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 ftrace_event_call *event,
  17                                  enum trace_reg type, void *data);
  18 static int syscall_exit_register(struct ftrace_event_call *event,
  19                                  enum trace_reg type, void *data);
  20
  21 static struct list_head *
  22 syscall_get_enter_fields(struct ftrace_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_seq *s = &iter->seq;
 114         struct trace_entry *ent = iter->ent;
 115         struct syscall_trace_enter *trace;
 116         struct syscall_metadata *entry;
 117         int i, ret, syscall;
 118
 119         trace = (typeof(trace))ent;
 120         syscall = trace->nr;
 121         entry = syscall_nr_to_meta(syscall);
 122
 123         if (!entry)
 124                 goto end;
 125
 126         if (entry->enter_event->event.type != ent->type) {
 127                 WARN_ON_ONCE(1);
 128                 goto end;
 129         }
 130
 131         ret = trace_seq_printf(s, "%s(", entry->name);
 132         if (!ret)
 133                 return TRACE_TYPE_PARTIAL_LINE;
 134
 135         for (i = 0; i < entry->nb_args; i++) {
 136                 /* parameter types */
 137                 if (trace_flags & TRACE_ITER_VERBOSE) {
 138                         ret = trace_seq_printf(s, "%s ", entry->types[i]);
 139                         if (!ret)
 140                                 return TRACE_TYPE_PARTIAL_LINE;
 141                 }
 142                 /* parameter values */
 143                 ret = trace_seq_printf(s, "%s: %lx%s", entry->args[i],
 144                                        trace->args[i],
 145                                        i == entry->nb_args - 1 ? "" : ", ");
 146                 if (!ret)
 147                         return TRACE_TYPE_PARTIAL_LINE;
 148         }
 149
 150         ret = trace_seq_putc(s, ')');
 151         if (!ret)
 152                 return TRACE_TYPE_PARTIAL_LINE;
 153
 154 end:
 155         ret =  trace_seq_putc(s, '\n');
 156         if (!ret)
 157                 return TRACE_TYPE_PARTIAL_LINE;
 158
 159         return TRACE_TYPE_HANDLED;
 160 }
 161
 162 static enum print_line_t
 163 print_syscall_exit(struct trace_iterator *iter, int flags,
 164                    struct trace_event *event)
 165 {
 166         struct trace_seq *s = &iter->seq;
 167         struct trace_entry *ent = iter->ent;
 168         struct syscall_trace_exit *trace;
 169         int syscall;
 170         struct syscall_metadata *entry;
 171         int ret;
 172
 173         trace = (typeof(trace))ent;
 174         syscall = trace->nr;
 175         entry = syscall_nr_to_meta(syscall);
 176
 177         if (!entry) {
 178                 trace_seq_printf(s, "\n");
 179                 return TRACE_TYPE_HANDLED;
 180         }
 181
 182         if (entry->exit_event->event.type != ent->type) {
 183                 WARN_ON_ONCE(1);
 184                 return TRACE_TYPE_UNHANDLED;
 185         }
 186
 187         ret = trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
 188                                 trace->ret);
 189         if (!ret)
 190                 return TRACE_TYPE_PARTIAL_LINE;
 191
 192         return TRACE_TYPE_HANDLED;
 193 }
 194
 195 extern char *__bad_type_size(void);
 196
 197 #define SYSCALL_FIELD(type, name)                                       \
 198         sizeof(type) != sizeof(trace.name) ?                            \
 199                 __bad_type_size() :                                     \
 200                 #type, #name, offsetof(typeof(trace), name),            \
 201                 sizeof(trace.name), is_signed_type(type)
 202
 203 static
 204 int  __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 205 {
 206         int i;
 207         int pos = 0;
 208
 209         /* When len=0, we just calculate the needed length */
 210 #define LEN_OR_ZERO (len ? len - pos : 0)
 211
 212         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 213         for (i = 0; i < entry->nb_args; i++) {
 214                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 215                                 entry->args[i], sizeof(unsigned long),
 216                                 i == entry->nb_args - 1 ? "" : ", ");
 217         }
 218         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 219
 220         for (i = 0; i < entry->nb_args; i++) {
 221                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 222                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 223         }
 224
 225 #undef LEN_OR_ZERO
 226
 227         /* return the length of print_fmt */
 228         return pos;
 229 }
 230
 231 static int set_syscall_print_fmt(struct ftrace_event_call *call)
 232 {
 233         char *print_fmt;
 234         int len;
 235         struct syscall_metadata *entry = call->data;
 236
 237         if (entry->enter_event != call) {
 238                 call->print_fmt = "\"0x%lx\", REC->ret";
 239                 return 0;
 240         }
 241
 242         /* First: called with 0 length to calculate the needed length */
 243         len = __set_enter_print_fmt(entry, NULL, 0);
 244
 245         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 246         if (!print_fmt)
 247                 return -ENOMEM;
 248
 249         /* Second: actually write the @print_fmt */
 250         __set_enter_print_fmt(entry, print_fmt, len + 1);
 251         call->print_fmt = print_fmt;
 252
 253         return 0;
 254 }
 255
 256 static void free_syscall_print_fmt(struct ftrace_event_call *call)
 257 {
 258         struct syscall_metadata *entry = call->data;
 259
 260         if (entry->enter_event == call)
 261                 kfree(call->print_fmt);
 262 }
 263
 264 static int __init syscall_enter_define_fields(struct ftrace_event_call *call)
 265 {
 266         struct syscall_trace_enter trace;
 267         struct syscall_metadata *meta = call->data;
 268         int ret;
 269         int i;
 270         int offset = offsetof(typeof(trace), args);
 271
 272         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 273         if (ret)
 274                 return ret;
 275
 276         for (i = 0; i < meta->nb_args; i++) {
 277                 ret = trace_define_field(call, meta->types[i],
 278                                          meta->args[i], offset,
 279                                          sizeof(unsigned long), 0,
 280                                          FILTER_OTHER);
 281                 offset += sizeof(unsigned long);
 282         }
 283
 284         return ret;
 285 }
 286
 287 static int __init syscall_exit_define_fields(struct ftrace_event_call *call)
 288 {
 289         struct syscall_trace_exit trace;
 290         int ret;
 291
 292         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 293         if (ret)
 294                 return ret;
 295
 296         ret = trace_define_field(call, SYSCALL_FIELD(long, ret),
 297                                  FILTER_OTHER);
 298
 299         return ret;
 300 }
 301
 302 static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 303 {
 304         struct trace_array *tr = data;
 305         struct syscall_trace_enter *entry;
 306         struct syscall_metadata *sys_data;
 307         struct ring_buffer_event *event;
 308         struct ring_buffer *buffer;
 309         int syscall_nr;
 310         int size;
 311
 312         syscall_nr = trace_get_syscall_nr(current, regs);
 313         if (syscall_nr < 0)
 314                 return;
 315         if (!test_bit(syscall_nr, tr->enabled_enter_syscalls))
 316                 return;
 317
 318         sys_data = syscall_nr_to_meta(syscall_nr);
 319         if (!sys_data)
 320                 return;
 321
 322         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 323
 324         buffer = tr->trace_buffer.buffer;
 325         event = trace_buffer_lock_reserve(buffer,
 326                         sys_data->enter_event->event.type, size, 0, 0);
 327         if (!event)
 328                 return;
 329
 330         entry = ring_buffer_event_data(event);
 331         entry->nr = syscall_nr;
 332         syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
 333
 334         if (!filter_current_check_discard(buffer, sys_data->enter_event,
 335                                           entry, event))
 336                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 337 }
 338
 339 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
 340 {
 341         struct trace_array *tr = data;
 342         struct syscall_trace_exit *entry;
 343         struct syscall_metadata *sys_data;
 344         struct ring_buffer_event *event;
 345         struct ring_buffer *buffer;
 346         int syscall_nr;
 347
 348         syscall_nr = trace_get_syscall_nr(current, regs);
 349         if (syscall_nr < 0)
 350                 return;
 351         if (!test_bit(syscall_nr, tr->enabled_exit_syscalls))
 352                 return;
 353
 354         sys_data = syscall_nr_to_meta(syscall_nr);
 355         if (!sys_data)
 356                 return;
 357
 358         buffer = tr->trace_buffer.buffer;
 359         event = trace_buffer_lock_reserve(buffer,
 360                         sys_data->exit_event->event.type, sizeof(*entry), 0, 0);
 361         if (!event)
 362                 return;
 363
 364         entry = ring_buffer_event_data(event);
 365         entry->nr = syscall_nr;
 366         entry->ret = syscall_get_return_value(current, regs);
 367
 368         if (!filter_current_check_discard(buffer, sys_data->exit_event,
 369                                           entry, event))
 370                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 371 }
 372
 373 static int reg_event_syscall_enter(struct ftrace_event_file *file,
 374                                    struct ftrace_event_call *call)
 375 {
 376         struct trace_array *tr = file->tr;
 377         int ret = 0;
 378         int num;
 379
 380         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 381         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 382                 return -ENOSYS;
 383         mutex_lock(&syscall_trace_lock);
 384         if (!tr->sys_refcount_enter)
 385                 ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
 386         if (!ret) {
 387                 set_bit(num, tr->enabled_enter_syscalls);
 388                 tr->sys_refcount_enter++;
 389         }
 390         mutex_unlock(&syscall_trace_lock);
 391         return ret;
 392 }
 393
 394 static void unreg_event_syscall_enter(struct ftrace_event_file *file,
 395                                       struct ftrace_event_call *call)
 396 {
 397         struct trace_array *tr = file->tr;
 398         int num;
 399
 400         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 401         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 402                 return;
 403         mutex_lock(&syscall_trace_lock);
 404         tr->sys_refcount_enter--;
 405         clear_bit(num, tr->enabled_enter_syscalls);
 406         if (!tr->sys_refcount_enter)
 407                 unregister_trace_sys_enter(ftrace_syscall_enter, tr);
 408         mutex_unlock(&syscall_trace_lock);
 409 }
 410
 411 static int reg_event_syscall_exit(struct ftrace_event_file *file,
 412                                   struct ftrace_event_call *call)
 413 {
 414         struct trace_array *tr = file->tr;
 415         int ret = 0;
 416         int num;
 417
 418         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 419         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 420                 return -ENOSYS;
 421         mutex_lock(&syscall_trace_lock);
 422         if (!tr->sys_refcount_exit)
 423                 ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
 424         if (!ret) {
 425                 set_bit(num, tr->enabled_exit_syscalls);
 426                 tr->sys_refcount_exit++;
 427         }
 428         mutex_unlock(&syscall_trace_lock);
 429         return ret;
 430 }
 431
 432 static void unreg_event_syscall_exit(struct ftrace_event_file *file,
 433                                      struct ftrace_event_call *call)
 434 {
 435         struct trace_array *tr = file->tr;
 436         int num;
 437
 438         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 439         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 440                 return;
 441         mutex_lock(&syscall_trace_lock);
 442         tr->sys_refcount_exit--;
 443         clear_bit(num, tr->enabled_exit_syscalls);
 444         if (!tr->sys_refcount_exit)
 445                 unregister_trace_sys_exit(ftrace_syscall_exit, tr);
 446         mutex_unlock(&syscall_trace_lock);
 447 }
 448
 449 static int init_syscall_trace(struct ftrace_event_call *call)
 450 {
 451         int id;
 452         int num;
 453
 454         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 455         if (num < 0 || num >= NR_syscalls) {
 456                 pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
 457                                 ((struct syscall_metadata *)call->data)->name);
 458                 return -ENOSYS;
 459         }
 460
 461         if (set_syscall_print_fmt(call) < 0)
 462                 return -ENOMEM;
 463
 464         id = trace_event_raw_init(call);
 465
 466         if (id < 0) {
 467                 free_syscall_print_fmt(call);
 468                 return id;
 469         }
 470
 471         return id;
 472 }
 473
 474 struct trace_event_functions enter_syscall_print_funcs = {
 475         .trace          = print_syscall_enter,
 476 };
 477
 478 struct trace_event_functions exit_syscall_print_funcs = {
 479         .trace          = print_syscall_exit,
 480 };
 481
 482 struct ftrace_event_class __refdata event_class_syscall_enter = {
 483         .system         = "syscalls",
 484         .reg            = syscall_enter_register,
 485         .define_fields  = syscall_enter_define_fields,
 486         .get_fields     = syscall_get_enter_fields,
 487         .raw_init       = init_syscall_trace,
 488 };
 489
 490 struct ftrace_event_class __refdata event_class_syscall_exit = {
 491         .system         = "syscalls",
 492         .reg            = syscall_exit_register,
 493         .define_fields  = syscall_exit_define_fields,
 494         .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
 495         .raw_init       = init_syscall_trace,
 496 };
 497
 498 unsigned long __init __weak arch_syscall_addr(int nr)
 499 {
 500         return (unsigned long)sys_call_table[nr];
 501 }
 502
 503 static int __init init_ftrace_syscalls(void)
 504 {
 505         struct syscall_metadata *meta;
 506         unsigned long addr;
 507         int i;
 508
 509         syscalls_metadata = kcalloc(NR_syscalls, sizeof(*syscalls_metadata),
 510                                     GFP_KERNEL);
 511         if (!syscalls_metadata) {
 512                 WARN_ON(1);
 513                 return -ENOMEM;
 514         }
 515
 516         for (i = 0; i < NR_syscalls; i++) {
 517                 addr = arch_syscall_addr(i);
 518                 meta = find_syscall_meta(addr);
 519                 if (!meta)
 520                         continue;
 521
 522                 meta->syscall_nr = i;
 523                 syscalls_metadata[i] = meta;
 524         }
 525
 526         return 0;
 527 }
 528 early_initcall(init_ftrace_syscalls);
 529
 530 #ifdef CONFIG_PERF_EVENTS
 531
 532 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 533 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 534 static int sys_perf_refcount_enter;
 535 static int sys_perf_refcount_exit;
 536
 537 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 538 {
 539         struct syscall_metadata *sys_data;
 540         struct syscall_trace_enter *rec;
 541         struct hlist_head *head;
 542         int syscall_nr;
 543         int rctx;
 544         int size;
 545
 546         syscall_nr = trace_get_syscall_nr(current, regs);
 547         if (syscall_nr < 0)
 548                 return;
 549         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 550                 return;
 551
 552         sys_data = syscall_nr_to_meta(syscall_nr);
 553         if (!sys_data)
 554                 return;
 555
 556         /* get the size after alignment with the u32 buffer size field */
 557         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 558         size = ALIGN(size + sizeof(u32), sizeof(u64));
 559         size -= sizeof(u32);
 560
 561         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
 562                       "perf buffer not large enough"))
 563                 return;
 564
 565         rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
 566                                 sys_data->enter_event->event.type, regs, &rctx);
 567         if (!rec)
 568                 return;
 569
 570         rec->nr = syscall_nr;
 571         syscall_get_arguments(current, regs, 0, sys_data->nb_args,
 572                                (unsigned long *)&rec->args);
 573
 574         head = this_cpu_ptr(sys_data->enter_event->perf_events);
 575         perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
 576 }
 577
 578 static int perf_sysenter_enable(struct ftrace_event_call *call)
 579 {
 580         int ret = 0;
 581         int num;
 582
 583         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 584
 585         mutex_lock(&syscall_trace_lock);
 586         if (!sys_perf_refcount_enter)
 587                 ret = register_trace_sys_enter(perf_syscall_enter, NULL);
 588         if (ret) {
 589                 pr_info("event trace: Could not activate"
 590                                 "syscall entry trace point");
 591         } else {
 592                 set_bit(num, enabled_perf_enter_syscalls);
 593                 sys_perf_refcount_enter++;
 594         }
 595         mutex_unlock(&syscall_trace_lock);
 596         return ret;
 597 }
 598
 599 static void perf_sysenter_disable(struct ftrace_event_call *call)
 600 {
 601         int num;
 602
 603         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 604
 605         mutex_lock(&syscall_trace_lock);
 606         sys_perf_refcount_enter--;
 607         clear_bit(num, enabled_perf_enter_syscalls);
 608         if (!sys_perf_refcount_enter)
 609                 unregister_trace_sys_enter(perf_syscall_enter, NULL);
 610         mutex_unlock(&syscall_trace_lock);
 611 }
 612
 613 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 614 {
 615         struct syscall_metadata *sys_data;
 616         struct syscall_trace_exit *rec;
 617         struct hlist_head *head;
 618         int syscall_nr;
 619         int rctx;
 620         int size;
 621
 622         syscall_nr = trace_get_syscall_nr(current, regs);
 623         if (syscall_nr < 0)
 624                 return;
 625         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 626                 return;
 627
 628         sys_data = syscall_nr_to_meta(syscall_nr);
 629         if (!sys_data)
 630                 return;
 631
 632         /* We can probably do that at build time */
 633         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 634         size -= sizeof(u32);
 635
 636         /*
 637          * Impossible, but be paranoid with the future
 638          * How to put this check outside runtime?
 639          */
 640         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
 641                 "exit event has grown above perf buffer size"))
 642                 return;
 643
 644         rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
 645                                 sys_data->exit_event->event.type, regs, &rctx);
 646         if (!rec)
 647                 return;
 648
 649         rec->nr = syscall_nr;
 650         rec->ret = syscall_get_return_value(current, regs);
 651
 652         head = this_cpu_ptr(sys_data->exit_event->perf_events);
 653         perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
 654 }
 655
 656 static int perf_sysexit_enable(struct ftrace_event_call *call)
 657 {
 658         int ret = 0;
 659         int num;
 660
 661         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 662
 663         mutex_lock(&syscall_trace_lock);
 664         if (!sys_perf_refcount_exit)
 665                 ret = register_trace_sys_exit(perf_syscall_exit, NULL);
 666         if (ret) {
 667                 pr_info("event trace: Could not activate"
 668                                 "syscall exit trace point");
 669         } else {
 670                 set_bit(num, enabled_perf_exit_syscalls);
 671                 sys_perf_refcount_exit++;
 672         }
 673         mutex_unlock(&syscall_trace_lock);
 674         return ret;
 675 }
 676
 677 static void perf_sysexit_disable(struct ftrace_event_call *call)
 678 {
 679         int num;
 680
 681         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 682
 683         mutex_lock(&syscall_trace_lock);
 684         sys_perf_refcount_exit--;
 685         clear_bit(num, enabled_perf_exit_syscalls);
 686         if (!sys_perf_refcount_exit)
 687                 unregister_trace_sys_exit(perf_syscall_exit, NULL);
 688         mutex_unlock(&syscall_trace_lock);
 689 }
 690
 691 #endif /* CONFIG_PERF_EVENTS */
 692
 693 static int syscall_enter_register(struct ftrace_event_call *event,
 694                                  enum trace_reg type, void *data)
 695 {
 696         struct ftrace_event_file *file = data;
 697
 698         switch (type) {
 699         case TRACE_REG_REGISTER:
 700                 return reg_event_syscall_enter(file, event);
 701         case TRACE_REG_UNREGISTER:
 702                 unreg_event_syscall_enter(file, event);
 703                 return 0;
 704
 705 #ifdef CONFIG_PERF_EVENTS
 706         case TRACE_REG_PERF_REGISTER:
 707                 return perf_sysenter_enable(event);
 708         case TRACE_REG_PERF_UNREGISTER:
 709                 perf_sysenter_disable(event);
 710                 return 0;
 711         case TRACE_REG_PERF_OPEN:
 712         case TRACE_REG_PERF_CLOSE:
 713         case TRACE_REG_PERF_ADD:
 714         case TRACE_REG_PERF_DEL:
 715                 return 0;
 716 #endif
 717         }
 718         return 0;
 719 }
 720
 721 static int syscall_exit_register(struct ftrace_event_call *event,
 722                                  enum trace_reg type, void *data)
 723 {
 724         struct ftrace_event_file *file = data;
 725
 726         switch (type) {
 727         case TRACE_REG_REGISTER:
 728                 return reg_event_syscall_exit(file, event);
 729         case TRACE_REG_UNREGISTER:
 730                 unreg_event_syscall_exit(file, event);
 731                 return 0;
 732
 733 #ifdef CONFIG_PERF_EVENTS
 734         case TRACE_REG_PERF_REGISTER:
 735                 return perf_sysexit_enable(event);
 736         case TRACE_REG_PERF_UNREGISTER:
 737                 perf_sysexit_disable(event);
 738                 return 0;
 739         case TRACE_REG_PERF_OPEN:
 740         case TRACE_REG_PERF_CLOSE:
 741         case TRACE_REG_PERF_ADD:
 742         case TRACE_REG_PERF_DEL:
 743                 return 0;
 744 #endif
 745         }
 746         return 0;
 747 }