Re: [PATCH 1/8] perf: Allow to block process in syscall tracepoints

[Jiri Olsa <jolsa@redhat.com>]

On Thu, Dec 06, 2018 at 09:17:07AM +0100, Peter Zijlstra wrote:
> On Wed, Dec 05, 2018 at 05:05:02PM +0100, Jiri Olsa wrote:
> > @@ -10461,6 +10484,19 @@ SYSCALL_DEFINE5(perf_event_open,
> >  			return -EINVAL;
> >  	}
> >  
> > +	if (attr.block) {
> > +		/*
> > +		 * Allow only syscall tracepoints, check for syscall class
> > +		 * is made in the tracepoint event_init callback.
> > +		 */
> > +		if (attr.type != PERF_TYPE_TRACEPOINT)
> > +			return -EINVAL;
> > +
> > +		/* Allow to block only if we attach to a process. */
> > +		if (pid == -1)
> > +			return -EINVAL;
> > +	}
> > +
> >  	/* Only privileged users can get physical addresses */
> >  	if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
> >  	    perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> 
> That's fairly horrible and will, when copied, lead to a giant mess.
> 
> Please see the whole exclusion patch set here:
> 
>   https://lkml.kernel.org/r/1543230756-15319-1-git-send-email-andrew.murray@arm.com
> 
> PERF_PMU_CAP_BLOCK sounds like something you'd want here.

ok, that's better

jirka