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[187.26.98.68]) by smtp.gmail.com with ESMTPSA id t5sm2359942qkt.93.2019.08.12.13.27.09 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 12 Aug 2019 13:27:10 -0700 (PDT) From: Arnaldo Carvalho de Melo X-Google-Original-From: Arnaldo Carvalho de Melo Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 70EC640340; Mon, 12 Aug 2019 17:27:06 -0300 (-03) Date: Mon, 12 Aug 2019 17:27:06 -0300 To: Igor Lubashev Cc: linux-kernel@vger.kernel.org, Jiri Olsa , Alexey Budankov , Peter Zijlstra , Ingo Molnar , Mathieu Poirier , Alexander Shishkin , Namhyung Kim , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, James Morris Subject: Re: [PATCH v3 4/4] perf: Use CAP_SYS_ADMIN instead of euid==0 with ftrace Message-ID: <20190812202706.GH9280@kernel.org> References: <20190812202251.GG9280@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190812202251.GG9280@kernel.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.12.0 (2019-05-25) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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: > > Kernel requires CAP_SYS_ADMIN instead of euid==0 to mount debugfs for ftrace. > > Make perf do the same. > > > > Signed-off-by: Igor Lubashev > > --- > > tools/perf/builtin-ftrace.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c > > index ae1466aa3b26..d09eac8a6d57 100644 > > --- a/tools/perf/builtin-ftrace.c > > +++ b/tools/perf/builtin-ftrace.c > > @@ -13,6 +13,7 @@ > > #include > > #include > > #include > > +#include > > > > #include "debug.h" > > #include > > @@ -21,6 +22,7 @@ > > #include "target.h" > > #include "cpumap.h" > > #include "thread_map.h" > > +#include "util/cap.h" > > #include "util/config.h" > > > > > > @@ -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; }