linux-kernel - Re: [PATCH] x86,seccomp,prctl: Remove PR_TSC

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Message-ID: <20141003204443.GP10583@worktop.programming.kicks-ass.net>
Date:	Fri, 3 Oct 2014 22:44:43 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Erik Bosman <ebn310@....vu.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux API <linux-api@...r.kernel.org>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	X86 ML <x86@...nel.org>
Subject: Re: [PATCH] x86,seccomp,prctl: Remove PR_TSC_SIGSEGV and seccomp TSC
 filtering

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@...capital.net> 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.
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