text: // 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>
   */
  
  #define pr_fmt(fmt) "pstore: " fmt
  
  #include <linux/atomic.h>
  #include <linux/types.h>
  #include <linux/errno.h>
  #include <linux/init.h>
  #include <linux/kmsg_dump.h>
  #include <linux/console.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/workqueue.h>
  
  #include "internal.h"
  
  /*
   * We defer making "oops" entries appear in pstore - see
   * whether the system is actually still running well enough
   * to let someone see the entry
   */
  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 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 */
  static const char * const pstore_type_names[] = {
  	"dmesg",
  	"mce",
  	"console",
  	"ftrace",
  	"rtas",
  	"powerpc-ofw",
  	"powerpc-common",
  	"pmsg",
  	"powerpc-opal",
  };
  
  static int pstore_new_entry;
  
  static void pstore_timefunc(struct timer_list *);
  static DEFINE_TIMER(pstore_timer, pstore_timefunc);
  
  static void pstore_dowork(struct work_struct *);
  static DECLARE_WORK(pstore_work, pstore_dowork);
  
  /*
   * psinfo_lock protects "psinfo" during calls to
   * pstore_register(), pstore_unregister(), and
   * the filesystem mount/unmount routines.
   */
  static DEFINE_MUTEX(psinfo_lock);
  struct pstore_info *psinfo;
  
  static char *backend;
  module_param(backend, charp, 0444);
  MODULE_PARM_DESC(backend, "specific backend to use");
  
  static char *compress =
  #ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
  		CONFIG_PSTORE_COMPRESS_DEFAULT;
  #else
  		NULL;
  #endif
  module_param(compress, charp, 0444);
  MODULE_PARM_DESC(compress, "compression to use");
  
  /* Compression parameters */
  static struct crypto_comp *tfm;
  
  struct pstore_zbackend {
  	int (*zbufsize)(size_t size);
  	const char *name;
  };
  
  static char *big_oops_buf;
  static size_t big_oops_buf_sz;
  
  /* How much of the console log to snapshot */
  unsigned long kmsg_bytes = PSTORE_DEFAULT_KMSG_BYTES;
  
  void pstore_set_kmsg_bytes(int bytes)
  {
  	kmsg_bytes = bytes;
  }
  
  /* Tag each group of saved records with a sequence number */
  static int	oopscount;
  
  const char *pstore_type_to_name(enum pstore_type_id type)
  {
  	BUILD_BUG_ON(ARRAY_SIZE(pstore_type_names) != PSTORE_TYPE_MAX);
  
  	if (WARN_ON_ONCE(type >= PSTORE_TYPE_MAX))
  		return "unknown";
  
  	return pstore_type_names[type];
  }
  EXPORT_SYMBOL_GPL(pstore_type_to_name);
  
  enum pstore_type_id pstore_name_to_type(const char *name)
  {
  	int i;
  
  	for (i = 0; i < PSTORE_TYPE_MAX; i++) {
  		if (!strcmp(pstore_type_names[i], name))
  			return i;
  	}
  
  	return PSTORE_TYPE_MAX;
  }
  EXPORT_SYMBOL_GPL(pstore_name_to_type);
  
  static void pstore_timer_kick(void)
  {
  	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)
  {
  	/* In NMI path, pstore shouldn't block 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. */
  	case KMSG_DUMP_EMERG:
  		return true;
  	default:
  		return false;
  	}
  }
  
  #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)
  {
  	int ret;
  
  	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS))
  		return -EINVAL;
  
  	ret = crypto_comp_compress(tfm, in, inlen, out, &outlen);
  	if (ret) {
  		pr_err("crypto_comp_compress failed, ret = %d!\n", ret);
  		return ret;
  	}
  
  	return outlen;
  }
  
  static void allocate_buf_for_compression(void)
  {
  	struct crypto_comp *ctx;
  	int 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);
  		return;
  	}
  
  	size = zbackend->zbufsize(psinfo->bufsize);
  	if (size <= 0) {
  		pr_err("Invalid compression size for %s: %d\n",
  		       zbackend->name, size);
  		return;
  	}
  
  	buf = kmalloc(size, GFP_KERNEL);
  	if (!buf) {
  		pr_err("Failed %d byte compression buffer allocation for: %s\n",
  		       size, zbackend->name);
  		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));
  		return;
  	}
  
  	/* A non-NULL big_oops_buf indicates compression is available. */
  	tfm = ctx;
  	big_oops_buf_sz = size;
  	big_oops_buf = buf;
  
  	pr_info("Using crash dump compression: %s\n", zbackend->name);
  }
  
  static void free_buf_for_compression(void)
  {
  	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm) {
  		crypto_free_comp(tfm);
  		tfm = NULL;
  	}
  	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);
  
  	return total_len;
  }
  
  void pstore_record_init(struct pstore_record *record,
  			struct pstore_info *psinfo)
  {
  	memset(record, 0, sizeof(*record));
  
  	record->psi = psinfo;
  
  	/* Report zeroed timestamp if called before timekeeping has resumed. */
  	record->time = ns_to_timespec64(ktime_get_real_fast_ns());
  }
  
  /*
   * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from the
   * end of the buffer.
   */
  static void pstore_dump(struct kmsg_dumper *dumper,
  			enum kmsg_dump_reason reason,
  			struct kmsg_dumper_iter *iter)
  {
  	unsigned long	total = 0;
  	const char	*why;
  	unsigned int	part = 1;
  	int		ret;
  
  	why = kmsg_dump_reason_str(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");
  			return;
  		}
  	}
  
  	oopscount++;
  	while (total < kmsg_bytes) {
  		char *dst;
  		size_t dst_size;
  		int header_size;
  		int zipped_len = -1;
  		size_t dump_size;
  		struct pstore_record record;
  
  		pstore_record_init(&record, psinfo);
  		record.type = PSTORE_TYPE_DMESG;
  		record.count = oopscount;
  		record.reason = 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;
  		}
  
  		/* Write dump header. */
  		header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
  				 oopscount, part);
  		dst_size -= header_size;
  
  		/* Write dump contents. */
  		if (!kmsg_dump_get_buffer(iter, true, dst + header_size,
  					  dst_size, &dump_size))
  			break;
  
  		if (big_oops_buf) {
  			zipped_len = pstore_compress(dst, psinfo->buf,
  						header_size + dump_size,
  						psinfo->bufsize);
  
  			if (zipped_len > 0) {
  				record.compressed = true;
  				record.size = zipped_len;
  			} else {
  				record.size = copy_kmsg_to_buffer(header_size,
  								  dump_size);
  			}
  		} else {
  			record.size = header_size + dump_size;
  		}
  
  		ret = psinfo->write(&record);
  		if (ret == 0 && reason == KMSG_DUMP_OOPS) {
  			pstore_new_entry = 1;
  			pstore_timer_kick();
  		}
  
  		total += record.size;
  		part++;
  	}
  
  	up(&psinfo->buf_lock);
  }
  
  static struct kmsg_dumper pstore_dumper = {
  	.dump = pstore_dump,
  };
  
  /*
   * Register with kmsg_dump to save last part of console log on panic.
   */
  static void pstore_register_kmsg(void)
  {
  	kmsg_dump_register(&pstore_dumper);
  }
  
  static void pstore_unregister_kmsg(void)
  {
  	kmsg_dump_unregister(&pstore_dumper);
  }
  
  #ifdef CONFIG_PSTORE_CONSOLE
  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;
  
  	record.buf = (char *)s;
  	record.size = c;
  	psinfo->write(&record);
  }
  
  static struct console pstore_console = {
  	.write	= pstore_console_write,
  	.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);
  }
  
  static void pstore_unregister_console(void)
  {
  	unregister_console(&pstore_console);
  }
  #else
  static void pstore_register_console(void) {}
  static void pstore_unregister_console(void) {}
  #endif
  
  static int pstore_write_user_compat(struct pstore_record *record,
  				    const char __user *buf)
  {
  	int ret = 0;
  
  	if (record->buf)
  		return -EINVAL;
  
  	record->buf = memdup_user(buf, record->size);
  	if (IS_ERR(record->buf)) {
  		ret = PTR_ERR(record->buf);
  		goto out;
  	}
  
  	ret = record->psi->write(record);
  
  	kfree(record->buf);
  out:
  	record->buf = NULL;
  
  	return unlikely(ret < 0) ? ret : record->size;
  }
  
  /*
   * platform specific persistent storage driver registers with
   * us here. If pstore is already mounted, call the platform
   * read function right away to populate the file system. If not
   * then the pstore mount code will call us later to fill out
   * the file system.
   */
  int pstore_register(struct pstore_info *psi)
  {
  	if (backend && strcmp(backend, psi->name)) {
  		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
  		return -EPERM;
  	}
  
  	/* Sanity check flags. */
  	if (!psi->flags) {
  		pr_warn("backend '%s' must support at least one frontend\n",
  			psi->name);
  		return -EINVAL;
  	}
  
  	/* Check for required functions. */
  	if (!psi->read || !psi->write) {
  		pr_warn("backend '%s' must implement read() and write()\n",
  			psi->name);
  		return -EINVAL;
  	}
  
  	mutex_lock(&psinfo_lock);
  	if (psinfo) {
  		pr_warn("backend '%s' already loaded: ignoring '%s'\n",
  			psinfo->name, psi->name);
  		mutex_unlock(&psinfo_lock);
  		return -EBUSY;
  	}
  
  	if (!psi->write_user)
  		psi->write_user = pstore_write_user_compat;
  	psinfo = psi;
  	mutex_init(&psinfo->read_mutex);
  	sema_init(&psinfo->buf_lock, 1);
  
  	if (psi->flags & PSTORE_FLAGS_DMESG)
  		allocate_buf_for_compression();
  
  	pstore_get_records(0);
  
  	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)
  		pstore_register_ftrace();
  	if (psi->flags & PSTORE_FLAGS_PMSG)
  		pstore_register_pmsg();
  
  	/* Start watching for new records, if desired. */
  	pstore_timer_kick();
  
  	/*
  	 * Update the module parameter backend, so it is visible
  	 * through /sys/module/pstore/parameters/backend
  	 */
  	backend = kstrdup(psi->name, GFP_KERNEL);
  
  	pr_info("Registered %s as persistent store backend\n", psi->name);
  
  	mutex_unlock(&psinfo_lock);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(pstore_register);
  
  void pstore_unregister(struct pstore_info *psi)
  {
  	/* 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)
  		pstore_unregister_ftrace();
  	if (psi->flags & PSTORE_FLAGS_CONSOLE)
  		pstore_unregister_console();
  	if (psi->flags & PSTORE_FLAGS_DMESG)
  		pstore_unregister_kmsg();
  
  	/* Stop timer and make sure all work has finished. */
  	del_timer_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;
  	mutex_unlock(&psinfo_lock);
  }
  EXPORT_SYMBOL_GPL(pstore_unregister);
  
  static void decompress_record(struct pstore_record *record)
  {
  	int ret;
  	int unzipped_len;
  	char *unzipped, *workspace;
  
  	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !record->compressed)
  		return;
  
  	/* Only PSTORE_TYPE_DMESG support compression. */
  	if (record->type != PSTORE_TYPE_DMESG) {
  		pr_warn("ignored compressed record type %d\n", record->type);
  		return;
  	}
  
  	/* Missing compression buffer means compression was not initialized. */
  	if (!big_oops_buf) {
  		pr_warn("no decompression method initialized!\n");
  		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);
  	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);
  		return;
  	}
  
  	/* 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);
  	if (!unzipped)
  		return;
  
  	/* Swap out compressed contents with decompressed contents. */
  	kfree(record->buf);
  	record->buf = unzipped;
  	record->size = unzipped_len;
  	record->compressed = false;
  }
  
  /*
   * Read all the records from one persistent store backend. Create
   * files in our filesystem.  Don't warn about -EEXIST errors
   * when we are re-scanning the backing store looking to add new
   * error records.
   */
  void pstore_get_backend_records(struct pstore_info *psi,
  				struct dentry *root, int quiet)
  {
  	int failed = 0;
  	unsigned int stop_loop = 65536;
  
  	if (!psi || !root)
  		return;
  
  	mutex_lock(&psi->read_mutex);
  	if (psi->open && psi->open(psi))
  		goto out;
  
  	/*
  	 * Backend callback read() allocates record.buf. decompress_record()
  	 * may reallocate record.buf. On success, pstore_mkfile() will keep
  	 * the record.buf, so free it only on failure.
  	 */
  	for (; stop_loop; stop_loop--) {
  		struct pstore_record *record;
  		int rc;
  
  		record = kzalloc(sizeof(*record), GFP_KERNEL);
  		if (!record) {
  			pr_err("out of memory creating record\n");
  			break;
  		}
  		pstore_record_init(record, psi);
  
  		record->size = psi->read(record);
  
  		/* No more records left in backend? */
  		if (record->size <= 0) {
  			kfree(record);
  			break;
  		}
  
  		decompress_record(record);
  		rc = pstore_mkfile(root, record);
  		if (rc) {
  			/* pstore_mkfile() did not take record, so free it. */
  			kfree(record->buf);
  			kfree(record);
  			if (rc != -EEXIST || !quiet)
  				failed++;
  		}
  	}
  	if (psi->close)
  		psi->close(psi);
  out:
  	mutex_unlock(&psi->read_mutex);
  
  	if (failed)
  		pr_warn("failed to create %d record(s) from '%s'\n",
  			failed, psi->name);
  	if (!stop_loop)
  		pr_err("looping? Too many records seen from '%s'\n",
  			psi->name);
  }
  
  static void pstore_dowork(struct work_struct *work)
  {
  	pstore_get_records(1);
  }
  
  static void pstore_timefunc(struct timer_list *unused)
  {
  	if (pstore_new_entry) {
  		pstore_new_entry = 0;
  		schedule_work(&pstore_work);
  	}
  
  	pstore_timer_kick();
  }
  
  static 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;
  		}
  	}
  }
  
  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)
  		free_buf_for_compression();
  
  	return ret;
  }
  late_initcall(pstore_init);
  
  static void __exit pstore_exit(void)
  {
  	pstore_exit_fs();
  }
  module_exit(pstore_exit)
  
  MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
  MODULE_LICENSE("GPL");
  