diff mbox series

[v1] nvmem: address crc32 check on redundant-layout powerpc machines

Message ID 41e7ab94800b4a9aef73e212464bd94117429bec.1667555240.git.chunkeey@gmail.com
State New
Headers
Series [v1] nvmem: address crc32 check on redundant-layout powerpc machines |

Commit Message

Christian Lamparter Nov. 4, 2022, 9:47 a.m. UTC 
  The Western Digital MyBook Live (PowerPC 464/APM82181)
has a set of redundant u-boot-env. Loading up the driver
causes it to error out with:

| u_boot_env: Invalid calculated CRC32: 0x4f8f2c86 (expected: 0x98b14514)
| u_boot_env: probe of partition@1e000 failed with error -22

Looking up the userspace libubootenv utilities source [0],
it looks like the "mark" or "flag" is not part of the
crc32 sum... which is unfortunate :(

|static int libuboot_load(struct uboot_ctx *ctx)
|{
|[...]
|       if (ctx->redundant) {
|		[...]
|               offsetdata = offsetof(struct uboot_env_redund, data);
|		[...]
|       }
|       usable_envsize = ctx->size - offsetdata;
|       buf[0] = malloc(bufsize);
|[...]
|	for (i = 0; i < copies; i++) {
|		data = (uint8_t *)(buf[i] + offsetdata);
|               uint32_t crc;
|
|		ret = devread(ctx, i, buf[i]);
|		[...]
|		crc = *(uint32_t *)(buf[i] + offsetcrc);
|               dev->crc = crc32(0, (uint8_t *)data, usable_envsize);
|

Now, this alone didn't fully fix the kernel's uboot-env nvmem
driver. The driver then ran into an endian error on the
big-endian powerpc device:

| u_boot_env: Invalid calculated CRC32: 0x1445b198 (expected: 0x98b14514)

however the __le32 type for the crc32 value is justified because the
the crc32() is just a macro for crc32_le(). So, to side-step that
problem, the crc32 check gets extended to also accept a byteswapped
crc32.

[0] https://github.com/sbabic/libubootenv/blob/master/src/uboot_env.c#L951
Fixes: d5542923f200 ("nvmem: add driver handling U-Boot environment variables")
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
---
Might it be better to add a dt-property (I wouldn't piggy-pack on
the existing big-endian;) to specify that the crc32 value stored
in the flash/rom is swapped?
---
 drivers/nvmem/u-boot-env.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Rafał Miłecki Nov. 4, 2022, 10:04 a.m. UTC | #1 
On 2022-11-04 10:47, Christian Lamparter wrote:
> The Western Digital MyBook Live (PowerPC 464/APM82181)
> has a set of redundant u-boot-env. Loading up the driver
> causes it to error out with:
> 
> | u_boot_env: Invalid calculated CRC32: 0x4f8f2c86 (expected: 
> 0x98b14514)
> | u_boot_env: probe of partition@1e000 failed with error -22
> 
> Looking up the userspace libubootenv utilities source [0],
> it looks like the "mark" or "flag" is not part of the
> crc32 sum... which is unfortunate :(
> 
> |static int libuboot_load(struct uboot_ctx *ctx)
> |{
> |[...]
> |       if (ctx->redundant) {
> |		[...]
> |               offsetdata = offsetof(struct uboot_env_redund, data);
> |		[...]
> |       }
> |       usable_envsize = ctx->size - offsetdata;
> |       buf[0] = malloc(bufsize);
> |[...]
> |	for (i = 0; i < copies; i++) {
> |		data = (uint8_t *)(buf[i] + offsetdata);
> |               uint32_t crc;
> |
> |		ret = devread(ctx, i, buf[i]);
> |		[...]
> |		crc = *(uint32_t *)(buf[i] + offsetcrc);
> |               dev->crc = crc32(0, (uint8_t *)data, usable_envsize);
> |

Thanks for the fix, it may be I didn't actually test that code.

That change has nothing to do with byte swapping so I' suggest TWO
separated patches.


> Now, this alone didn't fully fix the kernel's uboot-env nvmem
> driver. The driver then ran into an endian error on the
> big-endian powerpc device:
> 
> | u_boot_env: Invalid calculated CRC32: 0x1445b198 (expected: 
> 0x98b14514)
> 
> however the __le32 type for the crc32 value is justified because the
> the crc32() is just a macro for crc32_le(). So, to side-step that
> problem, the crc32 check gets extended to also accept a byteswapped
> crc32.

Can you try this pending patch, please?
[PATCH v2] nvmem: u-boot-env: align endianness of crc32 values
https://lore.kernel.org/lkml/20221012155133.287-1-musashino.open@gmail.com/
diff mbox series

Patch

diff --git a/drivers/nvmem/u-boot-env.c b/drivers/nvmem/u-boot-env.c
index 8e72d1bbd649..f78e2f5d2ef1 100644
--- a/drivers/nvmem/u-boot-env.c
+++ b/drivers/nvmem/u-boot-env.c
@@ -135,7 +135,7 @@  static int u_boot_env_parse(struct u_boot_env *priv)
 		break;
 	case U_BOOT_FORMAT_REDUNDANT:
 		crc32_offset = offsetof(struct u_boot_env_image_redundant, crc32);
-		crc32_data_offset = offsetof(struct u_boot_env_image_redundant, mark);
+		crc32_data_offset = offsetof(struct u_boot_env_image_redundant, data);
 		data_offset = offsetof(struct u_boot_env_image_redundant, data);
 		break;
 	}
@@ -144,7 +144,11 @@  static int u_boot_env_parse(struct u_boot_env *priv)
 	data_len = priv->mtd->size - data_offset;
 
 	calc = crc32(~0, buf + crc32_data_offset, crc32_data_len) ^ ~0L;
-	if (calc != crc32) {
+	/*
+	 * also accept byteswapped crc32 values for compatibility with
+	 * existing legacy powerpc devices and userspace tools.
+	 */
+	if (calc != crc32 && calc != swab32(crc32)) {
 		dev_err(dev, "Invalid calculated CRC32: 0x%08x (expected: 0x%08x)\n", calc, crc32);
 		err = -EINVAL;
 		goto err_kfree;