gdbserver/notif.cc

   1 /* Notification to GDB.
   2    Copyright (C) 1989-2020 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* Async notifications to GDB.  When the state of remote target is
  20    changed or something interesting to GDB happened, async
  21    notifications are used to tell GDB.
  22
  23    Each type of notification is represented by an object
  24    'struct notif_server', in which there is a queue for events to GDB
  25    represented by 'struct notif_event'.  GDBserver writes (by means of
  26    'write' field) each event in the queue into the buffer and send the
  27    contents in buffer to GDB.  The contents in buffer is specified in
  28    RSP.  See more in the comments to field 'queue' of
  29    'struct notif_server'.
  30
  31    Here is the workflow of sending events and managing queue:
  32    1.  At any time, when something interesting FOO happens, a object
  33    of 'struct notif_event' or its sub-class EVENT is created for FOO.
  34
  35    2.  Enque EVENT to the 'queue' field of 'struct notif_server' for
  36    FOO and send corresponding notification packet to GDB if EVENT is
  37    the first one.
  38    #1 and #2 are done by function 'notif_push'.
  39
  40    3.  EVENT is not deque'ed until the ack of FOO from GDB arrives.
  41    Before ack of FOO arrives, FOO happens again, a new object of
  42    EVENT is created and enque EVENT silently.
  43    Once GDB has a chance to ack to FOO, it sends an ack to GDBserver,
  44    and GDBserver repeatedly sends events to GDB and gets ack of FOO,
  45    until queue is empty.  Then, GDBserver sends 'OK' to GDB that all
  46    queued notification events are done.
  47
  48    # 3 is done by function 'handle_notif_ack'.  */
  49
  50 #include "server.h"
  51 #include "notif.h"
  52
  53 static struct notif_server *notifs[] =
  54 {
  55   &notif_stop,
  56 };
  57
  58 /* Write another event or an OK, if there are no more left, to
  59    OWN_BUF.  */
  60
  61 void
  62 notif_write_event (struct notif_server *notif, char *own_buf)
  63 {
  64   if (!notif->queue.empty ())
  65     {
  66       struct notif_event *event = notif->queue.front ();
  67
  68       notif->write (event, own_buf);
  69     }
  70   else
  71     write_ok (own_buf);
  72 }
  73
  74 /* Handle the ack in buffer OWN_BUF,and packet length is PACKET_LEN.
  75    Return 1 if the ack is handled, and return 0 if the contents
  76    in OWN_BUF is not a ack.  */
  77
  78 int
  79 handle_notif_ack (char *own_buf, int packet_len)
  80 {
  81   size_t i;
  82   struct notif_server *np;
  83
  84   for (i = 0; i < ARRAY_SIZE (notifs); i++)
  85     {
  86       const char *ack_name = notifs[i]->ack_name;
  87
  88       if (startswith (own_buf, ack_name)
  89           && packet_len == strlen (ack_name))
  90         break;
  91     }
  92
  93   if (i == ARRAY_SIZE (notifs))
  94     return 0;
  95
  96   np = notifs[i];
  97
  98   /* If we're waiting for GDB to acknowledge a pending event,
  99      consider that done.  */
 100   if (!np->queue.empty ())
 101     {
 102       struct notif_event *head = np->queue.front ();
 103       np->queue.pop_front ();
 104
 105       if (remote_debug)
 106         debug_printf ("%s: acking %d\n", np->ack_name,
 107                       (int) np->queue.size ());
 108
 109       delete head;
 110     }
 111
 112   notif_write_event (np, own_buf);
 113
 114   return 1;
 115 }
 116
 117 /* Put EVENT to the queue of NOTIF.  */
 118
 119 void
 120 notif_event_enque (struct notif_server *notif,
 121                    struct notif_event *event)
 122 {
 123   notif->queue.push_back (event);
 124
 125   if (remote_debug)
 126     debug_printf ("pending events: %s %d\n", notif->notif_name,
 127                   (int) notif->queue.size ());
 128
 129 }
 130
 131 /* Push one event NEW_EVENT of notification NP into NP->queue.  */
 132
 133 void
 134 notif_push (struct notif_server *np, struct notif_event *new_event)
 135 {
 136   bool is_first_event = np->queue.empty ();
 137
 138   /* Something interesting.  Tell GDB about it.  */
 139   notif_event_enque (np, new_event);
 140
 141   /* If this is the first stop reply in the queue, then inform GDB
 142      about it, by sending a corresponding notification.  */
 143   if (is_first_event)
 144     {
 145       char buf[PBUFSIZ];
 146       char *p = buf;
 147
 148       xsnprintf (p, PBUFSIZ, "%s:", np->notif_name);
 149       p += strlen (p);
 150
 151       np->write (new_event, p);
 152       putpkt_notif (buf);
 153     }
 154 }