1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Persistent Storage - platform driver interface parts. 4 * 5 * Copyright (C) 2007-2008 Google, Inc. 6 * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com> 7 */ 8 9 #define pr_fmt(fmt) "pstore: " fmt 10 11 #include <linux/atomic.h> 12 #include <linux/types.h> 13 #include <linux/errno.h> 14 #include <linux/init.h> 15 #include <linux/kmsg_dump.h> 16 #include <linux/console.h> 17 #include <linux/mm.h> 18 #include <linux/module.h> 19 #include <linux/pstore.h> 20 #include <linux/string.h> 21 #include <linux/timer.h> 22 #include <linux/slab.h> 23 #include <linux/uaccess.h> 24 #include <linux/jiffies.h> 25 #include <linux/vmalloc.h> 26 #include <linux/workqueue.h> 27 #include <linux/zlib.h> 28 29 #include "internal.h" 30 31 /* 32 * We defer making "oops" entries appear in pstore - see 33 * whether the system is actually still running well enough 34 * to let someone see the entry 35 */ 36 static int pstore_update_ms = -1; 37 module_param_named(update_ms, pstore_update_ms, int, 0600); 38 MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content " 39 "(default is -1, which means runtime updates are disabled; " 40 "enabling this option may not be safe; it may lead to further " 41 "corruption on Oopses)"); 42 43 /* Names should be in the same order as the enum pstore_type_id */ 44 static const char * const pstore_type_names[] = { 45 "dmesg", 46 "mce", 47 "console", 48 "ftrace", 49 "rtas", 50 "powerpc-ofw", 51 "powerpc-common", 52 "pmsg", 53 "powerpc-opal", 54 }; 55 56 static int pstore_new_entry; 57 58 static void pstore_timefunc(struct timer_list *); 59 static DEFINE_TIMER(pstore_timer, pstore_timefunc); 60 61 static void pstore_dowork(struct work_struct *); 62 static DECLARE_WORK(pstore_work, pstore_dowork); 63 64 /* 65 * psinfo_lock protects "psinfo" during calls to 66 * pstore_register(), pstore_unregister(), and 67 * the filesystem mount/unmount routines. 68 */ 69 static DEFINE_MUTEX(psinfo_lock); 70 struct pstore_info *psinfo; 71 72 static char *backend; 73 module_param(backend, charp, 0444); 74 MODULE_PARM_DESC(backend, "specific backend to use"); 75 76 /* 77 * pstore no longer implements compression via the crypto API, and only 78 * supports zlib deflate compression implemented using the zlib library 79 * interface. This removes additional complexity which is hard to justify for a 80 * diagnostic facility that has to operate in conditions where the system may 81 * have become unstable. Zlib deflate is comparatively small in terms of code 82 * size, and compresses ASCII text comparatively well. In terms of compression 83 * speed, deflate is not the best performer but for recording the log output on 84 * a kernel panic, this is not considered critical. 85 * 86 * The only remaining arguments supported by the compress= module parameter are 87 * 'deflate' and 'none'. To retain compatibility with existing installations, 88 * all other values are logged and replaced with 'deflate'. 89 */ 90 static char *compress = "deflate"; 91 module_param(compress, charp, 0444); 92 MODULE_PARM_DESC(compress, "compression to use"); 93 94 /* How much of the kernel log to snapshot */ 95 unsigned long kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES; 96 module_param(kmsg_bytes, ulong, 0444); 97 MODULE_PARM_DESC(kmsg_bytes, "amount of kernel log to snapshot (in bytes)"); 98 99 static void *compress_workspace; 100 101 /* 102 * Compression is only used for dmesg output, which consists of low-entropy 103 * ASCII text, and so we can assume worst-case 60%. 104 */ 105 #define DMESG_COMP_PERCENT 60 106 107 static char *big_oops_buf; 108 static size_t max_compressed_size; 109 110 void pstore_set_kmsg_bytes(int bytes) 111 { 112 kmsg_bytes = bytes; 113 } 114 115 /* Tag each group of saved records with a sequence number */ 116 static int oopscount; 117 118 const char *pstore_type_to_name(enum pstore_type_id type) 119 { 120 BUILD_BUG_ON(ARRAY_SIZE(pstore_type_names) != PSTORE_TYPE_MAX); 121 122 if (WARN_ON_ONCE(type >= PSTORE_TYPE_MAX)) 123 return "unknown"; 124 125 return pstore_type_names[type]; 126 } 127 EXPORT_SYMBOL_GPL(pstore_type_to_name); 128 129 enum pstore_type_id pstore_name_to_type(const char *name) 130 { 131 int i; 132 133 for (i = 0; i < PSTORE_TYPE_MAX; i++) { 134 if (!strcmp(pstore_type_names[i], name)) 135 return i; 136 } 137 138 return PSTORE_TYPE_MAX; 139 } 140 EXPORT_SYMBOL_GPL(pstore_name_to_type); 141 142 static void pstore_timer_kick(void) 143 { 144 if (pstore_update_ms < 0) 145 return; 146 147 mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms)); 148 } 149 150 static bool pstore_cannot_block_path(enum kmsg_dump_reason reason) 151 { 152 /* 153 * In case of NMI path, pstore shouldn't be blocked 154 * regardless of reason. 155 */ 156 if (in_nmi()) 157 return true; 158 159 switch (reason) { 160 /* In panic case, other cpus are stopped by smp_send_stop(). */ 161 case KMSG_DUMP_PANIC: 162 /* 163 * Emergency restart shouldn't be blocked by spinning on 164 * pstore_info::buf_lock. 165 */ 166 case KMSG_DUMP_EMERG: 167 return true; 168 default: 169 return false; 170 } 171 } 172 173 static int pstore_compress(const void *in, void *out, 174 unsigned int inlen, unsigned int outlen) 175 { 176 struct z_stream_s zstream = { 177 .next_in = in, 178 .avail_in = inlen, 179 .next_out = out, 180 .avail_out = outlen, 181 .workspace = compress_workspace, 182 }; 183 int ret; 184 185 if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS)) 186 return -EINVAL; 187 188 ret = zlib_deflateInit2(&zstream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, 189 -MAX_WBITS, DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY); 190 if (ret != Z_OK) 191 return -EINVAL; 192 193 ret = zlib_deflate(&zstream, Z_FINISH); 194 if (ret != Z_STREAM_END) 195 return -EINVAL; 196 197 ret = zlib_deflateEnd(&zstream); 198 if (ret != Z_OK) 199 pr_warn_once("zlib_deflateEnd() failed: %d\n", ret); 200 201 return zstream.total_out; 202 } 203 204 static void allocate_buf_for_compression(void) 205 { 206 size_t compressed_size; 207 char *buf; 208 209 /* Skip if not built-in or compression disabled. */ 210 if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !compress || 211 !strcmp(compress, "none")) { 212 compress = NULL; 213 return; 214 } 215 216 if (strcmp(compress, "deflate")) { 217 pr_err("Unsupported compression '%s', falling back to deflate\n", 218 compress); 219 compress = "deflate"; 220 } 221 222 /* 223 * The compression buffer only needs to be as large as the maximum 224 * uncompressed record size, since any record that would be expanded by 225 * compression is just stored uncompressed. 226 */ 227 compressed_size = (psinfo->bufsize * 100) / DMESG_COMP_PERCENT; 228 buf = kvzalloc(compressed_size, GFP_KERNEL); 229 if (!buf) { 230 pr_err("Failed %zu byte compression buffer allocation for: %s\n", 231 psinfo->bufsize, compress); 232 return; 233 } 234 235 compress_workspace = 236 vmalloc(zlib_deflate_workspacesize(MAX_WBITS, DEF_MEM_LEVEL)); 237 if (!compress_workspace) { 238 pr_err("Failed to allocate zlib deflate workspace\n"); 239 kvfree(buf); 240 return; 241 } 242 243 /* A non-NULL big_oops_buf indicates compression is available. */ 244 big_oops_buf = buf; 245 max_compressed_size = compressed_size; 246 247 pr_info("Using crash dump compression: %s\n", compress); 248 } 249 250 static void free_buf_for_compression(void) 251 { 252 if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress_workspace) { 253 vfree(compress_workspace); 254 compress_workspace = NULL; 255 } 256 257 kvfree(big_oops_buf); 258 big_oops_buf = NULL; 259 max_compressed_size = 0; 260 } 261 262 void pstore_record_init(struct pstore_record *record, 263 struct pstore_info *psinfo) 264 { 265 memset(record, 0, sizeof(*record)); 266 267 record->psi = psinfo; 268 269 /* Report zeroed timestamp if called before timekeeping has resumed. */ 270 record->time = ns_to_timespec64(ktime_get_real_fast_ns()); 271 } 272 273 /* 274 * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from the 275 * end of the buffer. 276 */ 277 static void pstore_dump(struct kmsg_dumper *dumper, 278 enum kmsg_dump_reason reason) 279 { 280 struct kmsg_dump_iter iter; 281 unsigned long total = 0; 282 const char *why; 283 unsigned int part = 1; 284 unsigned long flags = 0; 285 int saved_ret = 0; 286 int ret; 287 288 why = kmsg_dump_reason_str(reason); 289 290 if (pstore_cannot_block_path(reason)) { 291 if (!spin_trylock_irqsave(&psinfo->buf_lock, flags)) { 292 pr_err("dump skipped in %s path because of concurrent dump\n", 293 in_nmi() ? "NMI" : why); 294 return; 295 } 296 } else { 297 spin_lock_irqsave(&psinfo->buf_lock, flags); 298 } 299 300 kmsg_dump_rewind(&iter); 301 302 oopscount++; 303 while (total < kmsg_bytes) { 304 char *dst; 305 size_t dst_size; 306 int header_size; 307 int zipped_len = -1; 308 size_t dump_size; 309 struct pstore_record record; 310 311 pstore_record_init(&record, psinfo); 312 record.type = PSTORE_TYPE_DMESG; 313 record.count = oopscount; 314 record.reason = reason; 315 record.part = part; 316 record.buf = psinfo->buf; 317 318 dst = big_oops_buf ?: psinfo->buf; 319 dst_size = max_compressed_size ?: psinfo->bufsize; 320 321 /* Write dump header. */ 322 header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why, 323 oopscount, part); 324 dst_size -= header_size; 325 326 /* Write dump contents. */ 327 if (!kmsg_dump_get_buffer(&iter, true, dst + header_size, 328 dst_size, &dump_size)) 329 break; 330 331 if (big_oops_buf) { 332 zipped_len = pstore_compress(dst, psinfo->buf, 333 header_size + dump_size, 334 psinfo->bufsize); 335 336 if (zipped_len > 0) { 337 record.compressed = true; 338 record.size = zipped_len; 339 } else { 340 /* 341 * Compression failed, so the buffer is most 342 * likely filled with binary data that does not 343 * compress as well as ASCII text. Copy as much 344 * of the uncompressed data as possible into 345 * the pstore record, and discard the rest. 346 */ 347 record.size = psinfo->bufsize; 348 memcpy(psinfo->buf, dst, psinfo->bufsize); 349 } 350 } else { 351 record.size = header_size + dump_size; 352 } 353 354 ret = psinfo->write(&record); 355 if (ret == 0 && reason == KMSG_DUMP_OOPS) { 356 pstore_new_entry = 1; 357 pstore_timer_kick(); 358 } else { 359 /* Preserve only the first non-zero returned value. */ 360 if (!saved_ret) 361 saved_ret = ret; 362 } 363 364 total += record.size; 365 part++; 366 } 367 spin_unlock_irqrestore(&psinfo->buf_lock, flags); 368 369 if (saved_ret) { 370 pr_err_once("backend (%s) writing error (%d)\n", psinfo->name, 371 saved_ret); 372 } 373 } 374 375 static struct kmsg_dumper pstore_dumper = { 376 .dump = pstore_dump, 377 }; 378 379 /* 380 * Register with kmsg_dump to save last part of console log on panic. 381 */ 382 static void pstore_register_kmsg(void) 383 { 384 kmsg_dump_register(&pstore_dumper); 385 } 386 387 static void pstore_unregister_kmsg(void) 388 { 389 kmsg_dump_unregister(&pstore_dumper); 390 } 391 392 #ifdef CONFIG_PSTORE_CONSOLE 393 static void pstore_console_write(struct console *con, const char *s, unsigned c) 394 { 395 struct pstore_record record; 396 397 if (!c) 398 return; 399 400 pstore_record_init(&record, psinfo); 401 record.type = PSTORE_TYPE_CONSOLE; 402 403 record.buf = (char *)s; 404 record.size = c; 405 psinfo->write(&record); 406 } 407 408 static struct console pstore_console = { 409 .write = pstore_console_write, 410 .index = -1, 411 }; 412 413 static void pstore_register_console(void) 414 { 415 /* Show which backend is going to get console writes. */ 416 strscpy(pstore_console.name, psinfo->name, 417 sizeof(pstore_console.name)); 418 /* 419 * Always initialize flags here since prior unregister_console() 420 * calls may have changed settings (specifically CON_ENABLED). 421 */ 422 pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME; 423 register_console(&pstore_console); 424 } 425 426 static void pstore_unregister_console(void) 427 { 428 unregister_console(&pstore_console); 429 } 430 #else 431 static void pstore_register_console(void) {} 432 static void pstore_unregister_console(void) {} 433 #endif 434 435 static int pstore_write_user_compat(struct pstore_record *record, 436 const char __user *buf) 437 { 438 int ret = 0; 439 440 if (record->buf) 441 return -EINVAL; 442 443 record->buf = vmemdup_user(buf, record->size); 444 if (IS_ERR(record->buf)) { 445 ret = PTR_ERR(record->buf); 446 goto out; 447 } 448 449 ret = record->psi->write(record); 450 451 kvfree(record->buf); 452 out: 453 record->buf = NULL; 454 455 return unlikely(ret < 0) ? ret : record->size; 456 } 457 458 /* 459 * platform specific persistent storage driver registers with 460 * us here. If pstore is already mounted, call the platform 461 * read function right away to populate the file system. If not 462 * then the pstore mount code will call us later to fill out 463 * the file system. 464 */ 465 int pstore_register(struct pstore_info *psi) 466 { 467 char *new_backend; 468 469 if (backend && strcmp(backend, psi->name)) { 470 pr_warn("backend '%s' already in use: ignoring '%s'\n", 471 backend, psi->name); 472 return -EBUSY; 473 } 474 475 /* Sanity check flags. */ 476 if (!psi->flags) { 477 pr_warn("backend '%s' must support at least one frontend\n", 478 psi->name); 479 return -EINVAL; 480 } 481 482 /* Check for required functions. */ 483 if (!psi->read || !psi->write) { 484 pr_warn("backend '%s' must implement read() and write()\n", 485 psi->name); 486 return -EINVAL; 487 } 488 489 new_backend = kstrdup(psi->name, GFP_KERNEL); 490 if (!new_backend) 491 return -ENOMEM; 492 493 mutex_lock(&psinfo_lock); 494 if (psinfo) { 495 pr_warn("backend '%s' already loaded: ignoring '%s'\n", 496 psinfo->name, psi->name); 497 mutex_unlock(&psinfo_lock); 498 kfree(new_backend); 499 return -EBUSY; 500 } 501 502 if (!psi->write_user) 503 psi->write_user = pstore_write_user_compat; 504 psinfo = psi; 505 mutex_init(&psinfo->read_mutex); 506 spin_lock_init(&psinfo->buf_lock); 507 508 if (psi->flags & PSTORE_FLAGS_DMESG) 509 allocate_buf_for_compression(); 510 511 pstore_get_records(0); 512 513 if (psi->flags & PSTORE_FLAGS_DMESG) { 514 pstore_dumper.max_reason = psinfo->max_reason; 515 pstore_register_kmsg(); 516 } 517 if (psi->flags & PSTORE_FLAGS_CONSOLE) 518 pstore_register_console(); 519 if (psi->flags & PSTORE_FLAGS_FTRACE) 520 pstore_register_ftrace(); 521 if (psi->flags & PSTORE_FLAGS_PMSG) 522 pstore_register_pmsg(); 523 524 /* Start watching for new records, if desired. */ 525 pstore_timer_kick(); 526 527 /* 528 * Update the module parameter backend, so it is visible 529 * through /sys/module/pstore/parameters/backend 530 */ 531 backend = new_backend; 532 533 pr_info("Registered %s as persistent store backend\n", psi->name); 534 535 mutex_unlock(&psinfo_lock); 536 return 0; 537 } 538 EXPORT_SYMBOL_GPL(pstore_register); 539 540 void pstore_unregister(struct pstore_info *psi) 541 { 542 /* It's okay to unregister nothing. */ 543 if (!psi) 544 return; 545 546 mutex_lock(&psinfo_lock); 547 548 /* Only one backend can be registered at a time. */ 549 if (WARN_ON(psi != psinfo)) { 550 mutex_unlock(&psinfo_lock); 551 return; 552 } 553 554 /* Unregister all callbacks. */ 555 if (psi->flags & PSTORE_FLAGS_PMSG) 556 pstore_unregister_pmsg(); 557 if (psi->flags & PSTORE_FLAGS_FTRACE) 558 pstore_unregister_ftrace(); 559 if (psi->flags & PSTORE_FLAGS_CONSOLE) 560 pstore_unregister_console(); 561 if (psi->flags & PSTORE_FLAGS_DMESG) 562 pstore_unregister_kmsg(); 563 564 /* Stop timer and make sure all work has finished. */ 565 del_timer_sync(&pstore_timer); 566 flush_work(&pstore_work); 567 568 /* Remove all backend records from filesystem tree. */ 569 pstore_put_backend_records(psi); 570 571 free_buf_for_compression(); 572 573 psinfo = NULL; 574 kfree(backend); 575 backend = NULL; 576 577 pr_info("Unregistered %s as persistent store backend\n", psi->name); 578 mutex_unlock(&psinfo_lock); 579 } 580 EXPORT_SYMBOL_GPL(pstore_unregister); 581 582 static void decompress_record(struct pstore_record *record, 583 struct z_stream_s *zstream) 584 { 585 int ret; 586 int unzipped_len; 587 char *unzipped, *workspace; 588 size_t max_uncompressed_size; 589 590 if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !record->compressed) 591 return; 592 593 /* Only PSTORE_TYPE_DMESG support compression. */ 594 if (record->type != PSTORE_TYPE_DMESG) { 595 pr_warn("ignored compressed record type %d\n", record->type); 596 return; 597 } 598 599 /* Missing compression buffer means compression was not initialized. */ 600 if (!zstream->workspace) { 601 pr_warn("no decompression method initialized!\n"); 602 return; 603 } 604 605 ret = zlib_inflateReset(zstream); 606 if (ret != Z_OK) { 607 pr_err("zlib_inflateReset() failed, ret = %d!\n", ret); 608 return; 609 } 610 611 /* Allocate enough space to hold max decompression and ECC. */ 612 max_uncompressed_size = 3 * psinfo->bufsize; 613 workspace = kvzalloc(max_uncompressed_size + record->ecc_notice_size, 614 GFP_KERNEL); 615 if (!workspace) 616 return; 617 618 zstream->next_in = record->buf; 619 zstream->avail_in = record->size; 620 zstream->next_out = workspace; 621 zstream->avail_out = max_uncompressed_size; 622 623 ret = zlib_inflate(zstream, Z_FINISH); 624 if (ret != Z_STREAM_END) { 625 pr_err_ratelimited("zlib_inflate() failed, ret = %d!\n", ret); 626 kvfree(workspace); 627 return; 628 } 629 630 unzipped_len = zstream->total_out; 631 632 /* Append ECC notice to decompressed buffer. */ 633 memcpy(workspace + unzipped_len, record->buf + record->size, 634 record->ecc_notice_size); 635 636 /* Copy decompressed contents into an minimum-sized allocation. */ 637 unzipped = kvmemdup(workspace, unzipped_len + record->ecc_notice_size, 638 GFP_KERNEL); 639 kvfree(workspace); 640 if (!unzipped) 641 return; 642 643 /* Swap out compressed contents with decompressed contents. */ 644 kvfree(record->buf); 645 record->buf = unzipped; 646 record->size = unzipped_len; 647 record->compressed = false; 648 } 649 650 /* 651 * Read all the records from one persistent store backend. Create 652 * files in our filesystem. Don't warn about -EEXIST errors 653 * when we are re-scanning the backing store looking to add new 654 * error records. 655 */ 656 void pstore_get_backend_records(struct pstore_info *psi, 657 struct dentry *root, int quiet) 658 { 659 int failed = 0; 660 unsigned int stop_loop = 65536; 661 struct z_stream_s zstream = {}; 662 663 if (!psi || !root) 664 return; 665 666 if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) { 667 zstream.workspace = kvmalloc(zlib_inflate_workspacesize(), 668 GFP_KERNEL); 669 zlib_inflateInit2(&zstream, -DEF_WBITS); 670 } 671 672 mutex_lock(&psi->read_mutex); 673 if (psi->open && psi->open(psi)) 674 goto out; 675 676 /* 677 * Backend callback read() allocates record.buf. decompress_record() 678 * may reallocate record.buf. On success, pstore_mkfile() will keep 679 * the record.buf, so free it only on failure. 680 */ 681 for (; stop_loop; stop_loop--) { 682 struct pstore_record *record; 683 int rc; 684 685 record = kzalloc(sizeof(*record), GFP_KERNEL); 686 if (!record) { 687 pr_err("out of memory creating record\n"); 688 break; 689 } 690 pstore_record_init(record, psi); 691 692 record->size = psi->read(record); 693 694 /* No more records left in backend? */ 695 if (record->size <= 0) { 696 kfree(record); 697 break; 698 } 699 700 decompress_record(record, &zstream); 701 rc = pstore_mkfile(root, record); 702 if (rc) { 703 /* pstore_mkfile() did not take record, so free it. */ 704 kvfree(record->buf); 705 kfree(record->priv); 706 kfree(record); 707 if (rc != -EEXIST || !quiet) 708 failed++; 709 } 710 } 711 if (psi->close) 712 psi->close(psi); 713 out: 714 mutex_unlock(&psi->read_mutex); 715 716 if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) { 717 if (zlib_inflateEnd(&zstream) != Z_OK) 718 pr_warn("zlib_inflateEnd() failed\n"); 719 kvfree(zstream.workspace); 720 } 721 722 if (failed) 723 pr_warn("failed to create %d record(s) from '%s'\n", 724 failed, psi->name); 725 if (!stop_loop) 726 pr_err("looping? Too many records seen from '%s'\n", 727 psi->name); 728 } 729 730 static void pstore_dowork(struct work_struct *work) 731 { 732 pstore_get_records(1); 733 } 734 735 static void pstore_timefunc(struct timer_list *unused) 736 { 737 if (pstore_new_entry) { 738 pstore_new_entry = 0; 739 schedule_work(&pstore_work); 740 } 741 742 pstore_timer_kick(); 743 } 744 745 static int __init pstore_init(void) 746 { 747 int ret; 748 749 ret = pstore_init_fs(); 750 if (ret) 751 free_buf_for_compression(); 752 753 return ret; 754 } 755 late_initcall(pstore_init); 756 757 static void __exit pstore_exit(void) 758 { 759 pstore_exit_fs(); 760 } 761 module_exit(pstore_exit) 762 763 MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>"); 764 MODULE_LICENSE("GPL"); 765