Message-ID: <a9d47bf1-7498-1d07-a943-29dd0b0ef2e1@allwinnertech.com>
Date:   Tue, 12 May 2020 11:55:20 +0800
From:   WeiXiong Liao <liaoweixiong@...winnertech.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh@...nel.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v8 01/11] pstore/zone: Introduce common layer to manage
 storage zones

hi Kees Cook,

On 2020/5/12 AM 7:32, Kees Cook wrote:
> From: WeiXiong Liao <liaoweixiong@...winnertech.com>
> 
> Implement a common set of APIs needed to support pstore storage zones,
> based on how ramoops is designed. This will be used by pstore/blk with
> the intention of migrating pstore/ram in the future.
> 
> Signed-off-by: WeiXiong Liao <liaoweixiong@...winnertech.com>
> Link: https://lore.kernel.org/r/1585126506-18635-2-git-send-email-liaoweixiong@allwinnertech.com
> Co-developed-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  fs/pstore/Kconfig           |   7 +
>  fs/pstore/Makefile          |   3 +
>  fs/pstore/zone.c            | 987 ++++++++++++++++++++++++++++++++++++
>  include/linux/pstore_zone.h |  44 ++
>  4 files changed, 1041 insertions(+)
>  create mode 100644 fs/pstore/zone.c
>  create mode 100644 include/linux/pstore_zone.h
> 
> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
> index 8f0369aad22a..98d2457bdd9f 100644
> --- a/fs/pstore/Kconfig
> +++ b/fs/pstore/Kconfig
> @@ -153,3 +153,10 @@ config PSTORE_RAM
>  	  "ramoops.ko".
>  
>  	  For more information, see Documentation/admin-guide/ramoops.rst.
> +
> +config PSTORE_ZONE
> +	tristate
> +	depends on PSTORE
> +	help
> +	  The common layer for pstore/blk (and pstore/ram in the future)
> +	  to manage storage in zones.
> diff --git a/fs/pstore/Makefile b/fs/pstore/Makefile
> index 967b5891f325..58a967cbe4af 100644
> --- a/fs/pstore/Makefile
> +++ b/fs/pstore/Makefile
> @@ -12,3 +12,6 @@ pstore-$(CONFIG_PSTORE_PMSG)	+= pmsg.o
>  
>  ramoops-objs += ram.o ram_core.o
>  obj-$(CONFIG_PSTORE_RAM)	+= ramoops.o
> +
> +pstore_zone-objs += zone.o
> +obj-$(CONFIG_PSTORE_ZONE)	+= pstore_zone.o
> diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
> new file mode 100644
> index 000000000000..20fa52385c78
> --- /dev/null
> +++ b/fs/pstore/zone.c
> @@ -0,0 +1,987 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Provide a pstore intermediate backend, organized into kernel memory
> + * allocated zones that are then mapped and flushed into a single
> + * contiguous region on a storage backend of some kind (block, mtd, etc).
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/mount.h>
> +#include <linux/printk.h>
> +#include <linux/fs.h>
> +#include <linux/pstore_zone.h>
> +#include <linux/kdev_t.h>
> +#include <linux/device.h>
> +#include <linux/namei.h>
> +#include <linux/fcntl.h>
> +#include <linux/uio.h>
> +#include <linux/writeback.h>
> +#include "internal.h"
> +
> +/**
> + * struct psz_head - header of zone to flush to storage
> + *
> + * @sig: signature to indicate header (PSZ_SIG xor PSZONE-type value)
> + * @datalen: length of data in @data
> + * @data: zone data.
> + */
> +struct psz_buffer {
> +#define PSZ_SIG (0x43474244) /* DBGC */
> +	uint32_t sig;
> +	atomic_t datalen;
> +	uint8_t data[];
> +};
> +
> +/**
> + * struct psz_kmsg_header - kmsg dump-specific header to flush to storage
> + *
> + * @magic: magic num for kmsg dump header
> + * @time: kmsg dump trigger time
> + * @compressed: whether conpressed
> + * @counter: kmsg dump counter
> + * @reason: the kmsg dump reason (e.g. oops, panic, etc)
> + * @data: pointer to log data
> + *
> + * This is a sub-header for a kmsg dump, trailing after &psz_buffer.
> + */
> +struct psz_kmsg_header {
> +#define PSTORE_KMSG_HEADER_MAGIC 0x4dfc3ae5 /* Just a random number */
> +	uint32_t magic;
> +	struct timespec64 time;
> +	bool compressed;
> +	uint32_t counter;
> +	enum kmsg_dump_reason reason;
> +	uint8_t data[];
> +};
> +
> +/**
> + * struct pstore_zone - single stored buffer
> + *
> + * @off: zone offset of storage
> + * @type: front-end type for this zone
> + * @name: front-end name for this zone
> + * @buffer: pointer to data buffer managed by this zone
> + * @oldbuf: pointer to old data buffer
> + * @buffer_size: bytes in @buffer->data
> + * @should_recover: whether this zone should recover from storage
> + * @dirty: whether the data in @buffer dirty
> + *
> + * zone structure in memory.
> + */
> +struct pstore_zone {
> +	loff_t off;
> +	const char *name;
> +	enum pstore_type_id type;
> +
> +	struct psz_buffer *buffer;
> +	struct psz_buffer *oldbuf;
> +	size_t buffer_size;
> +	bool should_recover;
> +	atomic_t dirty;
> +};
> +
> +/**
> + * struct psz_context - all about running state of pstore/zone
> + *
> + * @kpszs: kmsg dump storage zones
> + * @kmsg_max_cnt: max count of @kpszs
> + * @kmsg_read_cnt: counter of total read kmsg dumps
> + * @kmsg_write_cnt: counter of total kmsg dump writes
> + * @oops_counter: counter of oops dumps
> + * @panic_counter: counter of panic dumps
> + * @recovered: whether finished recovering data from storage
> + * @on_panic: whether panic is happening
> + * @pstore_zone_info_lock: lock to @pstore_zone_info
> + * @pstore_zone_info: information from backend
> + * @pstore: structure for pstore
> + */
> +struct psz_context {
> +	struct pstore_zone **kpszs;
> +	unsigned int kmsg_max_cnt;
> +	unsigned int kmsg_read_cnt;
> +	unsigned int kmsg_write_cnt;
> +	/*
> +	 * These counters should be calculated during recovery.
> +	 * It records the oops/panic times after crashes rather than boots.
> +	 */
> +	unsigned int oops_counter;
> +	unsigned int panic_counter;

oops/panic_counter is designed to count the crash times since the
linux kernel was installed. pstore/zone lookup the max counter from all
valid kmsg zones when recovery and saves them to oops/panic_counter.
However, they are unable to get real number if we remove files. It's
not serious, we can fix it after this series.

And since pstore supports "max_reason", should pstore/zone count for
other reason?

> +	atomic_t recovered;
> +	atomic_t on_panic;
> +
> +	/*
> +	 * pstore_zone_info_lock protects this entire structure during calls
> +	 * to register_pstore_zone()/unregister_pstore_zone().
> +	 */
> +	struct mutex pstore_zone_info_lock;
> +	struct pstore_zone_info *pstore_zone_info;
> +	struct pstore_info pstore;
> +};
> +static struct psz_context pstore_zone_cxt;
> +
> +/**
> + * enum psz_flush_mode - flush mode for psz_zone_write()
> + *
> + * @FLUSH_NONE: do not flush to storage but update data on memory
> + * @FLUSH_PART: just flush part of data including meta data to storage
> + * @FLUSH_META: just flush meta data of zone to storage
> + * @FLUSH_ALL: flush all of zone
> + */
> +enum psz_flush_mode {
> +	FLUSH_NONE = 0,
> +	FLUSH_PART,
> +	FLUSH_META,
> +	FLUSH_ALL,
> +};
> +
> +static inline int buffer_datalen(struct pstore_zone *zone)
> +{
> +	return atomic_read(&zone->buffer->datalen);
> +}
> +
> +static inline bool is_on_panic(void)
> +{
> +	return atomic_read(&pstore_zone_cxt.on_panic);
> +}
> +
> +static ssize_t psz_zone_read(struct pstore_zone *zone, char *buf,
> +		size_t len, unsigned long off)
> +{
> +	if (!buf || !zone->buffer)
> +		return -EINVAL;
> +	if (off > zone->buffer_size)
> +		return -EINVAL;
> +	len = min_t(size_t, len, zone->buffer_size - off);
> +	memcpy(buf, zone->buffer->data + off, len);
> +	return len;
> +}
> +
> +static int psz_zone_write(struct pstore_zone *zone,
> +		enum psz_flush_mode flush_mode, const char *buf,
> +		size_t len, unsigned long off)
> +{
> +	struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
> +	ssize_t wcnt = 0;
> +	ssize_t (*writeop)(const char *buf, size_t bytes, loff_t pos);
> +	size_t wlen;
> +
> +	if (off > zone->buffer_size)
> +		return -EINVAL;
> +
> +	wlen = min_t(size_t, len, zone->buffer_size - off);
> +	if (buf && wlen) {
> +		memcpy(zone->buffer->data + off, buf, wlen);
> +		atomic_set(&zone->buffer->datalen, wlen + off);
> +	}
> +
> +	/* avoid to damage old records */
> +	if (!is_on_panic() && !atomic_read(&pstore_zone_cxt.recovered))
> +		goto dirty;
> +
> +	writeop = is_on_panic() ? info->panic_write : info->write;
> +	if (!writeop)
> +		goto dirty;
> +
> +	switch (flush_mode) {
> +	case FLUSH_NONE:
> +		if (unlikely(buf && wlen))
> +			goto dirty;
> +		return 0;
> +	case FLUSH_PART:
> +		wcnt = writeop((const char *)zone->buffer->data + off, wlen,
> +				zone->off + sizeof(*zone->buffer) + off);
> +		if (wcnt != wlen)
> +			goto dirty;
> +		fallthrough;
> +	case FLUSH_META:
> +		wlen = sizeof(struct psz_buffer);
> +		wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
> +		if (wcnt != wlen)
> +			goto dirty;
> +		break;
> +	case FLUSH_ALL:
> +		wlen = zone->buffer_size + sizeof(*zone->buffer);
> +		wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
> +		if (wcnt != wlen)
> +			goto dirty;
> +		break;
> +	}
> +
> +	return 0;
> +dirty:
> +	atomic_set(&zone->dirty, true);
> +	return -EBUSY;
> +}
> +
> +static int psz_flush_dirty_zone(struct pstore_zone *zone)
> +{
> +	int ret;
> +
> +	if (unlikely(!zone))
> +		return -EINVAL;
> +
> +	if (unlikely(!atomic_read(&pstore_zone_cxt.recovered)))
> +		return -EBUSY;
> +
> +	if (!atomic_xchg(&zone->dirty, false))
> +		return 0;
> +
> +	ret = psz_zone_write(zone, FLUSH_ALL, NULL, 0, 0);
> +	if (ret)
> +		atomic_set(&zone->dirty, true);
> +	return ret;
> +}
> +
> +static int psz_flush_dirty_zones(struct pstore_zone **zones, unsigned int cnt)
> +{
> +	int i, ret;
> +	struct pstore_zone *zone;
> +
> +	if (!zones)
> +		return -EINVAL;
> +
> +	for (i = 0; i < cnt; i++) {
> +		zone = zones[i];
> +		if (!zone)
> +			return -EINVAL;
> +		ret = psz_flush_dirty_zone(zone);
> +		if (ret)
> +			return ret;
> +	}
> +	return 0;
> +}
> +
> +static int psz_move_zone(struct pstore_zone *old, struct pstore_zone *new)
> +{
> +	const char *data = (const char *)old->buffer->data;
> +	int ret;
> +
> +	ret = psz_zone_write(new, FLUSH_ALL, data, buffer_datalen(old), 0);
> +	if (ret) {
> +		atomic_set(&new->buffer->datalen, 0);
> +		atomic_set(&new->dirty, false);
> +		return ret;
> +	}
> +	atomic_set(&old->buffer->datalen, 0);
> +	return 0;
> +}
> +
> +static int psz_kmsg_recover_data(struct psz_context *cxt)
> +{
> +	struct pstore_zone_info *info = cxt->pstore_zone_info;
> +	struct pstore_zone *zone = NULL;
> +	struct psz_buffer *buf;
> +	unsigned long i;
> +	ssize_t rcnt;
> +
> +	if (!info->read)
> +		return -EINVAL;
> +
> +	for (i = 0; i < cxt->kmsg_max_cnt; i++) {
> +		zone = cxt->kpszs[i];
> +		if (unlikely(!zone))
> +			return -EINVAL;
> +		if (atomic_read(&zone->dirty)) {
> +			unsigned int wcnt = cxt->kmsg_write_cnt;
> +			struct pstore_zone *new = cxt->kpszs[wcnt];
> +			int ret;
> +
> +			ret = psz_move_zone(zone, new);
> +			if (ret) {
> +				pr_err("move zone from %lu to %d failed\n",
> +						i, wcnt);
> +				return ret;
> +			}
> +			cxt->kmsg_write_cnt = (wcnt + 1) % cxt->kmsg_max_cnt;
> +		}
> +		if (!zone->should_recover)
> +			continue;
> +		buf = zone->buffer;
> +		rcnt = info->read((char *)buf, zone->buffer_size + sizeof(*buf),
> +				zone->off);
> +		if (rcnt != zone->buffer_size + sizeof(*buf))
> +			return (int)rcnt < 0 ? (int)rcnt : -EIO;
> +	}
> +	return 0;
> +}
> +
> +static int psz_kmsg_recover_meta(struct psz_context *cxt)
> +{
> +	struct pstore_zone_info *info = cxt->pstore_zone_info;
> +	struct pstore_zone *zone;
> +	size_t rcnt, len;
> +	struct psz_buffer *buf;
> +	struct psz_kmsg_header *hdr;
> +	struct timespec64 time = { };
> +	unsigned long i;
> +	/*
> +	 * Recover may on panic, we can't allocate any memory by kmalloc.
> +	 * So, we use local array instead.
> +	 */
> +	char buffer_header[sizeof(*buf) + sizeof(*hdr)] = {0};
> +
> +	if (!info->read)
> +		return -EINVAL;
> +
> +	len = sizeof(*buf) + sizeof(*hdr);
> +	buf = (struct psz_buffer *)buffer_header;
> +	for (i = 0; i < cxt->kmsg_max_cnt; i++) {
> +		zone = cxt->kpszs[i];
> +		if (unlikely(!zone))
> +			return -EINVAL;
> +
> +		rcnt = info->read((char *)buf, len, zone->off);
> +		if (rcnt != len) {
> +			pr_err("read %s with id %lu failed\n", zone->name, i);
> +			return (int)rcnt < 0 ? (int)rcnt : -EIO;
> +		}
> +
> +		if (buf->sig != zone->buffer->sig) {
> +			pr_debug("no valid data in kmsg dump zone %lu\n", i);
> +			continue;
> +		}
> +
> +		if (zone->buffer_size < atomic_read(&buf->datalen)) {
> +			pr_info("found overtop zone: %s: id %lu, off %lld, size %zu\n",
> +					zone->name, i, zone->off,
> +					zone->buffer_size);
> +			continue;
> +		}
> +
> +		hdr = (struct psz_kmsg_header *)buf->data;
> +		if (hdr->magic != PSTORE_KMSG_HEADER_MAGIC) {
> +			pr_info("found invalid zone: %s: id %lu, off %lld, size %zu\n",
> +					zone->name, i, zone->off,
> +					zone->buffer_size);
> +			continue;
> +		}
> +
> +		/*
> +		 * we get the newest zone, and the next one must be the oldest
> +		 * or unused zone, because we do write one by one like a circle.
> +		 */
> +		if (hdr->time.tv_sec >= time.tv_sec) {
> +			time.tv_sec = hdr->time.tv_sec;
> +			cxt->kmsg_write_cnt = (i + 1) % cxt->kmsg_max_cnt;
> +		}
> +
> +		if (hdr->reason == KMSG_DUMP_OOPS)
> +			cxt->oops_counter =
> +				max(cxt->oops_counter, hdr->counter);
> +		else if (hdr->reason == KMSG_DUMP_PANIC)
> +			cxt->panic_counter =
> +				max(cxt->panic_counter, hdr->counter);
> +
> +		if (!atomic_read(&buf->datalen)) {
> +			pr_debug("found erased zone: %s: id %lu, off %lld, size %zu, datalen %d\n",
> +					zone->name, i, zone->off,
> +					zone->buffer_size,
> +					atomic_read(&buf->datalen));
> +			continue;
> +		}
> +
> +		if (!is_on_panic())
> +			zone->should_recover = true;
> +		pr_debug("found nice zone: %s: id %lu, off %lld, size %zu, datalen %d\n",
> +				zone->name, i, zone->off,
> +				zone->buffer_size, atomic_read(&buf->datalen));
> +	}
> +
> +	return 0;
> +}
> +
> +static int psz_kmsg_recover(struct psz_context *cxt)
> +{
> +	int ret;
> +
> +	if (!cxt->kpszs)
> +		return 0;
> +
> +	ret = psz_kmsg_recover_meta(cxt);
> +	if (ret)
> +		goto recover_fail;
> +
> +	ret = psz_kmsg_recover_data(cxt);
> +	if (ret)
> +		goto recover_fail;
> +
> +	return 0;
> +recover_fail:
> +	pr_debug("psz_recover_kmsg failed\n");
> +	return ret;
> +}
> +
> +/**
> + * psz_recovery() - recover data from storage
> + * @cxt: the context of pstore/zone
> + *
> + * recovery means reading data back from storage after rebooting
> + *
> + * Return: 0 on success, others on failure.
> + */
> +static inline int psz_recovery(struct psz_context *cxt)
> +{
> +	int ret = -EBUSY;
> +
> +	if (atomic_read(&cxt->recovered))
> +		return 0;
> +
> +	ret = psz_kmsg_recover(cxt);
> +	if (ret)
> +		goto recover_fail;
> +
> +	pr_debug("recover end!\n");
> +	atomic_set(&cxt->recovered, 1);
> +	return 0;
> +
> +recover_fail:
> +	pr_err("recover failed\n");
> +	return ret;
> +}
> +
> +static int psz_pstore_open(struct pstore_info *psi)
> +{
> +	struct psz_context *cxt = psi->data;
> +
> +	cxt->kmsg_read_cnt = 0;
> +	return 0;
> +}
> +
> +static inline bool psz_ok(struct pstore_zone *zone)
> +{
> +	if (zone && zone->buffer && buffer_datalen(zone))
> +		return true;
> +	return false;
> +}
> +
> +static inline int psz_kmsg_erase(struct psz_context *cxt,
> +		struct pstore_zone *zone, struct pstore_record *record)
> +{
> +	struct psz_buffer *buffer = zone->buffer;
> +	struct psz_kmsg_header *hdr =
> +		(struct psz_kmsg_header *)buffer->data;
> +
> +	if (unlikely(!psz_ok(zone)))
> +		return 0;
> +	/* this zone is already updated, no need to erase */
> +	if (record->count != hdr->counter)
> +		return 0;

These codes is to fix bug that user remove files on pstore filesystem
but kmsg zone is already updated and pstore/zone should not erase
zone. It work for oops and panic because the count number is increasing.
However, it's useless for other reason of kmsg. We can fix it after this
series.

> +
> +	atomic_set(&zone->buffer->datalen, 0);
> +	return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
> +}
> +
> +static int psz_pstore_erase(struct pstore_record *record)
> +{
> +	struct psz_context *cxt = record->psi->data;
> +
> +	switch (record->type) {
> +	case PSTORE_TYPE_DMESG:
> +		if (record->id >= cxt->kmsg_max_cnt)
> +			return -EINVAL;
> +		return psz_kmsg_erase(cxt, cxt->kpszs[record->id], record);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static void psz_write_kmsg_hdr(struct pstore_zone *zone,
> +		struct pstore_record *record)
> +{
> +	struct psz_context *cxt = record->psi->data;
> +	struct psz_buffer *buffer = zone->buffer;
> +	struct psz_kmsg_header *hdr =
> +		(struct psz_kmsg_header *)buffer->data;
> +
> +	hdr->magic = PSTORE_KMSG_HEADER_MAGIC;
> +	hdr->compressed = record->compressed;
> +	hdr->time.tv_sec = record->time.tv_sec;
> +	hdr->time.tv_nsec = record->time.tv_nsec;
> +	hdr->reason = record->reason;
> +	if (hdr->reason == KMSG_DUMP_OOPS)
> +		hdr->counter = ++cxt->oops_counter;
> +	else if (hdr->reason == KMSG_DUMP_PANIC)
> +		hdr->counter = ++cxt->panic_counter;
> +	else
> +		hdr->counter = 0;
> +}
> +
> +static inline int notrace psz_kmsg_write_record(struct psz_context *cxt,
> +		struct pstore_record *record)
> +{
> +	size_t size, hlen;
> +	struct pstore_zone *zone;
> +	unsigned int zonenum;
> +
> +	zonenum = cxt->kmsg_write_cnt;
> +	zone = cxt->kpszs[zonenum];
> +	if (unlikely(!zone))
> +		return -ENOSPC;
> +	cxt->kmsg_write_cnt = (zonenum + 1) % cxt->kmsg_max_cnt;
> +
> +	pr_debug("write %s to zone id %d\n", zone->name, zonenum);
> +	psz_write_kmsg_hdr(zone, record);
> +	hlen = sizeof(struct psz_kmsg_header);
> +	size = min_t(size_t, record->size, zone->buffer_size - hlen);
> +	return psz_zone_write(zone, FLUSH_ALL, record->buf, size, hlen);
> +}
> +
> +static int notrace psz_kmsg_write(struct psz_context *cxt,
> +		struct pstore_record *record)
> +{
> +	int ret;
> +
> +	/*
> +	 * Explicitly only take the first part of any new crash.
> +	 * If our buffer is larger than kmsg_bytes, this can never happen,
> +	 * and if our buffer is smaller than kmsg_bytes, we don't want the
> +	 * report split across multiple records.
> +	 */
> +	if (record->part != 1)
> +		return -ENOSPC;
> +
> +	if (!cxt->kpszs)
> +		return -ENOSPC;
> +
> +	ret = psz_kmsg_write_record(cxt, record);
> +	if (!ret) {
> +		pr_debug("try to flush other dirty zones\n");
> +		psz_flush_dirty_zones(cxt->kpszs, cxt->kmsg_max_cnt);
> +	}
> +
> +	/* always return 0 as we had handled it on buffer */
> +	return 0;
> +}
> +
> +static int notrace psz_pstore_write(struct pstore_record *record)
> +{
> +	struct psz_context *cxt = record->psi->data;
> +
> +	if (record->type == PSTORE_TYPE_DMESG &&
> +			record->reason == KMSG_DUMP_PANIC)
> +		atomic_set(&cxt->on_panic, 1);
> +
> +	switch (record->type) {
> +	case PSTORE_TYPE_DMESG:
> +		return psz_kmsg_write(cxt, record);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static struct pstore_zone *psz_read_next_zone(struct psz_context *cxt)
> +{
> +	struct pstore_zone *zone = NULL;
> +
> +	while (cxt->kmsg_read_cnt < cxt->kmsg_max_cnt) {
> +		zone = cxt->kpszs[cxt->kmsg_read_cnt++];
> +		if (psz_ok(zone))
> +			return zone;
> +	}
> +
> +	return NULL;
> +}
> +
> +static int psz_kmsg_read_hdr(struct pstore_zone *zone,
> +		struct pstore_record *record)
> +{
> +	struct psz_buffer *buffer = zone->buffer;
> +	struct psz_kmsg_header *hdr =
> +		(struct psz_kmsg_header *)buffer->data;
> +
> +	if (hdr->magic != PSTORE_KMSG_HEADER_MAGIC)
> +		return -EINVAL;
> +	record->compressed = hdr->compressed;
> +	record->time.tv_sec = hdr->time.tv_sec;
> +	record->time.tv_nsec = hdr->time.tv_nsec;
> +	record->reason = hdr->reason;
> +	record->count = hdr->counter;
> +	return 0;
> +}
> +
> +static ssize_t psz_kmsg_read(struct pstore_zone *zone,
> +		struct pstore_record *record)
> +{
> +	ssize_t size, hlen = 0;
> +
> +	size = buffer_datalen(zone);
> +	/* Clear and skip this kmsg dump record if it has no valid header */
> +	if (psz_kmsg_read_hdr(zone, record)) {
> +		atomic_set(&zone->buffer->datalen, 0);
> +		atomic_set(&zone->dirty, 0);
> +		return -ENOMSG;
> +	}
> +	size -= sizeof(struct psz_kmsg_header);
> +
> +	if (!record->compressed) {
> +		char *buf = kasprintf(GFP_KERNEL, "%s: Total %d times\n",
> +				      kmsg_dump_reason_str(record->reason),
> +				      record->count);
> +		hlen = strlen(buf);
> +		record->buf = krealloc(buf, hlen + size, GFP_KERNEL);
> +		if (!record->buf) {
> +			kfree(buf);
> +			return -ENOMEM;
> +		}
> +	} else {
> +		record->buf = kmalloc(size, GFP_KERNEL);
> +		if (!record->buf)
> +			return -ENOMEM;
> +	}
> +
> +	size = psz_zone_read(zone, record->buf + hlen, size,
> +			sizeof(struct psz_kmsg_header));
> +	if (unlikely(size < 0)) {
> +		kfree(record->buf);
> +		return -ENOMSG;
> +	}
> +
> +	return size + hlen;
> +}
> +
> +static ssize_t psz_pstore_read(struct pstore_record *record)
> +{
> +	struct psz_context *cxt = record->psi->data;
> +	ssize_t (*readop)(struct pstore_zone *zone,
> +			struct pstore_record *record);
> +	struct pstore_zone *zone;
> +	ssize_t ret;
> +
> +	/* before read, we must recover from storage */
> +	ret = psz_recovery(cxt);
> +	if (ret)
> +		return ret;
> +
> +next_zone:
> +	zone = psz_read_next_zone(cxt);
> +	if (!zone)
> +		return 0;
> +
> +	record->type = zone->type;
> +	switch (record->type) {
> +	case PSTORE_TYPE_DMESG:
> +		readop = psz_kmsg_read;
> +		record->id = cxt->kmsg_read_cnt - 1;
> +		break;
> +	default:
> +		goto next_zone;
> +	}
> +
> +	ret = readop(zone, record);
> +	if (ret == -ENOMSG)
> +		goto next_zone;
> +	return ret;
> +}
> +
> +static struct psz_context pstore_zone_cxt = {
> +	.pstore_zone_info_lock =
> +		__MUTEX_INITIALIZER(pstore_zone_cxt.pstore_zone_info_lock),
> +	.recovered = ATOMIC_INIT(0),
> +	.on_panic = ATOMIC_INIT(0),
> +	.pstore = {
> +		.owner = THIS_MODULE,
> +		.open = psz_pstore_open,
> +		.read = psz_pstore_read,
> +		.write = psz_pstore_write,
> +		.erase = psz_pstore_erase,
> +	},
> +};
> +
> +static void psz_free_zone(struct pstore_zone **pszone)
> +{
> +	struct pstore_zone *zone = *pszone;
> +
> +	if (!zone)
> +		return;
> +
> +	kfree(zone->buffer);
> +	kfree(zone);
> +	*pszone = NULL;
> +}
> +
> +static void psz_free_zones(struct pstore_zone ***pszones, unsigned int *cnt)
> +{
> +	struct pstore_zone **zones = *pszones;
> +
> +	if (!zones)
> +		return;
> +
> +	while (*cnt > 0) {
> +		(*cnt)--;
> +		psz_free_zone(&(zones[*cnt]));
> +	}
> +	kfree(zones);
> +	*pszones = NULL;
> +}
> +
> +static void psz_free_all_zones(struct psz_context *cxt)
> +{
> +	if (cxt->kpszs)
> +		psz_free_zones(&cxt->kpszs, &cxt->kmsg_max_cnt);
> +}
> +
> +static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
> +		loff_t *off, size_t size)
> +{
> +	struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
> +	struct pstore_zone *zone;
> +	const char *name = pstore_type_to_name(type);
> +
> +	if (!size)
> +		return NULL;
> +
> +	if (*off + size > info->total_size) {
> +		pr_err("no room for %s (0x%zx@...llx over 0x%lx)\n",
> +			name, size, *off, info->total_size);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	zone = kzalloc(sizeof(struct pstore_zone), GFP_KERNEL);
> +	if (!zone)
> +		return ERR_PTR(-ENOMEM);
> +
> +	zone->buffer = kmalloc(size, GFP_KERNEL);
> +	if (!zone->buffer) {
> +		kfree(zone);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +	memset(zone->buffer, 0xFF, size);
> +	zone->off = *off;
> +	zone->name = name;
> +	zone->type = type;
> +	zone->buffer_size = size - sizeof(struct psz_buffer);
> +	zone->buffer->sig = type ^ PSZ_SIG;
> +	atomic_set(&zone->dirty, 0);
> +	atomic_set(&zone->buffer->datalen, 0);
> +
> +	*off += size;
> +
> +	pr_debug("pszone %s: off 0x%llx, %zu header, %zu data\n", zone->name,
> +			zone->off, sizeof(*zone->buffer), zone->buffer_size);
> +	return zone;
> +}
> +
> +static struct pstore_zone **psz_init_zones(enum pstore_type_id type,
> +	loff_t *off, size_t total_size, ssize_t record_size,
> +	unsigned int *cnt)
> +{
> +	struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
> +	struct pstore_zone **zones, *zone;
> +	const char *name = pstore_type_to_name(type);
> +	int c, i;
> +
> +	*cnt = 0;
> +	if (!total_size || !record_size)
> +		return NULL;
> +
> +	if (*off + total_size > info->total_size) {
> +		pr_err("no room for zones %s (0x%zx@...llx over 0x%lx)\n",
> +			name, total_size, *off, info->total_size);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	c = total_size / record_size;
> +	zones = kcalloc(c, sizeof(*zones), GFP_KERNEL);
> +	if (!zones) {
> +		pr_err("allocate for zones %s failed\n", name);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +	memset(zones, 0, c * sizeof(*zones));
> +
> +	for (i = 0; i < c; i++) {
> +		zone = psz_init_zone(type, off, record_size);
> +		if (!zone || IS_ERR(zone)) {
> +			pr_err("initialize zones %s failed\n", name);
> +			psz_free_zones(&zones, &i);
> +			return (void *)zone;
> +		}
> +		zones[i] = zone;
> +	}
> +
> +	*cnt = c;
> +	return zones;
> +}
> +
> +static int psz_alloc_zones(struct psz_context *cxt)
> +{
> +	struct pstore_zone_info *info = cxt->pstore_zone_info;
> +	loff_t off = 0;
> +	int err;
> +	size_t size;
> +
> +	size = info->total_size;
> +	cxt->kpszs = psz_init_zones(PSTORE_TYPE_DMESG, &off, size,
> +			info->kmsg_size, &cxt->kmsg_max_cnt);
> +	if (IS_ERR(cxt->kpszs)) {
> +		err = PTR_ERR(cxt->kpszs);
> +		cxt->kpszs = NULL;
> +		goto fail_out;
> +	}
> +
> +	return 0;
> +fail_out:
> +	return err;
> +}
> +
> +/**
> + * register_pstore_zone() - register to pstore/zone
> + *
> + * @info: back-end driver information. See &struct pstore_zone_info.
> + *
> + * Only one back-end at one time.
> + *
> + * Return: 0 on success, others on failure.
> + */
> +int register_pstore_zone(struct pstore_zone_info *info)
> +{
> +	int err = -EINVAL;
> +	struct psz_context *cxt = &pstore_zone_cxt;
> +
> +	if (info->total_size < 4096) {
> +		pr_warn("total_size must be >= 4096\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!info->kmsg_size) {
> +		pr_warn("at least one record size must be non-zero\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!info->name || !info->name[0])
> +		return -EINVAL;
> +
> +#define check_size(name, size) {					\
> +		if (info->name > 0 && info->name < (size)) {		\
> +			pr_err(#name " must be over %d\n", (size));	\
> +			return -EINVAL;					\
> +		}							\
> +		if (info->name & (size - 1)) {				\
> +			pr_err(#name " must be a multiple of %d\n",	\
> +					(size));			\
> +			return -EINVAL;					\
> +		}							\
> +	}
> +
> +	check_size(total_size, 4096);
> +	check_size(kmsg_size, SECTOR_SIZE);
> +
> +#undef check_size
> +
> +	/*
> +	 * the @read and @write must be applied.
> +	 * if no @read, pstore may mount failed.
> +	 * if no @write, pstore do not support to remove record file.
> +	 */
> +	if (!info->read || !info->write) {
> +		pr_err("no valid general read/write interface\n");
> +		return -EINVAL;
> +	}
> +
> +	mutex_lock(&cxt->pstore_zone_info_lock);
> +	if (cxt->pstore_zone_info) {
> +		pr_warn("'%s' already loaded: ignoring '%s'\n",
> +				cxt->pstore_zone_info->name, info->name);
> +		mutex_unlock(&cxt->pstore_zone_info_lock);
> +		return -EBUSY;
> +	}
> +	cxt->pstore_zone_info = info;
> +
> +	pr_debug("register %s with properties:\n", info->name);
> +	pr_debug("\ttotal size : %ld Bytes\n", info->total_size);
> +	pr_debug("\tkmsg size : %ld Bytes\n", info->kmsg_size);
> +
> +	err = psz_alloc_zones(cxt);
> +	if (err) {
> +		pr_err("alloc zones failed\n");
> +		goto fail_out;
> +	}
> +
> +	if (info->kmsg_size) {
> +		cxt->pstore.bufsize = cxt->kpszs[0]->buffer_size -
> +			sizeof(struct psz_kmsg_header);
> +		cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
> +		if (!cxt->pstore.buf) {
> +			err = -ENOMEM;
> +			goto fail_free;
> +		}
> +	}
> +	cxt->pstore.data = cxt;
> +
> +	pr_info("registered %s as backend for", info->name);
> +	cxt->pstore.max_reason = info->max_reason;
> +	cxt->pstore.name = info->name;
> +	if (info->kmsg_size) {
> +		cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
> +		pr_cont(" kmsg(%s",
> +			kmsg_dump_reason_str(cxt->pstore.max_reason));
> +		if (cxt->pstore_zone_info->panic_write)
> +			pr_cont(",panic_write");
> +		pr_cont(")");
> +	}
> +	pr_cont("\n");
> +
> +	err = pstore_register(&cxt->pstore);
> +	if (err) {
> +		pr_err("registering with pstore failed\n");
> +		goto fail_free;
> +	}
> +	mutex_unlock(&pstore_zone_cxt.pstore_zone_info_lock);
> +
> +	return 0;
> +
> +fail_free:
> +	kfree(cxt->pstore.buf);
> +	cxt->pstore.buf = NULL;
> +	cxt->pstore.bufsize = 0;
> +	psz_free_all_zones(cxt);
> +fail_out:
> +	pstore_zone_cxt.pstore_zone_info = NULL;
> +	mutex_unlock(&pstore_zone_cxt.pstore_zone_info_lock);
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(register_pstore_zone);
> +
> +/**
> + * unregister_pstore_zone() - unregister to pstore/zone
> + *
> + * @info: back-end driver information. See struct pstore_zone_info.
> + */
> +void unregister_pstore_zone(struct pstore_zone_info *info)
> +{
> +	struct psz_context *cxt = &pstore_zone_cxt;
> +
> +	mutex_lock(&cxt->pstore_zone_info_lock);
> +	if (!cxt->pstore_zone_info) {
> +		mutex_unlock(&cxt->pstore_zone_info_lock);
> +		return;
> +	}
> +
> +	/* Stop incoming writes from pstore. */
> +	pstore_unregister(&cxt->pstore);
> +
> +	/* Clean up allocations. */
> +	kfree(cxt->pstore.buf);
> +	cxt->pstore.buf = NULL;
> +	cxt->pstore.bufsize = 0;
> +	cxt->pstore_zone_info = NULL;
> +
> +	psz_free_all_zones(cxt);
> +
> +	/* Clear counters and zone state. */
> +	cxt->oops_counter = 0;
> +	cxt->panic_counter = 0;
> +	atomic_set(&cxt->recovered, 0);
> +	atomic_set(&cxt->on_panic, 0);
> +
> +	mutex_unlock(&cxt->pstore_zone_info_lock);
> +}
> +EXPORT_SYMBOL_GPL(unregister_pstore_zone);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("WeiXiong Liao <liaoweixiong@...winnertech.com>");
> +MODULE_AUTHOR("Kees Cook <keescook@...omium.org>");
> +MODULE_DESCRIPTION("Storage Manager for pstore/blk");
> diff --git a/include/linux/pstore_zone.h b/include/linux/pstore_zone.h
> new file mode 100644
> index 000000000000..eb005d9ae40c
> --- /dev/null
> +++ b/include/linux/pstore_zone.h
> @@ -0,0 +1,44 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __PSTORE_ZONE_H_
> +#define __PSTORE_ZONE_H_
> +
> +#include <linux/types.h>
> +
> +typedef ssize_t (*pstore_zone_read_op)(char *, size_t, loff_t);
> +typedef ssize_t (*pstore_zone_write_op)(const char *, size_t, loff_t);
> +/**
> + * struct pstore_zone_info - pstore/zone back-end driver structure
> + *
> + * @owner:	Module which is responsible for this back-end driver.
> + * @name:	Name of the back-end driver.
> + * @total_size: The total size in bytes pstore/zone can use. It must be greater
> + *		than 4096 and be multiple of 4096.
> + * @kmsg_size:	The size of oops/panic zone. Zero means disabled, otherwise,
> + *		it must be multiple of SECTOR_SIZE(512 Bytes).
> + * @max_reason: Maximum kmsg dump reason to store.
> + * @read:	The general read operation. Both of the function parameters
> + *		@size and @offset are relative value to storage.
> + *		On success, the number of bytes should be returned, others
> + *		means error.
> + * @write:	The same as @read.
> + * @panic_write:The write operation only used for panic case. It's optional
> + *		if you do not care panic log. The parameters and return value
> + *		are the same as @read.
> + */
> +struct pstore_zone_info {
> +	struct module *owner;
> +	const char *name;
> +
> +	unsigned long total_size;
> +	unsigned long kmsg_size;
> +	int max_reason;
> +	pstore_zone_read_op read;
> +	pstore_zone_write_op write;
> +	pstore_zone_write_op panic_write;
> +};
> +
> +extern int register_pstore_zone(struct pstore_zone_info *info);
> +extern void unregister_pstore_zone(struct pstore_zone_info *info);
> +
> +#endif
> 

-- 
WeiXiong Liao

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