The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/gdb/gdb_cons.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2006 Sam Leffler
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  *
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
   18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   20  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   27  */
   28 
   29 /* 
   30  * Support for redirecting console msgs to gdb.  We register
   31  * a pseudo console to hook cnputc and send stuff to the gdb
   32  * port.  The only trickiness here is buffering output so this
   33  * isn't dog slow.
   34  */
   35 
   36 #include <sys/cdefs.h>
   37 __FBSDID("$FreeBSD: releng/12.0/sys/gdb/gdb_cons.c 326269 2017-11-27 15:16:59Z pfg $");
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/cons.h>
   42 #include <sys/kdb.h>
   43 #include <sys/kernel.h>
   44 #include <sys/malloc.h>
   45 #include <sys/reboot.h>
   46 #include <sys/sysctl.h>
   47 
   48 #include <machine/gdb_machdep.h>
   49 #include <machine/kdb.h>
   50 
   51 #include <gdb/gdb.h>
   52 #include <gdb/gdb_int.h>
   53 
   54 struct gdbcons {
   55         int     npending;
   56         /* /2 for hex conversion, -6 for protocol glue */
   57         char    buf[GDB_BUFSZ/2 - 6];
   58         struct callout flush;
   59 };
   60 static struct gdbcons state = { -1 };
   61 
   62 static  int gdbcons_enable = 0;
   63 SYSCTL_INT(_debug, OID_AUTO, gdbcons, CTLFLAG_RWTUN, &gdbcons_enable,
   64             0, "copy console messages to GDB");
   65 
   66 static void
   67 gdb_cnprobe(struct consdev *cp)
   68 {
   69         sprintf(cp->cn_name, "gdb");
   70         cp->cn_pri = CN_LOW;            /* XXX no way to say "write only" */
   71 }
   72 
   73 static void
   74 gdb_cninit(struct consdev *cp)
   75 {
   76         struct gdbcons *c = &state;
   77 
   78         /* setup tx buffer and callout */
   79         if (c->npending == -1) {
   80                 c->npending = 0;
   81                 callout_init(&c->flush, 1);
   82                 cp->cn_arg = c;
   83         }
   84 }
   85 
   86 static void
   87 gdb_cnterm(struct consdev *cp)
   88 {
   89 }
   90 
   91 static void
   92 gdb_cngrab(struct consdev *cp)
   93 {
   94 }
   95 
   96 static void
   97 gdb_cnungrab(struct consdev *cp)
   98 {
   99 }
  100 
  101 static int
  102 gdb_cngetc(struct consdev *cp)
  103 {
  104         return -1;
  105 }
  106 
  107 static void
  108 gdb_tx_puthex(int c)
  109 {
  110         const char *hex = "0123456789abcdef";
  111 
  112         gdb_tx_char(hex[(c>>4)&0xf]);
  113         gdb_tx_char(hex[(c>>0)&0xf]);
  114 }
  115 
  116 static void
  117 gdb_cnflush(void *arg)
  118 {
  119         struct gdbcons *gc = arg;
  120         int i;
  121 
  122         gdb_tx_begin('O');
  123         for (i = 0; i < gc->npending; i++)
  124                 gdb_tx_puthex(gc->buf[i]);
  125         gdb_tx_end();
  126         gc->npending = 0;
  127 }
  128 
  129 /*
  130  * This glop is to figure out when it's safe to use callouts
  131  * to defer buffer flushing.  There's probably a better way
  132  * and/or an earlier point in the boot process when it's ok.
  133  */
  134 static int calloutok = 0;
  135 static void
  136 oktousecallout(void *data __unused)
  137 {
  138         calloutok = 1;
  139 }
  140 SYSINIT(gdbhack, SI_SUB_LAST, SI_ORDER_MIDDLE, oktousecallout, NULL);
  141 
  142 static void
  143 gdb_cnputc(struct consdev *cp, int c)
  144 {
  145         struct gdbcons *gc;
  146 
  147         if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
  148                 gc = cp->cn_arg;
  149                 if (gc->npending != 0) {
  150                         /*
  151                          * Cancel any pending callout and flush the
  152                          * buffer if there's no space for this byte.
  153                          */
  154                         if (calloutok)
  155                                 callout_stop(&gc->flush);
  156                         if (gc->npending == sizeof(gc->buf))
  157                                 gdb_cnflush(gc);
  158                 }
  159                 gc->buf[gc->npending++] = c;
  160                 /*
  161                  * Flush on end of line; this is especially helpful
  162                  * during boot when we don't have callouts to flush
  163                  * the buffer.  Otherwise we defer flushing; a 1/4 
  164                  * second is a guess.
  165                  */
  166                 if (c == '\n')
  167                         gdb_cnflush(gc);
  168                 else if (calloutok)
  169                         callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
  170         }
  171 }
  172 
  173 CONSOLE_DRIVER(gdb);
  174 
  175 /*
  176  * Our console device only gets attached if the system is booted
  177  * with RB_MULTIPLE set so gdb_init also calls us to attach the
  178  * console so we're setup regardless.
  179  */
  180 void
  181 gdb_consinit(void)
  182 {
  183         gdb_cnprobe(&gdb_consdev);
  184         gdb_cninit(&gdb_consdev);
  185         cnadd(&gdb_consdev);
  186 }

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