[Issue]

A format of variable name has been updated to type, id, count and ctime
to support holding multiple logs.

Format of current variable name
  dump-type0-1-2-12345678

  type:0
  id:1
  count:2
  ctime:12345678

On the other hand, if an old variable name before being updated
remains, users can't read it via /dev/pstore.

Format of old variable name
  dump-type0-1-12345678

  type:0
  id:1
  ctime:12345678

[Solution]

This patch adds a format check for the old variable name in a read callback
to make it readable.

Signed-off-by: Seiji Aguchi <redacted>
---
 drivers/firmware/efivars.c |   38 ++++++++++++++++++++++++++++----------
 1 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index dc69802..dd228d5 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c

@@ -681,17 +681,35 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                                *count = cnt;
                                timespec->tv_sec = time;
                                timespec->tv_nsec = 0;
-                               get_var_data_locked(efivars, &efivars->walk_entry->var);
-                               size = efivars->walk_entry->var.DataSize;
-                               *buf = kmalloc(size, GFP_KERNEL);
-                               if (*buf == NULL)
-                                       return -ENOMEM;
-                               memcpy(*buf, efivars->walk_entry->var.Data,
-                                      size);
-                               efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
-                                                  struct efivar_entry, list);
-                               return size;
+                       } else if (sscanf(name, "dump-type%u-%u-%lu",
+                                  type, &part, &time) == 3) {
+                               /*
+                                * Check if an old format,
+                                * which doesn't support holding
+                                * multiple logs, remains.
+                                */
+                               *id = part;
+                               *count = 0;
+                               timespec->tv_sec = time;
+                               timespec->tv_nsec = 0;
+                       } else {
+                               efivars->walk_entry = list_entry(
+                                       efivars->walk_entry->list.next,
+                                        struct efivar_entry, list);