Re: [RFC 0/4] perf: Per PMU access controls (paranoid setting)

[Jiri Olsa <jolsa@redhat.com>]

On Tue, Jun 26, 2018 at 04:36:38PM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> For situations where sysadmins might want to allow different level of
> access control for different PMUs, we start creating per-PMU
> perf_event_paranoid controls in sysfs.
> 
> These work in equivalent fashion as the existing perf_event_paranoid
> sysctl, which now becomes the parent control for each PMU.
> 
> On PMU registration the global/parent value will be inherited by each PMU,
> as it will be propagated to all registered PMUs when the sysctl is
> updated.
> 
> At any later point individual PMU access controls, located in
> <sysfs>/device/<pmu-name>/perf_event_paranoid, can be adjusted to achieve
> fine grained access control.
> 
> Discussion from previous posting:
> https://lkml.org/lkml/2018/5/21/156
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: x86@kernel.org
> 
> Tvrtko Ursulin (4):
>   perf: Move some access checks later in perf_event_open
>   perf: Pass pmu pointer to perf_paranoid_* helpers
>   perf: Allow per PMU access control
>   perf Documentation: Document the per PMU perf_event_paranoid interface

I think we'll need some perf tool changes for this

apart from the hint/docs, that checks/display paranoid value,
I think we need some changes in arch related code like below
(untested)

jirka


---
diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index 2f595cd73da6..a5437f100ab9 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -69,7 +69,7 @@ static int cs_etm_recording_options(struct auxtrace_record *itr,
 	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
 	struct perf_evsel *evsel, *cs_etm_evsel = NULL;
 	const struct cpu_map *cpus = evlist->cpus;
-	bool privileged = (geteuid() == 0 || perf_event_paranoid() < 0);
+	bool privileged = (geteuid() == 0 || cs_etm_pmu->paranoid < 0);
 
 	ptr->evlist = evlist;
 	ptr->snapshot_mode = opts->auxtrace_snapshot_mode;
diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
index 1120e39c1b00..89d3d27ed8be 100644
--- a/tools/perf/arch/arm64/util/arm-spe.c
+++ b/tools/perf/arch/arm64/util/arm-spe.c
@@ -65,7 +65,7 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
 			container_of(itr, struct arm_spe_recording, itr);
 	struct perf_pmu *arm_spe_pmu = sper->arm_spe_pmu;
 	struct perf_evsel *evsel, *arm_spe_evsel = NULL;
-	bool privileged = geteuid() == 0 || perf_event_paranoid() < 0;
+	bool privileged = geteuid() == 0 || arm_spe_pmu->paranoid < 0;
 	struct perf_evsel *tracking_evsel;
 	int err;
 
diff --git a/tools/perf/arch/x86/util/intel-bts.c b/tools/perf/arch/x86/util/intel-bts.c
index 781df40b2966..c97e6556c8e7 100644
--- a/tools/perf/arch/x86/util/intel-bts.c
+++ b/tools/perf/arch/x86/util/intel-bts.c
@@ -116,7 +116,7 @@ static int intel_bts_recording_options(struct auxtrace_record *itr,
 	struct perf_pmu *intel_bts_pmu = btsr->intel_bts_pmu;
 	struct perf_evsel *evsel, *intel_bts_evsel = NULL;
 	const struct cpu_map *cpus = evlist->cpus;
-	bool privileged = geteuid() == 0 || perf_event_paranoid() < 0;
+	bool privileged = geteuid() == 0 || intel_bts_pmu->paranoid < 0;
 
 	btsr->evlist = evlist;
 	btsr->snapshot_mode = opts->auxtrace_snapshot_mode;
diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index db0ba8caf5a2..ffbe5f7f1c57 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -555,7 +555,7 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
 	bool have_timing_info, need_immediate = false;
 	struct perf_evsel *evsel, *intel_pt_evsel = NULL;
 	const struct cpu_map *cpus = evlist->cpus;
-	bool privileged = geteuid() == 0 || perf_event_paranoid() < 0;
+	bool privileged = geteuid() == 0 || intel_pt_pmu->paranoid < 0;
 	u64 tsc_bit;
 	int err;
 
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index d2fb597c9a8c..f2a91305a8b6 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -450,6 +450,20 @@ static int pmu_type(const char *name, __u32 *type)
 	return ret;
 }
 
+static int pmu_paranoid(const char *name)
+{
+	char path[PATH_MAX];
+	int paranoid;
+
+	snprintf(path, PATH_MAX,
+                 EVENT_SOURCE_DEVICE_PATH "%s/perf_event_paranoid", name);
+
+	if (!sysfs__read_int(EVENT_SOURCE_DEVICE_PATH, &paranoid))
+		return paranoid;
+
+	return perf_event_paranoid();
+}
+
 /* Add all pmus in sysfs to pmu list: */
 static void pmu_read_sysfs(void)
 {
@@ -736,6 +750,7 @@ static struct perf_pmu *pmu_lookup(const char *name)
 	pmu->name = strdup(name);
 	pmu->type = type;
 	pmu->is_uncore = pmu_is_uncore(name);
+	pmu->paranoid = pmu_paranoid(name);
 	pmu_add_cpu_aliases(&aliases, pmu);
 
 	INIT_LIST_HEAD(&pmu->format);
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 76fecec7b3f9..1f00c8bbdb90 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -30,6 +30,7 @@ struct perf_pmu {
 	struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
 	struct list_head list;    /* ELEM */
 	int (*set_drv_config)	(struct perf_evsel_config_term *term);
+	int paranoid;
 };
 
 struct perf_pmu_info {