[U-Boot] [PATCH] disk: fix unaligned access in efi partitions

Stephen Warren
2013-03-29T15:57:05Z

On 03/29/2013 09:13 AM, Marc Dietrich wrote:
> On Friday 29 March 2013 13:32:26 Albert ARIBAUD wrote:
>> On Fri, 29 Mar 2013 12:28:58 +0100, Marc Dietrich <marvin24@gmx.de> wrote:
>>> start_sect is not aligned to a 4 byte boundary thus causing exceptions
>>> on ARM platforms. Access this field via the get_unaligned macro.

>>> - le32_to_cpu(part->start_sect) == 1UL) {
>>> + le32_to_cpu(get_unaligned(&part->start_sect)) == 1UL) {

>> Also, beside the asm/unaligned.h file I gave as an example, other header
>> files in include/linux/unaligned/ exist that provide alignment-related
>> macros, notably with _le and _be versions. Maybe you can find one that
>> combines the effects of both le32_to_cpu() and get_unaligned()?
>
> I looks like get_unaligned does the job for us already, so we can leave the
> le32_to_cpu out. But I cannot test it here because of missing big endian
> machine with efi and my two brain halfs are already swapped until confusion
> (start_sect is defined as _le32).
>
> Albert, I like to get a fix for this into 2013.04 if possible. Maybe someone
> with more endian experience can look at it quickly.

Looking at include/linux/unaligned/generic.h, I think you can just use:

__get_unaligned_le(&part->start_sect) == 1UL

I don't believe the __le32 marking of the start_sect field will have any
effect, since the implementation of __get_unaligned_le accesses the
variable byte-by-byte.