[PATCH v1 3/3] perf tool: extend Perf tool with CAP_SYS_PERFMON support

Alexey Budankov
2019-12-05T16:22:31Z

Extend error messages to mention CAP_SYS_PERFMON capability as an option
to substitute CAP_SYS_ADMIN credentials where applicable.

Make perf_event_paranoid_check() to be aware of CAP_SYS_PERFMON in case
perf_event_paranoid value >= 0.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
tools/perf/design.txt | 3 ++-
tools/perf/util/cap.h | 4 ++++
tools/perf/util/evsel.c | 10 +++++-----
tools/perf/util/util.c | 15 +++++++++++++--
4 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index 0453ba26cdbd..71755b3e1303 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -258,7 +258,8 @@ 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_SYS_ADMIN privilege.
+all events on CPU-x. Per CPU counters need CAP_SYS_PERFMON or
+CAP_SYS_ADMIN privilege.

The 'flags' parameter is currently unused and must be zero.

diff --git a/tools/perf/util/cap.h b/tools/perf/util/cap.h
index 051dc590ceee..0f79fbf6638b 100644
--- a/tools/perf/util/cap.h
+++ b/tools/perf/util/cap.h
@@ -29,4 +29,8 @@ static inline bool perf_cap__capable(int cap __maybe_unused)
#define CAP_SYSLOG 34
#endif

+#ifndef CAP_SYS_PERFMON
+#define CAP_SYS_PERFMON 38
+#endif
+
#endif /* __PERF_CAP_H */
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index f4dea055b080..3a46325e3702 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2468,14 +2468,14 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
"You may not have permission to collect %sstats.\n\n"
"Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
"which controls use of the performance events system by\n"
- "unprivileged users (without CAP_SYS_ADMIN).\n\n"
+ "unprivileged users (without CAP_SYS_PERFMON or CAP_SYS_ADMIN).\n\n"
"The current value is %d:\n\n"
" -1: Allow use of (almost) all events by all users\n"
" Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n"
- ">= 0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN\n"
- " Disallow raw tracepoint access by users without CAP_SYS_ADMIN\n"
- ">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n"
- ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN\n\n"
+ ">= 0: Disallow ftrace function tracepoint by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
+ " Disallow raw tracepoint access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
+ ">= 1: Disallow CPU event access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
+ ">= 2: Disallow kernel profiling by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n\n"
"To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n"
" kernel.perf_event_paranoid = -1\n" ,
target->system_wide ? "system-wide " : "",
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 969ae560dad9..d8334fa97c85 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -271,8 +271,19 @@ int perf_event_paranoid(void)

bool perf_event_paranoid_check(int max_level)
{
- return perf_cap__capable(CAP_SYS_ADMIN) ||
- perf_event_paranoid() <= max_level;
+ bool res = false;
+
+ res = perf_cap__capable(CAP_SYS_ADMIN);
+
+ if (!res) {
+ if (max_level >= 0)
+ res = perf_cap__capable(CAP_SYS_PERFMON);
+ }
+
+ if (!res)
+ res = perf_event_paranoid() <= max_level;
+
+ return res;
}

static int
--
2.20.1