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 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 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 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