tracing: Sample module to demonstrate kernel access to Ftrace instances. (89ed4249) · Commits · 戴 / test

samples/Kconfig

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		@@ -27,6 +27,13 @@ config SAMPLE_FTRACE_DIRECT
		This builds an ftrace direct function example
		that hooks to wake_up_process and prints the parameters.

		config SAMPLE_TRACE_ARRAY
		tristate "Build sample module for kernel access to Ftrace instancess"
		depends on EVENT_TRACING && m
		help
		This builds a module that demonstrates the use of various APIs to
		access Ftrace instances from within the kernel.

		config SAMPLE_KOBJECT
		tristate "Build kobject examples"
		help

samples/Makefile

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		@@ -18,6 +18,7 @@ subdir-$(CONFIG_SAMPLE_SECCOMP) += seccomp
		obj-$(CONFIG_SAMPLE_TRACE_EVENTS) += trace_events/
		obj-$(CONFIG_SAMPLE_TRACE_PRINTK) += trace_printk/
		obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace/
		obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += ftrace/
		obj-$(CONFIG_VIDEO_PCI_SKELETON) += v4l/
		obj-y += vfio-mdev/
		subdir-$(CONFIG_SAMPLE_VFS) += vfs

samples/ftrace/Makefile

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		@@ -3,3 +3,6 @@
		obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct.o
		obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-too.o
		obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-modify.o

		CFLAGS_sample-trace-array.o := -I$(src)
		obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += sample-trace-array.o

samples/ftrace/sample-trace-array.c

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		// SPDX-License-Identifier: GPL-2.0-only
		#include <linux/module.h>
		#include <linux/kthread.h>
		#include <linux/trace.h>
		#include <linux/trace_events.h>
		#include <linux/timer.h>
		#include <linux/err.h>
		#include <linux/jiffies.h>

		/*
		* Any file that uses trace points, must include the header.
		* But only one file, must include the header by defining
		* CREATE_TRACE_POINTS first. This will make the C code that
		* creates the handles for the trace points.
		*/
		#define CREATE_TRACE_POINTS
		#include "sample-trace-array.h"

		struct trace_array *tr;
		static void mytimer_handler(struct timer_list *unused);
		static struct task_struct *simple_tsk;

		/*
		* mytimer: Timer setup to disable tracing for event "sample_event". This
		* timer is only for the purposes of the sample module to demonstrate access of
		* Ftrace instances from within kernel.
		*/
		static DEFINE_TIMER(mytimer, mytimer_handler);

		static void mytimer_handler(struct timer_list *unused)
		{
		/*
		* Disable tracing for event "sample_event".
		*/
		trace_array_set_clr_event(tr, "sample-subsystem", "sample_event",
		false);
		}

		static void simple_thread_func(int count)
		{
		set_current_state(TASK_INTERRUPTIBLE);
		schedule_timeout(HZ);

		/*
		* Printing count value using trace_array_printk() - trace_printk()
		* equivalent for the instance buffers.
		*/
		trace_array_printk(tr, _THIS_IP_, "trace_array_printk: count=%d\n",
		count);
		/*
		* Tracepoint for event "sample_event". This will print the
		* current value of count and current jiffies.
		*/
		trace_sample_event(count, jiffies);
		}

		static int simple_thread(void *arg)
		{
		int count = 0;
		unsigned long delay = msecs_to_jiffies(5000);

		/*
		* Enable tracing for "sample_event".
		*/
		trace_array_set_clr_event(tr, "sample-subsystem", "sample_event", true);

		/*
		* Adding timer - mytimer. This timer will disable tracing after
		* delay seconds.
		*
		*/
		add_timer(&mytimer);
		mod_timer(&mytimer, jiffies+delay);

		while (!kthread_should_stop())
		simple_thread_func(count++);

		del_timer(&mytimer);

		/*
		* trace_array_put() decrements the reference counter associated with
		* the trace array - "tr". We are done using the trace array, hence
		* decrement the reference counter so that it can be destroyed using
		* trace_array_destroy().
		*/
		trace_array_put(tr);

		return 0;
		}

		static int __init sample_trace_array_init(void)
		{
		/*
		* Return a pointer to the trace array with name "sample-instance" if it
		* exists, else create a new trace array.
		*
		* NOTE: This function increments the reference counter
		* associated with the trace array - "tr".
		*/
		tr = trace_array_get_by_name("sample-instance");

		if (!tr)
		return -1;
		/*
		* If context specific per-cpu buffers havent already been allocated.
		*/
		trace_printk_init_buffers();

		simple_tsk = kthread_run(simple_thread, NULL, "sample-instance");
		if (IS_ERR(simple_tsk))
		return -1;
		return 0;
		}

		static void __exit sample_trace_array_exit(void)
		{
		kthread_stop(simple_tsk);

		/*
		* We are unloading our module and no longer require the trace array.
		* Remove/destroy "tr" using trace_array_destroy()
		*/
		trace_array_destroy(tr);
		}

		module_init(sample_trace_array_init);
		module_exit(sample_trace_array_exit);

		MODULE_AUTHOR("Divya Indi");
		MODULE_DESCRIPTION("Sample module for kernel access to Ftrace instances");
		MODULE_LICENSE("GPL");

samples/ftrace/sample-trace-array.h

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		/* SPDX-License-Identifier: GPL-2.0 */

		/*
		* If TRACE_SYSTEM is defined, that will be the directory created
		* in the ftrace directory under /sys/kernel/tracing/events/<system>
		*
		* The define_trace.h below will also look for a file name of
		* TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
		* In this case, it would look for sample-trace.h
		*
		* If the header name will be different than the system name
		* (as in this case), then you can override the header name that
		* define_trace.h will look up by defining TRACE_INCLUDE_FILE
		*
		* This file is called sample-trace-array.h but we want the system
		* to be called "sample-subsystem". Therefore we must define the name of this
		* file:
		*
		* #define TRACE_INCLUDE_FILE sample-trace-array
		*
		* As we do in the bottom of this file.
		*
		* Notice that TRACE_SYSTEM should be defined outside of #if
		* protection, just like TRACE_INCLUDE_FILE.
		*/
		#undef TRACE_SYSTEM
		#define TRACE_SYSTEM sample-subsystem

		/*
		* TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric
		* and underscore), although it may start with numbers. If for some
		* reason it is not, you need to add the following lines:
		*/
		#undef TRACE_SYSTEM_VAR
		#define TRACE_SYSTEM_VAR sample_subsystem

		/*
		* But the above is only needed if TRACE_SYSTEM is not alpha-numeric
		* and underscored. By default, TRACE_SYSTEM_VAR will be equal to
		* TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if
		* TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with
		* only alpha-numeric and underscores.
		*
		* The TRACE_SYSTEM_VAR is only used internally and not visible to
		* user space.
		*/

		/*
		* Notice that this file is not protected like a normal header.
		* We also must allow for rereading of this file. The
		*
		* \|\| defined(TRACE_HEADER_MULTI_READ)
		*
		* serves this purpose.
		*/
		#if !defined(_SAMPLE_TRACE_ARRAY_H) \|\| defined(TRACE_HEADER_MULTI_READ)
		#define _SAMPLE_TRACE_ARRAY_H

		#include <linux/tracepoint.h>
		TRACE_EVENT(sample_event,

		TP_PROTO(int count, unsigned long time),

		TP_ARGS(count, time),

		TP_STRUCT__entry(
		__field(int, count)
		__field(unsigned long, time)
		),

		TP_fast_assign(
		__entry->count = count;
		__entry->time = time;
		),

		TP_printk("count value=%d at jiffies=%lu", __entry->count,
		__entry->time)
		);
		#endif

		#undef TRACE_INCLUDE_PATH
		#define TRACE_INCLUDE_PATH .
		#define TRACE_INCLUDE_FILE sample-trace-array
		#include <trace/define_trace.h>

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