[RFC PATCH v3 1/2] tracing: Add new trace type for bpf data output

[He Kuang <hekuang@huawei.com>]

Add TRACE_BPF as a new trace type to establish infrastruction for bpf
output data to perf. This new trace type creates a static singleton
ftrace entry in kernel, userspace perf tools can detect and use this
new ftrace entry just as using the existing tracepoint events.

This added a new bpf ftrace entry in debugfs:

     /sys/kernel/debug/tracing/events/ftrace/bpf

Userspace perf tools detect the new tracepoint event as:

     ftrace:bpf                          [Tracepoint event]

Data in ring-buffer of perf events added to this ftrace:bpf event can
be polled out, sample types and other attributes can be adjusted to
those events directly without touching the original kprobe events.

Signed-off-by: He Kuang <hekuang@huawei.com>
---
 kernel/trace/trace.h         |  1 +
 kernel/trace/trace_entries.h | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index d261201..d135f55 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -38,6 +38,7 @@ enum trace_type {
 	TRACE_USER_STACK,
 	TRACE_BLK,
 	TRACE_BPUTS,
+	TRACE_BPF,
 
 	__TRACE_LAST_TYPE,
 };
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index ee7b94a..c237212 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -322,3 +322,21 @@ FTRACE_ENTRY(branch, trace_branch,
 	FILTER_OTHER
 );
 
+#define TRACE_BPF_MAX_ENTRY	64
+#define TRACE_BPF_MAX_SIZE	(TRACE_BPF_MAX_ENTRY * sizeof(u64))
+
+FTRACE_ENTRY_REG(bpf, trace_bpf,
+
+	TRACE_BPF,
+
+	F_STRUCT(
+		__field(long,	size)
+		__array(u64,	raw_data,	TRACE_BPF_MAX_ENTRY)
+	),
+
+	F_printk("%ld: (%016llx, ...)", __entry->size, __entry->raw_data[0]),
+
+	FILTER_OTHER,
+
+	perf_ftrace_event_register
+);
-- 
1.8.5.2