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 return; 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 } 180 181 static int perf_trace_event_open(struct perf_event *p_event) 182 { 183 struct trace_event_call *tp_event = p_event->tp_event; 184 return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event); 185 } 186 187 static void perf_trace_event_close(struct perf_event *p_event) 188 { 189 struct trace_event_call *tp_event = p_event->tp_event; 190 tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event); 191 } 192 193 static int perf_trace_event_init(struct trace_event_call *tp_event, 194 struct perf_event *p_event) 195 { 196 int ret; 197 198 ret = perf_trace_event_perm(tp_event, p_event); 199 if (ret) 200 return ret; 201 202 ret = perf_trace_event_reg(tp_event, p_event); 203 if (ret) 204 return ret; 205 206 ret = perf_trace_event_open(p_event); 207 if (ret) { 208 perf_trace_event_unreg(p_event); 209 return ret; 210 } 211 212 return 0; 213 } 214 215 int perf_trace_init(struct perf_event *p_event) 216 { 217 struct trace_event_call *tp_event; 218 u64 event_id = p_event->attr.config; 219 int ret = -EINVAL; 220 221 mutex_lock(&event_mutex); 222 list_for_each_entry(tp_event, &ftrace_events, list) { 223 if (tp_event->event.type == event_id && 224 tp_event->class && tp_event->class->reg && 225 trace_event_try_get_ref(tp_event)) { 226 ret = perf_trace_event_init(tp_event, p_event); 227 if (ret) 228 trace_event_put_ref(tp_event); 229 break; 230 } 231 } 232 mutex_unlock(&event_mutex); 233 234 return ret; 235 } 236 237 void perf_trace_destroy(struct perf_event *p_event) 238 { 239 mutex_lock(&event_mutex); 240 perf_trace_event_close(p_event); 241 perf_trace_event_unreg(p_event); 242 trace_event_put_ref(p_event->tp_event); 243 mutex_unlock(&event_mutex); 244 } 245 246 #ifdef CONFIG_KPROBE_EVENTS 247 int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe) 248 { 249 int ret; 250 char *func = NULL; 251 struct trace_event_call *tp_event; 252 253 if (p_event->attr.kprobe_func) { 254 func = strndup_user(u64_to_user_ptr(p_event->attr.kprobe_func), 255 KSYM_NAME_LEN); 256 if (IS_ERR(func)) { 257 ret = PTR_ERR(func); 258 return (ret == -EINVAL) ? -E2BIG : ret; 259 } 260 261 if (func[0] == '\0') { 262 kfree(func); 263 func = NULL; 264 } 265 } 266 267 tp_event = create_local_trace_kprobe( 268 func, (void *)(unsigned long)(p_event->attr.kprobe_addr), 269 p_event->attr.probe_offset, is_retprobe); 270 if (IS_ERR(tp_event)) { 271 ret = PTR_ERR(tp_event); 272 goto out; 273 } 274 275 mutex_lock(&event_mutex); 276 ret = perf_trace_event_init(tp_event, p_event); 277 if (ret) 278 destroy_local_trace_kprobe(tp_event); 279 mutex_unlock(&event_mutex); 280 out: 281 kfree(func); 282 return ret; 283 } 284 285 void perf_kprobe_destroy(struct perf_event *p_event) 286 { 287 mutex_lock(&event_mutex); 288 perf_trace_event_close(p_event); 289 perf_trace_event_unreg(p_event); 290 trace_event_put_ref(p_event->tp_event); 291 mutex_unlock(&event_mutex); 292 293 destroy_local_trace_kprobe(p_event->tp_event); 294 } 295 #endif /* CONFIG_KPROBE_EVENTS */ 296 297 #ifdef CONFIG_UPROBE_EVENTS 298 int perf_uprobe_init(struct perf_event *p_event, 299 unsigned long ref_ctr_offset, bool is_retprobe) 300 { 301 int ret; 302 char *path = NULL; 303 struct trace_event_call *tp_event; 304 305 if (!p_event->attr.uprobe_path) 306 return -EINVAL; 307 308 path = strndup_user(u64_to_user_ptr(p_event->attr.uprobe_path), 309 PATH_MAX); 310 if (IS_ERR(path)) { 311 ret = PTR_ERR(path); 312 return (ret == -EINVAL) ? -E2BIG : ret; 313 } 314 if (path[0] == '\0') { 315 ret = -EINVAL; 316 goto out; 317 } 318 319 tp_event = create_local_trace_uprobe(path, p_event->attr.probe_offset, 320 ref_ctr_offset, is_retprobe); 321 if (IS_ERR(tp_event)) { 322 ret = PTR_ERR(tp_event); 323 goto out; 324 } 325 326 /* 327 * local trace_uprobe need to hold event_mutex to call 328 * uprobe_buffer_enable() and uprobe_buffer_disable(). 329 * event_mutex is not required for local trace_kprobes. 330 */ 331 mutex_lock(&event_mutex); 332 ret = perf_trace_event_init(tp_event, p_event); 333 if (ret) 334 destroy_local_trace_uprobe(tp_event); 335 mutex_unlock(&event_mutex); 336 out: 337 kfree(path); 338 return ret; 339 } 340 341 void perf_uprobe_destroy(struct perf_event *p_event) 342 { 343 mutex_lock(&event_mutex); 344 perf_trace_event_close(p_event); 345 perf_trace_event_unreg(p_event); 346 trace_event_put_ref(p_event->tp_event); 347 mutex_unlock(&event_mutex); 348 destroy_local_trace_uprobe(p_event->tp_event); 349 } 350 #endif /* CONFIG_UPROBE_EVENTS */ 351 352 int perf_trace_add(struct perf_event *p_event, int flags) 353 { 354 struct trace_event_call *tp_event = p_event->tp_event; 355 struct hw_perf_event *hwc = &p_event->hw; 356 357 if (!(flags & PERF_EF_START)) 358 p_event->hw.state = PERF_HES_STOPPED; 359 360 if (is_sampling_event(p_event)) { 361 hwc->last_period = hwc->sample_period; 362 perf_swevent_set_period(p_event); 363 } 364 365 /* 366 * If TRACE_REG_PERF_ADD returns false; no custom action was performed 367 * and we need to take the default action of enqueueing our event on 368 * the right per-cpu hlist. 369 */ 370 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) { 371 struct hlist_head __percpu *pcpu_list; 372 struct hlist_head *list; 373 374 pcpu_list = tp_event->perf_events; 375 if (WARN_ON_ONCE(!pcpu_list)) 376 return -EINVAL; 377 378 list = this_cpu_ptr(pcpu_list); 379 hlist_add_head_rcu(&p_event->hlist_entry, list); 380 } 381 382 return 0; 383 } 384 385 void perf_trace_del(struct perf_event *p_event, int flags) 386 { 387 struct trace_event_call *tp_event = p_event->tp_event; 388 389 /* 390 * If TRACE_REG_PERF_DEL returns false; no custom action was performed 391 * and we need to take the default action of dequeueing our event from 392 * the right per-cpu hlist. 393 */ 394 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event)) 395 hlist_del_rcu(&p_event->hlist_entry); 396 } 397 398 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp) 399 { 400 char *raw_data; 401 int rctx; 402 403 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 404 405 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, 406 "perf buffer not large enough, wanted %d, have %d", 407 size, PERF_MAX_TRACE_SIZE)) 408 return NULL; 409 410 *rctxp = rctx = perf_swevent_get_recursion_context(); 411 if (rctx < 0) 412 return NULL; 413 414 if (regs) 415 *regs = this_cpu_ptr(&__perf_regs[rctx]); 416 raw_data = this_cpu_ptr(perf_trace_buf[rctx]); 417 418 /* zero the dead bytes from align to not leak stack to user */ 419 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 420 return raw_data; 421 } 422 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc); 423 NOKPROBE_SYMBOL(perf_trace_buf_alloc); 424 425 void perf_trace_buf_update(void *record, u16 type) 426 { 427 struct trace_entry *entry = record; 428 429 tracing_generic_entry_update(entry, type, tracing_gen_ctx()); 430 } 431 NOKPROBE_SYMBOL(perf_trace_buf_update); 432 433 #ifdef CONFIG_FUNCTION_TRACER 434 static void 435 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 436 struct ftrace_ops *ops, struct ftrace_regs *fregs) 437 { 438 struct ftrace_entry *entry; 439 struct perf_event *event; 440 struct hlist_head head; 441 struct pt_regs regs; 442 int rctx; 443 int bit; 444 445 if (!rcu_is_watching()) 446 return; 447 448 bit = ftrace_test_recursion_trylock(ip, parent_ip); 449 if (bit < 0) 450 return; 451 452 if ((unsigned long)ops->private != smp_processor_id()) 453 goto out; 454 455 event = container_of(ops, struct perf_event, ftrace_ops); 456 457 /* 458 * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all 459 * the perf code does is hlist_for_each_entry_rcu(), so we can 460 * get away with simply setting the @head.first pointer in order 461 * to create a singular list. 462 */ 463 head.first = &event->hlist_entry; 464 465 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ 466 sizeof(u64)) - sizeof(u32)) 467 468 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); 469 470 memset(®s, 0, sizeof(regs)); 471 perf_fetch_caller_regs(®s); 472 473 entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx); 474 if (!entry) 475 goto out; 476 477 entry->ip = ip; 478 entry->parent_ip = parent_ip; 479 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN, 480 1, ®s, &head, NULL); 481 482 out: 483 ftrace_test_recursion_unlock(bit); 484 #undef ENTRY_SIZE 485 } 486 487 static int perf_ftrace_function_register(struct perf_event *event) 488 { 489 struct ftrace_ops *ops = &event->ftrace_ops; 490 491 ops->func = perf_ftrace_function_call; 492 ops->private = (void *)(unsigned long)nr_cpu_ids; 493 494 return register_ftrace_function(ops); 495 } 496 497 static int perf_ftrace_function_unregister(struct perf_event *event) 498 { 499 struct ftrace_ops *ops = &event->ftrace_ops; 500 int ret = unregister_ftrace_function(ops); 501 ftrace_free_filter(ops); 502 return ret; 503 } 504 505 int perf_ftrace_event_register(struct trace_event_call *call, 506 enum trace_reg type, void *data) 507 { 508 struct perf_event *event = data; 509 510 switch (type) { 511 case TRACE_REG_REGISTER: 512 case TRACE_REG_UNREGISTER: 513 break; 514 case TRACE_REG_PERF_REGISTER: 515 case TRACE_REG_PERF_UNREGISTER: 516 return 0; 517 case TRACE_REG_PERF_OPEN: 518 return perf_ftrace_function_register(data); 519 case TRACE_REG_PERF_CLOSE: 520 return perf_ftrace_function_unregister(data); 521 case TRACE_REG_PERF_ADD: 522 event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id(); 523 return 1; 524 case TRACE_REG_PERF_DEL: 525 event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids; 526 return 1; 527 } 528 529 return -EINVAL; 530 } 531 #endif /* CONFIG_FUNCTION_TRACER */ 532