gdb/remote-notif.c

   1 /* Remote notification in GDB protocol
   2
   3    Copyright (C) 1988-2020 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 bool notif_debug = false;
  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 /* Parse the BUF for the expected notification NC, and send packet to
  56    acknowledge.  */
  57
  58 void
  59 remote_notif_ack (remote_target *remote,
  60                   struct notif_client *nc, const char *buf)
  61 {
  62   notif_event_up event = nc->alloc_event ();
  63
  64   if (notif_debug)
  65     fprintf_unfiltered (gdb_stdlog, "notif: ack '%s'\n",
  66                         nc->ack_command);
  67
  68   nc->parse (remote, nc, buf, event.get ());
  69   nc->ack (remote, nc, buf, event.release ());
  70 }
  71
  72 /* Parse the BUF for the expected notification NC.  */
  73
  74 struct notif_event *
  75 remote_notif_parse (remote_target *remote,
  76                     struct notif_client *nc, const char *buf)
  77 {
  78   notif_event_up event = nc->alloc_event ();
  79
  80   if (notif_debug)
  81     fprintf_unfiltered (gdb_stdlog, "notif: parse '%s'\n", nc->name);
  82
  83   nc->parse (remote, nc, buf, event.get ());
  84
  85   return event.release ();
  86 }
  87
  88 /* Process notifications in STATE's notification queue one by one.
  89    EXCEPT is not expected in the queue.  */
  90
  91 void
  92 remote_notif_process (struct remote_notif_state *state,
  93                       struct notif_client *except)
  94 {
  95   while (!state->notif_queue.empty ())
  96     {
  97       struct notif_client *nc = state->notif_queue.front ();
  98       state->notif_queue.pop_front ();
  99
 100       gdb_assert (nc != except);
 101
 102       if (nc->can_get_pending_events (state->remote, nc))
 103         remote_notif_get_pending_events (state->remote, nc);
 104     }
 105 }
 106
 107 static void
 108 remote_async_get_pending_events_handler (gdb_client_data data)
 109 {
 110   gdb_assert (target_is_non_stop_p ());
 111   remote_notif_process ((struct remote_notif_state *) data, NULL);
 112 }
 113
 114 /* Remote notification handler.  Parse BUF, queue notification and
 115    update STATE.  */
 116
 117 void
 118 handle_notification (struct remote_notif_state *state, const char *buf)
 119 {
 120   struct notif_client *nc;
 121   size_t i;
 122
 123   for (i = 0; i < ARRAY_SIZE (notifs); i++)
 124     {
 125       const char *name = notifs[i]->name;
 126
 127       if (startswith (buf, name)
 128           && buf[strlen (name)] == ':')
 129         break;
 130     }
 131
 132   /* We ignore notifications we don't recognize, for compatibility
 133      with newer stubs.  */
 134   if (i == ARRAY_SIZE (notifs))
 135     return;
 136
 137   nc =  notifs[i];
 138
 139   if (state->pending_event[nc->id] != NULL)
 140     {
 141       /* We've already parsed the in-flight reply, but the stub for some
 142          reason thought we didn't, possibly due to timeout on its side.
 143          Just ignore it.  */
 144       if (notif_debug)
 145         fprintf_unfiltered (gdb_stdlog,
 146                             "notif: ignoring resent notification\n");
 147     }
 148   else
 149     {
 150       struct notif_event *event
 151         = remote_notif_parse (state->remote, nc, buf + strlen (nc->name) + 1);
 152
 153       /* Be careful to only set it after parsing, since an error
 154          may be thrown then.  */
 155       state->pending_event[nc->id] = event;
 156
 157       /* Notify the event loop there's a stop reply to acknowledge
 158          and that there may be more events to fetch.  */
 159       state->notif_queue.push_back (nc);
 160       if (target_is_non_stop_p ())
 161         {
 162           /* In non-stop, We mark REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN
 163              in order to go on what we were doing and postpone
 164              querying notification events to some point safe to do so.
 165              See details in the function comment of
 166              remote.c:remote_notif_get_pending_events.
 167
 168              In all-stop, GDB may be blocked to wait for the reply, we
 169              shouldn't return to event loop until the expected reply
 170              arrives.  For example:
 171
 172              1.1) --> vCont;c
 173                GDB expects getting stop reply 'T05 thread:2'.
 174              1.2) <-- %Notif
 175                <GDB marks the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 176
 177              After step #1.2, we return to the event loop, which
 178              notices there is a new event on the
 179              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and calls the
 180              handler, which will send 'vNotif' packet.
 181              1.3) --> vNotif
 182              It is not safe to start a new sequence, because target
 183              is still running and GDB is expecting the stop reply
 184              from stub.
 185
 186              To solve this, whenever we parse a notification
 187              successfully, we don't mark the
 188              REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN and let GDB blocked
 189              there as before to get the sequence done.
 190
 191              2.1) --> vCont;c
 192                GDB expects getting stop reply 'T05 thread:2'
 193              2.2) <-- %Notif
 194                <Don't mark the REMOTE_ASYNC_GET_PENDING_EVENTS_TOKEN>
 195              2.3) <-- T05 thread:2
 196
 197              These pending notifications can be processed later.  */
 198           mark_async_event_handler (state->get_pending_events_token);
 199         }
 200
 201       if (notif_debug)
 202         fprintf_unfiltered (gdb_stdlog,
 203                             "notif: Notification '%s' captured\n",
 204                             nc->name);
 205     }
 206 }
 207
 208 /* Return an allocated remote_notif_state.  */
 209
 210 struct remote_notif_state *
 211 remote_notif_state_allocate (remote_target *remote)
 212 {
 213   struct remote_notif_state *notif_state = new struct remote_notif_state;
 214
 215   notif_state->remote = remote;
 216
 217   /* Register async_event_handler for notification.  */
 218
 219   notif_state->get_pending_events_token
 220     = create_async_event_handler (remote_async_get_pending_events_handler,
 221                                   notif_state);
 222
 223   return notif_state;
 224 }
 225
 226 /* Free STATE and its fields.  */
 227
 228 remote_notif_state::~remote_notif_state ()
 229 {
 230   int i;
 231
 232   /* Unregister async_event_handler for notification.  */
 233   if (get_pending_events_token != NULL)
 234     delete_async_event_handler (&get_pending_events_token);
 235
 236   for (i = 0; i < REMOTE_NOTIF_LAST; i++)
 237     delete pending_event[i];
 238 }
 239
 240 void
 241 _initialize_notif (void)
 242 {
 243   add_setshow_boolean_cmd ("notification", no_class, &notif_debug,
 244                            _("\
 245 Set debugging of async remote notification."), _("\
 246 Show debugging of async remote notification."), _("\
 247 When non-zero, debugging output about async remote notifications"
 248 " is enabled."),
 249                            NULL,
 250                            NULL,
 251                            &setdebuglist, &showdebuglist);
 252 }