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
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17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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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 * 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.
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
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.
55 * - Allow subsytems to register to submit files for inclusion in the text
56 * dump in a generic way.
59 #include <sys/cdefs.h>
60 __FBSDID("$FreeBSD$");
62 #include "opt_config.h"
64 #include <sys/param.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 #include <sys/vimage.h>
74 #include <ddb/db_lex.h>
76 static SYSCTL_NODE(_debug_ddb, OID_AUTO, textdump, CTLFLAG_RW, 0,
77 "DDB textdump options");
80 * Don't touch the first SIZEOF_METADATA bytes on the dump device. This is
81 * to protect us from metadata and metadata from us.
83 #define SIZEOF_METADATA (64*1024)
86 * Data is written out as a series of files in the ustar tar format. ustar
87 * is a simple streamed format consiting of a series of files prefixed with
88 * headers, and all padded to 512-byte block boundaries, which maps
89 * conveniently to our requirements.
92 char uh_filename[100];
100 char uh_linkfile[100];
107 char uh_filenameprefix[155];
112 * Various size assertions -- pretty much everything must be one block in
115 CTASSERT(sizeof(struct kerneldumpheader) == TEXTDUMP_BLOCKSIZE);
116 CTASSERT(sizeof(struct ustar_header) == TEXTDUMP_BLOCKSIZE);
119 * Is a textdump scheduled? If so, the shutdown code will invoke our dumpsys
120 * routine instead of the machine-dependent kernel dump routine.
122 int textdump_pending;
123 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, pending, CTLFLAG_RW,
124 &textdump_pending, 0,
125 "Perform textdump instead of regular kernel dump.");
128 * Various constants for tar headers and contents.
130 #define TAR_USER "root"
131 #define TAR_GROUP "wheel"
134 #define TAR_MODE "0600"
135 #define TAR_USTAR "ustar"
137 #define TAR_CONFIG_FILENAME "config.txt" /* Kernel configuration. */
138 #define TAR_MSGBUF_FILENAME "msgbuf.txt" /* Kernel messsage buffer. */
139 #define TAR_PANIC_FILENAME "panic.txt" /* Panic message. */
140 #define TAR_VERSION_FILENAME "version.txt" /* Kernel version. */
143 * Configure which files will be dumped.
145 #ifdef INCLUDE_CONFIG_FILE
146 static int textdump_do_config = 1;
147 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_config, CTLFLAG_RW,
148 &textdump_do_config, 0, "Dump kernel configuration in textdump");
151 static int textdump_do_ddb = 1;
152 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_ddb, CTLFLAG_RW,
153 &textdump_do_ddb, 0, "Dump DDB captured output in textdump");
155 static int textdump_do_msgbuf = 1;
156 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_msgbuf, CTLFLAG_RW,
157 &textdump_do_msgbuf, 0, "Dump kernel message buffer in textdump");
159 static int textdump_do_panic = 1;
160 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_panic, CTLFLAG_RW,
161 &textdump_do_panic, 0, "Dump kernel panic message in textdump");
163 static int textdump_do_version = 1;
164 SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_version, CTLFLAG_RW,
165 &textdump_do_version, 0, "Dump kernel version string in textdump");
168 * State related to incremental writing of blocks to disk.
170 static off_t textdump_offset; /* Offset of next sequential write. */
171 static int textdump_error; /* Carried write error, if any. */
174 * Statically allocate space to prepare block-sized headers and data.
176 char textdump_block_buffer[TEXTDUMP_BLOCKSIZE];
177 static struct kerneldumpheader kdh;
180 * Calculate and fill in the checksum for a ustar header.
183 ustar_checksum(struct ustar_header *uhp)
188 for (i = 0; i < sizeof(uhp->uh_sum); i++)
189 uhp->uh_sum[i] = ' ';
191 for (i = 0; i < sizeof(*uhp); i++)
192 sum += ((u_char *)uhp)[i];
193 snprintf(uhp->uh_sum, sizeof(uhp->uh_sum), "%6o", sum);
197 * Each file in the tarball has a block-sized header with its name and other,
198 * largely hard-coded, properties.
201 textdump_mkustar(char *block_buffer, const char *filename, u_int size)
203 struct ustar_header *uhp;
205 uhp = (struct ustar_header *)block_buffer;
206 bzero(uhp, sizeof(*uhp));
207 strlcpy(uhp->uh_filename, filename, sizeof(uhp->uh_filename));
208 strlcpy(uhp->uh_mode, TAR_MODE, sizeof(uhp->uh_mode));
209 snprintf(uhp->uh_size, sizeof(uhp->uh_size), "%o", size);
210 strlcpy(uhp->uh_tar_owner, TAR_UID, sizeof(uhp->uh_tar_owner));
211 strlcpy(uhp->uh_tar_group, TAR_GID, sizeof(uhp->uh_tar_group));
212 strlcpy(uhp->uh_owner, TAR_USER, sizeof(uhp->uh_owner));
213 strlcpy(uhp->uh_group, TAR_GROUP, sizeof(uhp->uh_group));
214 snprintf(uhp->uh_mtime, sizeof(uhp->uh_mtime), "%lo",
215 (unsigned long)time_second);
217 strlcpy(uhp->uh_ustar, TAR_USTAR, sizeof(uhp->uh_ustar));
222 * textdump_writeblock() writes TEXTDUMP_BLOCKSIZE-sized blocks of data to
223 * the space between di->mediaoffset and di->mediaoffset + di->mediasize. It
224 * accepts an offset relative to di->mediaoffset. If we're carrying any
225 * error from previous I/O, return that error and don't continue to try to
226 * write. Most writers ignore the error and forge ahead on the basis that
227 * there's not much you can do.
230 textdump_writeblock(struct dumperinfo *di, off_t offset, char *buffer)
234 return (textdump_error);
235 if (offset + TEXTDUMP_BLOCKSIZE > di->mediasize)
237 if (offset < SIZEOF_METADATA)
239 textdump_error = dump_write(di, buffer, 0, offset + di->mediaoffset,
241 return (textdump_error);
245 * Interfaces to save and restore the dump offset, so that printers can go
246 * back to rewrite a header if required, while avoiding their knowing about
247 * the global layout of the blocks.
249 * If we ever want to support writing textdumps to tape or other
250 * stream-oriented target, we'll need to remove this.
253 textdump_saveoff(off_t *offsetp)
256 *offsetp = textdump_offset;
260 textdump_restoreoff(off_t offset)
263 textdump_offset = offset;
267 * Interface to write the "next block" relative to the current offset; since
268 * we write backwards from the end of the partition, we subtract, but there's
269 * no reason for the caller to know this.
272 textdump_writenextblock(struct dumperinfo *di, char *buffer)
276 error = textdump_writeblock(di, textdump_offset, buffer);
277 textdump_offset -= TEXTDUMP_BLOCKSIZE;
281 #ifdef INCLUDE_CONFIG_FILE
282 extern char kernconfstring[];
285 * Dump kernel configuration.
288 textdump_dump_config(struct dumperinfo *di)
290 u_int count, fullblocks, len;
292 len = strlen(kernconfstring);
293 textdump_mkustar(textdump_block_buffer, TAR_CONFIG_FILENAME, len);
294 (void)textdump_writenextblock(di, textdump_block_buffer);
297 * Write out all full blocks directly from the string, and handle any
298 * left-over bits by copying it to out to the local buffer and
301 fullblocks = len / TEXTDUMP_BLOCKSIZE;
302 for (count = 0; count < fullblocks; count++)
303 (void)textdump_writenextblock(di, kernconfstring + count *
305 if (len % TEXTDUMP_BLOCKSIZE != 0) {
306 bzero(textdump_block_buffer, TEXTDUMP_BLOCKSIZE);
307 bcopy(kernconfstring + count * TEXTDUMP_BLOCKSIZE,
308 textdump_block_buffer, len % TEXTDUMP_BLOCKSIZE);
309 (void)textdump_writenextblock(di, textdump_block_buffer);
312 #endif /* INCLUDE_CONFIG_FILE */
315 * Dump kernel message buffer.
318 textdump_dump_msgbuf(struct dumperinfo *di)
320 off_t end_offset, tarhdr_offset;
321 u_int i, len, offset, seq, total_len;
325 * Write out a dummy tar header to advance the offset; we'll rewrite
326 * it later once we know the true size.
328 textdump_saveoff(&tarhdr_offset);
329 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME, 0);
330 (void)textdump_writenextblock(di, textdump_block_buffer);
333 * Copy out the data in small chunks, but don't copy nuls that may be
334 * present if the message buffer has not yet completely filled at
339 msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
340 while ((len = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq)) > 0) {
341 for (i = 0; i < len; i++) {
344 textdump_block_buffer[offset] = buf[i];
346 if (offset != sizeof(textdump_block_buffer))
348 (void)textdump_writenextblock(di,
349 textdump_block_buffer);
354 total_len += offset; /* Without the zero-padding. */
356 bzero(textdump_block_buffer + offset,
357 sizeof(textdump_block_buffer) - offset);
358 (void)textdump_writenextblock(di, textdump_block_buffer);
362 * Rewrite tar header to reflect how much was actually written.
364 textdump_saveoff(&end_offset);
365 textdump_restoreoff(tarhdr_offset);
366 textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME,
368 (void)textdump_writenextblock(di, textdump_block_buffer);
369 textdump_restoreoff(end_offset);
373 textdump_dump_panic(struct dumperinfo *di)
378 * Write out tar header -- we store up to one block of panic message.
380 len = min(strlen(panicstr), TEXTDUMP_BLOCKSIZE);
381 textdump_mkustar(textdump_block_buffer, TAR_PANIC_FILENAME, len);
382 (void)textdump_writenextblock(di, textdump_block_buffer);
385 * Zero-pad the panic string and write out block.
387 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
388 bcopy(panicstr, textdump_block_buffer, len);
389 (void)textdump_writenextblock(di, textdump_block_buffer);
393 textdump_dump_version(struct dumperinfo *di)
398 * Write out tar header -- at most one block of version information.
400 len = min(strlen(version), TEXTDUMP_BLOCKSIZE);
401 textdump_mkustar(textdump_block_buffer, TAR_VERSION_FILENAME, len);
402 (void)textdump_writenextblock(di, textdump_block_buffer);
405 * Zero pad the version string and write out block.
407 bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
408 bcopy(version, textdump_block_buffer, len);
409 (void)textdump_writenextblock(di, textdump_block_buffer);
413 * Commit text dump to disk.
416 textdump_dumpsys(struct dumperinfo *di)
418 off_t dumplen, trailer_offset;
420 if (di->blocksize != TEXTDUMP_BLOCKSIZE) {
421 printf("Dump partition block size (%ju) not textdump "
422 "block size (%ju)", (uintmax_t)di->blocksize,
423 (uintmax_t)TEXTDUMP_BLOCKSIZE);
428 * We don't know a priori how large the dump will be, but we do know
429 * that we need to reserve space for metadata and that we need two
430 * dump headers. Also leave room for one ustar header and one block
433 if (di->mediasize < SIZEOF_METADATA + 2 * sizeof(kdh)) {
434 printf("Insufficient space on dump partition.\n");
440 * Position the start of the dump so that we'll write the kernel dump
441 * trailer immediately before the end of the partition, and then work
442 * our way back. We will rewrite this header later to reflect the
443 * true size if things go well.
445 textdump_offset = di->mediasize - sizeof(kdh);
446 textdump_saveoff(&trailer_offset);
447 mkdumpheader(&kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, 0, TEXTDUMP_BLOCKSIZE);
448 (void)textdump_writenextblock(di, (char *)&kdh);
451 * Write a series of files in ustar format.
455 #ifdef INCLUDE_CONFIG_FILE
456 if (textdump_do_config)
457 textdump_dump_config(di);
459 if (textdump_do_msgbuf)
460 textdump_dump_msgbuf(di);
461 if (textdump_do_panic && panicstr != NULL)
462 textdump_dump_panic(di);
463 if (textdump_do_version)
464 textdump_dump_version(di);
467 * Now that we know the true size, we can write out the header, then
468 * seek back to the end and rewrite the trailer with the correct
471 dumplen = trailer_offset - (textdump_offset + TEXTDUMP_BLOCKSIZE);
472 mkdumpheader(&kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, dumplen,
474 (void)textdump_writenextblock(di, (char *)&kdh);
475 textdump_restoreoff(trailer_offset);
476 (void)textdump_writenextblock(di, (char *)&kdh);
479 * Terminate the dump, report any errors, and clear the pending flag.
481 if (textdump_error == 0)
482 (void)dump_write(di, NULL, 0, 0, 0);
483 if (textdump_error == ENOSPC)
484 printf("Insufficient space on dump partition\n");
485 else if (textdump_error != 0)
486 printf("Error %d writing dump\n", textdump_error);
488 printf("Textdump complete.\n");
489 textdump_pending = 0;
493 * DDB(4) command to manage textdumps:
495 * textdump set - request a textdump
496 * textdump status - print DDB output textdump status
497 * textdump unset - clear textdump request
500 db_textdump_usage(void)
503 db_printf("textdump [unset|set|status]\n");
507 db_textdump_cmd(db_expr_t addr, boolean_t have_addr, db_expr_t count,
517 if (db_read_token() != tEOL) {
521 if (strcmp(db_tok_string, "set") == 0) {
522 textdump_pending = 1;
523 db_printf("textdump set\n");
524 } else if (strcmp(db_tok_string, "status") == 0) {
525 if (textdump_pending)
526 db_printf("textdump is set\n");
528 db_printf("textdump is not set\n");
529 } else if (strcmp(db_tok_string, "unset") == 0) {
530 textdump_pending = 0;
531 db_printf("textdump unset\n");