kernel/trace/trace_event_perf.c

   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
 356         if (!(flags & PERF_EF_START))
 357                 p_event->hw.state = PERF_HES_STOPPED;
 358
 359         /*
 360          * If TRACE_REG_PERF_ADD returns false; no custom action was performed
 361          * and we need to take the default action of enqueueing our event on
 362          * the right per-cpu hlist.
 363          */
 364         if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) {
 365                 struct hlist_head __percpu *pcpu_list;
 366                 struct hlist_head *list;
 367
 368                 pcpu_list = tp_event->perf_events;
 369                 if (WARN_ON_ONCE(!pcpu_list))
 370                         return -EINVAL;
 371
 372                 list = this_cpu_ptr(pcpu_list);
 373                 hlist_add_head_rcu(&p_event->hlist_entry, list);
 374         }
 375
 376         return 0;
 377 }
 378
 379 void perf_trace_del(struct perf_event *p_event, int flags)
 380 {
 381         struct trace_event_call *tp_event = p_event->tp_event;
 382
 383         /*
 384          * If TRACE_REG_PERF_DEL returns false; no custom action was performed
 385          * and we need to take the default action of dequeueing our event from
 386          * the right per-cpu hlist.
 387          */
 388         if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event))
 389                 hlist_del_rcu(&p_event->hlist_entry);
 390 }
 391
 392 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)
 393 {
 394         char *raw_data;
 395         int rctx;
 396
 397         BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
 398
 399         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
 400                       "perf buffer not large enough, wanted %d, have %d",
 401                       size, PERF_MAX_TRACE_SIZE))
 402                 return NULL;
 403
 404         *rctxp = rctx = perf_swevent_get_recursion_context();
 405         if (rctx < 0)
 406                 return NULL;
 407
 408         if (regs)
 409                 *regs = this_cpu_ptr(&__perf_regs[rctx]);
 410         raw_data = this_cpu_ptr(perf_trace_buf[rctx]);
 411
 412         /* zero the dead bytes from align to not leak stack to user */
 413         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
 414         return raw_data;
 415 }
 416 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc);
 417 NOKPROBE_SYMBOL(perf_trace_buf_alloc);
 418
 419 void perf_trace_buf_update(void *record, u16 type)
 420 {
 421         struct trace_entry *entry = record;
 422
 423         tracing_generic_entry_update(entry, type, tracing_gen_ctx());
 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 ftrace_regs *fregs)
 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         int bit;
 438
 439         if (!rcu_is_watching())
 440                 return;
 441
 442         bit = ftrace_test_recursion_trylock(ip, parent_ip);
 443         if (bit < 0)
 444                 return;
 445
 446         if ((unsigned long)ops->private != smp_processor_id())
 447                 goto out;
 448
 449         event = container_of(ops, struct perf_event, ftrace_ops);
 450
 451         /*
 452          * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all
 453          * the perf code does is hlist_for_each_entry_rcu(), so we can
 454          * get away with simply setting the @head.first pointer in order
 455          * to create a singular list.
 456          */
 457         head.first = &event->hlist_entry;
 458
 459 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
 460                     sizeof(u64)) - sizeof(u32))
 461
 462         BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
 463
 464         memset(&regs, 0, sizeof(regs));
 465         perf_fetch_caller_regs(&regs);
 466
 467         entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);
 468         if (!entry)
 469                 goto out;
 470
 471         entry->ip = ip;
 472         entry->parent_ip = parent_ip;
 473         perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,
 474                               1, &regs, &head, NULL);
 475
 476 out:
 477         ftrace_test_recursion_unlock(bit);
 478 #undef ENTRY_SIZE
 479 }
 480
 481 static int perf_ftrace_function_register(struct perf_event *event)
 482 {
 483         struct ftrace_ops *ops = &event->ftrace_ops;
 484
 485         ops->func    = perf_ftrace_function_call;
 486         ops->private = (void *)(unsigned long)nr_cpu_ids;
 487
 488         return register_ftrace_function(ops);
 489 }
 490
 491 static int perf_ftrace_function_unregister(struct perf_event *event)
 492 {
 493         struct ftrace_ops *ops = &event->ftrace_ops;
 494         int ret = unregister_ftrace_function(ops);
 495         ftrace_free_filter(ops);
 496         return ret;
 497 }
 498
 499 int perf_ftrace_event_register(struct trace_event_call *call,
 500                                enum trace_reg type, void *data)
 501 {
 502         struct perf_event *event = data;
 503
 504         switch (type) {
 505         case TRACE_REG_REGISTER:
 506         case TRACE_REG_UNREGISTER:
 507                 break;
 508         case TRACE_REG_PERF_REGISTER:
 509         case TRACE_REG_PERF_UNREGISTER:
 510                 return 0;
 511         case TRACE_REG_PERF_OPEN:
 512                 return perf_ftrace_function_register(data);
 513         case TRACE_REG_PERF_CLOSE:
 514                 return perf_ftrace_function_unregister(data);
 515         case TRACE_REG_PERF_ADD:
 516                 event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id();
 517                 return 1;
 518         case TRACE_REG_PERF_DEL:
 519                 event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids;
 520                 return 1;
 521         }
 522
 523         return -EINVAL;
 524 }
 525 #endif /* CONFIG_FUNCTION_TRACER */