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 
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 
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  */
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 	ret = kprobe_event_delete("gen_kprobe_test");
150 	goto out;
151 }
152 
153 /*
154  * Test to make sure we can create a kretprobe event.
155  */
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 	ret = kprobe_event_delete("gen_kretprobe_test");
215 	goto out;
216 }
217 
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 
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