[for-next][PATCH 4/7] tracing: Add method for recording "func_repeats" events

[Steven Rostedt]

From: "Yordan Karadzhov (VMware)" <y.karadz@xxxxxxxxx>

This patch only provides the implementation of the method.
Later we will used it in a combination with a new option for
function tracing.

Link: https://lkml.kernel.org/r/20210415181854.147448-5-y.karadz@xxxxxxxxx

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@xxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c | 34 ++++++++++++++++++++++++++++++++++
 kernel/trace/trace.h |  4 ++++
 2 files changed, 38 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 82833be07c1e..66a4ad93b5e9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3117,6 +3117,40 @@ static void ftrace_trace_userstack(struct trace_array *tr,
 
 #endif /* CONFIG_STACKTRACE */
 
+static inline void
+func_repeats_set_delta_ts(struct func_repeats_entry *entry,
+			  unsigned long long delta)
+{
+	entry->bottom_delta_ts = delta & U32_MAX;
+	entry->top_delta_ts = (delta >> 32);
+}
+
+void trace_last_func_repeats(struct trace_array *tr,
+			     struct trace_func_repeats *last_info,
+			     unsigned int trace_ctx)
+{
+	struct trace_buffer *buffer = tr->array_buffer.buffer;
+	struct func_repeats_entry *entry;
+	struct ring_buffer_event *event;
+	u64 delta;
+
+	event = __trace_buffer_lock_reserve(buffer, TRACE_FUNC_REPEATS,
+					    sizeof(*entry), trace_ctx);
+	if (!event)
+		return;
+
+	delta = ring_buffer_event_time_stamp(buffer, event) -
+		last_info->ts_last_call;
+
+	entry = ring_buffer_event_data(event);
+	entry->ip = last_info->ip;
+	entry->parent_ip = last_info->parent_ip;
+	entry->count = last_info->count;
+	func_repeats_set_delta_ts(entry, delta);
+
+	__buffer_unlock_commit(buffer, event);
+}
+
 /* created for use with alloc_percpu */
 struct trace_buffer_struct {
 	int nesting;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index a4f1b66049fd..cd80d046c7a5 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -695,6 +695,10 @@ static inline void __trace_stack(struct trace_array *tr, unsigned int trace_ctx,
 }
 #endif /* CONFIG_STACKTRACE */
 
+void trace_last_func_repeats(struct trace_array *tr,
+			     struct trace_func_repeats *last_info,
+			     unsigned int trace_ctx);
+
 extern u64 ftrace_now(int cpu);
 
 extern void trace_find_cmdline(int pid, char comm[]);
-- 
2.30.1