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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 is not 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  * pstore_lock just protects "psinfo" during
73  * calls to pstore_register()
74  */
75 static DEFINE_SPINLOCK(pstore_lock);
76 struct pstore_info *psinfo;
77 
78 static char *backend;
79 static char *compress =
80 #ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
81 		CONFIG_PSTORE_COMPRESS_DEFAULT;
82 #else
83 		NULL;
84 #endif
85 
86 /* Compression parameters */
87 static struct crypto_comp *tfm;
88 
89 struct pstore_zbackend {
90 	int (*zbufsize)(size_t size);
91 	const char *name;
92 };
93 
94 static char *big_oops_buf;
95 static size_t big_oops_buf_sz;
96 
97 /* How much of the console log to snapshot */
98 unsigned long kmsg_bytes = PSTORE_DEFAULT_KMSG_BYTES;
99 
pstore_set_kmsg_bytes(int bytes)100 void pstore_set_kmsg_bytes(int bytes)
101 {
102 	kmsg_bytes = bytes;
103 }
104 
105 /* Tag each group of saved records with a sequence number */
106 static int	oopscount;
107 
pstore_type_to_name(enum pstore_type_id type)108 const char *pstore_type_to_name(enum pstore_type_id type)
109 {
110 	BUILD_BUG_ON(ARRAY_SIZE(pstore_type_names) != PSTORE_TYPE_MAX);
111 
112 	if (WARN_ON_ONCE(type >= PSTORE_TYPE_MAX))
113 		return "unknown";
114 
115 	return pstore_type_names[type];
116 }
117 EXPORT_SYMBOL_GPL(pstore_type_to_name);
118 
pstore_name_to_type(const char * name)119 enum pstore_type_id pstore_name_to_type(const char *name)
120 {
121 	int i;
122 
123 	for (i = 0; i < PSTORE_TYPE_MAX; i++) {
124 		if (!strcmp(pstore_type_names[i], name))
125 			return i;
126 	}
127 
128 	return PSTORE_TYPE_MAX;
129 }
130 EXPORT_SYMBOL_GPL(pstore_name_to_type);
131 
get_reason_str(enum kmsg_dump_reason reason)132 static const char *get_reason_str(enum kmsg_dump_reason reason)
133 {
134 	switch (reason) {
135 	case KMSG_DUMP_PANIC:
136 		return "Panic";
137 	case KMSG_DUMP_OOPS:
138 		return "Oops";
139 	case KMSG_DUMP_EMERG:
140 		return "Emergency";
141 	case KMSG_DUMP_RESTART:
142 		return "Restart";
143 	case KMSG_DUMP_HALT:
144 		return "Halt";
145 	case KMSG_DUMP_POWEROFF:
146 		return "Poweroff";
147 	default:
148 		return "Unknown";
149 	}
150 }
151 
152 /*
153  * Should pstore_dump() wait for a concurrent pstore_dump()? If
154  * not, the current pstore_dump() will report a failure to dump
155  * and return.
156  */
pstore_cannot_wait(enum kmsg_dump_reason reason)157 static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
158 {
159 	/* In NMI path, pstore shouldn't block regardless of reason. */
160 	if (in_nmi())
161 		return true;
162 
163 	switch (reason) {
164 	/* In panic case, other cpus are stopped by smp_send_stop(). */
165 	case KMSG_DUMP_PANIC:
166 	/* Emergency restart shouldn't be blocked. */
167 	case KMSG_DUMP_EMERG:
168 		return true;
169 	default:
170 		return false;
171 	}
172 }
173 
174 #if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
zbufsize_deflate(size_t size)175 static int zbufsize_deflate(size_t size)
176 {
177 	size_t cmpr;
178 
179 	switch (size) {
180 	/* buffer range for efivars */
181 	case 1000 ... 2000:
182 		cmpr = 56;
183 		break;
184 	case 2001 ... 3000:
185 		cmpr = 54;
186 		break;
187 	case 3001 ... 3999:
188 		cmpr = 52;
189 		break;
190 	/* buffer range for nvram, erst */
191 	case 4000 ... 10000:
192 		cmpr = 45;
193 		break;
194 	default:
195 		cmpr = 60;
196 		break;
197 	}
198 
199 	return (size * 100) / cmpr;
200 }
201 #endif
202 
203 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
zbufsize_lzo(size_t size)204 static int zbufsize_lzo(size_t size)
205 {
206 	return lzo1x_worst_compress(size);
207 }
208 #endif
209 
210 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
zbufsize_lz4(size_t size)211 static int zbufsize_lz4(size_t size)
212 {
213 	return LZ4_compressBound(size);
214 }
215 #endif
216 
217 #if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
zbufsize_842(size_t size)218 static int zbufsize_842(size_t size)
219 {
220 	return size;
221 }
222 #endif
223 
224 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
zbufsize_zstd(size_t size)225 static int zbufsize_zstd(size_t size)
226 {
227 	return ZSTD_compressBound(size);
228 }
229 #endif
230 
231 static const struct pstore_zbackend *zbackend __ro_after_init;
232 
233 static const struct pstore_zbackend zbackends[] = {
234 #if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
235 	{
236 		.zbufsize	= zbufsize_deflate,
237 		.name		= "deflate",
238 	},
239 #endif
240 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
241 	{
242 		.zbufsize	= zbufsize_lzo,
243 		.name		= "lzo",
244 	},
245 #endif
246 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS)
247 	{
248 		.zbufsize	= zbufsize_lz4,
249 		.name		= "lz4",
250 	},
251 #endif
252 #if IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
253 	{
254 		.zbufsize	= zbufsize_lz4,
255 		.name		= "lz4hc",
256 	},
257 #endif
258 #if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
259 	{
260 		.zbufsize	= zbufsize_842,
261 		.name		= "842",
262 	},
263 #endif
264 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
265 	{
266 		.zbufsize	= zbufsize_zstd,
267 		.name		= "zstd",
268 	},
269 #endif
270 	{ }
271 };
272 
pstore_compress(const void * in,void * out,unsigned int inlen,unsigned int outlen)273 static int pstore_compress(const void *in, void *out,
274 			   unsigned int inlen, unsigned int outlen)
275 {
276 	int ret;
277 
278 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS))
279 		return -EINVAL;
280 
281 	ret = crypto_comp_compress(tfm, in, inlen, out, &outlen);
282 	if (ret) {
283 		pr_err("crypto_comp_compress failed, ret = %d!\n", ret);
284 		return ret;
285 	}
286 
287 	return outlen;
288 }
289 
allocate_buf_for_compression(void)290 static void allocate_buf_for_compression(void)
291 {
292 	struct crypto_comp *ctx;
293 	int size;
294 	char *buf;
295 
296 	/* Skip if not built-in or compression backend not selected yet. */
297 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
298 		return;
299 
300 	/* Skip if no pstore backend yet or compression init already done. */
301 	if (!psinfo || tfm)
302 		return;
303 
304 	if (!crypto_has_comp(zbackend->name, 0, 0)) {
305 		pr_err("Unknown compression: %s\n", zbackend->name);
306 		return;
307 	}
308 
309 	size = zbackend->zbufsize(psinfo->bufsize);
310 	if (size <= 0) {
311 		pr_err("Invalid compression size for %s: %d\n",
312 		       zbackend->name, size);
313 		return;
314 	}
315 
316 	buf = kmalloc(size, GFP_KERNEL);
317 	if (!buf) {
318 		pr_err("Failed %d byte compression buffer allocation for: %s\n",
319 		       size, zbackend->name);
320 		return;
321 	}
322 
323 	ctx = crypto_alloc_comp(zbackend->name, 0, 0);
324 	if (IS_ERR_OR_NULL(ctx)) {
325 		kfree(buf);
326 		pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
327 		       PTR_ERR(ctx));
328 		return;
329 	}
330 
331 	/* A non-NULL big_oops_buf indicates compression is available. */
332 	tfm = ctx;
333 	big_oops_buf_sz = size;
334 	big_oops_buf = buf;
335 
336 	pr_info("Using crash dump compression: %s\n", zbackend->name);
337 }
338 
free_buf_for_compression(void)339 static void free_buf_for_compression(void)
340 {
341 	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm) {
342 		crypto_free_comp(tfm);
343 		tfm = NULL;
344 	}
345 	kfree(big_oops_buf);
346 	big_oops_buf = NULL;
347 	big_oops_buf_sz = 0;
348 }
349 
350 /*
351  * Called when compression fails, since the printk buffer
352  * would be fetched for compression calling it again when
353  * compression fails would have moved the iterator of
354  * printk buffer which results in fetching old contents.
355  * Copy the recent messages from big_oops_buf to psinfo->buf
356  */
copy_kmsg_to_buffer(int hsize,size_t len)357 static size_t copy_kmsg_to_buffer(int hsize, size_t len)
358 {
359 	size_t total_len;
360 	size_t diff;
361 
362 	total_len = hsize + len;
363 
364 	if (total_len > psinfo->bufsize) {
365 		diff = total_len - psinfo->bufsize + hsize;
366 		memcpy(psinfo->buf, big_oops_buf, hsize);
367 		memcpy(psinfo->buf + hsize, big_oops_buf + diff,
368 					psinfo->bufsize - hsize);
369 		total_len = psinfo->bufsize;
370 	} else
371 		memcpy(psinfo->buf, big_oops_buf, total_len);
372 
373 	return total_len;
374 }
375 
pstore_record_init(struct pstore_record * record,struct pstore_info * psinfo)376 void pstore_record_init(struct pstore_record *record,
377 			struct pstore_info *psinfo)
378 {
379 	memset(record, 0, sizeof(*record));
380 
381 	record->psi = psinfo;
382 
383 	/* Report zeroed timestamp if called before timekeeping has resumed. */
384 	record->time = ns_to_timespec64(ktime_get_real_fast_ns());
385 }
386 
387 /*
388  * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from the
389  * end of the buffer.
390  */
pstore_dump(struct kmsg_dumper * dumper,enum kmsg_dump_reason reason)391 static void pstore_dump(struct kmsg_dumper *dumper,
392 			enum kmsg_dump_reason reason)
393 {
394 	unsigned long	total = 0;
395 	const char	*why;
396 	unsigned int	part = 1;
397 	int		ret;
398 
399 	why = get_reason_str(reason);
400 
401 	if (down_trylock(&psinfo->buf_lock)) {
402 		/* Failed to acquire lock: give up if we cannot wait. */
403 		if (pstore_cannot_wait(reason)) {
404 			pr_err("dump skipped in %s path: may corrupt error record\n",
405 				in_nmi() ? "NMI" : why);
406 			return;
407 		}
408 		if (down_interruptible(&psinfo->buf_lock)) {
409 			pr_err("could not grab semaphore?!\n");
410 			return;
411 		}
412 	}
413 
414 	oopscount++;
415 	while (total < kmsg_bytes) {
416 		char *dst;
417 		size_t dst_size;
418 		int header_size;
419 		int zipped_len = -1;
420 		size_t dump_size;
421 		struct pstore_record record;
422 
423 		pstore_record_init(&record, psinfo);
424 		record.type = PSTORE_TYPE_DMESG;
425 		record.count = oopscount;
426 		record.reason = reason;
427 		record.part = part;
428 		record.buf = psinfo->buf;
429 
430 		if (big_oops_buf) {
431 			dst = big_oops_buf;
432 			dst_size = big_oops_buf_sz;
433 		} else {
434 			dst = psinfo->buf;
435 			dst_size = psinfo->bufsize;
436 		}
437 
438 		/* Write dump header. */
439 		header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
440 				 oopscount, part);
441 		dst_size -= header_size;
442 
443 		/* Write dump contents. */
444 		if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
445 					  dst_size, &dump_size))
446 			break;
447 
448 		if (big_oops_buf) {
449 			zipped_len = pstore_compress(dst, psinfo->buf,
450 						header_size + dump_size,
451 						psinfo->bufsize);
452 
453 			if (zipped_len > 0) {
454 				record.compressed = true;
455 				record.size = zipped_len;
456 			} else {
457 				record.size = copy_kmsg_to_buffer(header_size,
458 								  dump_size);
459 			}
460 		} else {
461 			record.size = header_size + dump_size;
462 		}
463 
464 		ret = psinfo->write(&record);
465 		if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
466 			pstore_new_entry = 1;
467 
468 		total += record.size;
469 		part++;
470 	}
471 
472 	up(&psinfo->buf_lock);
473 }
474 
475 static struct kmsg_dumper pstore_dumper = {
476 	.dump = pstore_dump,
477 };
478 
479 /*
480  * Register with kmsg_dump to save last part of console log on panic.
481  */
pstore_register_kmsg(void)482 static void pstore_register_kmsg(void)
483 {
484 	kmsg_dump_register(&pstore_dumper);
485 }
486 
pstore_unregister_kmsg(void)487 static void pstore_unregister_kmsg(void)
488 {
489 	kmsg_dump_unregister(&pstore_dumper);
490 }
491 
492 #ifdef CONFIG_PSTORE_CONSOLE
pstore_console_write(struct console * con,const char * s,unsigned c)493 static void pstore_console_write(struct console *con, const char *s, unsigned c)
494 {
495 	struct pstore_record record;
496 
497 	if (!c)
498 		return;
499 
500 	pstore_record_init(&record, psinfo);
501 	record.type = PSTORE_TYPE_CONSOLE;
502 
503 	record.buf = (char *)s;
504 	record.size = c;
505 	psinfo->write(&record);
506 }
507 
508 static struct console pstore_console = {
509 	.name	= "pstore",
510 	.write	= pstore_console_write,
511 	.flags	= CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
512 	.index	= -1,
513 };
514 
pstore_register_console(void)515 static void pstore_register_console(void)
516 {
517 	register_console(&pstore_console);
518 }
519 
pstore_unregister_console(void)520 static void pstore_unregister_console(void)
521 {
522 	unregister_console(&pstore_console);
523 }
524 #else
pstore_register_console(void)525 static void pstore_register_console(void) {}
pstore_unregister_console(void)526 static void pstore_unregister_console(void) {}
527 #endif
528 
pstore_write_user_compat(struct pstore_record * record,const char __user * buf)529 static int pstore_write_user_compat(struct pstore_record *record,
530 				    const char __user *buf)
531 {
532 	int ret = 0;
533 
534 	if (record->buf)
535 		return -EINVAL;
536 
537 	record->buf = memdup_user(buf, record->size);
538 	if (IS_ERR(record->buf)) {
539 		ret = PTR_ERR(record->buf);
540 		goto out;
541 	}
542 
543 	ret = record->psi->write(record);
544 
545 	kfree(record->buf);
546 out:
547 	record->buf = NULL;
548 
549 	return unlikely(ret < 0) ? ret : record->size;
550 }
551 
552 /*
553  * platform specific persistent storage driver registers with
554  * us here. If pstore is already mounted, call the platform
555  * read function right away to populate the file system. If not
556  * then the pstore mount code will call us later to fill out
557  * the file system.
558  */
pstore_register(struct pstore_info * psi)559 int pstore_register(struct pstore_info *psi)
560 {
561 	struct module *owner = psi->owner;
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 	spin_lock(&pstore_lock);
583 	if (psinfo) {
584 		pr_warn("backend '%s' already loaded: ignoring '%s'\n",
585 			psinfo->name, psi->name);
586 		spin_unlock(&pstore_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 	spin_unlock(&pstore_lock);
596 
597 	if (owner && !try_module_get(owner)) {
598 		psinfo = NULL;
599 		return -EINVAL;
600 	}
601 
602 	if (psi->flags & PSTORE_FLAGS_DMESG)
603 		allocate_buf_for_compression();
604 
605 	if (pstore_is_mounted())
606 		pstore_get_records(0);
607 
608 	if (psi->flags & PSTORE_FLAGS_DMESG)
609 		pstore_register_kmsg();
610 	if (psi->flags & PSTORE_FLAGS_CONSOLE)
611 		pstore_register_console();
612 	if (psi->flags & PSTORE_FLAGS_FTRACE)
613 		pstore_register_ftrace();
614 	if (psi->flags & PSTORE_FLAGS_PMSG)
615 		pstore_register_pmsg();
616 
617 	/* Start watching for new records, if desired. */
618 	if (pstore_update_ms >= 0) {
619 		pstore_timer.expires = jiffies +
620 			msecs_to_jiffies(pstore_update_ms);
621 		add_timer(&pstore_timer);
622 	}
623 
624 	/*
625 	 * Update the module parameter backend, so it is visible
626 	 * through /sys/module/pstore/parameters/backend
627 	 */
628 	backend = psi->name;
629 
630 	pr_info("Registered %s as persistent store backend\n", psi->name);
631 
632 	module_put(owner);
633 
634 	return 0;
635 }
636 EXPORT_SYMBOL_GPL(pstore_register);
637 
pstore_unregister(struct pstore_info * psi)638 void pstore_unregister(struct pstore_info *psi)
639 {
640 	/* Stop timer and make sure all work has finished. */
641 	pstore_update_ms = -1;
642 	del_timer_sync(&pstore_timer);
643 	flush_work(&pstore_work);
644 
645 	if (psi->flags & PSTORE_FLAGS_PMSG)
646 		pstore_unregister_pmsg();
647 	if (psi->flags & PSTORE_FLAGS_FTRACE)
648 		pstore_unregister_ftrace();
649 	if (psi->flags & PSTORE_FLAGS_CONSOLE)
650 		pstore_unregister_console();
651 	if (psi->flags & PSTORE_FLAGS_DMESG)
652 		pstore_unregister_kmsg();
653 
654 	free_buf_for_compression();
655 
656 	psinfo = NULL;
657 	backend = NULL;
658 }
659 EXPORT_SYMBOL_GPL(pstore_unregister);
660 
decompress_record(struct pstore_record * record)661 static void decompress_record(struct pstore_record *record)
662 {
663 	int ret;
664 	int unzipped_len;
665 	char *unzipped, *workspace;
666 
667 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !record->compressed)
668 		return;
669 
670 	/* Only PSTORE_TYPE_DMESG support compression. */
671 	if (record->type != PSTORE_TYPE_DMESG) {
672 		pr_warn("ignored compressed record type %d\n", record->type);
673 		return;
674 	}
675 
676 	/* Missing compression buffer means compression was not initialized. */
677 	if (!big_oops_buf) {
678 		pr_warn("no decompression method initialized!\n");
679 		return;
680 	}
681 
682 	/* Allocate enough space to hold max decompression and ECC. */
683 	unzipped_len = big_oops_buf_sz;
684 	workspace = kmalloc(unzipped_len + record->ecc_notice_size,
685 			    GFP_KERNEL);
686 	if (!workspace)
687 		return;
688 
689 	/* After decompression "unzipped_len" is almost certainly smaller. */
690 	ret = crypto_comp_decompress(tfm, record->buf, record->size,
691 					  workspace, &unzipped_len);
692 	if (ret) {
693 		pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
694 		kfree(workspace);
695 		return;
696 	}
697 
698 	/* Append ECC notice to decompressed buffer. */
699 	memcpy(workspace + unzipped_len, record->buf + record->size,
700 	       record->ecc_notice_size);
701 
702 	/* Copy decompressed contents into an minimum-sized allocation. */
703 	unzipped = kmemdup(workspace, unzipped_len + record->ecc_notice_size,
704 			   GFP_KERNEL);
705 	kfree(workspace);
706 	if (!unzipped)
707 		return;
708 
709 	/* Swap out compressed contents with decompressed contents. */
710 	kfree(record->buf);
711 	record->buf = unzipped;
712 	record->size = unzipped_len;
713 	record->compressed = false;
714 }
715 
716 /*
717  * Read all the records from one persistent store backend. Create
718  * files in our filesystem.  Don't warn about -EEXIST errors
719  * when we are re-scanning the backing store looking to add new
720  * error records.
721  */
pstore_get_backend_records(struct pstore_info * psi,struct dentry * root,int quiet)722 void pstore_get_backend_records(struct pstore_info *psi,
723 				struct dentry *root, int quiet)
724 {
725 	int failed = 0;
726 	unsigned int stop_loop = 65536;
727 
728 	if (!psi || !root)
729 		return;
730 
731 	mutex_lock(&psi->read_mutex);
732 	if (psi->open && psi->open(psi))
733 		goto out;
734 
735 	/*
736 	 * Backend callback read() allocates record.buf. decompress_record()
737 	 * may reallocate record.buf. On success, pstore_mkfile() will keep
738 	 * the record.buf, so free it only on failure.
739 	 */
740 	for (; stop_loop; stop_loop--) {
741 		struct pstore_record *record;
742 		int rc;
743 
744 		record = kzalloc(sizeof(*record), GFP_KERNEL);
745 		if (!record) {
746 			pr_err("out of memory creating record\n");
747 			break;
748 		}
749 		pstore_record_init(record, psi);
750 
751 		record->size = psi->read(record);
752 
753 		/* No more records left in backend? */
754 		if (record->size <= 0) {
755 			kfree(record);
756 			break;
757 		}
758 
759 		decompress_record(record);
760 		rc = pstore_mkfile(root, record);
761 		if (rc) {
762 			/* pstore_mkfile() did not take record, so free it. */
763 			kfree(record->buf);
764 			kfree(record);
765 			if (rc != -EEXIST || !quiet)
766 				failed++;
767 		}
768 	}
769 	if (psi->close)
770 		psi->close(psi);
771 out:
772 	mutex_unlock(&psi->read_mutex);
773 
774 	if (failed)
775 		pr_warn("failed to create %d record(s) from '%s'\n",
776 			failed, psi->name);
777 	if (!stop_loop)
778 		pr_err("looping? Too many records seen from '%s'\n",
779 			psi->name);
780 }
781 
pstore_dowork(struct work_struct * work)782 static void pstore_dowork(struct work_struct *work)
783 {
784 	pstore_get_records(1);
785 }
786 
pstore_timefunc(struct timer_list * unused)787 static void pstore_timefunc(struct timer_list *unused)
788 {
789 	if (pstore_new_entry) {
790 		pstore_new_entry = 0;
791 		schedule_work(&pstore_work);
792 	}
793 
794 	if (pstore_update_ms >= 0)
795 		mod_timer(&pstore_timer,
796 			  jiffies + msecs_to_jiffies(pstore_update_ms));
797 }
798 
pstore_choose_compression(void)799 void __init pstore_choose_compression(void)
800 {
801 	const struct pstore_zbackend *step;
802 
803 	if (!compress)
804 		return;
805 
806 	for (step = zbackends; step->name; step++) {
807 		if (!strcmp(compress, step->name)) {
808 			zbackend = step;
809 			return;
810 		}
811 	}
812 }
813 
pstore_init(void)814 static int __init pstore_init(void)
815 {
816 	int ret;
817 
818 	pstore_choose_compression();
819 
820 	/*
821 	 * Check if any pstore backends registered earlier but did not
822 	 * initialize compression because crypto was not ready. If so,
823 	 * initialize compression now.
824 	 */
825 	allocate_buf_for_compression();
826 
827 	ret = pstore_init_fs();
828 	if (ret)
829 		free_buf_for_compression();
830 
831 	return ret;
832 }
833 late_initcall(pstore_init);
834 
pstore_exit(void)835 static void __exit pstore_exit(void)
836 {
837 	pstore_exit_fs();
838 }
839 module_exit(pstore_exit)
840 
841 module_param(compress, charp, 0444);
842 MODULE_PARM_DESC(compress, "Pstore compression to use");
843 
844 module_param(backend, charp, 0444);
845 MODULE_PARM_DESC(backend, "Pstore backend to use");
846 
847 MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
848 MODULE_LICENSE("GPL");
849