[PATCH] android_ab: Fix backup offset calculation

[Sam Protsenko]

On Wed, Aug 7, 2024 at 9:14 AM Joshua Watt <jpewhacker at gmail.com> wrote:
>
> The backup offset is in bytes, but was incorrectly be interpreted as
> blocks, leading to it being written to the wrong location. Fix the
> calculation and clarify that ANDROID_AB_BACKUP_OFFSET is in bytes and
> must be a multiple of the block size.
>
> Signed-off-by: Joshua Watt <JPEWhacker at gmail.com>
> ---

In addition to what Mattijs said, I think it makes sense to add
"Fixes:" tag for this patch.

>  boot/android_ab.c | 4 ++--
>  common/Kconfig    | 3 ++-
>  2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/boot/android_ab.c b/boot/android_ab.c
> index 143f373aae..b253200161 100644
> --- a/boot/android_ab.c
> +++ b/boot/android_ab.c
> @@ -139,8 +139,8 @@ static int ab_control_store(struct blk_desc *dev_desc,
>  {
>         ulong abc_offset, abc_blocks, ret;
>
> -       abc_offset = offset +
> -                    offsetof(struct bootloader_message_ab, slot_suffix) /
> +       abc_offset = (offset +
> +                     offsetof(struct bootloader_message_ab, slot_suffix)) /
>                      part_info->blksz;
>         abc_blocks = DIV_ROUND_UP(sizeof(struct bootloader_control),
>                                   part_info->blksz);
> diff --git a/common/Kconfig b/common/Kconfig
> index 83c81edac2..e1b8557e0c 100644
> --- a/common/Kconfig
> +++ b/common/Kconfig
> @@ -986,7 +986,8 @@ config ANDROID_AB_BACKUP_OFFSET
>         help
>           If non-zero, a backup bootloader message starting at this offset in
>           the partition will tried in the event that the primary one (starting
> -         at offset 0) fails its checksum.
> +         at offset 0) fails its checksum. The offset is in bytes and must be
> +         multiple of the block size.
>
>  endmenu
>
> --
> 2.45.2
>