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
35 static struct trace_event_file *gen_kprobe_test;
36 static 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
trace_event_file_is_valid(struct trace_event_file * input)76 static 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 */
test_gen_kprobe_cmd(void)85 static 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 */
test_gen_kretprobe_cmd(void)156 static 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
kprobe_event_gen_test_init(void)218 static 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
kprobe_event_gen_test_exit(void)240 static 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
271 module_init(kprobe_event_gen_test_init)
272 module_exit(kprobe_event_gen_test_exit)
273
274 MODULE_AUTHOR("Tom Zanussi");
275 MODULE_DESCRIPTION("kprobe event generation test");
276 MODULE_LICENSE("GPL v2");
277