FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_textdump.c
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 * Kernel text-dump support: write a series of text files to the dump
31 * partition for later recovery, including captured DDB output, kernel
32 * configuration, message buffer, and panic message. This allows for a more
33 * compact representation of critical debugging information than traditional
34 * binary dumps, as well as allowing dump information to be used without
35 * access to kernel symbols, source code, etc.
36 *
37 * Storage Layout
38 * --------------
39 *
40 * Crash dumps are aligned to the end of the dump or swap partition in order
41 * to minimize the chances of swap duing fsck eating into the dump. However,
42 * unlike a memory dump, we don't know the size of the textdump a priori, so
43 * can't just write it out sequentially in order from a known starting point
44 * calculated with respect to the end of the partition. In order to address
45 * this, we actually write out the textdump in reverse block order, allowing
46 * us to directly align it to the end of the partition and then write out the
47 * dump header and trailer before and after it once done. savecore(8) must
48 * know to reverse the order of the blocks in order to produce a readable
49 * file.
50 *
51 * Data is written out in the ustar file format so that we can write data
52 * incrementally as a stream without reference to previous files.
53 *
54 * TODO
55 * ----
56 *
57 * - Allow subsystems to register to submit files for inclusion in the text
58 * dump in a generic way.
59 */
60
61 #include <sys/cdefs.h>
62 __FBSDID("$FreeBSD$");
63
64 #include "opt_config.h"
65
66 #include "opt_ddb.h"
67
68 #include <sys/param.h>
69 #include <sys/conf.h>
70 #include <sys/kernel.h>
71 #include <sys/kerneldump.h>
72 #include <sys/msgbuf.h>
73 #include <sys/sysctl.h>
74 #include <sys/systm.h>
75
76 #include <ddb/ddb.h>
77 #include <ddb/db_lex.h>
78
79 static SYSCTL_NODE(_debug_ddb, OID_AUTO, textdump,
80 CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
81 "DDB textdump options");
82
83 /*
84 * Don't touch the first SIZEOF_METADATA bytes on the dump device. This is
85 * to protect us from metadata and metadata from us.
86 */
87 #define SIZEOF_METADATA (64*1024)
88
89 /*
90 * Data is written out as a series of files in the ustar tar format. ustar
91 * is a simple streamed format consiting of a series of files prefixed with
92 * headers, and all padded to 512-byte block boundaries, which maps
93 * conveniently to our requirements.
94 */
95 struct ustar_header {
96 char uh_filename[100];
97 char uh_mode[8];
98 char uh_tar_owner[8];
99 char uh_tar_group[8];
100 char uh_size[12];
101 char uh_mtime[12];
102 char uh_sum[8];
103 char uh_type;
104 char uh_linkfile[100];
105 char uh_ustar[6];
106 char uh_version[2];
107 char uh_owner[32];
108 char uh_group[32];
109 char uh_major[8];
110 char uh_minor[8];
111 char uh_filenameprefix[155];
112 char uh_zeropad[12];
113 } __packed;
114
115 /*
116 * Various size assertions -- pretty much everything must be one block in
117 * size.
118 */
119 CTASSERT(sizeof(struct kerneldumpheader) == TEXTDUMP_BLOCKSIZE);
120 CTASSERT(sizeof(struct ustar_header) == TEXTDUMP_BLOCKSIZE);
121
122 /*
123 * Is a textdump scheduled? If so, the shutdown code will invoke our dumpsys
124 * routine instead of the machine-dependent kernel dump routine.
125 */
126 #ifdef TEXTDUMP_PREFERRED
127 int textdump_pending = 1;
128 #else
129 int textdump_pending = 0;
130 #endif
131 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, pending, CTLFLAG_RW,
132 &textdump_pending, 0,
133 "Perform textdump instead of regular kernel dump.");
134
135 /*
136 * Various constants for tar headers and contents.
137 */
138 #define TAR_USER "root"
139 #define TAR_GROUP "wheel"
140 #define TAR_UID ""
141 #define TAR_GID ""
142 #define TAR_MODE "0600"
143 #define TAR_USTAR "ustar"
144
145 #define TAR_CONFIG_FILENAME "config.txt" /* Kernel configuration. */
146 #define TAR_MSGBUF_FILENAME "msgbuf.txt" /* Kernel messsage buffer. */
147 #define TAR_PANIC_FILENAME "panic.txt" /* Panic message. */
148 #define TAR_VERSION_FILENAME "version.txt" /* Kernel version. */
149
150 /*
151 * Configure which files will be dumped.
152 */
153 #ifdef INCLUDE_CONFIG_FILE
154 static int textdump_do_config = 1;
155 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_config, CTLFLAG_RW,
156 &textdump_do_config, 0, "Dump kernel configuration in textdump");
157 #endif
158
159 static int textdump_do_ddb = 1;
160 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_ddb, CTLFLAG_RW,
161 &textdump_do_ddb, 0, "Dump DDB captured output in textdump");
162
163 static int textdump_do_msgbuf = 1;
164 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_msgbuf, CTLFLAG_RW,
165 &textdump_do_msgbuf, 0, "Dump kernel message buffer in textdump");
166
167 static int textdump_do_panic = 1;
168 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_panic, CTLFLAG_RW,
169 &textdump_do_panic, 0, "Dump kernel panic message in textdump");
170
171 static int textdump_do_version = 1;
172 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_version, CTLFLAG_RW,
173 &textdump_do_version, 0, "Dump kernel version string in textdump");
174
175 /*
176 * State related to incremental writing of blocks to disk.
177 */
178 static off_t textdump_offset; /* Offset of next sequential write. */
179 static int textdump_error; /* Carried write error, if any. */
180
181 /*
182 * Statically allocate space to prepare block-sized headers and data.
183 */
184 char textdump_block_buffer[TEXTDUMP_BLOCKSIZE];
185 static struct kerneldumpheader kdh;
186
187 /*
188 * Calculate and fill in the checksum for a ustar header.
189 */
190 static void
191 ustar_checksum(struct ustar_header *uhp)
192 {
193 u_int sum;
194 int i;
195
196 for (i = 0; i < sizeof(uhp->uh_sum); i++)
197 uhp->uh_sum[i] = ' ';
198 sum = 0;
199 for (i = 0; i < sizeof(*uhp); i++)
200 sum += ((u_char *)uhp)[i];
201 snprintf(uhp->uh_sum, sizeof(uhp->uh_sum), "%6o", sum);
202 }
203
204 /*
205 * Each file in the tarball has a block-sized header with its name and other,
206 * largely hard-coded, properties.
207 */
208 void
209 textdump_mkustar(char *block_buffer, const char *filename, u_int size)
210 {
211 struct ustar_header *uhp;
212
213 #ifdef TEXTDUMP_VERBOSE
214 if (textdump_error == 0)
215 printf("textdump: creating '%s'.\n", filename);
216 #endif
217 uhp = (struct ustar_header *)block_buffer;
218 bzero(uhp, sizeof(*uhp));
219 strlcpy(uhp->uh_filename, filename, sizeof(uhp->uh_filename));
220 strlcpy(uhp->uh_mode, TAR_MODE, sizeof(uhp->uh_mode));
221 snprintf(uhp->uh_size, sizeof(uhp->uh_size), "%o", size);
222 strlcpy(uhp->uh_tar_owner, TAR_UID, sizeof(uhp->uh_tar_owner));
223 strlcpy(uhp->uh_tar_group, TAR_GID, sizeof(uhp->uh_tar_group));
224 strlcpy(uhp->uh_owner, TAR_USER, sizeof(uhp->uh_owner));
225 strlcpy(uhp->uh_group, TAR_GROUP, sizeof(uhp->uh_group));
226 snprintf(uhp->uh_mtime, sizeof(uhp->uh_mtime), "%lo",
227 (unsigned long)time_second);
228 uhp->uh_type = 0;
229 strlcpy(uhp->uh_ustar, TAR_USTAR, sizeof(uhp->uh_ustar));
230 ustar_checksum(uhp);
231 }
232
233 /*
234 * textdump_writeblock() writes TEXTDUMP_BLOCKSIZE-sized blocks of data to
235 * the space between di->mediaoffset and di->mediaoffset + di->mediasize. It
236 * accepts an offset relative to di->mediaoffset. If we're carrying any
237 * error from previous I/O, return that error and don't continue to try to
238 * write. Most writers ignore the error and forge ahead on the basis that
239 * there's not much you can do.
240 */
241 static int
242 textdump_writeblock(struct dumperinfo *di, off_t offset, char *buffer)
243 {
244
245 if (textdump_error)
246 return (textdump_error);
247 if (offset + TEXTDUMP_BLOCKSIZE > di->mediasize)
248 return (EIO);
249 if (offset < SIZEOF_METADATA)
250 return (ENOSPC);
251 textdump_error = dump_write(di, buffer, offset + di->mediaoffset,
252 TEXTDUMP_BLOCKSIZE);
253 if (textdump_error)
254 printf("textdump_writeblock: offset %jd, error %d\n", (intmax_t)offset,
255 textdump_error);
256 return (textdump_error);
257 }
258
259 /*
260 * Interfaces to save and restore the dump offset, so that printers can go
261 * back to rewrite a header if required, while avoiding their knowing about
262 * the global layout of the blocks.
263 *
264 * If we ever want to support writing textdumps to tape or other
265 * stream-oriented target, we'll need to remove this.
266 */
267 void
268 textdump_saveoff(off_t *offsetp)
269 {
270
271 *offsetp = textdump_offset;
272 }
273
274 void
275 textdump_restoreoff(off_t offset)
276 {
277
278 textdump_offset = offset;
279 }
280
281 /*
282 * Interface to write the "next block" relative to the current offset; since
283 * we write backwards from the end of the partition, we subtract, but there's
284 * no reason for the caller to know this.
285 */
286 int
287 textdump_writenextblock(struct dumperinfo *di, char *buffer)
288 {
289 int error;
290
291 error = textdump_writeblock(di, textdump_offset, buffer);
292 textdump_offset -= TEXTDUMP_BLOCKSIZE;
293 return (error);
294 }
295
296 #ifdef INCLUDE_CONFIG_FILE
297 extern char kernconfstring[];
298
299 /*
300 * Dump kernel configuration.
301 */
302 static void
303 textdump_dump_config(struct dumperinfo *di)
304 {
305 u_int count, fullblocks, len;
306
307 len = strlen(kernconfstring);
308 textdump_mkustar(textdump_block_buffer, TAR_CONFIG_FILENAME, len);
309 (void)textdump_writenextblock(di, textdump_block_buffer);
310
311 /*
312 * Write out all full blocks directly from the string, and handle any
313 * left-over bits by copying it to out to the local buffer and
314 * zero-padding it.
315 */
316 fullblocks = len / TEXTDUMP_BLOCKSIZE;
317 for (count = 0; count < fullblocks; count++)
318 (void)textdump_writenextblock(di, kernconfstring + count *
319 TEXTDUMP_BLOCKSIZE);
320 if (len % TEXTDUMP_BLOCKSIZE != 0) {
321 bzero(textdump_block_buffer, TEXTDUMP_BLOCKSIZE);
322 bcopy(kernconfstring + count * TEXTDUMP_BLOCKSIZE,
323 textdump_block_buffer, len % TEXTDUMP_BLOCKSIZE);
324 (void)textdump_writenextblock(di, textdump_block_buffer);
325 }
326 }
327 #endif /* INCLUDE_CONFIG_FILE */
328
329 /*
330 * Dump kernel message buffer.
331 */
332 static void
333 textdump_dump_msgbuf(struct dumperinfo *di)
334 {
335 off_t end_offset, tarhdr_offset;
336 u_int i, len, offset, seq, total_len;
337 char buf[16];
338
339 /*
340 * Write out a dummy tar header to advance the offset; we'll rewrite
341 * it later once we know the true size.
342 */
343 textdump_saveoff(&tarhdr_offset);
344 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME, 0);
345 (void)textdump_writenextblock(di, textdump_block_buffer);
346
347 /*
348 * Copy out the data in small chunks, but don't copy nuls that may be
349 * present if the message buffer has not yet completely filled at
350 * least once.
351 */
352 total_len = 0;
353 offset = 0;
354 msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
355 while ((len = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq)) > 0) {
356 for (i = 0; i < len; i++) {
357 if (buf[i] == '\0')
358 continue;
359 textdump_block_buffer[offset] = buf[i];
360 offset++;
361 if (offset != sizeof(textdump_block_buffer))
362 continue;
363 (void)textdump_writenextblock(di,
364 textdump_block_buffer);
365 total_len += offset;
366 offset = 0;
367 }
368 }
369 total_len += offset; /* Without the zero-padding. */
370 if (offset != 0) {
371 bzero(textdump_block_buffer + offset,
372 sizeof(textdump_block_buffer) - offset);
373 (void)textdump_writenextblock(di, textdump_block_buffer);
374 }
375
376 /*
377 * Rewrite tar header to reflect how much was actually written.
378 */
379 textdump_saveoff(&end_offset);
380 textdump_restoreoff(tarhdr_offset);
381 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME,
382 total_len);
383 (void)textdump_writenextblock(di, textdump_block_buffer);
384 textdump_restoreoff(end_offset);
385 }
386
387 static void
388 textdump_dump_panic(struct dumperinfo *di)
389 {
390 u_int len;
391
392 /*
393 * Write out tar header -- we store up to one block of panic message.
394 */
395 len = min(strlen(panicstr), TEXTDUMP_BLOCKSIZE);
396 textdump_mkustar(textdump_block_buffer, TAR_PANIC_FILENAME, len);
397 (void)textdump_writenextblock(di, textdump_block_buffer);
398
399 /*
400 * Zero-pad the panic string and write out block.
401 */
402 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
403 bcopy(panicstr, textdump_block_buffer, len);
404 (void)textdump_writenextblock(di, textdump_block_buffer);
405 }
406
407 static void
408 textdump_dump_version(struct dumperinfo *di)
409 {
410 u_int len;
411
412 /*
413 * Write out tar header -- at most one block of version information.
414 */
415 len = min(strlen(version), TEXTDUMP_BLOCKSIZE);
416 textdump_mkustar(textdump_block_buffer, TAR_VERSION_FILENAME, len);
417 (void)textdump_writenextblock(di, textdump_block_buffer);
418
419 /*
420 * Zero pad the version string and write out block.
421 */
422 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
423 bcopy(version, textdump_block_buffer, len);
424 (void)textdump_writenextblock(di, textdump_block_buffer);
425 }
426
427 /*
428 * Commit text dump to disk.
429 */
430 void
431 textdump_dumpsys(struct dumperinfo *di)
432 {
433 struct kerneldumpcrypto *kdc;
434 off_t dumplen, trailer_offset;
435
436 if (di->blocksize != TEXTDUMP_BLOCKSIZE) {
437 printf("Dump partition block size (%ju) not textdump "
438 "block size (%ju)", (uintmax_t)di->blocksize,
439 (uintmax_t)TEXTDUMP_BLOCKSIZE);
440 return;
441 }
442
443 /*
444 * We don't know a priori how large the dump will be, but we do know
445 * that we need to reserve space for metadata and that we need two
446 * dump headers. Also leave room for one ustar header and one block
447 * of data.
448 */
449 if (di->mediasize < SIZEOF_METADATA + 2 * sizeof(kdh)) {
450 printf("Insufficient space on dump partition for minimal textdump.\n");
451 return;
452 }
453 textdump_error = 0;
454
455 /*
456 * Disable EKCD because we don't provide encrypted textdumps.
457 */
458 kdc = di->kdcrypto;
459 di->kdcrypto = NULL;
460
461 /*
462 * Position the start of the dump so that we'll write the kernel dump
463 * trailer immediately before the end of the partition, and then work
464 * our way back. We will rewrite this header later to reflect the
465 * true size if things go well.
466 */
467 textdump_offset = di->mediasize - sizeof(kdh);
468 textdump_saveoff(&trailer_offset);
469 dump_init_header(di, &kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, 0);
470 (void)textdump_writenextblock(di, (char *)&kdh);
471
472 /*
473 * Write a series of files in ustar format.
474 */
475 if (textdump_do_ddb)
476 db_capture_dump(di);
477 #ifdef INCLUDE_CONFIG_FILE
478 if (textdump_do_config)
479 textdump_dump_config(di);
480 #endif
481 if (textdump_do_msgbuf)
482 textdump_dump_msgbuf(di);
483 if (textdump_do_panic && KERNEL_PANICKED())
484 textdump_dump_panic(di);
485 if (textdump_do_version)
486 textdump_dump_version(di);
487
488 /*
489 * Now that we know the true size, we can write out the header, then
490 * seek back to the end and rewrite the trailer with the correct
491 * size.
492 */
493 dumplen = trailer_offset - (textdump_offset + TEXTDUMP_BLOCKSIZE);
494 dump_init_header(di, &kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION,
495 dumplen);
496 (void)textdump_writenextblock(di, (char *)&kdh);
497 textdump_restoreoff(trailer_offset);
498 (void)textdump_writenextblock(di, (char *)&kdh);
499
500 /*
501 * Terminate the dump, report any errors, and clear the pending flag.
502 */
503 if (textdump_error == 0)
504 (void)dump_write(di, NULL, 0, 0);
505 if (textdump_error == ENOSPC)
506 printf("Textdump: Insufficient space on dump partition\n");
507 else if (textdump_error != 0)
508 printf("Textdump: Error %d writing dump\n", textdump_error);
509 else
510 printf("Textdump complete.\n");
511 textdump_pending = 0;
512
513 /*
514 * Restore EKCD status.
515 */
516 di->kdcrypto = kdc;
517 }
518
519 /*-
520 * DDB(4) command to manage textdumps:
521 *
522 * textdump set - request a textdump
523 * textdump status - print DDB output textdump status
524 * textdump unset - clear textdump request
525 */
526 static void
527 db_textdump_usage(void)
528 {
529
530 db_printf("textdump [unset|set|status|dump]\n");
531 }
532
533 void
534 db_textdump_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
535 {
536 int t;
537
538 t = db_read_token();
539 if (t != tIDENT) {
540 db_textdump_usage();
541 return;
542 }
543 if (db_read_token() != tEOL) {
544 db_textdump_usage();
545 return;
546 }
547 if (strcmp(db_tok_string, "set") == 0) {
548 textdump_pending = 1;
549 db_printf("textdump set\n");
550 } else if (strcmp(db_tok_string, "status") == 0) {
551 if (textdump_pending)
552 db_printf("textdump is set\n");
553 else
554 db_printf("textdump is not set\n");
555 } else if (strcmp(db_tok_string, "unset") == 0) {
556 textdump_pending = 0;
557 db_printf("textdump unset\n");
558 } else if (strcmp(db_tok_string, "dump") == 0) {
559 textdump_pending = 1;
560 doadump(true);
561 } else {
562 db_textdump_usage();
563 }
564 }
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