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 "observer.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 (struct notif_client *nc, char *buf)
  62 {
  63   struct notif_event *event = nc->alloc_event ();
  64   struct cleanup *old_chain
  65     = make_cleanup (do_notif_event_xfree, event);
  66
  67   if (notif_debug)
  68     fprintf_unfiltered (gdb_stdlog, "notif: ack '%s'\n",
  69                         nc->ack_command);
  70
  71   nc->parse (nc, buf, event);
  72   nc->ack (nc, buf, event);
  73
  74   discard_cleanups (old_chain);
  75 }
  76
  77 /* Parse the BUF for the expected notification NC.  */
  78
  79 struct notif_event *
  80 remote_notif_parse (struct notif_client *nc, char *buf)
  81 {
  82   struct notif_event *event = nc->alloc_event ();
  83   struct cleanup *old_chain
  84     = make_cleanup (do_notif_event_xfree, event);
  85
  86   if (notif_debug)
  87     fprintf_unfiltered (gdb_stdlog, "notif: parse '%s'\n", nc->name);
  88
  89   nc->parse (nc, buf, event);
  90
  91   discard_cleanups (old_chain);
  92   return event;
  93 }
  94
  95 DEFINE_QUEUE_P (notif_client_p);
  96
  97 /* Process notifications in STATE's notification queue one by one.
  98    EXCEPT is not expected in the queue.  */
  99
 100 void
 101 remote_notif_process (struct remote_notif_state *state,
 102                       struct notif_client *except)
 103 {
 104   while (!QUEUE_is_empty (notif_client_p, state->notif_queue))
 105     {
 106       struct notif_client *nc = QUEUE_deque (notif_client_p,
 107                                              state->notif_queue);
 108
 109       gdb_assert (nc != except);
 110
 111       if (nc->can_get_pending_events (nc))
 112         remote_notif_get_pending_events (nc);
 113     }
 114 }
 115
 116 static void
 117 remote_async_get_pending_events_handler (gdb_client_data data)
 118 {
 119   gdb_assert (target_is_non_stop_p ());
 120   remote_notif_process ((struct remote_notif_state *) data, NULL);
 121 }
 122
 123 /* Remote notification handler.  Parse BUF, queue notification and
 124    update STATE.  */
 125
 126 void
 127 handle_notification (struct remote_notif_state *state, char *buf)
 128 {
 129   struct notif_client *nc;
 130   size_t i;
 131
 132   for (i = 0; i < ARRAY_SIZE (notifs); i++)
 133     {
 134       const char *name = notifs[i]->name;
 135
 136       if (startswith (buf, name)
 137           && buf[strlen (name)] == ':')
 138         break;
 139     }
 140
 141   /* We ignore notifications we don't recognize, for compatibility
 142      with newer stubs.  */
 143   if (i == ARRAY_SIZE (notifs))
 144     return;
 145
 146   nc =  notifs[i];
 147
 148   if (state->pending_event[nc->id] != NULL)
 149     {
 150       /* We've already parsed the in-flight reply, but the stub for some
 151          reason thought we didn't, possibly due to timeout on its side.
 152          Just ignore it.  */
 153       if (notif_debug)
 154         fprintf_unfiltered (gdb_stdlog,
 155                             "notif: ignoring resent notification\n");
 156     }
 157   else
 158     {
 159       struct notif_event *event
 160         = remote_notif_parse (nc, buf + strlen (nc->name) + 1);
 161
 162       /* Be careful to only set it after parsing, since an error
 163          may be thrown then.  */
 164       state->pending_event[nc->id] = event;
 165
 166       /* Notify the event loop there's a stop reply to acknowledge
 167          and that there may be more events to fetch.  */
 168       QUEUE_enque (notif_client_p, state->notif_queue, nc);
 169       if (target_is_non_stop_p ())
 170         {
 171           /* In non-stop, We mark REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN
 172              in order to go on what we were doing and postpone
 173              querying notification events to some point safe to do so.
 174              See details in the function comment of
 175              remote.c:remote_notif_get_pending_events.
 176
 177              In all-stop, GDB may be blocked to wait for the reply, we
 178              shouldn't return to event loop until the expected reply
 179              arrives.  For example:
 180
 181              1.1) --> vCont;c
 182                GDB expects getting stop reply 'T05 thread:2'.
 183              1.2) <-- %Notif
 184                <GDB marks the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 185
 186              After step #1.2, we return to the event loop, which
 187              notices there is a new event on the
 188              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and calls the
 189              handler, which will send 'vNotif' packet.
 190              1.3) --> vNotif
 191              It is not safe to start a new sequence, because target
 192              is still running and GDB is expecting the stop reply
 193              from stub.
 194
 195              To solve this, whenever we parse a notification
 196              successfully, we don't mark the
 197              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and let GDB blocked
 198              there as before to get the sequence done.
 199
 200              2.1) --> vCont;c
 201                GDB expects getting stop reply 'T05 thread:2'
 202              2.2) <-- %Notif
 203                <Don't mark the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 204              2.3) <-- T05 thread:2
 205
 206              These pending notifications can be processed later.  */
 207           mark_async_event_handler (state->get_pending_events_token);
 208         }
 209
 210       if (notif_debug)
 211         fprintf_unfiltered (gdb_stdlog,
 212                             "notif: Notification '%s' captured\n",
 213                             nc->name);
 214     }
 215 }
 216
 217 /* Invoke destructor of EVENT and xfree it.  */
 218
 219 void
 220 notif_event_xfree (struct notif_event *event)
 221 {
 222   if (event != NULL && event->dtr != NULL)
 223     event->dtr (event);
 224
 225   xfree (event);
 226 }
 227
 228 /* Cleanup wrapper.  */
 229
 230 static void
 231 do_notif_event_xfree (void *arg)
 232 {
 233   notif_event_xfree ((struct notif_event *) arg);
 234 }
 235
 236 /* Return an allocated remote_notif_state.  */
 237
 238 struct remote_notif_state *
 239 remote_notif_state_allocate (void)
 240 {
 241   struct remote_notif_state *notif_state = XCNEW (struct remote_notif_state);
 242
 243   notif_state->notif_queue = QUEUE_alloc (notif_client_p, NULL);
 244
 245   /* Register async_event_handler for notification.  */
 246
 247   notif_state->get_pending_events_token
 248     = create_async_event_handler (remote_async_get_pending_events_handler,
 249                                   notif_state);
 250
 251   return notif_state;
 252 }
 253
 254 /* Free STATE and its fields.  */
 255
 256 void
 257 remote_notif_state_xfree (struct remote_notif_state *state)
 258 {
 259   int i;
 260
 261   QUEUE_free (notif_client_p, state->notif_queue);
 262
 263   /* Unregister async_event_handler for notification.  */
 264   if (state->get_pending_events_token != NULL)
 265     delete_async_event_handler (&state->get_pending_events_token);
 266
 267   for (i = 0; i < REMOTE_NOTIF_LAST; i++)
 268     notif_event_xfree (state->pending_event[i]);
 269
 270   xfree (state);
 271 }
 272
 273 void
 274 _initialize_notif (void)
 275 {
 276   add_setshow_boolean_cmd ("notification", no_class, &notif_debug,
 277                            _("\
 278 Set debugging of async remote notification."), _("\
 279 Show debugging of async remote notification."), _("\
 280 When non-zero, debugging output about async remote notifications"
 281 " is enabled."),
 282                            NULL,
 283                            NULL,
 284                            &setdebuglist, &showdebuglist);
 285 }