FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_capture.c
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 */
64 static 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
74 static char *db_capture_buf;
75 static u_int db_capture_bufsize = DDB_CAPTURE_DEFAULTBUFSIZE;
76 static u_int db_capture_maxbufsize = DDB_CAPTURE_MAXBUFSIZE; /* Read-only. */
77 static u_int db_capture_bufoff; /* Next location to write in buffer. */
78 static u_int db_capture_bufpadding; /* Amount of zero padding. */
79 static int db_capture_inpager; /* Suspend capture in pager. */
80 static int db_capture_inprogress; /* DDB capture currently in progress. */
81
82 struct sx db_capture_sx; /* Lock against user thread races. */
83 SX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx");
84
85 static SYSCTL_NODE(_debug_ddb, OID_AUTO, capture,
86 CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
87 "DDB capture options");
88
89 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD,
90 &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
91
92 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
93 &db_capture_maxbufsize, 0,
94 "Maximum value for debug.ddb.capture.bufsize");
95
96 SYSCTL_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 */
103 static void
104 db_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 }
117 SYSINIT(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 */
123 static int
124 sysctl_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 }
169 SYSCTL_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 */
178 static int
179 sysctl_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 }
196 SYSCTL_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 */
206 void
207 db_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
221 void
222 db_capture_writech(char ch)
223 {
224
225 return (db_capture_write(&ch, sizeof(ch)));
226 }
227
228 void
229 db_capture_enterpager(void)
230 {
231
232 db_capture_inpager = 1;
233 }
234
235 void
236 db_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 */
248 static void
249 db_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 */
262 static void
263 db_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 */
275 static void
276 db_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 */
291 static void
292 db_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 */
305 void
306 db_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 */
332 static void
333 db_capture_usage(void)
334 {
335
336 db_error("capture [on|off|reset|status]\n");
337 }
338
339 void
340 db_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 }
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