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 ret = perf_trace_event_init(tp_event, p_event); 276 if (ret) 277 destroy_local_trace_kprobe(tp_event); 278 out: 279 kfree(func); 280 return ret; 281 } 282 283 void perf_kprobe_destroy(struct perf_event *p_event) 284 { 285 perf_trace_event_close(p_event); 286 perf_trace_event_unreg(p_event); 287 288 destroy_local_trace_kprobe(p_event->tp_event); 289 } 290 #endif /* CONFIG_KPROBE_EVENTS */ 291 292 #ifdef CONFIG_UPROBE_EVENTS 293 int perf_uprobe_init(struct perf_event *p_event, 294 unsigned long ref_ctr_offset, bool is_retprobe) 295 { 296 int ret; 297 char *path = NULL; 298 struct trace_event_call *tp_event; 299 300 if (!p_event->attr.uprobe_path) 301 return -EINVAL; 302 303 path = strndup_user(u64_to_user_ptr(p_event->attr.uprobe_path), 304 PATH_MAX); 305 if (IS_ERR(path)) { 306 ret = PTR_ERR(path); 307 return (ret == -EINVAL) ? -E2BIG : ret; 308 } 309 if (path[0] == '\0') { 310 ret = -EINVAL; 311 goto out; 312 } 313 314 tp_event = create_local_trace_uprobe(path, p_event->attr.probe_offset, 315 ref_ctr_offset, is_retprobe); 316 if (IS_ERR(tp_event)) { 317 ret = PTR_ERR(tp_event); 318 goto out; 319 } 320 321 /* 322 * local trace_uprobe need to hold event_mutex to call 323 * uprobe_buffer_enable() and uprobe_buffer_disable(). 324 * event_mutex is not required for local trace_kprobes. 325 */ 326 mutex_lock(&event_mutex); 327 ret = perf_trace_event_init(tp_event, p_event); 328 if (ret) 329 destroy_local_trace_uprobe(tp_event); 330 mutex_unlock(&event_mutex); 331 out: 332 kfree(path); 333 return ret; 334 } 335 336 void perf_uprobe_destroy(struct perf_event *p_event) 337 { 338 mutex_lock(&event_mutex); 339 perf_trace_event_close(p_event); 340 perf_trace_event_unreg(p_event); 341 mutex_unlock(&event_mutex); 342 destroy_local_trace_uprobe(p_event->tp_event); 343 } 344 #endif /* CONFIG_UPROBE_EVENTS */ 345 346 int perf_trace_add(struct perf_event *p_event, int flags) 347 { 348 struct trace_event_call *tp_event = p_event->tp_event; 349 350 if (!(flags & PERF_EF_START)) 351 p_event->hw.state = PERF_HES_STOPPED; 352 353 /* 354 * If TRACE_REG_PERF_ADD returns false; no custom action was performed 355 * and we need to take the default action of enqueueing our event on 356 * the right per-cpu hlist. 357 */ 358 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) { 359 struct hlist_head __percpu *pcpu_list; 360 struct hlist_head *list; 361 362 pcpu_list = tp_event->perf_events; 363 if (WARN_ON_ONCE(!pcpu_list)) 364 return -EINVAL; 365 366 list = this_cpu_ptr(pcpu_list); 367 hlist_add_head_rcu(&p_event->hlist_entry, list); 368 } 369 370 return 0; 371 } 372 373 void perf_trace_del(struct perf_event *p_event, int flags) 374 { 375 struct trace_event_call *tp_event = p_event->tp_event; 376 377 /* 378 * If TRACE_REG_PERF_DEL returns false; no custom action was performed 379 * and we need to take the default action of dequeueing our event from 380 * the right per-cpu hlist. 381 */ 382 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event)) 383 hlist_del_rcu(&p_event->hlist_entry); 384 } 385 386 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp) 387 { 388 char *raw_data; 389 int rctx; 390 391 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 392 393 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, 394 "perf buffer not large enough")) 395 return NULL; 396 397 *rctxp = rctx = perf_swevent_get_recursion_context(); 398 if (rctx < 0) 399 return NULL; 400 401 if (regs) 402 *regs = this_cpu_ptr(&__perf_regs[rctx]); 403 raw_data = this_cpu_ptr(perf_trace_buf[rctx]); 404 405 /* zero the dead bytes from align to not leak stack to user */ 406 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 407 return raw_data; 408 } 409 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc); 410 NOKPROBE_SYMBOL(perf_trace_buf_alloc); 411 412 void perf_trace_buf_update(void *record, u16 type) 413 { 414 struct trace_entry *entry = record; 415 int pc = preempt_count(); 416 unsigned long flags; 417 418 local_save_flags(flags); 419 tracing_generic_entry_update(entry, type, flags, pc); 420 } 421 NOKPROBE_SYMBOL(perf_trace_buf_update); 422 423 #ifdef CONFIG_FUNCTION_TRACER 424 static void 425 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 426 struct ftrace_ops *ops, struct pt_regs *pt_regs) 427 { 428 struct ftrace_entry *entry; 429 struct perf_event *event; 430 struct hlist_head head; 431 struct pt_regs regs; 432 int rctx; 433 434 if ((unsigned long)ops->private != smp_processor_id()) 435 return; 436 437 event = container_of(ops, struct perf_event, ftrace_ops); 438 439 /* 440 * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all 441 * the perf code does is hlist_for_each_entry_rcu(), so we can 442 * get away with simply setting the @head.first pointer in order 443 * to create a singular list. 444 */ 445 head.first = &event->hlist_entry; 446 447 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ 448 sizeof(u64)) - sizeof(u32)) 449 450 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); 451 452 memset(®s, 0, sizeof(regs)); 453 perf_fetch_caller_regs(®s); 454 455 entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx); 456 if (!entry) 457 return; 458 459 entry->ip = ip; 460 entry->parent_ip = parent_ip; 461 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN, 462 1, ®s, &head, NULL); 463 464 #undef ENTRY_SIZE 465 } 466 467 static int perf_ftrace_function_register(struct perf_event *event) 468 { 469 struct ftrace_ops *ops = &event->ftrace_ops; 470 471 ops->flags = FTRACE_OPS_FL_RCU; 472 ops->func = perf_ftrace_function_call; 473 ops->private = (void *)(unsigned long)nr_cpu_ids; 474 475 return register_ftrace_function(ops); 476 } 477 478 static int perf_ftrace_function_unregister(struct perf_event *event) 479 { 480 struct ftrace_ops *ops = &event->ftrace_ops; 481 int ret = unregister_ftrace_function(ops); 482 ftrace_free_filter(ops); 483 return ret; 484 } 485 486 int perf_ftrace_event_register(struct trace_event_call *call, 487 enum trace_reg type, void *data) 488 { 489 struct perf_event *event = data; 490 491 switch (type) { 492 case TRACE_REG_REGISTER: 493 case TRACE_REG_UNREGISTER: 494 break; 495 case TRACE_REG_PERF_REGISTER: 496 case TRACE_REG_PERF_UNREGISTER: 497 return 0; 498 case TRACE_REG_PERF_OPEN: 499 return perf_ftrace_function_register(data); 500 case TRACE_REG_PERF_CLOSE: 501 return perf_ftrace_function_unregister(data); 502 case TRACE_REG_PERF_ADD: 503 event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id(); 504 return 1; 505 case TRACE_REG_PERF_DEL: 506 event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids; 507 return 1; 508 } 509 510 return -EINVAL; 511 } 512 #endif /* CONFIG_FUNCTION_TRACER */ 513