This patch adds helper bpf_perf_prog_read_time for perf event based bpf
programs, to read event 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 <y...@fb.com>
---
include/linux/perf_event.h | 1 +
include/uapi/linux/bpf.h | 8 ++++++++
kernel/events/core.c | 1 +
kernel/trace/bpf_trace.c | 23 +++++++++++++++++++++++
4 files changed, 33 insertions(+)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 5a50808..6756ae7 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -821,6 +821,7 @@ struct perf_output_handle {
struct bpf_perf_event_data_kern {
struct pt_regs *regs;
struct perf_sample_data *data;
+ struct perf_event *event;
};
#ifdef CONFIG_CGROUP_PERF
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9c23bef..1ae55c8 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -590,6 +590,13 @@ union bpf_attr {
* @counter_time_buf: buf to fill
* @buf_size: size of the counter_time_buf
* Return: 0 on success or negative error code
+ *
+ * int bpf_perf_prog_read_time(ctx, time_buf, buf_size)
+ * Read perf event enabled and running time
+ * @ctx: pointer to ctx
+ * @time_buf: buf to fill
+ * @buf_size: size of the time_buf
+ * Return : 0 on success or negative error code
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -647,6 +654,7 @@ union bpf_attr {
FN(sk_redirect_map), \
FN(sock_map_update), \
FN(perf_read_counter_time), \
+ FN(perf_prog_read_time), \
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 20c4039..338f564 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8026,6 +8026,7 @@ static void bpf_overflow_handler(struct perf_event *event,
struct bpf_perf_event_data_kern ctx = {
.data = data,
.regs = regs,
+ .event = event,
};
int ret = 0;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 7ef953f..89b0744 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -603,6 +603,18 @@ BPF_CALL_3(bpf_get_stackid_tp, void *, tp_buff, struct
bpf_map *, map,
flags, 0, 0);
}
+BPF_CALL_3(bpf_perf_prog_read_time_tp, void *, ctx, struct bpf_perf_time *,
+ time_buf, u32, size)
+{
+ struct bpf_perf_event_data_kern *kctx = (struct
bpf_perf_event_data_kern *)ctx;
+
+ if (size != sizeof(struct bpf_perf_time))
+ return -EINVAL;
+
+ return perf_event_read_local(kctx->event, NULL, &time_buf->enabled,
+ &time_buf->running);
+}
+
static const struct bpf_func_proto bpf_get_stackid_proto_tp = {
.func = bpf_get_stackid_tp,
.gpl_only = true,
@@ -612,6 +624,15 @@ static const struct bpf_func_proto
bpf_get_stackid_proto_tp = {
.arg3_type = ARG_ANYTHING,
};
+static const struct bpf_func_proto bpf_perf_prog_read_time_proto_tp = {
+ .func = bpf_perf_prog_read_time_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) {
@@ -619,6 +640,8 @@ 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_time:
+ return &bpf_perf_prog_read_time_proto_tp;
default:
return tracing_func_proto(func_id);
}
--
2.9.5
