FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_textdump.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 * Kernel text-dump support: write a series of text files to the dump
29 * partition for later recovery, including captured DDB output, kernel
30 * configuration, message buffer, and panic message. This allows for a more
31 * compact representation of critical debugging information than traditional
32 * binary dumps, as well as allowing dump information to be used without
33 * access to kernel symbols, source code, etc.
34 *
35 * Storage Layout
36 * --------------
37 *
38 * Crash dumps are aligned to the end of the dump or swap partition in order
39 * to minimize the chances of swap duing fsck eating into the dump. However,
40 * unlike a memory dump, we don't know the size of the textdump a priori, so
41 * can't just write it out sequentially in order from a known starting point
42 * calculated with respect to the end of the partition. In order to address
43 * this, we actually write out the textdump in reverse block order, allowing
44 * us to directly align it to the end of the partition and then write out the
45 * dump header and trailer before and after it once done. savecore(8) must
46 * know to reverse the order of the blocks in order to produce a readable
47 * file.
48 *
49 * Data is written out in the ustar file format so that we can write data
50 * incrementally as a stream without reference to previous files.
51 *
52 * TODO
53 * ----
54 *
55 * - Allow subsytems to register to submit files for inclusion in the text
56 * dump in a generic way.
57 */
58
59 #include <sys/cdefs.h>
60 __FBSDID("$FreeBSD: releng/9.2/sys/ddb/db_textdump.c 193066 2009-05-29 21:27:12Z jamie $");
61
62 #include "opt_config.h"
63
64 #include <sys/param.h>
65 #include <sys/conf.h>
66 #include <sys/kernel.h>
67 #include <sys/kerneldump.h>
68 #include <sys/msgbuf.h>
69 #include <sys/sysctl.h>
70 #include <sys/systm.h>
71
72 #include <ddb/ddb.h>
73 #include <ddb/db_lex.h>
74
75 static SYSCTL_NODE(_debug_ddb, OID_AUTO, textdump, CTLFLAG_RW, 0,
76 "DDB textdump options");
77
78 /*
79 * Don't touch the first SIZEOF_METADATA bytes on the dump device. This is
80 * to protect us from metadata and metadata from us.
81 */
82 #define SIZEOF_METADATA (64*1024)
83
84 /*
85 * Data is written out as a series of files in the ustar tar format. ustar
86 * is a simple streamed format consiting of a series of files prefixed with
87 * headers, and all padded to 512-byte block boundaries, which maps
88 * conveniently to our requirements.
89 */
90 struct ustar_header {
91 char uh_filename[100];
92 char uh_mode[8];
93 char uh_tar_owner[8];
94 char uh_tar_group[8];
95 char uh_size[12];
96 char uh_mtime[12];
97 char uh_sum[8];
98 char uh_type;
99 char uh_linkfile[100];
100 char uh_ustar[6];
101 char uh_version[2];
102 char uh_owner[32];
103 char uh_group[32];
104 char uh_major[8];
105 char uh_minor[8];
106 char uh_filenameprefix[155];
107 char uh_zeropad[12];
108 } __packed;
109
110 /*
111 * Various size assertions -- pretty much everything must be one block in
112 * size.
113 */
114 CTASSERT(sizeof(struct kerneldumpheader) == TEXTDUMP_BLOCKSIZE);
115 CTASSERT(sizeof(struct ustar_header) == TEXTDUMP_BLOCKSIZE);
116
117 /*
118 * Is a textdump scheduled? If so, the shutdown code will invoke our dumpsys
119 * routine instead of the machine-dependent kernel dump routine.
120 */
121 int textdump_pending;
122 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, pending, CTLFLAG_RW,
123 &textdump_pending, 0,
124 "Perform textdump instead of regular kernel dump.");
125
126 /*
127 * Various constants for tar headers and contents.
128 */
129 #define TAR_USER "root"
130 #define TAR_GROUP "wheel"
131 #define TAR_UID ""
132 #define TAR_GID ""
133 #define TAR_MODE "0600"
134 #define TAR_USTAR "ustar"
135
136 #define TAR_CONFIG_FILENAME "config.txt" /* Kernel configuration. */
137 #define TAR_MSGBUF_FILENAME "msgbuf.txt" /* Kernel messsage buffer. */
138 #define TAR_PANIC_FILENAME "panic.txt" /* Panic message. */
139 #define TAR_VERSION_FILENAME "version.txt" /* Kernel version. */
140
141 /*
142 * Configure which files will be dumped.
143 */
144 #ifdef INCLUDE_CONFIG_FILE
145 static int textdump_do_config = 1;
146 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_config, CTLFLAG_RW,
147 &textdump_do_config, 0, "Dump kernel configuration in textdump");
148 #endif
149
150 static int textdump_do_ddb = 1;
151 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_ddb, CTLFLAG_RW,
152 &textdump_do_ddb, 0, "Dump DDB captured output in textdump");
153
154 static int textdump_do_msgbuf = 1;
155 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_msgbuf, CTLFLAG_RW,
156 &textdump_do_msgbuf, 0, "Dump kernel message buffer in textdump");
157
158 static int textdump_do_panic = 1;
159 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_panic, CTLFLAG_RW,
160 &textdump_do_panic, 0, "Dump kernel panic message in textdump");
161
162 static int textdump_do_version = 1;
163 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_version, CTLFLAG_RW,
164 &textdump_do_version, 0, "Dump kernel version string in textdump");
165
166 /*
167 * State related to incremental writing of blocks to disk.
168 */
169 static off_t textdump_offset; /* Offset of next sequential write. */
170 static int textdump_error; /* Carried write error, if any. */
171
172 /*
173 * Statically allocate space to prepare block-sized headers and data.
174 */
175 char textdump_block_buffer[TEXTDUMP_BLOCKSIZE];
176 static struct kerneldumpheader kdh;
177
178 /*
179 * Calculate and fill in the checksum for a ustar header.
180 */
181 static void
182 ustar_checksum(struct ustar_header *uhp)
183 {
184 u_int sum;
185 int i;
186
187 for (i = 0; i < sizeof(uhp->uh_sum); i++)
188 uhp->uh_sum[i] = ' ';
189 sum = 0;
190 for (i = 0; i < sizeof(*uhp); i++)
191 sum += ((u_char *)uhp)[i];
192 snprintf(uhp->uh_sum, sizeof(uhp->uh_sum), "%6o", sum);
193 }
194
195 /*
196 * Each file in the tarball has a block-sized header with its name and other,
197 * largely hard-coded, properties.
198 */
199 void
200 textdump_mkustar(char *block_buffer, const char *filename, u_int size)
201 {
202 struct ustar_header *uhp;
203
204 uhp = (struct ustar_header *)block_buffer;
205 bzero(uhp, sizeof(*uhp));
206 strlcpy(uhp->uh_filename, filename, sizeof(uhp->uh_filename));
207 strlcpy(uhp->uh_mode, TAR_MODE, sizeof(uhp->uh_mode));
208 snprintf(uhp->uh_size, sizeof(uhp->uh_size), "%o", size);
209 strlcpy(uhp->uh_tar_owner, TAR_UID, sizeof(uhp->uh_tar_owner));
210 strlcpy(uhp->uh_tar_group, TAR_GID, sizeof(uhp->uh_tar_group));
211 strlcpy(uhp->uh_owner, TAR_USER, sizeof(uhp->uh_owner));
212 strlcpy(uhp->uh_group, TAR_GROUP, sizeof(uhp->uh_group));
213 snprintf(uhp->uh_mtime, sizeof(uhp->uh_mtime), "%lo",
214 (unsigned long)time_second);
215 uhp->uh_type = 0;
216 strlcpy(uhp->uh_ustar, TAR_USTAR, sizeof(uhp->uh_ustar));
217 ustar_checksum(uhp);
218 }
219
220 /*
221 * textdump_writeblock() writes TEXTDUMP_BLOCKSIZE-sized blocks of data to
222 * the space between di->mediaoffset and di->mediaoffset + di->mediasize. It
223 * accepts an offset relative to di->mediaoffset. If we're carrying any
224 * error from previous I/O, return that error and don't continue to try to
225 * write. Most writers ignore the error and forge ahead on the basis that
226 * there's not much you can do.
227 */
228 static int
229 textdump_writeblock(struct dumperinfo *di, off_t offset, char *buffer)
230 {
231
232 if (textdump_error)
233 return (textdump_error);
234 if (offset + TEXTDUMP_BLOCKSIZE > di->mediasize)
235 return (EIO);
236 if (offset < SIZEOF_METADATA)
237 return (ENOSPC);
238 textdump_error = dump_write(di, buffer, 0, offset + di->mediaoffset,
239 TEXTDUMP_BLOCKSIZE);
240 return (textdump_error);
241 }
242
243 /*
244 * Interfaces to save and restore the dump offset, so that printers can go
245 * back to rewrite a header if required, while avoiding their knowing about
246 * the global layout of the blocks.
247 *
248 * If we ever want to support writing textdumps to tape or other
249 * stream-oriented target, we'll need to remove this.
250 */
251 void
252 textdump_saveoff(off_t *offsetp)
253 {
254
255 *offsetp = textdump_offset;
256 }
257
258 void
259 textdump_restoreoff(off_t offset)
260 {
261
262 textdump_offset = offset;
263 }
264
265 /*
266 * Interface to write the "next block" relative to the current offset; since
267 * we write backwards from the end of the partition, we subtract, but there's
268 * no reason for the caller to know this.
269 */
270 int
271 textdump_writenextblock(struct dumperinfo *di, char *buffer)
272 {
273 int error;
274
275 error = textdump_writeblock(di, textdump_offset, buffer);
276 textdump_offset -= TEXTDUMP_BLOCKSIZE;
277 return (error);
278 }
279
280 #ifdef INCLUDE_CONFIG_FILE
281 extern char kernconfstring[];
282
283 /*
284 * Dump kernel configuration.
285 */
286 static void
287 textdump_dump_config(struct dumperinfo *di)
288 {
289 u_int count, fullblocks, len;
290
291 len = strlen(kernconfstring);
292 textdump_mkustar(textdump_block_buffer, TAR_CONFIG_FILENAME, len);
293 (void)textdump_writenextblock(di, textdump_block_buffer);
294
295 /*
296 * Write out all full blocks directly from the string, and handle any
297 * left-over bits by copying it to out to the local buffer and
298 * zero-padding it.
299 */
300 fullblocks = len / TEXTDUMP_BLOCKSIZE;
301 for (count = 0; count < fullblocks; count++)
302 (void)textdump_writenextblock(di, kernconfstring + count *
303 TEXTDUMP_BLOCKSIZE);
304 if (len % TEXTDUMP_BLOCKSIZE != 0) {
305 bzero(textdump_block_buffer, TEXTDUMP_BLOCKSIZE);
306 bcopy(kernconfstring + count * TEXTDUMP_BLOCKSIZE,
307 textdump_block_buffer, len % TEXTDUMP_BLOCKSIZE);
308 (void)textdump_writenextblock(di, textdump_block_buffer);
309 }
310 }
311 #endif /* INCLUDE_CONFIG_FILE */
312
313 /*
314 * Dump kernel message buffer.
315 */
316 static void
317 textdump_dump_msgbuf(struct dumperinfo *di)
318 {
319 off_t end_offset, tarhdr_offset;
320 u_int i, len, offset, seq, total_len;
321 char buf[16];
322
323 /*
324 * Write out a dummy tar header to advance the offset; we'll rewrite
325 * it later once we know the true size.
326 */
327 textdump_saveoff(&tarhdr_offset);
328 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME, 0);
329 (void)textdump_writenextblock(di, textdump_block_buffer);
330
331 /*
332 * Copy out the data in small chunks, but don't copy nuls that may be
333 * present if the message buffer has not yet completely filled at
334 * least once.
335 */
336 total_len = 0;
337 offset = 0;
338 msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
339 while ((len = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq)) > 0) {
340 for (i = 0; i < len; i++) {
341 if (buf[i] == '\0')
342 continue;
343 textdump_block_buffer[offset] = buf[i];
344 offset++;
345 if (offset != sizeof(textdump_block_buffer))
346 continue;
347 (void)textdump_writenextblock(di,
348 textdump_block_buffer);
349 total_len += offset;
350 offset = 0;
351 }
352 }
353 total_len += offset; /* Without the zero-padding. */
354 if (offset != 0) {
355 bzero(textdump_block_buffer + offset,
356 sizeof(textdump_block_buffer) - offset);
357 (void)textdump_writenextblock(di, textdump_block_buffer);
358 }
359
360 /*
361 * Rewrite tar header to reflect how much was actually written.
362 */
363 textdump_saveoff(&end_offset);
364 textdump_restoreoff(tarhdr_offset);
365 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME,
366 total_len);
367 (void)textdump_writenextblock(di, textdump_block_buffer);
368 textdump_restoreoff(end_offset);
369 }
370
371 static void
372 textdump_dump_panic(struct dumperinfo *di)
373 {
374 u_int len;
375
376 /*
377 * Write out tar header -- we store up to one block of panic message.
378 */
379 len = min(strlen(panicstr), TEXTDUMP_BLOCKSIZE);
380 textdump_mkustar(textdump_block_buffer, TAR_PANIC_FILENAME, len);
381 (void)textdump_writenextblock(di, textdump_block_buffer);
382
383 /*
384 * Zero-pad the panic string and write out block.
385 */
386 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
387 bcopy(panicstr, textdump_block_buffer, len);
388 (void)textdump_writenextblock(di, textdump_block_buffer);
389 }
390
391 static void
392 textdump_dump_version(struct dumperinfo *di)
393 {
394 u_int len;
395
396 /*
397 * Write out tar header -- at most one block of version information.
398 */
399 len = min(strlen(version), TEXTDUMP_BLOCKSIZE);
400 textdump_mkustar(textdump_block_buffer, TAR_VERSION_FILENAME, len);
401 (void)textdump_writenextblock(di, textdump_block_buffer);
402
403 /*
404 * Zero pad the version string and write out block.
405 */
406 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
407 bcopy(version, textdump_block_buffer, len);
408 (void)textdump_writenextblock(di, textdump_block_buffer);
409 }
410
411 /*
412 * Commit text dump to disk.
413 */
414 void
415 textdump_dumpsys(struct dumperinfo *di)
416 {
417 off_t dumplen, trailer_offset;
418
419 if (di->blocksize != TEXTDUMP_BLOCKSIZE) {
420 printf("Dump partition block size (%ju) not textdump "
421 "block size (%ju)", (uintmax_t)di->blocksize,
422 (uintmax_t)TEXTDUMP_BLOCKSIZE);
423 return;
424 }
425
426 /*
427 * We don't know a priori how large the dump will be, but we do know
428 * that we need to reserve space for metadata and that we need two
429 * dump headers. Also leave room for one ustar header and one block
430 * of data.
431 */
432 if (di->mediasize < SIZEOF_METADATA + 2 * sizeof(kdh)) {
433 printf("Insufficient space on dump partition.\n");
434 return;
435 }
436 textdump_error = 0;
437
438 /*
439 * Position the start of the dump so that we'll write the kernel dump
440 * trailer immediately before the end of the partition, and then work
441 * our way back. We will rewrite this header later to reflect the
442 * true size if things go well.
443 */
444 textdump_offset = di->mediasize - sizeof(kdh);
445 textdump_saveoff(&trailer_offset);
446 mkdumpheader(&kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, 0, TEXTDUMP_BLOCKSIZE);
447 (void)textdump_writenextblock(di, (char *)&kdh);
448
449 /*
450 * Write a series of files in ustar format.
451 */
452 if (textdump_do_ddb)
453 db_capture_dump(di);
454 #ifdef INCLUDE_CONFIG_FILE
455 if (textdump_do_config)
456 textdump_dump_config(di);
457 #endif
458 if (textdump_do_msgbuf)
459 textdump_dump_msgbuf(di);
460 if (textdump_do_panic && panicstr != NULL)
461 textdump_dump_panic(di);
462 if (textdump_do_version)
463 textdump_dump_version(di);
464
465 /*
466 * Now that we know the true size, we can write out the header, then
467 * seek back to the end and rewrite the trailer with the correct
468 * size.
469 */
470 dumplen = trailer_offset - (textdump_offset + TEXTDUMP_BLOCKSIZE);
471 mkdumpheader(&kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, dumplen,
472 TEXTDUMP_BLOCKSIZE);
473 (void)textdump_writenextblock(di, (char *)&kdh);
474 textdump_restoreoff(trailer_offset);
475 (void)textdump_writenextblock(di, (char *)&kdh);
476
477 /*
478 * Terminate the dump, report any errors, and clear the pending flag.
479 */
480 if (textdump_error == 0)
481 (void)dump_write(di, NULL, 0, 0, 0);
482 if (textdump_error == ENOSPC)
483 printf("Insufficient space on dump partition\n");
484 else if (textdump_error != 0)
485 printf("Error %d writing dump\n", textdump_error);
486 else
487 printf("Textdump complete.\n");
488 textdump_pending = 0;
489 }
490
491 /*-
492 * DDB(4) command to manage textdumps:
493 *
494 * textdump set - request a textdump
495 * textdump status - print DDB output textdump status
496 * textdump unset - clear textdump request
497 */
498 static void
499 db_textdump_usage(void)
500 {
501
502 db_printf("textdump [unset|set|status]\n");
503 }
504
505 void
506 db_textdump_cmd(db_expr_t addr, boolean_t have_addr, db_expr_t count,
507 char *modif)
508 {
509 int t;
510
511 t = db_read_token();
512 if (t != tIDENT) {
513 db_textdump_usage();
514 return;
515 }
516 if (db_read_token() != tEOL) {
517 db_textdump_usage();
518 return;
519 }
520 if (strcmp(db_tok_string, "set") == 0) {
521 textdump_pending = 1;
522 db_printf("textdump set\n");
523 } else if (strcmp(db_tok_string, "status") == 0) {
524 if (textdump_pending)
525 db_printf("textdump is set\n");
526 else
527 db_printf("textdump is not set\n");
528 } else if (strcmp(db_tok_string, "unset") == 0) {
529 textdump_pending = 0;
530 db_printf("textdump unset\n");
531 } else
532 db_textdump_usage();
533 }
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