pstore: fix ftrace dump, when ECC is enabled

total_size is sum of record->size and record->ecc_notice_size (ECC: No
errors detected). When ECC is not used, then there is no problem.
When ECC is enabled, then ftrace dump is decoded incorrectly after
restart.

First this affects starting offset calculation, that breaks
reading of all ftrace records.

  CPU:66 ts:51646260179894273 3818ffff80008002  fe00ffff800080f0  0x3818ffff80008002 <- 0xfe00ffff800080f0
  CPU:66 ts:56589664458375169 3818ffff80008002  ff02ffff800080f0  0x3818ffff80008002 <- 0xff02ffff800080f0
  CPU:67 ts:13194139533313 afe4ffff80008002  1ffff800080f0  0xafe4ffff80008002 <- 0x1ffff800080f0
  CPU:67 ts:13194139533313 b7d0ffff80008001  100ffff80008002  0xb7d0ffff80008001 <- 0x100ffff80008002
  CPU:67 ts:51646260179894273 8de0ffff80008001  202ffff80008002  0x8de0ffff80008001 <- 0x202ffff80008002

Second ECC notice message is printed like ftrace record and as a
result couple of last records are completely wrong.

For example, when the starting offset is fixed:

 CPU:0 ts:113 ffffffc00879bd04  ffffffc0080dc08c  cpuidle_enter <- do_idle+0x20c/0x290
 CPU:0 ts:114 ffffffc00879bd04  ffffffc0080dc08c  cpuidle_enter <- do_idle+0x20c/0x290
 CPU:100 ts:28259048229270629 6f4e203a4343450a  2073726f72726520  0x6f4e203a4343450a <- 0x2073726f72726520

Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Link: https://patch.msgid.link/20260215185156.317394-1-andrej.skvortzov@gmail.com
Signed-off-by: Kees Cook <kees@kernel.org>

Author: AndreySV

fs/pstore/inode.c

@@ -74,9 +74,9 @@ static void *pstore_ftrace_seq_start(struct seq_file *s, loff_t *pos)
 	if (!data)
 		return NULL;
 
-	data->off = ps->total_size % REC_SIZE;
+	data->off = ps->record->size % REC_SIZE;
 	data->off += *pos * REC_SIZE;
-	if (data->off + REC_SIZE > ps->total_size)
+	if (data->off + REC_SIZE > ps->record->size)
 		return NULL;
 
 	return_ptr(data);
@@ -94,7 +94,7 @@ static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
 
 	(*pos)++;
 	data->off += REC_SIZE;
-	if (data->off + REC_SIZE > ps->total_size)
+	if (data->off + REC_SIZE > ps->record->size)
 		return NULL;
 
 	return data;