kernel/trace/trace_syscalls.c

   1 #include <trace/syscall.h>
   2 #include <trace/events/syscalls.h>
   3 #include <linux/slab.h>
   4 #include <linux/kernel.h>
   5 #include <linux/ftrace.h>
   6 #include <linux/perf_event.h>
   7 #include <asm/syscall.h>
   8
   9 #include "trace_output.h"
  10 #include "trace.h"
  11
  12 static DEFINE_MUTEX(syscall_trace_lock);
  13 static int sys_refcount_enter;
  14 static int sys_refcount_exit;
  15 static DECLARE_BITMAP(enabled_enter_syscalls, NR_syscalls);
  16 static DECLARE_BITMAP(enabled_exit_syscalls, NR_syscalls);
  17
  18 extern unsigned long __start_syscalls_metadata[];
  19 extern unsigned long __stop_syscalls_metadata[];
  20
  21 static struct syscall_metadata **syscalls_metadata;
  22
  23 static struct syscall_metadata *find_syscall_meta(unsigned long syscall)
  24 {
  25         struct syscall_metadata *start;
  26         struct syscall_metadata *stop;
  27         char str[KSYM_SYMBOL_LEN];
  28
  29
  30         start = (struct syscall_metadata *)__start_syscalls_metadata;
  31         stop = (struct syscall_metadata *)__stop_syscalls_metadata;
  32         kallsyms_lookup(syscall, NULL, NULL, NULL, str);
  33
  34         for ( ; start < stop; start++) {
  35                 /*
  36                  * Only compare after the "sys" prefix. Archs that use
  37                  * syscall wrappers may have syscalls symbols aliases prefixed
  38                  * with "SyS" instead of "sys", leading to an unwanted
  39                  * mismatch.
  40                  */
  41                 if (start->name && !strcmp(start->name + 3, str + 3))
  42                         return start;
  43         }
  44         return NULL;
  45 }
  46
  47 static struct syscall_metadata *syscall_nr_to_meta(int nr)
  48 {
  49         if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
  50                 return NULL;
  51
  52         return syscalls_metadata[nr];
  53 }
  54
  55 enum print_line_t
  56 print_syscall_enter(struct trace_iterator *iter, int flags)
  57 {
  58         struct trace_seq *s = &iter->seq;
  59         struct trace_entry *ent = iter->ent;
  60         struct syscall_trace_enter *trace;
  61         struct syscall_metadata *entry;
  62         int i, ret, syscall;
  63
  64         trace = (typeof(trace))ent;
  65         syscall = trace->nr;
  66         entry = syscall_nr_to_meta(syscall);
  67
  68         if (!entry)
  69                 goto end;
  70
  71         if (entry->enter_event->id != ent->type) {
  72                 WARN_ON_ONCE(1);
  73                 goto end;
  74         }
  75
  76         ret = trace_seq_printf(s, "%s(", entry->name);
  77         if (!ret)
  78                 return TRACE_TYPE_PARTIAL_LINE;
  79
  80         for (i = 0; i < entry->nb_args; i++) {
  81                 /* parameter types */
  82                 if (trace_flags & TRACE_ITER_VERBOSE) {
  83                         ret = trace_seq_printf(s, "%s ", entry->types[i]);
  84                         if (!ret)
  85                                 return TRACE_TYPE_PARTIAL_LINE;
  86                 }
  87                 /* parameter values */
  88                 ret = trace_seq_printf(s, "%s: %lx%s", entry->args[i],
  89                                        trace->args[i],
  90                                        i == entry->nb_args - 1 ? "" : ", ");
  91                 if (!ret)
  92                         return TRACE_TYPE_PARTIAL_LINE;
  93         }
  94
  95         ret = trace_seq_putc(s, ')');
  96         if (!ret)
  97                 return TRACE_TYPE_PARTIAL_LINE;
  98
  99 end:
 100         ret =  trace_seq_putc(s, '\n');
 101         if (!ret)
 102                 return TRACE_TYPE_PARTIAL_LINE;
 103
 104         return TRACE_TYPE_HANDLED;
 105 }
 106
 107 enum print_line_t
 108 print_syscall_exit(struct trace_iterator *iter, int flags)
 109 {
 110         struct trace_seq *s = &iter->seq;
 111         struct trace_entry *ent = iter->ent;
 112         struct syscall_trace_exit *trace;
 113         int syscall;
 114         struct syscall_metadata *entry;
 115         int ret;
 116
 117         trace = (typeof(trace))ent;
 118         syscall = trace->nr;
 119         entry = syscall_nr_to_meta(syscall);
 120
 121         if (!entry) {
 122                 trace_seq_printf(s, "\n");
 123                 return TRACE_TYPE_HANDLED;
 124         }
 125
 126         if (entry->exit_event->id != ent->type) {
 127                 WARN_ON_ONCE(1);
 128                 return TRACE_TYPE_UNHANDLED;
 129         }
 130
 131         ret = trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
 132                                 trace->ret);
 133         if (!ret)
 134                 return TRACE_TYPE_PARTIAL_LINE;
 135
 136         return TRACE_TYPE_HANDLED;
 137 }
 138
 139 extern char *__bad_type_size(void);
 140
 141 #define SYSCALL_FIELD(type, name)                                       \
 142         sizeof(type) != sizeof(trace.name) ?                            \
 143                 __bad_type_size() :                                     \
 144                 #type, #name, offsetof(typeof(trace), name),            \
 145                 sizeof(trace.name), is_signed_type(type)
 146
 147 static
 148 int  __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
 149 {
 150         int i;
 151         int pos = 0;
 152
 153         /* When len=0, we just calculate the needed length */
 154 #define LEN_OR_ZERO (len ? len - pos : 0)
 155
 156         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 157         for (i = 0; i < entry->nb_args; i++) {
 158                 pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
 159                                 entry->args[i], sizeof(unsigned long),
 160                                 i == entry->nb_args - 1 ? "" : ", ");
 161         }
 162         pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
 163
 164         for (i = 0; i < entry->nb_args; i++) {
 165                 pos += snprintf(buf + pos, LEN_OR_ZERO,
 166                                 ", ((unsigned long)(REC->%s))", entry->args[i]);
 167         }
 168
 169 #undef LEN_OR_ZERO
 170
 171         /* return the length of print_fmt */
 172         return pos;
 173 }
 174
 175 static int set_syscall_print_fmt(struct ftrace_event_call *call)
 176 {
 177         char *print_fmt;
 178         int len;
 179         struct syscall_metadata *entry = call->data;
 180
 181         if (entry->enter_event != call) {
 182                 call->print_fmt = "\"0x%lx\", REC->ret";
 183                 return 0;
 184         }
 185
 186         /* First: called with 0 length to calculate the needed length */
 187         len = __set_enter_print_fmt(entry, NULL, 0);
 188
 189         print_fmt = kmalloc(len + 1, GFP_KERNEL);
 190         if (!print_fmt)
 191                 return -ENOMEM;
 192
 193         /* Second: actually write the @print_fmt */
 194         __set_enter_print_fmt(entry, print_fmt, len + 1);
 195         call->print_fmt = print_fmt;
 196
 197         return 0;
 198 }
 199
 200 static void free_syscall_print_fmt(struct ftrace_event_call *call)
 201 {
 202         struct syscall_metadata *entry = call->data;
 203
 204         if (entry->enter_event == call)
 205                 kfree(call->print_fmt);
 206 }
 207
 208 int syscall_enter_define_fields(struct ftrace_event_call *call)
 209 {
 210         struct syscall_trace_enter trace;
 211         struct syscall_metadata *meta = call->data;
 212         int ret;
 213         int i;
 214         int offset = offsetof(typeof(trace), args);
 215
 216         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 217         if (ret)
 218                 return ret;
 219
 220         for (i = 0; i < meta->nb_args; i++) {
 221                 ret = trace_define_field(call, meta->types[i],
 222                                          meta->args[i], offset,
 223                                          sizeof(unsigned long), 0,
 224                                          FILTER_OTHER);
 225                 offset += sizeof(unsigned long);
 226         }
 227
 228         return ret;
 229 }
 230
 231 int syscall_exit_define_fields(struct ftrace_event_call *call)
 232 {
 233         struct syscall_trace_exit trace;
 234         int ret;
 235
 236         ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
 237         if (ret)
 238                 return ret;
 239
 240         ret = trace_define_field(call, SYSCALL_FIELD(long, ret),
 241                                  FILTER_OTHER);
 242
 243         return ret;
 244 }
 245
 246 void ftrace_syscall_enter(struct pt_regs *regs, long id)
 247 {
 248         struct syscall_trace_enter *entry;
 249         struct syscall_metadata *sys_data;
 250         struct ring_buffer_event *event;
 251         struct ring_buffer *buffer;
 252         int size;
 253         int syscall_nr;
 254
 255         syscall_nr = syscall_get_nr(current, regs);
 256         if (syscall_nr < 0)
 257                 return;
 258         if (!test_bit(syscall_nr, enabled_enter_syscalls))
 259                 return;
 260
 261         sys_data = syscall_nr_to_meta(syscall_nr);
 262         if (!sys_data)
 263                 return;
 264
 265         size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
 266
 267         event = trace_current_buffer_lock_reserve(&buffer,
 268                         sys_data->enter_event->id, size, 0, 0);
 269         if (!event)
 270                 return;
 271
 272         entry = ring_buffer_event_data(event);
 273         entry->nr = syscall_nr;
 274         syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
 275
 276         if (!filter_current_check_discard(buffer, sys_data->enter_event,
 277                                           entry, event))
 278                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 279 }
 280
 281 void ftrace_syscall_exit(struct pt_regs *regs, long ret)
 282 {
 283         struct syscall_trace_exit *entry;
 284         struct syscall_metadata *sys_data;
 285         struct ring_buffer_event *event;
 286         struct ring_buffer *buffer;
 287         int syscall_nr;
 288
 289         syscall_nr = syscall_get_nr(current, regs);
 290         if (syscall_nr < 0)
 291                 return;
 292         if (!test_bit(syscall_nr, enabled_exit_syscalls))
 293                 return;
 294
 295         sys_data = syscall_nr_to_meta(syscall_nr);
 296         if (!sys_data)
 297                 return;
 298
 299         event = trace_current_buffer_lock_reserve(&buffer,
 300                         sys_data->exit_event->id, sizeof(*entry), 0, 0);
 301         if (!event)
 302                 return;
 303
 304         entry = ring_buffer_event_data(event);
 305         entry->nr = syscall_nr;
 306         entry->ret = syscall_get_return_value(current, regs);
 307
 308         if (!filter_current_check_discard(buffer, sys_data->exit_event,
 309                                           entry, event))
 310                 trace_current_buffer_unlock_commit(buffer, event, 0, 0);
 311 }
 312
 313 int reg_event_syscall_enter(struct ftrace_event_call *call)
 314 {
 315         int ret = 0;
 316         int num;
 317
 318         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 319         if (num < 0 || num >= NR_syscalls)
 320                 return -ENOSYS;
 321         mutex_lock(&syscall_trace_lock);
 322         if (!sys_refcount_enter)
 323                 ret = register_trace_sys_enter(ftrace_syscall_enter);
 324         if (!ret) {
 325                 set_bit(num, enabled_enter_syscalls);
 326                 sys_refcount_enter++;
 327         }
 328         mutex_unlock(&syscall_trace_lock);
 329         return ret;
 330 }
 331
 332 void unreg_event_syscall_enter(struct ftrace_event_call *call)
 333 {
 334         int num;
 335
 336         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 337         if (num < 0 || num >= NR_syscalls)
 338                 return;
 339         mutex_lock(&syscall_trace_lock);
 340         sys_refcount_enter--;
 341         clear_bit(num, enabled_enter_syscalls);
 342         if (!sys_refcount_enter)
 343                 unregister_trace_sys_enter(ftrace_syscall_enter);
 344         mutex_unlock(&syscall_trace_lock);
 345 }
 346
 347 int reg_event_syscall_exit(struct ftrace_event_call *call)
 348 {
 349         int ret = 0;
 350         int num;
 351
 352         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 353         if (num < 0 || num >= NR_syscalls)
 354                 return -ENOSYS;
 355         mutex_lock(&syscall_trace_lock);
 356         if (!sys_refcount_exit)
 357                 ret = register_trace_sys_exit(ftrace_syscall_exit);
 358         if (!ret) {
 359                 set_bit(num, enabled_exit_syscalls);
 360                 sys_refcount_exit++;
 361         }
 362         mutex_unlock(&syscall_trace_lock);
 363         return ret;
 364 }
 365
 366 void unreg_event_syscall_exit(struct ftrace_event_call *call)
 367 {
 368         int num;
 369
 370         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 371         if (num < 0 || num >= NR_syscalls)
 372                 return;
 373         mutex_lock(&syscall_trace_lock);
 374         sys_refcount_exit--;
 375         clear_bit(num, enabled_exit_syscalls);
 376         if (!sys_refcount_exit)
 377                 unregister_trace_sys_exit(ftrace_syscall_exit);
 378         mutex_unlock(&syscall_trace_lock);
 379 }
 380
 381 int init_syscall_trace(struct ftrace_event_call *call)
 382 {
 383         int id;
 384
 385         if (set_syscall_print_fmt(call) < 0)
 386                 return -ENOMEM;
 387
 388         id = trace_event_raw_init(call);
 389
 390         if (id < 0) {
 391                 free_syscall_print_fmt(call);
 392                 return id;
 393         }
 394
 395         return id;
 396 }
 397
 398 unsigned long __init arch_syscall_addr(int nr)
 399 {
 400         return (unsigned long)sys_call_table[nr];
 401 }
 402
 403 int __init init_ftrace_syscalls(void)
 404 {
 405         struct syscall_metadata *meta;
 406         unsigned long addr;
 407         int i;
 408
 409         syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
 410                                         NR_syscalls, GFP_KERNEL);
 411         if (!syscalls_metadata) {
 412                 WARN_ON(1);
 413                 return -ENOMEM;
 414         }
 415
 416         for (i = 0; i < NR_syscalls; i++) {
 417                 addr = arch_syscall_addr(i);
 418                 meta = find_syscall_meta(addr);
 419                 if (!meta)
 420                         continue;
 421
 422                 meta->syscall_nr = i;
 423                 syscalls_metadata[i] = meta;
 424         }
 425
 426         return 0;
 427 }
 428 core_initcall(init_ftrace_syscalls);
 429
 430 #ifdef CONFIG_PERF_EVENTS
 431
 432 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
 433 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
 434 static int sys_perf_refcount_enter;
 435 static int sys_perf_refcount_exit;
 436
 437 static void perf_syscall_enter(struct pt_regs *regs, long id)
 438 {
 439         struct syscall_metadata *sys_data;
 440         struct syscall_trace_enter *rec;
 441         unsigned long flags;
 442         int syscall_nr;
 443         int rctx;
 444         int size;
 445
 446         syscall_nr = syscall_get_nr(current, regs);
 447         if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
 448                 return;
 449
 450         sys_data = syscall_nr_to_meta(syscall_nr);
 451         if (!sys_data)
 452                 return;
 453
 454         /* get the size after alignment with the u32 buffer size field */
 455         size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
 456         size = ALIGN(size + sizeof(u32), sizeof(u64));
 457         size -= sizeof(u32);
 458
 459         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
 460                       "perf buffer not large enough"))
 461                 return;
 462
 463         rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
 464                                 sys_data->enter_event->id, &rctx, &flags);
 465         if (!rec)
 466                 return;
 467
 468         rec->nr = syscall_nr;
 469         syscall_get_arguments(current, regs, 0, sys_data->nb_args,
 470                                (unsigned long *)&rec->args);
 471         perf_trace_buf_submit(rec, size, rctx, 0, 1, flags, regs);
 472 }
 473
 474 int perf_sysenter_enable(struct ftrace_event_call *call)
 475 {
 476         int ret = 0;
 477         int num;
 478
 479         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 480
 481         mutex_lock(&syscall_trace_lock);
 482         if (!sys_perf_refcount_enter)
 483                 ret = register_trace_sys_enter(perf_syscall_enter);
 484         if (ret) {
 485                 pr_info("event trace: Could not activate"
 486                                 "syscall entry trace point");
 487         } else {
 488                 set_bit(num, enabled_perf_enter_syscalls);
 489                 sys_perf_refcount_enter++;
 490         }
 491         mutex_unlock(&syscall_trace_lock);
 492         return ret;
 493 }
 494
 495 void perf_sysenter_disable(struct ftrace_event_call *call)
 496 {
 497         int num;
 498
 499         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 500
 501         mutex_lock(&syscall_trace_lock);
 502         sys_perf_refcount_enter--;
 503         clear_bit(num, enabled_perf_enter_syscalls);
 504         if (!sys_perf_refcount_enter)
 505                 unregister_trace_sys_enter(perf_syscall_enter);
 506         mutex_unlock(&syscall_trace_lock);
 507 }
 508
 509 static void perf_syscall_exit(struct pt_regs *regs, long ret)
 510 {
 511         struct syscall_metadata *sys_data;
 512         struct syscall_trace_exit *rec;
 513         unsigned long flags;
 514         int syscall_nr;
 515         int rctx;
 516         int size;
 517
 518         syscall_nr = syscall_get_nr(current, regs);
 519         if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
 520                 return;
 521
 522         sys_data = syscall_nr_to_meta(syscall_nr);
 523         if (!sys_data)
 524                 return;
 525
 526         /* We can probably do that at build time */
 527         size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
 528         size -= sizeof(u32);
 529
 530         /*
 531          * Impossible, but be paranoid with the future
 532          * How to put this check outside runtime?
 533          */
 534         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
 535                 "exit event has grown above perf buffer size"))
 536                 return;
 537
 538         rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
 539                                 sys_data->exit_event->id, &rctx, &flags);
 540         if (!rec)
 541                 return;
 542
 543         rec->nr = syscall_nr;
 544         rec->ret = syscall_get_return_value(current, regs);
 545
 546         perf_trace_buf_submit(rec, size, rctx, 0, 1, flags, regs);
 547 }
 548
 549 int perf_sysexit_enable(struct ftrace_event_call *call)
 550 {
 551         int ret = 0;
 552         int num;
 553
 554         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 555
 556         mutex_lock(&syscall_trace_lock);
 557         if (!sys_perf_refcount_exit)
 558                 ret = register_trace_sys_exit(perf_syscall_exit);
 559         if (ret) {
 560                 pr_info("event trace: Could not activate"
 561                                 "syscall exit trace point");
 562         } else {
 563                 set_bit(num, enabled_perf_exit_syscalls);
 564                 sys_perf_refcount_exit++;
 565         }
 566         mutex_unlock(&syscall_trace_lock);
 567         return ret;
 568 }
 569
 570 void perf_sysexit_disable(struct ftrace_event_call *call)
 571 {
 572         int num;
 573
 574         num = ((struct syscall_metadata *)call->data)->syscall_nr;
 575
 576         mutex_lock(&syscall_trace_lock);
 577         sys_perf_refcount_exit--;
 578         clear_bit(num, enabled_perf_exit_syscalls);
 579         if (!sys_perf_refcount_exit)
 580                 unregister_trace_sys_exit(perf_syscall_exit);
 581         mutex_unlock(&syscall_trace_lock);
 582 }
 583
 584 #endif /* CONFIG_PERF_EVENTS */
 585