linux-kernel - [PATCH v4 07/24] tracing: Add helpers to create trace remote events

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Message-ID: <20250506164820.515876-8-vdonnefort@google.com>
Date: Tue,  6 May 2025 17:48:03 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
To: rostedt@...dmis.org, mhiramat@...nel.org, mathieu.desnoyers@...icios.com, 
	linux-trace-kernel@...r.kernel.org, maz@...nel.org, oliver.upton@...ux.dev, 
	joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	jstultz@...gle.com, qperret@...gle.com, will@...nel.org, 
	kernel-team@...roid.com, linux-kernel@...r.kernel.org, 
	Vincent Donnefort <vdonnefort@...gle.com>
Subject: [PATCH v4 07/24] tracing: Add helpers to create trace remote events

Declaring remote events can be cumbersome let's add a set of macros to
simplify developers life. The declaration of a remote event is very
similar to kernel's events:

 REMOTE_EVENT(name, id,
     RE_STRUCT(
        re_field(u64 foo)
     ),
     RE_PRINTK("foo=%llu", __entry->foo)
 )

Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>

diff --git a/include/linux/trace_remote_event.h b/include/linux/trace_remote_event.h
index 621c5dff0664..d00e85d2a633 100644
--- a/include/linux/trace_remote_event.h
+++ b/include/linux/trace_remote_event.h
@@ -5,6 +5,7 @@
 
 struct trace_remote;
 struct trace_event_fields;
+struct trace_seq;
 
 struct remote_event_hdr {
 	unsigned short	id;
@@ -20,4 +21,13 @@ struct remote_event {
 	char				*print_fmt;
 	void				(*print)(void *evt, struct trace_seq *seq);
 };
+
+#define RE_STRUCT(__args...) __args
+#define re_field(__type, __field) __type __field;
+
+#define REMOTE_EVENT_FORMAT(__name, __struct)	\
+	struct remote_event_format_##__name {	\
+		struct remote_event_hdr hdr;	\
+		__struct			\
+	}
 #endif
diff --git a/include/trace/define_remote_events.h b/include/trace/define_remote_events.h
new file mode 100644
index 000000000000..03c9f5515c5a
--- /dev/null
+++ b/include/trace/define_remote_events.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/trace_events.h>
+#include <linux/trace_remote_event.h>
+#include <linux/trace_seq.h>
+#include <linux/stringify.h>
+
+#define REMOTE_EVENT_INCLUDE(__file) __stringify(../../__file)
+
+#ifdef REMOTE_EVENT_SECTION
+# define __REMOTE_EVENT_SECTION(__name) __used __section(REMOTE_EVENT_SECTION"."#__name)
+#else
+# define __REMOTE_EVENT_SECTION(__name)
+#endif
+
+#define __REMOTE_PRINTK_COUNT_ARGS(_0, _1, _2, _n, __args...) _n
+#define REMOTE_PRINTK_COUNT_ARGS(__args...) __REMOTE_PRINTK_COUNT_ARGS(, ##__args, 2, 1, 0)
+
+#define __remote_printk0()								\
+	trace_seq_putc(seq, '\n')
+
+#define __remote_printk1(__fmt)								\
+	trace_seq_puts(seq, " " __fmt "\n")						\
+
+#define __remote_printk2(__fmt, __args...)						\
+do {											\
+	trace_seq_putc(seq, ' ');							\
+	trace_seq_printf(seq, __fmt, __args);						\
+	trace_seq_putc(seq, '\n');							\
+} while (0)
+
+/* Apply the appropriate trace_seq sequence according to the number of arguments */
+#define remote_printk(__args...)							\
+	CONCATENATE(__remote_printk, REMOTE_PRINTK_COUNT_ARGS(__args))(__args)
+
+#define RE_PRINTK(__args...) __args
+
+#define REMOTE_EVENT(__name, __id, __struct, __printk)					\
+	REMOTE_EVENT_FORMAT(__name, __struct);						\
+	static void remote_event_print_##__name(void *evt, struct trace_seq *seq)	\
+	{										\
+		struct remote_event_format_##__name __maybe_unused *__entry = evt;	\
+		trace_seq_puts(seq, #__name);						\
+		remote_printk(__printk);						\
+	}
+#include REMOTE_EVENT_INCLUDE(REMOTE_EVENT_INCLUDE_FILE)
+
+#undef REMOTE_EVENT
+#undef RE_PRINTK
+#undef re_field
+#define re_field(__type, __field)							\
+	{										\
+		.type = #__type, .name = #__field,					\
+		.size = sizeof(__type), .align = __alignof__(__type),			\
+		.is_signed = is_signed_type(__type),					\
+	},
+#define __entry REC
+#define RE_PRINTK(__fmt, __args...) "\"" __fmt "\", " __stringify(__args)
+#define REMOTE_EVENT(__name, __id, __struct, __printk)					\
+	static struct trace_event_fields remote_event_fields_##__name[] = {		\
+		__struct								\
+		{}									\
+	};										\
+	static char remote_event_print_fmt_##__name[] = __printk;			\
+	static struct remote_event __REMOTE_EVENT_SECTION(__name)			\
+	remote_event_##__name = {							\
+		.name		= #__name,						\
+		.id		= __id,							\
+		.fields		= remote_event_fields_##__name,				\
+		.print_fmt	= remote_event_print_fmt_##__name,			\
+		.print		= remote_event_print_##__name,				\
+	}
+#include REMOTE_EVENT_INCLUDE(REMOTE_EVENT_INCLUDE_FILE)
-- 
2.49.0.967.g6a0df3ecc3-goog