gdb/remote-notif.c

   1 /* Remote notification in GDB protocol
   2
   3    Copyright (C) 1988-2014 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 /* Remote async notification is sent from remote target over RSP.
  21    Each type of notification is represented by an object of
  22    'struct notif', which has a field 'pending_reply'.  It is not
  23    NULL when GDB receives a notification from GDBserver, but hasn't
  24    acknowledge yet.  Before GDB acknowledges the notification,
  25    GDBserver shouldn't send notification again (see the header comments
  26    in gdbserver/notif.c).
  27
  28    Notifications are processed in an almost-unified approach for both
  29    all-stop mode and non-stop mode, except the timing to process them.
  30    In non-stop mode, notifications are processed in
  31    remote_async_get_pending_events_handler, while in all-stop mode,
  32    they are processed in remote_resume.  */
  33
  34 #include "defs.h"
  35 #include "remote.h"
  36 #include "remote-notif.h"
  37 #include "observer.h"
  38 #include "event-loop.h"
  39 #include "target.h"
  40 #include "inferior.h"
  41 #include "gdbcmd.h"
  42
  43 #include <string.h>
  44
  45 int notif_debug = 0;
  46
  47 /* Supported clients of notifications.  */
  48
  49 static struct notif_client *notifs[] =
  50 {
  51   &notif_client_stop,
  52 };
  53
  54 gdb_static_assert (ARRAY_SIZE (notifs) == REMOTE_NOTIF_LAST);
  55
  56 static void do_notif_event_xfree (void *arg);
  57
  58 /* Parse the BUF for the expected notification NC, and send packet to
  59    acknowledge.  */
  60
  61 void
  62 remote_notif_ack (struct notif_client *nc, char *buf)
  63 {
  64   struct notif_event *event = nc->alloc_event ();
  65   struct cleanup *old_chain
  66     = make_cleanup (do_notif_event_xfree, event);
  67
  68   if (notif_debug)
  69     fprintf_unfiltered (gdb_stdlog, "notif: ack '%s'\n",
  70                         nc->ack_command);
  71
  72   nc->parse (nc, buf, event);
  73   nc->ack (nc, buf, event);
  74
  75   discard_cleanups (old_chain);
  76 }
  77
  78 /* Parse the BUF for the expected notification NC.  */
  79
  80 struct notif_event *
  81 remote_notif_parse (struct notif_client *nc, char *buf)
  82 {
  83   struct notif_event *event = nc->alloc_event ();
  84   struct cleanup *old_chain
  85     = make_cleanup (do_notif_event_xfree, event);
  86
  87   if (notif_debug)
  88     fprintf_unfiltered (gdb_stdlog, "notif: parse '%s'\n", nc->name);
  89
  90   nc->parse (nc, buf, event);
  91
  92   discard_cleanups (old_chain);
  93   return event;
  94 }
  95
  96 DEFINE_QUEUE_P (notif_client_p);
  97
  98 /* Process notifications in STATE's notification queue one by one.
  99    EXCEPT is not expected in the queue.  */
 100
 101 void
 102 remote_notif_process (struct remote_notif_state *state,
 103                       struct notif_client *except)
 104 {
 105   while (!QUEUE_is_empty (notif_client_p, state->notif_queue))
 106     {
 107       struct notif_client *nc = QUEUE_deque (notif_client_p,
 108                                              state->notif_queue);
 109
 110       gdb_assert (nc != except);
 111
 112       if (nc->can_get_pending_events (nc))
 113         remote_notif_get_pending_events (nc);
 114     }
 115 }
 116
 117 static void
 118 remote_async_get_pending_events_handler (gdb_client_data data)
 119 {
 120   gdb_assert (non_stop);
 121   remote_notif_process (data, NULL);
 122 }
 123
 124 /* Remote notification handler.  Parse BUF, queue notification and
 125    update STATE.  */
 126
 127 void
 128 handle_notification (struct remote_notif_state *state, char *buf)
 129 {
 130   struct notif_client *nc;
 131   size_t i;
 132
 133   for (i = 0; i < ARRAY_SIZE (notifs); i++)
 134     {
 135       const char *name = notifs[i]->name;
 136
 137       if (strncmp (buf, name, strlen (name)) == 0
 138           && buf[strlen (name)] == ':')
 139         break;
 140     }
 141
 142   /* We ignore notifications we don't recognize, for compatibility
 143      with newer stubs.  */
 144   if (i == ARRAY_SIZE (notifs))
 145     return;
 146
 147   nc =  notifs[i];
 148
 149   if (state->pending_event[nc->id] != NULL)
 150     {
 151       /* We've already parsed the in-flight reply, but the stub for some
 152          reason thought we didn't, possibly due to timeout on its side.
 153          Just ignore it.  */
 154       if (notif_debug)
 155         fprintf_unfiltered (gdb_stdlog,
 156                             "notif: ignoring resent notification\n");
 157     }
 158   else
 159     {
 160       struct notif_event *event
 161         = remote_notif_parse (nc, buf + strlen (nc->name) + 1);
 162
 163       /* Be careful to only set it after parsing, since an error
 164          may be thrown then.  */
 165       state->pending_event[nc->id] = event;
 166
 167       /* Notify the event loop there's a stop reply to acknowledge
 168          and that there may be more events to fetch.  */
 169       QUEUE_enque (notif_client_p, state->notif_queue, nc);
 170       if (non_stop)
 171         {
 172           /* In non-stop, We mark REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN
 173              in order to go on what we were doing and postpone
 174              querying notification events to some point safe to do so.
 175              See details in the function comment of
 176              remote.c:remote_notif_get_pending_events.
 177
 178              In all-stop, GDB may be blocked to wait for the reply, we
 179              shouldn't return to event loop until the expected reply
 180              arrives.  For example:
 181
 182              1.1) --> vCont;c
 183                GDB expects getting stop reply 'T05 thread:2'.
 184              1.2) <-- %Notif
 185                <GDB marks the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 186
 187              After step #1.2, we return to the event loop, which
 188              notices there is a new event on the
 189              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and calls the
 190              handler, which will send 'vNotif' packet.
 191              1.3) --> vNotif
 192              It is not safe to start a new sequence, because target
 193              is still running and GDB is expecting the stop reply
 194              from stub.
 195
 196              To solve this, whenever we parse a notification
 197              successfully, we don't mark the
 198              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and let GDB blocked
 199              there as before to get the sequence done.
 200
 201              2.1) --> vCont;c
 202                GDB expects getting stop reply 'T05 thread:2'
 203              2.2) <-- %Notif
 204                <Don't mark the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 205              2.3) <-- T05 thread:2
 206
 207              These pending notifications can be processed later.  */
 208           mark_async_event_handler (state->get_pending_events_token);
 209         }
 210
 211       if (notif_debug)
 212         fprintf_unfiltered (gdb_stdlog,
 213                             "notif: Notification '%s' captured\n",
 214                             nc->name);
 215     }
 216 }
 217
 218 /* Invoke destructor of EVENT and xfree it.  */
 219
 220 void
 221 notif_event_xfree (struct notif_event *event)
 222 {
 223   if (event != NULL && event->dtr != NULL)
 224     event->dtr (event);
 225
 226   xfree (event);
 227 }
 228
 229 /* Cleanup wrapper.  */
 230
 231 static void
 232 do_notif_event_xfree (void *arg)
 233 {
 234   notif_event_xfree (arg);
 235 }
 236
 237 /* Return an allocated remote_notif_state.  */
 238
 239 struct remote_notif_state *
 240 remote_notif_state_allocate (void)
 241 {
 242   struct remote_notif_state *notif_state = xzalloc (sizeof (*notif_state));
 243
 244   notif_state->notif_queue = QUEUE_alloc (notif_client_p, NULL);
 245
 246   /* Register async_event_handler for notification.  */
 247
 248   notif_state->get_pending_events_token
 249     = create_async_event_handler (remote_async_get_pending_events_handler,
 250                                   notif_state);
 251
 252   return notif_state;
 253 }
 254
 255 /* Free STATE and its fields.  */
 256
 257 void
 258 remote_notif_state_xfree (struct remote_notif_state *state)
 259 {
 260   int i;
 261
 262   QUEUE_free (notif_client_p, state->notif_queue);
 263
 264   /* Unregister async_event_handler for notification.  */
 265   if (state->get_pending_events_token != NULL)
 266     delete_async_event_handler (&state->get_pending_events_token);
 267
 268   for (i = 0; i < REMOTE_NOTIF_LAST; i++)
 269     notif_event_xfree (state->pending_event[i]);
 270
 271   xfree (state);
 272 }
 273
 274 /* -Wmissing-prototypes */
 275 extern initialize_file_ftype _initialize_notif;
 276
 277 void
 278 _initialize_notif (void)
 279 {
 280   add_setshow_boolean_cmd ("notification", no_class, &notif_debug,
 281                            _("\
 282 Set debugging of async remote notification."), _("\
 283 Show debugging of async remote notification."), _("\
 284 When non-zero, debugging output about async remote notifications"
 285 " is enabled."),
 286                            NULL,
 287                            NULL,
 288                            &setdebuglist, &showdebuglist);
 289 }