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 <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 | 28 ++++++++++++++++++++++++++++
4 files changed, 38 insertions(+)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 21d8c12..79b18a2 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -806,6 +806,7 @@ 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 ccfe1b1..f3eeae2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -590,6 +590,13 @@ 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), \
@@ -647,6 +654,7 @@ union bpf_attr {
FN(sk_redirect_map), \
FN(sock_map_update), \
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/events/core.c b/kernel/events/core.c
index 2d5bbe5..d039086 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8081,6 +8081,7 @@ 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 686dfa1..c4d617a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -612,6 +612,32 @@ 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;
+
+ if (unlikely(size != sizeof(struct bpf_perf_event_value)))
+ return -EINVAL;
+
+ err = perf_event_read_local(ctx->event, &buf->counter, &buf->enabled,
+ &buf->running);
+ if (unlikely(err)) {
+ memset(buf, 0, size);
+ return err;
+ }
+ return 0;
+}
+
+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) {
@@ -619,6 +645,8 @@ 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);
}
--
2.9.5
