kernel/trace/trace_syscalls.c

   1 #include <trace/syscall.h>
   2 #include <trace/events/syscalls.h>
   3 #include <linux/slab.h>
   4 #include <linux/kernel.h>
   5 #include <linux/ftrace.h>
   6 #include <linux/perf_event.h>
   7 #include <asm/syscall.h>
   8
   9 #include "trace_output.h"
  10 #include "trace.h"
  11
  12 static DEFINE_MUTEX(syscall_trace_lock);
  13 static int sys_refcount_enter;
  14 static int sys_refcount_exit;
  15 static DECLARE_BITMAP(enabled_enter_syscalls, NR_syscalls);
  16 static DECLARE_BITMAP(enabled_exit_syscalls, NR_syscalls);
  17
  18 static int syscall_enter_register(struct ftrace_event_call *event,
  19                                  enum trace_reg type);
  20 static int syscall_exit_register(struct ftrace_event_call *event,
  21                                  enum trace_reg type);
  22
  23 static int syscall_enter_define_fields(struct ftrace_event_call *call);
  24 static int syscall_exit_define_fields(struct ftrace_event_call *call);
  25
  26 static struct list_head *
  27 syscall_get_enter_fields(struct ftrace_event_call *call)
  28 {
  29         struct syscall_metadata *entry = call->data;
  30
  31         return &entry->enter_fields;
  32 }
  33
  34 struct trace_event_functions enter_syscall_print_funcs = {
  35         .trace          = print_syscall_enter,
  36 };
  37
  38 struct trace_event_functions exit_syscall_print_funcs = {
  39         .trace          = print_syscall_exit,
  40 };
  41
  42 struct ftrace_event_class event_class_syscall_enter = {
  43         .system         = "syscalls",
  44         .reg            = syscall_enter_register,
  45         .define_fields  = syscall_enter_define_fields,
  46         .get_fields     = syscall_get_enter_fields,
  47         .raw_init       = init_syscall_trace,
  48 };
  49
  50 struct ftrace_event_class event_class_syscall_exit = {
  51         .system         = "syscalls",
  52         .reg            = syscall_exit_register,
  53         .define_fields  = syscall_exit_define_fields,
  54         .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
  55         .raw_init       = init_syscall_trace,
  56 };
  57
  58 extern struct syscall_metadata *__start_syscalls_metadata[];
  59 extern struct syscall_metadata *__stop_syscalls_metadata[];
  60
  61 static struct syscall_metadata **syscalls_metadata;
  62
  63 static __init struct syscall_metadata *
  64 find_syscall_meta(unsigned long syscall)
  65 {
  66         struct syscall_metadata **start;
  67         struct syscall_metadata **stop;
  68         char str[KSYM_SYMBOL_LEN];
  69
  70
  71         start = __start_syscalls_metadata;
  72         stop = __stop_syscalls_metadata;
  73         kallsyms_lookup(syscall, NULL, NULL, NULL, str);
  74
  75         for ( ; start < stop; start++) {
  76                 /*
  77                  * Only compare after the "sys" prefix. Archs that use
  78                  * syscall wrappers may have syscalls symbols aliases prefixed
  79                  * with "SyS" instead of "sys", leading to an unwanted
  80                  * mismatch.
  81                  */
  82                 if ((*start)->name && !strcmp((*start)->name + 3, str + 3))
  83                         return *start;
  84         }
  85         return NULL;
  86 }
  87
  88 static struct syscall_metadata *syscall_nr_to_meta(int nr)
  89 {
  90         if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
  91                 return NULL;
  92
  93         return syscalls_metadata[nr];
  94 }
  95
  96 enum print_line_t
  97 print_syscall_enter(struct trace_iterator *iter, int flags,
  98                     struct trace_event *event)
  99 {
 100         struct trace_seq *s = &iter->seq;
 101         struct trace_entry *ent = iter->ent;
 102         struct syscall_trace_enter *trace;
 103         struct syscall_metadata *entry;
 104         int i, ret, syscall;
 105
 106         trace = (typeof(trace))ent;
 107         syscall = trace->nr;
 108         entry = syscall_nr_to_meta(syscall);
 109
 110         if (!entry)
 111                 goto end;
 112
 113         if (entry->enter_event->event.type != ent->type) {
 114                 WARN_ON_ONCE(1);
 115                 goto end;
 116         }
 117
 118         ret = trace_seq_printf(s, "%s(", entry->name);
 119         if (!ret)
 120                 return TRACE_TYPE_PARTIAL_LINE;
 121
 122         for (i = 0; i < entry->nb_args; i++) {
 123                 /* parameter types */
 124                 if (trace_flags & TRACE_ITER_VERBOSE) {
 125                         ret = trace_seq_printf(s, "%s ", entry->types[i]);
 126                         if (!ret)
 127                                 return TRACE_TYPE_PARTIAL_LINE;
 128                 }
 129                 /* parameter values */
 130                 ret = trace_seq_printf(s, "%s: %lx%s", entry->args[i],
 131                                        trace->args[i],
 132                                        i == entry->nb_args - 1 ? "" : ", ");
 133                 if (!ret)
 134                         return TRACE_TYPE_PARTIAL_LINE;
 135         }
 136
 137         ret = trace_seq_putc(s, ')');
 138         if (!ret)
 139                 return TRACE_TYPE_PARTIAL_LINE;
 140
 141 end:
 142         ret =  trace_seq_putc(s, '\n');
 143         if (!ret)
 144                 return TRACE_TYPE_PARTIAL_LINE;
 145
 146         return TRACE_TYPE_HANDLED;
 147 }
 148
 149 enum print_line_t
 150 print_syscall_exit(struct trace_iterator *iter, int flags,
 151                    struct trace_event *event)
 152 {
 153         struct trace_seq *s = &iter->seq;
 154         struct trace_entry *ent = iter->ent;
 155         struct syscall_trace_exit *trace;
 156         int syscall;
 157         struct syscall_metadata *entry;
 158         int ret;
 159
 160         trace = (typeof(trace))ent;
 161         syscall = trace->nr;
 162         entry = syscall_nr_to_meta(syscall);
 163
 164         if (!entry) {
 165                 trace_seq_printf(s, "\n");
 166                 return TRACE_TYPE_HANDLED;
 167         }
 168
 169         if (entry->exit_event->event.type != ent->type) {
 170                 WARN_ON_ONCE(1);
 171                 return TRACE_TYPE_UNHANDLED;
 172         }
 173
 174         ret = trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
 175                                 trace->ret);
 176         if (!ret)
 177                 return TRACE_TYPE_PARTIAL_LINE;
 178
 179         return TRACE_TYPE_HANDLED;
 180 }
 181
 182 extern char *__bad_type_size(void);
 183
 184 #define SYSCALL_FIELD(type, name)                                       \
 185         sizeof(type) != sizeof(trace.name) ?                            \
 186                 __bad_type_size() :                                     \
 187                 #type, #name, offsetof(typeof(trace), name),            \
 188                 sizeof(trace.name), is_signed_type(type)
 189
 190 static
 191 int  __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 192 {
 193         int i;
 194         int pos = 0;
 195
 196         /* When len=0, we just calculate the needed length */
 197 #define LEN_OR_ZERO (len ? len - pos : 0)
 198
 199         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 200         for (i = 0; i < entry->nb_args; i++) {
 201                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 202                                 entry->args[i], sizeof(unsigned long),
 203                                 i == entry->nb_args - 1 ? "" : ", ");
 204         }
 205         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 206
 207         for (i = 0; i < entry->nb_args; i++) {
 208                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 209                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 210         }
 211
 212 #undef LEN_OR_ZERO
 213
 214         /* return the length of print_fmt */
 215         return pos;
 216 }
 217
 218 static int set_syscall_print_fmt(struct ftrace_event_call *call)
 219 {
 220         char *print_fmt;
 221         int len;
 222         struct syscall_metadata *entry = call->data;
 223
 224         if (entry->enter_event != call) {
 225                 call->print_fmt = "\"0x%lx\", REC->ret";
 226                 return 0;
 227         }
 228
 229         /* First: called with 0 length to calculate the needed length */
 230         len = __set_enter_print_fmt(entry, NULL, 0);
 231
 232         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 233         if (!print_fmt)
 234                 return -ENOMEM;
 235
 236         /* Second: actually write the @print_fmt */
 237         __set_enter_print_fmt(entry, print_fmt, len + 1);
 238         call->print_fmt = print_fmt;
 239
 240         return 0;
 241 }
 242
 243 static void free_syscall_print_fmt(struct ftrace_event_call *call)
 244 {
 245         struct syscall_metadata *entry = call->data;
 246
 247         if (entry->enter_event == call)
 248                 kfree(call->print_fmt);
 249 }
 250
 251 static int syscall_enter_define_fields(struct ftrace_event_call *call)
 252 {
 253         struct syscall_trace_enter trace;
 254         struct syscall_metadata *meta = call->data;
 255         int ret;
 256         int i;
 257         int offset = offsetof(typeof(trace), args);
 258
 259         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 260         if (ret)
 261                 return ret;
 262
 263         for (i = 0; i < meta->nb_args; i++) {
 264                 ret = trace_define_field(call, meta->types[i],
 265                                          meta->args[i], offset,
 266                                          sizeof(unsigned long), 0,
 267                                          FILTER_OTHER);
 268                 offset += sizeof(unsigned long);
 269         }
 270
 271         return ret;
 272 }
 273
 274 static int syscall_exit_define_fields(struct ftrace_event_call *call)
 275 {
 276         struct syscall_trace_exit trace;
 277         int ret;
 278
 279         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 280         if (ret)
 281                 return ret;
 282
 283         ret = trace_define_field(call, SYSCALL_FIELD(long, ret),
 284                                  FILTER_OTHER);
 285
 286         return ret;
 287 }
 288
 289 void ftrace_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 290 {
 291         struct syscall_trace_enter *entry;
 292         struct syscall_metadata *sys_data;
 293         struct ring_buffer_event *event;
 294         struct ring_buffer *buffer;
 295         int size;
 296         int syscall_nr;
 297
 298         syscall_nr = syscall_get_nr(current, regs);
 299         if (syscall_nr < 0)
 300                 return;
 301         if (!test_bit(syscall_nr, enabled_enter_syscalls))
 302                 return;
 303
 304         sys_data = syscall_nr_to_meta(syscall_nr);
 305         if (!sys_data)
 306                 return;
 307
 308         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 309
 310         event = trace_current_buffer_lock_reserve(&buffer,
 311                         sys_data->enter_event->event.type, size, 0, 0);
 312         if (!event)
 313                 return;
 314
 315         entry = ring_buffer_event_data(event);
 316         entry->nr = syscall_nr;
 317         syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
 318
 319         if (!filter_current_check_discard(buffer, sys_data->enter_event,
 320                                           entry, event))
 321                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 322 }
 323
 324 void ftrace_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 325 {
 326         struct syscall_trace_exit *entry;
 327         struct syscall_metadata *sys_data;
 328         struct ring_buffer_event *event;
 329         struct ring_buffer *buffer;
 330         int syscall_nr;
 331
 332         syscall_nr = syscall_get_nr(current, regs);
 333         if (syscall_nr < 0)
 334                 return;
 335         if (!test_bit(syscall_nr, enabled_exit_syscalls))
 336                 return;
 337
 338         sys_data = syscall_nr_to_meta(syscall_nr);
 339         if (!sys_data)
 340                 return;
 341
 342         event = trace_current_buffer_lock_reserve(&buffer,
 343                         sys_data->exit_event->event.type, sizeof(*entry), 0, 0);
 344         if (!event)
 345                 return;
 346
 347         entry = ring_buffer_event_data(event);
 348         entry->nr = syscall_nr;
 349         entry->ret = syscall_get_return_value(current, regs);
 350
 351         if (!filter_current_check_discard(buffer, sys_data->exit_event,
 352                                           entry, event))
 353                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 354 }
 355
 356 int reg_event_syscall_enter(struct ftrace_event_call *call)
 357 {
 358         int ret = 0;
 359         int num;
 360
 361         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 362         if (num < 0 || num >= NR_syscalls)
 363                 return -ENOSYS;
 364         mutex_lock(&syscall_trace_lock);
 365         if (!sys_refcount_enter)
 366                 ret = register_trace_sys_enter(ftrace_syscall_enter, NULL);
 367         if (!ret) {
 368                 set_bit(num, enabled_enter_syscalls);
 369                 sys_refcount_enter++;
 370         }
 371         mutex_unlock(&syscall_trace_lock);
 372         return ret;
 373 }
 374
 375 void unreg_event_syscall_enter(struct ftrace_event_call *call)
 376 {
 377         int num;
 378
 379         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 380         if (num < 0 || num >= NR_syscalls)
 381                 return;
 382         mutex_lock(&syscall_trace_lock);
 383         sys_refcount_enter--;
 384         clear_bit(num, enabled_enter_syscalls);
 385         if (!sys_refcount_enter)
 386                 unregister_trace_sys_enter(ftrace_syscall_enter, NULL);
 387         mutex_unlock(&syscall_trace_lock);
 388 }
 389
 390 int reg_event_syscall_exit(struct ftrace_event_call *call)
 391 {
 392         int ret = 0;
 393         int num;
 394
 395         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 396         if (num < 0 || num >= NR_syscalls)
 397                 return -ENOSYS;
 398         mutex_lock(&syscall_trace_lock);
 399         if (!sys_refcount_exit)
 400                 ret = register_trace_sys_exit(ftrace_syscall_exit, NULL);
 401         if (!ret) {
 402                 set_bit(num, enabled_exit_syscalls);
 403                 sys_refcount_exit++;
 404         }
 405         mutex_unlock(&syscall_trace_lock);
 406         return ret;
 407 }
 408
 409 void unreg_event_syscall_exit(struct ftrace_event_call *call)
 410 {
 411         int num;
 412
 413         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 414         if (num < 0 || num >= NR_syscalls)
 415                 return;
 416         mutex_lock(&syscall_trace_lock);
 417         sys_refcount_exit--;
 418         clear_bit(num, enabled_exit_syscalls);
 419         if (!sys_refcount_exit)
 420                 unregister_trace_sys_exit(ftrace_syscall_exit, NULL);
 421         mutex_unlock(&syscall_trace_lock);
 422 }
 423
 424 int init_syscall_trace(struct ftrace_event_call *call)
 425 {
 426         int id;
 427         int num;
 428
 429         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 430         if (num < 0 || num >= NR_syscalls) {
 431                 pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
 432                                 ((struct syscall_metadata *)call->data)->name);
 433                 return -ENOSYS;
 434         }
 435
 436         if (set_syscall_print_fmt(call) < 0)
 437                 return -ENOMEM;
 438
 439         id = trace_event_raw_init(call);
 440
 441         if (id < 0) {
 442                 free_syscall_print_fmt(call);
 443                 return id;
 444         }
 445
 446         return id;
 447 }
 448
 449 unsigned long __init arch_syscall_addr(int nr)
 450 {
 451         return (unsigned long)sys_call_table[nr];
 452 }
 453
 454 int __init init_ftrace_syscalls(void)
 455 {
 456         struct syscall_metadata *meta;
 457         unsigned long addr;
 458         int i;
 459
 460         syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
 461                                         NR_syscalls, GFP_KERNEL);
 462         if (!syscalls_metadata) {
 463                 WARN_ON(1);
 464                 return -ENOMEM;
 465         }
 466
 467         for (i = 0; i < NR_syscalls; i++) {
 468                 addr = arch_syscall_addr(i);
 469                 meta = find_syscall_meta(addr);
 470                 if (!meta)
 471                         continue;
 472
 473                 meta->syscall_nr = i;
 474                 syscalls_metadata[i] = meta;
 475         }
 476
 477         return 0;
 478 }
 479 core_initcall(init_ftrace_syscalls);
 480
 481 #ifdef CONFIG_PERF_EVENTS
 482
 483 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 484 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 485 static int sys_perf_refcount_enter;
 486 static int sys_perf_refcount_exit;
 487
 488 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 489 {
 490         struct syscall_metadata *sys_data;
 491         struct syscall_trace_enter *rec;
 492         struct hlist_head *head;
 493         int syscall_nr;
 494         int rctx;
 495         int size;
 496
 497         syscall_nr = syscall_get_nr(current, regs);
 498         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 499                 return;
 500
 501         sys_data = syscall_nr_to_meta(syscall_nr);
 502         if (!sys_data)
 503                 return;
 504
 505         /* get the size after alignment with the u32 buffer size field */
 506         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 507         size = ALIGN(size + sizeof(u32), sizeof(u64));
 508         size -= sizeof(u32);
 509
 510         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
 511                       "perf buffer not large enough"))
 512                 return;
 513
 514         rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
 515                                 sys_data->enter_event->event.type, regs, &rctx);
 516         if (!rec)
 517                 return;
 518
 519         rec->nr = syscall_nr;
 520         syscall_get_arguments(current, regs, 0, sys_data->nb_args,
 521                                (unsigned long *)&rec->args);
 522
 523         head = this_cpu_ptr(sys_data->enter_event->perf_events);
 524         perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head);
 525 }
 526
 527 int perf_sysenter_enable(struct ftrace_event_call *call)
 528 {
 529         int ret = 0;
 530         int num;
 531
 532         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 533
 534         mutex_lock(&syscall_trace_lock);
 535         if (!sys_perf_refcount_enter)
 536                 ret = register_trace_sys_enter(perf_syscall_enter, NULL);
 537         if (ret) {
 538                 pr_info("event trace: Could not activate"
 539                                 "syscall entry trace point");
 540         } else {
 541                 set_bit(num, enabled_perf_enter_syscalls);
 542                 sys_perf_refcount_enter++;
 543         }
 544         mutex_unlock(&syscall_trace_lock);
 545         return ret;
 546 }
 547
 548 void perf_sysenter_disable(struct ftrace_event_call *call)
 549 {
 550         int num;
 551
 552         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 553
 554         mutex_lock(&syscall_trace_lock);
 555         sys_perf_refcount_enter--;
 556         clear_bit(num, enabled_perf_enter_syscalls);
 557         if (!sys_perf_refcount_enter)
 558                 unregister_trace_sys_enter(perf_syscall_enter, NULL);
 559         mutex_unlock(&syscall_trace_lock);
 560 }
 561
 562 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 563 {
 564         struct syscall_metadata *sys_data;
 565         struct syscall_trace_exit *rec;
 566         struct hlist_head *head;
 567         int syscall_nr;
 568         int rctx;
 569         int size;
 570
 571         syscall_nr = syscall_get_nr(current, regs);
 572         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 573                 return;
 574
 575         sys_data = syscall_nr_to_meta(syscall_nr);
 576         if (!sys_data)
 577                 return;
 578
 579         /* We can probably do that at build time */
 580         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 581         size -= sizeof(u32);
 582
 583         /*
 584          * Impossible, but be paranoid with the future
 585          * How to put this check outside runtime?
 586          */
 587         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
 588                 "exit event has grown above perf buffer size"))
 589                 return;
 590
 591         rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
 592                                 sys_data->exit_event->event.type, regs, &rctx);
 593         if (!rec)
 594                 return;
 595
 596         rec->nr = syscall_nr;
 597         rec->ret = syscall_get_return_value(current, regs);
 598
 599         head = this_cpu_ptr(sys_data->exit_event->perf_events);
 600         perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head);
 601 }
 602
 603 int perf_sysexit_enable(struct ftrace_event_call *call)
 604 {
 605         int ret = 0;
 606         int num;
 607
 608         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 609
 610         mutex_lock(&syscall_trace_lock);
 611         if (!sys_perf_refcount_exit)
 612                 ret = register_trace_sys_exit(perf_syscall_exit, NULL);
 613         if (ret) {
 614                 pr_info("event trace: Could not activate"
 615                                 "syscall exit trace point");
 616         } else {
 617                 set_bit(num, enabled_perf_exit_syscalls);
 618                 sys_perf_refcount_exit++;
 619         }
 620         mutex_unlock(&syscall_trace_lock);
 621         return ret;
 622 }
 623
 624 void perf_sysexit_disable(struct ftrace_event_call *call)
 625 {
 626         int num;
 627
 628         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 629
 630         mutex_lock(&syscall_trace_lock);
 631         sys_perf_refcount_exit--;
 632         clear_bit(num, enabled_perf_exit_syscalls);
 633         if (!sys_perf_refcount_exit)
 634                 unregister_trace_sys_exit(perf_syscall_exit, NULL);
 635         mutex_unlock(&syscall_trace_lock);
 636 }
 637
 638 #endif /* CONFIG_PERF_EVENTS */
 639
 640 static int syscall_enter_register(struct ftrace_event_call *event,
 641                                  enum trace_reg type)
 642 {
 643         switch (type) {
 644         case TRACE_REG_REGISTER:
 645                 return reg_event_syscall_enter(event);
 646         case TRACE_REG_UNREGISTER:
 647                 unreg_event_syscall_enter(event);
 648                 return 0;
 649
 650 #ifdef CONFIG_PERF_EVENTS
 651         case TRACE_REG_PERF_REGISTER:
 652                 return perf_sysenter_enable(event);
 653         case TRACE_REG_PERF_UNREGISTER:
 654                 perf_sysenter_disable(event);
 655                 return 0;
 656 #endif
 657         }
 658         return 0;
 659 }
 660
 661 static int syscall_exit_register(struct ftrace_event_call *event,
 662                                  enum trace_reg type)
 663 {
 664         switch (type) {
 665         case TRACE_REG_REGISTER:
 666                 return reg_event_syscall_exit(event);
 667         case TRACE_REG_UNREGISTER:
 668                 unreg_event_syscall_exit(event);
 669                 return 0;
 670
 671 #ifdef CONFIG_PERF_EVENTS
 672         case TRACE_REG_PERF_REGISTER:
 673                 return perf_sysexit_enable(event);
 674         case TRACE_REG_PERF_UNREGISTER:
 675                 perf_sysexit_disable(event);
 676                 return 0;
 677 #endif
 678         }
 679         return 0;
 680 }