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/10.2/sys/gdb/gdb_cons.c 253604 2013-07-24 09:45:31Z avg $");
   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_RW, &gdbcons_enable,
   62             0, "copy console messages to gdb");
   63 TUNABLE_INT("debug.gdbcons", &gdbcons_enable);
   64 
   65 static void
   66 gdb_cnprobe(struct consdev *cp)
   67 {
   68         sprintf(cp->cn_name, "gdb");
   69         cp->cn_pri = CN_LOW;            /* XXX no way to say "write only" */
   70 }
   71 
   72 static void
   73 gdb_cninit(struct consdev *cp)
   74 {
   75         struct gdbcons *c = &state;
   76 
   77         /* setup tx buffer and callout */
   78         if (c->npending == -1) {
   79                 c->npending = 0;
   80                 callout_init(&c->flush, CALLOUT_MPSAFE);
   81                 cp->cn_arg = c;
   82         }
   83 }
   84 
   85 static void
   86 gdb_cnterm(struct consdev *cp)
   87 {
   88 }
   89 
   90 static void
   91 gdb_cngrab(struct consdev *cp)
   92 {
   93 }
   94 
   95 static void
   96 gdb_cnungrab(struct consdev *cp)
   97 {
   98 }
   99 
  100 static int
  101 gdb_cngetc(struct consdev *cp)
  102 {
  103         return -1;
  104 }
  105 
  106 static void
  107 gdb_tx_puthex(int c)
  108 {
  109         const char *hex = "0123456789abcdef";
  110 
  111         gdb_tx_char(hex[(c>>4)&0xf]);
  112         gdb_tx_char(hex[(c>>0)&0xf]);
  113 }
  114 
  115 static void
  116 gdb_cnflush(void *arg)
  117 {
  118         struct gdbcons *gc = arg;
  119         int i;
  120 
  121         gdb_tx_begin('O');
  122         for (i = 0; i < gc->npending; i++)
  123                 gdb_tx_puthex(gc->buf[i]);
  124         gdb_tx_end();
  125         gc->npending = 0;
  126 }
  127 
  128 /*
  129  * This glop is to figure out when it's safe to use callouts
  130  * to defer buffer flushing.  There's probably a better way
  131  * and/or an earlier point in the boot process when it's ok.
  132  */
  133 static int calloutok = 0;
  134 static void
  135 oktousecallout(void *data __unused)
  136 {
  137         calloutok = 1;
  138 }
  139 SYSINIT(gdbhack, SI_SUB_LAST, SI_ORDER_MIDDLE, oktousecallout, NULL);
  140 
  141 static void
  142 gdb_cnputc(struct consdev *cp, int c)
  143 {
  144         struct gdbcons *gc;
  145 
  146         if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
  147                 gc = cp->cn_arg;
  148                 if (gc->npending != 0) {
  149                         /*
  150                          * Cancel any pending callout and flush the
  151                          * buffer if there's no space for this byte.
  152                          */
  153                         if (calloutok)
  154                                 callout_stop(&gc->flush);
  155                         if (gc->npending == sizeof(gc->buf))
  156                                 gdb_cnflush(gc);
  157                 }
  158                 gc->buf[gc->npending++] = c;
  159                 /*
  160                  * Flush on end of line; this is especially helpful
  161                  * during boot when we don't have callouts to flush
  162                  * the buffer.  Otherwise we defer flushing; a 1/4 
  163                  * second is a guess.
  164                  */
  165                 if (c == '\n')
  166                         gdb_cnflush(gc);
  167                 else if (calloutok)
  168                         callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
  169         }
  170 }
  171 
  172 CONSOLE_DRIVER(gdb);
  173 
  174 /*
  175  * Our console device only gets attached if the system is booted
  176  * with RB_MULTIPLE set so gdb_init also calls us to attach the
  177  * console so we're setup regardless.
  178  */
  179 void
  180 gdb_consinit(void)
  181 {
  182         gdb_cnprobe(&gdb_consdev);
  183         gdb_cninit(&gdb_consdev);
  184         cnadd(&gdb_consdev);
  185 }

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