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author | Arnaldo Carvalho de Melo <acme@redhat.com> | 2017-09-22 20:41:44 +0200 |
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committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2017-09-25 15:39:45 +0200 |
commit | f1e52f14a69386ac460a8d700df0647a631cf595 (patch) | |
tree | ae6228c6aa1a7d14699c176b82523538eabdeb25 /tools | |
parent | tools include: Sync kernel ABI headers with tooling headers (diff) | |
download | linux-f1e52f14a69386ac460a8d700df0647a631cf595.tar.xz linux-f1e52f14a69386ac460a8d700df0647a631cf595.zip |
perf evsel: Fix attr.exclude_kernel setting for default cycles:p
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>
Diffstat (limited to 'tools')
-rw-r--r-- | tools/perf/util/evsel.c | 7 |
1 files changed, 6 insertions, 1 deletions
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; |