linux-kernel - Re: [PATCH v3 4/4] perf: Use CAP_SYS_ADMIN instead of euid==0 with ftrace

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Date:   Mon, 12 Aug 2019 17:29:47 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Igor Lubashev <ilubashe@...mai.com>
Cc:     linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org,
        James Morris <jmorris@...ei.org>
Subject: Re: [PATCH v3 4/4] perf: Use CAP_SYS_ADMIN instead of euid==0 with
 ftrace

Em Mon, Aug 12, 2019 at 05:27:06PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Aug 12, 2019 at 05:22:51PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Wed, Aug 07, 2019 at 10:44:17AM -0400, Igor Lubashev escreveu:
> > > @@ -281,7 +283,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
> > >  		.events = POLLIN,
> > >  	};
> > >  
> > > -	if (geteuid() != 0) {
> > > +	if (!perf_cap__capable(CAP_SYS_ADMIN)) {
> > >  		pr_err("ftrace only works for root!\n");
> > 
> > I guess we should update the error message too? 
> > 
> 
> I.e. I applied this as a follow up patch:
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 01a5bb58eb04..ba8b65c2f9dc 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -284,7 +284,12 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
>  	};
>  
>  	if (!perf_cap__capable(CAP_SYS_ADMIN)) {
> -		pr_err("ftrace only works for root!\n");
> +		pr_err("ftrace only works for %s!\n",
> +#ifdef HAVE_LIBCAP_SUPPORT
> +		"users with the SYS_ADMIN capability"
> +#else
> +		"root"
> +#endif

                );

:-)
 
>  		return -1;
>  	}
>  

I've pushed the whole set to my tmp.perf/cap branch, please chec

- Arnaldo