gdb_cons.c revision 177255 
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 177255 2008-03-16 13:02:04Z rwatson $");
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 void
86gdb_cnterm(struct consdev *cp)
87{
88}
89
90static int
91gdb_cngetc(struct consdev *cp)
92{
93	return -1;
94}
95
96static void
97gdb_tx_puthex(int c)
98{
99	const char *hex = "0123456789abcdef";
100
101	gdb_tx_char(hex[(c>>4)&0xf]);
102	gdb_tx_char(hex[(c>>0)&0xf]);
103}
104
105static void
106gdb_cnflush(void *arg)
107{
108	struct gdbcons *gc = arg;
109	int i;
110
111	gdb_tx_begin('O');
112	for (i = 0; i < gc->npending; i++)
113		gdb_tx_puthex(gc->buf[i]);
114	gdb_tx_end();
115	gc->npending = 0;
116}
117
118/*
119 * This glop is to figure out when it's safe to use callouts
120 * to defer buffer flushing.  There's probably a better way
121 * and/or an earlier point in the boot process when it's ok.
122 */
123static int calloutok = 0;
124static void
125oktousecallout(void *data __unused)
126{
127	calloutok = 1;
128}
129SYSINIT(gdbhack, SI_SUB_RUN_SCHEDULER, SI_ORDER_ANY, oktousecallout, NULL);
130
131static void
132gdb_cnputc(struct consdev *cp, int c)
133{
134	struct gdbcons *gc;
135
136	if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
137		gc = cp->cn_arg;
138		if (gc->npending != 0) {
139			/*
140			 * Cancel any pending callout and flush the
141			 * buffer if there's no space for this byte.
142			 */
143			if (calloutok)
144				callout_stop(&gc->flush);
145			if (gc->npending == sizeof(gc->buf))
146				gdb_cnflush(gc);
147		}
148		gc->buf[gc->npending++] = c;
149		/*
150		 * Flush on end of line; this is especially helpful
151		 * during boot when we don't have callouts to flush
152		 * the buffer.  Otherwise we defer flushing; a 1/4
153		 * second is a guess.
154		 */
155		if (c == '\n')
156			gdb_cnflush(gc);
157		else if (calloutok)
158			callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
159	}
160}
161
162CONSOLE_DRIVER(gdb);
163
164/*
165 * Our console device only gets attached if the system is booted
166 * with RB_MULTIPLE set so gdb_init also calls us to attach the
167 * console so we're setup regardless.
168 */
169void
170gdb_consinit(void)
171{
172	gdb_cnprobe(&gdb_consdev);
173	gdb_cninit(&gdb_consdev);
174	cnadd(&gdb_consdev);
175}
176