1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2007 Robert N. M. Watson
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 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29/*
30 * DDB capture support: capture kernel debugger output into a fixed-size
31 * buffer for later dumping to disk or extraction from user space.
32 */
33
34#include <sys/cdefs.h>
35__FBSDID("$FreeBSD$");
36
37#include "opt_ddb.h"
38
39#include <sys/param.h>
40#include <sys/conf.h>
41#include <sys/kernel.h>
42#include <sys/kerneldump.h>
43#include <sys/malloc.h>
44#include <sys/msgbuf.h>
45#include <sys/priv.h>
46#include <sys/sx.h>
47#include <sys/sysctl.h>
48#include <sys/systm.h>
49
50#include <ddb/ddb.h>
51#include <ddb/db_lex.h>
52
53/*
54 * While it would be desirable to use a small block-sized buffer and dump
55 * incrementally to disk in fixed-size blocks, it's not possible to enter
56 * kernel dumper routines without restarting the kernel, which is undesirable
57 * in the midst of debugging.  Instead, we maintain a large static global
58 * buffer that we fill from DDB's output routines.
59 *
60 * We enforce an invariant at runtime that buffer sizes are even multiples of
61 * the textdump block size, which is a design choice that we might want to
62 * reconsider.
63 */
64static MALLOC_DEFINE(M_DDB_CAPTURE, "ddb_capture", "DDB capture buffer");
65
66#ifndef DDB_CAPTURE_DEFAULTBUFSIZE
67#define	DDB_CAPTURE_DEFAULTBUFSIZE	48*1024
68#endif
69#ifndef DDB_CAPTURE_MAXBUFSIZE
70#define	DDB_CAPTURE_MAXBUFSIZE	5*1024*1024
71#endif
72#define	DDB_CAPTURE_FILENAME	"ddb.txt"	/* Captured DDB output. */
73
74static char *db_capture_buf;
75static u_int db_capture_bufsize = DDB_CAPTURE_DEFAULTBUFSIZE;
76static u_int db_capture_maxbufsize = DDB_CAPTURE_MAXBUFSIZE; /* Read-only. */
77static u_int db_capture_bufoff;		/* Next location to write in buffer. */
78static u_int db_capture_bufpadding;	/* Amount of zero padding. */
79static int db_capture_inpager;		/* Suspend capture in pager. */
80static int db_capture_inprogress;	/* DDB capture currently in progress. */
81
82struct sx db_capture_sx;		/* Lock against user thread races. */
83SX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx");
84
85static SYSCTL_NODE(_debug_ddb, OID_AUTO, capture,
86    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
87    "DDB capture options");
88
89SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD,
90    &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
91
92SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
93    &db_capture_maxbufsize, 0,
94    "Maximum value for debug.ddb.capture.bufsize");
95
96SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD,
97    &db_capture_inprogress, 0, "DDB output capture in progress");
98
99/*
100 * Boot-time allocation of the DDB capture buffer, if any.  Force all buffer
101 * sizes, including the maximum size, to be rounded to block sizes.
102 */
103static void
104db_capture_sysinit(__unused void *dummy)
105{
106
107	TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize);
108	db_capture_maxbufsize = roundup(db_capture_maxbufsize,
109	    TEXTDUMP_BLOCKSIZE);
110	db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE);
111	if (db_capture_bufsize > db_capture_maxbufsize)
112		db_capture_bufsize = db_capture_maxbufsize;
113	if (db_capture_bufsize != 0)
114		db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE,
115		    M_WAITOK);
116}
117SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit,
118    NULL);
119
120/*
121 * Run-time adjustment of the capture buffer.
122 */
123static int
124sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS)
125{
126	u_int len, size;
127	char *buf;
128	int error;
129
130	size = db_capture_bufsize;
131	error = sysctl_handle_int(oidp, &size, 0, req);
132	if (error || req->newptr == NULL)
133		return (error);
134	size = roundup(size, TEXTDUMP_BLOCKSIZE);
135	if (size > db_capture_maxbufsize)
136		return (EINVAL);
137	sx_xlock(&db_capture_sx);
138	if (size != 0) {
139		/*
140		 * Potentially the buffer is quite large, so if we can't
141		 * allocate it, fail rather than waiting.
142		 */
143		buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT);
144		if (buf == NULL) {
145			sx_xunlock(&db_capture_sx);
146			return (ENOMEM);
147		}
148		len = min(db_capture_bufoff, size);
149	} else {
150		buf = NULL;
151		len = 0;
152	}
153	if (db_capture_buf != NULL && buf != NULL)
154		bcopy(db_capture_buf, buf, len);
155	if (db_capture_buf != NULL)
156		free(db_capture_buf, M_DDB_CAPTURE);
157	db_capture_bufoff = len;
158	db_capture_buf = buf;
159	db_capture_bufsize = size;
160	sx_xunlock(&db_capture_sx);
161
162	KASSERT(db_capture_bufoff <= db_capture_bufsize,
163	    ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize"));
164	KASSERT(db_capture_bufsize <= db_capture_maxbufsize,
165	    ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize"));
166
167	return (0);
168}
169SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize,
170    CTLTYPE_UINT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
171    sysctl_debug_ddb_capture_bufsize, "IU",
172    "Size of DDB capture buffer");
173
174/*
175 * Sysctl to read out the capture buffer from userspace.  We require
176 * privilege as sensitive process/memory information may be accessed.
177 */
178static int
179sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS)
180{
181	int error;
182	char ch;
183
184	error = priv_check(req->td, PRIV_DDB_CAPTURE);
185	if (error)
186		return (error);
187
188	sx_slock(&db_capture_sx);
189	error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff);
190	sx_sunlock(&db_capture_sx);
191	if (error)
192		return (error);
193	ch = '\0';
194	return (SYSCTL_OUT(req, &ch, sizeof(ch)));
195}
196SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data,
197    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
198    sysctl_debug_ddb_capture_data, "A",
199    "DDB capture data");
200
201/*
202 * Routines for capturing DDB output into a fixed-size buffer.  These are
203 * invoked from DDB's input and output routines.  If we hit the limit on the
204 * buffer, we simply drop further data.
205 */
206void
207db_capture_write(char *buffer, u_int buflen)
208{
209	u_int len;
210
211	if (db_capture_inprogress == 0 || db_capture_inpager)
212		return;
213	len = min(buflen, db_capture_bufsize - db_capture_bufoff);
214	bcopy(buffer, db_capture_buf + db_capture_bufoff, len);
215	db_capture_bufoff += len;
216
217	KASSERT(db_capture_bufoff <= db_capture_bufsize,
218	    ("db_capture_write: bufoff > bufsize"));
219}
220
221void
222db_capture_writech(char ch)
223{
224
225	return (db_capture_write(&ch, sizeof(ch)));
226}
227
228void
229db_capture_enterpager(void)
230{
231
232	db_capture_inpager = 1;
233}
234
235void
236db_capture_exitpager(void)
237{
238
239	db_capture_inpager = 0;
240}
241
242/*
243 * Zero out any bytes left in the last block of the DDB capture buffer.  This
244 * is run shortly before writing the blocks to disk, rather than when output
245 * capture is stopped, in order to avoid injecting nul's into the middle of
246 * output.
247 */
248static void
249db_capture_zeropad(void)
250{
251	u_int len;
252
253	len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize -
254	    db_capture_bufoff) % TEXTDUMP_BLOCKSIZE);
255	bzero(db_capture_buf + db_capture_bufoff, len);
256	db_capture_bufpadding = len;
257}
258
259/*
260 * Reset capture state, which flushes buffers.
261 */
262static void
263db_capture_reset(void)
264{
265
266	db_capture_inprogress = 0;
267	db_capture_bufoff = 0;
268	db_capture_bufpadding = 0;
269}
270
271/*
272 * Start capture.  Only one session is allowed at any time, but we may
273 * continue a previous session, so the buffer isn't reset.
274 */
275static void
276db_capture_start(void)
277{
278
279	if (db_capture_inprogress) {
280		db_printf("Capture already started\n");
281		return;
282	}
283	db_capture_inprogress = 1;
284}
285
286/*
287 * Terminate DDB output capture--real work is deferred to db_capture_dump,
288 * which executes outside of the DDB context.  We don't zero pad here because
289 * capture may be started again before the dump takes place.
290 */
291static void
292db_capture_stop(void)
293{
294
295	if (db_capture_inprogress == 0) {
296		db_printf("Capture not started\n");
297		return;
298	}
299	db_capture_inprogress = 0;
300}
301
302/*
303 * Dump DDB(4) captured output (and resets capture buffers).
304 */
305void
306db_capture_dump(struct dumperinfo *di)
307{
308	u_int offset;
309
310	if (db_capture_bufoff == 0)
311		return;
312
313	db_capture_zeropad();
314	textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME,
315	    db_capture_bufoff);
316	(void)textdump_writenextblock(di, textdump_block_buffer);
317	for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding;
318	    offset += TEXTDUMP_BLOCKSIZE)
319		(void)textdump_writenextblock(di, db_capture_buf + offset);
320	db_capture_bufoff = 0;
321	db_capture_bufpadding = 0;
322}
323
324/*-
325 * DDB(4) command to manage capture:
326 *
327 * capture on          - start DDB output capture
328 * capture off         - stop DDB output capture
329 * capture reset       - reset DDB capture buffer (also stops capture)
330 * capture status      - print DDB output capture status
331 */
332static void
333db_capture_usage(void)
334{
335
336	db_error("capture [on|off|reset|status]\n");
337}
338
339void
340db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
341{
342	int t;
343
344	t = db_read_token();
345	if (t != tIDENT) {
346		db_capture_usage();
347		return;
348	}
349	if (db_read_token() != tEOL)
350		db_error("?\n");
351	if (strcmp(db_tok_string, "on") == 0)
352		db_capture_start();
353	else if (strcmp(db_tok_string, "off") == 0)
354		db_capture_stop();
355	else if (strcmp(db_tok_string, "reset") == 0)
356		db_capture_reset();
357	else if (strcmp(db_tok_string, "status") == 0) {
358		db_printf("%u/%u bytes used\n", db_capture_bufoff,
359		    db_capture_bufsize);
360		if (db_capture_inprogress)
361			db_printf("capture is on\n");
362		else
363			db_printf("capture is off\n");
364	} else
365		db_capture_usage();
366}
367