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