Messages in this thread | | | Date | Mon, 1 Feb 2021 14:41:33 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/4] perf/core: Add support to exclude kernel mode instruction tracing |
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On Mon, Feb 01, 2021 at 01:11:04PM +0530, Sai Prakash Ranjan wrote:
> Ok I suppose you mean CONFIG_SECURITY_LOCKDOWN_LSM? But I don't see > how this new config has to depend on that? This can work independently > whether complete lockdown is enforced or not since it applies to only > hardware instruction tracing. Ideally this depends on several hardware > tracing configs such as ETMs and others but we don't need them because > we are already exposing PERF_PMU_CAP_ITRACE check in the events core.
If you don't have lockdown, root pretty much owns the kernel, or am I missing something?
> be used for some speculative execution based attacks. Which other > kernel level PMUs can be used to get a full branch trace that is not > locked down? If there is one, then this should probably be applied to > it as well.
Just the regular counters. The information isn't as accurate, but given enough goes you can infer plenty.
Just like all the SMT size-channel attacks.
Sure, PT and friends make it even easier, but I don't see a fundamental distinction.
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