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, _name) {                                   \
 207         .type = #_type, .name = #_name,                                 \
 208         .size = sizeof(_type), .align = __alignof__(_type),             \
 209         .is_signed = is_signed_type(_type), .filter_type = FILTER_OTHER }
 210
 211 static int __init
 212 __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 213 {
 214         int i;
 215         int pos = 0;
 216
 217         /* When len=0, we just calculate the needed length */
 218 #define LEN_OR_ZERO (len ? len - pos : 0)
 219
 220         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 221         for (i = 0; i < entry->nb_args; i++) {
 222                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 223                                 entry->args[i], sizeof(unsigned long),
 224                                 i == entry->nb_args - 1 ? "" : ", ");
 225         }
 226         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 227
 228         for (i = 0; i < entry->nb_args; i++) {
 229                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 230                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 231         }
 232
 233 #undef LEN_OR_ZERO
 234
 235         /* return the length of print_fmt */
 236         return pos;
 237 }
 238
 239 static int __init set_syscall_print_fmt(struct trace_event_call *call)
 240 {
 241         char *print_fmt;
 242         int len;
 243         struct syscall_metadata *entry = call->data;
 244
 245         if (entry->enter_event != call) {
 246                 call->print_fmt = "\"0x%lx\", REC->ret";
 247                 return 0;
 248         }
 249
 250         /* First: called with 0 length to calculate the needed length */
 251         len = __set_enter_print_fmt(entry, NULL, 0);
 252
 253         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 254         if (!print_fmt)
 255                 return -ENOMEM;
 256
 257         /* Second: actually write the @print_fmt */
 258         __set_enter_print_fmt(entry, print_fmt, len + 1);
 259         call->print_fmt = print_fmt;
 260
 261         return 0;
 262 }
 263
 264 static void __init free_syscall_print_fmt(struct trace_event_call *call)
 265 {
 266         struct syscall_metadata *entry = call->data;
 267
 268         if (entry->enter_event == call)
 269                 kfree(call->print_fmt);
 270 }
 271
 272 static int __init syscall_enter_define_fields(struct trace_event_call *call)
 273 {
 274         struct syscall_trace_enter trace;
 275         struct syscall_metadata *meta = call->data;
 276         int offset = offsetof(typeof(trace), args);
 277         int ret = 0;
 278         int i;
 279
 280         for (i = 0; i < meta->nb_args; i++) {
 281                 ret = trace_define_field(call, meta->types[i],
 282                                          meta->args[i], offset,
 283                                          sizeof(unsigned long), 0,
 284                                          FILTER_OTHER);
 285                 if (ret)
 286                         break;
 287                 offset += sizeof(unsigned long);
 288         }
 289
 290         return ret;
 291 }
 292
 293 static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
 294 {
 295         struct trace_array *tr = data;
 296         struct trace_event_file *trace_file;
 297         struct syscall_trace_enter *entry;
 298         struct syscall_metadata *sys_data;
 299         struct ring_buffer_event *event;
 300         struct trace_buffer *buffer;
 301         unsigned long irq_flags;
 302         unsigned long args[6];
 303         int pc;
 304         int syscall_nr;
 305         int size;
 306
 307         syscall_nr = trace_get_syscall_nr(current, regs);
 308         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 309                 return;
 310
 311         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE) */
 312         trace_file = rcu_dereference_sched(tr->enter_syscall_files[syscall_nr]);
 313         if (!trace_file)
 314                 return;
 315
 316         if (trace_trigger_soft_disabled(trace_file))
 317                 return;
 318
 319         sys_data = syscall_nr_to_meta(syscall_nr);
 320         if (!sys_data)
 321                 return;
 322
 323         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 324
 325         local_save_flags(irq_flags);
 326         pc = preempt_count();
 327
 328         buffer = tr->array_buffer.buffer;
 329         event = trace_buffer_lock_reserve(buffer,
 330                         sys_data->enter_event->event.type, size, irq_flags, pc);
 331         if (!event)
 332                 return;
 333
 334         entry = ring_buffer_event_data(event);
 335         entry->nr = syscall_nr;
 336         syscall_get_arguments(current, regs, args);
 337         memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
 338
 339         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 340                                     irq_flags, pc);
 341 }
 342
 343 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
 344 {
 345         struct trace_array *tr = data;
 346         struct trace_event_file *trace_file;
 347         struct syscall_trace_exit *entry;
 348         struct syscall_metadata *sys_data;
 349         struct ring_buffer_event *event;
 350         struct trace_buffer *buffer;
 351         unsigned long irq_flags;
 352         int pc;
 353         int syscall_nr;
 354
 355         syscall_nr = trace_get_syscall_nr(current, regs);
 356         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 357                 return;
 358
 359         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE()) */
 360         trace_file = rcu_dereference_sched(tr->exit_syscall_files[syscall_nr]);
 361         if (!trace_file)
 362                 return;
 363
 364         if (trace_trigger_soft_disabled(trace_file))
 365                 return;
 366
 367         sys_data = syscall_nr_to_meta(syscall_nr);
 368         if (!sys_data)
 369                 return;
 370
 371         local_save_flags(irq_flags);
 372         pc = preempt_count();
 373
 374         buffer = tr->array_buffer.buffer;
 375         event = trace_buffer_lock_reserve(buffer,
 376                         sys_data->exit_event->event.type, sizeof(*entry),
 377                         irq_flags, pc);
 378         if (!event)
 379                 return;
 380
 381         entry = ring_buffer_event_data(event);
 382         entry->nr = syscall_nr;
 383         entry->ret = syscall_get_return_value(current, regs);
 384
 385         event_trigger_unlock_commit(trace_file, buffer, event, entry,
 386                                     irq_flags, pc);
 387 }
 388
 389 static int reg_event_syscall_enter(struct trace_event_file *file,
 390                                    struct trace_event_call *call)
 391 {
 392         struct trace_array *tr = file->tr;
 393         int ret = 0;
 394         int num;
 395
 396         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 397         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 398                 return -ENOSYS;
 399         mutex_lock(&syscall_trace_lock);
 400         if (!tr->sys_refcount_enter)
 401                 ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
 402         if (!ret) {
 403                 rcu_assign_pointer(tr->enter_syscall_files[num], file);
 404                 tr->sys_refcount_enter++;
 405         }
 406         mutex_unlock(&syscall_trace_lock);
 407         return ret;
 408 }
 409
 410 static void unreg_event_syscall_enter(struct trace_event_file *file,
 411                                       struct trace_event_call *call)
 412 {
 413         struct trace_array *tr = file->tr;
 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;
 419         mutex_lock(&syscall_trace_lock);
 420         tr->sys_refcount_enter--;
 421         RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
 422         if (!tr->sys_refcount_enter)
 423                 unregister_trace_sys_enter(ftrace_syscall_enter, tr);
 424         mutex_unlock(&syscall_trace_lock);
 425 }
 426
 427 static int reg_event_syscall_exit(struct trace_event_file *file,
 428                                   struct trace_event_call *call)
 429 {
 430         struct trace_array *tr = file->tr;
 431         int ret = 0;
 432         int num;
 433
 434         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 435         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 436                 return -ENOSYS;
 437         mutex_lock(&syscall_trace_lock);
 438         if (!tr->sys_refcount_exit)
 439                 ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
 440         if (!ret) {
 441                 rcu_assign_pointer(tr->exit_syscall_files[num], file);
 442                 tr->sys_refcount_exit++;
 443         }
 444         mutex_unlock(&syscall_trace_lock);
 445         return ret;
 446 }
 447
 448 static void unreg_event_syscall_exit(struct trace_event_file *file,
 449                                      struct trace_event_call *call)
 450 {
 451         struct trace_array *tr = file->tr;
 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;
 457         mutex_lock(&syscall_trace_lock);
 458         tr->sys_refcount_exit--;
 459         RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
 460         if (!tr->sys_refcount_exit)
 461                 unregister_trace_sys_exit(ftrace_syscall_exit, tr);
 462         mutex_unlock(&syscall_trace_lock);
 463 }
 464
 465 static int __init init_syscall_trace(struct trace_event_call *call)
 466 {
 467         int id;
 468         int num;
 469
 470         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 471         if (num < 0 || num >= NR_syscalls) {
 472                 pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
 473                                 ((struct syscall_metadata *)call->data)->name);
 474                 return -ENOSYS;
 475         }
 476
 477         if (set_syscall_print_fmt(call) < 0)
 478                 return -ENOMEM;
 479
 480         id = trace_event_raw_init(call);
 481
 482         if (id < 0) {
 483                 free_syscall_print_fmt(call);
 484                 return id;
 485         }
 486
 487         return id;
 488 }
 489
 490 static struct trace_event_fields __refdata syscall_enter_fields_array[] = {
 491         SYSCALL_FIELD(int, __syscall_nr),
 492         { .type = TRACE_FUNCTION_TYPE,
 493           .define_fields = syscall_enter_define_fields },
 494         {}
 495 };
 496
 497 struct trace_event_functions enter_syscall_print_funcs = {
 498         .trace          = print_syscall_enter,
 499 };
 500
 501 struct trace_event_functions exit_syscall_print_funcs = {
 502         .trace          = print_syscall_exit,
 503 };
 504
 505 struct trace_event_class __refdata event_class_syscall_enter = {
 506         .system         = "syscalls",
 507         .reg            = syscall_enter_register,
 508         .fields_array   = syscall_enter_fields_array,
 509         .get_fields     = syscall_get_enter_fields,
 510         .raw_init       = init_syscall_trace,
 511 };
 512
 513 struct trace_event_class __refdata event_class_syscall_exit = {
 514         .system         = "syscalls",
 515         .reg            = syscall_exit_register,
 516         .fields_array   = (struct trace_event_fields[]){
 517                 SYSCALL_FIELD(int, __syscall_nr),
 518                 SYSCALL_FIELD(long, ret),
 519                 {}
 520         },
 521         .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
 522         .raw_init       = init_syscall_trace,
 523 };
 524
 525 unsigned long __init __weak arch_syscall_addr(int nr)
 526 {
 527         return (unsigned long)sys_call_table[nr];
 528 }
 529
 530 void __init init_ftrace_syscalls(void)
 531 {
 532         struct syscall_metadata *meta;
 533         unsigned long addr;
 534         int i;
 535         void *ret;
 536
 537         if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
 538                 syscalls_metadata = kcalloc(NR_syscalls,
 539                                         sizeof(*syscalls_metadata),
 540                                         GFP_KERNEL);
 541                 if (!syscalls_metadata) {
 542                         WARN_ON(1);
 543                         return;
 544                 }
 545         }
 546
 547         for (i = 0; i < NR_syscalls; i++) {
 548                 addr = arch_syscall_addr(i);
 549                 meta = find_syscall_meta(addr);
 550                 if (!meta)
 551                         continue;
 552
 553                 meta->syscall_nr = i;
 554
 555                 if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
 556                         syscalls_metadata[i] = meta;
 557                 } else {
 558                         ret = xa_store(&syscalls_metadata_sparse, i, meta,
 559                                         GFP_KERNEL);
 560                         WARN(xa_is_err(ret),
 561                                 "Syscall memory allocation failed\n");
 562                 }
 563
 564         }
 565 }
 566
 567 #ifdef CONFIG_PERF_EVENTS
 568
 569 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 570 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 571 static int sys_perf_refcount_enter;
 572 static int sys_perf_refcount_exit;
 573
 574 static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *regs,
 575                                struct syscall_metadata *sys_data,
 576                                struct syscall_trace_enter *rec)
 577 {
 578         struct syscall_tp_t {
 579                 unsigned long long regs;
 580                 unsigned long syscall_nr;
 581                 unsigned long args[SYSCALL_DEFINE_MAXARGS];
 582         } param;
 583         int i;
 584
 585         *(struct pt_regs **)&param = regs;
 586         param.syscall_nr = rec->nr;
 587         for (i = 0; i < sys_data->nb_args; i++)
 588                 param.args[i] = rec->args[i];
 589         return trace_call_bpf(call, &param);
 590 }
 591
 592 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 593 {
 594         struct syscall_metadata *sys_data;
 595         struct syscall_trace_enter *rec;
 596         struct hlist_head *head;
 597         unsigned long args[6];
 598         bool valid_prog_array;
 599         int syscall_nr;
 600         int rctx;
 601         int size;
 602
 603         syscall_nr = trace_get_syscall_nr(current, regs);
 604         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 605                 return;
 606         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 607                 return;
 608
 609         sys_data = syscall_nr_to_meta(syscall_nr);
 610         if (!sys_data)
 611                 return;
 612
 613         head = this_cpu_ptr(sys_data->enter_event->perf_events);
 614         valid_prog_array = bpf_prog_array_valid(sys_data->enter_event);
 615         if (!valid_prog_array && hlist_empty(head))
 616                 return;
 617
 618         /* get the size after alignment with the u32 buffer size field */
 619         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 620         size = ALIGN(size + sizeof(u32), sizeof(u64));
 621         size -= sizeof(u32);
 622
 623         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 624         if (!rec)
 625                 return;
 626
 627         rec->nr = syscall_nr;
 628         syscall_get_arguments(current, regs, args);
 629         memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
 630
 631         if ((valid_prog_array &&
 632              !perf_call_bpf_enter(sys_data->enter_event, regs, sys_data, rec)) ||
 633             hlist_empty(head)) {
 634                 perf_swevent_put_recursion_context(rctx);
 635                 return;
 636         }
 637
 638         perf_trace_buf_submit(rec, size, rctx,
 639                               sys_data->enter_event->event.type, 1, regs,
 640                               head, NULL);
 641 }
 642
 643 static int perf_sysenter_enable(struct trace_event_call *call)
 644 {
 645         int ret = 0;
 646         int num;
 647
 648         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 649
 650         mutex_lock(&syscall_trace_lock);
 651         if (!sys_perf_refcount_enter)
 652                 ret = register_trace_sys_enter(perf_syscall_enter, NULL);
 653         if (ret) {
 654                 pr_info("event trace: Could not activate syscall entry trace point");
 655         } else {
 656                 set_bit(num, enabled_perf_enter_syscalls);
 657                 sys_perf_refcount_enter++;
 658         }
 659         mutex_unlock(&syscall_trace_lock);
 660         return ret;
 661 }
 662
 663 static void perf_sysenter_disable(struct trace_event_call *call)
 664 {
 665         int num;
 666
 667         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 668
 669         mutex_lock(&syscall_trace_lock);
 670         sys_perf_refcount_enter--;
 671         clear_bit(num, enabled_perf_enter_syscalls);
 672         if (!sys_perf_refcount_enter)
 673                 unregister_trace_sys_enter(perf_syscall_enter, NULL);
 674         mutex_unlock(&syscall_trace_lock);
 675 }
 676
 677 static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *regs,
 678                               struct syscall_trace_exit *rec)
 679 {
 680         struct syscall_tp_t {
 681                 unsigned long long regs;
 682                 unsigned long syscall_nr;
 683                 unsigned long ret;
 684         } param;
 685
 686         *(struct pt_regs **)&param = regs;
 687         param.syscall_nr = rec->nr;
 688         param.ret = rec->ret;
 689         return trace_call_bpf(call, &param);
 690 }
 691
 692 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 693 {
 694         struct syscall_metadata *sys_data;
 695         struct syscall_trace_exit *rec;
 696         struct hlist_head *head;
 697         bool valid_prog_array;
 698         int syscall_nr;
 699         int rctx;
 700         int size;
 701
 702         syscall_nr = trace_get_syscall_nr(current, regs);
 703         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 704                 return;
 705         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 706                 return;
 707
 708         sys_data = syscall_nr_to_meta(syscall_nr);
 709         if (!sys_data)
 710                 return;
 711
 712         head = this_cpu_ptr(sys_data->exit_event->perf_events);
 713         valid_prog_array = bpf_prog_array_valid(sys_data->exit_event);
 714         if (!valid_prog_array && hlist_empty(head))
 715                 return;
 716
 717         /* We can probably do that at build time */
 718         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 719         size -= sizeof(u32);
 720
 721         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 722         if (!rec)
 723                 return;
 724
 725         rec->nr = syscall_nr;
 726         rec->ret = syscall_get_return_value(current, regs);
 727
 728         if ((valid_prog_array &&
 729              !perf_call_bpf_exit(sys_data->exit_event, regs, rec)) ||
 730             hlist_empty(head)) {
 731                 perf_swevent_put_recursion_context(rctx);
 732                 return;
 733         }
 734
 735         perf_trace_buf_submit(rec, size, rctx, sys_data->exit_event->event.type,
 736                               1, regs, head, NULL);
 737 }
 738
 739 static int perf_sysexit_enable(struct trace_event_call *call)
 740 {
 741         int ret = 0;
 742         int num;
 743
 744         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 745
 746         mutex_lock(&syscall_trace_lock);
 747         if (!sys_perf_refcount_exit)
 748                 ret = register_trace_sys_exit(perf_syscall_exit, NULL);
 749         if (ret) {
 750                 pr_info("event trace: Could not activate syscall exit trace point");
 751         } else {
 752                 set_bit(num, enabled_perf_exit_syscalls);
 753                 sys_perf_refcount_exit++;
 754         }
 755         mutex_unlock(&syscall_trace_lock);
 756         return ret;
 757 }
 758
 759 static void perf_sysexit_disable(struct trace_event_call *call)
 760 {
 761         int num;
 762
 763         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 764
 765         mutex_lock(&syscall_trace_lock);
 766         sys_perf_refcount_exit--;
 767         clear_bit(num, enabled_perf_exit_syscalls);
 768         if (!sys_perf_refcount_exit)
 769                 unregister_trace_sys_exit(perf_syscall_exit, NULL);
 770         mutex_unlock(&syscall_trace_lock);
 771 }
 772
 773 #endif /* CONFIG_PERF_EVENTS */
 774
 775 static int syscall_enter_register(struct trace_event_call *event,
 776                                  enum trace_reg type, void *data)
 777 {
 778         struct trace_event_file *file = data;
 779
 780         switch (type) {
 781         case TRACE_REG_REGISTER:
 782                 return reg_event_syscall_enter(file, event);
 783         case TRACE_REG_UNREGISTER:
 784                 unreg_event_syscall_enter(file, event);
 785                 return 0;
 786
 787 #ifdef CONFIG_PERF_EVENTS
 788         case TRACE_REG_PERF_REGISTER:
 789                 return perf_sysenter_enable(event);
 790         case TRACE_REG_PERF_UNREGISTER:
 791                 perf_sysenter_disable(event);
 792                 return 0;
 793         case TRACE_REG_PERF_OPEN:
 794         case TRACE_REG_PERF_CLOSE:
 795         case TRACE_REG_PERF_ADD:
 796         case TRACE_REG_PERF_DEL:
 797                 return 0;
 798 #endif
 799         }
 800         return 0;
 801 }
 802
 803 static int syscall_exit_register(struct trace_event_call *event,
 804                                  enum trace_reg type, void *data)
 805 {
 806         struct trace_event_file *file = data;
 807
 808         switch (type) {
 809         case TRACE_REG_REGISTER:
 810                 return reg_event_syscall_exit(file, event);
 811         case TRACE_REG_UNREGISTER:
 812                 unreg_event_syscall_exit(file, event);
 813                 return 0;
 814
 815 #ifdef CONFIG_PERF_EVENTS
 816         case TRACE_REG_PERF_REGISTER:
 817                 return perf_sysexit_enable(event);
 818         case TRACE_REG_PERF_UNREGISTER:
 819                 perf_sysexit_disable(event);
 820                 return 0;
 821         case TRACE_REG_PERF_OPEN:
 822         case TRACE_REG_PERF_CLOSE:
 823         case TRACE_REG_PERF_ADD:
 824         case TRACE_REG_PERF_DEL:
 825                 return 0;
 826 #endif
 827         }
 828         return 0;
 829 }