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