gdb_cons.c revision 256281 
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: stable/10/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
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 void
91gdb_cngrab(struct consdev *cp)
92{
93}
94
95static void
96gdb_cnungrab(struct consdev *cp)
97{
98}
99
100static int
101gdb_cngetc(struct consdev *cp)
102{
103	return -1;
104}
105
106static void
107gdb_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
115static void
116gdb_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 */
133static int calloutok = 0;
134static void
135oktousecallout(void *data __unused)
136{
137	calloutok = 1;
138}
139SYSINIT(gdbhack, SI_SUB_LAST, SI_ORDER_MIDDLE, oktousecallout, NULL);
140
141static void
142gdb_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
172CONSOLE_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 */
179void
180gdb_consinit(void)
181{
182	gdb_cnprobe(&gdb_consdev);
183	gdb_cninit(&gdb_consdev);
184	cnadd(&gdb_consdev);
185}
186