mono/mini/mini-posix.c

   1 /*
   2  * mini-posix.c: POSIX signal handling support for Mono.
   3  *
   4  * Authors:
   5  *   Mono Team (mono-list@lists.ximian.com)
   6  *
   7  * Copyright 2001-2003 Ximian, Inc.
   8  * Copyright 2003-2008 Ximian, Inc.
   9  * Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
  10  *
  11  * See LICENSE for licensing information.
  12  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
  13  */
  14 #include <config.h>
  15 #include <signal.h>
  16 #ifdef HAVE_ALLOCA_H
  17 #include <alloca.h>
  18 #endif
  19 #ifdef HAVE_UNISTD_H
  20 #include <unistd.h>
  21 #endif
  22 #include <math.h>
  23 #ifdef HAVE_SYS_TIME_H
  24 #include <sys/time.h>
  25 #endif
  26 #ifdef HAVE_SYS_SYSCALL_H
  27 #include <sys/syscall.h>
  28 #endif
  29 #include <errno.h>
  30 #include <sched.h>
  31
  32 #include <mono/metadata/assembly.h>
  33 #include <mono/metadata/loader.h>
  34 #include <mono/metadata/tabledefs.h>
  35 #include <mono/metadata/class.h>
  36 #include <mono/metadata/object.h>
  37 #include <mono/metadata/tokentype.h>
  38 #include <mono/metadata/tabledefs.h>
  39 #include <mono/metadata/threads.h>
  40 #include <mono/metadata/appdomain.h>
  41 #include <mono/metadata/debug-helpers.h>
  42 #include <mono/io-layer/io-layer.h>
  43 #include "mono/metadata/profiler.h"
  44 #include <mono/metadata/profiler-private.h>
  45 #include <mono/metadata/mono-config.h>
  46 #include <mono/metadata/environment.h>
  47 #include <mono/metadata/mono-debug.h>
  48 #include <mono/metadata/gc-internals.h>
  49 #include <mono/metadata/threads-types.h>
  50 #include <mono/metadata/verify.h>
  51 #include <mono/metadata/verify-internals.h>
  52 #include <mono/metadata/mempool-internals.h>
  53 #include <mono/metadata/attach.h>
  54 #include <mono/utils/mono-math.h>
  55 #include <mono/utils/mono-compiler.h>
  56 #include <mono/utils/mono-counters.h>
  57 #include <mono/utils/mono-logger-internals.h>
  58 #include <mono/utils/mono-mmap.h>
  59 #include <mono/utils/dtrace.h>
  60 #include <mono/utils/mono-signal-handler.h>
  61 #include <mono/utils/mono-threads.h>
  62 #include <mono/utils/mono-threads-posix-signals.h>
  63
  64 #include "mini.h"
  65 #include <string.h>
  66 #include <ctype.h>
  67 #include "trace.h"
  68 #include "version.h"
  69 #include "debugger-agent.h"
  70
  71 #include "jit-icalls.h"
  72
  73 #ifdef PLATFORM_MACOSX
  74 #include <mach/mach.h>
  75 #include <mach/mach_time.h>
  76 #include <mach/clock.h>
  77 #endif
  78
  79 #if defined(__native_client__) || defined(HOST_WATCHOS)
  80
  81 void
  82 mono_runtime_setup_stat_profiler (void)
  83 {
  84         printf("WARNING: mono_runtime_setup_stat_profiler() called!\n");
  85 }
  86
  87
  88 void
  89 mono_runtime_shutdown_stat_profiler (void)
  90 {
  91 }
  92
  93
  94 gboolean
  95 MONO_SIG_HANDLER_SIGNATURE (mono_chain_signal)
  96 {
  97         return FALSE;
  98 }
  99
 100 #ifndef PLATFORM_MACOSX
 101 void
 102 mono_runtime_install_handlers (void)
 103 {
 104 }
 105 #endif
 106
 107 void
 108 mono_runtime_posix_install_handlers(void)
 109 {
 110
 111 }
 112
 113 void
 114 mono_runtime_shutdown_handlers (void)
 115 {
 116 }
 117
 118 void
 119 mono_runtime_cleanup_handlers (void)
 120 {
 121 }
 122
 123 #if !defined(PLATFORM_MACOSX)
 124 pid_t
 125 mono_runtime_syscall_fork (void)
 126 {
 127         g_assert_not_reached();
 128         return 0;
 129 }
 130
 131 void
 132 mono_gdb_render_native_backtraces (pid_t crashed_pid)
 133 {
 134 }
 135 #endif
 136
 137 #else
 138
 139 static GHashTable *mono_saved_signal_handlers = NULL;
 140
 141 static struct sigaction *
 142 get_saved_signal_handler (int signo)
 143 {
 144         if (mono_saved_signal_handlers)
 145                 /* The hash is only modified during startup, so no need for locking */
 146                 return (struct sigaction *)g_hash_table_lookup (mono_saved_signal_handlers, GINT_TO_POINTER (signo));
 147         return NULL;
 148 }
 149
 150 static void
 151 save_old_signal_handler (int signo, struct sigaction *old_action)
 152 {
 153         struct sigaction *handler_to_save = (struct sigaction *)g_malloc (sizeof (struct sigaction));
 154
 155         mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_CONFIG,
 156                                 "Saving old signal handler for signal %d.", signo);
 157
 158         if (! (old_action->sa_flags & SA_SIGINFO)) {
 159                 handler_to_save->sa_handler = old_action->sa_handler;
 160         } else {
 161 #ifdef MONO_ARCH_USE_SIGACTION
 162                 handler_to_save->sa_sigaction = old_action->sa_sigaction;
 163 #endif /* MONO_ARCH_USE_SIGACTION */
 164         }
 165         handler_to_save->sa_mask = old_action->sa_mask;
 166         handler_to_save->sa_flags = old_action->sa_flags;
 167
 168         if (!mono_saved_signal_handlers)
 169                 mono_saved_signal_handlers = g_hash_table_new (NULL, NULL);
 170         g_hash_table_insert (mono_saved_signal_handlers, GINT_TO_POINTER (signo), handler_to_save);
 171 }
 172
 173 static void
 174 free_saved_sig_handler_func (gpointer key, gpointer value, gpointer user_data)
 175 {
 176         g_free (value);
 177 }
 178
 179 static void
 180 free_saved_signal_handlers (void)
 181 {
 182         if (mono_saved_signal_handlers) {
 183                 g_hash_table_foreach (mono_saved_signal_handlers, free_saved_sig_handler_func, NULL);
 184                 g_hash_table_destroy (mono_saved_signal_handlers);
 185                 mono_saved_signal_handlers = NULL;
 186         }
 187 }
 188
 189 /*
 190  * mono_chain_signal:
 191  *
 192  *   Call the original signal handler for the signal given by the arguments, which
 193  * should be the same as for a signal handler. Returns TRUE if the original handler
 194  * was called, false otherwise.
 195  */
 196 gboolean
 197 MONO_SIG_HANDLER_SIGNATURE (mono_chain_signal)
 198 {
 199         int signal = MONO_SIG_HANDLER_GET_SIGNO ();
 200         struct sigaction *saved_handler = (struct sigaction *)get_saved_signal_handler (signal);
 201
 202         if (saved_handler && saved_handler->sa_handler) {
 203                 if (!(saved_handler->sa_flags & SA_SIGINFO)) {
 204                         saved_handler->sa_handler (signal);
 205                 } else {
 206 #ifdef MONO_ARCH_USE_SIGACTION
 207                         saved_handler->sa_sigaction (MONO_SIG_HANDLER_PARAMS);
 208 #endif /* MONO_ARCH_USE_SIGACTION */
 209                 }
 210                 return TRUE;
 211         }
 212         return FALSE;
 213 }
 214
 215 MONO_SIG_HANDLER_FUNC (static, sigabrt_signal_handler)
 216 {
 217         MonoJitInfo *ji = NULL;
 218         MONO_SIG_HANDLER_INFO_TYPE *info = MONO_SIG_HANDLER_GET_INFO ();
 219         MONO_SIG_HANDLER_GET_CONTEXT;
 220
 221         if (mono_thread_internal_current ())
 222                 ji = mono_jit_info_table_find_internal (mono_domain_get (), (char *)mono_arch_ip_from_context (ctx), TRUE, TRUE);
 223         if (!ji) {
 224         if (mono_chain_signal (MONO_SIG_HANDLER_PARAMS))
 225                         return;
 226                 mono_handle_native_sigsegv (SIGABRT, ctx, info);
 227         }
 228 }
 229
 230 #if defined(__i386__) || defined(__x86_64__)
 231 #define FULL_STAT_PROFILER_BACKTRACE 1
 232 #define CURRENT_FRAME_GET_BASE_POINTER(f) (* (gpointer*)(f))
 233 #define CURRENT_FRAME_GET_RETURN_ADDRESS(f) (* (((gpointer*)(f)) + 1))
 234 #if MONO_ARCH_STACK_GROWS_UP
 235 #define IS_BEFORE_ON_STACK <
 236 #define IS_AFTER_ON_STACK >
 237 #else
 238 #define IS_BEFORE_ON_STACK >
 239 #define IS_AFTER_ON_STACK <
 240 #endif
 241 #else
 242 #define FULL_STAT_PROFILER_BACKTRACE 0
 243 #endif
 244
 245 #if (defined (USE_POSIX_BACKEND) && defined (SIGRTMIN)) || defined (SIGPROF)
 246 #define HAVE_PROFILER_SIGNAL
 247 #endif
 248
 249 #ifdef HAVE_PROFILER_SIGNAL
 250
 251 static void
 252 per_thread_profiler_hit (void *ctx)
 253 {
 254         int call_chain_depth = mono_profiler_stat_get_call_chain_depth ();
 255         MonoProfilerCallChainStrategy call_chain_strategy = mono_profiler_stat_get_call_chain_strategy ();
 256
 257         if (call_chain_depth == 0) {
 258                 mono_profiler_stat_hit ((guchar *)mono_arch_ip_from_context (ctx), ctx);
 259         } else {
 260                 MonoJitTlsData *jit_tls = (MonoJitTlsData *)mono_native_tls_get_value (mono_jit_tls_id);
 261                 int current_frame_index = 1;
 262                 MonoContext mono_context;
 263                 guchar *ips [call_chain_depth + 1];
 264
 265                 mono_sigctx_to_monoctx (ctx, &mono_context);
 266                 ips [0] = (guchar *)MONO_CONTEXT_GET_IP (&mono_context);
 267
 268                 if (jit_tls != NULL) {
 269                         if (call_chain_strategy == MONO_PROFILER_CALL_CHAIN_NATIVE) {
 270 #if FULL_STAT_PROFILER_BACKTRACE
 271                         guchar *current_frame;
 272                         guchar *stack_bottom;
 273                         guchar *stack_top;
 274
 275                         stack_bottom = (guchar *)jit_tls->end_of_stack;
 276                         stack_top = (guchar *)MONO_CONTEXT_GET_SP (&mono_context);
 277                         current_frame = (guchar *)MONO_CONTEXT_GET_BP (&mono_context);
 278
 279                         while ((current_frame_index <= call_chain_depth) &&
 280                                         (stack_bottom IS_BEFORE_ON_STACK (guchar*) current_frame) &&
 281                                         ((guchar*) current_frame IS_BEFORE_ON_STACK stack_top)) {
 282                                 ips [current_frame_index] = (guchar *)CURRENT_FRAME_GET_RETURN_ADDRESS (current_frame);
 283                                 current_frame_index ++;
 284                                 stack_top = current_frame;
 285                                 current_frame = (guchar *)CURRENT_FRAME_GET_BASE_POINTER (current_frame);
 286                         }
 287 #else
 288                                 call_chain_strategy = MONO_PROFILER_CALL_CHAIN_GLIBC;
 289 #endif
 290                         }
 291
 292                         if (call_chain_strategy == MONO_PROFILER_CALL_CHAIN_GLIBC) {
 293 #if GLIBC_PROFILER_BACKTRACE
 294                                 current_frame_index = backtrace ((void**) & ips [1], call_chain_depth);
 295 #else
 296                                 call_chain_strategy = MONO_PROFILER_CALL_CHAIN_MANAGED;
 297 #endif
 298                         }
 299
 300                         if (call_chain_strategy == MONO_PROFILER_CALL_CHAIN_MANAGED) {
 301                                 MonoDomain *domain = mono_domain_get ();
 302                                 if (domain != NULL) {
 303                                         MonoLMF *lmf = NULL;
 304                                         MonoJitInfo *ji;
 305                                         MonoJitInfo res;
 306                                         MonoContext new_mono_context;
 307                                         int native_offset;
 308                                         ji = mono_find_jit_info (domain, jit_tls, &res, NULL, &mono_context,
 309                                                         &new_mono_context, NULL, &lmf, &native_offset, NULL);
 310                                         while ((ji != NULL) && (current_frame_index <= call_chain_depth)) {
 311                                                 ips [current_frame_index] = (guchar *)MONO_CONTEXT_GET_IP (&new_mono_context);
 312                                                 current_frame_index ++;
 313                                                 mono_context = new_mono_context;
 314                                                 ji = mono_find_jit_info (domain, jit_tls, &res, NULL, &mono_context,
 315                                                                 &new_mono_context, NULL, &lmf, &native_offset, NULL);
 316                                         }
 317                                 }
 318                         }
 319                 }
 320
 321                 mono_profiler_stat_call_chain (current_frame_index, & ips [0], ctx);
 322         }
 323 }
 324
 325 static gint32 profiler_signals_sent;
 326 static gint32 profiler_signals_received;
 327 static gint32 profiler_signals_accepted;
 328
 329 MONO_SIG_HANDLER_FUNC (static, profiler_signal_handler)
 330 {
 331         int old_errno = errno;
 332         int hp_save_index;
 333         MONO_SIG_HANDLER_GET_CONTEXT;
 334
 335         InterlockedIncrement (&profiler_signals_received);
 336
 337         if (mono_thread_info_get_small_id () == -1)
 338                 return; //an non-attached thread got the signal
 339
 340         if (!mono_domain_get () || !mono_native_tls_get_value (mono_jit_tls_id))
 341                 return; //thread in the process of dettaching
 342
 343         InterlockedIncrement (&profiler_signals_accepted);
 344
 345         hp_save_index = mono_hazard_pointer_save_for_signal_handler ();
 346
 347         mono_thread_info_set_is_async_context (TRUE);
 348         per_thread_profiler_hit (ctx);
 349         mono_thread_info_set_is_async_context (FALSE);
 350
 351         mono_hazard_pointer_restore_for_signal_handler (hp_save_index);
 352         errno = old_errno;
 353
 354         mono_chain_signal (MONO_SIG_HANDLER_PARAMS);
 355 }
 356
 357 #endif
 358
 359 MONO_SIG_HANDLER_FUNC (static, sigquit_signal_handler)
 360 {
 361         gboolean res;
 362
 363         /* We use this signal to start the attach agent too */
 364         res = mono_attach_start ();
 365         if (res)
 366                 return;
 367
 368         mono_threads_request_thread_dump ();
 369
 370         mono_chain_signal (MONO_SIG_HANDLER_PARAMS);
 371 }
 372
 373 MONO_SIG_HANDLER_FUNC (static, sigusr2_signal_handler)
 374 {
 375         gboolean enabled = mono_trace_is_enabled ();
 376
 377         mono_trace_enable (!enabled);
 378
 379         mono_chain_signal (MONO_SIG_HANDLER_PARAMS);
 380 }
 381
 382 static void
 383 add_signal_handler (int signo, gpointer handler, int flags)
 384 {
 385         struct sigaction sa;
 386         struct sigaction previous_sa;
 387
 388 #ifdef MONO_ARCH_USE_SIGACTION
 389         sa.sa_sigaction = (void (*)(int, siginfo_t *, void *))handler;
 390         sigemptyset (&sa.sa_mask);
 391         sa.sa_flags = SA_SIGINFO | flags;
 392 #ifdef MONO_ARCH_SIGSEGV_ON_ALTSTACK
 393
 394 /*Apple likes to deliver SIGBUS for *0 */
 395 #ifdef PLATFORM_MACOSX
 396         if (signo == SIGSEGV || signo == SIGBUS) {
 397 #else
 398         if (signo == SIGSEGV) {
 399 #endif
 400                 sa.sa_flags |= SA_ONSTACK;
 401
 402                 /*
 403                  * libgc will crash when trying to do stack marking for threads which are on
 404                  * an altstack, so delay the suspend signal after the signal handler has
 405                  * executed.
 406                  */
 407                 if (mono_gc_get_suspend_signal () != -1)
 408                         sigaddset (&sa.sa_mask, mono_gc_get_suspend_signal ());
 409         }
 410 #endif
 411         if (signo == SIGSEGV) {
 412                 /*
 413                  * Delay abort signals while handling SIGSEGVs since they could go unnoticed.
 414                  */
 415                 sigset_t block_mask;
 416
 417                 sigemptyset (&block_mask);
 418         }
 419 #else
 420         sa.sa_handler = handler;
 421         sigemptyset (&sa.sa_mask);
 422         sa.sa_flags = flags;
 423 #endif
 424         g_assert (sigaction (signo, &sa, &previous_sa) != -1);
 425
 426         /* if there was already a handler in place for this signal, store it */
 427         if (! (previous_sa.sa_flags & SA_SIGINFO) &&
 428                         (SIG_DFL == previous_sa.sa_handler)) {
 429                 /* it there is no sa_sigaction function and the sa_handler is default, we can safely ignore this */
 430         } else {
 431                 if (mono_do_signal_chaining)
 432                         save_old_signal_handler (signo, &previous_sa);
 433         }
 434 }
 435
 436 static void
 437 remove_signal_handler (int signo)
 438 {
 439         struct sigaction sa;
 440         struct sigaction *saved_action = get_saved_signal_handler (signo);
 441
 442         if (!saved_action) {
 443                 sa.sa_handler = SIG_DFL;
 444                 sigemptyset (&sa.sa_mask);
 445                 sa.sa_flags = 0;
 446
 447                 sigaction (signo, &sa, NULL);
 448         } else {
 449                 g_assert (sigaction (signo, saved_action, NULL) != -1);
 450         }
 451 }
 452
 453 void
 454 mono_runtime_posix_install_handlers (void)
 455 {
 456
 457         sigset_t signal_set;
 458
 459         if (mini_get_debug_options ()->handle_sigint)
 460                 add_signal_handler (SIGINT, mono_sigint_signal_handler, SA_RESTART);
 461
 462         add_signal_handler (SIGFPE, mono_sigfpe_signal_handler, 0);
 463         add_signal_handler (SIGQUIT, sigquit_signal_handler, SA_RESTART);
 464         add_signal_handler (SIGILL, mono_sigill_signal_handler, 0);
 465         add_signal_handler (SIGBUS, mono_sigsegv_signal_handler, 0);
 466         if (mono_jit_trace_calls != NULL)
 467                 add_signal_handler (SIGUSR2, sigusr2_signal_handler, SA_RESTART);
 468
 469         /* it seems to have become a common bug for some programs that run as parents
 470          * of many processes to block signal delivery for real time signals.
 471          * We try to detect and work around their breakage here.
 472          */
 473         sigemptyset (&signal_set);
 474         if (mono_gc_get_suspend_signal () != -1)
 475                 sigaddset (&signal_set, mono_gc_get_suspend_signal ());
 476         if (mono_gc_get_restart_signal () != -1)
 477                 sigaddset (&signal_set, mono_gc_get_restart_signal ());
 478         sigaddset (&signal_set, SIGCHLD);
 479         sigprocmask (SIG_UNBLOCK, &signal_set, NULL);
 480
 481         signal (SIGPIPE, SIG_IGN);
 482
 483         add_signal_handler (SIGABRT, sigabrt_signal_handler, 0);
 484
 485         /* catch SIGSEGV */
 486         add_signal_handler (SIGSEGV, mono_sigsegv_signal_handler, 0);
 487 }
 488
 489 #ifndef PLATFORM_MACOSX
 490 void
 491 mono_runtime_install_handlers (void)
 492 {
 493         mono_runtime_posix_install_handlers ();
 494 }
 495 #endif
 496
 497 void
 498 mono_runtime_cleanup_handlers (void)
 499 {
 500         if (mini_get_debug_options ()->handle_sigint)
 501                 remove_signal_handler (SIGINT);
 502
 503         remove_signal_handler (SIGFPE);
 504         remove_signal_handler (SIGQUIT);
 505         remove_signal_handler (SIGILL);
 506         remove_signal_handler (SIGBUS);
 507         if (mono_jit_trace_calls != NULL)
 508                 remove_signal_handler (SIGUSR2);
 509
 510         remove_signal_handler (SIGABRT);
 511
 512         remove_signal_handler (SIGSEGV);
 513
 514         free_saved_signal_handlers ();
 515 }
 516
 517 #ifdef HAVE_PROFILER_SIGNAL
 518
 519 #ifdef PLATFORM_MACOSX
 520
 521 static clock_serv_t sampling_clock_service;
 522
 523 static void
 524 clock_init (void)
 525 {
 526         kern_return_t ret;
 527
 528         do {
 529                 ret = host_get_clock_service (mach_host_self (), SYSTEM_CLOCK, &sampling_clock_service);
 530         } while (ret == KERN_ABORTED);
 531
 532         if (ret != KERN_SUCCESS)
 533                 g_error ("%s: host_get_clock_service () returned %d", __func__, ret);
 534 }
 535
 536 static void
 537 clock_cleanup (void)
 538 {
 539         kern_return_t ret;
 540
 541         do {
 542                 ret = mach_port_deallocate (mach_task_self (), sampling_clock_service);
 543         } while (ret == KERN_ABORTED);
 544
 545         if (ret != KERN_SUCCESS)
 546                 g_error ("%s: mach_port_deallocate () returned %d", __func__, ret);
 547 }
 548
 549 static guint64
 550 clock_get_time_ns (void)
 551 {
 552         kern_return_t ret;
 553         mach_timespec_t mach_ts;
 554
 555         do {
 556                 ret = clock_get_time (sampling_clock_service, &mach_ts);
 557         } while (ret == KERN_ABORTED);
 558
 559         if (ret != KERN_SUCCESS)
 560                 g_error ("%s: clock_get_time () returned %d", __func__, ret);
 561
 562         return ((guint64) mach_ts.tv_sec * 1000000000) + (guint64) mach_ts.tv_nsec;
 563 }
 564
 565 static void
 566 clock_sleep_ns_abs (guint64 ns_abs)
 567 {
 568         kern_return_t ret;
 569         mach_timespec_t then, remain_unused;
 570
 571         then.tv_sec = ns_abs / 1000000000;
 572         then.tv_nsec = ns_abs % 1000000000;
 573
 574         do {
 575                 ret = clock_sleep (sampling_clock_service, TIME_ABSOLUTE, then, &remain_unused);
 576         } while (ret == KERN_ABORTED);
 577
 578         if (ret != KERN_SUCCESS)
 579                 g_error ("%s: clock_sleep () returned %d", __func__, ret);
 580
 581 }
 582
 583 #else
 584
 585 clockid_t sampling_posix_clock;
 586
 587 static void
 588 clock_init (void)
 589 {
 590         switch (mono_profiler_get_sampling_mode ()) {
 591         case MONO_PROFILER_STAT_MODE_PROCESS:
 592 #ifdef HAVE_CLOCK_NANOSLEEP
 593                 /*
 594                  * If we don't have clock_nanosleep (), measuring the process time
 595                  * makes very little sense as we can only use nanosleep () to sleep on
 596                  * real time.
 597                  */
 598                 sampling_posix_clock = CLOCK_PROCESS_CPUTIME_ID;
 599                 break;
 600 #endif
 601         case MONO_PROFILER_STAT_MODE_REAL: sampling_posix_clock = CLOCK_MONOTONIC; break;
 602         default: g_assert_not_reached (); break;
 603         }
 604 }
 605
 606 static void
 607 clock_cleanup (void)
 608 {
 609 }
 610
 611 static guint64
 612 clock_get_time_ns (void)
 613 {
 614         struct timespec ts;
 615
 616         if (clock_gettime (sampling_posix_clock, &ts) == -1)
 617                 g_error ("%s: clock_gettime () returned -1, errno = %d", __func__, errno);
 618
 619         return ((guint64) ts.tv_sec * 1000000000) + (guint64) ts.tv_nsec;
 620 }
 621
 622 static void
 623 clock_sleep_ns_abs (guint64 ns_abs)
 624 {
 625 #ifdef HAVE_CLOCK_NANOSLEEP
 626         int ret;
 627         struct timespec then;
 628
 629         then.tv_sec = ns_abs / 1000000000;
 630         then.tv_nsec = ns_abs % 1000000000;
 631
 632         do {
 633                 ret = clock_nanosleep (sampling_posix_clock, TIMER_ABSTIME, &then, NULL);
 634
 635                 if (ret != 0 && ret != EINTR)
 636                         g_error ("%s: clock_nanosleep () returned %d", __func__, ret);
 637         } while (ret == EINTR);
 638 #else
 639         int ret;
 640         gint64 diff;
 641         struct timespec req;
 642
 643         /*
 644          * What follows is a crude attempt at emulating clock_nanosleep () on OSs
 645          * which don't provide it (e.g. FreeBSD).
 646          *
 647          * The problem with nanosleep () is that if it is interrupted by a signal,
 648          * time will drift as a result of having to restart the call after the
 649          * signal handler has finished. For this reason, we avoid using the rem
 650          * argument of nanosleep (). Instead, before every nanosleep () call, we
 651          * check if enough time has passed to satisfy the sleep request. If yes, we
 652          * simply return. If not, we calculate the difference and do another sleep.
 653          *
 654          * This should reduce the amount of drift that happens because we account
 655          * for the time spent executing the signal handler, which nanosleep () is
 656          * not guaranteed to do for the rem argument.
 657          *
 658          * The downside to this approach is that it is slightly expensive: We have
 659          * to make an extra system call to retrieve the current time whenever we're
 660          * going to restart a nanosleep () call. This is unlikely to be a problem
 661          * in practice since the sampling thread won't be receiving many signals in
 662          * the first place (it's a tools thread, so no STW), and because typical
 663          * sleep periods for the thread are many orders of magnitude bigger than
 664          * the time it takes to actually perform that system call (just a few
 665          * nanoseconds).
 666          */
 667         do {
 668                 diff = (gint64) ns_abs - (gint64) clock_get_time_ns ();
 669
 670                 if (diff <= 0)
 671                         break;
 672
 673                 req.tv_sec = diff / 1000000000;
 674                 req.tv_nsec = diff % 1000000000;
 675
 676                 if ((ret = nanosleep (&req, NULL)) == -1 && errno != EINTR)
 677                         g_error ("%s: nanosleep () returned -1, errno = %d", __func__, errno);
 678         } while (ret == -1);
 679 #endif
 680 }
 681
 682 #endif
 683
 684 static int profiler_signal;
 685 static MonoNativeThreadId sampling_thread;
 686 static volatile gint32 sampling_thread_running;
 687
 688 static mono_native_thread_return_t
 689 sampling_thread_func (void *data)
 690 {
 691         mono_threads_attach_tools_thread ();
 692         mono_thread_info_set_name (mono_native_thread_id_get (), "Profiler sampler");
 693
 694         gint64 rate = 1000000000 / mono_profiler_get_sampling_rate ();
 695
 696         int old_policy;
 697         struct sched_param old_sched;
 698         pthread_getschedparam (pthread_self (), &old_policy, &old_sched);
 699
 700         /*
 701          * Attempt to switch the thread to real time scheduling. This will not
 702          * necessarily work on all OSs; for example, most Linux systems will give
 703          * us EPERM here unless configured to allow this.
 704          *
 705          * TODO: This does not work on Mac (and maybe some other OSs). On Mac, we
 706          * have to use the Mach thread policy routines to switch to real-time
 707          * scheduling. This is quite tricky as we need to specify how often we'll
 708          * be doing work (easy), the normal processing time needed (also easy),
 709          * and the maximum amount of processing time needed (hard). This is
 710          * further complicated by the fact that if we misbehave and take too long
 711          * to do our work, the kernel may knock us back down to the normal thread
 712          * scheduling policy without telling us.
 713          */
 714         struct sched_param sched = { .sched_priority = sched_get_priority_max (SCHED_FIFO) };
 715         pthread_setschedparam (pthread_self (), SCHED_FIFO, &sched);
 716
 717         clock_init ();
 718
 719         guint64 sleep = clock_get_time_ns ();
 720
 721         while (InterlockedRead (&sampling_thread_running)) {
 722                 sleep += rate;
 723
 724                 FOREACH_THREAD_SAFE (info) {
 725                         /* info should never be this thread as we're a tools thread. */
 726                         g_assert (mono_thread_info_get_tid (info) != mono_native_thread_id_get ());
 727
 728                         mono_threads_pthread_kill (info, profiler_signal);
 729                         InterlockedIncrement (&profiler_signals_sent);
 730                 } FOREACH_THREAD_SAFE_END
 731
 732                 clock_sleep_ns_abs (sleep);
 733         }
 734
 735         clock_cleanup ();
 736
 737         pthread_setschedparam (pthread_self (), old_policy, &old_sched);
 738
 739         mono_thread_info_detach ();
 740
 741         return NULL;
 742 }
 743
 744 void
 745 mono_runtime_shutdown_stat_profiler (void)
 746 {
 747         InterlockedWrite (&sampling_thread_running, 0);
 748         pthread_join (sampling_thread, NULL);
 749
 750         /*
 751          * We can't safely remove the signal handler because we have no guarantee
 752          * that all pending signals have been delivered at this point. This should
 753          * not really be a problem anyway.
 754          */
 755         //remove_signal_handler (profiler_signal);
 756 }
 757
 758 void
 759 mono_runtime_setup_stat_profiler (void)
 760 {
 761         /*
 762          * Use a real-time signal when possible. This gives us roughly a 99% signal
 763          * delivery rate in all cases. On the other hand, using a regular signal
 764          * tends to result in awful delivery rates when the application is heavily
 765          * loaded.
 766          *
 767          * TODO: On Mac, we should explore using the Mach thread suspend/resume
 768          * functions and doing the stack walk from the sampling thread. This would
 769          * get us a 100% sampling rate. However, this may interfere with the GC's
 770          * STW logic. Could perhaps be solved by taking the suspend lock.
 771          */
 772 #if defined (USE_POSIX_BACKEND) && defined (SIGRTMIN)
 773         /* Just take the first real-time signal we can get. */
 774         profiler_signal = mono_threads_posix_signal_search_alternative (-1);
 775 #else
 776         profiler_signal = SIGPROF;
 777 #endif
 778
 779         add_signal_handler (profiler_signal, profiler_signal_handler, SA_RESTART);
 780
 781         mono_counters_register ("Sampling signals sent", MONO_COUNTER_UINT | MONO_COUNTER_PROFILER | MONO_COUNTER_MONOTONIC, &profiler_signals_sent);
 782         mono_counters_register ("Sampling signals received", MONO_COUNTER_UINT | MONO_COUNTER_PROFILER | MONO_COUNTER_MONOTONIC, &profiler_signals_received);
 783         mono_counters_register ("Sampling signals accepted", MONO_COUNTER_UINT | MONO_COUNTER_PROFILER | MONO_COUNTER_MONOTONIC, &profiler_signals_accepted);
 784
 785         InterlockedWrite (&sampling_thread_running, 1);
 786         mono_native_thread_create (&sampling_thread, sampling_thread_func, NULL);
 787 }
 788
 789 #else
 790
 791 void
 792 mono_runtime_shutdown_stat_profiler (void)
 793 {
 794 }
 795
 796 void
 797 mono_runtime_setup_stat_profiler (void)
 798 {
 799 }
 800
 801 #endif
 802
 803 #if !defined(PLATFORM_MACOSX)
 804 pid_t
 805 mono_runtime_syscall_fork ()
 806 {
 807 #if defined(PLATFORM_ANDROID)
 808         /* SYS_fork is defined to be __NR_fork which is not defined in some ndk versions */
 809         g_assert_not_reached ();
 810         return 0;
 811 #elif defined(SYS_fork)
 812         return (pid_t) syscall (SYS_fork);
 813 #else
 814         g_assert_not_reached ();
 815         return 0;
 816 #endif
 817 }
 818
 819 void
 820 mono_gdb_render_native_backtraces (pid_t crashed_pid)
 821 {
 822         const char *argv [9];
 823         char template_ [] = "/tmp/mono-lldb-commands.XXXXXX";
 824         char buf1 [128];
 825         FILE *commands;
 826         gboolean using_lldb = FALSE;
 827
 828         argv [0] = g_find_program_in_path ("gdb");
 829         if (argv [0] == NULL) {
 830                 argv [0] = g_find_program_in_path ("lldb");
 831                 using_lldb = TRUE;
 832         }
 833
 834         if (argv [0] == NULL)
 835                 return;
 836
 837         if (using_lldb) {
 838                 if (mkstemp (template_) == -1)
 839                         return;
 840
 841                 commands = fopen (template_, "w");
 842
 843                 fprintf (commands, "process attach --pid %ld\n", (long) crashed_pid);
 844                 fprintf (commands, "thread list\n");
 845                 fprintf (commands, "thread backtrace all\n");
 846                 fprintf (commands, "detach\n");
 847                 fprintf (commands, "quit\n");
 848
 849                 fflush (commands);
 850                 fclose (commands);
 851
 852                 argv [1] = "--source";
 853                 argv [2] = template_;
 854                 argv [3] = 0;
 855         } else {
 856                 argv [1] = "-ex";
 857                 sprintf (buf1, "attach %ld", (long) crashed_pid);
 858                 argv [2] = buf1;
 859                 argv [3] = "--ex";
 860                 argv [4] = "info threads";
 861                 argv [5] = "--ex";
 862                 argv [6] = "thread apply all bt";
 863                 argv [7] = "--batch";
 864                 argv [8] = 0;
 865         }
 866
 867         execv (argv [0], (char**)argv);
 868
 869         if (using_lldb)
 870                 unlink (template_);
 871 }
 872 #endif
 873 #endif /* __native_client__ */
 874
 875 #if !defined (__MACH__)
 876
 877 gboolean
 878 mono_thread_state_init_from_handle (MonoThreadUnwindState *tctx, MonoThreadInfo *info)
 879 {
 880         g_error ("Posix systems don't support mono_thread_state_init_from_handle");
 881         return FALSE;
 882 }
 883
 884 #endif