Re: [PATCH 02/17] perf: Add ability to attach user level registersdump to sample

[Jiri Olsa]

On Wed, Jul 25, 2012 at 07:39:18PM +0200, Stephane Eranian wrote:
> On Sun, Jul 22, 2012 at 2:14 PM, Jiri Olsa <jolsa@xxxxxxxxxx> wrote:

SNIP

> > +       if (sample_type & PERF_SAMPLE_REGS_USER) {
> > +               u64 avail = (data->regs_user != NULL);
> > +
> > +               /*
> > +                * If there are no regs to dump, notice it through
> > +                * first u64 being zero.
> > +                */
> > +               perf_output_put(handle, avail);
> > +
> The only role of avail is to report whether or not you've captured actual
> registers. Could it be used to report the sampled process ABI (32 vs. 64)
> instead? Something like:
>       PERF_SAMPLE_REGS_ABI_NONE -> no regs captured (emulate your
> current behavior)
>       PERF_SAMPLE_REGS_ABI_32 -> 32 bit ABI regs captured
>       PERF_SAMPLE_REGS_ABI_64 -> 64 bit ABI regs captured
> 
> That could help the tools interpret the register values.

Yes, I think that could help once we start dealing with compat tasks.

The current userspace code stays untouched, because it checks for
'avail != 0', which stays even with your change.

I think this could be sent later with all other fixes I'm already
working on. But I can work/send it preferentially before whole patchset
is taken if you like.

thanks,
jirka
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/