Re: [RFC v5 3/4] pstore/blk: support pmsg for pstore block

[Kees Cook <keescook@chromium.org>]

On Mon, Jan 7, 2019 at 4:01 AM liaoweixiong
<liaoweixiong@allwinnertech.com> wrote:
>
> To enable pmsg, just set pmsg_size when block device register blkzone.

At first pass, this looks like a reasonable extension of blkzone. Is
it possible to add console, ftrace, etc, too?

-Kees

>
> Signed-off-by: liaoweixiong <liaoweixiong@allwinnertech.com>
> ---
>  fs/pstore/blkzone.c        | 254 +++++++++++++++++++++++++++++++++++++++++----
>  include/linux/pstore_blk.h |   1 +
>  2 files changed, 233 insertions(+), 22 deletions(-)
>
> diff --git a/fs/pstore/blkzone.c b/fs/pstore/blkzone.c
> index e1b7f26..157f1cfd 100644
> --- a/fs/pstore/blkzone.c
> +++ b/fs/pstore/blkzone.c
> @@ -32,12 +32,14 @@
>   *
>   * @sig: signature to indicate header (BLK_SIG xor BLKZONE-type value)
>   * @datalen: length of data in @data
> + * @start: offset into @data where the beginning of the stored bytes begin
>   * @data: zone data.
>   */
>  struct blkz_buffer {
>  #define BLK_SIG (0x43474244) /* DBGC */
>         uint32_t sig;
>         atomic_t datalen;
> +       atomic_t start;
>         uint8_t data[0];
>  };
>
> @@ -70,6 +72,9 @@ struct blkz_dmesg_header {
>   *     frontent name for this zone
>   * @buffer:
>   *     pointer to data buffer managed by this zone
> + * @oldbuf:
> + *     pointer to old data buffer. It is used for single zone such as pmsg,
> + *     saving the old buffer.
>   * @buffer_size:
>   *     bytes in @buffer->data
>   * @should_recover:
> @@ -83,6 +88,7 @@ struct blkz_zone {
>         enum pstore_type_id type;
>
>         struct blkz_buffer *buffer;
> +       struct blkz_buffer *oldbuf;
>         size_t buffer_size;
>         bool should_recover;
>         atomic_t dirty;
> @@ -90,8 +96,10 @@ struct blkz_zone {
>
>  struct blkoops_context {
>         struct blkz_zone **dbzs;        /* dmesg block zones */
> +       struct blkz_zone *pbz;          /* Pmsg block zone */
>         unsigned int dmesg_max_cnt;
>         unsigned int dmesg_read_cnt;
> +       unsigned int pmsg_read_cnt;
>         unsigned int dmesg_write_cnt;
>         /**
>          * the counter should be recovered when do recovery
> @@ -125,6 +133,11 @@ static inline int buffer_datalen(struct blkz_zone *zone)
>         return atomic_read(&zone->buffer->datalen);
>  }
>
> +static inline int buffer_start(struct blkz_zone *zone)
> +{
> +       return atomic_read(&zone->buffer->start);
> +}
> +
>  static inline bool is_on_panic(void)
>  {
>         struct blkoops_context *cxt = &blkz_cxt;
> @@ -394,6 +407,72 @@ static int blkz_recover_dmesg(struct blkoops_context *cxt)
>         return ret;
>  }
>
> +static int blkz_recover_pmsg(struct blkoops_context *cxt)
> +{
> +       struct blkz_info *info = cxt->bzinfo;
> +       struct blkz_buffer *oldbuf;
> +       struct blkz_zone *zone = NULL;
> +       ssize_t (*readop)(char *buf, size_t bytes, loff_t pos);
> +       int ret = 0;
> +       ssize_t rcnt, len;
> +
> +       zone = cxt->pbz;
> +       if (!zone || zone->oldbuf)
> +               return 0;
> +
> +       if (is_on_panic())
> +               goto out;
> +
> +       readop = info->read;
> +       if (unlikely(!readop))
> +               return -EINVAL;
> +
> +       len = zone->buffer_size + sizeof(*oldbuf);
> +       oldbuf = kzalloc(len, GFP_KERNEL);
> +       if (!oldbuf)
> +               return -ENOMEM;
> +
> +       rcnt = readop((char *)oldbuf, len, zone->off);
> +       if (rcnt != len) {
> +               pr_debug("recovery pmsg failed\n");
> +               ret = (int)rcnt < 0 ? (int)rcnt : -EIO;
> +               goto free_oldbuf;
> +       }
> +
> +       if (oldbuf->sig != zone->buffer->sig) {
> +               pr_debug("no valid data in zone %s\n", zone->name);
> +               goto free_oldbuf;
> +       }
> +
> +       if (zone->buffer_size < atomic_read(&oldbuf->datalen) ||
> +               zone->buffer_size < atomic_read(&oldbuf->start)) {
> +               pr_info("found overtop zone: %s: off %lu, size %zu\n",
> +                               zone->name, zone->off, zone->buffer_size);
> +               goto free_oldbuf;
> +       }
> +
> +       if (!atomic_read(&oldbuf->datalen)) {
> +               pr_debug("found erased zone: %s: id 0, off %lu, size %zu, datalen %d\n",
> +                               zone->name, zone->off, zone->buffer_size,
> +                               atomic_read(&oldbuf->datalen));
> +               kfree(oldbuf);
> +               goto out;
> +       }
> +
> +       pr_debug("found nice zone: %s: id 0, off %lu, size %zu, datalen %d\n",
> +                       zone->name, zone->off, zone->buffer_size,
> +                       atomic_read(&oldbuf->datalen));
> +       zone->oldbuf = oldbuf;
> +out:
> +       if (atomic_read(&zone->dirty))
> +               blkz_zone_write(zone, FLUSH_ALL, NULL, buffer_datalen(zone), 0);
> +       return 0;
> +
> +free_oldbuf:
> +       kfree(oldbuf);
> +       return ret;
> +}
> +
>  static inline int blkz_recovery(struct blkoops_context *cxt)
>  {
>         int ret = -EBUSY;
> @@ -408,6 +487,10 @@ static inline int blkz_recovery(struct blkoops_context *cxt)
>         if (ret)
>                 goto recover_fail;
>
> +       ret = blkz_recover_pmsg(cxt);
> +       if (ret)
> +               goto recover_fail;
> +
>         atomic_set(&cxt->recovery, 1);
>         pr_debug("recover end!\n");
>         return 0;
> @@ -425,11 +508,18 @@ static int blkoops_pstore_open(struct pstore_info *psi)
>         return 0;
>  }
>
> +static inline bool blkz_old_ok(struct blkz_zone *zone)
> +{
> +       if (zone && zone->oldbuf && atomic_read(&zone->oldbuf->datalen))
> +               return true;
> +       return false;
> +}
> +
>  static inline bool blkz_ok(struct blkz_zone *zone)
>  {
> -       if (!zone || !zone->buffer || !buffer_datalen(zone))
> -               return false;
> -       return true;
> +       if (zone && zone->buffer && buffer_datalen(zone))
> +               return true;
> +       return false;
>  }
>
>  static int blkoops_pstore_erase(struct pstore_record *record)
> @@ -443,13 +533,29 @@ static int blkoops_pstore_erase(struct pstore_record *record)
>          */
>         blkz_recovery(cxt);
>
> -       if (record->type == PSTORE_TYPE_DMESG)
> +       if (record->type == PSTORE_TYPE_DMESG) {
>                 zone = cxt->dbzs[record->id];
> -       if (!blkz_ok(zone))
> -               return 0;
> +               if (unlikely(!blkz_ok(zone)))
> +                       return 0;
>
> -       atomic_set(&zone->buffer->datalen, 0);
> -       return blkz_zone_write(zone, FLUSH_META, NULL, 0, 0);
> +               atomic_set(&zone->buffer->datalen, 0);
> +               return blkz_zone_write(zone, FLUSH_META, NULL, 0, 0);
> +       } else if (record->type == PSTORE_TYPE_PMSG) {
> +               zone = cxt->pbz;
> +               if (unlikely(!blkz_old_ok(zone)))
> +                       return 0;
> +
> +               kfree(zone->oldbuf);
> +               zone->oldbuf = NULL;
> +               /**
> +                * if there is new data in zone buffer, there is no need to
> +                * flush 0 (erase) to block device
> +                */
> +               if (buffer_datalen(zone))
> +                       return 0;
> +               return blkz_zone_write(zone, FLUSH_META, NULL, 0, 0);
> +       }
> +       return -EINVAL;
>  }
>
>  static void blkoops_write_kmsg_hdr(struct blkz_zone *zone,
> @@ -467,8 +573,10 @@ static void blkoops_write_kmsg_hdr(struct blkz_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 int notrace blkz_dmesg_write(struct blkoops_context *cxt,
> @@ -518,6 +626,55 @@ static int notrace blkz_dmesg_write(struct blkoops_context *cxt,
>         return 0;
>  }
>
> +static int notrace blkz_pmsg_write(struct blkoops_context *cxt,
> +               struct pstore_record *record)
> +{
> +       struct blkz_zone *zone;
> +       size_t start, rem;
> +       int cnt = record->size;
> +       bool is_full_data = false;
> +       char *buf = record->buf;
> +
> +       zone = cxt->pbz;
> +       if (!zone)
> +               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)) {
> +               blkz_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);
> +       blkz_zone_write(zone, FLUSH_PART, buf, cnt, start);
> +
> +       /**
> +        * blkz_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);
> +               blkz_zone_write(zone, FLUSH_META, NULL, 0, 0);
> +       }
> +       return 0;
> +}
> +
>  static int notrace blkoops_pstore_write(struct pstore_record *record)
>  {
>         struct blkoops_context *cxt = record->psi->data;
> @@ -535,6 +692,8 @@ static int notrace blkoops_pstore_write(struct pstore_record *record)
>         switch (record->type) {
>         case PSTORE_TYPE_DMESG:
>                 return blkz_dmesg_write(cxt, record);
> +       case PSTORE_TYPE_PMSG:
> +               return blkz_pmsg_write(cxt, record);
>         default:
>                 return -EINVAL;
>         }
> @@ -551,6 +710,13 @@ static struct blkz_zone *blkz_read_next_zone(struct blkoops_context *cxt)
>                         return zone;
>         }
>
> +       if (cxt->pmsg_read_cnt == 0) {
> +               cxt->pmsg_read_cnt++;
> +               zone = cxt->pbz;
> +               if (blkz_old_ok(zone))
> +                       return zone;
> +       }
> +
>         return NULL;
>  }
>
> @@ -589,7 +755,8 @@ static ssize_t blkz_dmesg_read(struct blkz_zone *zone,
>                 char *buf = kasprintf(GFP_KERNEL,
>                                 "blkoops: %s: Total %d times\n",
>                                 record->reason == KMSG_DUMP_OOPS ? "Oops" :
> -                               "Panic", record->count);
> +                               record->reason == KMSG_DUMP_PANIC ? "Panic" :
> +                               "Unknown", record->count);
>                 hlen = strlen(buf);
>                 record->buf = krealloc(buf, hlen + size, GFP_KERNEL);
>                 if (!record->buf) {
> @@ -611,6 +778,29 @@ static ssize_t blkz_dmesg_read(struct blkz_zone *zone,
>         return size + hlen;
>  }
>
> +static ssize_t blkz_pmsg_read(struct blkz_zone *zone,
> +               struct pstore_record *record)
> +{
> +       size_t size, start;
> +       struct blkz_buffer *buf;
> +
> +       buf = (struct blkz_buffer *)zone->oldbuf;
> +       if (!buf)
> +               return READ_NEXT_ZONE;
> +
> +       size = atomic_read(&buf->datalen);
> +       start = atomic_read(&buf->start);
> +
> +       record->buf = kmalloc(size, GFP_KERNEL);
> +       if (!record->buf)
> +               return -ENOMEM;
> +
> +       memcpy(record->buf, buf->data + start, size - start);
> +       memcpy(record->buf + size - start, buf->data, start);
> +
> +       return size;
> +}
> +
>  static ssize_t blkoops_pstore_read(struct pstore_record *record)
>  {
>         struct blkoops_context *cxt = record->psi->data;
> @@ -642,6 +832,9 @@ static ssize_t blkoops_pstore_read(struct pstore_record *record)
>                 blkz_read = blkz_dmesg_read;
>                 record->id = cxt->dmesg_read_cnt - 1;
>                 break;
> +       case PSTORE_TYPE_PMSG:
> +               blkz_read = blkz_pmsg_read;
> +               break;
>         default:
>                 goto next_zone;
>         }
> @@ -754,8 +947,10 @@ static struct blkz_zone *blkz_init_zone(enum pstore_type_id type,
>         zone->type = type;
>         zone->buffer_size = size - sizeof(struct blkz_buffer);
>         zone->buffer->sig = type ^ BLK_SIG;
> +       zone->oldbuf = NULL;
>         atomic_set(&zone->dirty, 0);
>         atomic_set(&zone->buffer->datalen, 0);
> +       atomic_set(&zone->buffer->start, 0);
>
>         *off += size;
>
> @@ -837,7 +1032,7 @@ static int blkz_cut_zones(struct blkoops_context *cxt)
>         int err;
>         size_t size;
>
> -       size = info->part_size;
> +       size = info->part_size - info->pmsg_size;
>         cxt->dbzs = blkz_init_zones(PSTORE_TYPE_DMESG, &off, size,
>                         info->dmesg_size, &cxt->dmesg_max_cnt);
>         if (IS_ERR(cxt->dbzs)) {
> @@ -845,7 +1040,16 @@ static int blkz_cut_zones(struct blkoops_context *cxt)
>                 goto fail_out;
>         }
>
> +       size = info->pmsg_size;
> +       cxt->pbz = blkz_init_zone(PSTORE_TYPE_PMSG, &off, size);
> +       if (IS_ERR(cxt->pbz)) {
> +               err = PTR_ERR(cxt->pbz);
> +               goto free_dmesg_zones;
> +       }
> +
>         return 0;
> +free_dmesg_zones:
> +       blkz_free_zones(&cxt->dbzs, &cxt->dmesg_max_cnt);
>  fail_out:
>         return err;
>  }
> @@ -856,7 +1060,7 @@ int blkz_register(struct blkz_info *info)
>         struct blkoops_context *cxt = &blkz_cxt;
>         struct module *owner = info->owner;
>
> -       if (!info->part_size || !info->dmesg_size) {
> +       if (!info->part_size || (!info->dmesg_size && !info->pmsg_size)) {
>                 pr_warn("The memory size and the dmesg size must be non-zero\n");
>                 return -EINVAL;
>         }
> @@ -876,6 +1080,7 @@ int blkz_register(struct blkz_info *info)
>
>         check_size(part_size, 4096 - 1);
>         check_size(dmesg_size, SECTOR_SIZE - 1);
> +       check_size(pmsg_size, SECTOR_SIZE - 1);
>
>  #undef check_size
>
> @@ -902,16 +1107,20 @@ int blkz_register(struct blkz_info *info)
>                 goto fail_out;
>         }
>
> -       cxt->pstore.bufsize = cxt->dbzs[0]->buffer_size -
> +       if (info->dmesg_size) {
> +               cxt->pstore.bufsize = cxt->dbzs[0]->buffer_size -
>                         sizeof(struct blkz_dmesg_header);
> -       cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
> -       if (!cxt->pstore.buf) {
> -               pr_err("cannot allocate pstore crash dump buffer\n");
> -               err = -ENOMEM;
> -               goto fail_out;
> +               cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
> +               if (!cxt->pstore.buf) {
> +                       err = -ENOMEM;
> +                       goto fail_out;
> +               }
>         }
>         cxt->pstore.data = cxt;
> -       cxt->pstore.flags = PSTORE_FLAGS_DMESG;
> +       if (info->dmesg_size)
> +               cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
> +       if (info->pmsg_size)
> +               cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
>
>         err = pstore_register(&cxt->pstore);
>         if (err) {
> @@ -919,9 +1128,10 @@ int blkz_register(struct blkz_info *info)
>                 goto free_pstore_buf;
>         }
>
> -       pr_info("Registered %s as blkzone backend for %s%s\n", info->name,
> +       pr_info("Registered %s as blkzone backend for %s%s%s\n", info->name,
>                         cxt->dbzs && cxt->bzinfo->dump_oops ? "Oops " : "",
> -                       cxt->dbzs && cxt->bzinfo->panic_write ? "Panic " : "");
> +                       cxt->dbzs && cxt->bzinfo->panic_write ? "Panic " : "",
> +                       cxt->pbz ? "Pmsg" : "");
>
>         module_put(owner);
>         return 0;
> @@ -949,7 +1159,7 @@ void blkz_unregister(struct blkz_info *info)
>         spin_unlock(&cxt->bzinfo_lock);
>
>         blkz_free_zones(&cxt->dbzs, &cxt->dmesg_max_cnt);
> -
> +       blkz_free_zone(&cxt->pbz);
>  }
>  EXPORT_SYMBOL_GPL(blkz_unregister);
>
> diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
> index 426cae4..6c6b4eb 100644
> --- a/include/linux/pstore_blk.h
> +++ b/include/linux/pstore_blk.h
> @@ -48,6 +48,7 @@ struct blkz_info {
>         const char *part_path;
>         unsigned long part_size;
>         unsigned long dmesg_size;
> +       unsigned long pmsg_size;
>         int dump_oops;
>         ssize_t (*read)(char *buf, size_t bytes, loff_t pos);
>         ssize_t (*write)(const char *buf, size_t bytes, loff_t pos);
> --
> 1.9.1
>


-- 
Kees Cook