Re: [PATCH] Support new 'h' core note item format for hidden fields

[Mark Wielaard <mjw at redhat dot com>]

On Tue, 2013-10-01 at 00:08 +0200, Petr Machata wrote:
> Signed-off-by: Petr Machata <pmachata@redhat.com>
> ---
> 
>  The use case here is NT_ARM_HW_BREAK and NT_ARM_HW_WATCH core notes.
>  These end in a 4-byte padding field.  If that field is absent from the
>  note description, readelf notices that we still have data left, and
>  does another pass through the items.  But we don't want to really show
>  that field either, as it carries no useful information.  Hence this.

If I understand correctly this is because this comment in
handle_core_items:

  /* This set of items consumed a certain amount of the note's data.
     If there is more data there, we have another unit of the same size.
     Loop to print that out too.  */

And it uses gelf_fsize on the item type to decide how big the consumed
data was. Which doesn't know about any padding. Right?

>  I initially chose '\0' for that field, but handle_auxv_note uses that
>  for fields that should be hidden if all zero, but displayed otherwise.
>  That might be eventually useful for core note items as well.

'h' is nice for hidden, but would 'p' for padding be more apt?

>  OK for master?

It looks OK, but I like to get this in together with the actual code
using it (it can still be a separate commit). Just to make sure that it
is actually used.

Thanks,

Mark