1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2006 Sam Leffler
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/*
30 * Support for redirecting console msgs to gdb.  We register
31 * a pseudo console to hook cnputc and send stuff to the gdb
32 * port.  The only trickiness here is buffering output so this
33 * isn't dog slow.
34 */
35
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD$");
38
39#include <sys/param.h>
40#include <sys/systm.h>
41#include <sys/cons.h>
42#include <sys/kdb.h>
43#include <sys/kernel.h>
44#include <sys/malloc.h>
45#include <sys/reboot.h>
46#include <sys/sysctl.h>
47
48#include <machine/gdb_machdep.h>
49#include <machine/kdb.h>
50
51#include <gdb/gdb.h>
52#include <gdb/gdb_int.h>
53
54struct gdbcons {
55	int	npending;
56	/* /2 for hex conversion, -6 for protocol glue */
57	char	buf[GDB_BUFSZ/2 - 6];
58	struct callout flush;
59};
60static struct gdbcons state = { -1 };
61
62static	int gdbcons_enable = 0;
63SYSCTL_INT(_debug_gdb, OID_AUTO, cons, CTLFLAG_RWTUN, &gdbcons_enable, 0,
64	"copy console messages to GDB");
65/* Legacy sysctl alias */
66SYSCTL_INT(_debug, OID_AUTO, gdbcons, CTLFLAG_RWTUN, &gdbcons_enable,
67	0, "copy console messages to GDB");
68
69static void
70gdb_cnprobe(struct consdev *cp)
71{
72	sprintf(cp->cn_name, "gdb");
73	cp->cn_pri = CN_LOW;		/* XXX no way to say "write only" */
74}
75
76static void
77gdb_cninit(struct consdev *cp)
78{
79	struct gdbcons *c = &state;
80
81	/* setup tx buffer and callout */
82	if (c->npending == -1) {
83		c->npending = 0;
84		callout_init(&c->flush, 1);
85		cp->cn_arg = c;
86	}
87}
88
89static void
90gdb_cnterm(struct consdev *cp)
91{
92}
93
94static void
95gdb_cngrab(struct consdev *cp)
96{
97}
98
99static void
100gdb_cnungrab(struct consdev *cp)
101{
102}
103
104static int
105gdb_cngetc(struct consdev *cp)
106{
107	return -1;
108}
109
110static void
111gdb_tx_puthex(int c)
112{
113	const char *hex = "0123456789abcdef";
114
115	gdb_tx_char(hex[(c>>4)&0xf]);
116	gdb_tx_char(hex[(c>>0)&0xf]);
117}
118
119static void
120gdb_cnflush(void *arg)
121{
122	struct gdbcons *gc = arg;
123	int i;
124
125	gdb_tx_begin('O');
126	for (i = 0; i < gc->npending; i++)
127		gdb_tx_puthex(gc->buf[i]);
128	gdb_tx_end();
129	gc->npending = 0;
130}
131
132/*
133 * This glop is to figure out when it's safe to use callouts
134 * to defer buffer flushing.  There's probably a better way
135 * and/or an earlier point in the boot process when it's ok.
136 */
137static int calloutok = 0;
138static void
139oktousecallout(void *data __unused)
140{
141	calloutok = 1;
142}
143SYSINIT(gdbhack, SI_SUB_LAST, SI_ORDER_MIDDLE, oktousecallout, NULL);
144
145static void
146gdb_cnputc(struct consdev *cp, int c)
147{
148	struct gdbcons *gc;
149
150	if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
151		gc = cp->cn_arg;
152		if (gc->npending != 0) {
153			/*
154			 * Cancel any pending callout and flush the
155			 * buffer if there's no space for this byte.
156			 */
157			if (calloutok)
158				callout_stop(&gc->flush);
159			if (gc->npending == sizeof(gc->buf))
160				gdb_cnflush(gc);
161		}
162		gc->buf[gc->npending++] = c;
163		/*
164		 * Flush on end of line; this is especially helpful
165		 * during boot when we don't have callouts to flush
166		 * the buffer.  Otherwise we defer flushing; a 1/4
167		 * second is a guess.
168		 */
169		if (c == '\n')
170			gdb_cnflush(gc);
171		else if (calloutok)
172			callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
173	}
174}
175
176CONSOLE_DRIVER(gdb);
177
178/*
179 * Our console device only gets attached if the system is booted
180 * with RB_MULTIPLE set so gdb_init also calls us to attach the
181 * console so we're setup regardless.
182 */
183void
184gdb_consinit(void)
185{
186	gdb_cnprobe(&gdb_consdev);
187	gdb_cninit(&gdb_consdev);
188	cnadd(&gdb_consdev);
189}
190