1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * trace event based perf event profiling/tracing 4 * 5 * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra 6 * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com> 7 */ 8 9 #include <linux/module.h> 10 #include <linux/kprobes.h> 11 #include <linux/security.h> 12 #include "trace.h" 13 #include "trace_probe.h" 14 15 static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS]; 16 17 /* 18 * Force it to be aligned to unsigned long to avoid misaligned accesses 19 * surprises 20 */ 21 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)]) 22 perf_trace_t; 23 24 /* Count the events in use (per event id, not per instance) */ 25 static int total_ref_count; 26 27 static int perf_trace_event_perm(struct trace_event_call *tp_event, 28 struct perf_event *p_event) 29 { 30 int ret; 31 32 if (tp_event->perf_perm) { 33 ret = tp_event->perf_perm(tp_event, p_event); 34 if (ret) 35 return ret; 36 } 37 38 /* 39 * We checked and allowed to create parent, 40 * allow children without checking. 41 */ 42 if (p_event->parent) 43 return 0; 44 45 /* 46 * It's ok to check current process (owner) permissions in here, 47 * because code below is called only via perf_event_open syscall. 48 */ 49 50 /* The ftrace function trace is allowed only for root. */ 51 if (ftrace_event_is_function(tp_event)) { 52 ret = perf_allow_tracepoint(&p_event->attr); 53 if (ret) 54 return ret; 55 56 if (!is_sampling_event(p_event)) 57 return 0; 58 59 /* 60 * We don't allow user space callchains for function trace 61 * event, due to issues with page faults while tracing page 62 * fault handler and its overall trickiness nature. 63 */ 64 if (!p_event->attr.exclude_callchain_user) 65 return -EINVAL; 66 67 /* 68 * Same reason to disable user stack dump as for user space 69 * callchains above. 70 */ 71 if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER) 72 return -EINVAL; 73 } 74 75 /* No tracing, just counting, so no obvious leak */ 76 if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW)) 77 return 0; 78 79 /* Some events are ok to be traced by non-root users... */ 80 if (p_event->attach_state == PERF_ATTACH_TASK) { 81 if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY) 82 return 0; 83 } 84 85 /* 86 * ...otherwise raw tracepoint data can be a severe data leak, 87 * only allow root to have these. 88 */ 89 ret = perf_allow_tracepoint(&p_event->attr); 90 if (ret) 91 return ret; 92 93 return 0; 94 } 95 96 static int perf_trace_event_reg(struct trace_event_call *tp_event, 97 struct perf_event *p_event) 98 { 99 struct hlist_head __percpu *list; 100 int ret = -ENOMEM; 101 int cpu; 102 103 p_event->tp_event = tp_event; 104 if (tp_event->perf_refcount++ > 0) 105 return 0; 106 107 list = alloc_percpu(struct hlist_head); 108 if (!list) 109 goto fail; 110 111 for_each_possible_cpu(cpu) 112 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu)); 113 114 tp_event->perf_events = list; 115 116 if (!total_ref_count) { 117 char __percpu *buf; 118 int i; 119 120 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 121 buf = (char __percpu *)alloc_percpu(perf_trace_t); 122 if (!buf) 123 goto fail; 124 125 perf_trace_buf[i] = buf; 126 } 127 } 128 129 ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL); 130 if (ret) 131 goto fail; 132 133 total_ref_count++; 134 return 0; 135 136 fail: 137 if (!total_ref_count) { 138 int i; 139 140 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 141 free_percpu(perf_trace_buf[i]); 142 perf_trace_buf[i] = NULL; 143 } 144 } 145 146 if (!--tp_event->perf_refcount) { 147 free_percpu(tp_event->perf_events); 148 tp_event->perf_events = NULL; 149 } 150 151 return ret; 152 } 153 154 static void perf_trace_event_unreg(struct perf_event *p_event) 155 { 156 struct trace_event_call *tp_event = p_event->tp_event; 157 int i; 158 159 if (--tp_event->perf_refcount > 0) 160 goto out; 161 162 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL); 163 164 /* 165 * Ensure our callback won't be called anymore. The buffers 166 * will be freed after that. 167 */ 168 tracepoint_synchronize_unregister(); 169 170 free_percpu(tp_event->perf_events); 171 tp_event->perf_events = NULL; 172 173 if (!--total_ref_count) { 174 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 175 free_percpu(perf_trace_buf[i]); 176 perf_trace_buf[i] = NULL; 177 } 178 } 179 out: 180 module_put(tp_event->mod); 181 } 182 183 static int perf_trace_event_open(struct perf_event *p_event) 184 { 185 struct trace_event_call *tp_event = p_event->tp_event; 186 return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event); 187 } 188 189 static void perf_trace_event_close(struct perf_event *p_event) 190 { 191 struct trace_event_call *tp_event = p_event->tp_event; 192 tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event); 193 } 194 195 static int perf_trace_event_init(struct trace_event_call *tp_event, 196 struct perf_event *p_event) 197 { 198 int ret; 199 200 ret = perf_trace_event_perm(tp_event, p_event); 201 if (ret) 202 return ret; 203 204 ret = perf_trace_event_reg(tp_event, p_event); 205 if (ret) 206 return ret; 207 208 ret = perf_trace_event_open(p_event); 209 if (ret) { 210 perf_trace_event_unreg(p_event); 211 return ret; 212 } 213 214 return 0; 215 } 216 217 int perf_trace_init(struct perf_event *p_event) 218 { 219 struct trace_event_call *tp_event; 220 u64 event_id = p_event->attr.config; 221 int ret = -EINVAL; 222 223 mutex_lock(&event_mutex); 224 list_for_each_entry(tp_event, &ftrace_events, list) { 225 if (tp_event->event.type == event_id && 226 tp_event->class && tp_event->class->reg && 227 try_module_get(tp_event->mod)) { 228 ret = perf_trace_event_init(tp_event, p_event); 229 if (ret) 230 module_put(tp_event->mod); 231 break; 232 } 233 } 234 mutex_unlock(&event_mutex); 235 236 return ret; 237 } 238 239 void perf_trace_destroy(struct perf_event *p_event) 240 { 241 mutex_lock(&event_mutex); 242 perf_trace_event_close(p_event); 243 perf_trace_event_unreg(p_event); 244 mutex_unlock(&event_mutex); 245 } 246 247 #ifdef CONFIG_KPROBE_EVENTS 248 int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe) 249 { 250 int ret; 251 char *func = NULL; 252 struct trace_event_call *tp_event; 253 254 if (p_event->attr.kprobe_func) { 255 func = kzalloc(KSYM_NAME_LEN, GFP_KERNEL); 256 if (!func) 257 return -ENOMEM; 258 ret = strncpy_from_user( 259 func, u64_to_user_ptr(p_event->attr.kprobe_func), 260 KSYM_NAME_LEN); 261 if (ret == KSYM_NAME_LEN) 262 ret = -E2BIG; 263 if (ret < 0) 264 goto out; 265 266 if (func[0] == '\0') { 267 kfree(func); 268 func = NULL; 269 } 270 } 271 272 tp_event = create_local_trace_kprobe( 273 func, (void *)(unsigned long)(p_event->attr.kprobe_addr), 274 p_event->attr.probe_offset, is_retprobe); 275 if (IS_ERR(tp_event)) { 276 ret = PTR_ERR(tp_event); 277 goto out; 278 } 279 280 mutex_lock(&event_mutex); 281 ret = perf_trace_event_init(tp_event, p_event); 282 if (ret) 283 destroy_local_trace_kprobe(tp_event); 284 mutex_unlock(&event_mutex); 285 out: 286 kfree(func); 287 return ret; 288 } 289 290 void perf_kprobe_destroy(struct perf_event *p_event) 291 { 292 mutex_lock(&event_mutex); 293 perf_trace_event_close(p_event); 294 perf_trace_event_unreg(p_event); 295 mutex_unlock(&event_mutex); 296 297 destroy_local_trace_kprobe(p_event->tp_event); 298 } 299 #endif /* CONFIG_KPROBE_EVENTS */ 300 301 #ifdef CONFIG_UPROBE_EVENTS 302 int perf_uprobe_init(struct perf_event *p_event, 303 unsigned long ref_ctr_offset, bool is_retprobe) 304 { 305 int ret; 306 char *path = NULL; 307 struct trace_event_call *tp_event; 308 309 if (!p_event->attr.uprobe_path) 310 return -EINVAL; 311 312 path = strndup_user(u64_to_user_ptr(p_event->attr.uprobe_path), 313 PATH_MAX); 314 if (IS_ERR(path)) { 315 ret = PTR_ERR(path); 316 return (ret == -EINVAL) ? -E2BIG : ret; 317 } 318 if (path[0] == '\0') { 319 ret = -EINVAL; 320 goto out; 321 } 322 323 tp_event = create_local_trace_uprobe(path, p_event->attr.probe_offset, 324 ref_ctr_offset, is_retprobe); 325 if (IS_ERR(tp_event)) { 326 ret = PTR_ERR(tp_event); 327 goto out; 328 } 329 330 /* 331 * local trace_uprobe need to hold event_mutex to call 332 * uprobe_buffer_enable() and uprobe_buffer_disable(). 333 * event_mutex is not required for local trace_kprobes. 334 */ 335 mutex_lock(&event_mutex); 336 ret = perf_trace_event_init(tp_event, p_event); 337 if (ret) 338 destroy_local_trace_uprobe(tp_event); 339 mutex_unlock(&event_mutex); 340 out: 341 kfree(path); 342 return ret; 343 } 344 345 void perf_uprobe_destroy(struct perf_event *p_event) 346 { 347 mutex_lock(&event_mutex); 348 perf_trace_event_close(p_event); 349 perf_trace_event_unreg(p_event); 350 mutex_unlock(&event_mutex); 351 destroy_local_trace_uprobe(p_event->tp_event); 352 } 353 #endif /* CONFIG_UPROBE_EVENTS */ 354 355 int perf_trace_add(struct perf_event *p_event, int flags) 356 { 357 struct trace_event_call *tp_event = p_event->tp_event; 358 359 if (!(flags & PERF_EF_START)) 360 p_event->hw.state = PERF_HES_STOPPED; 361 362 /* 363 * If TRACE_REG_PERF_ADD returns false; no custom action was performed 364 * and we need to take the default action of enqueueing our event on 365 * the right per-cpu hlist. 366 */ 367 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) { 368 struct hlist_head __percpu *pcpu_list; 369 struct hlist_head *list; 370 371 pcpu_list = tp_event->perf_events; 372 if (WARN_ON_ONCE(!pcpu_list)) 373 return -EINVAL; 374 375 list = this_cpu_ptr(pcpu_list); 376 hlist_add_head_rcu(&p_event->hlist_entry, list); 377 } 378 379 return 0; 380 } 381 382 void perf_trace_del(struct perf_event *p_event, int flags) 383 { 384 struct trace_event_call *tp_event = p_event->tp_event; 385 386 /* 387 * If TRACE_REG_PERF_DEL returns false; no custom action was performed 388 * and we need to take the default action of dequeueing our event from 389 * the right per-cpu hlist. 390 */ 391 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event)) 392 hlist_del_rcu(&p_event->hlist_entry); 393 } 394 395 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp) 396 { 397 char *raw_data; 398 int rctx; 399 400 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 401 402 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, 403 "perf buffer not large enough")) 404 return NULL; 405 406 *rctxp = rctx = perf_swevent_get_recursion_context(); 407 if (rctx < 0) 408 return NULL; 409 410 if (regs) 411 *regs = this_cpu_ptr(&__perf_regs[rctx]); 412 raw_data = this_cpu_ptr(perf_trace_buf[rctx]); 413 414 /* zero the dead bytes from align to not leak stack to user */ 415 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 416 return raw_data; 417 } 418 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc); 419 NOKPROBE_SYMBOL(perf_trace_buf_alloc); 420 421 void perf_trace_buf_update(void *record, u16 type) 422 { 423 struct trace_entry *entry = record; 424 425 tracing_generic_entry_update(entry, type, tracing_gen_ctx()); 426 } 427 NOKPROBE_SYMBOL(perf_trace_buf_update); 428 429 #ifdef CONFIG_FUNCTION_TRACER 430 static void 431 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 432 struct ftrace_ops *ops, struct ftrace_regs *fregs) 433 { 434 struct ftrace_entry *entry; 435 struct perf_event *event; 436 struct hlist_head head; 437 struct pt_regs regs; 438 int rctx; 439 int bit; 440 441 if (!rcu_is_watching()) 442 return; 443 444 if ((unsigned long)ops->private != smp_processor_id()) 445 return; 446 447 bit = ftrace_test_recursion_trylock(ip, parent_ip); 448 if (bit < 0) 449 return; 450 451 event = container_of(ops, struct perf_event, ftrace_ops); 452 453 /* 454 * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all 455 * the perf code does is hlist_for_each_entry_rcu(), so we can 456 * get away with simply setting the @head.first pointer in order 457 * to create a singular list. 458 */ 459 head.first = &event->hlist_entry; 460 461 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ 462 sizeof(u64)) - sizeof(u32)) 463 464 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); 465 466 memset(®s, 0, sizeof(regs)); 467 perf_fetch_caller_regs(®s); 468 469 entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx); 470 if (!entry) 471 goto out; 472 473 entry->ip = ip; 474 entry->parent_ip = parent_ip; 475 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN, 476 1, ®s, &head, NULL); 477 478 out: 479 ftrace_test_recursion_unlock(bit); 480 #undef ENTRY_SIZE 481 } 482 483 static int perf_ftrace_function_register(struct perf_event *event) 484 { 485 struct ftrace_ops *ops = &event->ftrace_ops; 486 487 ops->func = perf_ftrace_function_call; 488 ops->private = (void *)(unsigned long)nr_cpu_ids; 489 490 return register_ftrace_function(ops); 491 } 492 493 static int perf_ftrace_function_unregister(struct perf_event *event) 494 { 495 struct ftrace_ops *ops = &event->ftrace_ops; 496 int ret = unregister_ftrace_function(ops); 497 ftrace_free_filter(ops); 498 return ret; 499 } 500 501 int perf_ftrace_event_register(struct trace_event_call *call, 502 enum trace_reg type, void *data) 503 { 504 struct perf_event *event = data; 505 506 switch (type) { 507 case TRACE_REG_REGISTER: 508 case TRACE_REG_UNREGISTER: 509 break; 510 case TRACE_REG_PERF_REGISTER: 511 case TRACE_REG_PERF_UNREGISTER: 512 return 0; 513 case TRACE_REG_PERF_OPEN: 514 return perf_ftrace_function_register(data); 515 case TRACE_REG_PERF_CLOSE: 516 return perf_ftrace_function_unregister(data); 517 case TRACE_REG_PERF_ADD: 518 event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id(); 519 return 1; 520 case TRACE_REG_PERF_DEL: 521 event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids; 522 return 1; 523 } 524 525 return -EINVAL; 526 } 527 #endif /* CONFIG_FUNCTION_TRACER */ 528