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 <asm/syscall.h>
  11
  12 #include "trace_output.h"
  13 #include "trace.h"
  14
  15 static DEFINE_MUTEX(syscall_trace_lock);
  16
  17 static int syscall_enter_register(struct trace_event_call *event,
  18                                  enum trace_reg type, void *data);
  19 static int syscall_exit_register(struct trace_event_call *event,
  20                                  enum trace_reg type, void *data);
  21
  22 static struct list_head *
  23 syscall_get_enter_fields(struct trace_event_call *call)
  24 {
  25         struct syscall_metadata *entry = call->data;
  26
  27         return &entry->enter_fields;
  28 }
  29
  30 extern struct syscall_metadata *__start_syscalls_metadata[];
  31 extern struct syscall_metadata *__stop_syscalls_metadata[];
  32
  33 static struct syscall_metadata **syscalls_metadata;
  34
  35 #ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
  36 static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
  37 {
  38         /*
  39          * Only compare after the "sys" prefix. Archs that use
  40          * syscall wrappers may have syscalls symbols aliases prefixed
  41          * with ".SyS" or ".sys" instead of "sys", leading to an unwanted
  42          * mismatch.
  43          */
  44         return !strcmp(sym + 3, name + 3);
  45 }
  46 #endif
  47
  48 #ifdef ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
  49 /*
  50  * Some architectures that allow for 32bit applications
  51  * to run on a 64bit kernel, do not map the syscalls for
  52  * the 32bit tasks the same as they do for 64bit tasks.
  53  *
  54  *     *cough*x86*cough*
  55  *
  56  * In such a case, instead of reporting the wrong syscalls,
  57  * simply ignore them.
  58  *
  59  * For an arch to ignore the compat syscalls it needs to
  60  * define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS as well as
  61  * define the function arch_trace_is_compat_syscall() to let
  62  * the tracing system know that it should ignore it.
  63  */
  64 static int
  65 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
  66 {
  67         if (unlikely(arch_trace_is_compat_syscall(regs)))
  68                 return -1;
  69
  70         return syscall_get_nr(task, regs);
  71 }
  72 #else
  73 static inline int
  74 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
  75 {
  76         return syscall_get_nr(task, regs);
  77 }
  78 #endif /* ARCH_TRACE_IGNORE_COMPAT_SYSCALLS */
  79
  80 static __init struct syscall_metadata *
  81 find_syscall_meta(unsigned long syscall)
  82 {
  83         struct syscall_metadata **start;
  84         struct syscall_metadata **stop;
  85         char str[KSYM_SYMBOL_LEN];
  86
  87
  88         start = __start_syscalls_metadata;
  89         stop = __stop_syscalls_metadata;
  90         kallsyms_lookup(syscall, NULL, NULL, NULL, str);
  91
  92         if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
  93                 return NULL;
  94
  95         for ( ; start < stop; start++) {
  96                 if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
  97                         return *start;
  98         }
  99         return NULL;
 100 }
 101
 102 static struct syscall_metadata *syscall_nr_to_meta(int nr)
 103 {
 104         if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
 105                 return NULL;
 106
 107         return syscalls_metadata[nr];
 108 }
 109
 110 const char *get_syscall_name(int syscall)
 111 {
 112         struct syscall_metadata *entry;
 113
 114         entry = syscall_nr_to_meta(syscall);
 115         if (!entry)
 116                 return NULL;
 117
 118         return entry->name;
 119 }
 120
 121 static enum print_line_t
 122 print_syscall_enter(struct trace_iterator *iter, int flags,
 123                     struct trace_event *event)
 124 {
 125         struct trace_array *tr = iter->tr;
 126         struct trace_seq *s = &iter->seq;
 127         struct trace_entry *ent = iter->ent;
 128         struct syscall_trace_enter *trace;
 129         struct syscall_metadata *entry;
 130         int i, syscall;
 131
 132         trace = (typeof(trace))ent;
 133         syscall = trace->nr;
 134         entry = syscall_nr_to_meta(syscall);
 135
 136         if (!entry)
 137                 goto end;
 138
 139         if (entry->enter_event->event.type != ent->type) {
 140                 WARN_ON_ONCE(1);
 141                 goto end;
 142         }
 143
 144         trace_seq_printf(s, "%s(", entry->name);
 145
 146         for (i = 0; i < entry->nb_args; i++) {
 147
 148                 if (trace_seq_has_overflowed(s))
 149                         goto end;
 150
 151                 /* parameter types */
 152                 if (tr->trace_flags & TRACE_ITER_VERBOSE)
 153                         trace_seq_printf(s, "%s ", entry->types[i]);
 154
 155                 /* parameter values */
 156                 trace_seq_printf(s, "%s: %lx%s", entry->args[i],
 157                                  trace->args[i],
 158                                  i == entry->nb_args - 1 ? "" : ", ");
 159         }
 160
 161         trace_seq_putc(s, ')');
 162 end:
 163         trace_seq_putc(s, '\n');
 164
 165         return trace_handle_return(s);
 166 }
 167
 168 static enum print_line_t
 169 print_syscall_exit(struct trace_iterator *iter, int flags,
 170                    struct trace_event *event)
 171 {
 172         struct trace_seq *s = &iter->seq;
 173         struct trace_entry *ent = iter->ent;
 174         struct syscall_trace_exit *trace;
 175         int syscall;
 176         struct syscall_metadata *entry;
 177
 178         trace = (typeof(trace))ent;
 179         syscall = trace->nr;
 180         entry = syscall_nr_to_meta(syscall);
 181
 182         if (!entry) {
 183                 trace_seq_putc(s, '\n');
 184                 goto out;
 185         }
 186
 187         if (entry->exit_event->event.type != ent->type) {
 188                 WARN_ON_ONCE(1);
 189                 return TRACE_TYPE_UNHANDLED;
 190         }
 191
 192         trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
 193                                 trace->ret);
 194
 195  out:
 196         return trace_handle_return(s);
 197 }
 198
 199 extern char *__bad_type_size(void);
 200
 201 #define SYSCALL_FIELD(type, field, name)                                \
 202         sizeof(type) != sizeof(trace.field) ?                           \
 203                 __bad_type_size() :                                     \
 204                 #type, #name, offsetof(typeof(trace), field),           \
 205                 sizeof(trace.field), is_signed_type(type)
 206
 207 static int __init
 208 __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 209 {
 210         int i;
 211         int pos = 0;
 212
 213         /* When len=0, we just calculate the needed length */
 214 #define LEN_OR_ZERO (len ? len - pos : 0)
 215
 216         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 217         for (i = 0; i < entry->nb_args; i++) {
 218                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 219                                 entry->args[i], sizeof(unsigned long),
 220                                 i == entry->nb_args - 1 ? "" : ", ");
 221         }
 222         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 223
 224         for (i = 0; i < entry->nb_args; i++) {
 225                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 226                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 227         }
 228
 229 #undef LEN_OR_ZERO
 230
 231         /* return the length of print_fmt */
 232         return pos;
 233 }
 234
 235 static int __init set_syscall_print_fmt(struct trace_event_call *call)
 236 {
 237         char *print_fmt;
 238         int len;
 239         struct syscall_metadata *entry = call->data;
 240
 241         if (entry->enter_event != call) {
 242                 call->print_fmt = "\"0x%lx\", REC->ret";
 243                 return 0;
 244         }
 245
 246         /* First: called with 0 length to calculate the needed length */
 247         len = __set_enter_print_fmt(entry, NULL, 0);
 248
 249         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 250         if (!print_fmt)
 251                 return -ENOMEM;
 252
 253         /* Second: actually write the @print_fmt */
 254         __set_enter_print_fmt(entry, print_fmt, len + 1);
 255         call->print_fmt = print_fmt;
 256
 257         return 0;
 258 }
 259
 260 static void __init free_syscall_print_fmt(struct trace_event_call *call)
 261 {
 262         struct syscall_metadata *entry = call->data;
 263
 264         if (entry->enter_event == call)
 265                 kfree(call->print_fmt);
 266 }
 267
 268 static int __init syscall_enter_define_fields(struct trace_event_call *call)
 269 {
 270         struct syscall_trace_enter trace;
 271         struct syscall_metadata *meta = call->data;
 272         int ret;
 273         int i;
 274         int offset = offsetof(typeof(trace), args);
 275
 276         ret = trace_define_field(call, SYSCALL_FIELD(int, nr, __syscall_nr),
 277                                  FILTER_OTHER);
 278         if (ret)
 279                 return ret;
 280
 281         for (i = 0; i < meta->nb_args; i++) {
 282                 ret = trace_define_field(call, meta->types[i],
 283                                          meta->args[i], offset,
 284                                          sizeof(unsigned long), 0,
 285                                          FILTER_OTHER);
 286                 offset += sizeof(unsigned long);
 287         }
 288
 289         return ret;
 290 }
 291
 292 static int __init syscall_exit_define_fields(struct trace_event_call *call)
 293 {
 294         struct syscall_trace_exit trace;
 295         int ret;
 296
 297         ret = trace_define_field(call, SYSCALL_FIELD(int, nr, __syscall_nr),
 298                                  FILTER_OTHER);
 299         if (ret)
 300                 return ret;
 301
 302         ret = trace_define_field(call, SYSCALL_FIELD(long, ret, ret),
 303                                  FILTER_OTHER);
 304
 305         return ret;
 306 }
 307
 308 static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 309 {
 310         struct trace_array *tr = data;
 311         struct trace_event_file *trace_file;
 312         struct syscall_trace_enter *entry;
 313         struct syscall_metadata *sys_data;
 314         struct ring_buffer_event *event;
 315         struct ring_buffer *buffer;
 316         unsigned long irq_flags;
 317         int pc;
 318         int syscall_nr;
 319         int size;
 320
 321         syscall_nr = trace_get_syscall_nr(current, regs);
 322         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 323                 return;
 324
 325         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE) */
 326         trace_file = rcu_dereference_sched(tr->enter_syscall_files[syscall_nr]);
 327         if (!trace_file)
 328                 return;
 329
 330         if (trace_trigger_soft_disabled(trace_file))
 331                 return;
 332
 333         sys_data = syscall_nr_to_meta(syscall_nr);
 334         if (!sys_data)
 335                 return;
 336
 337         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 338
 339         local_save_flags(irq_flags);
 340         pc = preempt_count();
 341
 342         buffer = tr->trace_buffer.buffer;
 343         event = trace_buffer_lock_reserve(buffer,
 344                         sys_data->enter_event->event.type, size, irq_flags, pc);
 345         if (!event)
 346                 return;
 347
 348         entry = ring_buffer_event_data(event);
 349         entry->nr = syscall_nr;
 350         syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
 351
 352         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 353                                     irq_flags, pc);
 354 }
 355
 356 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
 357 {
 358         struct trace_array *tr = data;
 359         struct trace_event_file *trace_file;
 360         struct syscall_trace_exit *entry;
 361         struct syscall_metadata *sys_data;
 362         struct ring_buffer_event *event;
 363         struct ring_buffer *buffer;
 364         unsigned long irq_flags;
 365         int pc;
 366         int syscall_nr;
 367
 368         syscall_nr = trace_get_syscall_nr(current, regs);
 369         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 370                 return;
 371
 372         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE()) */
 373         trace_file = rcu_dereference_sched(tr->exit_syscall_files[syscall_nr]);
 374         if (!trace_file)
 375                 return;
 376
 377         if (trace_trigger_soft_disabled(trace_file))
 378                 return;
 379
 380         sys_data = syscall_nr_to_meta(syscall_nr);
 381         if (!sys_data)
 382                 return;
 383
 384         local_save_flags(irq_flags);
 385         pc = preempt_count();
 386
 387         buffer = tr->trace_buffer.buffer;
 388         event = trace_buffer_lock_reserve(buffer,
 389                         sys_data->exit_event->event.type, sizeof(*entry),
 390                         irq_flags, pc);
 391         if (!event)
 392                 return;
 393
 394         entry = ring_buffer_event_data(event);
 395         entry->nr = syscall_nr;
 396         entry->ret = syscall_get_return_value(current, regs);
 397
 398         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 399                                     irq_flags, pc);
 400 }
 401
 402 static int reg_event_syscall_enter(struct trace_event_file *file,
 403                                    struct trace_event_call *call)
 404 {
 405         struct trace_array *tr = file->tr;
 406         int ret = 0;
 407         int num;
 408
 409         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 410         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 411                 return -ENOSYS;
 412         mutex_lock(&syscall_trace_lock);
 413         if (!tr->sys_refcount_enter)
 414                 ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
 415         if (!ret) {
 416                 rcu_assign_pointer(tr->enter_syscall_files[num], file);
 417                 tr->sys_refcount_enter++;
 418         }
 419         mutex_unlock(&syscall_trace_lock);
 420         return ret;
 421 }
 422
 423 static void unreg_event_syscall_enter(struct trace_event_file *file,
 424                                       struct trace_event_call *call)
 425 {
 426         struct trace_array *tr = file->tr;
 427         int num;
 428
 429         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 430         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 431                 return;
 432         mutex_lock(&syscall_trace_lock);
 433         tr->sys_refcount_enter--;
 434         RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
 435         if (!tr->sys_refcount_enter)
 436                 unregister_trace_sys_enter(ftrace_syscall_enter, tr);
 437         mutex_unlock(&syscall_trace_lock);
 438 }
 439
 440 static int reg_event_syscall_exit(struct trace_event_file *file,
 441                                   struct trace_event_call *call)
 442 {
 443         struct trace_array *tr = file->tr;
 444         int ret = 0;
 445         int num;
 446
 447         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 448         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 449                 return -ENOSYS;
 450         mutex_lock(&syscall_trace_lock);
 451         if (!tr->sys_refcount_exit)
 452                 ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
 453         if (!ret) {
 454                 rcu_assign_pointer(tr->exit_syscall_files[num], file);
 455                 tr->sys_refcount_exit++;
 456         }
 457         mutex_unlock(&syscall_trace_lock);
 458         return ret;
 459 }
 460
 461 static void unreg_event_syscall_exit(struct trace_event_file *file,
 462                                      struct trace_event_call *call)
 463 {
 464         struct trace_array *tr = file->tr;
 465         int num;
 466
 467         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 468         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 469                 return;
 470         mutex_lock(&syscall_trace_lock);
 471         tr->sys_refcount_exit--;
 472         RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
 473         if (!tr->sys_refcount_exit)
 474                 unregister_trace_sys_exit(ftrace_syscall_exit, tr);
 475         mutex_unlock(&syscall_trace_lock);
 476 }
 477
 478 static int __init init_syscall_trace(struct trace_event_call *call)
 479 {
 480         int id;
 481         int num;
 482
 483         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 484         if (num < 0 || num >= NR_syscalls) {
 485                 pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
 486                                 ((struct syscall_metadata *)call->data)->name);
 487                 return -ENOSYS;
 488         }
 489
 490         if (set_syscall_print_fmt(call) < 0)
 491                 return -ENOMEM;
 492
 493         id = trace_event_raw_init(call);
 494
 495         if (id < 0) {
 496                 free_syscall_print_fmt(call);
 497                 return id;
 498         }
 499
 500         return id;
 501 }
 502
 503 struct trace_event_functions enter_syscall_print_funcs = {
 504         .trace          = print_syscall_enter,
 505 };
 506
 507 struct trace_event_functions exit_syscall_print_funcs = {
 508         .trace          = print_syscall_exit,
 509 };
 510
 511 struct trace_event_class __refdata event_class_syscall_enter = {
 512         .system         = "syscalls",
 513         .reg            = syscall_enter_register,
 514         .define_fields  = syscall_enter_define_fields,
 515         .get_fields     = syscall_get_enter_fields,
 516         .raw_init       = init_syscall_trace,
 517 };
 518
 519 struct trace_event_class __refdata event_class_syscall_exit = {
 520         .system         = "syscalls",
 521         .reg            = syscall_exit_register,
 522         .define_fields  = syscall_exit_define_fields,
 523         .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
 524         .raw_init       = init_syscall_trace,
 525 };
 526
 527 unsigned long __init __weak arch_syscall_addr(int nr)
 528 {
 529         return (unsigned long)sys_call_table[nr];
 530 }
 531
 532 void __init init_ftrace_syscalls(void)
 533 {
 534         struct syscall_metadata *meta;
 535         unsigned long addr;
 536         int i;
 537
 538         syscalls_metadata = kcalloc(NR_syscalls, sizeof(*syscalls_metadata),
 539                                     GFP_KERNEL);
 540         if (!syscalls_metadata) {
 541                 WARN_ON(1);
 542                 return;
 543         }
 544
 545         for (i = 0; i < NR_syscalls; i++) {
 546                 addr = arch_syscall_addr(i);
 547                 meta = find_syscall_meta(addr);
 548                 if (!meta)
 549                         continue;
 550
 551                 meta->syscall_nr = i;
 552                 syscalls_metadata[i] = meta;
 553         }
 554 }
 555
 556 #ifdef CONFIG_PERF_EVENTS
 557
 558 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 559 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 560 static int sys_perf_refcount_enter;
 561 static int sys_perf_refcount_exit;
 562
 563 static int perf_call_bpf_enter(struct bpf_prog *prog, struct pt_regs *regs,
 564                               struct syscall_metadata *sys_data,
 565                               struct syscall_trace_enter *rec) {
 566         struct syscall_tp_t {
 567                 unsigned long long regs;
 568                 unsigned long syscall_nr;
 569                 unsigned long args[SYSCALL_DEFINE_MAXARGS];
 570         } param;
 571         int i;
 572
 573         *(struct pt_regs **)&param = regs;
 574         param.syscall_nr = rec->nr;
 575         for (i = 0; i < sys_data->nb_args; i++)
 576                 param.args[i] = rec->args[i];
 577         return trace_call_bpf(prog, &param);
 578 }
 579
 580 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 581 {
 582         struct syscall_metadata *sys_data;
 583         struct syscall_trace_enter *rec;
 584         struct hlist_head *head;
 585         struct bpf_prog *prog;
 586         int syscall_nr;
 587         int rctx;
 588         int size;
 589
 590         syscall_nr = trace_get_syscall_nr(current, regs);
 591         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 592                 return;
 593         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 594                 return;
 595
 596         sys_data = syscall_nr_to_meta(syscall_nr);
 597         if (!sys_data)
 598                 return;
 599
 600         prog = READ_ONCE(sys_data->enter_event->prog);
 601         head = this_cpu_ptr(sys_data->enter_event->perf_events);
 602         if (!prog && hlist_empty(head))
 603                 return;
 604
 605         /* get the size after alignment with the u32 buffer size field */
 606         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 607         size = ALIGN(size + sizeof(u32), sizeof(u64));
 608         size -= sizeof(u32);
 609
 610         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 611         if (!rec)
 612                 return;
 613
 614         rec->nr = syscall_nr;
 615         syscall_get_arguments(current, regs, 0, sys_data->nb_args,
 616                                (unsigned long *)&rec->args);
 617
 618         if ((prog && !perf_call_bpf_enter(prog, regs, sys_data, rec)) ||
 619             hlist_empty(head)) {
 620                 perf_swevent_put_recursion_context(rctx);
 621                 return;
 622         }
 623
 624         perf_trace_buf_submit(rec, size, rctx,
 625                               sys_data->enter_event->event.type, 1, regs,
 626                               head, NULL, NULL);
 627 }
 628
 629 static int perf_sysenter_enable(struct trace_event_call *call)
 630 {
 631         int ret = 0;
 632         int num;
 633
 634         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 635
 636         mutex_lock(&syscall_trace_lock);
 637         if (!sys_perf_refcount_enter)
 638                 ret = register_trace_sys_enter(perf_syscall_enter, NULL);
 639         if (ret) {
 640                 pr_info("event trace: Could not activate syscall entry trace point");
 641         } else {
 642                 set_bit(num, enabled_perf_enter_syscalls);
 643                 sys_perf_refcount_enter++;
 644         }
 645         mutex_unlock(&syscall_trace_lock);
 646         return ret;
 647 }
 648
 649 static void perf_sysenter_disable(struct trace_event_call *call)
 650 {
 651         int num;
 652
 653         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 654
 655         mutex_lock(&syscall_trace_lock);
 656         sys_perf_refcount_enter--;
 657         clear_bit(num, enabled_perf_enter_syscalls);
 658         if (!sys_perf_refcount_enter)
 659                 unregister_trace_sys_enter(perf_syscall_enter, NULL);
 660         mutex_unlock(&syscall_trace_lock);
 661 }
 662
 663 static int perf_call_bpf_exit(struct bpf_prog *prog, struct pt_regs *regs,
 664                               struct syscall_trace_exit *rec) {
 665         struct syscall_tp_t {
 666                 unsigned long long regs;
 667                 unsigned long syscall_nr;
 668                 unsigned long ret;
 669         } param;
 670
 671         *(struct pt_regs **)&param = regs;
 672         param.syscall_nr = rec->nr;
 673         param.ret = rec->ret;
 674         return trace_call_bpf(prog, &param);
 675 }
 676
 677 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 678 {
 679         struct syscall_metadata *sys_data;
 680         struct syscall_trace_exit *rec;
 681         struct hlist_head *head;
 682         struct bpf_prog *prog;
 683         int syscall_nr;
 684         int rctx;
 685         int size;
 686
 687         syscall_nr = trace_get_syscall_nr(current, regs);
 688         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 689                 return;
 690         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 691                 return;
 692
 693         sys_data = syscall_nr_to_meta(syscall_nr);
 694         if (!sys_data)
 695                 return;
 696
 697         prog = READ_ONCE(sys_data->exit_event->prog);
 698         head = this_cpu_ptr(sys_data->exit_event->perf_events);
 699         if (!prog && hlist_empty(head))
 700                 return;
 701
 702         /* We can probably do that at build time */
 703         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 704         size -= sizeof(u32);
 705
 706         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 707         if (!rec)
 708                 return;
 709
 710         rec->nr = syscall_nr;
 711         rec->ret = syscall_get_return_value(current, regs);
 712
 713         if ((prog && !perf_call_bpf_exit(prog, regs, rec)) ||
 714             hlist_empty(head)) {
 715                 perf_swevent_put_recursion_context(rctx);
 716                 return;
 717         }
 718
 719         perf_trace_buf_submit(rec, size, rctx, sys_data->exit_event->event.type,
 720                               1, regs, head, NULL, NULL);
 721 }
 722
 723 static int perf_sysexit_enable(struct trace_event_call *call)
 724 {
 725         int ret = 0;
 726         int num;
 727
 728         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 729
 730         mutex_lock(&syscall_trace_lock);
 731         if (!sys_perf_refcount_exit)
 732                 ret = register_trace_sys_exit(perf_syscall_exit, NULL);
 733         if (ret) {
 734                 pr_info("event trace: Could not activate syscall exit trace point");
 735         } else {
 736                 set_bit(num, enabled_perf_exit_syscalls);
 737                 sys_perf_refcount_exit++;
 738         }
 739         mutex_unlock(&syscall_trace_lock);
 740         return ret;
 741 }
 742
 743 static void perf_sysexit_disable(struct trace_event_call *call)
 744 {
 745         int num;
 746
 747         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 748
 749         mutex_lock(&syscall_trace_lock);
 750         sys_perf_refcount_exit--;
 751         clear_bit(num, enabled_perf_exit_syscalls);
 752         if (!sys_perf_refcount_exit)
 753                 unregister_trace_sys_exit(perf_syscall_exit, NULL);
 754         mutex_unlock(&syscall_trace_lock);
 755 }
 756
 757 #endif /* CONFIG_PERF_EVENTS */
 758
 759 static int syscall_enter_register(struct trace_event_call *event,
 760                                  enum trace_reg type, void *data)
 761 {
 762         struct trace_event_file *file = data;
 763
 764         switch (type) {
 765         case TRACE_REG_REGISTER:
 766                 return reg_event_syscall_enter(file, event);
 767         case TRACE_REG_UNREGISTER:
 768                 unreg_event_syscall_enter(file, event);
 769                 return 0;
 770
 771 #ifdef CONFIG_PERF_EVENTS
 772         case TRACE_REG_PERF_REGISTER:
 773                 return perf_sysenter_enable(event);
 774         case TRACE_REG_PERF_UNREGISTER:
 775                 perf_sysenter_disable(event);
 776                 return 0;
 777         case TRACE_REG_PERF_OPEN:
 778         case TRACE_REG_PERF_CLOSE:
 779         case TRACE_REG_PERF_ADD:
 780         case TRACE_REG_PERF_DEL:
 781                 return 0;
 782 #endif
 783         }
 784         return 0;
 785 }
 786
 787 static int syscall_exit_register(struct trace_event_call *event,
 788                                  enum trace_reg type, void *data)
 789 {
 790         struct trace_event_file *file = data;
 791
 792         switch (type) {
 793         case TRACE_REG_REGISTER:
 794                 return reg_event_syscall_exit(file, event);
 795         case TRACE_REG_UNREGISTER:
 796                 unreg_event_syscall_exit(file, event);
 797                 return 0;
 798
 799 #ifdef CONFIG_PERF_EVENTS
 800         case TRACE_REG_PERF_REGISTER:
 801                 return perf_sysexit_enable(event);
 802         case TRACE_REG_PERF_UNREGISTER:
 803                 perf_sysexit_disable(event);
 804                 return 0;
 805         case TRACE_REG_PERF_OPEN:
 806         case TRACE_REG_PERF_CLOSE:
 807         case TRACE_REG_PERF_ADD:
 808         case TRACE_REG_PERF_DEL:
 809                 return 0;
 810 #endif
 811         }
 812         return 0;
 813 }