service_runtime/nacl_app_thread.h

   1 /*
   2  * Copyright 2008, Google Inc.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *
   9  *     * Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *     * Redistributions in binary form must reproduce the above
  12  * copyright notice, this list of conditions and the following disclaimer
  13  * in the documentation and/or other materials provided with the
  14  * distribution.
  15  *     * Neither the name of Google Inc. nor the names of its
  16  * contributors may be used to endorse or promote products derived from
  17  * this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  22  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  23  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * NaCl Server Runtime user thread state.
  34  */
  35
  36 #ifndef NATIVE_CLIENT_SERVICE_RUNTIME_NACL_APP_THREAD_H__
  37 #define NATIVE_CLIENT_SERVICE_RUNTIME_NACL_APP_THREAD_H__ 1
  38
  39 #include "native_client/include/nacl_base.h"
  40 #include "native_client/service_runtime/nacl_bottom_half.h"
  41 #include "native_client/service_runtime/nacl_config.h"
  42 #include "native_client/service_runtime/nacl_desc_effector.h"
  43 #include "native_client/service_runtime/nacl_sync.h"
  44 #include "native_client/service_runtime/nacl_threads.h"
  45 #include "native_client/service_runtime/sel_rt.h"
  46
  47 EXTERN_C_BEGIN
  48
  49 struct NaClApp;
  50
  51 enum NaClThreadState {
  52   NACL_APP_THREAD_ALIVE,
  53   /* NACL_APP_THREAD_INTERRUPTIBLE_MUTEX, etc */
  54   NACL_APP_THREAD_SUICIDE_PENDING,
  55   NACL_APP_THREAD_DEAD
  56 };
  57
  58 /*
  59  * Generally, only the thread itself will need to manipulate this
  60  * structure, but occasionally we may need to blow away a thread for
  61  * some reason, and look inside.  While a thread is in the NaCl
  62  * application running untrusted code, the lock must *not* be held.
  63  */
  64 struct NaClAppThread {
  65   struct NaClMutex          mu;
  66   struct NaClCondVar        cv;
  67
  68   int                       is_privileged;  /* can make "special" syscalls? */
  69
  70   uint32_t                  refcount;
  71
  72   struct NaClClosureResult  result;
  73
  74   uint32_t                  sysret;
  75
  76   /*
  77    * The NaCl app that contains this thread.  The app must exist as
  78    * long as a thread is still alive.
  79    */
  80   struct NaClApp            *nap;
  81
  82   /*
  83    * The effector interface object used to manipulate NaCl apps by the
  84    * objects in the NaClDesc class hierarchy.  Used by this thread when
  85    * making NaClDesc method calls from syscall handlers.
  86    */
  87   struct NaClDescEffector   *effp;
  88
  89   int                       thread_num;  /* index into nap->threads */
  90
  91   struct NaClThread         thread;  /* low level thread representation */
  92
  93   /*
  94    * WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
  95    *
  96    * The locking behavior described below is not yet implemented.
  97    *
  98    * WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
  99    *
 100    * When a thread invokes a service call from the NaCl application,
 101    * it must first grab its own lock (mu) before it executes any code
 102    * that can grab other service runtime locks/resources.  The thread
 103    * clears the holding_sr_locks flag as it is about to return from
 104    * the service call.  Short duration service calls can just hold the
 105    * lock throughout; potentially blocking service calls must drop the
 106    * thread lock and reacquire when it can unblock.  Condition
 107    * variables are used to allow the thread to wake up.  If a thread
 108    * is blocked waiting for I/O, a central epoll thread is responsible
 109    * for waking up the thread.  (The epoll thread serves the same
 110    * purpose as hardware interrupt handlers.)
 111    *
 112    * To summarily kill a thread from elsewhere, we check the
 113    * holding_sr_locks flag after acquiring the target thread's lock.
 114    * If it is clear, then the thread is running in the application
 115    * space (or at least it has not yet touched any service runtime
 116    * resources), and we can directly pthread_kill it before we release
 117    * the thread lock.  If it is set, we set the state flag to
 118    * NACL_APP_THREAD_SUICIDE_PENDING and release the thread lock,
 119    * possibly waking the blocked thread.
 120    *
 121    * When the thread is about to leave service runtime code and return
 122    * to the NaCl application, it should have released all locks to
 123    * service-runtime resources.  Next, the thread grabs its own lock
 124    * to clear the holding_sr_locks flag, at which point it examines
 125    * the suicide flag; if it finds that set, it should gracefully
 126    * exit.
 127    */
 128   int                       holding_sr_locks;
 129
 130   /*
 131    * a thread cannot free up its own mutex lock and commit suicide,
 132    * since another thread may be trying to summarily kill it and is
 133    * waiting on the lock in order to ask it to commit suicide!
 134    * instead, the suiciding thread just marks itself as dead, and a
 135    * periodic thread grabs a global thread table lock to do thread
 136    * deletion (which the thread requesting summary execution must also
 137    * grab).
 138    */
 139   enum NaClThreadState      state;
 140
 141   struct NaClThreadContext  user;
 142   /* sys is only used to hold segment registers */
 143   struct NaClThreadContext  sys;
 144   /*
 145    * NaClThread abstraction allows us to specify the stack size
 146    * (NACL_KERN_STACK_SIZE), but not its location.  The underlying
 147    * implementation takes care of finding memory for the thread stack,
 148    * and when the thread exits (they're not joinable), the stack
 149    * should be automatically released.
 150    */
 151
 152   uint32_t                  *x_esp;
 153   /*
 154    * user's %esp translated to system address, used for accessing syscall
 155    * arguments
 156    */
 157 };
 158
 159 int NaClAppThreadCtor(struct NaClAppThread  *natp,
 160                       struct NaClApp        *nap,
 161                       int                   is_privileged,
 162                       uintptr_t             entry,
 163                       uintptr_t             esp,
 164                       uint16_t              gs);
 165
 166 void NaClAppThreadDtor(struct NaClAppThread *natp);
 167
 168 /*
 169  * Low level initialization of thread, with validated values.  The
 170  * usr_entry and usr_esp values are directly used to initialize the
 171  * user register values; the sys_tdb_base is the system address for
 172  * allocating a %gs thread descriptor block base.  The caller is
 173  * responsible for error checking: usr_entry is a valid entry point (0
 174  * mod N) and sys_tdb_base is in the NaClApp's address space.
 175  */
 176 int NaClAppThreadAllocSegCtor(struct NaClAppThread  *natp,
 177                               struct NaClApp        *nap,
 178                               int                   is_privileged,
 179                               uintptr_t             usr_entry,
 180                               uintptr_t             usr_esp,
 181                               uintptr_t             sys_tdb_base,
 182                               size_t                tdb_size);
 183
 184 int NaClAppThreadIncRef(struct NaClAppThread *natp);
 185
 186 int NaClAppThreadDecRef(struct NaClAppThread *natp);
 187
 188 EXTERN_C_END
 189
 190 #endif