Albert,
On Friday 29 March 2013 08:00:54 Albert ARIBAUD wrote:
On Thu, 28 Mar 2013 23:35 +0100, Marc Dietrich marvin24@gmx.de wrote:
[ ... ] On Thursday 28 March 2013 21:42:13 Albert ARIBAUD wrote:
Which fields, which structures, which files are affected by the unalignment issue?
in my test case, it is the start sector of a partition (check include/part_efi.h). disk/part_efi.c reads the legacy mbr (to an aligned buffer) which has a partition structure on offset 440+4+2 (<- not aligned to 4 byte boundary) and inside this a 32 bit field start_sect (aligned to 4 byte boundary). Reading this field (and also the next, nr_sects) will cause an exception. Same is for part_dos, but there we still use le32_to_int which reads byte by byte. I didn't checked others.
Thanks for clarifying.
Considering this is about a very small number of reads, I strongly prefer that these reads be done through the get_unaligned(&field) macro defined in e.g. arch/arm/include/asm/unaligned.h, even at the slightly added cost of decomposing the reads into 8-bit accesses.
ok, this is what I was actually looking for :-) I've sent a new patch.
Marc