[U-Boot] [PATCH] fs: btrfs: Fix unaligned memory accesses

[Robert Nelson]

On Sat, Jan 20, 2018 at 1:17 AM, Alberto Sánchez Molero
<alsamolero at gmail.com> wrote:
> Loading files stored with lzo compression from a btrfs filesystem was
> producing unaligned memory accesses, which were causing a data abort
> and a reset on an Orange Pi Zero.
>
> The change in hash.c is not triggered by any error but follows the
> same pattern. Please confirm.
>
> Fixed according to doc/README.unaligned-memory-access.txt

Awesome!

Marek, this fixes the issue i was also seeing on the Beagle's with lzo
compression.

Tested-by: Robert Nelson <robertcnelson at gmail.com>


>
> Signed-off by: Alberto Sánchez Molero <alsamolero at gmail.com>
> ---
>  fs/btrfs/compression.c | 5 +++--
>  fs/btrfs/hash.c        | 3 ++-
>  2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index a59ff5a..4e685a0 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -9,6 +9,7 @@
>  #include "btrfs.h"
>  #include <linux/lzo.h>
>  #include <u-boot/zlib.h>
> +#include <asm/unaligned.h>
>
>  static u32 decompress_lzo(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen)
>  {
> @@ -19,7 +20,7 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen,
> u8 *dbuf, u32 dlen)
>      if (clen < 4)
>          return -1;
>
> -    tot_len = le32_to_cpu(*(u32 *) cbuf);
> +    tot_len = le32_to_cpu(get_unaligned((u32 *) cbuf));
>      cbuf += 4;
>      clen -= 4;
>      tot_len -= 4;
> @@ -32,7 +33,7 @@ static u32 decompress_lzo(const u8 *cbuf, u32 clen,
> u8 *dbuf, u32 dlen)
>      res = 0;
>
>      while (tot_len > 4) {
> -        in_len = le32_to_cpu(*(u32 *) cbuf);
> +        in_len = le32_to_cpu(get_unaligned((u32 *) cbuf));
>          cbuf += 4;
>          clen -= 4;
>
> diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
> index f8a50e5..1c75ea8 100644
> --- a/fs/btrfs/hash.c
> +++ b/fs/btrfs/hash.c
> @@ -8,6 +8,7 @@
>
>  #include "btrfs.h"
>  #include <u-boot/crc.h>
> +#include <asm/unaligned.h>
>
>  static u32 btrfs_crc32c_table[256];
>
> @@ -34,5 +35,5 @@ u32 btrfs_csum_data(char *data, u32 seed, size_t len)
>
>  void btrfs_csum_final(u32 crc, void *result)
>  {
> -    *((u32 *) result) = cpu_to_le32(~crc);
> +    put_unaligned(cpu_to_le32(~crc), (u32 *) result);
>  }
> --
> 2.16.0
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-- 
Robert Nelson
https://rcn-ee.com/