xref: /openbmc/linux/fs/pstore/platform.c (revision 7e60e389) 
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/module.h>
18 #include <linux/pstore.h>
19 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
20 #include <linux/lzo.h>
21 #endif
22 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
23 #include <linux/lz4.h>
24 #endif
25 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
26 #include <linux/zstd.h>
27 #endif
28 #include <linux/crypto.h>
29 #include <linux/string.h>
30 #include <linux/timer.h>
31 #include <linux/slab.h>
32 #include <linux/uaccess.h>
33 #include <linux/jiffies.h>
34 #include <linux/workqueue.h>
35 
36 #include "internal.h"
37 
38 /*
39  * We defer making "oops" entries appear in pstore - see
40  * whether the system is actually still running well enough
41  * to let someone see the entry
42  */
43 static int pstore_update_ms = -1;
44 module_param_named(update_ms, pstore_update_ms, int, 0600);
45 MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
46 		 "(default is -1, which means runtime updates are disabled; "
47 		 "enabling this option may not be safe; it may lead to further "
48 		 "corruption on Oopses)");
49 
50 /* Names should be in the same order as the enum pstore_type_id */
51 static const char * const pstore_type_names[] = {
52 	"dmesg",
53 	"mce",
54 	"console",
55 	"ftrace",
56 	"rtas",
57 	"powerpc-ofw",
58 	"powerpc-common",
59 	"pmsg",
60 	"powerpc-opal",
61 };
62 
63 static int pstore_new_entry;
64 
65 static void pstore_timefunc(struct timer_list *);
66 static DEFINE_TIMER(pstore_timer, pstore_timefunc);
67 
68 static void pstore_dowork(struct work_struct *);
69 static DECLARE_WORK(pstore_work, pstore_dowork);
70 
71 /*
72  * psinfo_lock protects "psinfo" during calls to
73  * pstore_register(), pstore_unregister(), and
74  * the filesystem mount/unmount routines.
75  */
76 static DEFINE_MUTEX(psinfo_lock);
77 struct pstore_info *psinfo;
78 
79 static char *backend;
80 module_param(backend, charp, 0444);
81 MODULE_PARM_DESC(backend, "specific backend to use");
82 
83 static char *compress =
84 #ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
85 		CONFIG_PSTORE_COMPRESS_DEFAULT;
86 #else
87 		NULL;
88 #endif
89 module_param(compress, charp, 0444);
90 MODULE_PARM_DESC(compress, "compression to use");
91 
92 /* Compression parameters */
93 static struct crypto_comp *tfm;
94 
95 struct pstore_zbackend {
96 	int (*zbufsize)(size_t size);
97 	const char *name;
98 };
99 
100 static char *big_oops_buf;
101 static size_t big_oops_buf_sz;
102 
103 /* How much of the console log to snapshot */
104 unsigned long kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES;
105 
106 void pstore_set_kmsg_bytes(int bytes)
107 {
108 	kmsg_bytes = bytes;
109 }
110 
111 /* Tag each group of saved records with a sequence number */
112 static int	oopscount;
113 
114 const char *pstore_type_to_name(enum pstore_type_id type)
115 {
116 	BUILD_BUG_ON(ARRAY_SIZE(pstore_type_names) != PSTORE_TYPE_MAX);
117 
118 	if (WARN_ON_ONCE(type >= PSTORE_TYPE_MAX))
119 		return "unknown";
120 
121 	return pstore_type_names[type];
122 }
123 EXPORT_SYMBOL_GPL(pstore_type_to_name);
124 
125 enum pstore_type_id pstore_name_to_type(const char *name)
126 {
127 	int i;
128 
129 	for (i = 0; i < PSTORE_TYPE_MAX; i++) {
130 		if (!strcmp(pstore_type_names[i], name))
131 			return i;
132 	}
133 
134 	return PSTORE_TYPE_MAX;
135 }
136 EXPORT_SYMBOL_GPL(pstore_name_to_type);
137 
138 static void pstore_timer_kick(void)
139 {
140 	if (pstore_update_ms < 0)
141 		return;
142 
143 	mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
144 }
145 
146 /*
147  * Should pstore_dump() wait for a concurrent pstore_dump()? If
148  * not, the current pstore_dump() will report a failure to dump
149  * and return.
150  */
151 static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
152 {
153 	/* In NMI path, pstore shouldn't block regardless of reason. */
154 	if (in_nmi())
155 		return true;
156 
157 	switch (reason) {
158 	/* In panic case, other cpus are stopped by smp_send_stop(). */
159 	case KMSG_DUMP_PANIC:
160 	/* Emergency restart shouldn't be blocked. */
161 	case KMSG_DUMP_EMERG:
162 		return true;
163 	default:
164 		return false;
165 	}
166 }
167 
168 #if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
169 static int zbufsize_deflate(size_t size)
170 {
171 	size_t cmpr;
172 
173 	switch (size) {
174 	/* buffer range for efivars */
175 	case 1000 ... 2000:
176 		cmpr = 56;
177 		break;
178 	case 2001 ... 3000:
179 		cmpr = 54;
180 		break;
181 	case 3001 ... 3999:
182 		cmpr = 52;
183 		break;
184 	/* buffer range for nvram, erst */
185 	case 4000 ... 10000:
186 		cmpr = 45;
187 		break;
188 	default:
189 		cmpr = 60;
190 		break;
191 	}
192 
193 	return (size * 100) / cmpr;
194 }
195 #endif
196 
197 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
198 static int zbufsize_lzo(size_t size)
199 {
200 	return lzo1x_worst_compress(size);
201 }
202 #endif
203 
204 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
205 static int zbufsize_lz4(size_t size)
206 {
207 	return LZ4_compressBound(size);
208 }
209 #endif
210 
211 #if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
212 static int zbufsize_842(size_t size)
213 {
214 	return size;
215 }
216 #endif
217 
218 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
219 static int zbufsize_zstd(size_t size)
220 {
221 	return ZSTD_compressBound(size);
222 }
223 #endif
224 
225 static const struct pstore_zbackend *zbackend __ro_after_init;
226 
227 static const struct pstore_zbackend zbackends[] = {
228 #if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
229 	{
230 		.zbufsize	= zbufsize_deflate,
231 		.name		= "deflate",
232 	},
233 #endif
234 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
235 	{
236 		.zbufsize	= zbufsize_lzo,
237 		.name		= "lzo",
238 	},
239 #endif
240 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS)
241 	{
242 		.zbufsize	= zbufsize_lz4,
243 		.name		= "lz4",
244 	},
245 #endif
246 #if IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
247 	{
248 		.zbufsize	= zbufsize_lz4,
249 		.name		= "lz4hc",
250 	},
251 #endif
252 #if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
253 	{
254 		.zbufsize	= zbufsize_842,
255 		.name		= "842",
256 	},
257 #endif
258 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
259 	{
260 		.zbufsize	= zbufsize_zstd,
261 		.name		= "zstd",
262 	},
263 #endif
264 	{ }
265 };
266 
267 static int pstore_compress(const void *in, void *out,
268 			   unsigned int inlen, unsigned int outlen)
269 {
270 	int ret;
271 
272 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESSION))
273 		return -EINVAL;
274 
275 	ret = crypto_comp_compress(tfm, in, inlen, out, &outlen);
276 	if (ret) {
277 		pr_err("crypto_comp_compress failed, ret = %d!\n", ret);
278 		return ret;
279 	}
280 
281 	return outlen;
282 }
283 
284 static void allocate_buf_for_compression(void)
285 {
286 	struct crypto_comp *ctx;
287 	int size;
288 	char *buf;
289 
290 	/* Skip if not built-in or compression backend not selected yet. */
291 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
292 		return;
293 
294 	/* Skip if no pstore backend yet or compression init already done. */
295 	if (!psinfo || tfm)
296 		return;
297 
298 	if (!crypto_has_comp(zbackend->name, 0, 0)) {
299 		pr_err("Unknown compression: %s\n", zbackend->name);
300 		return;
301 	}
302 
303 	size = zbackend->zbufsize(psinfo->bufsize);
304 	if (size <= 0) {
305 		pr_err("Invalid compression size for %s: %d\n",
306 		       zbackend->name, size);
307 		return;
308 	}
309 
310 	buf = kmalloc(size, GFP_KERNEL);
311 	if (!buf) {
312 		pr_err("Failed %d byte compression buffer allocation for: %s\n",
313 		       size, zbackend->name);
314 		return;
315 	}
316 
317 	ctx = crypto_alloc_comp(zbackend->name, 0, 0);
318 	if (IS_ERR_OR_NULL(ctx)) {
319 		kfree(buf);
320 		pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
321 		       PTR_ERR(ctx));
322 		return;
323 	}
324 
325 	/* A non-NULL big_oops_buf indicates compression is available. */
326 	tfm = ctx;
327 	big_oops_buf_sz = size;
328 	big_oops_buf = buf;
329 
330 	pr_info("Using crash dump compression: %s\n", zbackend->name);
331 }
332 
333 static void free_buf_for_compression(void)
334 {
335 	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm) {
336 		crypto_free_comp(tfm);
337 		tfm = NULL;
338 	}
339 	kfree(big_oops_buf);
340 	big_oops_buf = NULL;
341 	big_oops_buf_sz = 0;
342 }
343 
344 /*
345  * Called when compression fails, since the printk buffer
346  * would be fetched for compression calling it again when
347  * compression fails would have moved the iterator of
348  * printk buffer which results in fetching old contents.
349  * Copy the recent messages from big_oops_buf to psinfo->buf
350  */
351 static size_t copy_kmsg_to_buffer(int hsize, size_t len)
352 {
353 	size_t total_len;
354 	size_t diff;
355 
356 	total_len = hsize + len;
357 
358 	if (total_len > psinfo->bufsize) {
359 		diff = total_len - psinfo->bufsize + hsize;
360 		memcpy(psinfo->buf, big_oops_buf, hsize);
361 		memcpy(psinfo->buf + hsize, big_oops_buf + diff,
362 					psinfo->bufsize - hsize);
363 		total_len = psinfo->bufsize;
364 	} else
365 		memcpy(psinfo->buf, big_oops_buf, total_len);
366 
367 	return total_len;
368 }
369 
370 void pstore_record_init(struct pstore_record *record,
371 			struct pstore_info *psinfo)
372 {
373 	memset(record, 0, sizeof(*record));
374 
375 	record->psi = psinfo;
376 
377 	/* Report zeroed timestamp if called before timekeeping has resumed. */
378 	record->time = ns_to_timespec64(ktime_get_real_fast_ns());
379 }
380 
381 /*
382  * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from the
383  * end of the buffer.
384  */
385 static void pstore_dump(struct kmsg_dumper *dumper,
386 			enum kmsg_dump_reason reason)
387 {
388 	unsigned long	total = 0;
389 	const char	*why;
390 	unsigned int	part = 1;
391 	int		ret;
392 
393 	why = kmsg_dump_reason_str(reason);
394 
395 	if (down_trylock(&psinfo->buf_lock)) {
396 		/* Failed to acquire lock: give up if we cannot wait. */
397 		if (pstore_cannot_wait(reason)) {
398 			pr_err("dump skipped in %s path: may corrupt error record\n",
399 				in_nmi() ? "NMI" : why);
400 			return;
401 		}
402 		if (down_interruptible(&psinfo->buf_lock)) {
403 			pr_err("could not grab semaphore?!\n");
404 			return;
405 		}
406 	}
407 
408 	oopscount++;
409 	while (total < kmsg_bytes) {
410 		char *dst;
411 		size_t dst_size;
412 		int header_size;
413 		int zipped_len = -1;
414 		size_t dump_size;
415 		struct pstore_record record;
416 
417 		pstore_record_init(&record, psinfo);
418 		record.type = PSTORE_TYPE_DMESG;
419 		record.count = oopscount;
420 		record.reason = reason;
421 		record.part = part;
422 		record.buf = psinfo->buf;
423 
424 		if (big_oops_buf) {
425 			dst = big_oops_buf;
426 			dst_size = big_oops_buf_sz;
427 		} else {
428 			dst = psinfo->buf;
429 			dst_size = psinfo->bufsize;
430 		}
431 
432 		/* Write dump header. */
433 		header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
434 				 oopscount, part);
435 		dst_size -= header_size;
436 
437 		/* Write dump contents. */
438 		if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
439 					  dst_size, &dump_size))
440 			break;
441 
442 		if (big_oops_buf) {
443 			zipped_len = pstore_compress(dst, psinfo->buf,
444 						header_size + dump_size,
445 						psinfo->bufsize);
446 
447 			if (zipped_len > 0) {
448 				record.compressed = true;
449 				record.size = zipped_len;
450 			} else {
451 				record.size = copy_kmsg_to_buffer(header_size,
452 								  dump_size);
453 			}
454 		} else {
455 			record.size = header_size + dump_size;
456 		}
457 
458 		ret = psinfo->write(&record);
459 		if (ret == 0 && reason == KMSG_DUMP_OOPS) {
460 			pstore_new_entry = 1;
461 			pstore_timer_kick();
462 		}
463 
464 		total += record.size;
465 		part++;
466 	}
467 
468 	up(&psinfo->buf_lock);
469 }
470 
471 static struct kmsg_dumper pstore_dumper = {
472 	.dump = pstore_dump,
473 };
474 
475 /*
476  * Register with kmsg_dump to save last part of console log on panic.
477  */
478 static void pstore_register_kmsg(void)
479 {
480 	kmsg_dump_register(&pstore_dumper);
481 }
482 
483 static void pstore_unregister_kmsg(void)
484 {
485 	kmsg_dump_unregister(&pstore_dumper);
486 }
487 
488 #ifdef CONFIG_PSTORE_CONSOLE
489 static void pstore_console_write(struct console *con, const char *s, unsigned c)
490 {
491 	struct pstore_record record;
492 
493 	if (!c)
494 		return;
495 
496 	pstore_record_init(&record, psinfo);
497 	record.type = PSTORE_TYPE_CONSOLE;
498 
499 	record.buf = (char *)s;
500 	record.size = c;
501 	psinfo->write(&record);
502 }
503 
504 static struct console pstore_console = {
505 	.write	= pstore_console_write,
506 	.index	= -1,
507 };
508 
509 static void pstore_register_console(void)
510 {
511 	/* Show which backend is going to get console writes. */
512 	strscpy(pstore_console.name, psinfo->name,
513 		sizeof(pstore_console.name));
514 	/*
515 	 * Always initialize flags here since prior unregister_console()
516 	 * calls may have changed settings (specifically CON_ENABLED).
517 	 */
518 	pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME;
519 	register_console(&pstore_console);
520 }
521 
522 static void pstore_unregister_console(void)
523 {
524 	unregister_console(&pstore_console);
525 }
526 #else
527 static void pstore_register_console(void) {}
528 static void pstore_unregister_console(void) {}
529 #endif
530 
531 static int pstore_write_user_compat(struct pstore_record *record,
532 				    const char __user *buf)
533 {
534 	int ret = 0;
535 
536 	if (record->buf)
537 		return -EINVAL;
538 
539 	record->buf = memdup_user(buf, record->size);
540 	if (IS_ERR(record->buf)) {
541 		ret = PTR_ERR(record->buf);
542 		goto out;
543 	}
544 
545 	ret = record->psi->write(record);
546 
547 	kfree(record->buf);
548 out:
549 	record->buf = NULL;
550 
551 	return unlikely(ret < 0) ? ret : record->size;
552 }
553 
554 /*
555  * platform specific persistent storage driver registers with
556  * us here. If pstore is already mounted, call the platform
557  * read function right away to populate the file system. If not
558  * then the pstore mount code will call us later to fill out
559  * the file system.
560  */
561 int pstore_register(struct pstore_info *psi)
562 {
563 	if (backend && strcmp(backend, psi->name)) {
564 		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
565 		return -EPERM;
566 	}
567 
568 	/* Sanity check flags. */
569 	if (!psi->flags) {
570 		pr_warn("backend '%s' must support at least one frontend\n",
571 			psi->name);
572 		return -EINVAL;
573 	}
574 
575 	/* Check for required functions. */
576 	if (!psi->read || !psi->write) {
577 		pr_warn("backend '%s' must implement read() and write()\n",
578 			psi->name);
579 		return -EINVAL;
580 	}
581 
582 	mutex_lock(&psinfo_lock);
583 	if (psinfo) {
584 		pr_warn("backend '%s' already loaded: ignoring '%s'\n",
585 			psinfo->name, psi->name);
586 		mutex_unlock(&psinfo_lock);
587 		return -EBUSY;
588 	}
589 
590 	if (!psi->write_user)
591 		psi->write_user = pstore_write_user_compat;
592 	psinfo = psi;
593 	mutex_init(&psinfo->read_mutex);
594 	sema_init(&psinfo->buf_lock, 1);
595 
596 	if (psi->flags & PSTORE_FLAGS_DMESG)
597 		allocate_buf_for_compression();
598 
599 	pstore_get_records(0);
600 
601 	if (psi->flags & PSTORE_FLAGS_DMESG) {
602 		pstore_dumper.max_reason = psinfo->max_reason;
603 		pstore_register_kmsg();
604 	}
605 	if (psi->flags & PSTORE_FLAGS_CONSOLE)
606 		pstore_register_console();
607 	if (psi->flags & PSTORE_FLAGS_FTRACE)
608 		pstore_register_ftrace();
609 	if (psi->flags & PSTORE_FLAGS_PMSG)
610 		pstore_register_pmsg();
611 
612 	/* Start watching for new records, if desired. */
613 	pstore_timer_kick();
614 
615 	/*
616 	 * Update the module parameter backend, so it is visible
617 	 * through /sys/module/pstore/parameters/backend
618 	 */
619 	backend = kstrdup(psi->name, GFP_KERNEL);
620 
621 	pr_info("Registered %s as persistent store backend\n", psi->name);
622 
623 	mutex_unlock(&psinfo_lock);
624 	return 0;
625 }
626 EXPORT_SYMBOL_GPL(pstore_register);
627 
628 void pstore_unregister(struct pstore_info *psi)
629 {
630 	/* It's okay to unregister nothing. */
631 	if (!psi)
632 		return;
633 
634 	mutex_lock(&psinfo_lock);
635 
636 	/* Only one backend can be registered at a time. */
637 	if (WARN_ON(psi != psinfo)) {
638 		mutex_unlock(&psinfo_lock);
639 		return;
640 	}
641 
642 	/* Unregister all callbacks. */
643 	if (psi->flags & PSTORE_FLAGS_PMSG)
644 		pstore_unregister_pmsg();
645 	if (psi->flags & PSTORE_FLAGS_FTRACE)
646 		pstore_unregister_ftrace();
647 	if (psi->flags & PSTORE_FLAGS_CONSOLE)
648 		pstore_unregister_console();
649 	if (psi->flags & PSTORE_FLAGS_DMESG)
650 		pstore_unregister_kmsg();
651 
652 	/* Stop timer and make sure all work has finished. */
653 	del_timer_sync(&pstore_timer);
654 	flush_work(&pstore_work);
655 
656 	/* Remove all backend records from filesystem tree. */
657 	pstore_put_backend_records(psi);
658 
659 	free_buf_for_compression();
660 
661 	psinfo = NULL;
662 	kfree(backend);
663 	backend = NULL;
664 	mutex_unlock(&psinfo_lock);
665 }
666 EXPORT_SYMBOL_GPL(pstore_unregister);
667 
668 static void decompress_record(struct pstore_record *record)
669 {
670 	int ret;
671 	int unzipped_len;
672 	char *unzipped, *workspace;
673 
674 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESSION) || !record->compressed)
675 		return;
676 
677 	/* Only PSTORE_TYPE_DMESG support compression. */
678 	if (record->type != PSTORE_TYPE_DMESG) {
679 		pr_warn("ignored compressed record type %d\n", record->type);
680 		return;
681 	}
682 
683 	/* Missing compression buffer means compression was not initialized. */
684 	if (!big_oops_buf) {
685 		pr_warn("no decompression method initialized!\n");
686 		return;
687 	}
688 
689 	/* Allocate enough space to hold max decompression and ECC. */
690 	unzipped_len = big_oops_buf_sz;
691 	workspace = kmalloc(unzipped_len + record->ecc_notice_size,
692 			    GFP_KERNEL);
693 	if (!workspace)
694 		return;
695 
696 	/* After decompression "unzipped_len" is almost certainly smaller. */
697 	ret = crypto_comp_decompress(tfm, record->buf, record->size,
698 					  workspace, &unzipped_len);
699 	if (ret) {
700 		pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
701 		kfree(workspace);
702 		return;
703 	}
704 
705 	/* Append ECC notice to decompressed buffer. */
706 	memcpy(workspace + unzipped_len, record->buf + record->size,
707 	       record->ecc_notice_size);
708 
709 	/* Copy decompressed contents into an minimum-sized allocation. */
710 	unzipped = kmemdup(workspace, unzipped_len + record->ecc_notice_size,
711 			   GFP_KERNEL);
712 	kfree(workspace);
713 	if (!unzipped)
714 		return;
715 
716 	/* Swap out compressed contents with decompressed contents. */
717 	kfree(record->buf);
718 	record->buf = unzipped;
719 	record->size = unzipped_len;
720 	record->compressed = false;
721 }
722 
723 /*
724  * Read all the records from one persistent store backend. Create
725  * files in our filesystem.  Don't warn about -EEXIST errors
726  * when we are re-scanning the backing store looking to add new
727  * error records.
728  */
729 void pstore_get_backend_records(struct pstore_info *psi,
730 				struct dentry *root, int quiet)
731 {
732 	int failed = 0;
733 	unsigned int stop_loop = 65536;
734 
735 	if (!psi || !root)
736 		return;
737 
738 	mutex_lock(&psi->read_mutex);
739 	if (psi->open && psi->open(psi))
740 		goto out;
741 
742 	/*
743 	 * Backend callback read() allocates record.buf. decompress_record()
744 	 * may reallocate record.buf. On success, pstore_mkfile() will keep
745 	 * the record.buf, so free it only on failure.
746 	 */
747 	for (; stop_loop; stop_loop--) {
748 		struct pstore_record *record;
749 		int rc;
750 
751 		record = kzalloc(sizeof(*record), GFP_KERNEL);
752 		if (!record) {
753 			pr_err("out of memory creating record\n");
754 			break;
755 		}
756 		pstore_record_init(record, psi);
757 
758 		record->size = psi->read(record);
759 
760 		/* No more records left in backend? */
761 		if (record->size <= 0) {
762 			kfree(record);
763 			break;
764 		}
765 
766 		decompress_record(record);
767 		rc = pstore_mkfile(root, record);
768 		if (rc) {
769 			/* pstore_mkfile() did not take record, so free it. */
770 			kfree(record->buf);
771 			kfree(record);
772 			if (rc != -EEXIST || !quiet)
773 				failed++;
774 		}
775 	}
776 	if (psi->close)
777 		psi->close(psi);
778 out:
779 	mutex_unlock(&psi->read_mutex);
780 
781 	if (failed)
782 		pr_warn("failed to create %d record(s) from '%s'\n",
783 			failed, psi->name);
784 	if (!stop_loop)
785 		pr_err("looping? Too many records seen from '%s'\n",
786 			psi->name);
787 }
788 
789 static void pstore_dowork(struct work_struct *work)
790 {
791 	pstore_get_records(1);
792 }
793 
794 static void pstore_timefunc(struct timer_list *unused)
795 {
796 	if (pstore_new_entry) {
797 		pstore_new_entry = 0;
798 		schedule_work(&pstore_work);
799 	}
800 
801 	pstore_timer_kick();
802 }
803 
804 static void __init pstore_choose_compression(void)
805 {
806 	const struct pstore_zbackend *step;
807 
808 	if (!compress)
809 		return;
810 
811 	for (step = zbackends; step->name; step++) {
812 		if (!strcmp(compress, step->name)) {
813 			zbackend = step;
814 			return;
815 		}
816 	}
817 }
818 
819 static int __init pstore_init(void)
820 {
821 	int ret;
822 
823 	pstore_choose_compression();
824 
825 	/*
826 	 * Check if any pstore backends registered earlier but did not
827 	 * initialize compression because crypto was not ready. If so,
828 	 * initialize compression now.
829 	 */
830 	allocate_buf_for_compression();
831 
832 	ret = pstore_init_fs();
833 	if (ret)
834 		free_buf_for_compression();
835 
836 	return ret;
837 }
838 late_initcall(pstore_init);
839 
840 static void __exit pstore_exit(void)
841 {
842 	pstore_exit_fs();
843 }
844 module_exit(pstore_exit)
845 
846 MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
847 MODULE_LICENSE("GPL");
848