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, CTLFLAG_RW, 0,
86 "DDB capture options");
87
88 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD,
89 &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
90
91 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
92 &db_capture_maxbufsize, 0,
93 "Maximum value for debug.ddb.capture.bufsize");
94
95 SYSCTL_INT(_debug_ddb_capture, OID_AUTO, inprogress, CTLFLAG_RD,
96 &db_capture_inprogress, 0, "DDB output capture in progress");
97
98 /*
99 * Boot-time allocation of the DDB capture buffer, if any. Force all buffer
100 * sizes, including the maximum size, to be rounded to block sizes.
101 */
102 static void
103 db_capture_sysinit(__unused void *dummy)
104 {
105
106 TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize);
107 db_capture_maxbufsize = roundup(db_capture_maxbufsize,
108 TEXTDUMP_BLOCKSIZE);
109 db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE);
110 if (db_capture_bufsize > db_capture_maxbufsize)
111 db_capture_bufsize = db_capture_maxbufsize;
112 if (db_capture_bufsize != 0)
113 db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE,
114 M_WAITOK);
115 }
116 SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit,
117 NULL);
118
119 /*
120 * Run-time adjustment of the capture buffer.
121 */
122 static int
123 sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS)
124 {
125 u_int len, size;
126 char *buf;
127 int error;
128
129 size = db_capture_bufsize;
130 error = sysctl_handle_int(oidp, &size, 0, req);
131 if (error || req->newptr == NULL)
132 return (error);
133 size = roundup(size, TEXTDUMP_BLOCKSIZE);
134 if (size > db_capture_maxbufsize)
135 return (EINVAL);
136 sx_xlock(&db_capture_sx);
137 if (size != 0) {
138 /*
139 * Potentially the buffer is quite large, so if we can't
140 * allocate it, fail rather than waiting.
141 */
142 buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT);
143 if (buf == NULL) {
144 sx_xunlock(&db_capture_sx);
145 return (ENOMEM);
146 }
147 len = min(db_capture_bufoff, size);
148 } else {
149 buf = NULL;
150 len = 0;
151 }
152 if (db_capture_buf != NULL && buf != NULL)
153 bcopy(db_capture_buf, buf, len);
154 if (db_capture_buf != NULL)
155 free(db_capture_buf, M_DDB_CAPTURE);
156 db_capture_bufoff = len;
157 db_capture_buf = buf;
158 db_capture_bufsize = size;
159 sx_xunlock(&db_capture_sx);
160
161 KASSERT(db_capture_bufoff <= db_capture_bufsize,
162 ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize"));
163 KASSERT(db_capture_bufsize <= db_capture_maxbufsize,
164 ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize"));
165
166 return (0);
167 }
168 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, CTLTYPE_UINT|CTLFLAG_RW,
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 */
176 static int
177 sysctl_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 }
194 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, CTLTYPE_STRING | CTLFLAG_RD,
195 NULL, 0, sysctl_debug_ddb_capture_data, "A", "DDB capture data");
196
197 /*
198 * Routines for capturing DDB output into a fixed-size buffer. These are
199 * invoked from DDB's input and output routines. If we hit the limit on the
200 * buffer, we simply drop further data.
201 */
202 void
203 db_capture_write(char *buffer, u_int buflen)
204 {
205 u_int len;
206
207 if (db_capture_inprogress == 0 || db_capture_inpager)
208 return;
209 len = min(buflen, db_capture_bufsize - db_capture_bufoff);
210 bcopy(buffer, db_capture_buf + db_capture_bufoff, len);
211 db_capture_bufoff += len;
212
213 KASSERT(db_capture_bufoff <= db_capture_bufsize,
214 ("db_capture_write: bufoff > bufsize"));
215 }
216
217 void
218 db_capture_writech(char ch)
219 {
220
221 return (db_capture_write(&ch, sizeof(ch)));
222 }
223
224 void
225 db_capture_enterpager(void)
226 {
227
228 db_capture_inpager = 1;
229 }
230
231 void
232 db_capture_exitpager(void)
233 {
234
235 db_capture_inpager = 0;
236 }
237
238 /*
239 * Zero out any bytes left in the last block of the DDB capture buffer. This
240 * is run shortly before writing the blocks to disk, rather than when output
241 * capture is stopped, in order to avoid injecting nul's into the middle of
242 * output.
243 */
244 static void
245 db_capture_zeropad(void)
246 {
247 u_int len;
248
249 len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize -
250 db_capture_bufoff) % TEXTDUMP_BLOCKSIZE);
251 bzero(db_capture_buf + db_capture_bufoff, len);
252 db_capture_bufpadding = len;
253 }
254
255 /*
256 * Reset capture state, which flushes buffers.
257 */
258 static void
259 db_capture_reset(void)
260 {
261
262 db_capture_inprogress = 0;
263 db_capture_bufoff = 0;
264 db_capture_bufpadding = 0;
265 }
266
267 /*
268 * Start capture. Only one session is allowed at any time, but we may
269 * continue a previous session, so the buffer isn't reset.
270 */
271 static void
272 db_capture_start(void)
273 {
274
275 if (db_capture_inprogress) {
276 db_printf("Capture already started\n");
277 return;
278 }
279 db_capture_inprogress = 1;
280 }
281
282 /*
283 * Terminate DDB output capture--real work is deferred to db_capture_dump,
284 * which executes outside of the DDB context. We don't zero pad here because
285 * capture may be started again before the dump takes place.
286 */
287 static void
288 db_capture_stop(void)
289 {
290
291 if (db_capture_inprogress == 0) {
292 db_printf("Capture not started\n");
293 return;
294 }
295 db_capture_inprogress = 0;
296 }
297
298 /*
299 * Dump DDB(4) captured output (and resets capture buffers).
300 */
301 void
302 db_capture_dump(struct dumperinfo *di)
303 {
304 u_int offset;
305
306 if (db_capture_bufoff == 0)
307 return;
308
309 db_capture_zeropad();
310 textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME,
311 db_capture_bufoff);
312 (void)textdump_writenextblock(di, textdump_block_buffer);
313 for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding;
314 offset += TEXTDUMP_BLOCKSIZE)
315 (void)textdump_writenextblock(di, db_capture_buf + offset);
316 db_capture_bufoff = 0;
317 db_capture_bufpadding = 0;
318 }
319
320 /*-
321 * DDB(4) command to manage capture:
322 *
323 * capture on - start DDB output capture
324 * capture off - stop DDB output capture
325 * capture reset - reset DDB capture buffer (also stops capture)
326 * capture status - print DDB output capture status
327 */
328 static void
329 db_capture_usage(void)
330 {
331
332 db_error("capture [on|off|reset|status]\n");
333 }
334
335 void
336 db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
337 {
338 int t;
339
340 t = db_read_token();
341 if (t != tIDENT) {
342 db_capture_usage();
343 return;
344 }
345 if (db_read_token() != tEOL)
346 db_error("?\n");
347 if (strcmp(db_tok_string, "on") == 0)
348 db_capture_start();
349 else if (strcmp(db_tok_string, "off") == 0)
350 db_capture_stop();
351 else if (strcmp(db_tok_string, "reset") == 0)
352 db_capture_reset();
353 else if (strcmp(db_tok_string, "status") == 0) {
354 db_printf("%u/%u bytes used\n", db_capture_bufoff,
355 db_capture_bufsize);
356 if (db_capture_inprogress)
357 db_printf("capture is on\n");
358 else
359 db_printf("capture is off\n");
360 } else
361 db_capture_usage();
362 }
Cache object: 5b6114964f1fbd47abc1e2c7af1637d2
|