[PATCH V3 1/2] bpf: control the trace data output on current cpu when perf sampling

@@ -472,6 +472,7 @@ struct perf_event {
 	struct irq_work			pending;
 
 	atomic_t			event_limit;
+	atomic_t			dump_enable;
 
 	void (*destroy)(struct perf_event *);
 	struct rcu_head			rcu_head;

@@ -287,6 +287,11 @@ enum bpf_func_id {
 	 * Return: realm if != 0
 	 */
 	BPF_FUNC_get_route_realm,
+
+	/**
+	 * u64 bpf_perf_event_dump_control(&map, index, flag)
+	 */
+	BPF_FUNC_perf_event_dump_control,
 	__BPF_FUNC_MAX_ID,
 };
 

@@ -331,7 +331,8 @@ struct perf_event_attr {
 				comm_exec      :  1, /* flag comm events that are due to an exec */
 				use_clockid    :  1, /* use @clockid for time fields */
 				context_switch :  1, /* context switch data */
-				__reserved_1   : 37;
+				dump_enable    :  1, /* don't output data on samples */
+				__reserved_1   : 36;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */

@@ -245,6 +245,7 @@ static const struct {
 } func_limit[] = {
 	{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
 	{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
+	{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_dump_control},
 };
 
 static void print_verifier_state(struct verifier_env *env)

@@ -910,7 +911,7 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
 		 * don't allow any other map type to be passed into
 		 * the special func;
 		 */
-		if (bool_map != bool_func)
+		if (bool_func && bool_map != bool_func)
 			return -EINVAL;
 	}
 

@@ -6337,6 +6337,9 @@ static int __perf_event_overflow(struct perf_event *event,
 		irq_work_queue(&event->pending);
 	}
 
+	if (!atomic_read(&event->dump_enable))
+		return ret;
+
 	if (event->overflow_handler)
 		event->overflow_handler(event, data, regs);
 	else

@@ -7709,6 +7712,14 @@ static void account_event(struct perf_event *event)
 	account_event_cpu(event, event->cpu);
 }
 
+static void perf_event_check_dump_flag(struct perf_event *event)
+{
+	if (event->attr.dump_enable == 1)
+		atomic_set(&event->dump_enable, 1);
+	else
+		atomic_set(&event->dump_enable, 0);
+}
+
 /*
  * Allocate and initialize a event structure
  */

@@ -7840,6 +7851,8 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 		}
 	}
 
+	perf_event_check_dump_flag(event);
+
 	return event;
 
 err_per_task:

@@ -215,6 +215,48 @@ const struct bpf_func_proto bpf_perf_event_read_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+/* flags for PERF_EVENT_ARRAY maps*/
+enum {
+	PERF_EVENT_CTL_BIT_DUMP = 0,
+	_NR_PERF_EVENT_CTL_BITS,
+};
+
+#define	BIT_FLAG_CHECK	GENMASK_ULL(63, _NR_PERF_EVENT_CTL_BITS)
+#define	BIT_DUMP_CTL	BIT_ULL(PERF_EVENT_CTL_BIT_DUMP)
+
+static u64 bpf_perf_event_dump_control(u64 r1, u64 index, u64 flag, u64 r4, u64 r5)
+{
+	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
+	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	struct perf_event *event;
+
+	if (unlikely(index >= array->map.max_entries))
+		return -E2BIG;
+
+	if (flag & BIT_FLAG_CHECK)
+		return -EINVAL;
+
+	event = (struct perf_event *)array->ptrs[index];
+	if (!event)
+		return -ENOENT;
+
+	if (flag & BIT_DUMP_CTL)
+		atomic_dec_if_positive(&event->dump_enable);
+	else
+		atomic_inc_unless_negative(&event->dump_enable);
+
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_perf_event_dump_control_proto = {
+	.func		= bpf_perf_event_dump_control,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
 {
 	switch (func_id) {

@@ -242,6 +284,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
 		return &bpf_get_smp_processor_id_proto;
 	case BPF_FUNC_perf_event_read:
 		return &bpf_perf_event_read_proto;
+	case BPF_FUNC_perf_event_dump_control:
+		return &bpf_perf_event_dump_control_proto;
 	default:
 		return NULL;
 	}