Messages in this thread | | | Date | Tue, 18 Jan 2022 09:52:58 +0000 | From | Will Deacon <> | Subject | Re: [RFC PATCH 2/2] perf: arm_spe: Enable CONTEXT packets in SPE traces if the profiler runs in CPU mode. |
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On Mon, Jan 17, 2022 at 12:44:32PM +0000, German Gomez wrote: > Enable CONTEXT packets in SPE traces if the profiler runs in CPU mode. > This is no less permissive than the existing behavior for the following > reason: > > If perf_event_paranoid <= 0, then non perfmon_capable() users can open > a per-CPU event. With a per-CPU event, unpriviledged users are allowed > to profile _all_ processes, even ones owned by root. > > Without this change, users could see kernel addresses, root processes, > etc, but not gather the PIDs of those processes. The PID is probably the > least sensitive of all the information. > > It would be more idiomatic to check the perf_event_paranoid level with > perf_allow_cpu(), but this function is not exported so cannot be used > from a module. Looking for cpu != -1 is the indirect way of checking > the same thing as it could never get to arm_spe_pmu_event_init() without > perf_event_paranoid <= 0.
perf_allow_cpu() is a static inline so there's no need to export it. What's missing?
Will
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