gdb/remote-notif.c

   1 /* Remote notification in GDB protocol
   2
   3    Copyright (C) 1988-2018 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 "observable.h"
  38 #include "event-loop.h"
  39 #include "target.h"
  40 #include "inferior.h"
  41 #include "infrun.h"
  42 #include "gdbcmd.h"
  43
  44 int notif_debug = 0;
  45
  46 /* Supported clients of notifications.  */
  47
  48 static struct notif_client *notifs[] =
  49 {
  50   &notif_client_stop,
  51 };
  52
  53 gdb_static_assert (ARRAY_SIZE (notifs) == REMOTE_NOTIF_LAST);
  54
  55 static void do_notif_event_xfree (void *arg);
  56
  57 /* Parse the BUF for the expected notification NC, and send packet to
  58    acknowledge.  */
  59
  60 void
  61 remote_notif_ack (remote_target *remote,
  62                   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 (remote, nc, buf, event);
  73   nc->ack (remote, 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 (remote_target *remote,
  82                     struct notif_client *nc, char *buf)
  83 {
  84   struct notif_event *event = nc->alloc_event ();
  85   struct cleanup *old_chain
  86     = make_cleanup (do_notif_event_xfree, event);
  87
  88   if (notif_debug)
  89     fprintf_unfiltered (gdb_stdlog, "notif: parse '%s'\n", nc->name);
  90
  91   nc->parse (remote, nc, buf, event);
  92
  93   discard_cleanups (old_chain);
  94   return event;
  95 }
  96
  97 DEFINE_QUEUE_P (notif_client_p);
  98
  99 /* Process notifications in STATE's notification queue one by one.
 100    EXCEPT is not expected in the queue.  */
 101
 102 void
 103 remote_notif_process (struct remote_notif_state *state,
 104                       struct notif_client *except)
 105 {
 106   while (!QUEUE_is_empty (notif_client_p, state->notif_queue))
 107     {
 108       struct notif_client *nc = QUEUE_deque (notif_client_p,
 109                                              state->notif_queue);
 110
 111       gdb_assert (nc != except);
 112
 113       if (nc->can_get_pending_events (state->remote, nc))
 114         remote_notif_get_pending_events (state->remote, nc);
 115     }
 116 }
 117
 118 static void
 119 remote_async_get_pending_events_handler (gdb_client_data data)
 120 {
 121   gdb_assert (target_is_non_stop_p ());
 122   remote_notif_process ((struct remote_notif_state *) data, NULL);
 123 }
 124
 125 /* Remote notification handler.  Parse BUF, queue notification and
 126    update STATE.  */
 127
 128 void
 129 handle_notification (struct remote_notif_state *state, char *buf)
 130 {
 131   struct notif_client *nc;
 132   size_t i;
 133
 134   for (i = 0; i < ARRAY_SIZE (notifs); i++)
 135     {
 136       const char *name = notifs[i]->name;
 137
 138       if (startswith (buf, name)
 139           && buf[strlen (name)] == ':')
 140         break;
 141     }
 142
 143   /* We ignore notifications we don't recognize, for compatibility
 144      with newer stubs.  */
 145   if (i == ARRAY_SIZE (notifs))
 146     return;
 147
 148   nc =  notifs[i];
 149
 150   if (state->pending_event[nc->id] != NULL)
 151     {
 152       /* We've already parsed the in-flight reply, but the stub for some
 153          reason thought we didn't, possibly due to timeout on its side.
 154          Just ignore it.  */
 155       if (notif_debug)
 156         fprintf_unfiltered (gdb_stdlog,
 157                             "notif: ignoring resent notification\n");
 158     }
 159   else
 160     {
 161       struct notif_event *event
 162         = remote_notif_parse (state->remote, nc, buf + strlen (nc->name) + 1);
 163
 164       /* Be careful to only set it after parsing, since an error
 165          may be thrown then.  */
 166       state->pending_event[nc->id] = event;
 167
 168       /* Notify the event loop there's a stop reply to acknowledge
 169          and that there may be more events to fetch.  */
 170       QUEUE_enque (notif_client_p, state->notif_queue, nc);
 171       if (target_is_non_stop_p ())
 172         {
 173           /* In non-stop, We mark REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN
 174              in order to go on what we were doing and postpone
 175              querying notification events to some point safe to do so.
 176              See details in the function comment of
 177              remote.c:remote_notif_get_pending_events.
 178
 179              In all-stop, GDB may be blocked to wait for the reply, we
 180              shouldn't return to event loop until the expected reply
 181              arrives.  For example:
 182
 183              1.1) --> vCont;c
 184                GDB expects getting stop reply 'T05 thread:2'.
 185              1.2) <-- %Notif
 186                <GDB marks the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 187
 188              After step #1.2, we return to the event loop, which
 189              notices there is a new event on the
 190              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and calls the
 191              handler, which will send 'vNotif' packet.
 192              1.3) --> vNotif
 193              It is not safe to start a new sequence, because target
 194              is still running and GDB is expecting the stop reply
 195              from stub.
 196
 197              To solve this, whenever we parse a notification
 198              successfully, we don't mark the
 199              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and let GDB blocked
 200              there as before to get the sequence done.
 201
 202              2.1) --> vCont;c
 203                GDB expects getting stop reply 'T05 thread:2'
 204              2.2) <-- %Notif
 205                <Don't mark the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 206              2.3) <-- T05 thread:2
 207
 208              These pending notifications can be processed later.  */
 209           mark_async_event_handler (state->get_pending_events_token);
 210         }
 211
 212       if (notif_debug)
 213         fprintf_unfiltered (gdb_stdlog,
 214                             "notif: Notification '%s' captured\n",
 215                             nc->name);
 216     }
 217 }
 218
 219 /* Invoke destructor of EVENT and xfree it.  */
 220
 221 void
 222 notif_event_xfree (struct notif_event *event)
 223 {
 224   if (event != NULL && event->dtr != NULL)
 225     event->dtr (event);
 226
 227   xfree (event);
 228 }
 229
 230 /* Cleanup wrapper.  */
 231
 232 static void
 233 do_notif_event_xfree (void *arg)
 234 {
 235   notif_event_xfree ((struct notif_event *) arg);
 236 }
 237
 238 /* Return an allocated remote_notif_state.  */
 239
 240 struct remote_notif_state *
 241 remote_notif_state_allocate (remote_target *remote)
 242 {
 243   struct remote_notif_state *notif_state = XCNEW (struct remote_notif_state);
 244
 245   notif_state->remote = remote;
 246
 247   notif_state->notif_queue = QUEUE_alloc (notif_client_p, NULL);
 248
 249   /* Register async_event_handler for notification.  */
 250
 251   notif_state->get_pending_events_token
 252     = create_async_event_handler (remote_async_get_pending_events_handler,
 253                                   notif_state);
 254
 255   return notif_state;
 256 }
 257
 258 /* Free STATE and its fields.  */
 259
 260 void
 261 remote_notif_state_xfree (struct remote_notif_state *state)
 262 {
 263   int i;
 264
 265   QUEUE_free (notif_client_p, state->notif_queue);
 266
 267   /* Unregister async_event_handler for notification.  */
 268   if (state->get_pending_events_token != NULL)
 269     delete_async_event_handler (&state->get_pending_events_token);
 270
 271   for (i = 0; i < REMOTE_NOTIF_LAST; i++)
 272     notif_event_xfree (state->pending_event[i]);
 273
 274   xfree (state);
 275 }
 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 }