Re: [PATCH] x86,seccomp,prctl: Remove PR_TSC_SIGSEGV and seccomp TSC filtering

[Andy Lutomirski]

On Fri, Oct 3, 2014 at 1:44 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Fri, Oct 03, 2014 at 01:27:52PM -0700, Andy Lutomirski wrote:
>> On Fri, Oct 3, 2014 at 1:22 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>> >
>> > We could make the rule be that RDPMC is enabled if a perf event is
>> > mmapped or TIF_SECCOMP is clear, but I'd prefer to be convinced that
>> > there's an actual performance issue first.  Ideally we can get this
>> > all working with no API or ABI change at all.
>>
>> No, we can't use that rule.  But we could say that RDPMC is enabled if
>> a perf event is mmapped and no thread in the mm uses seccomp.  I'll
>> grumble a little bit about adding yet another piece of seccomp state.
>
> Well, we could simply disable the RDPMC for everything TIF_SECCOMP.
> Should be fairly straight fwd.

That won't work.  I bet there are plenty of existing users of fairly
wide-open seccomp sandboxes that allow perf_event in.

-- 
Andy Lutomirski
AMA Capital Management, LLC
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