gdb_cons.c revision 157059 
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: head/sys/gdb/gdb_cons.c 157059 2006-03-23 23:06:14Z sam $");
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
52struct 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};
58static struct gdbcons state = { -1 };
59
60static	int gdbcons_enable = 0;
61SYSCTL_INT(_debug, OID_AUTO, gdbcons, CTLFLAG_RW, &gdbcons_enable,
62	    0, "copy console messages to gdb");
63TUNABLE_INT("debug.gdbcons", &gdbcons_enable);
64
65static void
66gdb_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
72static void
73gdb_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
85static int
86gdb_nogetc(struct consdev *cp)
87{
88	return -1;
89}
90
91static void
92gdb_tx_puthex(int c)
93{
94	const char *hex = "0123456789abcdef";
95
96	gdb_tx_char(hex[(c>>4)&0xf]);
97	gdb_tx_char(hex[(c>>0)&0xf]);
98}
99
100static void
101gdb_cnflush(void *arg)
102{
103	struct gdbcons *gc = arg;
104	int i;
105
106	gdb_tx_begin('O');
107	for (i = 0; i < gc->npending; i++)
108		gdb_tx_puthex(gc->buf[i]);
109	gdb_tx_end();
110	gc->npending = 0;
111}
112
113/*
114 * This glop is to figure out when it's safe to use callouts
115 * to defer buffer flushing.  There's probably a better way
116 * and/or an earlier point in the boot process when it's ok.
117 */
118static int calloutok = 0;
119static void
120oktousecallout(void *data __unused)
121{
122	calloutok = 1;
123}
124SYSINIT(gdbhack, SI_SUB_RUN_SCHEDULER, SI_ORDER_ANY, oktousecallout, NULL)
125
126static void
127gdb_cnputc(struct consdev *cp, int c)
128{
129	struct gdbcons *gc;
130
131	if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
132		gc = cp->cn_arg;
133		if (gc->npending != 0) {
134			/*
135			 * Cancel any pending callout and flush the
136			 * buffer if there's no space for this byte.
137			 */
138			if (calloutok)
139				callout_stop(&gc->flush);
140			if (gc->npending == sizeof(gc->buf))
141				gdb_cnflush(gc);
142		}
143		gc->buf[gc->npending++] = c;
144		/*
145		 * Flush on end of line; this is especially helpful
146		 * during boot when we don't have callouts to flush
147		 * the buffer.  Otherwise we defer flushing; a 1/4
148		 * second is a guess.
149		 */
150		if (c == '\n')
151			gdb_cnflush(gc);
152		else if (calloutok)
153			callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
154	}
155}
156
157/* NB: no get interface, we supply nogetc for checkc too */
158CONS_DRIVER(gdb, gdb_cnprobe, gdb_cninit, NULL, gdb_nogetc, gdb_nogetc,
159	gdb_cnputc, NULL);
160
161/*
162 * Our console device only gets attached if the system is booted
163 * with RB_MULTIPLE set so gdb_init also calls us to attach the
164 * console so we're setup regardless.
165 */
166void
167gdb_consinit(void)
168{
169	gdb_cnprobe(&gdb_consdev);
170	gdb_cninit(&gdb_consdev);
171	cnadd(&gdb_consdev);
172}
173