Re: [PATCH net-next v4 1/4] bpf: add helper bpf_perf_event_read_value for perf event array map

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 43ab5c4..2c68b9e 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h

@@ -582,6 +582,14 @@ union bpf_attr {
   *	@map: pointer to sockmap to update
   *	@key: key to insert/update sock in map
   *	@flags: same flags as map update elem
+ *
+ * int bpf_perf_event_read_value(map, flags, buf, buf_size)
+ *     read perf event counter value and perf event enabled/running time
+ *     @map: pointer to perf_event_array map
+ *     @flags: index of event in the map or bitmask flags
+ *     @buf: buf to fill
+ *     @buf_size: size of the buf
+ *     Return: 0 on success or negative error code
   */
  #define __BPF_FUNC_MAPPER(FN)		\
  	FN(unspec),			\

@@ -638,6 +646,7 @@ union bpf_attr {
  	FN(redirect_map),		\
  	FN(sk_redirect_map),		\
  	FN(sock_map_update),		\
+	FN(perf_event_read_value),		\

  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
   * function eBPF program intends to call

@@ -681,7 +690,8 @@ enum bpf_func_id {
  #define BPF_F_ZERO_CSUM_TX		(1ULL << 1)
  #define BPF_F_DONT_FRAGMENT		(1ULL << 2)

-/* BPF_FUNC_perf_event_output and BPF_FUNC_perf_event_read flags. */
+/* BPF_FUNC_perf_event_output, BPF_FUNC_perf_event_read and
+ * BPF_FUNC_perf_event_read_value flags. */

  #define BPF_F_INDEX_MASK		0xffffffffULL
  #define BPF_F_CURRENT_CPU		BPF_F_INDEX_MASK
  /* BPF_FUNC_perf_event_output for sk_buff input context. */

@@ -864,4 +874,10 @@ enum {
  #define TCP_BPF_IW		1001	/* Set TCP initial congestion window */
  #define TCP_BPF_SNDCWND_CLAMP	1002	/* Set sndcwnd_clamp */

+struct bpf_perf_event_value {
+	__u64 counter;
+	__u64 enabled;
+	__u64 running;
+};
+

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3e691b7..2d5bbe5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c

@@ -3684,10 +3684,12 @@ static inline u64 perf_event_count(struct perf_event *event)
   *     will not be local and we cannot read them atomically
   *   - must not have a pmu::count method
   */
-int perf_event_read_local(struct perf_event *event, u64 *value)
+int perf_event_read_local(struct perf_event *event, u64 *value,
+			  u64 *enabled, u64 *running)
  {
  	unsigned long flags;
  	int ret = 0;
+	u64 now;

  	/*
  	 * Disabling interrupts avoids all counter scheduling (context

@@ -3718,14 +3720,21 @@ int perf_event_read_local(struct perf_event *event, u64 *value)
  		goto out;
  	}

+	now = event->shadow_ctx_time + perf_clock();
+	if (enabled)
+		*enabled = now - event->tstamp_enabled;
  	/*
  	 * If the event is currently on this CPU, its either a per-task event,
  	 * or local to this CPU. Furthermore it means its ACTIVE (otherwise
  	 * oncpu == -1).
  	 */
-	if (event->oncpu == smp_processor_id())
+	if (event->oncpu == smp_processor_id()) {
  		event->pmu->read(event);
-
+		if (running)
+			*running = now - event->tstamp_running;
+	} else if (running) {
+		*running = event->total_time_running;
+	}
  	*value = local64_read(&event->count);
  out:
  	local_irq_restore(flags);

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index dc498b6..39ce5d9 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

@@ -255,13 +255,13 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
  	return &bpf_trace_printk_proto;
  }

-BPF_CALL_2(bpf_perf_event_read, struct bpf_map *, map, u64, flags)
-{
+static __always_inline int
+get_map_perf_counter(struct bpf_map *map, u64 flags,
+		u64 *value, u64 *enabled, u64 *running) {

  	struct bpf_array *array = container_of(map, struct bpf_array, map);
  	unsigned int cpu = smp_processor_id();
  	u64 index = flags & BPF_F_INDEX_MASK;
  	struct bpf_event_entry *ee;
-	u64 value = 0;
  	int err;

  	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))

@@ -275,7 +275,17 @@ BPF_CALL_2(bpf_perf_event_read, struct bpf_map *, map, u64, flags)
  	if (!ee)
  		return -ENOENT;

-	err = perf_event_read_local(ee->event, &value);
+	err = perf_event_read_local(ee->event, value, enabled, running);
+	return err;

+BPF_CALL_2(bpf_perf_event_read, struct bpf_map *, map, u64, flags)
+{
+	u64 value = 0;
+	int err;
+
+	err = get_map_perf_counter(map, flags, &value, NULL, NULL);
  	/*
  	 * this api is ugly since we miss [-22..-2] range of valid
  	 * counter values, but that's uapi

@@ -285,6 +295,20 @@ BPF_CALL_2(bpf_perf_event_read, struct bpf_map *, map, u64, flags)
  	return value;
  }

+}
+
  static const struct bpf_func_proto bpf_perf_event_read_proto = {
  	.func		= bpf_perf_event_read,
  	.gpl_only	= true,

@@ -293,6 +317,16 @@ static const struct bpf_func_proto bpf_perf_event_read_proto = {
  	.arg2_type	= ARG_ANYTHING,
  };

+static const struct bpf_func_proto bpf_perf_event_read_value_proto = {
+	.func		= bpf_perf_event_read_value,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_PTR_TO_UNINIT_MEM,

+	.arg4_type	= ARG_CONST_SIZE,
+};
+
  static DEFINE_PER_CPU(struct perf_sample_data, bpf_sd);

  static __always_inline u64

@@ -499,6 +533,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
  		return &bpf_perf_event_output_proto;
  	case BPF_FUNC_get_stackid:
  		return &bpf_get_stackid_proto;
+	case BPF_FUNC_perf_event_read_value:
+		return &bpf_perf_event_read_value_proto;
  	default:
  		return tracing_func_proto(func_id);
  	}