1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Test module for in-kernel kprobe event creation and generation.
  4 *
  5 * Copyright (C) 2019 Tom Zanussi <zanussi@kernel.org>
  6 */
  7
  8#include <linux/module.h>
  9#include <linux/trace_events.h>
 10
 11/*
 12 * This module is a simple test of basic functionality for in-kernel
 13 * kprobe/kretprobe event creation.  The first test uses
 14 * kprobe_event_gen_cmd_start(), kprobe_event_add_fields() and
 15 * kprobe_event_gen_cmd_end() to create a kprobe event, which is then
 16 * enabled in order to generate trace output.  The second creates a
 17 * kretprobe event using kretprobe_event_gen_cmd_start() and
 18 * kretprobe_event_gen_cmd_end(), and is also then enabled.
 19 *
 20 * To test, select CONFIG_KPROBE_EVENT_GEN_TEST and build the module.
 21 * Then:
 22 *
 23 * # insmod kernel/trace/kprobe_event_gen_test.ko
 24 * # cat /sys/kernel/debug/tracing/trace
 25 *
 26 * You should see many instances of the "gen_kprobe_test" and
 27 * "gen_kretprobe_test" events in the trace buffer.
 28 *
 29 * To remove the events, remove the module:
 30 *
 31 * # rmmod kprobe_event_gen_test
 32 *
 33 */
 34
 35static struct trace_event_file *gen_kprobe_test;
 36static struct trace_event_file *gen_kretprobe_test;
 37
 38/*
 39 * Test to make sure we can create a kprobe event, then add more
 40 * fields.
 41 */
 42static int __init test_gen_kprobe_cmd(void)
 43{
 44	struct dynevent_cmd cmd;
 45	char *buf;
 46	int ret;
 47
 48	/* Create a buffer to hold the generated command */
 49	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
 50	if (!buf)
 51		return -ENOMEM;
 52
 53	/* Before generating the command, initialize the cmd object */
 54	kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
 55
 56	/*
 57	 * Define the gen_kprobe_test event with the first 2 kprobe
 58	 * fields.
 59	 */
 60	ret = kprobe_event_gen_cmd_start(&cmd, "gen_kprobe_test",
 61					 "do_sys_open",
 62					 "dfd=%ax", "filename=%dx");
 63	if (ret)
 64		goto free;
 65
 66	/* Use kprobe_event_add_fields to add the rest of the fields */
 67
 68	ret = kprobe_event_add_fields(&cmd, "flags=%cx", "mode=+4($stack)");
 69	if (ret)
 70		goto free;
 71
 72	/*
 73	 * This actually creates the event.
 74	 */
 75	ret = kprobe_event_gen_cmd_end(&cmd);
 76	if (ret)
 77		goto free;
 78
 79	/*
 80	 * Now get the gen_kprobe_test event file.  We need to prevent
 81	 * the instance and event from disappearing from underneath
 82	 * us, which trace_get_event_file() does (though in this case
 83	 * we're using the top-level instance which never goes away).
 84	 */
 85	gen_kprobe_test = trace_get_event_file(NULL, "kprobes",
 86					       "gen_kprobe_test");
 87	if (IS_ERR(gen_kprobe_test)) {
 88		ret = PTR_ERR(gen_kprobe_test);
 89		goto delete;
 90	}
 91
 92	/* Enable the event or you won't see anything */
 93	ret = trace_array_set_clr_event(gen_kprobe_test->tr,
 94					"kprobes", "gen_kprobe_test", true);
 95	if (ret) {
 96		trace_put_event_file(gen_kprobe_test);
 97		goto delete;
 98	}
 99 out:
100	return ret;
101 delete:
102	/* We got an error after creating the event, delete it */
103	ret = kprobe_event_delete("gen_kprobe_test");
104 free:
105	kfree(buf);
106
107	goto out;
108}
109
110/*
111 * Test to make sure we can create a kretprobe event.
112 */
113static int __init test_gen_kretprobe_cmd(void)
114{
115	struct dynevent_cmd cmd;
116	char *buf;
117	int ret;
118
119	/* Create a buffer to hold the generated command */
120	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
121	if (!buf)
122		return -ENOMEM;
123
124	/* Before generating the command, initialize the cmd object */
125	kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
126
127	/*
128	 * Define the kretprobe event.
129	 */
130	ret = kretprobe_event_gen_cmd_start(&cmd, "gen_kretprobe_test",
131					    "do_sys_open",
132					    "$retval");
133	if (ret)
134		goto free;
135
136	/*
137	 * This actually creates the event.
138	 */
139	ret = kretprobe_event_gen_cmd_end(&cmd);
140	if (ret)
141		goto free;
142
143	/*
144	 * Now get the gen_kretprobe_test event file.  We need to
145	 * prevent the instance and event from disappearing from
146	 * underneath us, which trace_get_event_file() does (though in
147	 * this case we're using the top-level instance which never
148	 * goes away).
149	 */
150	gen_kretprobe_test = trace_get_event_file(NULL, "kprobes",
151						  "gen_kretprobe_test");
152	if (IS_ERR(gen_kretprobe_test)) {
153		ret = PTR_ERR(gen_kretprobe_test);
154		goto delete;
155	}
156
157	/* Enable the event or you won't see anything */
158	ret = trace_array_set_clr_event(gen_kretprobe_test->tr,
159					"kprobes", "gen_kretprobe_test", true);
160	if (ret) {
161		trace_put_event_file(gen_kretprobe_test);
162		goto delete;
163	}
164 out:
165	return ret;
166 delete:
167	/* We got an error after creating the event, delete it */
168	ret = kprobe_event_delete("gen_kretprobe_test");
169 free:
170	kfree(buf);
171
172	goto out;
173}
174
175static int __init kprobe_event_gen_test_init(void)
176{
177	int ret;
178
179	ret = test_gen_kprobe_cmd();
180	if (ret)
181		return ret;
182
183	ret = test_gen_kretprobe_cmd();
184	if (ret) {
185		WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
186						  "kprobes",
187						  "gen_kretprobe_test", false));
188		trace_put_event_file(gen_kretprobe_test);
189		WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
190	}
191
192	return ret;
193}
194
195static void __exit kprobe_event_gen_test_exit(void)
196{
197	/* Disable the event or you can't remove it */
198	WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
199					  "kprobes",
200					  "gen_kprobe_test", false));
201
202	/* Now give the file and instance back */
203	trace_put_event_file(gen_kprobe_test);
204
205	/* Now unregister and free the event */
206	WARN_ON(kprobe_event_delete("gen_kprobe_test"));
207
208	/* Disable the event or you can't remove it */
209	WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
210					  "kprobes",
211					  "gen_kretprobe_test", false));
212
213	/* Now give the file and instance back */
214	trace_put_event_file(gen_kretprobe_test);
215
216	/* Now unregister and free the event */
217	WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
218}
219
220module_init(kprobe_event_gen_test_init)
221module_exit(kprobe_event_gen_test_exit)
222
223MODULE_AUTHOR("Tom Zanussi");
224MODULE_DESCRIPTION("kprobe event generation test");
225MODULE_LICENSE("GPL v2");