gdbserver/notif.cc

   1 /* Notification to GDB.
   2    Copyright (C) 1989-2024 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 "notif.h"
  51
  52 static struct notif_server *notifs[] =
  53 {
  54   &notif_stop,
  55 };
  56
  57 /* Write another event or an OK, if there are no more left, to
  58    OWN_BUF.  */
  59
  60 void
  61 notif_write_event (struct notif_server *notif, char *own_buf)
  62 {
  63   if (!notif->queue.empty ())
  64     {
  65       struct notif_event *event = notif->queue.front ();
  66
  67       notif->write (event, own_buf);
  68     }
  69   else
  70     write_ok (own_buf);
  71 }
  72
  73 /* Handle the ack in buffer OWN_BUF,and packet length is PACKET_LEN.
  74    Return 1 if the ack is handled, and return 0 if the contents
  75    in OWN_BUF is not a ack.  */
  76
  77 int
  78 handle_notif_ack (char *own_buf, int packet_len)
  79 {
  80   size_t i;
  81   struct notif_server *np;
  82
  83   for (i = 0; i < ARRAY_SIZE (notifs); i++)
  84     {
  85       const char *ack_name = notifs[i]->ack_name;
  86
  87       if (startswith (own_buf, ack_name)
  88           && packet_len == strlen (ack_name))
  89         break;
  90     }
  91
  92   if (i == ARRAY_SIZE (notifs))
  93     return 0;
  94
  95   np = notifs[i];
  96
  97   /* If we're waiting for GDB to acknowledge a pending event,
  98      consider that done.  */
  99   if (!np->queue.empty ())
 100     {
 101       struct notif_event *head = np->queue.front ();
 102       np->queue.pop_front ();
 103
 104       remote_debug_printf ("%s: acking %d", np->ack_name,
 105                            (int) np->queue.size ());
 106
 107       delete head;
 108     }
 109
 110   notif_write_event (np, own_buf);
 111
 112   return 1;
 113 }
 114
 115 /* Put EVENT to the queue of NOTIF.  */
 116
 117 void
 118 notif_event_enque (struct notif_server *notif,
 119                    struct notif_event *event)
 120 {
 121   notif->queue.push_back (event);
 122
 123   remote_debug_printf ("pending events: %s %d", notif->notif_name,
 124                        (int) notif->queue.size ());
 125
 126 }
 127
 128 /* Push one event NEW_EVENT of notification NP into NP->queue.  */
 129
 130 void
 131 notif_push (struct notif_server *np, struct notif_event *new_event)
 132 {
 133   bool is_first_event = np->queue.empty ();
 134
 135   /* Something interesting.  Tell GDB about it.  */
 136   notif_event_enque (np, new_event);
 137
 138   /* If this is the first stop reply in the queue, then inform GDB
 139      about it, by sending a corresponding notification.  */
 140   if (is_first_event)
 141     {
 142       char buf[PBUFSIZ];
 143       char *p = buf;
 144
 145       xsnprintf (p, PBUFSIZ, "%s:", np->notif_name);
 146       p += strlen (p);
 147
 148       np->write (new_event, p);
 149       putpkt_notif (buf);
 150     }
 151 }