kernel/trace/trace_syscalls.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <trace/syscall.h>
   3 #include <trace/events/syscalls.h>
   4 #include <linux/syscalls.h>
   5 #include <linux/slab.h>
   6 #include <linux/kernel.h>
   7 #include <linux/module.h>       /* for MODULE_NAME_LEN via KSYM_SYMBOL_LEN */
   8 #include <linux/ftrace.h>
   9 #include <linux/perf_event.h>
  10 #include <linux/xarray.h>
  11 #include <asm/syscall.h>
  12
  13 #include "trace_output.h"
  14 #include "trace.h"
  15
  16 static DEFINE_MUTEX(syscall_trace_lock);
  17
  18 static int syscall_enter_register(struct trace_event_call *event,
  19                                  enum trace_reg type, void *data);
  20 static int syscall_exit_register(struct trace_event_call *event,
  21                                  enum trace_reg type, void *data);
  22
  23 static struct list_head *
  24 syscall_get_enter_fields(struct trace_event_call *call)
  25 {
  26         struct syscall_metadata *entry = call->data;
  27
  28         return &entry->enter_fields;
  29 }
  30
  31 extern struct syscall_metadata *__start_syscalls_metadata[];
  32 extern struct syscall_metadata *__stop_syscalls_metadata[];
  33
  34 static DEFINE_XARRAY(syscalls_metadata_sparse);
  35 static struct syscall_metadata **syscalls_metadata;
  36
  37 #ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
  38 static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
  39 {
  40         /*
  41          * Only compare after the "sys" prefix. Archs that use
  42          * syscall wrappers may have syscalls symbols aliases prefixed
  43          * with ".SyS" or ".sys" instead of "sys", leading to an unwanted
  44          * mismatch.
  45          */
  46         return !strcmp(sym + 3, name + 3);
  47 }
  48 #endif
  49
  50 #ifdef ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
  51 /*
  52  * Some architectures that allow for 32bit applications
  53  * to run on a 64bit kernel, do not map the syscalls for
  54  * the 32bit tasks the same as they do for 64bit tasks.
  55  *
  56  *     *cough*x86*cough*
  57  *
  58  * In such a case, instead of reporting the wrong syscalls,
  59  * simply ignore them.
  60  *
  61  * For an arch to ignore the compat syscalls it needs to
  62  * define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS as well as
  63  * define the function arch_trace_is_compat_syscall() to let
  64  * the tracing system know that it should ignore it.
  65  */
  66 static int
  67 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
  68 {
  69         if (unlikely(arch_trace_is_compat_syscall(regs)))
  70                 return -1;
  71
  72         return syscall_get_nr(task, regs);
  73 }
  74 #else
  75 static inline int
  76 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
  77 {
  78         return syscall_get_nr(task, regs);
  79 }
  80 #endif /* ARCH_TRACE_IGNORE_COMPAT_SYSCALLS */
  81
  82 static __init struct syscall_metadata *
  83 find_syscall_meta(unsigned long syscall)
  84 {
  85         struct syscall_metadata **start;
  86         struct syscall_metadata **stop;
  87         char str[KSYM_SYMBOL_LEN];
  88
  89
  90         start = __start_syscalls_metadata;
  91         stop = __stop_syscalls_metadata;
  92         kallsyms_lookup(syscall, NULL, NULL, NULL, str);
  93
  94         if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
  95                 return NULL;
  96
  97         for ( ; start < stop; start++) {
  98                 if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
  99                         return *start;
 100         }
 101         return NULL;
 102 }
 103
 104 static struct syscall_metadata *syscall_nr_to_meta(int nr)
 105 {
 106         if (IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR))
 107                 return xa_load(&syscalls_metadata_sparse, (unsigned long)nr);
 108
 109         if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
 110                 return NULL;
 111
 112         return syscalls_metadata[nr];
 113 }
 114
 115 const char *get_syscall_name(int syscall)
 116 {
 117         struct syscall_metadata *entry;
 118
 119         entry = syscall_nr_to_meta(syscall);
 120         if (!entry)
 121                 return NULL;
 122
 123         return entry->name;
 124 }
 125
 126 static enum print_line_t
 127 print_syscall_enter(struct trace_iterator *iter, int flags,
 128                     struct trace_event *event)
 129 {
 130         struct trace_array *tr = iter->tr;
 131         struct trace_seq *s = &iter->seq;
 132         struct trace_entry *ent = iter->ent;
 133         struct syscall_trace_enter *trace;
 134         struct syscall_metadata *entry;
 135         int i, syscall;
 136
 137         trace = (typeof(trace))ent;
 138         syscall = trace->nr;
 139         entry = syscall_nr_to_meta(syscall);
 140
 141         if (!entry)
 142                 goto end;
 143
 144         if (entry->enter_event->event.type != ent->type) {
 145                 WARN_ON_ONCE(1);
 146                 goto end;
 147         }
 148
 149         trace_seq_printf(s, "%s(", entry->name);
 150
 151         for (i = 0; i < entry->nb_args; i++) {
 152
 153                 if (trace_seq_has_overflowed(s))
 154                         goto end;
 155
 156                 /* parameter types */
 157                 if (tr->trace_flags & TRACE_ITER_VERBOSE)
 158                         trace_seq_printf(s, "%s ", entry->types[i]);
 159
 160                 /* parameter values */
 161                 trace_seq_printf(s, "%s: %lx%s", entry->args[i],
 162                                  trace->args[i],
 163                                  i == entry->nb_args - 1 ? "" : ", ");
 164         }
 165
 166         trace_seq_putc(s, ')');
 167 end:
 168         trace_seq_putc(s, '\n');
 169
 170         return trace_handle_return(s);
 171 }
 172
 173 static enum print_line_t
 174 print_syscall_exit(struct trace_iterator *iter, int flags,
 175                    struct trace_event *event)
 176 {
 177         struct trace_seq *s = &iter->seq;
 178         struct trace_entry *ent = iter->ent;
 179         struct syscall_trace_exit *trace;
 180         int syscall;
 181         struct syscall_metadata *entry;
 182
 183         trace = (typeof(trace))ent;
 184         syscall = trace->nr;
 185         entry = syscall_nr_to_meta(syscall);
 186
 187         if (!entry) {
 188                 trace_seq_putc(s, '\n');
 189                 goto out;
 190         }
 191
 192         if (entry->exit_event->event.type != ent->type) {
 193                 WARN_ON_ONCE(1);
 194                 return TRACE_TYPE_UNHANDLED;
 195         }
 196
 197         trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
 198                                 trace->ret);
 199
 200  out:
 201         return trace_handle_return(s);
 202 }
 203
 204 extern char *__bad_type_size(void);
 205
 206 #define SYSCALL_FIELD(type, field, name)                                \
 207         sizeof(type) != sizeof(trace.field) ?                           \
 208                 __bad_type_size() :                                     \
 209                 #type, #name, offsetof(typeof(trace), field),           \
 210                 sizeof(trace.field), is_signed_type(type)
 211
 212 static int __init
 213 __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 214 {
 215         int i;
 216         int pos = 0;
 217
 218         /* When len=0, we just calculate the needed length */
 219 #define LEN_OR_ZERO (len ? len - pos : 0)
 220
 221         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 222         for (i = 0; i < entry->nb_args; i++) {
 223                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 224                                 entry->args[i], sizeof(unsigned long),
 225                                 i == entry->nb_args - 1 ? "" : ", ");
 226         }
 227         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 228
 229         for (i = 0; i < entry->nb_args; i++) {
 230                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 231                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 232         }
 233
 234 #undef LEN_OR_ZERO
 235
 236         /* return the length of print_fmt */
 237         return pos;
 238 }
 239
 240 static int __init set_syscall_print_fmt(struct trace_event_call *call)
 241 {
 242         char *print_fmt;
 243         int len;
 244         struct syscall_metadata *entry = call->data;
 245
 246         if (entry->enter_event != call) {
 247                 call->print_fmt = "\"0x%lx\", REC->ret";
 248                 return 0;
 249         }
 250
 251         /* First: called with 0 length to calculate the needed length */
 252         len = __set_enter_print_fmt(entry, NULL, 0);
 253
 254         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 255         if (!print_fmt)
 256                 return -ENOMEM;
 257
 258         /* Second: actually write the @print_fmt */
 259         __set_enter_print_fmt(entry, print_fmt, len + 1);
 260         call->print_fmt = print_fmt;
 261
 262         return 0;
 263 }
 264
 265 static void __init free_syscall_print_fmt(struct trace_event_call *call)
 266 {
 267         struct syscall_metadata *entry = call->data;
 268
 269         if (entry->enter_event == call)
 270                 kfree(call->print_fmt);
 271 }
 272
 273 static int __init syscall_enter_define_fields(struct trace_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, __syscall_nr),
 282                                  FILTER_OTHER);
 283         if (ret)
 284                 return ret;
 285
 286         for (i = 0; i < meta->nb_args; i++) {
 287                 ret = trace_define_field(call, meta->types[i],
 288                                          meta->args[i], offset,
 289                                          sizeof(unsigned long), 0,
 290                                          FILTER_OTHER);
 291                 offset += sizeof(unsigned long);
 292         }
 293
 294         return ret;
 295 }
 296
 297 static int __init syscall_exit_define_fields(struct trace_event_call *call)
 298 {
 299         struct syscall_trace_exit trace;
 300         int ret;
 301
 302         ret = trace_define_field(call, SYSCALL_FIELD(int, nr, __syscall_nr),
 303                                  FILTER_OTHER);
 304         if (ret)
 305                 return ret;
 306
 307         ret = trace_define_field(call, SYSCALL_FIELD(long, ret, ret),
 308                                  FILTER_OTHER);
 309
 310         return ret;
 311 }
 312
 313 static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 314 {
 315         struct trace_array *tr = data;
 316         struct trace_event_file *trace_file;
 317         struct syscall_trace_enter *entry;
 318         struct syscall_metadata *sys_data;
 319         struct ring_buffer_event *event;
 320         struct ring_buffer *buffer;
 321         unsigned long irq_flags;
 322         unsigned long args[6];
 323         int pc;
 324         int syscall_nr;
 325         int size;
 326
 327         syscall_nr = trace_get_syscall_nr(current, regs);
 328         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 329                 return;
 330
 331         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE) */
 332         trace_file = rcu_dereference_sched(tr->enter_syscall_files[syscall_nr]);
 333         if (!trace_file)
 334                 return;
 335
 336         if (trace_trigger_soft_disabled(trace_file))
 337                 return;
 338
 339         sys_data = syscall_nr_to_meta(syscall_nr);
 340         if (!sys_data)
 341                 return;
 342
 343         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 344
 345         local_save_flags(irq_flags);
 346         pc = preempt_count();
 347
 348         buffer = tr->trace_buffer.buffer;
 349         event = trace_buffer_lock_reserve(buffer,
 350                         sys_data->enter_event->event.type, size, irq_flags, pc);
 351         if (!event)
 352                 return;
 353
 354         entry = ring_buffer_event_data(event);
 355         entry->nr = syscall_nr;
 356         syscall_get_arguments(current, regs, args);
 357         memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
 358
 359         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 360                                     irq_flags, pc);
 361 }
 362
 363 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
 364 {
 365         struct trace_array *tr = data;
 366         struct trace_event_file *trace_file;
 367         struct syscall_trace_exit *entry;
 368         struct syscall_metadata *sys_data;
 369         struct ring_buffer_event *event;
 370         struct ring_buffer *buffer;
 371         unsigned long irq_flags;
 372         int pc;
 373         int syscall_nr;
 374
 375         syscall_nr = trace_get_syscall_nr(current, regs);
 376         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 377                 return;
 378
 379         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE()) */
 380         trace_file = rcu_dereference_sched(tr->exit_syscall_files[syscall_nr]);
 381         if (!trace_file)
 382                 return;
 383
 384         if (trace_trigger_soft_disabled(trace_file))
 385                 return;
 386
 387         sys_data = syscall_nr_to_meta(syscall_nr);
 388         if (!sys_data)
 389                 return;
 390
 391         local_save_flags(irq_flags);
 392         pc = preempt_count();
 393
 394         buffer = tr->trace_buffer.buffer;
 395         event = trace_buffer_lock_reserve(buffer,
 396                         sys_data->exit_event->event.type, sizeof(*entry),
 397                         irq_flags, pc);
 398         if (!event)
 399                 return;
 400
 401         entry = ring_buffer_event_data(event);
 402         entry->nr = syscall_nr;
 403         entry->ret = syscall_get_return_value(current, regs);
 404
 405         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 406                                     irq_flags, pc);
 407 }
 408
 409 static int reg_event_syscall_enter(struct trace_event_file *file,
 410                                    struct trace_event_call *call)
 411 {
 412         struct trace_array *tr = file->tr;
 413         int ret = 0;
 414         int num;
 415
 416         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 417         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 418                 return -ENOSYS;
 419         mutex_lock(&syscall_trace_lock);
 420         if (!tr->sys_refcount_enter)
 421                 ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
 422         if (!ret) {
 423                 rcu_assign_pointer(tr->enter_syscall_files[num], file);
 424                 tr->sys_refcount_enter++;
 425         }
 426         mutex_unlock(&syscall_trace_lock);
 427         return ret;
 428 }
 429
 430 static void unreg_event_syscall_enter(struct trace_event_file *file,
 431                                       struct trace_event_call *call)
 432 {
 433         struct trace_array *tr = file->tr;
 434         int num;
 435
 436         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 437         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 438                 return;
 439         mutex_lock(&syscall_trace_lock);
 440         tr->sys_refcount_enter--;
 441         RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
 442         if (!tr->sys_refcount_enter)
 443                 unregister_trace_sys_enter(ftrace_syscall_enter, tr);
 444         mutex_unlock(&syscall_trace_lock);
 445 }
 446
 447 static int reg_event_syscall_exit(struct trace_event_file *file,
 448                                   struct trace_event_call *call)
 449 {
 450         struct trace_array *tr = file->tr;
 451         int ret = 0;
 452         int num;
 453
 454         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 455         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 456                 return -ENOSYS;
 457         mutex_lock(&syscall_trace_lock);
 458         if (!tr->sys_refcount_exit)
 459                 ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
 460         if (!ret) {
 461                 rcu_assign_pointer(tr->exit_syscall_files[num], file);
 462                 tr->sys_refcount_exit++;
 463         }
 464         mutex_unlock(&syscall_trace_lock);
 465         return ret;
 466 }
 467
 468 static void unreg_event_syscall_exit(struct trace_event_file *file,
 469                                      struct trace_event_call *call)
 470 {
 471         struct trace_array *tr = file->tr;
 472         int num;
 473
 474         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 475         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 476                 return;
 477         mutex_lock(&syscall_trace_lock);
 478         tr->sys_refcount_exit--;
 479         RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
 480         if (!tr->sys_refcount_exit)
 481                 unregister_trace_sys_exit(ftrace_syscall_exit, tr);
 482         mutex_unlock(&syscall_trace_lock);
 483 }
 484
 485 static int __init init_syscall_trace(struct trace_event_call *call)
 486 {
 487         int id;
 488         int num;
 489
 490         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 491         if (num < 0 || num >= NR_syscalls) {
 492                 pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
 493                                 ((struct syscall_metadata *)call->data)->name);
 494                 return -ENOSYS;
 495         }
 496
 497         if (set_syscall_print_fmt(call) < 0)
 498                 return -ENOMEM;
 499
 500         id = trace_event_raw_init(call);
 501
 502         if (id < 0) {
 503                 free_syscall_print_fmt(call);
 504                 return id;
 505         }
 506
 507         return id;
 508 }
 509
 510 struct trace_event_functions enter_syscall_print_funcs = {
 511         .trace          = print_syscall_enter,
 512 };
 513
 514 struct trace_event_functions exit_syscall_print_funcs = {
 515         .trace          = print_syscall_exit,
 516 };
 517
 518 struct trace_event_class __refdata event_class_syscall_enter = {
 519         .system         = "syscalls",
 520         .reg            = syscall_enter_register,
 521         .define_fields  = syscall_enter_define_fields,
 522         .get_fields     = syscall_get_enter_fields,
 523         .raw_init       = init_syscall_trace,
 524 };
 525
 526 struct trace_event_class __refdata event_class_syscall_exit = {
 527         .system         = "syscalls",
 528         .reg            = syscall_exit_register,
 529         .define_fields  = syscall_exit_define_fields,
 530         .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
 531         .raw_init       = init_syscall_trace,
 532 };
 533
 534 unsigned long __init __weak arch_syscall_addr(int nr)
 535 {
 536         return (unsigned long)sys_call_table[nr];
 537 }
 538
 539 void __init init_ftrace_syscalls(void)
 540 {
 541         struct syscall_metadata *meta;
 542         unsigned long addr;
 543         int i;
 544         void *ret;
 545
 546         if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
 547                 syscalls_metadata = kcalloc(NR_syscalls,
 548                                         sizeof(*syscalls_metadata),
 549                                         GFP_KERNEL);
 550                 if (!syscalls_metadata) {
 551                         WARN_ON(1);
 552                         return;
 553                 }
 554         }
 555
 556         for (i = 0; i < NR_syscalls; i++) {
 557                 addr = arch_syscall_addr(i);
 558                 meta = find_syscall_meta(addr);
 559                 if (!meta)
 560                         continue;
 561
 562                 meta->syscall_nr = i;
 563
 564                 if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
 565                         syscalls_metadata[i] = meta;
 566                 } else {
 567                         ret = xa_store(&syscalls_metadata_sparse, i, meta,
 568                                         GFP_KERNEL);
 569                         WARN(xa_is_err(ret),
 570                                 "Syscall memory allocation failed\n");
 571                 }
 572
 573         }
 574 }
 575
 576 #ifdef CONFIG_PERF_EVENTS
 577
 578 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 579 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 580 static int sys_perf_refcount_enter;
 581 static int sys_perf_refcount_exit;
 582
 583 static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *regs,
 584                                struct syscall_metadata *sys_data,
 585                                struct syscall_trace_enter *rec)
 586 {
 587         struct syscall_tp_t {
 588                 unsigned long long regs;
 589                 unsigned long syscall_nr;
 590                 unsigned long args[SYSCALL_DEFINE_MAXARGS];
 591         } param;
 592         int i;
 593
 594         *(struct pt_regs **)&param = regs;
 595         param.syscall_nr = rec->nr;
 596         for (i = 0; i < sys_data->nb_args; i++)
 597                 param.args[i] = rec->args[i];
 598         return trace_call_bpf(call, &param);
 599 }
 600
 601 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 602 {
 603         struct syscall_metadata *sys_data;
 604         struct syscall_trace_enter *rec;
 605         struct hlist_head *head;
 606         unsigned long args[6];
 607         bool valid_prog_array;
 608         int syscall_nr;
 609         int rctx;
 610         int size;
 611
 612         syscall_nr = trace_get_syscall_nr(current, regs);
 613         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 614                 return;
 615         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 616                 return;
 617
 618         sys_data = syscall_nr_to_meta(syscall_nr);
 619         if (!sys_data)
 620                 return;
 621
 622         head = this_cpu_ptr(sys_data->enter_event->perf_events);
 623         valid_prog_array = bpf_prog_array_valid(sys_data->enter_event);
 624         if (!valid_prog_array && hlist_empty(head))
 625                 return;
 626
 627         /* get the size after alignment with the u32 buffer size field */
 628         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 629         size = ALIGN(size + sizeof(u32), sizeof(u64));
 630         size -= sizeof(u32);
 631
 632         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 633         if (!rec)
 634                 return;
 635
 636         rec->nr = syscall_nr;
 637         syscall_get_arguments(current, regs, args);
 638         memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
 639
 640         if ((valid_prog_array &&
 641              !perf_call_bpf_enter(sys_data->enter_event, regs, sys_data, rec)) ||
 642             hlist_empty(head)) {
 643                 perf_swevent_put_recursion_context(rctx);
 644                 return;
 645         }
 646
 647         perf_trace_buf_submit(rec, size, rctx,
 648                               sys_data->enter_event->event.type, 1, regs,
 649                               head, NULL);
 650 }
 651
 652 static int perf_sysenter_enable(struct trace_event_call *call)
 653 {
 654         int ret = 0;
 655         int num;
 656
 657         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 658
 659         mutex_lock(&syscall_trace_lock);
 660         if (!sys_perf_refcount_enter)
 661                 ret = register_trace_sys_enter(perf_syscall_enter, NULL);
 662         if (ret) {
 663                 pr_info("event trace: Could not activate syscall entry trace point");
 664         } else {
 665                 set_bit(num, enabled_perf_enter_syscalls);
 666                 sys_perf_refcount_enter++;
 667         }
 668         mutex_unlock(&syscall_trace_lock);
 669         return ret;
 670 }
 671
 672 static void perf_sysenter_disable(struct trace_event_call *call)
 673 {
 674         int num;
 675
 676         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 677
 678         mutex_lock(&syscall_trace_lock);
 679         sys_perf_refcount_enter--;
 680         clear_bit(num, enabled_perf_enter_syscalls);
 681         if (!sys_perf_refcount_enter)
 682                 unregister_trace_sys_enter(perf_syscall_enter, NULL);
 683         mutex_unlock(&syscall_trace_lock);
 684 }
 685
 686 static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *regs,
 687                               struct syscall_trace_exit *rec)
 688 {
 689         struct syscall_tp_t {
 690                 unsigned long long regs;
 691                 unsigned long syscall_nr;
 692                 unsigned long ret;
 693         } param;
 694
 695         *(struct pt_regs **)&param = regs;
 696         param.syscall_nr = rec->nr;
 697         param.ret = rec->ret;
 698         return trace_call_bpf(call, &param);
 699 }
 700
 701 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 702 {
 703         struct syscall_metadata *sys_data;
 704         struct syscall_trace_exit *rec;
 705         struct hlist_head *head;
 706         bool valid_prog_array;
 707         int syscall_nr;
 708         int rctx;
 709         int size;
 710
 711         syscall_nr = trace_get_syscall_nr(current, regs);
 712         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 713                 return;
 714         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 715                 return;
 716
 717         sys_data = syscall_nr_to_meta(syscall_nr);
 718         if (!sys_data)
 719                 return;
 720
 721         head = this_cpu_ptr(sys_data->exit_event->perf_events);
 722         valid_prog_array = bpf_prog_array_valid(sys_data->exit_event);
 723         if (!valid_prog_array && hlist_empty(head))
 724                 return;
 725
 726         /* We can probably do that at build time */
 727         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 728         size -= sizeof(u32);
 729
 730         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 731         if (!rec)
 732                 return;
 733
 734         rec->nr = syscall_nr;
 735         rec->ret = syscall_get_return_value(current, regs);
 736
 737         if ((valid_prog_array &&
 738              !perf_call_bpf_exit(sys_data->exit_event, regs, rec)) ||
 739             hlist_empty(head)) {
 740                 perf_swevent_put_recursion_context(rctx);
 741                 return;
 742         }
 743
 744         perf_trace_buf_submit(rec, size, rctx, sys_data->exit_event->event.type,
 745                               1, regs, head, NULL);
 746 }
 747
 748 static int perf_sysexit_enable(struct trace_event_call *call)
 749 {
 750         int ret = 0;
 751         int num;
 752
 753         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 754
 755         mutex_lock(&syscall_trace_lock);
 756         if (!sys_perf_refcount_exit)
 757                 ret = register_trace_sys_exit(perf_syscall_exit, NULL);
 758         if (ret) {
 759                 pr_info("event trace: Could not activate syscall exit trace point");
 760         } else {
 761                 set_bit(num, enabled_perf_exit_syscalls);
 762                 sys_perf_refcount_exit++;
 763         }
 764         mutex_unlock(&syscall_trace_lock);
 765         return ret;
 766 }
 767
 768 static void perf_sysexit_disable(struct trace_event_call *call)
 769 {
 770         int num;
 771
 772         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 773
 774         mutex_lock(&syscall_trace_lock);
 775         sys_perf_refcount_exit--;
 776         clear_bit(num, enabled_perf_exit_syscalls);
 777         if (!sys_perf_refcount_exit)
 778                 unregister_trace_sys_exit(perf_syscall_exit, NULL);
 779         mutex_unlock(&syscall_trace_lock);
 780 }
 781
 782 #endif /* CONFIG_PERF_EVENTS */
 783
 784 static int syscall_enter_register(struct trace_event_call *event,
 785                                  enum trace_reg type, void *data)
 786 {
 787         struct trace_event_file *file = data;
 788
 789         switch (type) {
 790         case TRACE_REG_REGISTER:
 791                 return reg_event_syscall_enter(file, event);
 792         case TRACE_REG_UNREGISTER:
 793                 unreg_event_syscall_enter(file, event);
 794                 return 0;
 795
 796 #ifdef CONFIG_PERF_EVENTS
 797         case TRACE_REG_PERF_REGISTER:
 798                 return perf_sysenter_enable(event);
 799         case TRACE_REG_PERF_UNREGISTER:
 800                 perf_sysenter_disable(event);
 801                 return 0;
 802         case TRACE_REG_PERF_OPEN:
 803         case TRACE_REG_PERF_CLOSE:
 804         case TRACE_REG_PERF_ADD:
 805         case TRACE_REG_PERF_DEL:
 806                 return 0;
 807 #endif
 808         }
 809         return 0;
 810 }
 811
 812 static int syscall_exit_register(struct trace_event_call *event,
 813                                  enum trace_reg type, void *data)
 814 {
 815         struct trace_event_file *file = data;
 816
 817         switch (type) {
 818         case TRACE_REG_REGISTER:
 819                 return reg_event_syscall_exit(file, event);
 820         case TRACE_REG_UNREGISTER:
 821                 unreg_event_syscall_exit(file, event);
 822                 return 0;
 823
 824 #ifdef CONFIG_PERF_EVENTS
 825         case TRACE_REG_PERF_REGISTER:
 826                 return perf_sysexit_enable(event);
 827         case TRACE_REG_PERF_UNREGISTER:
 828                 perf_sysexit_disable(event);
 829                 return 0;
 830         case TRACE_REG_PERF_OPEN:
 831         case TRACE_REG_PERF_CLOSE:
 832         case TRACE_REG_PERF_ADD:
 833         case TRACE_REG_PERF_DEL:
 834                 return 0;
 835 #endif
 836         }
 837         return 0;
 838 }