Commit 64836248 authored by Tom Zanussi's avatar Tom Zanussi Committed by Steven Rostedt (VMware)
Browse files

tracing: Add kprobe event command generation test module 

Add a test module that checks the basic functionality of the in-kernel
kprobe event command generation API by creating kprobe events from a
module.

Link: http://lkml.kernel.org/r/97e502b204f9dba948e3fa3a4315448298218787.1580323897.git.zanussi@kernel.org



Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarTom Zanussi <zanussi@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 29a15481

kernel/trace/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -787,6 +787,18 @@ config SYNTH_EVENT_GEN_TEST 


	  If unsure, say N.



config KPROBE_EVENT_GEN_TEST

	tristate "Test module for in-kernel kprobe event generation"

	depends on KPROBE_EVENTS

	help

          This option creates a test module to check the base

          functionality of in-kernel kprobe event definition.



          To test, insert the module, and then check the trace buffer

	  for the generated kprobe events.



	  If unsure, say N.



config TRACE_EVAL_MAP_FILE

       bool "Show eval mappings for trace events"

       depends on TRACING

kernel/trace/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ obj-$(CONFIG_TRACING) += trace_printk.o 
obj-$(CONFIG_TRACING_MAP) += tracing_map.o

obj-$(CONFIG_PREEMPTIRQ_DELAY_TEST) += preemptirq_delay_test.o

obj-$(CONFIG_SYNTH_EVENT_GEN_TEST) += synth_event_gen_test.o

obj-$(CONFIG_KPROBE_EVENT_GEN_TEST) += kprobe_event_gen_test.o

obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o

obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o

obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o

kernel/trace/kprobe_event_gen_test.c

0 → 100644
+225 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * Test module for in-kernel kprobe event creation and generation.

 *

 * Copyright (C) 2019 Tom Zanussi <zanussi@kernel.org>

 */



#include <linux/module.h>

#include <linux/trace_events.h>



/*

 * This module is a simple test of basic functionality for in-kernel

 * kprobe/kretprobe event creation.  The first test uses

 * kprobe_event_gen_cmd_start(), kprobe_event_add_fields() and

 * kprobe_event_gen_cmd_end() to create a kprobe event, which is then

 * enabled in order to generate trace output.  The second creates a

 * kretprobe event using kretprobe_event_gen_cmd_start() and

 * kretprobe_event_gen_cmd_end(), and is also then enabled.

 *

 * To test, select CONFIG_KPROBE_EVENT_GEN_TEST and build the module.

 * Then:

 *

 * # insmod kernel/trace/kprobe_event_gen_test.ko

 * # cat /sys/kernel/debug/tracing/trace

 *

 * You should see many instances of the "gen_kprobe_test" and

 * "gen_kretprobe_test" events in the trace buffer.

 *

 * To remove the events, remove the module:

 *

 * # rmmod kprobe_event_gen_test

 *

 */



static struct trace_event_file *gen_kprobe_test;

static struct trace_event_file *gen_kretprobe_test;



/*

 * Test to make sure we can create a kprobe event, then add more

 * fields.

 */

static int __init test_gen_kprobe_cmd(void)

{

	struct dynevent_cmd cmd;

	char *buf;

	int ret;



	/* Create a buffer to hold the generated command */

	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;



	/* Before generating the command, initialize the cmd object */

	kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);



	/*

	 * Define the gen_kprobe_test event with the first 2 kprobe

	 * fields.

	 */

	ret = kprobe_event_gen_cmd_start(&cmd, "gen_kprobe_test",

					 "do_sys_open",

					 "dfd=%ax", "filename=%dx");

	if (ret)

		goto free;



	/* Use kprobe_event_add_fields to add the rest of the fields */



	ret = kprobe_event_add_fields(&cmd, "flags=%cx", "mode=+4($stack)");

	if (ret)

		goto free;



	/*

	 * This actually creates the event.

	 */

	ret = kprobe_event_gen_cmd_end(&cmd);

	if (ret)

		goto free;



	/*

	 * Now get the gen_kprobe_test event file.  We need to prevent

	 * the instance and event from disappearing from underneath

	 * us, which trace_get_event_file() does (though in this case

	 * we're using the top-level instance which never goes away).

	 */

	gen_kprobe_test = trace_get_event_file(NULL, "kprobes",

					       "gen_kprobe_test");

	if (IS_ERR(gen_kprobe_test)) {

		ret = PTR_ERR(gen_kprobe_test);

		goto delete;

	}



	/* Enable the event or you won't see anything */

	ret = trace_array_set_clr_event(gen_kprobe_test->tr,

					"kprobes", "gen_kprobe_test", true);

	if (ret) {

		trace_put_event_file(gen_kprobe_test);

		goto delete;

	}

 out:

	return ret;

 delete:

	/* We got an error after creating the event, delete it */

	ret = kprobe_event_delete("gen_kprobe_test");

 free:

	kfree(buf);



	goto out;

}



/*

 * Test to make sure we can create a kretprobe event.

 */

static int __init test_gen_kretprobe_cmd(void)

{

	struct dynevent_cmd cmd;

	char *buf;

	int ret;



	/* Create a buffer to hold the generated command */

	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;



	/* Before generating the command, initialize the cmd object */

	kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);



	/*

	 * Define the kretprobe event.

	 */

	ret = kretprobe_event_gen_cmd_start(&cmd, "gen_kretprobe_test",

					    "do_sys_open",

					    "$retval");

	if (ret)

		goto free;



	/*

	 * This actually creates the event.

	 */

	ret = kretprobe_event_gen_cmd_end(&cmd);

	if (ret)

		goto free;



	/*

	 * Now get the gen_kretprobe_test event file.  We need to

	 * prevent the instance and event from disappearing from

	 * underneath us, which trace_get_event_file() does (though in

	 * this case we're using the top-level instance which never

	 * goes away).

	 */

	gen_kretprobe_test = trace_get_event_file(NULL, "kprobes",

						  "gen_kretprobe_test");

	if (IS_ERR(gen_kretprobe_test)) {

		ret = PTR_ERR(gen_kretprobe_test);

		goto delete;

	}



	/* Enable the event or you won't see anything */

	ret = trace_array_set_clr_event(gen_kretprobe_test->tr,

					"kprobes", "gen_kretprobe_test", true);

	if (ret) {

		trace_put_event_file(gen_kretprobe_test);

		goto delete;

	}

 out:

	return ret;

 delete:

	/* We got an error after creating the event, delete it */

	ret = kprobe_event_delete("gen_kretprobe_test");

 free:

	kfree(buf);



	goto out;

}



static int __init kprobe_event_gen_test_init(void)

{

	int ret;



	ret = test_gen_kprobe_cmd();

	if (ret)

		return ret;



	ret = test_gen_kretprobe_cmd();

	if (ret) {

		WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,

						  "kprobes",

						  "gen_kretprobe_test", false));

		trace_put_event_file(gen_kretprobe_test);

		WARN_ON(kprobe_event_delete("gen_kretprobe_test"));

	}



	return ret;

}



static void __exit kprobe_event_gen_test_exit(void)

{

	/* Disable the event or you can't remove it */

	WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,

					  "kprobes",

					  "gen_kprobe_test", false));



	/* Now give the file and instance back */

	trace_put_event_file(gen_kprobe_test);



	/* Now unregister and free the event */

	WARN_ON(kprobe_event_delete("gen_kprobe_test"));



	/* Disable the event or you can't remove it */

	WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,

					  "kprobes",

					  "gen_kretprobe_test", false));



	/* Now give the file and instance back */

	trace_put_event_file(gen_kretprobe_test);



	/* Now unregister and free the event */

	WARN_ON(kprobe_event_delete("gen_kretprobe_test"));

}



module_init(kprobe_event_gen_test_init)

module_exit(kprobe_event_gen_test_exit)



MODULE_AUTHOR("Tom Zanussi");

MODULE_DESCRIPTION("kprobe event generation test");

MODULE_LICENSE("GPL v2");

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