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SubjectRe: [PATCH v1 2/2]: Documentation/admin-guide: introduce perf-security.rst file
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Hi,
On 19.11.2018 13:33, Peter Zijlstra wrote:
> On Mon, Nov 19, 2018 at 08:42:52AM +0300, Alexey Budankov wrote:
>>
>> Implement initial version of perf-security.rst documentation file
>> initially covering security concerns related to PCL/Perf performance
>> monitoring in multiuser environments.
>
> Ditch the PCL thing. That's not a term used anywhere in the kernel.

Ok. Which is the proper wording to reference to Perf kernel subsystem?

>
> Also:
>
>> +PCL/Perf unprivileged users
>> +---------------------------
>> +
>> +PCL/Perf *scope* and *access* control for unprivileged processes is governed by
>> +perf_event_paranoid [2]_ setting:
>> +
>> +**-1**:
>> + Impose no *scope* and *access* restrictions on using PCL performance
>> + monitoring. Per-user per-cpu perf_event_mlock_kb [2]_ locking limit is
>> + ignored when allocating memory buffers for storing performance data.
>> + This is the least secure mode since allowed monitored *scope* is
>> + maximized and no PCL specific limits are imposed on *resources*
>> + allocated for performance monitoring.
>> +
>> +**>=0**:
>> + *scope* includes per-process and system wide performance monitoring
>> + but excludes raw tracepoints and ftrace function tracepoints monitoring.
>> + CPU and system events happened when executing either in user or
>> + in kernel space can be monitored and captured for later analysis.
>> + Per-user per-cpu perf_event_mlock_kb locking limit is imposed but
>> + ignored for unprivileged processes with CAP_IPC_LOCK [6]_ capability.
>> +
>> +**>=1**:
>> + *scope* includes per-process performance monitoring only and excludes
>> + system wide performance monitoring. CPU and system events happened when
>> + executing either in user or in kernel space can be monitored and
>> + captured for later analysis. Per-user per-cpu perf_event_mlock_kb
>> + locking limit is imposed but ignored for unprivileged processes with
>> + CAP_IPC_LOCK capability.
>> +
>> +**>=2**:
>> + *scope* includes per-process performance monitoring only. CPU and system
>> + events happened when executing in user space only can be monitored and
>> + captured for later analysis. Per-user per-cpu perf_event_mlock_kb
>> + locking limit is imposed but ignored for unprivileged processes with
>> + CAP_IPC_LOCK capability.
>> +
>> +**>=3**:
>> + Restrict *access* to PCL performance monitoring for unprivileged processes.
>> + This is the default on Debian and Android [7]_ , [8]_ .
>
> that ** crud is unreadable.

It can be avoided without missing the sense.

"two asterisks: **text** for strong emphasis (boldface)".

Thanks,
Alexey

>
> http://lkml.kernel.org/r/094556ca-ea87-9c4a-2115-600d2833fb2a@darmarit.de
>

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