kernel/trace/trace_syscalls.c

   1 #include <trace/syscall.h>
   2 #include <trace/events/syscalls.h>
   3 #include <linux/syscalls.h>
   4 #include <linux/slab.h>
   5 #include <linux/kernel.h>
   6 #include <linux/module.h>       /* for MODULE_NAME_LEN via KSYM_SYMBOL_LEN */
   7 #include <linux/ftrace.h>
   8 #include <linux/perf_event.h>
   9 #include <asm/syscall.h>
  10
  11 #include "trace_output.h"
  12 #include "trace.h"
  13
  14 static DEFINE_MUTEX(syscall_trace_lock);
  15
  16 static int syscall_enter_register(struct trace_event_call *event,
  17                                  enum trace_reg type, void *data);
  18 static int syscall_exit_register(struct trace_event_call *event,
  19                                  enum trace_reg type, void *data);
  20
  21 static struct list_head *
  22 syscall_get_enter_fields(struct trace_event_call *call)
  23 {
  24         struct syscall_metadata *entry = call->data;
  25
  26         return &entry->enter_fields;
  27 }
  28
  29 extern struct syscall_metadata *__start_syscalls_metadata[];
  30 extern struct syscall_metadata *__stop_syscalls_metadata[];
  31
  32 static struct syscall_metadata **syscalls_metadata;
  33
  34 #ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
  35 static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
  36 {
  37         /*
  38          * Only compare after the "sys" prefix. Archs that use
  39          * syscall wrappers may have syscalls symbols aliases prefixed
  40          * with ".SyS" or ".sys" instead of "sys", leading to an unwanted
  41          * mismatch.
  42          */
  43         return !strcmp(sym + 3, name + 3);
  44 }
  45 #endif
  46
  47 #ifdef ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
  48 /*
  49  * Some architectures that allow for 32bit applications
  50  * to run on a 64bit kernel, do not map the syscalls for
  51  * the 32bit tasks the same as they do for 64bit tasks.
  52  *
  53  *     *cough*x86*cough*
  54  *
  55  * In such a case, instead of reporting the wrong syscalls,
  56  * simply ignore them.
  57  *
  58  * For an arch to ignore the compat syscalls it needs to
  59  * define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS as well as
  60  * define the function arch_trace_is_compat_syscall() to let
  61  * the tracing system know that it should ignore it.
  62  */
  63 static int
  64 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
  65 {
  66         if (unlikely(arch_trace_is_compat_syscall(regs)))
  67                 return -1;
  68
  69         return syscall_get_nr(task, regs);
  70 }
  71 #else
  72 static inline int
  73 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
  74 {
  75         return syscall_get_nr(task, regs);
  76 }
  77 #endif /* ARCH_TRACE_IGNORE_COMPAT_SYSCALLS */
  78
  79 static __init struct syscall_metadata *
  80 find_syscall_meta(unsigned long syscall)
  81 {
  82         struct syscall_metadata **start;
  83         struct syscall_metadata **stop;
  84         char str[KSYM_SYMBOL_LEN];
  85
  86
  87         start = __start_syscalls_metadata;
  88         stop = __stop_syscalls_metadata;
  89         kallsyms_lookup(syscall, NULL, NULL, NULL, str);
  90
  91         if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
  92                 return NULL;
  93
  94         for ( ; start < stop; start++) {
  95                 if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
  96                         return *start;
  97         }
  98         return NULL;
  99 }
 100
 101 static struct syscall_metadata *syscall_nr_to_meta(int nr)
 102 {
 103         if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
 104                 return NULL;
 105
 106         return syscalls_metadata[nr];
 107 }
 108
 109 static enum print_line_t
 110 print_syscall_enter(struct trace_iterator *iter, int flags,
 111                     struct trace_event *event)
 112 {
 113         struct trace_array *tr = iter->tr;
 114         struct trace_seq *s = &iter->seq;
 115         struct trace_entry *ent = iter->ent;
 116         struct syscall_trace_enter *trace;
 117         struct syscall_metadata *entry;
 118         int i, syscall;
 119
 120         trace = (typeof(trace))ent;
 121         syscall = trace->nr;
 122         entry = syscall_nr_to_meta(syscall);
 123
 124         if (!entry)
 125                 goto end;
 126
 127         if (entry->enter_event->event.type != ent->type) {
 128                 WARN_ON_ONCE(1);
 129                 goto end;
 130         }
 131
 132         trace_seq_printf(s, "%s(", entry->name);
 133
 134         for (i = 0; i < entry->nb_args; i++) {
 135
 136                 if (trace_seq_has_overflowed(s))
 137                         goto end;
 138
 139                 /* parameter types */
 140                 if (tr->trace_flags & TRACE_ITER_VERBOSE)
 141                         trace_seq_printf(s, "%s ", entry->types[i]);
 142
 143                 /* parameter values */
 144                 trace_seq_printf(s, "%s: %lx%s", entry->args[i],
 145                                  trace->args[i],
 146                                  i == entry->nb_args - 1 ? "" : ", ");
 147         }
 148
 149         trace_seq_putc(s, ')');
 150 end:
 151         trace_seq_putc(s, '\n');
 152
 153         return trace_handle_return(s);
 154 }
 155
 156 static enum print_line_t
 157 print_syscall_exit(struct trace_iterator *iter, int flags,
 158                    struct trace_event *event)
 159 {
 160         struct trace_seq *s = &iter->seq;
 161         struct trace_entry *ent = iter->ent;
 162         struct syscall_trace_exit *trace;
 163         int syscall;
 164         struct syscall_metadata *entry;
 165
 166         trace = (typeof(trace))ent;
 167         syscall = trace->nr;
 168         entry = syscall_nr_to_meta(syscall);
 169
 170         if (!entry) {
 171                 trace_seq_putc(s, '\n');
 172                 goto out;
 173         }
 174
 175         if (entry->exit_event->event.type != ent->type) {
 176                 WARN_ON_ONCE(1);
 177                 return TRACE_TYPE_UNHANDLED;
 178         }
 179
 180         trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
 181                                 trace->ret);
 182
 183  out:
 184         return trace_handle_return(s);
 185 }
 186
 187 extern char *__bad_type_size(void);
 188
 189 #define SYSCALL_FIELD(type, field, name)                                \
 190         sizeof(type) != sizeof(trace.field) ?                           \
 191                 __bad_type_size() :                                     \
 192                 #type, #name, offsetof(typeof(trace), field),           \
 193                 sizeof(trace.field), is_signed_type(type)
 194
 195 static int __init
 196 __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 197 {
 198         int i;
 199         int pos = 0;
 200
 201         /* When len=0, we just calculate the needed length */
 202 #define LEN_OR_ZERO (len ? len - pos : 0)
 203
 204         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 205         for (i = 0; i < entry->nb_args; i++) {
 206                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 207                                 entry->args[i], sizeof(unsigned long),
 208                                 i == entry->nb_args - 1 ? "" : ", ");
 209         }
 210         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 211
 212         for (i = 0; i < entry->nb_args; i++) {
 213                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 214                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 215         }
 216
 217 #undef LEN_OR_ZERO
 218
 219         /* return the length of print_fmt */
 220         return pos;
 221 }
 222
 223 static int __init set_syscall_print_fmt(struct trace_event_call *call)
 224 {
 225         char *print_fmt;
 226         int len;
 227         struct syscall_metadata *entry = call->data;
 228
 229         if (entry->enter_event != call) {
 230                 call->print_fmt = "\"0x%lx\", REC->ret";
 231                 return 0;
 232         }
 233
 234         /* First: called with 0 length to calculate the needed length */
 235         len = __set_enter_print_fmt(entry, NULL, 0);
 236
 237         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 238         if (!print_fmt)
 239                 return -ENOMEM;
 240
 241         /* Second: actually write the @print_fmt */
 242         __set_enter_print_fmt(entry, print_fmt, len + 1);
 243         call->print_fmt = print_fmt;
 244
 245         return 0;
 246 }
 247
 248 static void __init free_syscall_print_fmt(struct trace_event_call *call)
 249 {
 250         struct syscall_metadata *entry = call->data;
 251
 252         if (entry->enter_event == call)
 253                 kfree(call->print_fmt);
 254 }
 255
 256 static int __init syscall_enter_define_fields(struct trace_event_call *call)
 257 {
 258         struct syscall_trace_enter trace;
 259         struct syscall_metadata *meta = call->data;
 260         int ret;
 261         int i;
 262         int offset = offsetof(typeof(trace), args);
 263
 264         ret = trace_define_field(call, SYSCALL_FIELD(int, nr, __syscall_nr),
 265                                  FILTER_OTHER);
 266         if (ret)
 267                 return ret;
 268
 269         for (i = 0; i < meta->nb_args; i++) {
 270                 ret = trace_define_field(call, meta->types[i],
 271                                          meta->args[i], offset,
 272                                          sizeof(unsigned long), 0,
 273                                          FILTER_OTHER);
 274                 offset += sizeof(unsigned long);
 275         }
 276
 277         return ret;
 278 }
 279
 280 static int __init syscall_exit_define_fields(struct trace_event_call *call)
 281 {
 282         struct syscall_trace_exit trace;
 283         int ret;
 284
 285         ret = trace_define_field(call, SYSCALL_FIELD(int, nr, __syscall_nr),
 286                                  FILTER_OTHER);
 287         if (ret)
 288                 return ret;
 289
 290         ret = trace_define_field(call, SYSCALL_FIELD(long, ret, ret),
 291                                  FILTER_OTHER);
 292
 293         return ret;
 294 }
 295
 296 static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 297 {
 298         struct trace_array *tr = data;
 299         struct trace_event_file *trace_file;
 300         struct syscall_trace_enter *entry;
 301         struct syscall_metadata *sys_data;
 302         struct ring_buffer_event *event;
 303         struct ring_buffer *buffer;
 304         unsigned long irq_flags;
 305         int pc;
 306         int syscall_nr;
 307         int size;
 308
 309         syscall_nr = trace_get_syscall_nr(current, regs);
 310         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 311                 return;
 312
 313         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE) */
 314         trace_file = rcu_dereference_sched(tr->enter_syscall_files[syscall_nr]);
 315         if (!trace_file)
 316                 return;
 317
 318         if (trace_trigger_soft_disabled(trace_file))
 319                 return;
 320
 321         sys_data = syscall_nr_to_meta(syscall_nr);
 322         if (!sys_data)
 323                 return;
 324
 325         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 326
 327         local_save_flags(irq_flags);
 328         pc = preempt_count();
 329
 330         buffer = tr->trace_buffer.buffer;
 331         event = trace_buffer_lock_reserve(buffer,
 332                         sys_data->enter_event->event.type, size, irq_flags, pc);
 333         if (!event)
 334                 return;
 335
 336         entry = ring_buffer_event_data(event);
 337         entry->nr = syscall_nr;
 338         syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
 339
 340         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 341                                     irq_flags, pc);
 342 }
 343
 344 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
 345 {
 346         struct trace_array *tr = data;
 347         struct trace_event_file *trace_file;
 348         struct syscall_trace_exit *entry;
 349         struct syscall_metadata *sys_data;
 350         struct ring_buffer_event *event;
 351         struct ring_buffer *buffer;
 352         unsigned long irq_flags;
 353         int pc;
 354         int syscall_nr;
 355
 356         syscall_nr = trace_get_syscall_nr(current, regs);
 357         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 358                 return;
 359
 360         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE()) */
 361         trace_file = rcu_dereference_sched(tr->exit_syscall_files[syscall_nr]);
 362         if (!trace_file)
 363                 return;
 364
 365         if (trace_trigger_soft_disabled(trace_file))
 366                 return;
 367
 368         sys_data = syscall_nr_to_meta(syscall_nr);
 369         if (!sys_data)
 370                 return;
 371
 372         local_save_flags(irq_flags);
 373         pc = preempt_count();
 374
 375         buffer = tr->trace_buffer.buffer;
 376         event = trace_buffer_lock_reserve(buffer,
 377                         sys_data->exit_event->event.type, sizeof(*entry),
 378                         irq_flags, pc);
 379         if (!event)
 380                 return;
 381
 382         entry = ring_buffer_event_data(event);
 383         entry->nr = syscall_nr;
 384         entry->ret = syscall_get_return_value(current, regs);
 385
 386         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 387                                     irq_flags, pc);
 388 }
 389
 390 static int reg_event_syscall_enter(struct trace_event_file *file,
 391                                    struct trace_event_call *call)
 392 {
 393         struct trace_array *tr = file->tr;
 394         int ret = 0;
 395         int num;
 396
 397         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 398         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 399                 return -ENOSYS;
 400         mutex_lock(&syscall_trace_lock);
 401         if (!tr->sys_refcount_enter)
 402                 ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
 403         if (!ret) {
 404                 rcu_assign_pointer(tr->enter_syscall_files[num], file);
 405                 tr->sys_refcount_enter++;
 406         }
 407         mutex_unlock(&syscall_trace_lock);
 408         return ret;
 409 }
 410
 411 static void unreg_event_syscall_enter(struct trace_event_file *file,
 412                                       struct trace_event_call *call)
 413 {
 414         struct trace_array *tr = file->tr;
 415         int num;
 416
 417         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 418         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 419                 return;
 420         mutex_lock(&syscall_trace_lock);
 421         tr->sys_refcount_enter--;
 422         RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
 423         if (!tr->sys_refcount_enter)
 424                 unregister_trace_sys_enter(ftrace_syscall_enter, tr);
 425         mutex_unlock(&syscall_trace_lock);
 426 }
 427
 428 static int reg_event_syscall_exit(struct trace_event_file *file,
 429                                   struct trace_event_call *call)
 430 {
 431         struct trace_array *tr = file->tr;
 432         int ret = 0;
 433         int num;
 434
 435         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 436         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 437                 return -ENOSYS;
 438         mutex_lock(&syscall_trace_lock);
 439         if (!tr->sys_refcount_exit)
 440                 ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
 441         if (!ret) {
 442                 rcu_assign_pointer(tr->exit_syscall_files[num], file);
 443                 tr->sys_refcount_exit++;
 444         }
 445         mutex_unlock(&syscall_trace_lock);
 446         return ret;
 447 }
 448
 449 static void unreg_event_syscall_exit(struct trace_event_file *file,
 450                                      struct trace_event_call *call)
 451 {
 452         struct trace_array *tr = file->tr;
 453         int num;
 454
 455         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 456         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 457                 return;
 458         mutex_lock(&syscall_trace_lock);
 459         tr->sys_refcount_exit--;
 460         RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
 461         if (!tr->sys_refcount_exit)
 462                 unregister_trace_sys_exit(ftrace_syscall_exit, tr);
 463         mutex_unlock(&syscall_trace_lock);
 464 }
 465
 466 static int __init init_syscall_trace(struct trace_event_call *call)
 467 {
 468         int id;
 469         int num;
 470
 471         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 472         if (num < 0 || num >= NR_syscalls) {
 473                 pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
 474                                 ((struct syscall_metadata *)call->data)->name);
 475                 return -ENOSYS;
 476         }
 477
 478         if (set_syscall_print_fmt(call) < 0)
 479                 return -ENOMEM;
 480
 481         id = trace_event_raw_init(call);
 482
 483         if (id < 0) {
 484                 free_syscall_print_fmt(call);
 485                 return id;
 486         }
 487
 488         return id;
 489 }
 490
 491 struct trace_event_functions enter_syscall_print_funcs = {
 492         .trace          = print_syscall_enter,
 493 };
 494
 495 struct trace_event_functions exit_syscall_print_funcs = {
 496         .trace          = print_syscall_exit,
 497 };
 498
 499 struct trace_event_class __refdata event_class_syscall_enter = {
 500         .system         = "syscalls",
 501         .reg            = syscall_enter_register,
 502         .define_fields  = syscall_enter_define_fields,
 503         .get_fields     = syscall_get_enter_fields,
 504         .raw_init       = init_syscall_trace,
 505 };
 506
 507 struct trace_event_class __refdata event_class_syscall_exit = {
 508         .system         = "syscalls",
 509         .reg            = syscall_exit_register,
 510         .define_fields  = syscall_exit_define_fields,
 511         .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
 512         .raw_init       = init_syscall_trace,
 513 };
 514
 515 unsigned long __init __weak arch_syscall_addr(int nr)
 516 {
 517         return (unsigned long)sys_call_table[nr];
 518 }
 519
 520 void __init init_ftrace_syscalls(void)
 521 {
 522         struct syscall_metadata *meta;
 523         unsigned long addr;
 524         int i;
 525
 526         syscalls_metadata = kcalloc(NR_syscalls, sizeof(*syscalls_metadata),
 527                                     GFP_KERNEL);
 528         if (!syscalls_metadata) {
 529                 WARN_ON(1);
 530                 return;
 531         }
 532
 533         for (i = 0; i < NR_syscalls; i++) {
 534                 addr = arch_syscall_addr(i);
 535                 meta = find_syscall_meta(addr);
 536                 if (!meta)
 537                         continue;
 538
 539                 meta->syscall_nr = i;
 540                 syscalls_metadata[i] = meta;
 541         }
 542 }
 543
 544 #ifdef CONFIG_PERF_EVENTS
 545
 546 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 547 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 548 static int sys_perf_refcount_enter;
 549 static int sys_perf_refcount_exit;
 550
 551 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 552 {
 553         struct syscall_metadata *sys_data;
 554         struct syscall_trace_enter *rec;
 555         struct hlist_head *head;
 556         int syscall_nr;
 557         int rctx;
 558         int size;
 559
 560         syscall_nr = trace_get_syscall_nr(current, regs);
 561         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 562                 return;
 563         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 564                 return;
 565
 566         sys_data = syscall_nr_to_meta(syscall_nr);
 567         if (!sys_data)
 568                 return;
 569
 570         head = this_cpu_ptr(sys_data->enter_event->perf_events);
 571         if (hlist_empty(head))
 572                 return;
 573
 574         /* get the size after alignment with the u32 buffer size field */
 575         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 576         size = ALIGN(size + sizeof(u32), sizeof(u64));
 577         size -= sizeof(u32);
 578
 579         rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
 580                                 sys_data->enter_event->event.type, NULL, &rctx);
 581         if (!rec)
 582                 return;
 583
 584         rec->nr = syscall_nr;
 585         syscall_get_arguments(current, regs, 0, sys_data->nb_args,
 586                                (unsigned long *)&rec->args);
 587         perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
 588 }
 589
 590 static int perf_sysenter_enable(struct trace_event_call *call)
 591 {
 592         int ret = 0;
 593         int num;
 594
 595         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 596
 597         mutex_lock(&syscall_trace_lock);
 598         if (!sys_perf_refcount_enter)
 599                 ret = register_trace_sys_enter(perf_syscall_enter, NULL);
 600         if (ret) {
 601                 pr_info("event trace: Could not activate"
 602                                 "syscall entry trace point");
 603         } else {
 604                 set_bit(num, enabled_perf_enter_syscalls);
 605                 sys_perf_refcount_enter++;
 606         }
 607         mutex_unlock(&syscall_trace_lock);
 608         return ret;
 609 }
 610
 611 static void perf_sysenter_disable(struct trace_event_call *call)
 612 {
 613         int num;
 614
 615         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 616
 617         mutex_lock(&syscall_trace_lock);
 618         sys_perf_refcount_enter--;
 619         clear_bit(num, enabled_perf_enter_syscalls);
 620         if (!sys_perf_refcount_enter)
 621                 unregister_trace_sys_enter(perf_syscall_enter, NULL);
 622         mutex_unlock(&syscall_trace_lock);
 623 }
 624
 625 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 626 {
 627         struct syscall_metadata *sys_data;
 628         struct syscall_trace_exit *rec;
 629         struct hlist_head *head;
 630         int syscall_nr;
 631         int rctx;
 632         int size;
 633
 634         syscall_nr = trace_get_syscall_nr(current, regs);
 635         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 636                 return;
 637         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 638                 return;
 639
 640         sys_data = syscall_nr_to_meta(syscall_nr);
 641         if (!sys_data)
 642                 return;
 643
 644         head = this_cpu_ptr(sys_data->exit_event->perf_events);
 645         if (hlist_empty(head))
 646                 return;
 647
 648         /* We can probably do that at build time */
 649         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 650         size -= sizeof(u32);
 651
 652         rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
 653                                 sys_data->exit_event->event.type, NULL, &rctx);
 654         if (!rec)
 655                 return;
 656
 657         rec->nr = syscall_nr;
 658         rec->ret = syscall_get_return_value(current, regs);
 659         perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
 660 }
 661
 662 static int perf_sysexit_enable(struct trace_event_call *call)
 663 {
 664         int ret = 0;
 665         int num;
 666
 667         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 668
 669         mutex_lock(&syscall_trace_lock);
 670         if (!sys_perf_refcount_exit)
 671                 ret = register_trace_sys_exit(perf_syscall_exit, NULL);
 672         if (ret) {
 673                 pr_info("event trace: Could not activate"
 674                                 "syscall exit trace point");
 675         } else {
 676                 set_bit(num, enabled_perf_exit_syscalls);
 677                 sys_perf_refcount_exit++;
 678         }
 679         mutex_unlock(&syscall_trace_lock);
 680         return ret;
 681 }
 682
 683 static void perf_sysexit_disable(struct trace_event_call *call)
 684 {
 685         int num;
 686
 687         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 688
 689         mutex_lock(&syscall_trace_lock);
 690         sys_perf_refcount_exit--;
 691         clear_bit(num, enabled_perf_exit_syscalls);
 692         if (!sys_perf_refcount_exit)
 693                 unregister_trace_sys_exit(perf_syscall_exit, NULL);
 694         mutex_unlock(&syscall_trace_lock);
 695 }
 696
 697 #endif /* CONFIG_PERF_EVENTS */
 698
 699 static int syscall_enter_register(struct trace_event_call *event,
 700                                  enum trace_reg type, void *data)
 701 {
 702         struct trace_event_file *file = data;
 703
 704         switch (type) {
 705         case TRACE_REG_REGISTER:
 706                 return reg_event_syscall_enter(file, event);
 707         case TRACE_REG_UNREGISTER:
 708                 unreg_event_syscall_enter(file, event);
 709                 return 0;
 710
 711 #ifdef CONFIG_PERF_EVENTS
 712         case TRACE_REG_PERF_REGISTER:
 713                 return perf_sysenter_enable(event);
 714         case TRACE_REG_PERF_UNREGISTER:
 715                 perf_sysenter_disable(event);
 716                 return 0;
 717         case TRACE_REG_PERF_OPEN:
 718         case TRACE_REG_PERF_CLOSE:
 719         case TRACE_REG_PERF_ADD:
 720         case TRACE_REG_PERF_DEL:
 721                 return 0;
 722 #endif
 723         }
 724         return 0;
 725 }
 726
 727 static int syscall_exit_register(struct trace_event_call *event,
 728                                  enum trace_reg type, void *data)
 729 {
 730         struct trace_event_file *file = data;
 731
 732         switch (type) {
 733         case TRACE_REG_REGISTER:
 734                 return reg_event_syscall_exit(file, event);
 735         case TRACE_REG_UNREGISTER:
 736                 unreg_event_syscall_exit(file, event);
 737                 return 0;
 738
 739 #ifdef CONFIG_PERF_EVENTS
 740         case TRACE_REG_PERF_REGISTER:
 741                 return perf_sysexit_enable(event);
 742         case TRACE_REG_PERF_UNREGISTER:
 743                 perf_sysexit_disable(event);
 744                 return 0;
 745         case TRACE_REG_PERF_OPEN:
 746         case TRACE_REG_PERF_CLOSE:
 747         case TRACE_REG_PERF_ADD:
 748         case TRACE_REG_PERF_DEL:
 749                 return 0;
 750 #endif
 751         }
 752         return 0;
 753 }