James Clarke <jrtc27@xxxxxxxxxx> writes:
> Since the MBR layout only has partition records as 2-byte aligned, the 32-bit
> fields in them are not aligned. Thus, they cannot be accessed on some
> architectures (such as SPARC) by using a "struct MBR_part_record *" pointer,
> as the compiler can assume that the pointer is properly aligned. Instead, the
> records must be accessed by going through the MBR struct itself every time.
>
> Signed-off-by: James Clarke <jrtc27@xxxxxxxxxx>
> ---
> super-mbr.c | 6 ++++++
> util.c | 14 +++++++-------
> 2 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/super-mbr.c b/super-mbr.c
> index 62b3f03..303dde4 100644
> --- a/super-mbr.c
> +++ b/super-mbr.c
> @@ -57,6 +57,9 @@ static void examine_mbr(struct supertype *st, char *homehost)
>
> printf(" MBR Magic : %04x\n", sb->magic);
> for (i = 0; i < MBR_PARTITIONS; i++)
> + /* Have to make every access through sb rather than using a pointer to
> + * the partition table (or an entry), since the entries are not
> + * properly aligned. */
> if (sb->parts[i].blocks_num)
> printf("Partition[%d] : %12lu sectors at %12lu (type %02x)\n",
> i,
Reading through this thread and Neil's comments, I think it's reasonable
to do what you are doing with pointer access. However I also believe
that packed should be applied as Neil suggests.
Second, as code lines per definition are 80 characters wide, please make
sure your patch complies with this. I know some of the older code
violates this, but we shouldn't be adding more code which does so.
If you send me an updated patch I shall be happy to apply it.
Jes
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