[U-Boot] [PATCH] disk:efi: avoid unaligned access on efi partition

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Piotr,

On Fri, 11 Oct 2013 15:31:10 +0200, Piotr Wilczek
<p.wilczek@samsung.com> wrote:

> In this patch static variable and memcpy instead of an assignment
> are used to avoid unaligned access exception on some ARM platforms.
> 
> Signed-off-by: Piotr Wilczek <p.wilczek@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> CC: Tom Rini <trini@ti.com>
> ---
>  disk/part_efi.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/disk/part_efi.c b/disk/part_efi.c
> index b7524d6..303b8af 100644
> --- a/disk/part_efi.c
> +++ b/disk/part_efi.c
> @@ -224,7 +224,8 @@ static int set_protective_mbr(block_dev_desc_t *dev_desc)
>  	p_mbr->signature = MSDOS_MBR_SIGNATURE;
>  	p_mbr->partition_record[0].sys_ind = EFI_PMBR_OSTYPE_EFI_GPT;
>  	p_mbr->partition_record[0].start_sect = 1;
> -	p_mbr->partition_record[0].nr_sects = (u32) dev_desc->lba;
> +	memcpy(&p_mbr->partition_record[0].nr_sects, &dev_desc->lba,
> +	       sizeof(dev_desc->lba));
>  
>  	/* Write MBR sector to the MMC device */
>  	if (dev_desc->block_write(dev_desc->dev, 0, 1, p_mbr) != 1) {
> @@ -387,8 +388,9 @@ int gpt_fill_pte(gpt_header *gpt_h, gpt_entry *gpt_e,
>  			gpt_e[i].ending_lba = cpu_to_le64(offset - 1);
>  
>  		/* partition type GUID */
> +		static efi_guid_t basic_guid = PARTITION_BASIC_DATA_GUID;
>  		memcpy(gpt_e[i].partition_type_guid.b,
> -			&PARTITION_BASIC_DATA_GUID, 16);
> +			&basic_guid, 16);

Usually, an all-caps symbol is a macro, which makes taking its address
a no-no.

Besides, doing a memcpy() for 32-bit quantities seems like overkill
for me. Any reason you cannot simply use asm/unaligned.h and either
get_unaligned or put_unaligned depending on where the alignment issue
lies?
 
>  #ifdef CONFIG_PARTITION_UUIDS
>  		str_uuid = partitions[i].uuid;

Amicalement,
-- 
Albert.