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From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date:   Thu, 23 Apr 2020 10:22:01 -0300
To:     Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        "selinux@vger.kernel.org" <selinux@vger.kernel.org>,
        "linux-security-module@vger.kernel.org" 
        <linux-security-module@vger.kernel.org>
Subject: Re: [PATCH v2 2/4] perf docs: substitute CAP_SYS_ADMIN with
 CAP_PERFMON where needed
Message-ID: <20200423132201.GB19437@kernel.org>
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 <f1b48de9-e2b7-d20b-3686-3a15b73ef45c@linux.intel.com>
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Em Wed, Apr 22, 2020 at 05:44:53PM +0300, Alexey Budankov escreveu:
> 
> Substitute CAP_SYS_ADMIN with CAP_PERFMON in the docs where admin
> is mentioned. CAP_SYS_ADMIN still works in keeping with user space
> backward compatibility approach.

Same issue as with the previous patch, the documentation is for the
tool, that may be used in older kernels, so we need to clarify that
CAP_PERFMON requires updating libcap and the kernel, if that isn't
possible, then CAP_SYS_ADMIN is needed.

- Arnaldo
 
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
>  tools/perf/Documentation/perf-intel-pt.txt | 2 +-
>  tools/perf/design.txt                      | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
> index 456fdcbf26ac..176597be0755 100644
> --- a/tools/perf/Documentation/perf-intel-pt.txt
> +++ b/tools/perf/Documentation/perf-intel-pt.txt
> @@ -687,7 +687,7 @@ The v4.2 kernel introduced support for a context switch metadata event,
>  PERF_RECORD_SWITCH, which allows unprivileged users to see when their processes
>  are scheduled out and in, just not by whom, which is left for the
>  PERF_RECORD_SWITCH_CPU_WIDE, that is only accessible in system wide context,
> -which in turn requires CAP_SYS_ADMIN.
> +which in turn requires CAP_PERFMON.
>  
>  Please see the 45ac1403f564 ("perf: Add PERF_RECORD_SWITCH to indicate context
>  switches") commit, that introduces these metadata events for further info.
> diff --git a/tools/perf/design.txt b/tools/perf/design.txt
> index a42fab308ff6..6fd879440c40 100644
> --- a/tools/perf/design.txt
> +++ b/tools/perf/design.txt
> @@ -258,8 +258,7 @@ gets schedule to. Per task counters can be created by any user, for
>  their own tasks.
>  
>  A 'pid == -1' and 'cpu == x' counter is a per CPU counter that counts
> -all events on CPU-x. Per CPU counters need CAP_PERFMON or CAP_SYS_ADMIN
> -privilege.
> +all events on CPU-x. Per CPU counters need CAP_PERFMON privilege.
>  
>  The 'flags' parameter is currently unused and must be zero.
>  
> -- 
> 2.24.1
> 
> 

-- 

- Arnaldo