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Subject[PATCH v2 3/4] perf tool: make Perf tool aware of SELinux access control
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Date

Implement SELinux sysfs check to see if the system is in enforcing
mode and print warning message with pointers to check audit logs.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
tools/perf/util/cloexec.c | 4 ++--
tools/perf/util/evsel.c | 40 +++++++++++++++++++++++----------------
2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index a12872f2856a..9c8ec816261b 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -65,7 +65,7 @@ static int perf_flag_probe(void)
return 1;
}

- WARN_ONCE(err != EINVAL && err != EBUSY,
+ WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES,
"perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
err, str_error_r(err, sbuf, sizeof(sbuf)));

@@ -83,7 +83,7 @@ static int perf_flag_probe(void)
if (fd >= 0)
close(fd);

- if (WARN_ONCE(fd < 0 && err != EBUSY,
+ if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES,
"perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
err, str_error_r(err, sbuf, sizeof(sbuf))))
return -1;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 9fa92649adb4..82492ca12405 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2514,32 +2514,40 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
int err, char *msg, size_t size)
{
char sbuf[STRERR_BUFSIZE];
- int printed = 0;
+ int printed = 0, enforced = 0;

switch (err) {
case EPERM:
case EACCES:
+ printed += scnprintf(msg + printed, size - printed,
+ "Access to performance monitoring and observability operations is limited.\n");
+
+ if (!sysfs__read_int("fs/selinux/enforce", &enforced)) {
+ if (enforced) {
+ printed += scnprintf(msg + printed, size - printed,
+ "Enforced MAC policy settings (SELinux) can limit access to performance\n"
+ "monitoring and observability operations. Inspect system audit records for\n"
+ "more perf_event access control information and adjusting the policy.\n");
+ }
+ }
+
if (err == EPERM)
- printed = scnprintf(msg, size,
- "No permission to enable %s event.\n\n",
+ printed += scnprintf(msg, size,
+ "No permission to enable %s event.\n",
perf_evsel__name(evsel));

return scnprintf(msg + printed, size - printed,
- "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_PERFMON or CAP_SYS_ADMIN).\n\n"
- "The current value is %d:\n\n"
+ "Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open\n"
+ "access to performance monitoring and observability operations for users\n"
+ "without CAP_PERFMON capability. perf_event_paranoid setting is %d:\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_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_PERFMON or CAP_SYS_ADMIN\n"
- ">= 2: Disallow kernel profiling by users without CAP_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 " : "",
- perf_event_paranoid());
+ ">= 0: Disallow raw and ftrace function tracepoint access\n"
+ ">= 1: Disallow CPU event access\n"
+ ">= 2: Disallow kernel profiling\n"
+ "To make the adjusted perf_event_paranoid setting permanent preserve it\n"
+ "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)",
+ perf_event_paranoid());
case ENOENT:
return scnprintf(msg, size, "The %s event is not supported.",
perf_evsel__name(evsel));
--
2.24.1

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