1 files changed, 258 insertions, 343 deletions

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 2d1066ed3c28..f8b9c9c73997 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -1,21 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Persistent Storage - platform driver interface parts.
  *
  * Copyright (C) 2007-2008 Google, Inc.
  * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License version 2 as
- *  published by the Free Software Foundation.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with this program; if not, write to the Free Software
- *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
 #define pr_fmt(fmt) "pstore: " fmt
@@ -26,24 +14,17 @@
 #include <linux/init.h>
 #include <linux/kmsg_dump.h>
 #include <linux/console.h>
+#include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/pstore.h>
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
-#include <linux/lzo.h>
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
-#include <linux/lz4.h>
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
-#include <linux/zstd.h>
-#endif
-#include <linux/crypto.h>
 #include <linux/string.h>
 #include <linux/timer.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/jiffies.h>
+#include <linux/vmalloc.h>
 #include <linux/workqueue.h>
+#include <linux/zlib.h>
 
 #include "internal.h"
 
@@ -56,7 +37,7 @@ static int pstore_update_ms = -1;
 module_param_named(update_ms, pstore_update_ms, int, 0600);
 MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
 		 "(default is -1, which means runtime updates are disabled; "
-		 "enabling this option is not safe, it may lead to further "
+		 "enabling this option may not be safe; it may lead to further "
 		 "corruption on Oopses)");
 
 /* Names should be in the same order as the enum pstore_type_id */
@@ -81,37 +62,54 @@ static void pstore_dowork(struct work_struct *);
 static DECLARE_WORK(pstore_work, pstore_dowork);
 
 /*
- * pstore_lock just protects "psinfo" during
- * calls to pstore_register()
+ * psinfo_lock protects "psinfo" during calls to
+ * pstore_register(), pstore_unregister(), and
+ * the filesystem mount/unmount routines.
  */
-static DEFINE_SPINLOCK(pstore_lock);
+static DEFINE_MUTEX(psinfo_lock);
 struct pstore_info *psinfo;
 
 static char *backend;
-static char *compress =
-#ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
-		CONFIG_PSTORE_COMPRESS_DEFAULT;
-#else
-		NULL;
-#endif
+module_param(backend, charp, 0444);
+MODULE_PARM_DESC(backend, "specific backend to use");
 
-/* Compression parameters */
-static struct crypto_comp *tfm;
+/*
+ * pstore no longer implements compression via the crypto API, and only
+ * supports zlib deflate compression implemented using the zlib library
+ * interface. This removes additional complexity which is hard to justify for a
+ * diagnostic facility that has to operate in conditions where the system may
+ * have become unstable. Zlib deflate is comparatively small in terms of code
+ * size, and compresses ASCII text comparatively well. In terms of compression
+ * speed, deflate is not the best performer but for recording the log output on
+ * a kernel panic, this is not considered critical.
+ *
+ * The only remaining arguments supported by the compress= module parameter are
+ * 'deflate' and 'none'. To retain compatibility with existing installations,
+ * all other values are logged and replaced with 'deflate'.
+ */
+static char *compress = "deflate";
+module_param(compress, charp, 0444);
+MODULE_PARM_DESC(compress, "compression to use");
 
-struct pstore_zbackend {
-	int (*zbufsize)(size_t size);
-	const char *name;
-};
+/* How much of the kernel log to snapshot */
+unsigned int kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES;
+module_param(kmsg_bytes, uint, 0444);
+MODULE_PARM_DESC(kmsg_bytes, "amount of kernel log to snapshot (in bytes)");
 
-static char *big_oops_buf;
-static size_t big_oops_buf_sz;
+static void *compress_workspace;
 
-/* How much of the console log to snapshot */
-unsigned long kmsg_bytes = PSTORE_DEFAULT_KMSG_BYTES;
+/*
+ * Compression is only used for dmesg output, which consists of low-entropy
+ * ASCII text, and so we can assume worst-case 60%.
+ */
+#define DMESG_COMP_PERCENT	60
+
+static char *big_oops_buf;
+static size_t max_compressed_size;
 
-void pstore_set_kmsg_bytes(int bytes)
+void pstore_set_kmsg_bytes(unsigned int bytes)
 {
-	kmsg_bytes = bytes;
+	WRITE_ONCE(kmsg_bytes, bytes);
 }
 
 /* Tag each group of saved records with a sequence number */
@@ -141,41 +139,30 @@ enum pstore_type_id pstore_name_to_type(const char *name)
 }
 EXPORT_SYMBOL_GPL(pstore_name_to_type);
 
-static const char *get_reason_str(enum kmsg_dump_reason reason)
+static void pstore_timer_kick(void)
 {
-	switch (reason) {
-	case KMSG_DUMP_PANIC:
-		return "Panic";
-	case KMSG_DUMP_OOPS:
-		return "Oops";
-	case KMSG_DUMP_EMERG:
-		return "Emergency";
-	case KMSG_DUMP_RESTART:
-		return "Restart";
-	case KMSG_DUMP_HALT:
-		return "Halt";
-	case KMSG_DUMP_POWEROFF:
-		return "Poweroff";
-	default:
-		return "Unknown";
-	}
+	if (pstore_update_ms < 0)
+		return;
+
+	mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
 }
 
-/*
- * Should pstore_dump() wait for a concurrent pstore_dump()? If
- * not, the current pstore_dump() will report a failure to dump
- * and return.
- */
-static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
+static bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
 {
-	/* In NMI path, pstore shouldn't block regardless of reason. */
+	/*
+	 * In case of NMI path, pstore shouldn't be blocked
+	 * regardless of reason.
+	 */
 	if (in_nmi())
 		return true;
 
 	switch (reason) {
 	/* In panic case, other cpus are stopped by smp_send_stop(). */
 	case KMSG_DUMP_PANIC:
-	/* Emergency restart shouldn't be blocked. */
+	/*
+	 * Emergency restart shouldn't be blocked by spinning on
+	 * pstore_info::buf_lock.
+	 */
 	case KMSG_DUMP_EMERG:
 		return true;
 	default:
@@ -183,201 +170,93 @@ static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
 	}
 }
 
-#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
-static int zbufsize_deflate(size_t size)
-{
-	size_t cmpr;
-
-	switch (size) {
-	/* buffer range for efivars */
-	case 1000 ... 2000:
-		cmpr = 56;
-		break;
-	case 2001 ... 3000:
-		cmpr = 54;
-		break;
-	case 3001 ... 3999:
-		cmpr = 52;
-		break;
-	/* buffer range for nvram, erst */
-	case 4000 ... 10000:
-		cmpr = 45;
-		break;
-	default:
-		cmpr = 60;
-		break;
-	}
-
-	return (size * 100) / cmpr;
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
-static int zbufsize_lzo(size_t size)
-{
-	return lzo1x_worst_compress(size);
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
-static int zbufsize_lz4(size_t size)
-{
-	return LZ4_compressBound(size);
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
-static int zbufsize_842(size_t size)
-{
-	return size;
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
-static int zbufsize_zstd(size_t size)
-{
-	return ZSTD_compressBound(size);
-}
-#endif
-
-static const struct pstore_zbackend *zbackend __ro_after_init;
-
-static const struct pstore_zbackend zbackends[] = {
-#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
-	{
-		.zbufsize	= zbufsize_deflate,
-		.name		= "deflate",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
-	{
-		.zbufsize	= zbufsize_lzo,
-		.name		= "lzo",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS)
-	{
-		.zbufsize	= zbufsize_lz4,
-		.name		= "lz4",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
-	{
-		.zbufsize	= zbufsize_lz4,
-		.name		= "lz4hc",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
-	{
-		.zbufsize	= zbufsize_842,
-		.name		= "842",
-	},
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
-	{
-		.zbufsize	= zbufsize_zstd,
-		.name		= "zstd",
-	},
-#endif
-	{ }
-};
-
 static int pstore_compress(const void *in, void *out,
 			   unsigned int inlen, unsigned int outlen)
 {
+	struct z_stream_s zstream = {
+		.next_in	= in,
+		.avail_in	= inlen,
+		.next_out	= out,
+		.avail_out	= outlen,
+		.workspace	= compress_workspace,
+	};
 	int ret;
 
-	ret = crypto_comp_compress(tfm, in, inlen, out, &outlen);
-	if (ret) {
-		pr_err("crypto_comp_compress failed, ret = %d!\n", ret);
-		return ret;
-	}
+	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS))
+		return -EINVAL;
 
-	return outlen;
+	ret = zlib_deflateInit2(&zstream, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
+				-MAX_WBITS, DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY);
+	if (ret != Z_OK)
+		return -EINVAL;
+
+	ret = zlib_deflate(&zstream, Z_FINISH);
+	if (ret != Z_STREAM_END)
+		return -EINVAL;
+
+	ret = zlib_deflateEnd(&zstream);
+	if (ret != Z_OK)
+		pr_warn_once("zlib_deflateEnd() failed: %d\n", ret);
+
+	return zstream.total_out;
 }
 
 static void allocate_buf_for_compression(void)
 {
-	struct crypto_comp *ctx;
-	int size;
+	size_t compressed_size;
 	char *buf;
 
-	/* Skip if not built-in or compression backend not selected yet. */
-	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
-		return;
-
-	/* Skip if no pstore backend yet or compression init already done. */
-	if (!psinfo || tfm)
-		return;
-
-	if (!crypto_has_comp(zbackend->name, 0, 0)) {
-		pr_err("Unknown compression: %s\n", zbackend->name);
+	/* Skip if not built-in or compression disabled. */
+	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !compress ||
+	    !strcmp(compress, "none")) {
+		compress = NULL;
 		return;
 	}
 
-	size = zbackend->zbufsize(psinfo->bufsize);
-	if (size <= 0) {
-		pr_err("Invalid compression size for %s: %d\n",
-		       zbackend->name, size);
-		return;
+	if (strcmp(compress, "deflate")) {
+		pr_err("Unsupported compression '%s', falling back to deflate\n",
+		       compress);
+		compress = "deflate";
 	}
 
-	buf = kmalloc(size, GFP_KERNEL);
+	/*
+	 * The compression buffer only needs to be as large as the maximum
+	 * uncompressed record size, since any record that would be expanded by
+	 * compression is just stored uncompressed.
+	 */
+	compressed_size = (psinfo->bufsize * 100) / DMESG_COMP_PERCENT;
+	buf = kvzalloc(compressed_size, GFP_KERNEL);
 	if (!buf) {
-		pr_err("Failed %d byte compression buffer allocation for: %s\n",
-		       size, zbackend->name);
+		pr_err("Failed %zu byte compression buffer allocation for: %s\n",
+		       psinfo->bufsize, compress);
 		return;
 	}
 
-	ctx = crypto_alloc_comp(zbackend->name, 0, 0);
-	if (IS_ERR_OR_NULL(ctx)) {
-		kfree(buf);
-		pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
-		       PTR_ERR(ctx));
+	compress_workspace =
+		vmalloc(zlib_deflate_workspacesize(MAX_WBITS, DEF_MEM_LEVEL));
+	if (!compress_workspace) {
+		pr_err("Failed to allocate zlib deflate workspace\n");
+		kvfree(buf);
 		return;
 	}
 
 	/* A non-NULL big_oops_buf indicates compression is available. */
-	tfm = ctx;
-	big_oops_buf_sz = size;
 	big_oops_buf = buf;
+	max_compressed_size = compressed_size;
 
-	pr_info("Using crash dump compression: %s\n", zbackend->name);
+	pr_info("Using crash dump compression: %s\n", compress);
 }
 
 static void free_buf_for_compression(void)
 {
-	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm)
-		crypto_free_comp(tfm);
-	kfree(big_oops_buf);
-	big_oops_buf = NULL;
-	big_oops_buf_sz = 0;
-}
-
-/*
- * Called when compression fails, since the printk buffer
- * would be fetched for compression calling it again when
- * compression fails would have moved the iterator of
- * printk buffer which results in fetching old contents.
- * Copy the recent messages from big_oops_buf to psinfo->buf
- */
-static size_t copy_kmsg_to_buffer(int hsize, size_t len)
-{
-	size_t total_len;
-	size_t diff;
-
-	total_len = hsize + len;
-
-	if (total_len > psinfo->bufsize) {
-		diff = total_len - psinfo->bufsize + hsize;
-		memcpy(psinfo->buf, big_oops_buf, hsize);
-		memcpy(psinfo->buf + hsize, big_oops_buf + diff,
-					psinfo->bufsize - hsize);
-		total_len = psinfo->bufsize;
-	} else
-		memcpy(psinfo->buf, big_oops_buf, total_len);
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress_workspace) {
+		vfree(compress_workspace);
+		compress_workspace = NULL;
+	}
 
-	return total_len;
+	kvfree(big_oops_buf);
+	big_oops_buf = NULL;
+	max_compressed_size = 0;
 }
 
 void pstore_record_init(struct pstore_record *record,
@@ -396,30 +275,33 @@ void pstore_record_init(struct pstore_record *record,
  * end of the buffer.
  */
 static void pstore_dump(struct kmsg_dumper *dumper,
-			enum kmsg_dump_reason reason)
+			struct kmsg_dump_detail *detail)
 {
+	struct kmsg_dump_iter iter;
+	unsigned int	remaining = READ_ONCE(kmsg_bytes);
 	unsigned long	total = 0;
 	const char	*why;
 	unsigned int	part = 1;
+	unsigned long	flags = 0;
+	int		saved_ret = 0;
 	int		ret;
 
-	why = get_reason_str(reason);
+	why = kmsg_dump_reason_str(detail->reason);
 
-	if (down_trylock(&psinfo->buf_lock)) {
-		/* Failed to acquire lock: give up if we cannot wait. */
-		if (pstore_cannot_wait(reason)) {
-			pr_err("dump skipped in %s path: may corrupt error record\n",
-				in_nmi() ? "NMI" : why);
-			return;
-		}
-		if (down_interruptible(&psinfo->buf_lock)) {
-			pr_err("could not grab semaphore?!\n");
+	if (pstore_cannot_block_path(detail->reason)) {
+		if (!raw_spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
+			pr_err("dump skipped in %s path because of concurrent dump\n",
+					in_nmi() ? "NMI" : why);
 			return;
 		}
+	} else {
+		raw_spin_lock_irqsave(&psinfo->buf_lock, flags);
 	}
 
+	kmsg_dump_rewind(&iter);
+
 	oopscount++;
-	while (total < kmsg_bytes) {
+	while (total < remaining) {
 		char *dst;
 		size_t dst_size;
 		int header_size;
@@ -430,17 +312,12 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		pstore_record_init(&record, psinfo);
 		record.type = PSTORE_TYPE_DMESG;
 		record.count = oopscount;
-		record.reason = reason;
+		record.reason = detail->reason;
 		record.part = part;
 		record.buf = psinfo->buf;
 
-		if (big_oops_buf) {
-			dst = big_oops_buf;
-			dst_size = big_oops_buf_sz;
-		} else {
-			dst = psinfo->buf;
-			dst_size = psinfo->bufsize;
-		}
+		dst = big_oops_buf ?: psinfo->buf;
+		dst_size = max_compressed_size ?: psinfo->bufsize;
 
 		/* Write dump header. */
 		header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
@@ -448,7 +325,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		dst_size -= header_size;
 
 		/* Write dump contents. */
-		if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
+		if (!kmsg_dump_get_buffer(&iter, true, dst + header_size,
 					  dst_size, &dump_size))
 			break;
 
@@ -461,22 +338,39 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 				record.compressed = true;
 				record.size = zipped_len;
 			} else {
-				record.size = copy_kmsg_to_buffer(header_size,
-								  dump_size);
+				/*
+				 * Compression failed, so the buffer is most
+				 * likely filled with binary data that does not
+				 * compress as well as ASCII text. Copy as much
+				 * of the uncompressed data as possible into
+				 * the pstore record, and discard the rest.
+				 */
+				record.size = psinfo->bufsize;
+				memcpy(psinfo->buf, dst, psinfo->bufsize);
 			}
 		} else {
 			record.size = header_size + dump_size;
 		}
 
 		ret = psinfo->write(&record);
-		if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
+		if (ret == 0 && detail->reason == KMSG_DUMP_OOPS) {
 			pstore_new_entry = 1;
+			pstore_timer_kick();
+		} else {
+			/* Preserve only the first non-zero returned value. */
+			if (!saved_ret)
+				saved_ret = ret;
+		}
 
 		total += record.size;
 		part++;
 	}
+	raw_spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 
-	up(&psinfo->buf_lock);
+	if (saved_ret) {
+		pr_err_once("backend (%s) writing error (%d)\n", psinfo->name,
+			    saved_ret);
+	}
 }
 
 static struct kmsg_dumper pstore_dumper = {
@@ -501,6 +395,9 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 {
 	struct pstore_record record;
 
+	if (!c)
+		return;
+
 	pstore_record_init(&record, psinfo);
 	record.type = PSTORE_TYPE_CONSOLE;
 
@@ -510,14 +407,20 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 }
 
 static struct console pstore_console = {
-	.name	= "pstore",
 	.write	= pstore_console_write,
-	.flags	= CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
 	.index	= -1,
 };
 
 static void pstore_register_console(void)
 {
+	/* Show which backend is going to get console writes. */
+	strscpy(pstore_console.name, psinfo->name,
+		sizeof(pstore_console.name));
+	/*
+	 * Always initialize flags here since prior unregister_console()
+	 * calls may have changed settings (specifically CON_ENABLED).
+	 */
+	pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME;
 	register_console(&pstore_console);
 }
 
@@ -538,7 +441,7 @@ static int pstore_write_user_compat(struct pstore_record *record,
 	if (record->buf)
 		return -EINVAL;
 
-	record->buf = memdup_user(buf, record->size);
+	record->buf = vmemdup_user(buf, record->size);
 	if (IS_ERR(record->buf)) {
 		ret = PTR_ERR(record->buf);
 		goto out;
@@ -546,7 +449,7 @@ static int pstore_write_user_compat(struct pstore_record *record,
 
 	ret = record->psi->write(record);
 
-	kfree(record->buf);
+	kvfree(record->buf);
 out:
 	record->buf = NULL;
 
@@ -562,11 +465,12 @@ out:
  */
 int pstore_register(struct pstore_info *psi)
 {
-	struct module *owner = psi->owner;
+	char *new_backend;
 
 	if (backend && strcmp(backend, psi->name)) {
-		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
-		return -EPERM;
+		pr_warn("backend '%s' already in use: ignoring '%s'\n",
+			backend, psi->name);
+		return -EBUSY;
 	}
 
 	/* Sanity check flags. */
@@ -583,11 +487,16 @@ int pstore_register(struct pstore_info *psi)
 		return -EINVAL;
 	}
 
-	spin_lock(&pstore_lock);
+	new_backend = kstrdup(psi->name, GFP_KERNEL);
+	if (!new_backend)
+		return -ENOMEM;
+
+	mutex_lock(&psinfo_lock);
 	if (psinfo) {
 		pr_warn("backend '%s' already loaded: ignoring '%s'\n",
 			psinfo->name, psi->name);
-		spin_unlock(&pstore_lock);
+		mutex_unlock(&psinfo_lock);
+		kfree(new_backend);
 		return -EBUSY;
 	}
 
@@ -595,21 +504,17 @@ int pstore_register(struct pstore_info *psi)
 		psi->write_user = pstore_write_user_compat;
 	psinfo = psi;
 	mutex_init(&psinfo->read_mutex);
-	sema_init(&psinfo->buf_lock, 1);
-	spin_unlock(&pstore_lock);
+	raw_spin_lock_init(&psinfo->buf_lock);
 
-	if (owner && !try_module_get(owner)) {
-		psinfo = NULL;
-		return -EINVAL;
-	}
-
-	allocate_buf_for_compression();
+	if (psi->flags & PSTORE_FLAGS_DMESG)
+		allocate_buf_for_compression();
 
-	if (pstore_is_mounted())
-		pstore_get_records(0);
+	pstore_get_records(0);
 
-	if (psi->flags & PSTORE_FLAGS_DMESG)
+	if (psi->flags & PSTORE_FLAGS_DMESG) {
+		pstore_dumper.max_reason = psinfo->max_reason;
 		pstore_register_kmsg();
+	}
 	if (psi->flags & PSTORE_FLAGS_CONSOLE)
 		pstore_register_console();
 	if (psi->flags & PSTORE_FLAGS_FTRACE)
@@ -618,33 +523,36 @@ int pstore_register(struct pstore_info *psi)
 		pstore_register_pmsg();
 
 	/* Start watching for new records, if desired. */
-	if (pstore_update_ms >= 0) {
-		pstore_timer.expires = jiffies +
-			msecs_to_jiffies(pstore_update_ms);
-		add_timer(&pstore_timer);
-	}
+	pstore_timer_kick();
 
 	/*
 	 * Update the module parameter backend, so it is visible
 	 * through /sys/module/pstore/parameters/backend
 	 */
-	backend = psi->name;
+	backend = new_backend;
 
 	pr_info("Registered %s as persistent store backend\n", psi->name);
 
-	module_put(owner);
-
+	mutex_unlock(&psinfo_lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pstore_register);
 
 void pstore_unregister(struct pstore_info *psi)
 {
-	/* Stop timer and make sure all work has finished. */
-	pstore_update_ms = -1;
-	del_timer_sync(&pstore_timer);
-	flush_work(&pstore_work);
+	/* It's okay to unregister nothing. */
+	if (!psi)
+		return;
 
+	mutex_lock(&psinfo_lock);
+
+	/* Only one backend can be registered at a time. */
+	if (WARN_ON(psi != psinfo)) {
+		mutex_unlock(&psinfo_lock);
+		return;
+	}
+
+	/* Unregister all callbacks. */
 	if (psi->flags & PSTORE_FLAGS_PMSG)
 		pstore_unregister_pmsg();
 	if (psi->flags & PSTORE_FLAGS_FTRACE)
@@ -654,20 +562,33 @@ void pstore_unregister(struct pstore_info *psi)
 	if (psi->flags & PSTORE_FLAGS_DMESG)
 		pstore_unregister_kmsg();
 
+	/* Stop timer and make sure all work has finished. */
+	timer_delete_sync(&pstore_timer);
+	flush_work(&pstore_work);
+
+	/* Remove all backend records from filesystem tree. */
+	pstore_put_backend_records(psi);
+
 	free_buf_for_compression();
 
 	psinfo = NULL;
+	kfree(backend);
 	backend = NULL;
+
+	pr_info("Unregistered %s as persistent store backend\n", psi->name);
+	mutex_unlock(&psinfo_lock);
 }
 EXPORT_SYMBOL_GPL(pstore_unregister);
 
-static void decompress_record(struct pstore_record *record)
+static void decompress_record(struct pstore_record *record,
+			      struct z_stream_s *zstream)
 {
 	int ret;
 	int unzipped_len;
 	char *unzipped, *workspace;
+	size_t max_uncompressed_size;
 
-	if (!record->compressed)
+	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !record->compressed)
 		return;
 
 	/* Only PSTORE_TYPE_DMESG support compression. */
@@ -677,40 +598,51 @@ static void decompress_record(struct pstore_record *record)
 	}
 
 	/* Missing compression buffer means compression was not initialized. */
-	if (!big_oops_buf) {
+	if (!zstream->workspace) {
 		pr_warn("no decompression method initialized!\n");
 		return;
 	}
 
+	ret = zlib_inflateReset(zstream);
+	if (ret != Z_OK) {
+		pr_err("zlib_inflateReset() failed, ret = %d!\n", ret);
+		return;
+	}
+
 	/* Allocate enough space to hold max decompression and ECC. */
-	unzipped_len = big_oops_buf_sz;
-	workspace = kmalloc(unzipped_len + record->ecc_notice_size,
-			    GFP_KERNEL);
+	max_uncompressed_size = 3 * psinfo->bufsize;
+	workspace = kvzalloc(max_uncompressed_size + record->ecc_notice_size,
+			     GFP_KERNEL);
 	if (!workspace)
 		return;
 
-	/* After decompression "unzipped_len" is almost certainly smaller. */
-	ret = crypto_comp_decompress(tfm, record->buf, record->size,
-					  workspace, &unzipped_len);
-	if (ret) {
-		pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
-		kfree(workspace);
+	zstream->next_in	= record->buf;
+	zstream->avail_in	= record->size;
+	zstream->next_out	= workspace;
+	zstream->avail_out	= max_uncompressed_size;
+
+	ret = zlib_inflate(zstream, Z_FINISH);
+	if (ret != Z_STREAM_END) {
+		pr_err_ratelimited("zlib_inflate() failed, ret = %d!\n", ret);
+		kvfree(workspace);
 		return;
 	}
 
+	unzipped_len = zstream->total_out;
+
 	/* Append ECC notice to decompressed buffer. */
 	memcpy(workspace + unzipped_len, record->buf + record->size,
 	       record->ecc_notice_size);
 
 	/* Copy decompressed contents into an minimum-sized allocation. */
-	unzipped = kmemdup(workspace, unzipped_len + record->ecc_notice_size,
-			   GFP_KERNEL);
-	kfree(workspace);
+	unzipped = kvmemdup(workspace, unzipped_len + record->ecc_notice_size,
+			    GFP_KERNEL);
+	kvfree(workspace);
 	if (!unzipped)
 		return;
 
 	/* Swap out compressed contents with decompressed contents. */
-	kfree(record->buf);
+	kvfree(record->buf);
 	record->buf = unzipped;
 	record->size = unzipped_len;
 	record->compressed = false;
@@ -727,10 +659,17 @@ void pstore_get_backend_records(struct pstore_info *psi,
 {
 	int failed = 0;
 	unsigned int stop_loop = 65536;
+	struct z_stream_s zstream = {};
 
 	if (!psi || !root)
 		return;
 
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) {
+		zstream.workspace = kvmalloc(zlib_inflate_workspacesize(),
+					     GFP_KERNEL);
+		zlib_inflateInit2(&zstream, -DEF_WBITS);
+	}
+
 	mutex_lock(&psi->read_mutex);
 	if (psi->open && psi->open(psi))
 		goto out;
@@ -759,11 +698,12 @@ void pstore_get_backend_records(struct pstore_info *psi,
 			break;
 		}
 
-		decompress_record(record);
+		decompress_record(record, &zstream);
 		rc = pstore_mkfile(root, record);
 		if (rc) {
 			/* pstore_mkfile() did not take record, so free it. */
-			kfree(record->buf);
+			kvfree(record->buf);
+			kfree(record->priv);
 			kfree(record);
 			if (rc != -EEXIST || !quiet)
 				failed++;
@@ -774,6 +714,12 @@ void pstore_get_backend_records(struct pstore_info *psi,
 out:
 	mutex_unlock(&psi->read_mutex);
 
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && compress) {
+		if (zlib_inflateEnd(&zstream) != Z_OK)
+			pr_warn("zlib_inflateEnd() failed\n");
+		kvfree(zstream.workspace);
+	}
+
 	if (failed)
 		pr_warn("failed to create %d record(s) from '%s'\n",
 			failed, psi->name);
@@ -794,44 +740,18 @@ static void pstore_timefunc(struct timer_list *unused)
 		schedule_work(&pstore_work);
 	}
 
-	if (pstore_update_ms >= 0)
-		mod_timer(&pstore_timer,
-			  jiffies + msecs_to_jiffies(pstore_update_ms));
-}
-
-void __init pstore_choose_compression(void)
-{
-	const struct pstore_zbackend *step;
-
-	if (!compress)
-		return;
-
-	for (step = zbackends; step->name; step++) {
-		if (!strcmp(compress, step->name)) {
-			zbackend = step;
-			return;
-		}
-	}
+	pstore_timer_kick();
 }
 
 static int __init pstore_init(void)
 {
 	int ret;
 
-	pstore_choose_compression();
-
-	/*
-	 * Check if any pstore backends registered earlier but did not
-	 * initialize compression because crypto was not ready. If so,
-	 * initialize compression now.
-	 */
-	allocate_buf_for_compression();
-
 	ret = pstore_init_fs();
 	if (ret)
-		return ret;
+		free_buf_for_compression();
 
-	return 0;
+	return ret;
 }
 late_initcall(pstore_init);
 
@@ -841,11 +761,6 @@ static void __exit pstore_exit(void)
 }
 module_exit(pstore_exit)
 
-module_param(compress, charp, 0444);
-MODULE_PARM_DESC(compress, "Pstore compression to use");
-
-module_param(backend, charp, 0444);
-MODULE_PARM_DESC(backend, "Pstore backend to use");
-
 MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
+MODULE_DESCRIPTION("Persistent Storage - platform driver interface");
 MODULE_LICENSE("GPL");