1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
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#include "opt_ddb.h"
36
37#include <sys/param.h>
38#include <sys/conf.h>
39#include <sys/kernel.h>
40#include <sys/kerneldump.h>
41#include <sys/malloc.h>
42#include <sys/msgbuf.h>
43#include <sys/priv.h>
44#include <sys/sx.h>
45#include <sys/sysctl.h>
46#include <sys/systm.h>
47
48#include <ddb/ddb.h>
49#include <ddb/db_lex.h>
50
51/*
52 * While it would be desirable to use a small block-sized buffer and dump
53 * incrementally to disk in fixed-size blocks, it's not possible to enter
54 * kernel dumper routines without restarting the kernel, which is undesirable
55 * in the midst of debugging.  Instead, we maintain a large static global
56 * buffer that we fill from DDB's output routines.
57 *
58 * We enforce an invariant at runtime that buffer sizes are even multiples of
59 * the textdump block size, which is a design choice that we might want to
60 * reconsider.
61 */
62static MALLOC_DEFINE(M_DDB_CAPTURE, "ddb_capture", "DDB capture buffer");
63
64#ifndef DDB_CAPTURE_DEFAULTBUFSIZE
65#define	DDB_CAPTURE_DEFAULTBUFSIZE	48*1024
66#endif
67#ifndef DDB_CAPTURE_MAXBUFSIZE
68#define	DDB_CAPTURE_MAXBUFSIZE	5*1024*1024
69#endif
70#define	DDB_CAPTURE_FILENAME	"ddb.txt"	/* Captured DDB output. */
71
72static char *db_capture_buf;
73static u_int db_capture_bufsize = DDB_CAPTURE_DEFAULTBUFSIZE;
74static u_int db_capture_maxbufsize = DDB_CAPTURE_MAXBUFSIZE; /* Read-only. */
75static u_int db_capture_bufoff;		/* Next location to write in buffer. */
76static u_int db_capture_bufpadding;	/* Amount of zero padding. */
77static int db_capture_inpager;		/* Suspend capture in pager. */
78static int db_capture_inprogress;	/* DDB capture currently in progress. */
79
80struct sx db_capture_sx;		/* Lock against user thread races. */
81SX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx");
82
83static SYSCTL_NODE(_debug_ddb, OID_AUTO, capture,
84    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
85    "DDB capture options");
86
87SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD,
88    &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
89
90SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
91    &db_capture_maxbufsize, 0,
92    "Maximum value for debug.ddb.capture.bufsize");
93
94SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD,
95    &db_capture_inprogress, 0, "DDB output capture in progress");
96
97/*
98 * Boot-time allocation of the DDB capture buffer, if any.  Force all buffer
99 * sizes, including the maximum size, to be rounded to block sizes.
100 */
101static void
102db_capture_sysinit(__unused void *dummy)
103{
104
105	TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize);
106	db_capture_maxbufsize = roundup(db_capture_maxbufsize,
107	    TEXTDUMP_BLOCKSIZE);
108	db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE);
109	if (db_capture_bufsize > db_capture_maxbufsize)
110		db_capture_bufsize = db_capture_maxbufsize;
111	if (db_capture_bufsize != 0)
112		db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE,
113		    M_WAITOK);
114}
115SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit,
116    NULL);
117
118/*
119 * Run-time adjustment of the capture buffer.
120 */
121static int
122sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS)
123{
124	u_int len, size;
125	char *buf;
126	int error;
127
128	size = db_capture_bufsize;
129	error = sysctl_handle_int(oidp, &size, 0, req);
130	if (error || req->newptr == NULL)
131		return (error);
132	size = roundup(size, TEXTDUMP_BLOCKSIZE);
133	if (size > db_capture_maxbufsize)
134		return (EINVAL);
135	sx_xlock(&db_capture_sx);
136	if (size != 0) {
137		/*
138		 * Potentially the buffer is quite large, so if we can't
139		 * allocate it, fail rather than waiting.
140		 */
141		buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT);
142		if (buf == NULL) {
143			sx_xunlock(&db_capture_sx);
144			return (ENOMEM);
145		}
146		len = min(db_capture_bufoff, size);
147	} else {
148		buf = NULL;
149		len = 0;
150	}
151	if (db_capture_buf != NULL && buf != NULL)
152		bcopy(db_capture_buf, buf, len);
153	if (db_capture_buf != NULL)
154		free(db_capture_buf, M_DDB_CAPTURE);
155	db_capture_bufoff = len;
156	db_capture_buf = buf;
157	db_capture_bufsize = size;
158	sx_xunlock(&db_capture_sx);
159
160	KASSERT(db_capture_bufoff <= db_capture_bufsize,
161	    ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize"));
162	KASSERT(db_capture_bufsize <= db_capture_maxbufsize,
163	    ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize"));
164
165	return (0);
166}
167SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize,
168    CTLTYPE_UINT | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE,
169    0, 0, sysctl_debug_ddb_capture_bufsize, "IU",
170    "Size of DDB capture buffer");
171
172/*
173 * Sysctl to read out the capture buffer from userspace.  We require
174 * privilege as sensitive process/memory information may be accessed.
175 */
176static int
177sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS)
178{
179	int error;
180	char ch;
181
182	error = priv_check(req->td, PRIV_DDB_CAPTURE);
183	if (error)
184		return (error);
185
186	sx_slock(&db_capture_sx);
187	error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff);
188	sx_sunlock(&db_capture_sx);
189	if (error)
190		return (error);
191	ch = '\0';
192	return (SYSCTL_OUT(req, &ch, sizeof(ch)));
193}
194SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data,
195    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
196    sysctl_debug_ddb_capture_data, "A",
197    "DDB capture data");
198
199/*
200 * Routines for capturing DDB output into a fixed-size buffer.  These are
201 * invoked from DDB's input and output routines.  If we hit the limit on the
202 * buffer, we simply drop further data.
203 */
204void
205db_capture_write(char *buffer, u_int buflen)
206{
207	u_int len;
208
209	if (db_capture_inprogress == 0 || db_capture_inpager)
210		return;
211	len = min(buflen, db_capture_bufsize - db_capture_bufoff);
212	bcopy(buffer, db_capture_buf + db_capture_bufoff, len);
213	db_capture_bufoff += len;
214
215	KASSERT(db_capture_bufoff <= db_capture_bufsize,
216	    ("db_capture_write: bufoff > bufsize"));
217}
218
219void
220db_capture_writech(char ch)
221{
222
223	return (db_capture_write(&ch, sizeof(ch)));
224}
225
226void
227db_capture_enterpager(void)
228{
229
230	db_capture_inpager = 1;
231}
232
233void
234db_capture_exitpager(void)
235{
236
237	db_capture_inpager = 0;
238}
239
240/*
241 * Zero out any bytes left in the last block of the DDB capture buffer.  This
242 * is run shortly before writing the blocks to disk, rather than when output
243 * capture is stopped, in order to avoid injecting nul's into the middle of
244 * output.
245 */
246static void
247db_capture_zeropad(void)
248{
249	u_int len;
250
251	len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize -
252	    db_capture_bufoff) % TEXTDUMP_BLOCKSIZE);
253	bzero(db_capture_buf + db_capture_bufoff, len);
254	db_capture_bufpadding = len;
255}
256
257/*
258 * Reset capture state, which flushes buffers.
259 */
260static void
261db_capture_reset(void)
262{
263
264	db_capture_inprogress = 0;
265	db_capture_bufoff = 0;
266	db_capture_bufpadding = 0;
267}
268
269/*
270 * Start capture.  Only one session is allowed at any time, but we may
271 * continue a previous session, so the buffer isn't reset.
272 */
273static void
274db_capture_start(void)
275{
276
277	if (db_capture_inprogress) {
278		db_printf("Capture already started\n");
279		return;
280	}
281	db_capture_inprogress = 1;
282}
283
284/*
285 * Terminate DDB output capture--real work is deferred to db_capture_dump,
286 * which executes outside of the DDB context.  We don't zero pad here because
287 * capture may be started again before the dump takes place.
288 */
289static void
290db_capture_stop(void)
291{
292
293	if (db_capture_inprogress == 0) {
294		db_printf("Capture not started\n");
295		return;
296	}
297	db_capture_inprogress = 0;
298}
299
300/*
301 * Dump DDB(4) captured output (and resets capture buffers).
302 */
303void
304db_capture_dump(struct dumperinfo *di)
305{
306	u_int offset;
307
308	if (db_capture_bufoff == 0)
309		return;
310
311	db_capture_zeropad();
312	textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME,
313	    db_capture_bufoff);
314	(void)textdump_writenextblock(di, textdump_block_buffer);
315	for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding;
316	    offset += TEXTDUMP_BLOCKSIZE)
317		(void)textdump_writenextblock(di, db_capture_buf + offset);
318	db_capture_bufoff = 0;
319	db_capture_bufpadding = 0;
320}
321
322/*-
323 * DDB(4) command to manage capture:
324 *
325 * capture on          - start DDB output capture
326 * capture off         - stop DDB output capture
327 * capture reset       - reset DDB capture buffer (also stops capture)
328 * capture status      - print DDB output capture status
329 */
330static void
331db_capture_usage(void)
332{
333
334	db_error("capture [on|off|reset|status]\n");
335}
336
337void
338db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
339{
340	int t;
341
342	t = db_read_token();
343	if (t != tIDENT) {
344		db_capture_usage();
345		return;
346	}
347	if (db_read_token() != tEOL)
348		db_error("?\n");
349	if (strcmp(db_tok_string, "on") == 0)
350		db_capture_start();
351	else if (strcmp(db_tok_string, "off") == 0)
352		db_capture_stop();
353	else if (strcmp(db_tok_string, "reset") == 0)
354		db_capture_reset();
355	else if (strcmp(db_tok_string, "status") == 0) {
356		db_printf("%u/%u bytes used\n", db_capture_bufoff,
357		    db_capture_bufsize);
358		if (db_capture_inprogress)
359			db_printf("capture is on\n");
360		else
361			db_printf("capture is off\n");
362	} else
363		db_capture_usage();
364}
365