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Commit 6b099d9b authored by Alexander Shishkin's avatar Alexander Shishkin Committed by Ingo Molnar
Browse files

perf/x86/intel/bts: Fix DS area sharing with x86_pmu events 



Currently, the intel_bts driver relies on the DS area allocated by the x86_pmu
code in its event_init() path, which is a bug: creating a BTS event while
no x86_pmu events are present results in a NULL pointer dereference.

The same DS area is also used by PEBS sampling, which makes it quite a bit
trickier to have a separate one for intel_bts' purposes.

This patch makes intel_bts driver use the same DS allocation and reference
counting code as x86_pmu to make sure it is always present when either
intel_bts or x86_pmu need it.

Signed-off-by: default avatarAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Link: http://lkml.kernel.org/r/1434024837-9916-2-git-send-email-alexander.shishkin@linux.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4b36f1a4

arch/x86/kernel/cpu/perf_event.c

+33 −19
Original line number Diff line number Diff line
@@ -270,11 +270,7 @@ static bool check_hw_exists(void) 


static void hw_perf_event_destroy(struct perf_event *event)

{

	if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {

		release_pmc_hardware();

		release_ds_buffers();

		mutex_unlock(&pmc_reserve_mutex);

	}

	x86_release_hardware();

}



void hw_perf_lbr_event_destroy(struct perf_event *event)
@@ -324,6 +320,35 @@ set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event *event) 
	return x86_pmu_extra_regs(val, event);

}



int x86_reserve_hardware(void)

{

	int err = 0;



	if (!atomic_inc_not_zero(&active_events)) {

		mutex_lock(&pmc_reserve_mutex);

		if (atomic_read(&active_events) == 0) {

			if (!reserve_pmc_hardware())

				err = -EBUSY;

			else

				reserve_ds_buffers();

		}

		if (!err)

			atomic_inc(&active_events);

		mutex_unlock(&pmc_reserve_mutex);

	}



	return err;

}



void x86_release_hardware(void)

{

	if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) {

		release_pmc_hardware();

		release_ds_buffers();

		mutex_unlock(&pmc_reserve_mutex);

	}

}



/*

 * Check if we can create event of a certain type (that no conflicting events

 * are present).
@@ -336,9 +361,10 @@ int x86_add_exclusive(unsigned int what) 
		return 0;



	mutex_lock(&pmc_reserve_mutex);

	for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++)

	for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++) {

		if (i != what && atomic_read(&x86_pmu.lbr_exclusive[i]))

			goto out;

	}



	atomic_inc(&x86_pmu.lbr_exclusive[what]);

	ret = 0;
@@ -527,19 +553,7 @@ static int __x86_pmu_event_init(struct perf_event *event) 
	if (!x86_pmu_initialized())

		return -ENODEV;



	err = 0;

	if (!atomic_inc_not_zero(&active_events)) {

		mutex_lock(&pmc_reserve_mutex);

		if (atomic_read(&active_events) == 0) {

			if (!reserve_pmc_hardware())

				err = -EBUSY;

			else

				reserve_ds_buffers();

		}

		if (!err)

			atomic_inc(&active_events);

		mutex_unlock(&pmc_reserve_mutex);

	}

	err = x86_reserve_hardware();

	if (err)

		return err;

arch/x86/kernel/cpu/perf_event.h

+4 −0
Original line number Diff line number Diff line
@@ -703,6 +703,10 @@ int x86_add_exclusive(unsigned int what); 


void x86_del_exclusive(unsigned int what);



int x86_reserve_hardware(void);



void x86_release_hardware(void);



void hw_perf_lbr_event_destroy(struct perf_event *event);



int x86_setup_perfctr(struct perf_event *event);

arch/x86/kernel/cpu/perf_event_intel_bts.c

+9 −0
Original line number Diff line number Diff line
@@ -483,17 +483,26 @@ static int bts_event_add(struct perf_event *event, int mode) 


static void bts_event_destroy(struct perf_event *event)

{

	x86_release_hardware();

	x86_del_exclusive(x86_lbr_exclusive_bts);

}



static int bts_event_init(struct perf_event *event)

{

	int ret;



	if (event->attr.type != bts_pmu.type)

		return -ENOENT;



	if (x86_add_exclusive(x86_lbr_exclusive_bts))

		return -EBUSY;



	ret = x86_reserve_hardware();

	if (ret) {

		x86_del_exclusive(x86_lbr_exclusive_bts);

		return ret;

	}



	event->destroy = bts_event_destroy;



	return 0;