[PATCH 4/4 v2] tracing: Add TRACE_CUSTOM_EVENT() macro
From: Steven Rostedt
Date: Thu Mar 03 2022 - 16:49:39 EST
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
To make it really easy to add custom events from modules, add a
TRACE_CUSTOM_EVENT() macro that acts just like the TRACE_EVENT() macro,
but creates a custom event to an already existing tracepoint.
The trace_custom_sched.[ch] has been updated to use this new macro to show
how simple it is.
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
include/linux/trace_events.h | 24 +-
samples/trace_events/Makefile | 2 +-
samples/trace_events/trace_custom_sched.c | 259 ++--------------------
samples/trace_events/trace_custom_sched.h | 95 ++++++++
4 files changed, 143 insertions(+), 237 deletions(-)
create mode 100644 samples/trace_events/trace_custom_sched.h
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index dcea51fb60e2..6c7ae3c2ba9b 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -315,6 +315,7 @@ enum {
TRACE_EVENT_FL_KPROBE_BIT,
TRACE_EVENT_FL_UPROBE_BIT,
TRACE_EVENT_FL_EPROBE_BIT,
+ TRACE_EVENT_FL_CUSTOM_BIT,
};
/*
@@ -328,6 +329,9 @@ enum {
* KPROBE - Event is a kprobe
* UPROBE - Event is a uprobe
* EPROBE - Event is an event probe
+ * CUSTOM - Event is a custom event (to be attached to an exsiting tracepoint)
+ * This is set when the custom event has not been attached
+ * to a tracepoint yet, then it is cleared when it is.
*/
enum {
TRACE_EVENT_FL_FILTERED = (1 << TRACE_EVENT_FL_FILTERED_BIT),
@@ -339,6 +343,7 @@ enum {
TRACE_EVENT_FL_KPROBE = (1 << TRACE_EVENT_FL_KPROBE_BIT),
TRACE_EVENT_FL_UPROBE = (1 << TRACE_EVENT_FL_UPROBE_BIT),
TRACE_EVENT_FL_EPROBE = (1 << TRACE_EVENT_FL_EPROBE_BIT),
+ TRACE_EVENT_FL_CUSTOM = (1 << TRACE_EVENT_FL_CUSTOM_BIT),
};
#define TRACE_EVENT_FL_UKPROBE (TRACE_EVENT_FL_KPROBE | TRACE_EVENT_FL_UPROBE)
@@ -440,7 +445,9 @@ static inline bool bpf_prog_array_valid(struct trace_event_call *call)
static inline const char *
trace_event_name(struct trace_event_call *call)
{
- if (call->flags & TRACE_EVENT_FL_TRACEPOINT)
+ if (call->flags & TRACE_EVENT_FL_CUSTOM)
+ return call->name;
+ else if (call->flags & TRACE_EVENT_FL_TRACEPOINT)
return call->tp ? call->tp->name : NULL;
else
return call->name;
@@ -903,3 +910,18 @@ perf_trace_buf_submit(void *raw_data, int size, int rctx, u16 type,
#endif
#endif /* _LINUX_TRACE_EVENT_H */
+
+/*
+ * Note: we keep the TRACE_CUSTOM_EVENT outside the include file ifdef protection.
+ * This is due to the way trace custom events work. If a file includes two
+ * trace event headers under one "CREATE_CUSTOM_TRACE_EVENTS" the first include
+ * will override the TRACE_CUSTOM_EVENT and break the second include.
+ */
+
+#ifndef TRACE_CUSTOM_EVENT
+
+#define DECLARE_CUSTOM_EVENT_CLASS(name, proto, args, tstruct, assign, print)
+#define DEFINE_CUSTOM_EVENT(template, name, proto, args)
+#define TRACE_CUSTOM_EVENT(name, proto, args, struct, assign, print)
+
+#endif /* ifdef TRACE_CUSTOM_EVENT (see note above) */
diff --git a/samples/trace_events/Makefile b/samples/trace_events/Makefile
index e98afc447fe1..b3808bb4cf8b 100644
--- a/samples/trace_events/Makefile
+++ b/samples/trace_events/Makefile
@@ -11,7 +11,7 @@
# Here trace-events-sample.c does the CREATE_TRACE_POINTS.
#
CFLAGS_trace-events-sample.o := -I$(src)
+CFLAGS_trace_custom_sched.o := -I$(src)
obj-$(CONFIG_SAMPLE_TRACE_EVENTS) += trace-events-sample.o
-
obj-$(CONFIG_SAMPLE_TRACE_CUSTOM_EVENTS) += trace_custom_sched.o
diff --git a/samples/trace_events/trace_custom_sched.c b/samples/trace_events/trace_custom_sched.c
index 70a12c32ff99..b99d9ab7db85 100644
--- a/samples/trace_events/trace_custom_sched.c
+++ b/samples/trace_events/trace_custom_sched.c
@@ -11,256 +11,45 @@
#include <linux/version.h>
#include <linux/module.h>
#include <linux/sched.h>
-#include <trace/events/sched.h>
-
-#define THIS_SYSTEM "custom_sched"
-
-#define SCHED_PRINT_FMT \
- C("prev_prio=%d next_pid=%d next_prio=%d", REC->prev_prio, REC->next_pid, \
- REC->next_prio)
-
-#define SCHED_WAKING_FMT \
- C("pid=%d prio=%d", REC->pid, REC->prio)
-
-#undef C
-#define C(a, b...) a, b
-
-static struct trace_event_fields sched_switch_fields[] = {
- {
- .type = "unsigned short",
- .name = "prev_prio",
- .size = sizeof(short),
- .align = __alignof__(short),
- .is_signed = 0,
- .filter_type = FILTER_OTHER,
- },
- {
- .type = "unsigned short",
- .name = "next_prio",
- .size = sizeof(short),
- .align = __alignof__(short),
- .is_signed = 0,
- .filter_type = FILTER_OTHER,
- },
- {
- .type = "unsigned int",
- .name = "next_prio",
- .size = sizeof(int),
- .align = __alignof__(int),
- .is_signed = 0,
- .filter_type = FILTER_OTHER,
- },
- {}
-};
-
-struct sched_event {
- struct trace_entry ent;
- unsigned short prev_prio;
- unsigned short next_prio;
- unsigned int next_pid;
-};
-
-static struct trace_event_fields sched_waking_fields[] = {
- {
- .type = "unsigned int",
- .name = "pid",
- .size = sizeof(int),
- .align = __alignof__(int),
- .is_signed = 0,
- .filter_type = FILTER_OTHER,
- },
- {
- .type = "unsigned short",
- .name = "prio",
- .size = sizeof(short),
- .align = __alignof__(short),
- .is_signed = 0,
- .filter_type = FILTER_OTHER,
- },
- {}
-};
-
-struct wake_event {
- struct trace_entry ent;
- unsigned int pid;
- unsigned short prio;
-};
-
-static void sched_switch_probe(void *data, bool preempt, struct task_struct *prev,
- struct task_struct *next)
-{
- struct trace_event_file *trace_file = data;
- struct trace_event_buffer fbuffer;
- struct sched_event *entry;
-
- if (trace_trigger_soft_disabled(trace_file))
- return;
-
- entry = trace_event_buffer_reserve(&fbuffer, trace_file,
- sizeof(*entry));
-
- if (!entry)
- return;
-
- entry->prev_prio = prev->prio;
- entry->next_prio = next->prio;
- entry->next_pid = next->pid;
-
- trace_event_buffer_commit(&fbuffer);
-}
-
-static struct trace_event_class sched_switch_class = {
- .system = THIS_SYSTEM,
- .reg = trace_event_reg,
- .fields_array = sched_switch_fields,
- .fields = LIST_HEAD_INIT(sched_switch_class.fields),
- .probe = sched_switch_probe,
-};
-
-static void sched_waking_probe(void *data, struct task_struct *t)
-{
- struct trace_event_file *trace_file = data;
- struct trace_event_buffer fbuffer;
- struct wake_event *entry;
-
- if (trace_trigger_soft_disabled(trace_file))
- return;
-
- entry = trace_event_buffer_reserve(&fbuffer, trace_file,
- sizeof(*entry));
-
- if (!entry)
- return;
-
- entry->prio = t->prio;
- entry->pid = t->pid;
-
- trace_event_buffer_commit(&fbuffer);
-}
-
-static struct trace_event_class sched_waking_class = {
- .system = THIS_SYSTEM,
- .reg = trace_event_reg,
- .fields_array = sched_waking_fields,
- .fields = LIST_HEAD_INIT(sched_waking_class.fields),
- .probe = sched_waking_probe,
-};
-
-static enum print_line_t sched_switch_output(struct trace_iterator *iter, int flags,
- struct trace_event *trace_event)
-{
- struct trace_seq *s = &iter->seq;
- struct sched_event *REC = (struct sched_event *)iter->ent;
- int ret;
-
- ret = trace_raw_output_prep(iter, trace_event);
- if (ret != TRACE_TYPE_HANDLED)
- return ret;
-
- trace_seq_printf(s, SCHED_PRINT_FMT);
- trace_seq_putc(s, '\n');
- return trace_handle_return(s);
-}
-
-static struct trace_event_functions sched_switch_funcs = {
- .trace = sched_switch_output,
-};
-
-static enum print_line_t sched_waking_output(struct trace_iterator *iter, int flags,
- struct trace_event *trace_event)
-{
- struct trace_seq *s = &iter->seq;
- struct wake_event *REC = (struct wake_event *)iter->ent;
- int ret;
-
- ret = trace_raw_output_prep(iter, trace_event);
- if (ret != TRACE_TYPE_HANDLED)
- return ret;
-
- trace_seq_printf(s, SCHED_WAKING_FMT);
- trace_seq_putc(s, '\n');
-
- return trace_handle_return(s);
-}
-
-static struct trace_event_functions sched_waking_funcs = {
- .trace = sched_waking_output,
-};
-
-#undef C
-#define C(a, b...) #a "," __stringify(b)
+/*
+ * Must include the event header that the custom event will attach to,
+ * from the C file, and not in the custom header file.
+ */
+#include <trace/events/sched.h>
-static struct trace_event_call sched_switch_call = {
- .class = &sched_switch_class,
- .event = {
- .funcs = &sched_switch_funcs,
- },
- .print_fmt = SCHED_PRINT_FMT,
- .module = THIS_MODULE,
- .flags = TRACE_EVENT_FL_TRACEPOINT,
-};
+/* Declare CREATE_CUSTOM_TRACE_EVENTS before including custom header */
+#define CREATE_CUSTOM_TRACE_EVENTS
-static struct trace_event_call sched_waking_call = {
- .class = &sched_waking_class,
- .event = {
- .funcs = &sched_waking_funcs,
- },
- .print_fmt = SCHED_WAKING_FMT,
- .module = THIS_MODULE,
- .flags = TRACE_EVENT_FL_TRACEPOINT,
-};
+#include "trace_custom_sched.h"
+/*
+ * As the trace events are not exported to modules, the use of
+ * for_each_kernel_tracepoint() is needed to find the trace event
+ * to attach to. The fct() function below, is a callback that
+ * will be called for every event.
+ *
+ * Helper functions are created by the TRACE_CUSTOM_EVENT() macro
+ * update the event. Those are of the form:
+ *
+ * trace_custom_event_<event>_update()
+ *
+ * Where <event> is the event to attach.
+ */
static void fct(struct tracepoint *tp, void *priv)
{
- if (tp->name && strcmp(tp->name, "sched_switch") == 0)
- sched_switch_call.tp = tp;
- else if (tp->name && strcmp(tp->name, "sched_waking") == 0)
- sched_waking_call.tp = tp;
-}
-
-static int add_event(struct trace_event_call *call)
-{
- int ret;
-
- ret = register_trace_event(&call->event);
- if (WARN_ON(!ret))
- return -ENODEV;
-
- ret = trace_add_event_call(call);
- if (WARN_ON(ret))
- unregister_trace_event(&call->event);
-
- return ret;
+ trace_custom_event_sched_switch_update(tp);
+ trace_custom_event_sched_waking_update(tp);
}
static int __init trace_sched_init(void)
{
- int ret;
-
- check_trace_callback_type_sched_switch(sched_switch_probe);
- check_trace_callback_type_sched_waking(sched_waking_probe);
-
for_each_kernel_tracepoint(fct, NULL);
-
- ret = add_event(&sched_switch_call);
- if (ret)
- return ret;
-
- ret = add_event(&sched_waking_call);
- if (ret)
- trace_remove_event_call(&sched_switch_call);
-
- return ret;
+ return 0;
}
static void __exit trace_sched_exit(void)
{
- trace_set_clr_event(THIS_SYSTEM, "sched_switch", 0);
- trace_set_clr_event(THIS_SYSTEM, "sched_waking", 0);
-
- trace_remove_event_call(&sched_switch_call);
- trace_remove_event_call(&sched_waking_call);
}
module_init(trace_sched_init);
diff --git a/samples/trace_events/trace_custom_sched.h b/samples/trace_events/trace_custom_sched.h
new file mode 100644
index 000000000000..a3d14de6a2e5
--- /dev/null
+++ b/samples/trace_events/trace_custom_sched.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Like the headers that use TRACE_EVENT(), the TRACE_CUSTOM_EVENT()
+ * needs a header that allows for multiple inclusions.
+ *
+ * Test for a unique name (here we have _TRACE_CUSTOM_SCHED_H),
+ * also allowing to continue if TRACE_CUSTOM_MULTI_READ is defined.
+ */
+#if !defined(_TRACE_CUSTOM_SCHED_H) || defined(TRACE_CUSTOM_MULTI_READ)
+#define _TRACE_CUSTOM_SCHED_H
+
+/* Include linux/trace_events.h for initial defines of TRACE_CUSTOM_EVENT() */
+#include <linux/trace_events.h>
+
+/*
+ * TRACE_CUSTOM_EVENT() is just like TRACE_EVENT(). The first parameter
+ * is the event name of an existing event where the TRACE_EVENT has been included
+ * in the C file before including this file.
+ */
+TRACE_CUSTOM_EVENT(sched_switch,
+
+ /*
+ * The TP_PROTO() and TP_ARGS must match the trace event
+ * that the custom event is using.
+ */
+ TP_PROTO(bool preempt,
+ struct task_struct *prev,
+ struct task_struct *next),
+
+ TP_ARGS(preempt, prev, next),
+
+ /*
+ * The next fields are where the customization happens.
+ * The TP_STRUCT__entry() defines what will be recorded
+ * in the ring buffer when the custom event triggers.
+ *
+ * The rest is just like the TRACE_EVENT() macro except that
+ * it uses the custom entry.
+ */
+ TP_STRUCT__entry(
+ __field( unsigned short, prev_prio )
+ __field( unsigned short, next_prio )
+ __field( pid_t, next_pid )
+ ),
+
+ TP_fast_assign(
+ __entry->prev_prio = prev->prio;
+ __entry->next_pid = next->pid;
+ __entry->next_prio = next->prio;
+ ),
+
+ TP_printk("prev_prio=%d next_pid=%d next_prio=%d",
+ __entry->prev_prio, __entry->next_pid, __entry->next_prio)
+)
+
+
+TRACE_CUSTOM_EVENT(sched_waking,
+
+ TP_PROTO(struct task_struct *p),
+
+ TP_ARGS(p),
+
+ TP_STRUCT__entry(
+ __field( pid_t, pid )
+ __field( unsigned short, prio )
+ ),
+
+ TP_fast_assign(
+ __entry->pid = p->pid;
+ __entry->prio = p->prio;
+ ),
+
+ TP_printk("pid=%d prio=%d", __entry->pid, __entry->prio)
+)
+#endif
+/*
+ * Just like the headers that create TRACE_EVENTs, the below must
+ * be outside the protection of the above #if block.
+ */
+
+/*
+ * It is required that the Makefile includes:
+ * CFLAGS_<c_file>.o := -I$(src)
+ */
+#undef TRACE_INCLUDE_PATH
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_PATH .
+
+/*
+ * It is requred that the TRACE_INCLUDE_FILE be the same
+ * as this file without the ".h".
+ */
+#define TRACE_INCLUDE_FILE trace_custom_sched
+#include <trace/define_custom_trace.h>
--
2.34.1