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 /* 39 * Test to make sure we can create a kprobe event, then add more 40 * fields. 41 */ 42 static 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($stack)"); 69 if (ret) 70 goto free; 71 72 /* 73 * This actually creates the event. 74 */ 75 ret = kprobe_event_gen_cmd_end(&cmd); 76 if (ret) 77 goto free; 78 79 /* 80 * Now get the gen_kprobe_test event file. We need to prevent 81 * the instance and event from disappearing from underneath 82 * us, which trace_get_event_file() does (though in this case 83 * we're using the top-level instance which never goes away). 84 */ 85 gen_kprobe_test = trace_get_event_file(NULL, "kprobes", 86 "gen_kprobe_test"); 87 if (IS_ERR(gen_kprobe_test)) { 88 ret = PTR_ERR(gen_kprobe_test); 89 goto delete; 90 } 91 92 /* Enable the event or you won't see anything */ 93 ret = trace_array_set_clr_event(gen_kprobe_test->tr, 94 "kprobes", "gen_kprobe_test", true); 95 if (ret) { 96 trace_put_event_file(gen_kprobe_test); 97 goto delete; 98 } 99 out: 100 return ret; 101 delete: 102 /* We got an error after creating the event, delete it */ 103 ret = kprobe_event_delete("gen_kprobe_test"); 104 free: 105 kfree(buf); 106 107 goto out; 108 } 109 110 /* 111 * Test to make sure we can create a kretprobe event. 112 */ 113 static int __init test_gen_kretprobe_cmd(void) 114 { 115 struct dynevent_cmd cmd; 116 char *buf; 117 int ret; 118 119 /* Create a buffer to hold the generated command */ 120 buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL); 121 if (!buf) 122 return -ENOMEM; 123 124 /* Before generating the command, initialize the cmd object */ 125 kprobe_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN); 126 127 /* 128 * Define the kretprobe event. 129 */ 130 ret = kretprobe_event_gen_cmd_start(&cmd, "gen_kretprobe_test", 131 "do_sys_open", 132 "$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 } 174 175 static 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 } 194 195 static 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 } 219 220 module_init(kprobe_event_gen_test_init) 221 module_exit(kprobe_event_gen_test_exit) 222 223 MODULE_AUTHOR("Tom Zanussi"); 224 MODULE_DESCRIPTION("kprobe event generation test"); 225 MODULE_LICENSE("GPL v2"); 226