Home | History | Annotate | Download | only in ppapi_stub 
      1 /*
      2  * Copyright (c) 2014 The Chromium Authors. All rights reserved.
      3  * Use of this source code is governed by a BSD-style license that can be
      4  * found in the LICENSE file.
      5  */
      6 
      7 #include <pthread.h>
      8 
      9 #include "irt_syscalls.h"
     10 #include "ppapi/c/pp_module.h"
     11 #include "ppapi/c/ppp.h"
     12 
     13 struct PP_StartFunctions {
     14   int32_t (*PPP_InitializeModule)(PP_Module module_id,
     15                                   PPB_GetInterface get_browser_interface);
     16   void (*PPP_ShutdownModule)();
     17   const void* (*PPP_GetInterface)(const char* interface_name);
     18 };
     19 
     20 struct PP_ThreadFunctions {
     21   /*
     22    * This is a cut-down version of pthread_create()/pthread_join().
     23    * We omit thread creation attributes and the thread's return value.
     24    *
     25    * We use uintptr_t as the thread ID type because pthread_t is not
     26    * part of the stable ABI; a user thread library might choose an
     27    * arbitrary size for its own pthread_t.
     28    */
     29   int (*thread_create)(uintptr_t* tid,
     30                        void (*func)(void* thread_argument),
     31                        void* thread_argument);
     32   int (*thread_join)(uintptr_t tid);
     33 };
     34 
     35 #define NACL_IRT_PPAPIHOOK_v0_1 "nacl-irt-ppapihook-0.1"
     36 struct nacl_irt_ppapihook {
     37   int (*ppapi_start)(const struct PP_StartFunctions*);
     38   void (*ppapi_register_thread_creator)(const struct PP_ThreadFunctions*);
     39 };
     40 
     41 
     42 static int thread_create(uintptr_t *tid,
     43                          void (*func)(void *thread_argument),
     44                          void *thread_argument) {
     45   /*
     46    * We know that newlib and glibc use a small pthread_t type, so we
     47    * do not need to wrap pthread_t values.
     48    */
     49   return pthread_create((pthread_t *) tid, NULL,
     50                         (void *(*)(void *thread_argument)) func,
     51                         thread_argument);
     52 }
     53 
     54 static int thread_join(uintptr_t tid) {
     55   return pthread_join((pthread_t) tid, NULL);
     56 }
     57 
     58 /*
     59  * These are dangling references to functions that the application must define.
     60  */
     61 static const struct PP_StartFunctions ppapi_app_start_callbacks = {
     62   PPP_InitializeModule,
     63   PPP_ShutdownModule,
     64   PPP_GetInterface
     65 };
     66 
     67 const static struct PP_ThreadFunctions thread_funcs = {
     68   thread_create,
     69   thread_join
     70 };
     71 
     72 static void fatal_error(const char *message) {
     73   write(2, message, strlen(message));
     74   _exit(127);
     75 }
     76 
     77 /*
     78  * We cannot tell at link time whether the application uses PPB_Audio,
     79  * because of the way that PPAPI is defined via runtime interface
     80  * query rather than a set of static functions.  This means that we
     81  * register the audio thread functions unconditionally.  This adds the
     82  * small overhead of pulling in pthread_create() even if the
     83  * application does not use PPB_Audio or libpthread.
     84  *
     85  * If an application developer wants to avoid that cost, they can
     86  * override this function with an empty definition.
     87  */
     88 void __nacl_register_thread_creator(const struct nacl_irt_ppapihook *hooks) {
     89   hooks->ppapi_register_thread_creator(&thread_funcs);
     90 }
     91 
     92 int PpapiPluginStart(const struct PP_StartFunctions *funcs) {
     93   struct nacl_irt_ppapihook hooks;
     94   if (sizeof(hooks) != __nacl_irt_query(NACL_IRT_PPAPIHOOK_v0_1,
     95                                         &hooks, sizeof(hooks))) {
     96     fatal_error("PpapiPluginStart: PPAPI hooks not found\n");
     97   }
     98 
     99   __nacl_register_thread_creator(&hooks);
    100   return hooks.ppapi_start(funcs);
    101 }
    102 
    103 
    104 /*
    105  * The application's main (or the one supplied in this library) calls this
    106  * to start the PPAPI world.
    107  */
    108 int PpapiPluginMain(void) {
    109   return PpapiPluginStart(&ppapi_app_start_callbacks);
    110 }
    111