bpf: add helper bpf_perf_prog_read_value

This patch adds helper bpf_perf_prog_read_cvalue for perf event based bpf
programs, to read event counter and enabled/running time.
The enabled/running time is accumulated since the perf event open.

The typical use case for perf event based bpf program is to attach itself
to a single event. In such cases, if it is desirable to get scaling factor
between two bpf invocations, users can can save the time values in a map,
and use the value from the map and the current value to calculate
the scaling factor.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7b57a212c7d7d4ffae3ff6d9fac983af54a15491..5bbbec17aa5a67a9fba94a906e82f78887d7360f 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -649,6 +649,13 @@ union bpf_attr {
  *     @buf: buf to fill
  *     @buf_size: size of the buf
  *     Return: 0 on success or negative error code
+ *
+ * int bpf_perf_prog_read_value(ctx, buf, buf_size)
+ *     read perf prog attached perf event counter and enabled/running time
+ *     @ctx: pointer to ctx
+ *     @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),                     \
@@ -706,7 +713,8 @@ union bpf_attr {
        FN(sk_redirect_map),            \
        FN(sock_map_update),            \
        FN(xdp_adjust_meta),            \
-       FN(perf_event_read_value),
+       FN(perf_event_read_value),      \
+       FN(perf_prog_read_value),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0be86cc0130e78574061a4b6920f19cb751259da..04ea5314f2bc93586b4b29f8c102171ba5968d41 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -613,6 +613,32 @@ static const struct bpf_func_proto bpf_get_stackid_proto_tp = {
        .arg3_type      = ARG_ANYTHING,
 };
 
+BPF_CALL_3(bpf_perf_prog_read_value_tp, struct bpf_perf_event_data_kern *, ctx,
+          struct bpf_perf_event_value *, buf, u32, size)
+{
+       int err = -EINVAL;
+
+       if (unlikely(size != sizeof(struct bpf_perf_event_value)))
+               goto clear;
+       err = perf_event_read_local(ctx->event, &buf->counter, &buf->enabled,
+                                   &buf->running);
+       if (unlikely(err))
+               goto clear;
+       return 0;
+clear:
+       memset(buf, 0, size);
+       return err;
+}
+
+static const struct bpf_func_proto bpf_perf_prog_read_value_proto_tp = {
+         .func           = bpf_perf_prog_read_value_tp,
+         .gpl_only       = true,
+         .ret_type       = RET_INTEGER,
+         .arg1_type      = ARG_PTR_TO_CTX,
+         .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
+         .arg3_type      = ARG_CONST_SIZE,
+};
+
 static const struct bpf_func_proto *tp_prog_func_proto(enum bpf_func_id func_id)
 {
        switch (func_id) {
@@ -620,6 +646,8 @@ static const struct bpf_func_proto *tp_prog_func_proto(enum bpf_func_id func_id)
                return &bpf_perf_event_output_proto_tp;
        case BPF_FUNC_get_stackid:
                return &bpf_get_stackid_proto_tp;
+       case BPF_FUNC_perf_prog_read_value:
+               return &bpf_perf_prog_read_value_proto_tp;
        default:
                return tracing_func_proto(func_id);
        }