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 && 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 trace_event_buffer fbuffer;
 300         unsigned long args[6];
 301         int syscall_nr;
 302         int size;
 303
 304         syscall_nr = trace_get_syscall_nr(current, regs);
 305         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 306                 return;
 307
 308         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE) */
 309         trace_file = rcu_dereference_sched(tr->enter_syscall_files[syscall_nr]);
 310         if (!trace_file)
 311                 return;
 312
 313         if (trace_trigger_soft_disabled(trace_file))
 314                 return;
 315
 316         sys_data = syscall_nr_to_meta(syscall_nr);
 317         if (!sys_data)
 318                 return;
 319
 320         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 321
 322         entry = trace_event_buffer_reserve(&fbuffer, trace_file, size);
 323         if (!entry)
 324                 return;
 325
 326         entry = ring_buffer_event_data(fbuffer.event);
 327         entry->nr = syscall_nr;
 328         syscall_get_arguments(current, regs, args);
 329         memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
 330
 331         trace_event_buffer_commit(&fbuffer);
 332 }
 333
 334 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
 335 {
 336         struct trace_array *tr = data;
 337         struct trace_event_file *trace_file;
 338         struct syscall_trace_exit *entry;
 339         struct syscall_metadata *sys_data;
 340         struct trace_event_buffer fbuffer;
 341         int syscall_nr;
 342
 343         syscall_nr = trace_get_syscall_nr(current, regs);
 344         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 345                 return;
 346
 347         /* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE()) */
 348         trace_file = rcu_dereference_sched(tr->exit_syscall_files[syscall_nr]);
 349         if (!trace_file)
 350                 return;
 351
 352         if (trace_trigger_soft_disabled(trace_file))
 353                 return;
 354
 355         sys_data = syscall_nr_to_meta(syscall_nr);
 356         if (!sys_data)
 357                 return;
 358
 359         entry = trace_event_buffer_reserve(&fbuffer, trace_file, sizeof(*entry));
 360         if (!entry)
 361                 return;
 362
 363         entry = ring_buffer_event_data(fbuffer.event);
 364         entry->nr = syscall_nr;
 365         entry->ret = syscall_get_return_value(current, regs);
 366
 367         trace_event_buffer_commit(&fbuffer);
 368 }
 369
 370 static int reg_event_syscall_enter(struct trace_event_file *file,
 371                                    struct trace_event_call *call)
 372 {
 373         struct trace_array *tr = file->tr;
 374         int ret = 0;
 375         int num;
 376
 377         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 378         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 379                 return -ENOSYS;
 380         mutex_lock(&syscall_trace_lock);
 381         if (!tr->sys_refcount_enter)
 382                 ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
 383         if (!ret) {
 384                 rcu_assign_pointer(tr->enter_syscall_files[num], file);
 385                 tr->sys_refcount_enter++;
 386         }
 387         mutex_unlock(&syscall_trace_lock);
 388         return ret;
 389 }
 390
 391 static void unreg_event_syscall_enter(struct trace_event_file *file,
 392                                       struct trace_event_call *call)
 393 {
 394         struct trace_array *tr = file->tr;
 395         int num;
 396
 397         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 398         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 399                 return;
 400         mutex_lock(&syscall_trace_lock);
 401         tr->sys_refcount_enter--;
 402         RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
 403         if (!tr->sys_refcount_enter)
 404                 unregister_trace_sys_enter(ftrace_syscall_enter, tr);
 405         mutex_unlock(&syscall_trace_lock);
 406 }
 407
 408 static int reg_event_syscall_exit(struct trace_event_file *file,
 409                                   struct trace_event_call *call)
 410 {
 411         struct trace_array *tr = file->tr;
 412         int ret = 0;
 413         int num;
 414
 415         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 416         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 417                 return -ENOSYS;
 418         mutex_lock(&syscall_trace_lock);
 419         if (!tr->sys_refcount_exit)
 420                 ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
 421         if (!ret) {
 422                 rcu_assign_pointer(tr->exit_syscall_files[num], file);
 423                 tr->sys_refcount_exit++;
 424         }
 425         mutex_unlock(&syscall_trace_lock);
 426         return ret;
 427 }
 428
 429 static void unreg_event_syscall_exit(struct trace_event_file *file,
 430                                      struct trace_event_call *call)
 431 {
 432         struct trace_array *tr = file->tr;
 433         int num;
 434
 435         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 436         if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
 437                 return;
 438         mutex_lock(&syscall_trace_lock);
 439         tr->sys_refcount_exit--;
 440         RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
 441         if (!tr->sys_refcount_exit)
 442                 unregister_trace_sys_exit(ftrace_syscall_exit, tr);
 443         mutex_unlock(&syscall_trace_lock);
 444 }
 445
 446 static int __init init_syscall_trace(struct trace_event_call *call)
 447 {
 448         int id;
 449         int num;
 450
 451         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 452         if (num < 0 || num >= NR_syscalls) {
 453                 pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
 454                                 ((struct syscall_metadata *)call->data)->name);
 455                 return -ENOSYS;
 456         }
 457
 458         if (set_syscall_print_fmt(call) < 0)
 459                 return -ENOMEM;
 460
 461         id = trace_event_raw_init(call);
 462
 463         if (id < 0) {
 464                 free_syscall_print_fmt(call);
 465                 return id;
 466         }
 467
 468         return id;
 469 }
 470
 471 static struct trace_event_fields __refdata syscall_enter_fields_array[] = {
 472         SYSCALL_FIELD(int, __syscall_nr),
 473         { .type = TRACE_FUNCTION_TYPE,
 474           .define_fields = syscall_enter_define_fields },
 475         {}
 476 };
 477
 478 struct trace_event_functions enter_syscall_print_funcs = {
 479         .trace          = print_syscall_enter,
 480 };
 481
 482 struct trace_event_functions exit_syscall_print_funcs = {
 483         .trace          = print_syscall_exit,
 484 };
 485
 486 struct trace_event_class __refdata event_class_syscall_enter = {
 487         .system         = "syscalls",
 488         .reg            = syscall_enter_register,
 489         .fields_array   = syscall_enter_fields_array,
 490         .get_fields     = syscall_get_enter_fields,
 491         .raw_init       = init_syscall_trace,
 492 };
 493
 494 struct trace_event_class __refdata event_class_syscall_exit = {
 495         .system         = "syscalls",
 496         .reg            = syscall_exit_register,
 497         .fields_array   = (struct trace_event_fields[]){
 498                 SYSCALL_FIELD(int, __syscall_nr),
 499                 SYSCALL_FIELD(long, ret),
 500                 {}
 501         },
 502         .fields         = LIST_HEAD_INIT(event_class_syscall_exit.fields),
 503         .raw_init       = init_syscall_trace,
 504 };
 505
 506 unsigned long __init __weak arch_syscall_addr(int nr)
 507 {
 508         return (unsigned long)sys_call_table[nr];
 509 }
 510
 511 void __init init_ftrace_syscalls(void)
 512 {
 513         struct syscall_metadata *meta;
 514         unsigned long addr;
 515         int i;
 516         void *ret;
 517
 518         if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
 519                 syscalls_metadata = kcalloc(NR_syscalls,
 520                                         sizeof(*syscalls_metadata),
 521                                         GFP_KERNEL);
 522                 if (!syscalls_metadata) {
 523                         WARN_ON(1);
 524                         return;
 525                 }
 526         }
 527
 528         for (i = 0; i < NR_syscalls; i++) {
 529                 addr = arch_syscall_addr(i);
 530                 meta = find_syscall_meta(addr);
 531                 if (!meta)
 532                         continue;
 533
 534                 meta->syscall_nr = i;
 535
 536                 if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
 537                         syscalls_metadata[i] = meta;
 538                 } else {
 539                         ret = xa_store(&syscalls_metadata_sparse, i, meta,
 540                                         GFP_KERNEL);
 541                         WARN(xa_is_err(ret),
 542                                 "Syscall memory allocation failed\n");
 543                 }
 544
 545         }
 546 }
 547
 548 #ifdef CONFIG_PERF_EVENTS
 549
 550 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 551 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 552 static int sys_perf_refcount_enter;
 553 static int sys_perf_refcount_exit;
 554
 555 static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *regs,
 556                                struct syscall_metadata *sys_data,
 557                                struct syscall_trace_enter *rec)
 558 {
 559         struct syscall_tp_t {
 560                 unsigned long long regs;
 561                 unsigned long syscall_nr;
 562                 unsigned long args[SYSCALL_DEFINE_MAXARGS];
 563         } param;
 564         int i;
 565
 566         *(struct pt_regs **)&param = regs;
 567         param.syscall_nr = rec->nr;
 568         for (i = 0; i < sys_data->nb_args; i++)
 569                 param.args[i] = rec->args[i];
 570         return trace_call_bpf(call, &param);
 571 }
 572
 573 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
 574 {
 575         struct syscall_metadata *sys_data;
 576         struct syscall_trace_enter *rec;
 577         struct hlist_head *head;
 578         unsigned long args[6];
 579         bool valid_prog_array;
 580         int syscall_nr;
 581         int rctx;
 582         int size;
 583
 584         syscall_nr = trace_get_syscall_nr(current, regs);
 585         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 586                 return;
 587         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 588                 return;
 589
 590         sys_data = syscall_nr_to_meta(syscall_nr);
 591         if (!sys_data)
 592                 return;
 593
 594         head = this_cpu_ptr(sys_data->enter_event->perf_events);
 595         valid_prog_array = bpf_prog_array_valid(sys_data->enter_event);
 596         if (!valid_prog_array && hlist_empty(head))
 597                 return;
 598
 599         /* get the size after alignment with the u32 buffer size field */
 600         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 601         size = ALIGN(size + sizeof(u32), sizeof(u64));
 602         size -= sizeof(u32);
 603
 604         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 605         if (!rec)
 606                 return;
 607
 608         rec->nr = syscall_nr;
 609         syscall_get_arguments(current, regs, args);
 610         memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
 611
 612         if ((valid_prog_array &&
 613              !perf_call_bpf_enter(sys_data->enter_event, regs, sys_data, rec)) ||
 614             hlist_empty(head)) {
 615                 perf_swevent_put_recursion_context(rctx);
 616                 return;
 617         }
 618
 619         perf_trace_buf_submit(rec, size, rctx,
 620                               sys_data->enter_event->event.type, 1, regs,
 621                               head, NULL);
 622 }
 623
 624 static int perf_sysenter_enable(struct trace_event_call *call)
 625 {
 626         int ret = 0;
 627         int num;
 628
 629         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 630
 631         mutex_lock(&syscall_trace_lock);
 632         if (!sys_perf_refcount_enter)
 633                 ret = register_trace_sys_enter(perf_syscall_enter, NULL);
 634         if (ret) {
 635                 pr_info("event trace: Could not activate syscall entry trace point");
 636         } else {
 637                 set_bit(num, enabled_perf_enter_syscalls);
 638                 sys_perf_refcount_enter++;
 639         }
 640         mutex_unlock(&syscall_trace_lock);
 641         return ret;
 642 }
 643
 644 static void perf_sysenter_disable(struct trace_event_call *call)
 645 {
 646         int num;
 647
 648         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 649
 650         mutex_lock(&syscall_trace_lock);
 651         sys_perf_refcount_enter--;
 652         clear_bit(num, enabled_perf_enter_syscalls);
 653         if (!sys_perf_refcount_enter)
 654                 unregister_trace_sys_enter(perf_syscall_enter, NULL);
 655         mutex_unlock(&syscall_trace_lock);
 656 }
 657
 658 static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *regs,
 659                               struct syscall_trace_exit *rec)
 660 {
 661         struct syscall_tp_t {
 662                 unsigned long long regs;
 663                 unsigned long syscall_nr;
 664                 unsigned long ret;
 665         } param;
 666
 667         *(struct pt_regs **)&param = regs;
 668         param.syscall_nr = rec->nr;
 669         param.ret = rec->ret;
 670         return trace_call_bpf(call, &param);
 671 }
 672
 673 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
 674 {
 675         struct syscall_metadata *sys_data;
 676         struct syscall_trace_exit *rec;
 677         struct hlist_head *head;
 678         bool valid_prog_array;
 679         int syscall_nr;
 680         int rctx;
 681         int size;
 682
 683         syscall_nr = trace_get_syscall_nr(current, regs);
 684         if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
 685                 return;
 686         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 687                 return;
 688
 689         sys_data = syscall_nr_to_meta(syscall_nr);
 690         if (!sys_data)
 691                 return;
 692
 693         head = this_cpu_ptr(sys_data->exit_event->perf_events);
 694         valid_prog_array = bpf_prog_array_valid(sys_data->exit_event);
 695         if (!valid_prog_array && hlist_empty(head))
 696                 return;
 697
 698         /* We can probably do that at build time */
 699         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 700         size -= sizeof(u32);
 701
 702         rec = perf_trace_buf_alloc(size, NULL, &rctx);
 703         if (!rec)
 704                 return;
 705
 706         rec->nr = syscall_nr;
 707         rec->ret = syscall_get_return_value(current, regs);
 708
 709         if ((valid_prog_array &&
 710              !perf_call_bpf_exit(sys_data->exit_event, regs, rec)) ||
 711             hlist_empty(head)) {
 712                 perf_swevent_put_recursion_context(rctx);
 713                 return;
 714         }
 715
 716         perf_trace_buf_submit(rec, size, rctx, sys_data->exit_event->event.type,
 717                               1, regs, head, NULL);
 718 }
 719
 720 static int perf_sysexit_enable(struct trace_event_call *call)
 721 {
 722         int ret = 0;
 723         int num;
 724
 725         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 726
 727         mutex_lock(&syscall_trace_lock);
 728         if (!sys_perf_refcount_exit)
 729                 ret = register_trace_sys_exit(perf_syscall_exit, NULL);
 730         if (ret) {
 731                 pr_info("event trace: Could not activate syscall exit trace point");
 732         } else {
 733                 set_bit(num, enabled_perf_exit_syscalls);
 734                 sys_perf_refcount_exit++;
 735         }
 736         mutex_unlock(&syscall_trace_lock);
 737         return ret;
 738 }
 739
 740 static void perf_sysexit_disable(struct trace_event_call *call)
 741 {
 742         int num;
 743
 744         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 745
 746         mutex_lock(&syscall_trace_lock);
 747         sys_perf_refcount_exit--;
 748         clear_bit(num, enabled_perf_exit_syscalls);
 749         if (!sys_perf_refcount_exit)
 750                 unregister_trace_sys_exit(perf_syscall_exit, NULL);
 751         mutex_unlock(&syscall_trace_lock);
 752 }
 753
 754 #endif /* CONFIG_PERF_EVENTS */
 755
 756 static int syscall_enter_register(struct trace_event_call *event,
 757                                  enum trace_reg type, void *data)
 758 {
 759         struct trace_event_file *file = data;
 760
 761         switch (type) {
 762         case TRACE_REG_REGISTER:
 763                 return reg_event_syscall_enter(file, event);
 764         case TRACE_REG_UNREGISTER:
 765                 unreg_event_syscall_enter(file, event);
 766                 return 0;
 767
 768 #ifdef CONFIG_PERF_EVENTS
 769         case TRACE_REG_PERF_REGISTER:
 770                 return perf_sysenter_enable(event);
 771         case TRACE_REG_PERF_UNREGISTER:
 772                 perf_sysenter_disable(event);
 773                 return 0;
 774         case TRACE_REG_PERF_OPEN:
 775         case TRACE_REG_PERF_CLOSE:
 776         case TRACE_REG_PERF_ADD:
 777         case TRACE_REG_PERF_DEL:
 778                 return 0;
 779 #endif
 780         }
 781         return 0;
 782 }
 783
 784 static int syscall_exit_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_exit(file, event);
 792         case TRACE_REG_UNREGISTER:
 793                 unreg_event_syscall_exit(file, event);
 794                 return 0;
 795
 796 #ifdef CONFIG_PERF_EVENTS
 797         case TRACE_REG_PERF_REGISTER:
 798                 return perf_sysexit_enable(event);
 799         case TRACE_REG_PERF_UNREGISTER:
 800                 perf_sysexit_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 }