[PATCH v3 2/3] mtd: mtdoops: Create a header structure for the saved mtdoops.

From: Jean-Marc Eurin
Date: Thu Apr 14 2022 - 20:14:16 EST


Create a dump header to enable the addition of fields without having
to modify the rest of the code.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Jean-Marc Eurin <jmeurin@xxxxxxxxxx>
---
drivers/mtd/mtdoops.c | 55 +++++++++++++++++++++++--------------------
1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index 09a26747f490..f80468ef31c6 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -22,9 +22,6 @@
/* Maximum MTD partition size */
#define MTDOOPS_MAX_MTD_SIZE (8 * 1024 * 1024)

-#define MTDOOPS_KERNMSG_MAGIC 0x5d005d00
-#define MTDOOPS_HEADER_SIZE 8
-
static unsigned long record_size = 4096;
module_param(record_size, ulong, 0400);
MODULE_PARM_DESC(record_size,
@@ -40,6 +37,13 @@ module_param(dump_oops, int, 0600);
MODULE_PARM_DESC(dump_oops,
"set to 1 to dump oopses, 0 to only dump panics (default 1)");

+#define MTDOOPS_KERNMSG_MAGIC 0x5d005d00
+
+struct mtdoops_hdr {
+ u32 seq;
+ u32 magic;
+} __packed;
+
static struct mtdoops_context {
struct kmsg_dumper dump;

@@ -178,16 +182,16 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
{
struct mtd_info *mtd = cxt->mtd;
size_t retlen;
- u32 *hdr;
+ struct mtdoops_hdr *hdr;
int ret;

if (test_and_set_bit(0, &cxt->oops_buf_busy))
return;

/* Add mtdoops header to the buffer */
- hdr = cxt->oops_buf;
- hdr[0] = cxt->nextcount;
- hdr[1] = MTDOOPS_KERNMSG_MAGIC;
+ hdr = (struct mtdoops_hdr *)cxt->oops_buf;
+ hdr->seq = cxt->nextcount;
+ hdr->magic = MTDOOPS_KERNMSG_MAGIC;

if (panic) {
ret = mtd_panic_write(mtd, cxt->nextpage * record_size,
@@ -222,8 +226,9 @@ static void mtdoops_workfunc_write(struct work_struct *work)
static void find_next_position(struct mtdoops_context *cxt)
{
struct mtd_info *mtd = cxt->mtd;
+ struct mtdoops_hdr hdr;
int ret, page, maxpos = 0;
- u32 count[MTDOOPS_HEADER_SIZE/sizeof(u32)], maxcount = 0xffffffff;
+ u32 maxcount = 0xffffffff;
size_t retlen;

for (page = 0; page < cxt->oops_pages; page++) {
@@ -231,32 +236,31 @@ static void find_next_position(struct mtdoops_context *cxt)
continue;
/* Assume the page is used */
mark_page_used(cxt, page);
- ret = mtd_read(mtd, page * record_size, MTDOOPS_HEADER_SIZE,
- &retlen, (u_char *)&count[0]);
- if (retlen != MTDOOPS_HEADER_SIZE ||
+ ret = mtd_read(mtd, page * record_size, sizeof(hdr),
+ &retlen, (u_char *)&hdr);
+ if (retlen != sizeof(hdr) ||
(ret < 0 && !mtd_is_bitflip(ret))) {
- printk(KERN_ERR "mtdoops: read failure at %ld (%td of %d read), err %d\n",
- page * record_size, retlen,
- MTDOOPS_HEADER_SIZE, ret);
+ printk(KERN_ERR "mtdoops: read failure at %ld (%td of %ld read), err %d\n",
+ page * record_size, retlen, sizeof(hdr), ret);
continue;
}

- if (count[0] == 0xffffffff && count[1] == 0xffffffff)
+ if (hdr.seq == 0xffffffff && hdr.magic == 0xffffffff)
mark_page_unused(cxt, page);
- if (count[0] == 0xffffffff || count[1] != MTDOOPS_KERNMSG_MAGIC)
+ if (hdr.seq == 0xffffffff || hdr.magic != MTDOOPS_KERNMSG_MAGIC)
continue;
if (maxcount == 0xffffffff) {
- maxcount = count[0];
+ maxcount = hdr.seq;
maxpos = page;
- } else if (count[0] < 0x40000000 && maxcount > 0xc0000000) {
- maxcount = count[0];
+ } else if (hdr.seq < 0x40000000 && maxcount > 0xc0000000) {
+ maxcount = hdr.seq;
maxpos = page;
- } else if (count[0] > maxcount && count[0] < 0xc0000000) {
- maxcount = count[0];
+ } else if (hdr.seq > maxcount && hdr.seq < 0xc0000000) {
+ maxcount = hdr.seq;
maxpos = page;
- } else if (count[0] > maxcount && count[0] > 0xc0000000
+ } else if (hdr.seq > maxcount && hdr.seq > 0xc0000000
&& maxcount > 0x80000000) {
- maxcount = count[0];
+ maxcount = hdr.seq;
maxpos = page;
}
}
@@ -287,8 +291,9 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper,

if (test_and_set_bit(0, &cxt->oops_buf_busy))
return;
- kmsg_dump_get_buffer(&iter, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
- record_size - MTDOOPS_HEADER_SIZE, NULL);
+ kmsg_dump_get_buffer(&iter, true,
+ cxt->oops_buf + sizeof(struct mtdoops_hdr),
+ record_size - sizeof(struct mtdoops_hdr), NULL);
clear_bit(0, &cxt->oops_buf_busy);

if (reason != KMSG_DUMP_OOPS) {
--
2.36.0.rc0.470.gd361397f0d-goog