FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_capture.c
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: src/sys/ddb/db_capture.c,v 1.6 2008/04/25 13:23:36 rwatson Exp $");
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 */
62 static 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
72 static char *db_capture_buf;
73 static u_int db_capture_bufsize = DDB_CAPTURE_DEFAULTBUFSIZE;
74 static u_int db_capture_maxbufsize = DDB_CAPTURE_MAXBUFSIZE; /* Read-only. */
75 static u_int db_capture_bufoff; /* Next location to write in buffer. */
76 static u_int db_capture_bufpadding; /* Amount of zero padding. */
77 static int db_capture_inpager; /* Suspend capture in pager. */
78 static int db_capture_inprogress; /* DDB capture currently in progress. */
79
80 struct sx db_capture_sx; /* Lock against user thread races. */
81 SX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx");
82
83 static SYSCTL_NODE(_debug_ddb, OID_AUTO, capture, CTLFLAG_RW, 0,
84 "DDB capture options");
85
86 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bufoff, CTLFLAG_RD,
87 &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
88
89 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
90 &db_capture_maxbufsize, 0,
91 "Maximum value for debug.ddb.capture.bufsize");
92
93 SYSCTL_UINT(_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 */
100 static void
101 db_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 }
114 SYSINIT(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 */
120 static int
121 sysctl_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 }
166 SYSCTL_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 */
174 static int
175 sysctl_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 }
192 SYSCTL_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 */
200 void
201 db_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
215 void
216 db_capture_writech(char ch)
217 {
218
219 return (db_capture_write(&ch, sizeof(ch)));
220 }
221
222 void
223 db_capture_enterpager(void)
224 {
225
226 db_capture_inpager = 1;
227 }
228
229 void
230 db_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 */
242 static void
243 db_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 */
256 static void
257 db_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 */
269 static void
270 db_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 */
285 static void
286 db_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 */
299 void
300 db_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 */
326 static void
327 db_capture_usage(void)
328 {
329
330 db_error("capture [on|off|reset|status]\n");
331 }
332
333 void
334 db_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
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