Re: [PATCH 03/23] perf: Add ability to attach user level registersdump to sample
From: Frederic Weisbecker
Date: Wed Jun 27 2012 - 11:24:05 EST
On Wed, Jun 27, 2012 at 05:13:44PM +0200, Stephane Eranian wrote:
> On Wed, Jun 27, 2012 at 5:11 PM, Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:
> > On Tue, Jun 19, 2012 at 05:47:54PM +0200, Jiri Olsa wrote:
> >> @@ -4061,6 +4105,19 @@ void perf_prepare_sample(struct perf_event_header *header,
> >> }
> >> header->size += size;
> >> }
> >> +
> >> + if (sample_type & PERF_SAMPLE_REGS_USER) {
> >> + /* regs dump available bool */
> >> + int size = sizeof(u64);
> >> +
> >> + data->regs_user = perf_sample_regs_user(regs);
> >> + if (data->regs_user) {
> >> + u64 mask = event->attr.sample_regs_user;
> >> + size += hweight64(mask) * sizeof(u64);
> >> + }
> >> +
> >> + header->size += size;
> >
> > We'll need to remove the 64 bits registers for compat tasks but other than
> > that, it looks ok.
> You cannot do this. You cannot remove register values from under the hood.
> The only way the user has to parse the sample is the sample_regs_users bitmask.
> You have to return 0 for those unexisting regs for compat tasks.
You mean fill unexisting reg values with 0? Yeah that works.
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