1/*-
2 * Copyright (c) 2007 Robert N. M. Watson
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 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27/*
28 * DDB capture support: capture kernel debugger output into a fixed-size
29 * buffer for later dumping to disk or extraction from user space.
30 */
31
32#include <sys/cdefs.h>
33__FBSDID("$FreeBSD$");
34
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, CTLFLAG_RW, 0,
84    "DDB capture options");
85
86SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD,
87    &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
88
89SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
90    &db_capture_maxbufsize, 0,
91    "Maximum value for debug.ddb.capture.bufsize");
92
93SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD,
94    &db_capture_inprogress, 0, "DDB output capture in progress");
95
96/*
97 * Boot-time allocation of the DDB capture buffer, if any.  Force all buffer
98 * sizes, including the maximum size, to be rounded to block sizes.
99 */
100static void
101db_capture_sysinit(__unused void *dummy)
102{
103
104	TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize);
105	db_capture_maxbufsize = roundup(db_capture_maxbufsize,
106	    TEXTDUMP_BLOCKSIZE);
107	db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE);
108	if (db_capture_bufsize > db_capture_maxbufsize)
109		db_capture_bufsize = db_capture_maxbufsize;
110	if (db_capture_bufsize != 0)
111		db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE,
112		    M_WAITOK);
113}
114SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit,
115    NULL);
116
117/*
118 * Run-time adjustment of the capture buffer.
119 */
120static int
121sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS)
122{
123	u_int len, size;
124	char *buf;
125	int error;
126
127	size = db_capture_bufsize;
128	error = sysctl_handle_int(oidp, &size, 0, req);
129	if (error || req->newptr == NULL)
130		return (error);
131	size = roundup(size, TEXTDUMP_BLOCKSIZE);
132	if (size > db_capture_maxbufsize)
133		return (EINVAL);
134	sx_xlock(&db_capture_sx);
135	if (size != 0) {
136		/*
137		 * Potentially the buffer is quite large, so if we can't
138		 * allocate it, fail rather than waiting.
139		 */
140		buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT);
141		if (buf == NULL) {
142			sx_xunlock(&db_capture_sx);
143			return (ENOMEM);
144		}
145		len = min(db_capture_bufoff, size);
146	} else {
147		buf = NULL;
148		len = 0;
149	}
150	if (db_capture_buf != NULL && buf != NULL)
151		bcopy(db_capture_buf, buf, len);
152	if (db_capture_buf != NULL)
153		free(db_capture_buf, M_DDB_CAPTURE);
154	db_capture_bufoff = len;
155	db_capture_buf = buf;
156	db_capture_bufsize = size;
157	sx_xunlock(&db_capture_sx);
158
159	KASSERT(db_capture_bufoff <= db_capture_bufsize,
160	    ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize"));
161	KASSERT(db_capture_bufsize <= db_capture_maxbufsize,
162	    ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize"));
163
164	return (0);
165}
166SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, CTLTYPE_UINT|CTLFLAG_RW,
167    0, 0, sysctl_debug_ddb_capture_bufsize, "IU",
168    "Size of DDB capture buffer");
169
170/*
171 * Sysctl to read out the capture buffer from userspace.  We require
172 * privilege as sensitive process/memory information may be accessed.
173 */
174static int
175sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS)
176{
177	int error;
178	char ch;
179
180	error = priv_check(req->td, PRIV_DDB_CAPTURE);
181	if (error)
182		return (error);
183
184	sx_slock(&db_capture_sx);
185	error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff);
186	sx_sunlock(&db_capture_sx);
187	if (error)
188		return (error);
189	ch = '\0';
190	return (SYSCTL_OUT(req, &ch, sizeof(ch)));
191}
192SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, CTLTYPE_STRING | CTLFLAG_RD,
193    NULL, 0, sysctl_debug_ddb_capture_data, "A", "DDB capture data");
194
195/*
196 * Routines for capturing DDB output into a fixed-size buffer.  These are
197 * invoked from DDB's input and output routines.  If we hit the limit on the
198 * buffer, we simply drop further data.
199 */
200void
201db_capture_write(char *buffer, u_int buflen)
202{
203	u_int len;
204
205	if (db_capture_inprogress == 0 || db_capture_inpager)
206		return;
207	len = min(buflen, db_capture_bufsize - db_capture_bufoff);
208	bcopy(buffer, db_capture_buf + db_capture_bufoff, len);
209	db_capture_bufoff += len;
210
211	KASSERT(db_capture_bufoff <= db_capture_bufsize,
212	    ("db_capture_write: bufoff > bufsize"));
213}
214
215void
216db_capture_writech(char ch)
217{
218
219	return (db_capture_write(&ch, sizeof(ch)));
220}
221
222void
223db_capture_enterpager(void)
224{
225
226	db_capture_inpager = 1;
227}
228
229void
230db_capture_exitpager(void)
231{
232
233	db_capture_inpager = 0;
234}
235
236/*
237 * Zero out any bytes left in the last block of the DDB capture buffer.  This
238 * is run shortly before writing the blocks to disk, rather than when output
239 * capture is stopped, in order to avoid injecting nul's into the middle of
240 * output.
241 */
242static void
243db_capture_zeropad(void)
244{
245	u_int len;
246
247	len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize -
248	    db_capture_bufoff) % TEXTDUMP_BLOCKSIZE);
249	bzero(db_capture_buf + db_capture_bufoff, len);
250	db_capture_bufpadding = len;
251}
252
253/*
254 * Reset capture state, which flushes buffers.
255 */
256static void
257db_capture_reset(void)
258{
259
260	db_capture_inprogress = 0;
261	db_capture_bufoff = 0;
262	db_capture_bufpadding = 0;
263}
264
265/*
266 * Start capture.  Only one session is allowed at any time, but we may
267 * continue a previous session, so the buffer isn't reset.
268 */
269static void
270db_capture_start(void)
271{
272
273	if (db_capture_inprogress) {
274		db_printf("Capture already started\n");
275		return;
276	}
277	db_capture_inprogress = 1;
278}
279
280/*
281 * Terminate DDB output capture--real work is deferred to db_capture_dump,
282 * which executes outside of the DDB context.  We don't zero pad here because
283 * capture may be started again before the dump takes place.
284 */
285static void
286db_capture_stop(void)
287{
288
289	if (db_capture_inprogress == 0) {
290		db_printf("Capture not started\n");
291		return;
292	}
293	db_capture_inprogress = 0;
294}
295
296/*
297 * Dump DDB(4) captured output (and resets capture buffers).
298 */
299void
300db_capture_dump(struct dumperinfo *di)
301{
302	u_int offset;
303
304	if (db_capture_bufoff == 0)
305		return;
306
307	db_capture_zeropad();
308	textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME,
309	    db_capture_bufoff);
310	(void)textdump_writenextblock(di, textdump_block_buffer);
311	for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding;
312	    offset += TEXTDUMP_BLOCKSIZE)
313		(void)textdump_writenextblock(di, db_capture_buf + offset);
314	db_capture_bufoff = 0;
315	db_capture_bufpadding = 0;
316}
317
318/*-
319 * DDB(4) command to manage capture:
320 *
321 * capture on          - start DDB output capture
322 * capture off         - stop DDB output capture
323 * capture reset       - reset DDB capture buffer (also stops capture)
324 * capture status      - print DDB output capture status
325 */
326static void
327db_capture_usage(void)
328{
329
330	db_error("capture [on|off|reset|status]\n");
331}
332
333void
334db_capture_cmd(db_expr_t addr, boolean_t have_addr, db_expr_t count,
335    char *modif)
336{
337	int t;
338
339	t = db_read_token();
340	if (t != tIDENT) {
341		db_capture_usage();
342		return;
343	}
344	if (db_read_token() != tEOL)
345		db_error("?\n");
346	if (strcmp(db_tok_string, "on") == 0)
347		db_capture_start();
348	else if (strcmp(db_tok_string, "off") == 0)
349		db_capture_stop();
350	else if (strcmp(db_tok_string, "reset") == 0)
351		db_capture_reset();
352	else if (strcmp(db_tok_string, "status") == 0) {
353		db_printf("%u/%u bytes used\n", db_capture_bufoff,
354		    db_capture_bufsize);
355		if (db_capture_inprogress)
356			db_printf("capture is on\n");
357		else
358			db_printf("capture is off\n");
359	} else
360		db_capture_usage();
361}
362