kernel/trace/trace_syscalls.c

   1 #include <trace/syscall.h>
   2 #include <trace/events/syscalls.h>
   3 #include <linux/kernel.h>
   4 #include <linux/ftrace.h>
   5 #include <linux/perf_event.h>
   6 #include <asm/syscall.h>
   7
   8 #include "trace_output.h"
   9 #include "trace.h"
  10
  11 static DEFINE_MUTEX(syscall_trace_lock);
  12 static int sys_refcount_enter;
  13 static int sys_refcount_exit;
  14 static DECLARE_BITMAP(enabled_enter_syscalls, NR_syscalls);
  15 static DECLARE_BITMAP(enabled_exit_syscalls, NR_syscalls);
  16
  17 extern unsigned long __start_syscalls_metadata[];
  18 extern unsigned long __stop_syscalls_metadata[];
  19
  20 static struct syscall_metadata **syscalls_metadata;
  21
  22 static struct syscall_metadata *find_syscall_meta(unsigned long syscall)
  23 {
  24         struct syscall_metadata *start;
  25         struct syscall_metadata *stop;
  26         char str[KSYM_SYMBOL_LEN];
  27
  28
  29         start = (struct syscall_metadata *)__start_syscalls_metadata;
  30         stop = (struct syscall_metadata *)__stop_syscalls_metadata;
  31         kallsyms_lookup(syscall, NULL, NULL, NULL, str);
  32
  33         for ( ; start < stop; start++) {
  34                 /*
  35                  * Only compare after the "sys" prefix. Archs that use
  36                  * syscall wrappers may have syscalls symbols aliases prefixed
  37                  * with "SyS" instead of "sys", leading to an unwanted
  38                  * mismatch.
  39                  */
  40                 if (start->name && !strcmp(start->name + 3, str + 3))
  41                         return start;
  42         }
  43         return NULL;
  44 }
  45
  46 static struct syscall_metadata *syscall_nr_to_meta(int nr)
  47 {
  48         if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
  49                 return NULL;
  50
  51         return syscalls_metadata[nr];
  52 }
  53
  54 enum print_line_t
  55 print_syscall_enter(struct trace_iterator *iter, int flags)
  56 {
  57         struct trace_seq *s = &iter->seq;
  58         struct trace_entry *ent = iter->ent;
  59         struct syscall_trace_enter *trace;
  60         struct syscall_metadata *entry;
  61         int i, ret, syscall;
  62
  63         trace = (typeof(trace))ent;
  64         syscall = trace->nr;
  65         entry = syscall_nr_to_meta(syscall);
  66
  67         if (!entry)
  68                 goto end;
  69
  70         if (entry->enter_event->id != ent->type) {
  71                 WARN_ON_ONCE(1);
  72                 goto end;
  73         }
  74
  75         ret = trace_seq_printf(s, "%s(", entry->name);
  76         if (!ret)
  77                 return TRACE_TYPE_PARTIAL_LINE;
  78
  79         for (i = 0; i < entry->nb_args; i++) {
  80                 /* parameter types */
  81                 if (trace_flags & TRACE_ITER_VERBOSE) {
  82                         ret = trace_seq_printf(s, "%s ", entry->types[i]);
  83                         if (!ret)
  84                                 return TRACE_TYPE_PARTIAL_LINE;
  85                 }
  86                 /* parameter values */
  87                 ret = trace_seq_printf(s, "%s: %lx%s", entry->args[i],
  88                                        trace->args[i],
  89                                        i == entry->nb_args - 1 ? "" : ", ");
  90                 if (!ret)
  91                         return TRACE_TYPE_PARTIAL_LINE;
  92         }
  93
  94         ret = trace_seq_putc(s, ')');
  95         if (!ret)
  96                 return TRACE_TYPE_PARTIAL_LINE;
  97
  98 end:
  99         ret =  trace_seq_putc(s, '\n');
 100         if (!ret)
 101                 return TRACE_TYPE_PARTIAL_LINE;
 102
 103         return TRACE_TYPE_HANDLED;
 104 }
 105
 106 enum print_line_t
 107 print_syscall_exit(struct trace_iterator *iter, int flags)
 108 {
 109         struct trace_seq *s = &iter->seq;
 110         struct trace_entry *ent = iter->ent;
 111         struct syscall_trace_exit *trace;
 112         int syscall;
 113         struct syscall_metadata *entry;
 114         int ret;
 115
 116         trace = (typeof(trace))ent;
 117         syscall = trace->nr;
 118         entry = syscall_nr_to_meta(syscall);
 119
 120         if (!entry) {
 121                 trace_seq_printf(s, "\n");
 122                 return TRACE_TYPE_HANDLED;
 123         }
 124
 125         if (entry->exit_event->id != ent->type) {
 126                 WARN_ON_ONCE(1);
 127                 return TRACE_TYPE_UNHANDLED;
 128         }
 129
 130         ret = trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
 131                                 trace->ret);
 132         if (!ret)
 133                 return TRACE_TYPE_PARTIAL_LINE;
 134
 135         return TRACE_TYPE_HANDLED;
 136 }
 137
 138 extern char *__bad_type_size(void);
 139
 140 #define SYSCALL_FIELD(type, name)                                       \
 141         sizeof(type) != sizeof(trace.name) ?                            \
 142                 __bad_type_size() :                                     \
 143                 #type, #name, offsetof(typeof(trace), name),            \
 144                 sizeof(trace.name), is_signed_type(type)
 145
 146 int syscall_enter_format(struct ftrace_event_call *call, struct trace_seq *s)
 147 {
 148         int i;
 149         int ret;
 150         struct syscall_metadata *entry = call->data;
 151         struct syscall_trace_enter trace;
 152         int offset = offsetof(struct syscall_trace_enter, args);
 153
 154         ret = trace_seq_printf(s, "\tfield:%s %s;\toffset:%zu;\tsize:%zu;"
 155                                "\tsigned:%u;\n",
 156                                SYSCALL_FIELD(int, nr));
 157         if (!ret)
 158                 return 0;
 159
 160         for (i = 0; i < entry->nb_args; i++) {
 161                 ret = trace_seq_printf(s, "\tfield:%s %s;", entry->types[i],
 162                                         entry->args[i]);
 163                 if (!ret)
 164                         return 0;
 165                 ret = trace_seq_printf(s, "\toffset:%d;\tsize:%zu;"
 166                                        "\tsigned:%u;\n", offset,
 167                                        sizeof(unsigned long),
 168                                        is_signed_type(unsigned long));
 169                 if (!ret)
 170                         return 0;
 171                 offset += sizeof(unsigned long);
 172         }
 173
 174         trace_seq_puts(s, "\nprint fmt: \"");
 175         for (i = 0; i < entry->nb_args; i++) {
 176                 ret = trace_seq_printf(s, "%s: 0x%%0%zulx%s", entry->args[i],
 177                                         sizeof(unsigned long),
 178                                         i == entry->nb_args - 1 ? "" : ", ");
 179                 if (!ret)
 180                         return 0;
 181         }
 182         trace_seq_putc(s, '"');
 183
 184         for (i = 0; i < entry->nb_args; i++) {
 185                 ret = trace_seq_printf(s, ", ((unsigned long)(REC->%s))",
 186                                        entry->args[i]);
 187                 if (!ret)
 188                         return 0;
 189         }
 190
 191         return trace_seq_putc(s, '\n');
 192 }
 193
 194 static
 195 int  __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 196 {
 197         int i;
 198         int pos = 0;
 199
 200         /* When len=0, we just calculate the needed length */
 201 #define LEN_OR_ZERO (len ? len - pos : 0)
 202
 203         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 204         for (i = 0; i < entry->nb_args; i++) {
 205                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 206                                 entry->args[i], sizeof(unsigned long),
 207                                 i == entry->nb_args - 1 ? "" : ", ");
 208         }
 209         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 210
 211         for (i = 0; i < entry->nb_args; i++) {
 212                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 213                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 214         }
 215
 216 #undef LEN_OR_ZERO
 217
 218         /* return the length of print_fmt */
 219         return pos;
 220 }
 221
 222 static int set_syscall_print_fmt(struct ftrace_event_call *call)
 223 {
 224         char *print_fmt;
 225         int len;
 226         struct syscall_metadata *entry = call->data;
 227
 228         if (entry->enter_event != call) {
 229                 call->print_fmt = "\"0x%lx\", REC->ret";
 230                 return 0;
 231         }
 232
 233         /* First: called with 0 length to calculate the needed length */
 234         len = __set_enter_print_fmt(entry, NULL, 0);
 235
 236         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 237         if (!print_fmt)
 238                 return -ENOMEM;
 239
 240         /* Second: actually write the @print_fmt */
 241         __set_enter_print_fmt(entry, print_fmt, len + 1);
 242         call->print_fmt = print_fmt;
 243
 244         return 0;
 245 }
 246
 247 static void free_syscall_print_fmt(struct ftrace_event_call *call)
 248 {
 249         struct syscall_metadata *entry = call->data;
 250
 251         if (entry->enter_event == call)
 252                 kfree(call->print_fmt);
 253 }
 254
 255 int syscall_exit_format(struct ftrace_event_call *call, struct trace_seq *s)
 256 {
 257         int ret;
 258         struct syscall_trace_exit trace;
 259
 260         ret = trace_seq_printf(s,
 261                                "\tfield:%s %s;\toffset:%zu;\tsize:%zu;"
 262                                "\tsigned:%u;\n"
 263                                "\tfield:%s %s;\toffset:%zu;\tsize:%zu;"
 264                                "\tsigned:%u;\n",
 265                                SYSCALL_FIELD(int, nr),
 266                                SYSCALL_FIELD(long, ret));
 267         if (!ret)
 268                 return 0;
 269
 270         return trace_seq_printf(s, "\nprint fmt: \"0x%%lx\", REC->ret\n");
 271 }
 272
 273 int syscall_enter_define_fields(struct ftrace_event_call *call)
 274 {
 275         struct syscall_trace_enter trace;
 276         struct syscall_metadata *meta = call->data;
 277         int ret;
 278         int i;
 279         int offset = offsetof(typeof(trace), args);
 280
 281         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 282         if (ret)
 283                 return ret;
 284
 285         for (i = 0; i < meta->nb_args; i++) {
 286                 ret = trace_define_field(call, meta->types[i],
 287                                          meta->args[i], offset,
 288                                          sizeof(unsigned long), 0,
 289                                          FILTER_OTHER);
 290                 offset += sizeof(unsigned long);
 291         }
 292
 293         return ret;
 294 }
 295
 296 int syscall_exit_define_fields(struct ftrace_event_call *call)
 297 {
 298         struct syscall_trace_exit trace;
 299         int ret;
 300
 301         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 302         if (ret)
 303                 return ret;
 304
 305         ret = trace_define_field(call, SYSCALL_FIELD(long, ret),
 306                                  FILTER_OTHER);
 307
 308         return ret;
 309 }
 310
 311 void ftrace_syscall_enter(struct pt_regs *regs, long id)
 312 {
 313         struct syscall_trace_enter *entry;
 314         struct syscall_metadata *sys_data;
 315         struct ring_buffer_event *event;
 316         struct ring_buffer *buffer;
 317         int size;
 318         int syscall_nr;
 319
 320         syscall_nr = syscall_get_nr(current, regs);
 321         if (syscall_nr < 0)
 322                 return;
 323         if (!test_bit(syscall_nr, enabled_enter_syscalls))
 324                 return;
 325
 326         sys_data = syscall_nr_to_meta(syscall_nr);
 327         if (!sys_data)
 328                 return;
 329
 330         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 331
 332         event = trace_current_buffer_lock_reserve(&buffer,
 333                         sys_data->enter_event->id, size, 0, 0);
 334         if (!event)
 335                 return;
 336
 337         entry = ring_buffer_event_data(event);
 338         entry->nr = syscall_nr;
 339         syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
 340
 341         if (!filter_current_check_discard(buffer, sys_data->enter_event,
 342                                           entry, event))
 343                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 344 }
 345
 346 void ftrace_syscall_exit(struct pt_regs *regs, long ret)
 347 {
 348         struct syscall_trace_exit *entry;
 349         struct syscall_metadata *sys_data;
 350         struct ring_buffer_event *event;
 351         struct ring_buffer *buffer;
 352         int syscall_nr;
 353
 354         syscall_nr = syscall_get_nr(current, regs);
 355         if (syscall_nr < 0)
 356                 return;
 357         if (!test_bit(syscall_nr, enabled_exit_syscalls))
 358                 return;
 359
 360         sys_data = syscall_nr_to_meta(syscall_nr);
 361         if (!sys_data)
 362                 return;
 363
 364         event = trace_current_buffer_lock_reserve(&buffer,
 365                         sys_data->exit_event->id, sizeof(*entry), 0, 0);
 366         if (!event)
 367                 return;
 368
 369         entry = ring_buffer_event_data(event);
 370         entry->nr = syscall_nr;
 371         entry->ret = syscall_get_return_value(current, regs);
 372
 373         if (!filter_current_check_discard(buffer, sys_data->exit_event,
 374                                           entry, event))
 375                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 376 }
 377
 378 int reg_event_syscall_enter(struct ftrace_event_call *call)
 379 {
 380         int ret = 0;
 381         int num;
 382
 383         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 384         if (num < 0 || num >= NR_syscalls)
 385                 return -ENOSYS;
 386         mutex_lock(&syscall_trace_lock);
 387         if (!sys_refcount_enter)
 388                 ret = register_trace_sys_enter(ftrace_syscall_enter);
 389         if (!ret) {
 390                 set_bit(num, enabled_enter_syscalls);
 391                 sys_refcount_enter++;
 392         }
 393         mutex_unlock(&syscall_trace_lock);
 394         return ret;
 395 }
 396
 397 void unreg_event_syscall_enter(struct ftrace_event_call *call)
 398 {
 399         int num;
 400
 401         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 402         if (num < 0 || num >= NR_syscalls)
 403                 return;
 404         mutex_lock(&syscall_trace_lock);
 405         sys_refcount_enter--;
 406         clear_bit(num, enabled_enter_syscalls);
 407         if (!sys_refcount_enter)
 408                 unregister_trace_sys_enter(ftrace_syscall_enter);
 409         mutex_unlock(&syscall_trace_lock);
 410 }
 411
 412 int reg_event_syscall_exit(struct ftrace_event_call *call)
 413 {
 414         int ret = 0;
 415         int num;
 416
 417         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 418         if (num < 0 || num >= NR_syscalls)
 419                 return -ENOSYS;
 420         mutex_lock(&syscall_trace_lock);
 421         if (!sys_refcount_exit)
 422                 ret = register_trace_sys_exit(ftrace_syscall_exit);
 423         if (!ret) {
 424                 set_bit(num, enabled_exit_syscalls);
 425                 sys_refcount_exit++;
 426         }
 427         mutex_unlock(&syscall_trace_lock);
 428         return ret;
 429 }
 430
 431 void unreg_event_syscall_exit(struct ftrace_event_call *call)
 432 {
 433         int num;
 434
 435         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 436         if (num < 0 || num >= NR_syscalls)
 437                 return;
 438         mutex_lock(&syscall_trace_lock);
 439         sys_refcount_exit--;
 440         clear_bit(num, enabled_exit_syscalls);
 441         if (!sys_refcount_exit)
 442                 unregister_trace_sys_exit(ftrace_syscall_exit);
 443         mutex_unlock(&syscall_trace_lock);
 444 }
 445
 446 int init_syscall_trace(struct ftrace_event_call *call)
 447 {
 448         int id;
 449
 450         if (set_syscall_print_fmt(call) < 0)
 451                 return -ENOMEM;
 452
 453         id = trace_event_raw_init(call);
 454
 455         if (id < 0) {
 456                 free_syscall_print_fmt(call);
 457                 return id;
 458         }
 459
 460         return id;
 461 }
 462
 463 int __init init_ftrace_syscalls(void)
 464 {
 465         struct syscall_metadata *meta;
 466         unsigned long addr;
 467         int i;
 468
 469         syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
 470                                         NR_syscalls, GFP_KERNEL);
 471         if (!syscalls_metadata) {
 472                 WARN_ON(1);
 473                 return -ENOMEM;
 474         }
 475
 476         for (i = 0; i < NR_syscalls; i++) {
 477                 addr = arch_syscall_addr(i);
 478                 meta = find_syscall_meta(addr);
 479                 if (!meta)
 480                         continue;
 481
 482                 meta->syscall_nr = i;
 483                 syscalls_metadata[i] = meta;
 484         }
 485
 486         return 0;
 487 }
 488 core_initcall(init_ftrace_syscalls);
 489
 490 #ifdef CONFIG_EVENT_PROFILE
 491
 492 static DECLARE_BITMAP(enabled_prof_enter_syscalls, NR_syscalls);
 493 static DECLARE_BITMAP(enabled_prof_exit_syscalls, NR_syscalls);
 494 static int sys_prof_refcount_enter;
 495 static int sys_prof_refcount_exit;
 496
 497 static void prof_syscall_enter(struct pt_regs *regs, long id)
 498 {
 499         struct syscall_metadata *sys_data;
 500         struct syscall_trace_enter *rec;
 501         unsigned long flags;
 502         char *trace_buf;
 503         char *raw_data;
 504         int syscall_nr;
 505         int rctx;
 506         int size;
 507         int cpu;
 508
 509         syscall_nr = syscall_get_nr(current, regs);
 510         if (!test_bit(syscall_nr, enabled_prof_enter_syscalls))
 511                 return;
 512
 513         sys_data = syscall_nr_to_meta(syscall_nr);
 514         if (!sys_data)
 515                 return;
 516
 517         /* get the size after alignment with the u32 buffer size field */
 518         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 519         size = ALIGN(size + sizeof(u32), sizeof(u64));
 520         size -= sizeof(u32);
 521
 522         if (WARN_ONCE(size > FTRACE_MAX_PROFILE_SIZE,
 523                       "profile buffer not large enough"))
 524                 return;
 525
 526         /* Protect the per cpu buffer, begin the rcu read side */
 527         local_irq_save(flags);
 528
 529         rctx = perf_swevent_get_recursion_context();
 530         if (rctx < 0)
 531                 goto end_recursion;
 532
 533         cpu = smp_processor_id();
 534
 535         trace_buf = rcu_dereference(perf_trace_buf);
 536
 537         if (!trace_buf)
 538                 goto end;
 539
 540         raw_data = per_cpu_ptr(trace_buf, cpu);
 541
 542         /* zero the dead bytes from align to not leak stack to user */
 543         *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
 544
 545         rec = (struct syscall_trace_enter *) raw_data;
 546         tracing_generic_entry_update(&rec->ent, 0, 0);
 547         rec->ent.type = sys_data->enter_event->id;
 548         rec->nr = syscall_nr;
 549         syscall_get_arguments(current, regs, 0, sys_data->nb_args,
 550                                (unsigned long *)&rec->args);
 551         perf_tp_event(sys_data->enter_event->id, 0, 1, rec, size);
 552
 553 end:
 554         perf_swevent_put_recursion_context(rctx);
 555 end_recursion:
 556         local_irq_restore(flags);
 557 }
 558
 559 int prof_sysenter_enable(struct ftrace_event_call *call)
 560 {
 561         int ret = 0;
 562         int num;
 563
 564         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 565
 566         mutex_lock(&syscall_trace_lock);
 567         if (!sys_prof_refcount_enter)
 568                 ret = register_trace_sys_enter(prof_syscall_enter);
 569         if (ret) {
 570                 pr_info("event trace: Could not activate"
 571                                 "syscall entry trace point");
 572         } else {
 573                 set_bit(num, enabled_prof_enter_syscalls);
 574                 sys_prof_refcount_enter++;
 575         }
 576         mutex_unlock(&syscall_trace_lock);
 577         return ret;
 578 }
 579
 580 void prof_sysenter_disable(struct ftrace_event_call *call)
 581 {
 582         int num;
 583
 584         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 585
 586         mutex_lock(&syscall_trace_lock);
 587         sys_prof_refcount_enter--;
 588         clear_bit(num, enabled_prof_enter_syscalls);
 589         if (!sys_prof_refcount_enter)
 590                 unregister_trace_sys_enter(prof_syscall_enter);
 591         mutex_unlock(&syscall_trace_lock);
 592 }
 593
 594 static void prof_syscall_exit(struct pt_regs *regs, long ret)
 595 {
 596         struct syscall_metadata *sys_data;
 597         struct syscall_trace_exit *rec;
 598         unsigned long flags;
 599         int syscall_nr;
 600         char *trace_buf;
 601         char *raw_data;
 602         int rctx;
 603         int size;
 604         int cpu;
 605
 606         syscall_nr = syscall_get_nr(current, regs);
 607         if (!test_bit(syscall_nr, enabled_prof_exit_syscalls))
 608                 return;
 609
 610         sys_data = syscall_nr_to_meta(syscall_nr);
 611         if (!sys_data)
 612                 return;
 613
 614         /* We can probably do that at build time */
 615         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 616         size -= sizeof(u32);
 617
 618         /*
 619          * Impossible, but be paranoid with the future
 620          * How to put this check outside runtime?
 621          */
 622         if (WARN_ONCE(size > FTRACE_MAX_PROFILE_SIZE,
 623                 "exit event has grown above profile buffer size"))
 624                 return;
 625
 626         /* Protect the per cpu buffer, begin the rcu read side */
 627         local_irq_save(flags);
 628
 629         rctx = perf_swevent_get_recursion_context();
 630         if (rctx < 0)
 631                 goto end_recursion;
 632
 633         cpu = smp_processor_id();
 634
 635         trace_buf = rcu_dereference(perf_trace_buf);
 636
 637         if (!trace_buf)
 638                 goto end;
 639
 640         raw_data = per_cpu_ptr(trace_buf, cpu);
 641
 642         /* zero the dead bytes from align to not leak stack to user */
 643         *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL;
 644
 645         rec = (struct syscall_trace_exit *)raw_data;
 646
 647         tracing_generic_entry_update(&rec->ent, 0, 0);
 648         rec->ent.type = sys_data->exit_event->id;
 649         rec->nr = syscall_nr;
 650         rec->ret = syscall_get_return_value(current, regs);
 651
 652         perf_tp_event(sys_data->exit_event->id, 0, 1, rec, size);
 653
 654 end:
 655         perf_swevent_put_recursion_context(rctx);
 656 end_recursion:
 657         local_irq_restore(flags);
 658 }
 659
 660 int prof_sysexit_enable(struct ftrace_event_call *call)
 661 {
 662         int ret = 0;
 663         int num;
 664
 665         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 666
 667         mutex_lock(&syscall_trace_lock);
 668         if (!sys_prof_refcount_exit)
 669                 ret = register_trace_sys_exit(prof_syscall_exit);
 670         if (ret) {
 671                 pr_info("event trace: Could not activate"
 672                                 "syscall entry trace point");
 673         } else {
 674                 set_bit(num, enabled_prof_exit_syscalls);
 675                 sys_prof_refcount_exit++;
 676         }
 677         mutex_unlock(&syscall_trace_lock);
 678         return ret;
 679 }
 680
 681 void prof_sysexit_disable(struct ftrace_event_call *call)
 682 {
 683         int num;
 684
 685         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 686
 687         mutex_lock(&syscall_trace_lock);
 688         sys_prof_refcount_exit--;
 689         clear_bit(num, enabled_prof_exit_syscalls);
 690         if (!sys_prof_refcount_exit)
 691                 unregister_trace_sys_exit(prof_syscall_exit);
 692         mutex_unlock(&syscall_trace_lock);
 693 }
 694
 695 #endif
 696
 697