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/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#define KPROBE_GEN_TEST_FUNC	"do_sys_open"
39
40/* X86 */
41#if defined(CONFIG_X86_64) || defined(CONFIG_X86_32)
42#define KPROBE_GEN_TEST_ARG0	"dfd=%ax"
43#define KPROBE_GEN_TEST_ARG1	"filename=%dx"
44#define KPROBE_GEN_TEST_ARG2	"flags=%cx"
45#define KPROBE_GEN_TEST_ARG3	"mode=+4($stack)"
46
47/* ARM64 */
48#elif defined(CONFIG_ARM64)
49#define KPROBE_GEN_TEST_ARG0	"dfd=%x0"
50#define KPROBE_GEN_TEST_ARG1	"filename=%x1"
51#define KPROBE_GEN_TEST_ARG2	"flags=%x2"
52#define KPROBE_GEN_TEST_ARG3	"mode=%x3"
53
54/* ARM */
55#elif defined(CONFIG_ARM)
56#define KPROBE_GEN_TEST_ARG0	"dfd=%r0"
57#define KPROBE_GEN_TEST_ARG1	"filename=%r1"
58#define KPROBE_GEN_TEST_ARG2	"flags=%r2"
59#define KPROBE_GEN_TEST_ARG3	"mode=%r3"
60
61/* RISCV */
62#elif defined(CONFIG_RISCV)
63#define KPROBE_GEN_TEST_ARG0	"dfd=%a0"
64#define KPROBE_GEN_TEST_ARG1	"filename=%a1"
65#define KPROBE_GEN_TEST_ARG2	"flags=%a2"
66#define KPROBE_GEN_TEST_ARG3	"mode=%a3"
67
68/* others */
69#else
70#define KPROBE_GEN_TEST_ARG0	NULL
71#define KPROBE_GEN_TEST_ARG1	NULL
72#define KPROBE_GEN_TEST_ARG2	NULL
73#define KPROBE_GEN_TEST_ARG3	NULL
74#endif
75
76static bool trace_event_file_is_valid(struct trace_event_file *input)
77{
78	return input && !IS_ERR(input);
79}
80
81/*
82 * Test to make sure we can create a kprobe event, then add more
83 * fields.
84 */
85static int __init test_gen_kprobe_cmd(void)
86{
87	struct dynevent_cmd cmd;
88	char *buf;
89	int ret;
90
91	/* Create a buffer to hold the generated command */
92	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
93	if (!buf)
94		return -ENOMEM;
95
96	/* Before generating the command, initialize the cmd object */
97	kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
98
99	/*
100	 * Define the gen_kprobe_test event with the first 2 kprobe
101	 * fields.
102	 */
103	ret = kprobe_event_gen_cmd_start(&cmd, "gen_kprobe_test",
104					 KPROBE_GEN_TEST_FUNC,
105					 KPROBE_GEN_TEST_ARG0, KPROBE_GEN_TEST_ARG1);
106	if (ret)
107		goto out;
108
109	/* Use kprobe_event_add_fields to add the rest of the fields */
110
111	ret = kprobe_event_add_fields(&cmd, KPROBE_GEN_TEST_ARG2, KPROBE_GEN_TEST_ARG3);
112	if (ret)
113		goto out;
114
115	/*
116	 * This actually creates the event.
117	 */
118	ret = kprobe_event_gen_cmd_end(&cmd);
119	if (ret)
120		goto out;
121
122	/*
123	 * Now get the gen_kprobe_test event file.  We need to prevent
124	 * the instance and event from disappearing from underneath
125	 * us, which trace_get_event_file() does (though in this case
126	 * we're using the top-level instance which never goes away).
127	 */
128	gen_kprobe_test = trace_get_event_file(NULL, "kprobes",
129					       "gen_kprobe_test");
130	if (IS_ERR(gen_kprobe_test)) {
131		ret = PTR_ERR(gen_kprobe_test);
132		goto delete;
133	}
134
135	/* Enable the event or you won't see anything */
136	ret = trace_array_set_clr_event(gen_kprobe_test->tr,
137					"kprobes", "gen_kprobe_test", true);
138	if (ret) {
139		trace_put_event_file(gen_kprobe_test);
140		goto delete;
141	}
142 out:
143	kfree(buf);
144	return ret;
145 delete:
146	if (trace_event_file_is_valid(gen_kprobe_test))
147		gen_kprobe_test = NULL;
148	/* We got an error after creating the event, delete it */
149	kprobe_event_delete("gen_kprobe_test");
150	goto out;
151}
152
153/*
154 * Test to make sure we can create a kretprobe event.
155 */
156static int __init test_gen_kretprobe_cmd(void)
157{
158	struct dynevent_cmd cmd;
159	char *buf;
160	int ret;
161
162	/* Create a buffer to hold the generated command */
163	buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
164	if (!buf)
165		return -ENOMEM;
166
167	/* Before generating the command, initialize the cmd object */
168	kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);
169
170	/*
171	 * Define the kretprobe event.
172	 */
173	ret = kretprobe_event_gen_cmd_start(&cmd, "gen_kretprobe_test",
174					    KPROBE_GEN_TEST_FUNC,
175					    "$retval");
176	if (ret)
177		goto out;
178
179	/*
180	 * This actually creates the event.
181	 */
182	ret = kretprobe_event_gen_cmd_end(&cmd);
183	if (ret)
184		goto out;
185
186	/*
187	 * Now get the gen_kretprobe_test event file.  We need to
188	 * prevent the instance and event from disappearing from
189	 * underneath us, which trace_get_event_file() does (though in
190	 * this case we're using the top-level instance which never
191	 * goes away).
192	 */
193	gen_kretprobe_test = trace_get_event_file(NULL, "kprobes",
194						  "gen_kretprobe_test");
195	if (IS_ERR(gen_kretprobe_test)) {
196		ret = PTR_ERR(gen_kretprobe_test);
197		goto delete;
198	}
199
200	/* Enable the event or you won't see anything */
201	ret = trace_array_set_clr_event(gen_kretprobe_test->tr,
202					"kprobes", "gen_kretprobe_test", true);
203	if (ret) {
204		trace_put_event_file(gen_kretprobe_test);
205		goto delete;
206	}
207 out:
208	kfree(buf);
209	return ret;
210 delete:
211	if (trace_event_file_is_valid(gen_kretprobe_test))
212		gen_kretprobe_test = NULL;
213	/* We got an error after creating the event, delete it */
214	kprobe_event_delete("gen_kretprobe_test");
215	goto out;
216}
217
218static int __init kprobe_event_gen_test_init(void)
219{
220	int ret;
221
222	ret = test_gen_kprobe_cmd();
223	if (ret)
224		return ret;
225
226	ret = test_gen_kretprobe_cmd();
227	if (ret) {
228		if (trace_event_file_is_valid(gen_kretprobe_test)) {
229			WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
230							  "kprobes",
231							  "gen_kretprobe_test", false));
232			trace_put_event_file(gen_kretprobe_test);
233		}
234		WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
235	}
236
237	return ret;
238}
239
240static void __exit kprobe_event_gen_test_exit(void)
241{
242	if (trace_event_file_is_valid(gen_kprobe_test)) {
243		/* Disable the event or you can't remove it */
244		WARN_ON(trace_array_set_clr_event(gen_kprobe_test->tr,
245						  "kprobes",
246						  "gen_kprobe_test", false));
247
248		/* Now give the file and instance back */
249		trace_put_event_file(gen_kprobe_test);
250	}
251
252
253	/* Now unregister and free the event */
254	WARN_ON(kprobe_event_delete("gen_kprobe_test"));
255
256	if (trace_event_file_is_valid(gen_kretprobe_test)) {
257		/* Disable the event or you can't remove it */
258		WARN_ON(trace_array_set_clr_event(gen_kretprobe_test->tr,
259						  "kprobes",
260						  "gen_kretprobe_test", false));
261
262		/* Now give the file and instance back */
263		trace_put_event_file(gen_kretprobe_test);
264	}
265
266
267	/* Now unregister and free the event */
268	WARN_ON(kprobe_event_delete("gen_kretprobe_test"));
269}
270
271module_init(kprobe_event_gen_test_init)
272module_exit(kprobe_event_gen_test_exit)
273
274MODULE_AUTHOR("Tom Zanussi");
275MODULE_DESCRIPTION("kprobe event generation test");
276MODULE_LICENSE("GPL v2");
277