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  * Copyright (c) 2006 Sam Leffler
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  *
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
   16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   18  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   25  */
   26 
   27 /* 
   28  * Support for redirecting console msgs to gdb.  We register
   29  * a pseudo console to hook cnputc and send stuff to the gdb
   30  * port.  The only trickiness here is buffering output so this
   31  * isn't dog slow.
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/11.2/sys/gdb/gdb_cons.c 283291 2015-05-22 17:05:21Z jkim $");
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/cons.h>
   40 #include <sys/kdb.h>
   41 #include <sys/kernel.h>
   42 #include <sys/malloc.h>
   43 #include <sys/reboot.h>
   44 #include <sys/sysctl.h>
   45 
   46 #include <machine/gdb_machdep.h>
   47 #include <machine/kdb.h>
   48 
   49 #include <gdb/gdb.h>
   50 #include <gdb/gdb_int.h>
   51 
   52 struct gdbcons {
   53         int     npending;
   54         /* /2 for hex conversion, -6 for protocol glue */
   55         char    buf[GDB_BUFSZ/2 - 6];
   56         struct callout flush;
   57 };
   58 static struct gdbcons state = { -1 };
   59 
   60 static  int gdbcons_enable = 0;
   61 SYSCTL_INT(_debug, OID_AUTO, gdbcons, CTLFLAG_RWTUN, &gdbcons_enable,
   62             0, "copy console messages to GDB");
   63 
   64 static void
   65 gdb_cnprobe(struct consdev *cp)
   66 {
   67         sprintf(cp->cn_name, "gdb");
   68         cp->cn_pri = CN_LOW;            /* XXX no way to say "write only" */
   69 }
   70 
   71 static void
   72 gdb_cninit(struct consdev *cp)
   73 {
   74         struct gdbcons *c = &state;
   75 
   76         /* setup tx buffer and callout */
   77         if (c->npending == -1) {
   78                 c->npending = 0;
   79                 callout_init(&c->flush, 1);
   80                 cp->cn_arg = c;
   81         }
   82 }
   83 
   84 static void
   85 gdb_cnterm(struct consdev *cp)
   86 {
   87 }
   88 
   89 static void
   90 gdb_cngrab(struct consdev *cp)
   91 {
   92 }
   93 
   94 static void
   95 gdb_cnungrab(struct consdev *cp)
   96 {
   97 }
   98 
   99 static int
  100 gdb_cngetc(struct consdev *cp)
  101 {
  102         return -1;
  103 }
  104 
  105 static void
  106 gdb_tx_puthex(int c)
  107 {
  108         const char *hex = "0123456789abcdef";
  109 
  110         gdb_tx_char(hex[(c>>4)&0xf]);
  111         gdb_tx_char(hex[(c>>0)&0xf]);
  112 }
  113 
  114 static void
  115 gdb_cnflush(void *arg)
  116 {
  117         struct gdbcons *gc = arg;
  118         int i;
  119 
  120         gdb_tx_begin('O');
  121         for (i = 0; i < gc->npending; i++)
  122                 gdb_tx_puthex(gc->buf[i]);
  123         gdb_tx_end();
  124         gc->npending = 0;
  125 }
  126 
  127 /*
  128  * This glop is to figure out when it's safe to use callouts
  129  * to defer buffer flushing.  There's probably a better way
  130  * and/or an earlier point in the boot process when it's ok.
  131  */
  132 static int calloutok = 0;
  133 static void
  134 oktousecallout(void *data __unused)
  135 {
  136         calloutok = 1;
  137 }
  138 SYSINIT(gdbhack, SI_SUB_LAST, SI_ORDER_MIDDLE, oktousecallout, NULL);
  139 
  140 static void
  141 gdb_cnputc(struct consdev *cp, int c)
  142 {
  143         struct gdbcons *gc;
  144 
  145         if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
  146                 gc = cp->cn_arg;
  147                 if (gc->npending != 0) {
  148                         /*
  149                          * Cancel any pending callout and flush the
  150                          * buffer if there's no space for this byte.
  151                          */
  152                         if (calloutok)
  153                                 callout_stop(&gc->flush);
  154                         if (gc->npending == sizeof(gc->buf))
  155                                 gdb_cnflush(gc);
  156                 }
  157                 gc->buf[gc->npending++] = c;
  158                 /*
  159                  * Flush on end of line; this is especially helpful
  160                  * during boot when we don't have callouts to flush
  161                  * the buffer.  Otherwise we defer flushing; a 1/4 
  162                  * second is a guess.
  163                  */
  164                 if (c == '\n')
  165                         gdb_cnflush(gc);
  166                 else if (calloutok)
  167                         callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
  168         }
  169 }
  170 
  171 CONSOLE_DRIVER(gdb);
  172 
  173 /*
  174  * Our console device only gets attached if the system is booted
  175  * with RB_MULTIPLE set so gdb_init also calls us to attach the
  176  * console so we're setup regardless.
  177  */
  178 void
  179 gdb_consinit(void)
  180 {
  181         gdb_cnprobe(&gdb_consdev);
  182         gdb_cninit(&gdb_consdev);
  183         cnadd(&gdb_consdev);
  184 }

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