linux-kernel - [PATCH AUTOSEL 6.6 049/139] drivers/perf: arm_spe: Use perf_allow

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Message-ID: <20240925121137.1307574-49-sashal@kernel.org>
Date: Wed, 25 Sep 2024 08:07:49 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: James Clark <james.clark@...aro.org>,
	Al Grant <al.grant@....com>,
	Will Deacon <will@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	mark.rutland@....com,
	peterz@...radead.org,
	mingo@...hat.com,
	acme@...nel.org,
	namhyung@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 049/139] drivers/perf: arm_spe: Use perf_allow_kernel() for permissions

From: James Clark <james.clark@...aro.org>

[ Upstream commit 5e9629d0ae977d6f6916d7e519724804e95f0b07 ]

Use perf_allow_kernel() for 'pa_enable' (physical addresses),
'pct_enable' (physical timestamps) and context IDs. This means that
perf_event_paranoid is now taken into account and LSM hooks can be used,
which is more consistent with other perf_event_open calls. For example
PERF_SAMPLE_PHYS_ADDR uses perf_allow_kernel() rather than just
perfmon_capable().

This also indirectly fixes the following error message which is
misleading because perf_event_paranoid is not taken into account by
perfmon_capable():

  $ perf record -e arm_spe/pa_enable/

  Error:
  Access to performance monitoring and observability operations is
  limited. Consider adjusting /proc/sys/kernel/perf_event_paranoid
  setting ...

Suggested-by: Al Grant <al.grant@....com>
Signed-off-by: James Clark <james.clark@...aro.org>
Link: https://lore.kernel.org/r/20240827145113.1224604-1-james.clark@linaro.org
Link: https://lore.kernel.org/all/20240807120039.GD37996@noisy.programming.kicks-ass.net/
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/perf/arm_spe_pmu.c | 9 ++++-----
 include/linux/perf_event.h | 8 +-------
 kernel/events/core.c       | 9 +++++++++
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index d2b0cbf0e0c41..2bec2e3af0bd6 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -41,7 +41,7 @@
 
 /*
  * Cache if the event is allowed to trace Context information.
- * This allows us to perform the check, i.e, perfmon_capable(),
+ * This allows us to perform the check, i.e, perf_allow_kernel(),
  * in the context of the event owner, once, during the event_init().
  */
 #define SPE_PMU_HW_FLAGS_CX			0x00001
@@ -50,7 +50,7 @@ static_assert((PERF_EVENT_FLAG_ARCH & SPE_PMU_HW_FLAGS_CX) == SPE_PMU_HW_FLAGS_C
 
 static void set_spe_event_has_cx(struct perf_event *event)
 {
-	if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && perfmon_capable())
+	if (IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR) && !perf_allow_kernel(&event->attr))
 		event->hw.flags |= SPE_PMU_HW_FLAGS_CX;
 }
 
@@ -767,9 +767,8 @@ static int arm_spe_pmu_event_init(struct perf_event *event)
 
 	set_spe_event_has_cx(event);
 	reg = arm_spe_event_to_pmscr(event);
-	if (!perfmon_capable() &&
-	    (reg & (PMSCR_EL1_PA | PMSCR_EL1_PCT)))
-		return -EACCES;
+	if (reg & (PMSCR_EL1_PA | PMSCR_EL1_PCT))
+		return perf_allow_kernel(&event->attr);
 
 	return 0;
 }
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 95d4118ee4a91..7a5563ffe61b5 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1599,13 +1599,7 @@ static inline int perf_is_paranoid(void)
 	return sysctl_perf_event_paranoid > -1;
 }
 
-static inline int perf_allow_kernel(struct perf_event_attr *attr)
-{
-	if (sysctl_perf_event_paranoid > 1 && !perfmon_capable())
-		return -EACCES;
-
-	return security_perf_event_open(attr, PERF_SECURITY_KERNEL);
-}
+int perf_allow_kernel(struct perf_event_attr *attr);
 
 static inline int perf_allow_cpu(struct perf_event_attr *attr)
 {
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4d0abdace4e7c..d40809bdf4b30 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -13330,6 +13330,15 @@ const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
 	return &event->attr;
 }
 
+int perf_allow_kernel(struct perf_event_attr *attr)
+{
+	if (sysctl_perf_event_paranoid > 1 && !perfmon_capable())
+		return -EACCES;
+
+	return security_perf_event_open(attr, PERF_SECURITY_KERNEL);
+}
+EXPORT_SYMBOL_GPL(perf_allow_kernel);
+
 /*
  * Inherit an event from parent task to child task.
  *
-- 
2.43.0