From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Andy Lutomirski <luto@kernel.org>,
David Ahern <dsahern@gmail.com>, Jiri Olsa <jolsa@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Wang Nan <wangnan0@huawei.com>
Subject: [PATCH 3/7] perf evsel: Fix attr.exclude_kernel setting for default cycles:p
Date: Fri, 29 Sep 2017 13:00:13 -0300 [thread overview]
Message-ID: <20170929160017.29335-4-acme@kernel.org> (raw)
In-Reply-To: <20170929160017.29335-1-acme@kernel.org>
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Yet another fix for probing the max attr.precise_ip setting: it is not
enough settting attr.exclude_kernel for !root users, as they _can_
profile the kernel if the kernel.perf_event_paranoid sysctl is set to
-1, so check that as well.
Testing it:
As non root:
$ sysctl kernel.perf_event_paranoid
kernel.perf_event_paranoid = 2
$ perf record sleep 1
$ perf evlist -v
cycles:uppp: ..., exclude_kernel: 1, ... precise_ip: 3, ...
Now as non-root, but with kernel.perf_event_paranoid set set to the
most permissive value, -1:
$ sysctl kernel.perf_event_paranoid
kernel.perf_event_paranoid = -1
$ perf record sleep 1
$ perf evlist -v
cycles:ppp: ..., exclude_kernel: 0, ... precise_ip: 3, ...
$
I.e. non-root, default kernel.perf_event_paranoid: :uppp modifier = not allowed to sample the kernel,
non-root, most permissible kernel.perf_event_paranoid: :ppp = allowed to sample the kernel.
In both cases, use the highest available precision: attr.precise_ip = 3.
Reported-and-Tested-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: d37a36979077 ("perf evsel: Fix attr.exclude_kernel setting for default cycles:p")
Link: http://lkml.kernel.org/n/tip-nj2qkf75xsd6pw6hhjzfqqdx@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/evsel.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 4bb89373eb52..0dccdb89572c 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -271,12 +271,17 @@ struct perf_evsel *perf_evsel__new_idx(struct perf_event_attr *attr, int idx)
return evsel;
}
+static bool perf_event_can_profile_kernel(void)
+{
+ return geteuid() == 0 || perf_event_paranoid() == -1;
+}
+
struct perf_evsel *perf_evsel__new_cycles(bool precise)
{
struct perf_event_attr attr = {
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
- .exclude_kernel = geteuid() != 0,
+ .exclude_kernel = !perf_event_can_profile_kernel(),
};
struct perf_evsel *evsel;
--
2.13.5
next prev parent reply other threads:[~2017-09-29 16:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-29 16:00 [GIT PULL 0/7] perf/urgent fixes Arnaldo Carvalho de Melo
2017-09-29 16:00 ` [PATCH 1/7] perf tools: Get all of tools/{arch,include}/ in the MANIFEST Arnaldo Carvalho de Melo
2017-09-29 16:00 ` [PATCH 2/7] tools include: Sync kernel ABI headers with tooling headers Arnaldo Carvalho de Melo
2017-09-29 16:00 ` Arnaldo Carvalho de Melo [this message]
2017-09-29 16:00 ` [PATCH 4/7] perf report: Fix debug messages with --call-graph option Arnaldo Carvalho de Melo
2017-09-29 16:00 ` [PATCH 5/7] perf tools: Fix syscalltbl build failure Arnaldo Carvalho de Melo
2017-09-29 16:00 ` [PATCH 6/7] perf test: Fix vmlinux failure on s390x Arnaldo Carvalho de Melo
2017-09-29 16:00 ` [PATCH 7/7] perf test: Fix vmlinux failure on s390x part 2 Arnaldo Carvalho de Melo
2017-09-29 17:33 ` [GIT PULL 0/7] perf/urgent fixes Ingo Molnar
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