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: stable/12/sys/ddb/db_capture.c 373241 2023-10-12 05:11:39Z zlei $");
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
db_capture_sysinit(__unused void * dummy)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
sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS)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,
169 CTLTYPE_UINT | CTLFLAG_RWTUN | CTLFLAG_NOFETCH,
170 0, 0, sysctl_debug_ddb_capture_bufsize, "IU",
171 "Size of DDB capture buffer");
172
173 /*
174 * Sysctl to read out the capture buffer from userspace. We require
175 * privilege as sensitive process/memory information may be accessed.
176 */
177 static int
sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS)178 sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS)
179 {
180 int error;
181 char ch;
182
183 error = priv_check(req->td, PRIV_DDB_CAPTURE);
184 if (error)
185 return (error);
186
187 sx_slock(&db_capture_sx);
188 error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff);
189 sx_sunlock(&db_capture_sx);
190 if (error)
191 return (error);
192 ch = '\0';
193 return (SYSCTL_OUT(req, &ch, sizeof(ch)));
194 }
195 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, CTLTYPE_STRING | CTLFLAG_RD,
196 NULL, 0, sysctl_debug_ddb_capture_data, "A", "DDB capture data");
197
198 /*
199 * Routines for capturing DDB output into a fixed-size buffer. These are
200 * invoked from DDB's input and output routines. If we hit the limit on the
201 * buffer, we simply drop further data.
202 */
203 void
db_capture_write(char * buffer,u_int buflen)204 db_capture_write(char *buffer, u_int buflen)
205 {
206 u_int len;
207
208 if (db_capture_inprogress == 0 || db_capture_inpager)
209 return;
210 len = min(buflen, db_capture_bufsize - db_capture_bufoff);
211 bcopy(buffer, db_capture_buf + db_capture_bufoff, len);
212 db_capture_bufoff += len;
213
214 KASSERT(db_capture_bufoff <= db_capture_bufsize,
215 ("db_capture_write: bufoff > bufsize"));
216 }
217
218 void
db_capture_writech(char ch)219 db_capture_writech(char ch)
220 {
221
222 return (db_capture_write(&ch, sizeof(ch)));
223 }
224
225 void
db_capture_enterpager(void)226 db_capture_enterpager(void)
227 {
228
229 db_capture_inpager = 1;
230 }
231
232 void
db_capture_exitpager(void)233 db_capture_exitpager(void)
234 {
235
236 db_capture_inpager = 0;
237 }
238
239 /*
240 * Zero out any bytes left in the last block of the DDB capture buffer. This
241 * is run shortly before writing the blocks to disk, rather than when output
242 * capture is stopped, in order to avoid injecting nul's into the middle of
243 * output.
244 */
245 static void
db_capture_zeropad(void)246 db_capture_zeropad(void)
247 {
248 u_int len;
249
250 len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize -
251 db_capture_bufoff) % TEXTDUMP_BLOCKSIZE);
252 bzero(db_capture_buf + db_capture_bufoff, len);
253 db_capture_bufpadding = len;
254 }
255
256 /*
257 * Reset capture state, which flushes buffers.
258 */
259 static void
db_capture_reset(void)260 db_capture_reset(void)
261 {
262
263 db_capture_inprogress = 0;
264 db_capture_bufoff = 0;
265 db_capture_bufpadding = 0;
266 }
267
268 /*
269 * Start capture. Only one session is allowed at any time, but we may
270 * continue a previous session, so the buffer isn't reset.
271 */
272 static void
db_capture_start(void)273 db_capture_start(void)
274 {
275
276 if (db_capture_inprogress) {
277 db_printf("Capture already started\n");
278 return;
279 }
280 db_capture_inprogress = 1;
281 }
282
283 /*
284 * Terminate DDB output capture--real work is deferred to db_capture_dump,
285 * which executes outside of the DDB context. We don't zero pad here because
286 * capture may be started again before the dump takes place.
287 */
288 static void
db_capture_stop(void)289 db_capture_stop(void)
290 {
291
292 if (db_capture_inprogress == 0) {
293 db_printf("Capture not started\n");
294 return;
295 }
296 db_capture_inprogress = 0;
297 }
298
299 /*
300 * Dump DDB(4) captured output (and resets capture buffers).
301 */
302 void
db_capture_dump(struct dumperinfo * di)303 db_capture_dump(struct dumperinfo *di)
304 {
305 u_int offset;
306
307 if (db_capture_bufoff == 0)
308 return;
309
310 db_capture_zeropad();
311 textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME,
312 db_capture_bufoff);
313 (void)textdump_writenextblock(di, textdump_block_buffer);
314 for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding;
315 offset += TEXTDUMP_BLOCKSIZE)
316 (void)textdump_writenextblock(di, db_capture_buf + offset);
317 db_capture_bufoff = 0;
318 db_capture_bufpadding = 0;
319 }
320
321 /*-
322 * DDB(4) command to manage capture:
323 *
324 * capture on - start DDB output capture
325 * capture off - stop DDB output capture
326 * capture reset - reset DDB capture buffer (also stops capture)
327 * capture status - print DDB output capture status
328 */
329 static void
db_capture_usage(void)330 db_capture_usage(void)
331 {
332
333 db_error("capture [on|off|reset|status]\n");
334 }
335
336 void
db_capture_cmd(db_expr_t addr,bool have_addr,db_expr_t count,char * modif)337 db_capture_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
338 {
339 int t;
340
341 t = db_read_token();
342 if (t != tIDENT) {
343 db_capture_usage();
344 return;
345 }
346 if (db_read_token() != tEOL)
347 db_error("?\n");
348 if (strcmp(db_tok_string, "on") == 0)
349 db_capture_start();
350 else if (strcmp(db_tok_string, "off") == 0)
351 db_capture_stop();
352 else if (strcmp(db_tok_string, "reset") == 0)
353 db_capture_reset();
354 else if (strcmp(db_tok_string, "status") == 0) {
355 db_printf("%u/%u bytes used\n", db_capture_bufoff,
356 db_capture_bufsize);
357 if (db_capture_inprogress)
358 db_printf("capture is on\n");
359 else
360 db_printf("capture is off\n");
361 } else
362 db_capture_usage();
363 }
364