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