2 * Copyright (c) 2007 Robert N. M. Watson
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
28 * DDB capture support: capture kernel debugger output into a fixed-size
29 * buffer for later dumping to disk or extraction from user space.
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
37 #include <sys/param.h>
39 #include <sys/kernel.h>
40 #include <sys/kerneldump.h>
41 #include <sys/malloc.h>
42 #include <sys/msgbuf.h>
45 #include <sys/sysctl.h>
46 #include <sys/systm.h>
49 #include <ddb/db_lex.h>
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.
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
62 static MALLOC_DEFINE(M_DDB_CAPTURE, "ddb_capture", "DDB capture buffer");
64 #ifndef DDB_CAPTURE_DEFAULTBUFSIZE
65 #define DDB_CAPTURE_DEFAULTBUFSIZE 48*1024
67 #ifndef DDB_CAPTURE_MAXBUFSIZE
68 #define DDB_CAPTURE_MAXBUFSIZE 5*1024*1024
70 #define DDB_CAPTURE_FILENAME "ddb.txt" /* Captured DDB output. */
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. */
80 struct sx db_capture_sx; /* Lock against user thread races. */
81 SX_SYSINIT(db_capture_sx, &db_capture_sx, "db_capture_sx");
83 static SYSCTL_NODE(_debug_ddb, OID_AUTO, capture, CTLFLAG_RW, 0,
84 "DDB capture options");
86 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, bytes, CTLFLAG_RD,
87 &db_capture_bufoff, 0, "Bytes of data in DDB capture buffer");
89 SYSCTL_UINT(_debug_ddb_capture, OID_AUTO, maxbufsize, CTLFLAG_RD,
90 &db_capture_maxbufsize, 0,
91 "Maximum value for debug.ddb.capture.bufsize");
94 * Boot-time allocation of the DDB capture buffer, if any. Force all buffer
95 * sizes, including the maximum size, to be rounded to block sizes.
98 db_capture_sysinit(__unused void *dummy)
101 TUNABLE_INT_FETCH("debug.ddb.capture.bufsize", &db_capture_bufsize);
102 db_capture_maxbufsize = roundup(db_capture_maxbufsize,
104 db_capture_bufsize = roundup(db_capture_bufsize, TEXTDUMP_BLOCKSIZE);
105 if (db_capture_bufsize > db_capture_maxbufsize)
106 db_capture_bufsize = db_capture_maxbufsize;
107 if (db_capture_bufsize != 0)
108 db_capture_buf = malloc(db_capture_bufsize, M_DDB_CAPTURE,
111 SYSINIT(db_capture, SI_SUB_DDB_SERVICES, SI_ORDER_ANY, db_capture_sysinit,
115 * Run-time adjustment of the capture buffer.
118 sysctl_debug_ddb_capture_bufsize(SYSCTL_HANDLER_ARGS)
124 size = db_capture_bufsize;
125 error = sysctl_handle_int(oidp, &size, 0, req);
126 if (error || req->newptr == NULL)
128 size = roundup(size, TEXTDUMP_BLOCKSIZE);
129 if (size > db_capture_maxbufsize)
131 sx_xlock(&db_capture_sx);
134 * Potentially the buffer is quite large, so if we can't
135 * allocate it, fail rather than waiting.
137 buf = malloc(size, M_DDB_CAPTURE, M_NOWAIT);
139 sx_xunlock(&db_capture_sx);
142 len = min(db_capture_bufoff, size);
147 if (db_capture_buf != NULL && buf != NULL)
148 bcopy(db_capture_buf, buf, len);
149 if (db_capture_buf != NULL)
150 free(db_capture_buf, M_DDB_CAPTURE);
151 db_capture_bufoff = len;
152 db_capture_buf = buf;
153 db_capture_bufsize = size;
154 sx_xunlock(&db_capture_sx);
156 KASSERT(db_capture_bufoff <= db_capture_bufsize,
157 ("sysctl_debug_ddb_capture_bufsize: bufoff > bufsize"));
158 KASSERT(db_capture_bufsize <= db_capture_maxbufsize,
159 ("sysctl_debug_ddb_capture_maxbufsize: bufsize > maxbufsize"));
163 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, bufsize, CTLTYPE_UINT|CTLFLAG_RW,
164 0, 0, sysctl_debug_ddb_capture_bufsize, "IU",
165 "Size of DDB capture buffer");
168 * Sysctl to read out the capture buffer from userspace. We require
169 * privilege as sensitive process/memory information may be accessed.
172 sysctl_debug_ddb_capture_data(SYSCTL_HANDLER_ARGS)
177 error = priv_check(req->td, PRIV_DDB_CAPTURE);
181 sx_slock(&db_capture_sx);
182 error = SYSCTL_OUT(req, db_capture_buf, db_capture_bufoff);
183 sx_sunlock(&db_capture_sx);
187 return (SYSCTL_OUT(req, &ch, sizeof(ch)));
189 SYSCTL_PROC(_debug_ddb_capture, OID_AUTO, data, CTLTYPE_STRING | CTLFLAG_RD,
190 NULL, 0, sysctl_debug_ddb_capture_data, "A", "DDB capture data");
193 * Routines for capturing DDB output into a fixed-size buffer. These are
194 * invoked from DDB's input and output routines. If we hit the limit on the
195 * buffer, we simply drop further data.
198 db_capture_write(char *buffer, u_int buflen)
202 if (db_capture_inprogress == 0 || db_capture_inpager)
204 len = min(buflen, db_capture_bufsize - db_capture_bufoff);
205 bcopy(buffer, db_capture_buf + db_capture_bufoff, len);
206 db_capture_bufoff += len;
208 KASSERT(db_capture_bufoff <= db_capture_bufsize,
209 ("db_capture_write: bufoff > bufsize"));
213 db_capture_writech(char ch)
216 return (db_capture_write(&ch, sizeof(ch)));
220 db_capture_enterpager(void)
223 db_capture_inpager = 1;
227 db_capture_exitpager(void)
230 db_capture_inpager = 0;
234 * Zero out any bytes left in the last block of the DDB capture buffer. This
235 * is run shortly before writing the blocks to disk, rather than when output
236 * capture is stopped, in order to avoid injecting nul's into the middle of
240 db_capture_zeropad(void)
244 len = min(TEXTDUMP_BLOCKSIZE, (db_capture_bufsize -
245 db_capture_bufoff) % TEXTDUMP_BLOCKSIZE);
246 bzero(db_capture_buf + db_capture_bufoff, len);
247 db_capture_bufpadding = len;
251 * Reset capture state, which flushes buffers.
254 db_capture_reset(void)
257 db_capture_inprogress = 0;
258 db_capture_bufoff = 0;
259 db_capture_bufpadding = 0;
263 * Start capture. Only one session is allowed at any time, but we may
264 * continue a previous session, so the buffer isn't reset.
267 db_capture_start(void)
270 if (db_capture_inprogress) {
271 db_printf("Capture already started\n");
274 db_capture_inprogress = 1;
278 * Terminate DDB output capture--real work is deferred to db_capture_dump,
279 * which executes outside of the DDB context. We don't zero pad here because
280 * capture may be started again before the dump takes place.
283 db_capture_stop(void)
286 if (db_capture_inprogress == 0) {
287 db_printf("Capture not started\n");
290 db_capture_inprogress = 0;
294 * Dump DDB(4) captured output (and resets capture buffers).
297 db_capture_dump(struct dumperinfo *di)
301 if (db_capture_bufoff == 0)
304 db_capture_zeropad();
305 textdump_mkustar(textdump_block_buffer, DDB_CAPTURE_FILENAME,
307 (void)textdump_writenextblock(di, textdump_block_buffer);
308 for (offset = 0; offset < db_capture_bufoff + db_capture_bufpadding;
309 offset += TEXTDUMP_BLOCKSIZE)
310 (void)textdump_writenextblock(di, db_capture_buf + offset);
311 db_capture_bufoff = 0;
312 db_capture_bufpadding = 0;
316 * DDB(4) command to manage capture:
318 * capture on - start DDB output capture
319 * capture off - stop DDB output capture
320 * capture reset - reset DDB capture buffer (also stops capture)
321 * capture status - print DDB output capture status
324 db_capture_usage(void)
327 db_error("capture [on|off|reset|status]\n");
331 db_capture_cmd(db_expr_t addr, boolean_t have_addr, db_expr_t count,
341 if (db_read_token() != tEOL)
343 if (strcmp(db_tok_string, "on") == 0)
345 else if (strcmp(db_tok_string, "off") == 0)
347 else if (strcmp(db_tok_string, "reset") == 0)
349 else if (strcmp(db_tok_string, "status") == 0) {
350 db_printf("%u/%u bytes used\n", db_capture_bufoff,
352 if (db_capture_inprogress)
353 db_printf("capture is on\n");
355 db_printf("capture is off\n");