Commit 5e9629d0 authored by James Clark's avatar James Clark Committed by Will Deacon
Browse files

drivers/perf: arm_spe: Use perf_allow_kernel() for permissions 



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: default avatarAl Grant <al.grant@arm.com>
Signed-off-by: default avatarJames Clark <james.clark@linaro.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: default avatarWill Deacon <will@kernel.org>
parent db9e7a83

drivers/perf/arm_spe_pmu.c

+4 −5
Original line number Diff line number Diff line
@@ -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;

}
@@ -745,9 +745,8 @@ 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;

}

include/linux/perf_event.h

+1 −7
Original line number Diff line number Diff line
@@ -1602,13 +1602,7 @@ 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)

{

kernel/events/core.c

+9 −0
Original line number Diff line number Diff line
@@ -13351,6 +13351,15 @@ 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.

 *