// 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");
