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("$FreeBSD$");
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 * Text dumps are prefixed with a normal kernel dump header but with a
180 * different magic number to allow them to be uniquely identified.
181 */
182 static void
183 mkdumpheader(struct kerneldumpheader *kdh, uint32_t archver,
184 uint64_t dumplen, uint32_t blksz)
185 {
186
187 bzero(kdh, sizeof(*kdh));
188 strncpy(kdh->magic, TEXTDUMPMAGIC, sizeof(kdh->magic));
189 strncpy(kdh->architecture, MACHINE_ARCH, sizeof(kdh->architecture));
190 kdh->version = htod32(KERNELDUMPVERSION);
191 kdh->architectureversion = htod32(archver);
192 kdh->dumplength = htod64(dumplen);
193 kdh->dumptime = htod64(time_second);
194 kdh->blocksize = htod32(blksz);
195 strncpy(kdh->hostname, hostname, sizeof(kdh->hostname));
196 strncpy(kdh->versionstring, version, sizeof(kdh->versionstring));
197 if (panicstr != NULL)
198 strncpy(kdh->panicstring, panicstr, sizeof(kdh->panicstring));
199 kdh->parity = kerneldump_parity(kdh);
200 }
201
202 /*
203 * Calculate and fill in the checksum for a ustar header.
204 */
205 static void
206 ustar_checksum(struct ustar_header *uhp)
207 {
208 u_int sum;
209 int i;
210
211 for (i = 0; i < sizeof(uhp->uh_sum); i++)
212 uhp->uh_sum[i] = ' ';
213 sum = 0;
214 for (i = 0; i < sizeof(*uhp); i++)
215 sum += ((u_char *)uhp)[i];
216 snprintf(uhp->uh_sum, sizeof(uhp->uh_sum), "%6o", sum);
217 }
218
219 /*
220 * Each file in the tarball has a block-sized header with its name and other,
221 * largely hard-coded, properties.
222 */
223 void
224 textdump_mkustar(char *block_buffer, const char *filename, u_int size)
225 {
226 struct ustar_header *uhp;
227
228 uhp = (struct ustar_header *)block_buffer;
229 bzero(uhp, sizeof(*uhp));
230 strlcpy(uhp->uh_filename, filename, sizeof(uhp->uh_filename));
231 strlcpy(uhp->uh_mode, TAR_MODE, sizeof(uhp->uh_mode));
232 snprintf(uhp->uh_size, sizeof(uhp->uh_size), "%o", size);
233 strlcpy(uhp->uh_tar_owner, TAR_UID, sizeof(uhp->uh_tar_owner));
234 strlcpy(uhp->uh_tar_group, TAR_GID, sizeof(uhp->uh_tar_group));
235 strlcpy(uhp->uh_owner, TAR_USER, sizeof(uhp->uh_owner));
236 strlcpy(uhp->uh_group, TAR_GROUP, sizeof(uhp->uh_group));
237 snprintf(uhp->uh_mtime, sizeof(uhp->uh_mtime), "%lo",
238 (unsigned long)time_second);
239 uhp->uh_type = 0;
240 strlcpy(uhp->uh_ustar, TAR_USTAR, sizeof(uhp->uh_ustar));
241 ustar_checksum(uhp);
242 }
243
244 /*
245 * textdump_writeblock() writes TEXTDUMP_BLOCKSIZE-sized blocks of data to
246 * the space between di->mediaoffset and di->mediaoffset + di->mediasize. It
247 * accepts an offset relative to di->mediaoffset. If we're carrying any
248 * error from previous I/O, return that error and don't continue to try to
249 * write. Most writers ignore the error and forge ahead on the basis that
250 * there's not much you can do.
251 */
252 static int
253 textdump_writeblock(struct dumperinfo *di, off_t offset, char *buffer)
254 {
255
256 if (textdump_error)
257 return (textdump_error);
258 if (offset + TEXTDUMP_BLOCKSIZE > di->mediasize)
259 return (EIO);
260 if (offset < SIZEOF_METADATA)
261 return (ENOSPC);
262 textdump_error = dump_write(di, buffer, 0, offset + di->mediaoffset,
263 TEXTDUMP_BLOCKSIZE);
264 return (textdump_error);
265 }
266
267 /*
268 * Interfaces to save and restore the dump offset, so that printers can go
269 * back to rewrite a header if required, while avoiding their knowing about
270 * the global layout of the blocks.
271 *
272 * If we ever want to support writing textdumps to tape or other
273 * stream-oriented target, we'll need to remove this.
274 */
275 void
276 textdump_saveoff(off_t *offsetp)
277 {
278
279 *offsetp = textdump_offset;
280 }
281
282 void
283 textdump_restoreoff(off_t offset)
284 {
285
286 textdump_offset = offset;
287 }
288
289 /*
290 * Interface to write the "next block" relative to the current offset; since
291 * we write backwards from the end of the partition, we subtract, but there's
292 * no reason for the caller to know this.
293 */
294 int
295 textdump_writenextblock(struct dumperinfo *di, char *buffer)
296 {
297 int error;
298
299 error = textdump_writeblock(di, textdump_offset, buffer);
300 textdump_offset -= TEXTDUMP_BLOCKSIZE;
301 return (error);
302 }
303
304 #ifdef INCLUDE_CONFIG_FILE
305 extern char kernconfstring[];
306
307 /*
308 * Dump kernel configuration.
309 */
310 static void
311 textdump_dump_config(struct dumperinfo *di)
312 {
313 u_int count, fullblocks, len;
314
315 len = strlen(kernconfstring);
316 textdump_mkustar(textdump_block_buffer, TAR_CONFIG_FILENAME, len);
317 (void)textdump_writenextblock(di, textdump_block_buffer);
318
319 /*
320 * Write out all full blocks directly from the string, and handle any
321 * left-over bits by copying it to out to the local buffer and
322 * zero-padding it.
323 */
324 fullblocks = len / TEXTDUMP_BLOCKSIZE;
325 for (count = 0; count < fullblocks; count++)
326 (void)textdump_writenextblock(di, kernconfstring + count *
327 TEXTDUMP_BLOCKSIZE);
328 if (len % TEXTDUMP_BLOCKSIZE != 0) {
329 bzero(textdump_block_buffer, TEXTDUMP_BLOCKSIZE);
330 bcopy(kernconfstring + count * TEXTDUMP_BLOCKSIZE,
331 textdump_block_buffer, len % TEXTDUMP_BLOCKSIZE);
332 (void)textdump_writenextblock(di, textdump_block_buffer);
333 }
334 }
335 #endif /* INCLUDE_CONFIG_FILE */
336
337 /*
338 * Dump kernel message buffer.
339 */
340 static void
341 textdump_dump_msgbuf(struct dumperinfo *di)
342 {
343 off_t end_offset, tarhdr_offset;
344 u_int i, len, offset, seq, total_len;
345 char buf[16];
346
347 /*
348 * Write out a dummy tar header to advance the offset; we'll rewrite
349 * it later once we know the true size.
350 */
351 textdump_saveoff(&tarhdr_offset);
352 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME, 0);
353 (void)textdump_writenextblock(di, textdump_block_buffer);
354
355 /*
356 * Copy out the data in small chunks, but don't copy nuls that may be
357 * present if the message buffer has not yet completely filled at
358 * least once.
359 */
360 total_len = 0;
361 offset = 0;
362 msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
363 while ((len = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq)) > 0) {
364 for (i = 0; i < len; i++) {
365 if (buf[i] == '\0')
366 continue;
367 textdump_block_buffer[offset] = buf[i];
368 offset++;
369 if (offset != sizeof(textdump_block_buffer))
370 continue;
371 (void)textdump_writenextblock(di,
372 textdump_block_buffer);
373 total_len += offset;
374 offset = 0;
375 }
376 }
377 total_len += offset; /* Without the zero-padding. */
378 if (offset != 0) {
379 bzero(textdump_block_buffer + offset,
380 sizeof(textdump_block_buffer) - offset);
381 (void)textdump_writenextblock(di, textdump_block_buffer);
382 }
383
384 /*
385 * Rewrite tar header to reflect how much was actually written.
386 */
387 textdump_saveoff(&end_offset);
388 textdump_restoreoff(tarhdr_offset);
389 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME,
390 total_len);
391 (void)textdump_writenextblock(di, textdump_block_buffer);
392 textdump_restoreoff(end_offset);
393 }
394
395 static void
396 textdump_dump_panic(struct dumperinfo *di)
397 {
398 u_int len;
399
400 /*
401 * Write out tar header -- we store up to one block of panic message.
402 */
403 len = min(strlen(panicstr), TEXTDUMP_BLOCKSIZE);
404 textdump_mkustar(textdump_block_buffer, TAR_PANIC_FILENAME, len);
405 (void)textdump_writenextblock(di, textdump_block_buffer);
406
407 /*
408 * Zero-pad the panic string and write out block.
409 */
410 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
411 bcopy(panicstr, textdump_block_buffer, len);
412 (void)textdump_writenextblock(di, textdump_block_buffer);
413 }
414
415 static void
416 textdump_dump_version(struct dumperinfo *di)
417 {
418 u_int len;
419
420 /*
421 * Write out tar header -- at most one block of version information.
422 */
423 len = min(strlen(version), TEXTDUMP_BLOCKSIZE);
424 textdump_mkustar(textdump_block_buffer, TAR_VERSION_FILENAME, len);
425 (void)textdump_writenextblock(di, textdump_block_buffer);
426
427 /*
428 * Zero pad the version string and write out block.
429 */
430 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
431 bcopy(version, textdump_block_buffer, len);
432 (void)textdump_writenextblock(di, textdump_block_buffer);
433 }
434
435 /*
436 * Commit text dump to disk.
437 */
438 void
439 textdump_dumpsys(struct dumperinfo *di)
440 {
441 off_t dumplen, trailer_offset;
442
443 if (di->blocksize != TEXTDUMP_BLOCKSIZE) {
444 printf("Dump partition block size (%ju) not textdump "
445 "block size (%ju)", (uintmax_t)di->blocksize,
446 (uintmax_t)TEXTDUMP_BLOCKSIZE);
447 return;
448 }
449
450 /*
451 * We don't know a priori how large the dump will be, but we do know
452 * that we need to reserve space for metadata and that we need two
453 * dump headers. Also leave room for one ustar header and one block
454 * of data.
455 */
456 if (di->mediasize < SIZEOF_METADATA + 2 * sizeof(kdh)) {
457 printf("Insufficient space on dump partition.\n");
458 return;
459 }
460 textdump_error = 0;
461
462 /*
463 * Position the start of the dump so that we'll write the kernel dump
464 * trailer immediately before the end of the partition, and then work
465 * our way back. We will rewrite this header later to reflect the
466 * true size if things go well.
467 */
468 textdump_offset = di->mediasize - sizeof(kdh);
469 textdump_saveoff(&trailer_offset);
470 mkdumpheader(&kdh, KERNELDUMP_TEXT_VERSION, 0, TEXTDUMP_BLOCKSIZE);
471 (void)textdump_writenextblock(di, (char *)&kdh);
472
473 /*
474 * Write a series of files in ustar format.
475 */
476 if (textdump_do_ddb)
477 db_capture_dump(di);
478 #ifdef INCLUDE_CONFIG_FILE
479 if (textdump_do_config)
480 textdump_dump_config(di);
481 #endif
482 if (textdump_do_msgbuf)
483 textdump_dump_msgbuf(di);
484 if (textdump_do_panic && panicstr != NULL)
485 textdump_dump_panic(di);
486 if (textdump_do_version)
487 textdump_dump_version(di);
488
489 /*
490 * Now that we know the true size, we can write out the header, then
491 * seek back to the end and rewrite the trailer with the correct
492 * size.
493 */
494 dumplen = trailer_offset - (textdump_offset + TEXTDUMP_BLOCKSIZE);
495 mkdumpheader(&kdh, KERNELDUMP_TEXT_VERSION, dumplen,
496 TEXTDUMP_BLOCKSIZE);
497 (void)textdump_writenextblock(di, (char *)&kdh);
498 textdump_restoreoff(trailer_offset);
499 (void)textdump_writenextblock(di, (char *)&kdh);
500
501 /*
502 * Terminate the dump, report any errors, and clear the pending flag.
503 */
504 if (textdump_error == 0)
505 (void)dump_write(di, NULL, 0, 0, 0);
506 if (textdump_error == ENOSPC)
507 printf("Insufficient space on dump partition\n");
508 else if (textdump_error != 0)
509 printf("Error %d writing dump\n", textdump_error);
510 else
511 printf("Textdump complete.\n");
512 textdump_pending = 0;
513 }
514
515 /*-
516 * DDB(4) command to manage textdumps:
517 *
518 * textdump set - request a textdump
519 * textdump status - print DDB output textdump status
520 * textdump unset - clear textdump request
521 */
522 static void
523 db_textdump_usage(void)
524 {
525
526 db_printf("textdump [unset|set|status]\n");
527 }
528
529 void
530 db_textdump_cmd(db_expr_t addr, boolean_t have_addr, db_expr_t count,
531 char *modif)
532 {
533 int t;
534
535 t = db_read_token();
536 if (t != tIDENT) {
537 db_textdump_usage();
538 return;
539 }
540 if (db_read_token() != tEOL) {
541 db_textdump_usage();
542 return;
543 }
544 if (strcmp(db_tok_string, "set") == 0) {
545 textdump_pending = 1;
546 db_printf("textdump set\n");
547 } else if (strcmp(db_tok_string, "status") == 0) {
548 if (textdump_pending)
549 db_printf("textdump is set\n");
550 else
551 db_printf("textdump is not set\n");
552 } else if (strcmp(db_tok_string, "unset") == 0) {
553 textdump_pending = 0;
554 db_printf("textdump unset\n");
555 } else
556 db_textdump_usage();
557 }
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