Commit b326e956 authored by Frederic Weisbecker's avatar Frederic Weisbecker
Browse files

hw-breakpoints: Use overflow handler instead of the event callback 



struct perf_event::event callback was called when a breakpoint
triggers. But this is a rather opaque callback, pretty
tied-only to the breakpoint API and not really integrated into perf
as it triggers even when we don't overflow.

We prefer to use overflow_handler() as it fits into the perf events
rules, being called only when we overflow.

Reported-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>
parent 2f0993e0

arch/x86/kernel/hw_breakpoint.c

+2 −3
Original line number Diff line number Diff line
@@ -362,7 +362,6 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp, 
		return ret;

	}



	if (bp->callback)

	ret = arch_store_info(bp);



	if (ret < 0)
@@ -519,7 +518,7 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args) 
			break;

		}



		(bp->callback)(bp, args->regs);

		perf_bp_event(bp, args->regs);



		rcu_read_unlock();

	}

arch/x86/kernel/ptrace.c

+6 −3
Original line number Diff line number Diff line
@@ -555,7 +555,9 @@ static int genregs_set(struct task_struct *target, 
	return ret;

}



static void ptrace_triggered(struct perf_event *bp, void *data)

static void ptrace_triggered(struct perf_event *bp, int nmi,

			     struct perf_sample_data *data,

			     struct pt_regs *regs)

{

	int i;

	struct thread_struct *thread = &(current->thread);
@@ -599,7 +601,7 @@ ptrace_modify_breakpoint(struct perf_event *bp, int len, int type, 
{

	int err;

	int gen_len, gen_type;

	DEFINE_BREAKPOINT_ATTR(attr);

	struct perf_event_attr attr;



	/*

	 * We shoud have at least an inactive breakpoint at this
@@ -721,9 +723,10 @@ static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr, 
{

	struct perf_event *bp;

	struct thread_struct *t = &tsk->thread;

	DEFINE_BREAKPOINT_ATTR(attr);

	struct perf_event_attr attr;



	if (!t->ptrace_bps[nr]) {

		hw_breakpoint_init(&attr);

		/*

		 * Put stub len and type to register (reserve) an inactive but

		 * correct bp

include/linux/hw_breakpoint.h

+11 −14
Original line number Diff line number Diff line
@@ -20,19 +20,16 @@ enum { 


#ifdef CONFIG_HAVE_HW_BREAKPOINT



/* As it's for in-kernel or ptrace use, we want it to be pinned */

#define DEFINE_BREAKPOINT_ATTR(name)	\

struct perf_event_attr name = {		\

	.type = PERF_TYPE_BREAKPOINT,	\

	.size = sizeof(name),		\

	.pinned = 1,			\

};



static inline void hw_breakpoint_init(struct perf_event_attr *attr)

{

	attr->type = PERF_TYPE_BREAKPOINT;

	attr->size = sizeof(*attr);

	/*

	 * As it's for in-kernel or ptrace use, we want it to be pinned

	 * and to call its callback every hits.

	 */

	attr->pinned = 1;

	attr->sample_period = 1;

}



static inline unsigned long hw_breakpoint_addr(struct perf_event *bp)
@@ -52,7 +49,7 @@ static inline int hw_breakpoint_len(struct perf_event *bp) 


extern struct perf_event *

register_user_hw_breakpoint(struct perf_event_attr *attr,

			    perf_callback_t triggered,

			    perf_overflow_handler_t triggered,

			    struct task_struct *tsk);



/* FIXME: only change from the attr, and don't unregister */
@@ -64,12 +61,12 @@ modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr); 
 */

extern struct perf_event *

register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,

				perf_callback_t triggered,

				perf_overflow_handler_t	triggered,

				int cpu);



extern struct perf_event **

register_wide_hw_breakpoint(struct perf_event_attr *attr,

			    perf_callback_t triggered);

			    perf_overflow_handler_t triggered);



extern int register_perf_hw_breakpoint(struct perf_event *bp);

extern int __register_perf_hw_breakpoint(struct perf_event *bp);
@@ -90,18 +87,18 @@ static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp) 


static inline struct perf_event *

register_user_hw_breakpoint(struct perf_event_attr *attr,

			    perf_callback_t triggered,

			    perf_overflow_handler_t triggered,

			    struct task_struct *tsk)	{ return NULL; }

static inline struct perf_event *

modify_user_hw_breakpoint(struct perf_event *bp,

			  struct perf_event_attr *attr)	{ return NULL; }

static inline struct perf_event *

register_wide_hw_breakpoint_cpu(struct perf_event_attr *attr,

				perf_callback_t triggered,

				perf_overflow_handler_t	 triggered,

				int cpu)		{ return NULL; }

static inline struct perf_event **

register_wide_hw_breakpoint(struct perf_event_attr *attr,

			    perf_callback_t triggered)	{ return NULL; }

			    perf_overflow_handler_t triggered)	{ return NULL; }

static inline int

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

static inline int

include/linux/perf_event.h

+7 −6
Original line number Diff line number Diff line
@@ -565,10 +565,13 @@ struct perf_pending_entry { 
	void (*func)(struct perf_pending_entry *);

};



typedef void (*perf_callback_t)(struct perf_event *, void *);



struct perf_sample_data;



typedef void (*perf_callback_t)(struct perf_event *, void *);

typedef void (*perf_overflow_handler_t)(struct perf_event *, int,

					struct perf_sample_data *,

					struct pt_regs *regs);



/**

 * struct perf_event - performance event kernel representation:

 */
@@ -660,9 +663,7 @@ struct perf_event { 
	struct pid_namespace		*ns;

	u64				id;



	void (*overflow_handler)(struct perf_event *event,

			int nmi, struct perf_sample_data *data,

			struct pt_regs *regs);

	perf_overflow_handler_t		overflow_handler;



#ifdef CONFIG_EVENT_PROFILE

	struct event_filter		*filter;
@@ -779,7 +780,7 @@ extern struct perf_event * 
perf_event_create_kernel_counter(struct perf_event_attr *attr,

				int cpu,

				pid_t pid,

				perf_callback_t callback);

				perf_overflow_handler_t callback);

extern u64 perf_event_read_value(struct perf_event *event,

				 u64 *enabled, u64 *running);

kernel/hw_breakpoint.c

+5 −12
Original line number Diff line number Diff line
@@ -259,7 +259,7 @@ void release_bp_slot(struct perf_event *bp) 
}





int __register_perf_hw_breakpoint(struct perf_event *bp)

int register_perf_hw_breakpoint(struct perf_event *bp)

{

	int ret;
@@ -276,19 +276,12 @@ int __register_perf_hw_breakpoint(struct perf_event *bp) 
	 * This is a quick hack that will be removed soon, once we remove

	 * the tmp breakpoints from ptrace

	 */

	if (!bp->attr.disabled || bp->callback == perf_bp_event)

	if (!bp->attr.disabled || !bp->overflow_handler)

		ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);



	return ret;

}



int register_perf_hw_breakpoint(struct perf_event *bp)

{

	bp->callback = perf_bp_event;



	return __register_perf_hw_breakpoint(bp);

}



/**

 * register_user_hw_breakpoint - register a hardware breakpoint for user space

 * @attr: breakpoint attributes
@@ -297,7 +290,7 @@ int register_perf_hw_breakpoint(struct perf_event *bp) 
 */

struct perf_event *

register_user_hw_breakpoint(struct perf_event_attr *attr,

			    perf_callback_t triggered,

			    perf_overflow_handler_t triggered,

			    struct task_struct *tsk)

{

	return perf_event_create_kernel_counter(attr, -1, tsk->pid, triggered);
@@ -322,7 +315,7 @@ modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr) 
	unregister_hw_breakpoint(bp);



	return perf_event_create_kernel_counter(attr, -1, bp->ctx->task->pid,

						bp->callback);

						bp->overflow_handler);

}

EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
@@ -347,7 +340,7 @@ EXPORT_SYMBOL_GPL(unregister_hw_breakpoint); 
 */

struct perf_event **

register_wide_hw_breakpoint(struct perf_event_attr *attr,

			    perf_callback_t triggered)

			    perf_overflow_handler_t triggered)

{

	struct perf_event **cpu_events, **pevent, *bp;

	long err;

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