Commit c5b81449 authored by Marco Elver's avatar Marco Elver Committed by Peter Zijlstra
Browse files

perf/hw_breakpoint: Provide hw_breakpoint_is_used() and use in test 



Provide hw_breakpoint_is_used() to check if breakpoints are in use on
the system.

Use it in the KUnit test to verify the global state before and after a
test case.

Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Acked-by: default avatarIan Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20220829124719.675715-3-elver@google.com
parent 724c299c

include/linux/hw_breakpoint.h

+3 −0
Original line number Diff line number Diff line
@@ -74,6 +74,7 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr, 
extern int register_perf_hw_breakpoint(struct perf_event *bp);

extern void unregister_hw_breakpoint(struct perf_event *bp);

extern void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events);

extern bool hw_breakpoint_is_used(void);



extern int dbg_reserve_bp_slot(struct perf_event *bp);

extern int dbg_release_bp_slot(struct perf_event *bp);
@@ -121,6 +122,8 @@ register_perf_hw_breakpoint(struct perf_event *bp) { return -ENOSYS; } 
static inline void unregister_hw_breakpoint(struct perf_event *bp)	{ }

static inline void

unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)	{ }

static inline bool hw_breakpoint_is_used(void)		{ return false; }



static inline int

reserve_bp_slot(struct perf_event *bp)			{return -ENOSYS; }

static inline void release_bp_slot(struct perf_event *bp) 		{ }

kernel/events/hw_breakpoint.c

+29 −0
Original line number Diff line number Diff line
@@ -604,6 +604,35 @@ void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events) 
}

EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);



/**

 * hw_breakpoint_is_used - check if breakpoints are currently used

 *

 * Returns: true if breakpoints are used, false otherwise.

 */

bool hw_breakpoint_is_used(void)

{

	int cpu;



	if (!constraints_initialized)

		return false;



	for_each_possible_cpu(cpu) {

		for (int type = 0; type < TYPE_MAX; ++type) {

			struct bp_cpuinfo *info = get_bp_info(cpu, type);



			if (info->cpu_pinned)

				return true;



			for (int slot = 0; slot < nr_slots[type]; ++slot) {

				if (info->tsk_pinned[slot])

					return true;

			}

		}

	}



	return false;

}



static struct notifier_block hw_breakpoint_exceptions_nb = {

	.notifier_call = hw_breakpoint_exceptions_notify,

	/* we need to be notified first */

kernel/events/hw_breakpoint_test.c

+11 −1
Original line number Diff line number Diff line
@@ -294,7 +294,14 @@ static struct kunit_case hw_breakpoint_test_cases[] = { 
static int test_init(struct kunit *test)

{

	/* Most test cases want 2 distinct CPUs. */

	return num_online_cpus() < 2 ? -EINVAL : 0;

	if (num_online_cpus() < 2)

		return -EINVAL;



	/* Want the system to not use breakpoints elsewhere. */

	if (hw_breakpoint_is_used())

		return -EBUSY;



	return 0;

}



static void test_exit(struct kunit *test)
@@ -308,6 +315,9 @@ static void test_exit(struct kunit *test) 
		kthread_stop(__other_task);

		__other_task = NULL;

	}



	/* Verify that internal state agrees that no breakpoints are in use. */

	KUNIT_EXPECT_FALSE(test, hw_breakpoint_is_used());

}



static struct kunit_suite hw_breakpoint_test_suite = {