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Date:   Sat, 9 May 2020 12:38:23 +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>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-doc@...r.kernel.org, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 05/12] pstore/blk: Add support for pmsg frontend

hi Kees Cook,

On 2020/5/8 PM 2:39, Kees Cook wrote:
> From: WeiXiong Liao <liaoweixiong@...winnertech.com>
> 
> Add pmsg support to pstore/blk (through pstore/zone). To enable, pmsg_size
> must be greater than 0 and a multiple of 4096.
> 
> Signed-off-by: WeiXiong Liao <liaoweixiong@...winnertech.com>
> Link: https://lore.kernel.org/r/1585126506-18635-5-git-send-email-liaoweixiong@allwinnertech.com
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  fs/pstore/Kconfig           |  12 ++
>  fs/pstore/blk.c             |   9 ++
>  fs/pstore/zone.c            | 268 ++++++++++++++++++++++++++++++++++--
>  include/linux/pstore_zone.h |   2 +
>  4 files changed, 281 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
> index 92ba73bd0b62..f18cd126d83f 100644
> --- a/fs/pstore/Kconfig
> +++ b/fs/pstore/Kconfig
> @@ -224,3 +224,15 @@ config PSTORE_BLK_MAX_REASON
>  
>  	  NOTE that, both Kconfig and module parameters can configure
>  	  pstore/blk, but module parameters have priority over Kconfig.
> +
> +config PSTORE_BLK_PMSG_SIZE
> +	int "Size in Kbytes of pmsg to store"
> +	depends on PSTORE_BLK
> +	depends on PSTORE_PMSG
> +	default 64
> +	help
> +	  This just sets size of pmsg (pmsg_size) for pstore/blk. The size is
> +	  in KB and must be a multiple of 4.
> +
> +	  NOTE that, both Kconfig and module parameters can configure
> +	  pstore/blk, but module parameters have priority over Kconfig.
> diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
> index d1c3074aa128..401e5ba66a5f 100644
> --- a/fs/pstore/blk.c
> +++ b/fs/pstore/blk.c
> @@ -24,6 +24,14 @@ module_param(max_reason, int, 0400);
>  MODULE_PARM_DESC(max_reason,
>  		 "maximum reason for kmsg dump (default 2: Oops and Panic)");
>  
> +#if IS_ENABLED(CONFIG_PSTORE_PMSG)
> +static long pmsg_size = CONFIG_PSTORE_BLK_PMSG_SIZE;
> +#else
> +static long pmsg_size = -1;
> +#endif
> +module_param(pmsg_size, long, 0400);
> +MODULE_PARM_DESC(pmsg_size, "pmsg size in kbytes");
> +
>  /*
>   * blkdev - The block device to use.
>   *
> @@ -124,6 +132,7 @@ static int psblk_register_do(struct psblk_device *dev)
>  	}
>  
>  	verify_size(kmsg_size, 4096, dev->flags & PSTORE_FLAGS_DMESG);
> +	verify_size(pmsg_size, 4096, dev->flags & PSTORE_FLAGS_PMSG);
>  #undef verify_size
>  
>  	pstore_zone_info->total_size = dev->total_size;
> diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
> index 6c25c443c8e2..f472b06a6c14 100644
> --- a/fs/pstore/zone.c
> +++ b/fs/pstore/zone.c
> @@ -23,12 +23,14 @@
>   *
>   * @sig: signature to indicate header (PSZ_SIG xor PSZONE-type value)
>   * @datalen: length of data in @data
> + * @start: offset into @data where the beginning of the stored bytes begin
>   * @data: zone data.
>   */
>  struct psz_buffer {
>  #define PSZ_SIG (0x43474244) /* DBGC */
>  	uint32_t sig;
>  	atomic_t datalen;
> +	atomic_t start;
>  	uint8_t data[];
>  };
>  
> @@ -84,9 +86,11 @@ struct pstore_zone {
>   * struct psz_context - all about running state of pstore/zone
>   *
>   * @opszs: oops/panic storage zones
> + * @ppsz: pmsg storage zone
>   * @oops_max_cnt: max count of @opszs
>   * @oops_read_cnt: counter to read oops zone
>   * @oops_write_cnt: counter to write
> + * @pmsg_read_cnt: counter to read pmsg zone
>   * @oops_counter: counter to oops
>   * @panic_counter: counter to panic
>   * @recovered: whether finish recovering data from storage
> @@ -97,9 +101,11 @@ struct pstore_zone {
>   */
>  struct psz_context {
>  	struct pstore_zone **opszs;
> +	struct pstore_zone *ppsz;
>  	unsigned int oops_max_cnt;
>  	unsigned int oops_read_cnt;
>  	unsigned int oops_write_cnt;
> +	unsigned int pmsg_read_cnt;
>  	/*
>  	 * the counter should be recovered when recover.
>  	 * It records the oops/panic times after burning rather than booting.
> @@ -139,6 +145,11 @@ static inline int buffer_datalen(struct pstore_zone *zone)
>  	return atomic_read(&zone->buffer->datalen);
>  }
>  
> +static inline int buffer_start(struct pstore_zone *zone)
> +{
> +	return atomic_read(&zone->buffer->start);
> +}
> +
>  static inline bool is_on_panic(void)
>  {
>  	struct psz_context *cxt = &psz_cxt;
> @@ -146,10 +157,10 @@ static inline bool is_on_panic(void)
>  	return atomic_read(&cxt->on_panic);
>  }
>  
> -static ssize_t psz_zone_read(struct pstore_zone *zone, char *buf,
> +static ssize_t psz_zone_read_buffer(struct pstore_zone *zone, char *buf,
>  		size_t len, unsigned long off)
>  {
> -	if (!buf || !zone->buffer)
> +	if (!buf || !zone || !zone->buffer)
>  		return -EINVAL;
>  	if (off > zone->buffer_size)
>  		return -EINVAL;
> @@ -158,6 +169,18 @@ static ssize_t psz_zone_read(struct pstore_zone *zone, char *buf,
>  	return len;
>  }
>  
> +static int psz_zone_read_oldbuf(struct pstore_zone *zone, char *buf,
> +		size_t len, unsigned long off)
> +{
> +	if (!buf || !zone || !zone->oldbuf)
> +		return -EINVAL;
> +	if (off > zone->buffer_size)
> +		return -EINVAL;
> +	len = min_t(size_t, len, zone->buffer_size - off);
> +	memcpy(buf, zone->oldbuf->data + off, len);
> +	return 0;
> +}
> +
>  static int psz_zone_write(struct pstore_zone *zone,
>  		enum psz_flush_mode flush_mode, const char *buf,
>  		size_t len, unsigned long off)
> @@ -413,6 +436,93 @@ static int psz_recover_oops(struct psz_context *cxt)
>  	return ret;
>  }
>  
> +static int psz_recover_zone(struct psz_context *cxt, struct pstore_zone *zone)
> +{
> +	struct pstore_zone_info *info = cxt->pstore_zone_info;
> +	struct psz_buffer *oldbuf, tmpbuf;
> +	int ret = 0;
> +	char *buf;
> +	ssize_t rcnt, len, start, off;
> +
> +	if (!zone || zone->oldbuf)
> +		return 0;
> +
> +	if (is_on_panic()) {
> +		/* save data as much as possible */
> +		psz_flush_dirty_zone(zone);
> +		return 0;
> +	}
> +
> +	if (unlikely(!info->read))
> +		return -EINVAL;
> +
> +	len = sizeof(struct psz_buffer);
> +	rcnt = info->read((char *)&tmpbuf, len, zone->off);
> +	if (rcnt != len) {
> +		pr_debug("read zone %s failed\n", zone->name);
> +		return (int)rcnt < 0 ? (int)rcnt : -EIO;
> +	}
> +
> +	if (tmpbuf.sig != zone->buffer->sig) {
> +		pr_debug("no valid data in zone %s\n", zone->name);
> +		return 0;
> +	}
> +
> +	if (zone->buffer_size < atomic_read(&tmpbuf.datalen) ||
> +		zone->buffer_size < atomic_read(&tmpbuf.start)) {
> +		pr_info("found overtop zone: %s: off %lld, size %zu\n",
> +				zone->name, zone->off, zone->buffer_size);
> +		/* just keep going */
> +		return 0;
> +	}
> +
> +	if (!atomic_read(&tmpbuf.datalen)) {
> +		pr_debug("found erased zone: %s: off %lld, size %zu, datalen %d\n",
> +				zone->name, zone->off, zone->buffer_size,
> +				atomic_read(&tmpbuf.datalen));
> +		return 0;
> +	}
> +
> +	pr_debug("found nice zone: %s: off %lld, size %zu, datalen %d\n",
> +			zone->name, zone->off, zone->buffer_size,
> +			atomic_read(&tmpbuf.datalen));
> +
> +	len = atomic_read(&tmpbuf.datalen) + sizeof(*oldbuf);
> +	oldbuf = kzalloc(len, GFP_KERNEL);
> +	if (!oldbuf)
> +		return -ENOMEM;
> +
> +	memcpy(oldbuf, &tmpbuf, sizeof(*oldbuf));
> +	buf = (char *)oldbuf + sizeof(*oldbuf);
> +	len = atomic_read(&oldbuf->datalen);
> +	start = atomic_read(&oldbuf->start);
> +	off = zone->off + sizeof(*oldbuf);
> +
> +	/* get part of data */
> +	rcnt = info->read(buf, len - start, off + start);
> +	if (rcnt != len - start) {
> +		pr_err("read zone %s failed\n", zone->name);
> +		ret = (int)rcnt < 0 ? (int)rcnt : -EIO;
> +		goto free_oldbuf;
> +	}
> +
> +	/* get the rest of data */
> +	rcnt = info->read(buf + len - start, start, off);
> +	if (rcnt != start) {
> +		pr_err("read zone %s failed\n", zone->name);
> +		ret = (int)rcnt < 0 ? (int)rcnt : -EIO;
> +		goto free_oldbuf;
> +	}
> +
> +	zone->oldbuf = oldbuf;
> +	psz_flush_dirty_zone(zone);
> +	return 0;
> +
> +free_oldbuf:
> +	kfree(oldbuf);
> +	return ret;
> +}
> +
>  /**
>   * psz_recovery() - recover data from storage
>   * @cxt: the context of pstore/zone
> @@ -432,6 +542,10 @@ static inline int psz_recovery(struct psz_context *cxt)
>  	if (ret)
>  		goto recover_fail;
>  
> +	ret = psz_recover_zone(cxt, cxt->ppsz);
> +	if (ret)
> +		goto recover_fail;
> +
>  	pr_debug("recover end!\n");
>  	atomic_set(&cxt->recovered, 1);
>  	return 0;
> @@ -446,9 +560,17 @@ static int psz_pstore_open(struct pstore_info *psi)
>  	struct psz_context *cxt = psi->data;
>  
>  	cxt->oops_read_cnt = 0;
> +	cxt->pmsg_read_cnt = 0;
>  	return 0;
>  }
>  
> +static inline bool psz_old_ok(struct pstore_zone *zone)
> +{
> +	if (zone && zone->oldbuf && atomic_read(&zone->oldbuf->datalen))
> +		return true;
> +	return false;
> +}
> +
>  static inline bool psz_ok(struct pstore_zone *zone)
>  {
>  	if (zone && zone->buffer && buffer_datalen(zone))
> @@ -473,6 +595,25 @@ static inline int psz_oops_erase(struct psz_context *cxt,
>  	return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
>  }
>  
> +static inline int psz_record_erase(struct psz_context *cxt,
> +		struct pstore_zone *zone)
> +{
> +	if (unlikely(!psz_old_ok(zone)))
> +		return 0;
> +
> +	kfree(zone->oldbuf);
> +	zone->oldbuf = NULL;
> +	/*
> +	 * if there are new data in zone buffer, that means the old data
> +	 * are already invalid. It is no need to flush 0 (erase) to
> +	 * block device.
> +	 */
> +	if (!buffer_datalen(zone))
> +		return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
> +	psz_flush_dirty_zone(zone);
> +	return 0;
> +}
> +
>  static int psz_pstore_erase(struct pstore_record *record)
>  {
>  	struct psz_context *cxt = record->psi->data;
> @@ -482,6 +623,8 @@ static int psz_pstore_erase(struct pstore_record *record)
>  		if (record->id >= cxt->oops_max_cnt)
>  			return -EINVAL;
>  		return psz_oops_erase(cxt, cxt->opszs[record->id], record);
> +	case PSTORE_TYPE_PMSG:
> +		return psz_record_erase(cxt, cxt->ppsz);
>  	default:
>  		return -EINVAL;
>  	}
> @@ -502,8 +645,10 @@ static void psz_write_kmsg_hdr(struct pstore_zone *zone,
>  	hdr->reason = record->reason;
>  	if (hdr->reason == KMSG_DUMP_OOPS)
>  		hdr->counter = ++cxt->oops_counter;
> -	else
> +	else if (hdr->reason == KMSG_DUMP_PANIC)
>  		hdr->counter = ++cxt->panic_counter;
> +	else
> +		hdr->counter = 0;
>  }
>  
>  static inline int notrace psz_oops_write_record(struct psz_context *cxt,
> @@ -553,6 +698,53 @@ static int notrace psz_oops_write(struct psz_context *cxt,

I think we should also try to flush pmsg zone if it's dirty in case of panic
and lost data.

@@ -690,8 +690,9 @@ static int notrace psz_oops_write(struct psz_context
*cxt,

        ret = psz_oops_write_record(cxt, record);
        if (!ret) {
-               pr_debug("try to flush other dirty oops zones\n");
+               pr_debug("try to flush other dirty zones\n");
                psz_flush_dirty_zones(cxt->opszs, cxt->oops_max_cnt);
+               psz_flush_dirty_zone(cxt->ppsz);
        }

        /* always return 0 as we had handled it on buffer */

>  	return 0;
>  }
>  
> +static int notrace psz_record_write(struct pstore_zone *zone,
> +		struct pstore_record *record)
> +{
> +	size_t start, rem;
> +	int cnt = record->size;
> +	bool is_full_data = false;
> +	char *buf = record->buf;
> +
> +	if (!zone || !record)
> +		return -ENOSPC;
> +
> +	if (atomic_read(&zone->buffer->datalen) >= zone->buffer_size)
> +		is_full_data = true;
> +
> +	if (unlikely(cnt > zone->buffer_size)) {
> +		buf += cnt - zone->buffer_size;
> +		cnt = zone->buffer_size;
> +	}
> +
> +	start = buffer_start(zone);
> +	rem = zone->buffer_size - start;
> +	if (unlikely(rem < cnt)) {
> +		psz_zone_write(zone, FLUSH_PART, buf, rem, start);
> +		buf += rem;
> +		cnt -= rem;
> +		start = 0;
> +		is_full_data = true;
> +	}
> +
> +	atomic_set(&zone->buffer->start, cnt + start);
> +	psz_zone_write(zone, FLUSH_PART, buf, cnt, start);
> +
> +	/**
> +	 * psz_zone_write will set datalen as start + cnt.
> +	 * It work if actual data length lesser than buffer size.
> +	 * If data length greater than buffer size, pmsg will rewrite to
> +	 * beginning of zone, which make buffer->datalen wrongly.
> +	 * So we should reset datalen as buffer size once actual data length
> +	 * greater than buffer size.
> +	 */
> +	if (is_full_data) {
> +		atomic_set(&zone->buffer->datalen, zone->buffer_size);
> +		psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
> +	}
> +	return 0;
> +}
> +
>  static int notrace psz_pstore_write(struct pstore_record *record)
>  {
>  	struct psz_context *cxt = record->psi->data;
> @@ -564,6 +756,8 @@ static int notrace psz_pstore_write(struct pstore_record *record)
>  	switch (record->type) {
>  	case PSTORE_TYPE_DMESG:
>  		return psz_oops_write(cxt, record);
> +	case PSTORE_TYPE_PMSG:
> +		return psz_record_write(cxt->ppsz, record);
>  	default:
>  		return -EINVAL;
>  	}
> @@ -579,6 +773,13 @@ static struct pstore_zone *psz_read_next_zone(struct psz_context *cxt)
>  			return zone;
>  	}
>  
> +	if (cxt->pmsg_read_cnt == 0) {
> +		cxt->pmsg_read_cnt++;
> +		zone = cxt->ppsz;
> +		if (psz_old_ok(zone))
> +			return zone;
> +	}
> +
>  	return NULL;
>  }
>  
> @@ -629,7 +830,7 @@ static ssize_t psz_oops_read(struct pstore_zone *zone,
>  			return -ENOMEM;
>  	}
>  
> -	size = psz_zone_read(zone, record->buf + hlen, size,
> +	size = psz_zone_read_buffer(zone, record->buf + hlen, size,
>  			sizeof(struct psz_oops_header) < 0);
>  	if (unlikely(size < 0)) {
>  		kfree(record->buf);
> @@ -639,6 +840,32 @@ static ssize_t psz_oops_read(struct pstore_zone *zone,
>  	return size + hlen;
>  }
>  
> +static ssize_t psz_record_read(struct pstore_zone *zone,
> +		struct pstore_record *record)
> +{
> +	size_t len;
> +	struct psz_buffer *buf;
> +
> +	if (!zone || !record)
> +		return -ENOSPC;
> +
> +	buf = (struct psz_buffer *)zone->oldbuf;
> +	if (!buf)
> +		return -ENOMSG;
> +
> +	len = atomic_read(&buf->datalen);
> +	record->buf = kmalloc(len, GFP_KERNEL);
> +	if (!record->buf)
> +		return -ENOMEM;
> +
> +	if (unlikely(psz_zone_read_oldbuf(zone, record->buf, len, 0))) {
> +		kfree(record->buf);
> +		return -ENOMSG;
> +	}
> +
> +	return len;
> +}
> +
>  static ssize_t psz_pstore_read(struct pstore_record *record)
>  {
>  	struct psz_context *cxt = record->psi->data;
> @@ -663,6 +890,9 @@ static ssize_t psz_pstore_read(struct pstore_record *record)
>  		readop = psz_oops_read;
>  		record->id = cxt->oops_read_cnt - 1;
>  		break;
> +	case PSTORE_TYPE_PMSG:
> +		readop = psz_record_read;
> +		break;
>  	default:
>  		goto next_zone;
>  	}
> @@ -718,8 +948,10 @@ static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
>  	zone->type = type;
>  	zone->buffer_size = size - sizeof(struct psz_buffer);
>  	zone->buffer->sig = type ^ PSZ_SIG;
> +	zone->oldbuf = NULL;
>  	atomic_set(&zone->dirty, 0);
>  	atomic_set(&zone->buffer->datalen, 0);
> +	atomic_set(&zone->buffer->start, 0);
>  
>  	*off += size;
>  
> @@ -803,6 +1035,8 @@ static void psz_free_all_zones(struct psz_context *cxt)
>  {
>  	if (cxt->opszs)
>  		psz_free_zones(&cxt->opszs, &cxt->oops_max_cnt);
> +	if (cxt->ppsz)
> +		psz_free_zone(&cxt->ppsz);
>  }
>  
>  static int psz_alloc_zones(struct psz_context *cxt)
> @@ -810,18 +1044,26 @@ 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_t off_size = 0;
>  
> -	size = info->total_size;
> -	cxt->opszs = psz_init_zones(PSTORE_TYPE_DMESG, &off, size,
> +	off_size += info->pmsg_size;
> +	cxt->ppsz = psz_init_zone(PSTORE_TYPE_PMSG, &off, info->pmsg_size);
> +	if (IS_ERR(cxt->ppsz)) {
> +		err = PTR_ERR(cxt->ppsz);
> +		goto free_out;
> +	}
> +
> +	cxt->opszs = psz_init_zones(PSTORE_TYPE_DMESG, &off,
> +			info->total_size - off_size,
>  			info->kmsg_size, &cxt->oops_max_cnt);
>  	if (IS_ERR(cxt->opszs)) {
>  		err = PTR_ERR(cxt->opszs);
> -		goto fail_out;
> +		goto free_out;
>  	}
>  
>  	return 0;
> -fail_out:
> +free_out:
> +	psz_free_all_zones(cxt);
>  	return err;
>  }
>  
> @@ -844,7 +1086,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
>  		return -EINVAL;
>  	}
>  
> -	if (!info->kmsg_size) {
> +	if (!info->kmsg_size && !info->pmsg_size) {
>  		pr_warn("at least one of the records be non-zero\n");
>  		return -EINVAL;
>  	}
> @@ -871,6 +1113,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
>  
>  	check_size(total_size, 4096);
>  	check_size(kmsg_size, SECTOR_SIZE);
> +	check_size(pmsg_size, SECTOR_SIZE);
>  
>  #undef check_size
>  
> @@ -897,6 +1140,7 @@ int register_pstore_zone(struct 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("\toops size : %ld Bytes\n", info->kmsg_size);
> +	pr_debug("\tpmsg size : %ld Bytes\n", info->pmsg_size);
>  
>  	err = psz_alloc_zones(cxt);
>  	if (err) {
> @@ -925,6 +1169,10 @@ int register_pstore_zone(struct pstore_zone_info *info)
>  			pr_cont(",panic_write");
>  		pr_cont(")");
>  	}
> +	if (info->pmsg_size) {
> +		cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
> +		pr_cont(" pmsg");
> +	}
>  	pr_cont("\n");
>  
>  	err = pstore_register(&cxt->pstore);
> diff --git a/include/linux/pstore_zone.h b/include/linux/pstore_zone.h
> index a6a79ff1351b..39c2cb944123 100644
> --- a/include/linux/pstore_zone.h
> +++ b/include/linux/pstore_zone.h
> @@ -17,6 +17,7 @@ typedef ssize_t (*psz_write_op)(const char *, size_t, loff_t);
>   * @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.
> + * @pmsg_size:	The size of pmsg zone which is the same as @kmsg_size.
>   * @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
> @@ -33,6 +34,7 @@ struct pstore_zone_info {
>  	unsigned long total_size;
>  	unsigned long kmsg_size;
>  	int max_reason;
> +	unsigned long pmsg_size;
>  	psz_read_op read;
>  	psz_write_op write;
>  	psz_write_op panic_write;
> 

-- 
WeiXiong Liao

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