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 7b57a21..5bbbec1 100644
--- 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