_keys[i], prop, NULL) == 0) {
    139                 continue;
    140             }
    141             snprintf(path, sizeof(path), "%s/%s.%s.so",
    142                     HAL_LIBRARY_PATH1, id, prop);
    143             if (access(path, R_OK) == 0) break;
    144 
    145             snprintf(path, sizeof(path), "%s/%s.%s.so",
    146                      HAL_LIBRARY_PATH2, id, prop);
    147             if (access(path, R_OK) == 0) break;
    148         } else {
    149             snprintf(path, sizeof(path), "%s/%s.default.so",
    150                      HAL_LIBRARY_PATH1, id);
    151             if (access(path, R_OK) == 0) break;
    152         }
    153     }
    154 
    155     status = -ENOENT;
    156     if (i < HAL_VARIANT_KEYS_COUNT+1) {
    157         /* load the module, if this fails, we're doomed, and we should not try
    158          * to load a different variant. */
    159         status = load(id, path, module);
    160     }
    161 
    162     return status;
    163 }
    164