libsanitizer/asan/asan_rtl.cc

   1 //===-- asan_rtl.cc -------------------------------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file is a part of AddressSanitizer, an address sanity checker.
   9 //
  10 // Main file of the ASan run-time library.
  11 //===----------------------------------------------------------------------===//
  12 #include "asan_allocator.h"
  13 #include "asan_interceptors.h"
  14 #include "asan_internal.h"
  15 #include "asan_mapping.h"
  16 #include "asan_report.h"
  17 #include "asan_stack.h"
  18 #include "asan_stats.h"
  19 #include "asan_thread.h"
  20 #include "asan_thread_registry.h"
  21 #include "sanitizer_common/sanitizer_atomic.h"
  22 #include "sanitizer_common/sanitizer_flags.h"
  23 #include "sanitizer_common/sanitizer_libc.h"
  24 #include "sanitizer_common/sanitizer_symbolizer.h"
  25
  26 namespace __asan {
  27
  28 uptr AsanMappingProfile[kAsanMappingProfileSize];
  29
  30 static void AsanDie() {
  31   static atomic_uint32_t num_calls;
  32   if (atomic_fetch_add(&num_calls, 1, memory_order_relaxed) != 0) {
  33     // Don't die twice - run a busy loop.
  34     while (1) { }
  35   }
  36   if (flags()->sleep_before_dying) {
  37     Report("Sleeping for %d second(s)\n", flags()->sleep_before_dying);
  38     SleepForSeconds(flags()->sleep_before_dying);
  39   }
  40   if (flags()->unmap_shadow_on_exit) {
  41     if (kMidMemBeg) {
  42       UnmapOrDie((void*)kLowShadowBeg, kMidMemBeg - kLowShadowBeg);
  43       UnmapOrDie((void*)kMidMemEnd, kHighShadowEnd - kMidMemEnd);
  44     } else {
  45       UnmapOrDie((void*)kLowShadowBeg, kHighShadowEnd - kLowShadowBeg);
  46     }
  47   }
  48   if (death_callback)
  49     death_callback();
  50   if (flags()->abort_on_error)
  51     Abort();
  52   internal__exit(flags()->exitcode);
  53 }
  54
  55 static void AsanCheckFailed(const char *file, int line, const char *cond,
  56                             u64 v1, u64 v2) {
  57   Report("AddressSanitizer CHECK failed: %s:%d \"%s\" (0x%zx, 0x%zx)\n",
  58              file, line, cond, (uptr)v1, (uptr)v2);
  59   // FIXME: check for infinite recursion without a thread-local counter here.
  60   PRINT_CURRENT_STACK();
  61   Die();
  62 }
  63
  64 // -------------------------- Flags ------------------------- {{{1
  65 static const int kDeafultMallocContextSize = 30;
  66
  67 static Flags asan_flags;
  68
  69 Flags *flags() {
  70   return &asan_flags;
  71 }
  72
  73 static const char *MaybeCallAsanDefaultOptions() {
  74   return (&__asan_default_options) ? __asan_default_options() : "";
  75 }
  76
  77 static const char *MaybeUseAsanDefaultOptionsCompileDefiniton() {
  78 #ifdef ASAN_DEFAULT_OPTIONS
  79 // Stringize the macro value.
  80 # define ASAN_STRINGIZE(x) #x
  81 # define ASAN_STRINGIZE_OPTIONS(options) ASAN_STRINGIZE(options)
  82   return ASAN_STRINGIZE_OPTIONS(ASAN_DEFAULT_OPTIONS);
  83 #else
  84   return "";
  85 #endif
  86 }
  87
  88 static void ParseFlagsFromString(Flags *f, const char *str) {
  89   ParseFlag(str, &f->quarantine_size, "quarantine_size");
  90   ParseFlag(str, &f->symbolize, "symbolize");
  91   ParseFlag(str, &f->verbosity, "verbosity");
  92   ParseFlag(str, &f->redzone, "redzone");
  93   CHECK(f->redzone >= 16);
  94   CHECK(IsPowerOfTwo(f->redzone));
  95
  96   ParseFlag(str, &f->debug, "debug");
  97   ParseFlag(str, &f->report_globals, "report_globals");
  98   ParseFlag(str, &f->check_initialization_order, "initialization_order");
  99   ParseFlag(str, &f->malloc_context_size, "malloc_context_size");
 100   CHECK((uptr)f->malloc_context_size <= kStackTraceMax);
 101
 102   ParseFlag(str, &f->replace_str, "replace_str");
 103   ParseFlag(str, &f->replace_intrin, "replace_intrin");
 104   ParseFlag(str, &f->mac_ignore_invalid_free, "mac_ignore_invalid_free");
 105   ParseFlag(str, &f->use_fake_stack, "use_fake_stack");
 106   ParseFlag(str, &f->max_malloc_fill_size, "max_malloc_fill_size");
 107   ParseFlag(str, &f->exitcode, "exitcode");
 108   ParseFlag(str, &f->allow_user_poisoning, "allow_user_poisoning");
 109   ParseFlag(str, &f->sleep_before_dying, "sleep_before_dying");
 110   ParseFlag(str, &f->handle_segv, "handle_segv");
 111   ParseFlag(str, &f->use_sigaltstack, "use_sigaltstack");
 112   ParseFlag(str, &f->check_malloc_usable_size, "check_malloc_usable_size");
 113   ParseFlag(str, &f->unmap_shadow_on_exit, "unmap_shadow_on_exit");
 114   ParseFlag(str, &f->abort_on_error, "abort_on_error");
 115   ParseFlag(str, &f->print_stats, "print_stats");
 116   ParseFlag(str, &f->print_legend, "print_legend");
 117   ParseFlag(str, &f->atexit, "atexit");
 118   ParseFlag(str, &f->disable_core, "disable_core");
 119   ParseFlag(str, &f->strip_path_prefix, "strip_path_prefix");
 120   ParseFlag(str, &f->allow_reexec, "allow_reexec");
 121   ParseFlag(str, &f->print_full_thread_history, "print_full_thread_history");
 122   ParseFlag(str, &f->log_path, "log_path");
 123   ParseFlag(str, &f->fast_unwind_on_fatal, "fast_unwind_on_fatal");
 124   ParseFlag(str, &f->fast_unwind_on_malloc, "fast_unwind_on_malloc");
 125   ParseFlag(str, &f->poison_heap, "poison_heap");
 126   ParseFlag(str, &f->alloc_dealloc_mismatch, "alloc_dealloc_mismatch");
 127   ParseFlag(str, &f->use_stack_depot, "use_stack_depot");
 128 }
 129
 130 void InitializeFlags(Flags *f, const char *env) {
 131   internal_memset(f, 0, sizeof(*f));
 132
 133   f->quarantine_size = (ASAN_LOW_MEMORY) ? 1UL << 26 : 1UL << 28;
 134   f->symbolize = false;
 135   f->verbosity = 0;
 136   f->redzone = ASAN_ALLOCATOR_VERSION == 2 ? 16 : (ASAN_LOW_MEMORY) ? 64 : 128;
 137   f->debug = false;
 138   f->report_globals = 1;
 139   f->check_initialization_order = true;
 140   f->malloc_context_size = kDeafultMallocContextSize;
 141   f->replace_str = true;
 142   f->replace_intrin = true;
 143   f->mac_ignore_invalid_free = false;
 144   f->use_fake_stack = true;
 145   f->max_malloc_fill_size = 0;
 146   f->exitcode = ASAN_DEFAULT_FAILURE_EXITCODE;
 147   f->allow_user_poisoning = true;
 148   f->sleep_before_dying = 0;
 149   f->handle_segv = ASAN_NEEDS_SEGV;
 150   f->use_sigaltstack = false;
 151   f->check_malloc_usable_size = true;
 152   f->unmap_shadow_on_exit = false;
 153   f->abort_on_error = false;
 154   f->print_stats = false;
 155   f->print_legend = true;
 156   f->atexit = false;
 157   f->disable_core = (SANITIZER_WORDSIZE == 64);
 158   f->strip_path_prefix = "";
 159   f->allow_reexec = true;
 160   f->print_full_thread_history = true;
 161   f->log_path = 0;
 162   f->fast_unwind_on_fatal = false;
 163   f->fast_unwind_on_malloc = true;
 164   f->poison_heap = true;
 165   f->alloc_dealloc_mismatch = true;
 166   f->use_stack_depot = true;  // Only affects allocator2.
 167
 168   // Override from compile definition.
 169   ParseFlagsFromString(f, MaybeUseAsanDefaultOptionsCompileDefiniton());
 170
 171   // Override from user-specified string.
 172   ParseFlagsFromString(f, MaybeCallAsanDefaultOptions());
 173   if (flags()->verbosity) {
 174     Report("Using the defaults from __asan_default_options: %s\n",
 175            MaybeCallAsanDefaultOptions());
 176   }
 177
 178   // Override from command line.
 179   ParseFlagsFromString(f, env);
 180 }
 181
 182 // -------------------------- Globals --------------------- {{{1
 183 int asan_inited;
 184 bool asan_init_is_running;
 185 void (*death_callback)(void);
 186
 187 #if !ASAN_FIXED_MAPPING
 188 uptr kHighMemEnd, kMidMemBeg, kMidMemEnd;
 189 #endif
 190
 191 // -------------------------- Misc ---------------- {{{1
 192 void ShowStatsAndAbort() {
 193   __asan_print_accumulated_stats();
 194   Die();
 195 }
 196
 197 // ---------------------- mmap -------------------- {{{1
 198 // Reserve memory range [beg, end].
 199 static void ReserveShadowMemoryRange(uptr beg, uptr end) {
 200   CHECK((beg % GetPageSizeCached()) == 0);
 201   CHECK(((end + 1) % GetPageSizeCached()) == 0);
 202   uptr size = end - beg + 1;
 203   void *res = MmapFixedNoReserve(beg, size);
 204   if (res != (void*)beg) {
 205     Report("ReserveShadowMemoryRange failed while trying to map 0x%zx bytes. "
 206            "Perhaps you're using ulimit -v\n", size);
 207     Abort();
 208   }
 209 }
 210
 211 // --------------- LowLevelAllocateCallbac ---------- {{{1
 212 static void OnLowLevelAllocate(uptr ptr, uptr size) {
 213   PoisonShadow(ptr, size, kAsanInternalHeapMagic);
 214 }
 215
 216 // -------------------------- Run-time entry ------------------- {{{1
 217 // exported functions
 218 #define ASAN_REPORT_ERROR(type, is_write, size)                     \
 219 extern "C" NOINLINE INTERFACE_ATTRIBUTE                        \
 220 void __asan_report_ ## type ## size(uptr addr);                \
 221 void __asan_report_ ## type ## size(uptr addr) {               \
 222   GET_CALLER_PC_BP_SP;                                              \
 223   __asan_report_error(pc, bp, sp, addr, is_write, size);            \
 224 }
 225
 226 ASAN_REPORT_ERROR(load, false, 1)
 227 ASAN_REPORT_ERROR(load, false, 2)
 228 ASAN_REPORT_ERROR(load, false, 4)
 229 ASAN_REPORT_ERROR(load, false, 8)
 230 ASAN_REPORT_ERROR(load, false, 16)
 231 ASAN_REPORT_ERROR(store, true, 1)
 232 ASAN_REPORT_ERROR(store, true, 2)
 233 ASAN_REPORT_ERROR(store, true, 4)
 234 ASAN_REPORT_ERROR(store, true, 8)
 235 ASAN_REPORT_ERROR(store, true, 16)
 236
 237 #define ASAN_REPORT_ERROR_N(type, is_write)                    \
 238 extern "C" NOINLINE INTERFACE_ATTRIBUTE                        \
 239 void __asan_report_ ## type ## _n(uptr addr, uptr size);       \
 240 void __asan_report_ ## type ## _n(uptr addr, uptr size) {      \
 241   GET_CALLER_PC_BP_SP;                                         \
 242   __asan_report_error(pc, bp, sp, addr, is_write, size);       \
 243 }
 244
 245 ASAN_REPORT_ERROR_N(load, false)
 246 ASAN_REPORT_ERROR_N(store, true)
 247
 248 // Force the linker to keep the symbols for various ASan interface functions.
 249 // We want to keep those in the executable in order to let the instrumented
 250 // dynamic libraries access the symbol even if it is not used by the executable
 251 // itself. This should help if the build system is removing dead code at link
 252 // time.
 253 static NOINLINE void force_interface_symbols() {
 254   volatile int fake_condition = 0;  // prevent dead condition elimination.
 255   // __asan_report_* functions are noreturn, so we need a switch to prevent
 256   // the compiler from removing any of them.
 257   switch (fake_condition) {
 258     case 1: __asan_report_load1(0); break;
 259     case 2: __asan_report_load2(0); break;
 260     case 3: __asan_report_load4(0); break;
 261     case 4: __asan_report_load8(0); break;
 262     case 5: __asan_report_load16(0); break;
 263     case 6: __asan_report_store1(0); break;
 264     case 7: __asan_report_store2(0); break;
 265     case 8: __asan_report_store4(0); break;
 266     case 9: __asan_report_store8(0); break;
 267     case 10: __asan_report_store16(0); break;
 268     case 12: __asan_register_globals(0, 0); break;
 269     case 13: __asan_unregister_globals(0, 0); break;
 270     case 14: __asan_set_death_callback(0); break;
 271     case 15: __asan_set_error_report_callback(0); break;
 272     case 16: __asan_handle_no_return(); break;
 273     case 17: __asan_address_is_poisoned(0); break;
 274     case 18: __asan_get_allocated_size(0); break;
 275     case 19: __asan_get_current_allocated_bytes(); break;
 276     case 20: __asan_get_estimated_allocated_size(0); break;
 277     case 21: __asan_get_free_bytes(); break;
 278     case 22: __asan_get_heap_size(); break;
 279     case 23: __asan_get_ownership(0); break;
 280     case 24: __asan_get_unmapped_bytes(); break;
 281     case 25: __asan_poison_memory_region(0, 0); break;
 282     case 26: __asan_unpoison_memory_region(0, 0); break;
 283     case 27: __asan_set_error_exit_code(0); break;
 284     case 28: __asan_stack_free(0, 0, 0); break;
 285     case 29: __asan_stack_malloc(0, 0); break;
 286     case 30: __asan_before_dynamic_init(0, 0); break;
 287     case 31: __asan_after_dynamic_init(); break;
 288     case 32: __asan_poison_stack_memory(0, 0); break;
 289     case 33: __asan_unpoison_stack_memory(0, 0); break;
 290     case 34: __asan_region_is_poisoned(0, 0); break;
 291     case 35: __asan_describe_address(0); break;
 292   }
 293 }
 294
 295 static void asan_atexit() {
 296   Printf("AddressSanitizer exit stats:\n");
 297   __asan_print_accumulated_stats();
 298   // Print AsanMappingProfile.
 299   for (uptr i = 0; i < kAsanMappingProfileSize; i++) {
 300     if (AsanMappingProfile[i] == 0) continue;
 301     Printf("asan_mapping.h:%zd -- %zd\n", i, AsanMappingProfile[i]);
 302   }
 303 }
 304
 305 static void InitializeHighMemEnd() {
 306 #if !ASAN_FIXED_MAPPING
 307 #if SANITIZER_WORDSIZE == 64
 308 # if defined(__powerpc64__)
 309   // FIXME:
 310   // On PowerPC64 we have two different address space layouts: 44- and 46-bit.
 311   // We somehow need to figure our which one we are using now and choose
 312   // one of 0x00000fffffffffffUL and 0x00003fffffffffffUL.
 313   // Note that with 'ulimit -s unlimited' the stack is moved away from the top
 314   // of the address space, so simply checking the stack address is not enough.
 315   kHighMemEnd = (1ULL << 44) - 1;  // 0x00000fffffffffffUL
 316 # else
 317   kHighMemEnd = (1ULL << 47) - 1;  // 0x00007fffffffffffUL;
 318 # endif
 319 #else  // SANITIZER_WORDSIZE == 32
 320   kHighMemEnd = (1ULL << 32) - 1;  // 0xffffffff;
 321 #endif  // SANITIZER_WORDSIZE
 322 #endif  // !ASAN_FIXED_MAPPING
 323 }
 324
 325 static void ProtectGap(uptr a, uptr size) {
 326   CHECK_EQ(a, (uptr)Mprotect(a, size));
 327 }
 328
 329 static void PrintAddressSpaceLayout() {
 330   Printf("|| `[%p, %p]` || HighMem    ||\n",
 331          (void*)kHighMemBeg, (void*)kHighMemEnd);
 332   Printf("|| `[%p, %p]` || HighShadow ||\n",
 333          (void*)kHighShadowBeg, (void*)kHighShadowEnd);
 334   if (kMidMemBeg) {
 335     Printf("|| `[%p, %p]` || ShadowGap3 ||\n",
 336            (void*)kShadowGap3Beg, (void*)kShadowGap3End);
 337     Printf("|| `[%p, %p]` || MidMem     ||\n",
 338            (void*)kMidMemBeg, (void*)kMidMemEnd);
 339     Printf("|| `[%p, %p]` || ShadowGap2 ||\n",
 340            (void*)kShadowGap2Beg, (void*)kShadowGap2End);
 341     Printf("|| `[%p, %p]` || MidShadow  ||\n",
 342            (void*)kMidShadowBeg, (void*)kMidShadowEnd);
 343   }
 344   Printf("|| `[%p, %p]` || ShadowGap  ||\n",
 345          (void*)kShadowGapBeg, (void*)kShadowGapEnd);
 346   if (kLowShadowBeg) {
 347     Printf("|| `[%p, %p]` || LowShadow  ||\n",
 348            (void*)kLowShadowBeg, (void*)kLowShadowEnd);
 349     Printf("|| `[%p, %p]` || LowMem     ||\n",
 350            (void*)kLowMemBeg, (void*)kLowMemEnd);
 351   }
 352   Printf("MemToShadow(shadow): %p %p %p %p",
 353          (void*)MEM_TO_SHADOW(kLowShadowBeg),
 354          (void*)MEM_TO_SHADOW(kLowShadowEnd),
 355          (void*)MEM_TO_SHADOW(kHighShadowBeg),
 356          (void*)MEM_TO_SHADOW(kHighShadowEnd));
 357   if (kMidMemBeg) {
 358     Printf(" %p %p",
 359            (void*)MEM_TO_SHADOW(kMidShadowBeg),
 360            (void*)MEM_TO_SHADOW(kMidShadowEnd));
 361   }
 362   Printf("\n");
 363   Printf("red_zone=%zu\n", (uptr)flags()->redzone);
 364   Printf("malloc_context_size=%zu\n", (uptr)flags()->malloc_context_size);
 365
 366   Printf("SHADOW_SCALE: %zx\n", (uptr)SHADOW_SCALE);
 367   Printf("SHADOW_GRANULARITY: %zx\n", (uptr)SHADOW_GRANULARITY);
 368   Printf("SHADOW_OFFSET: %zx\n", (uptr)SHADOW_OFFSET);
 369   CHECK(SHADOW_SCALE >= 3 && SHADOW_SCALE <= 7);
 370   if (kMidMemBeg)
 371     CHECK(kMidShadowBeg > kLowShadowEnd &&
 372           kMidMemBeg > kMidShadowEnd &&
 373           kHighShadowBeg > kMidMemEnd);
 374 }
 375
 376 }  // namespace __asan
 377
 378 // ---------------------- Interface ---------------- {{{1
 379 using namespace __asan;  // NOLINT
 380
 381 #if !SANITIZER_SUPPORTS_WEAK_HOOKS
 382 extern "C" {
 383 SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
 384 const char* __asan_default_options() { return ""; }
 385 }  // extern "C"
 386 #endif
 387
 388 int NOINLINE __asan_set_error_exit_code(int exit_code) {
 389   int old = flags()->exitcode;
 390   flags()->exitcode = exit_code;
 391   return old;
 392 }
 393
 394 void NOINLINE __asan_handle_no_return() {
 395   int local_stack;
 396   AsanThread *curr_thread = asanThreadRegistry().GetCurrent();
 397   CHECK(curr_thread);
 398   uptr PageSize = GetPageSizeCached();
 399   uptr top = curr_thread->stack_top();
 400   uptr bottom = ((uptr)&local_stack - PageSize) & ~(PageSize-1);
 401   PoisonShadow(bottom, top - bottom, 0);
 402 }
 403
 404 void NOINLINE __asan_set_death_callback(void (*callback)(void)) {
 405   death_callback = callback;
 406 }
 407
 408 void __asan_init() {
 409   if (asan_inited) return;
 410   SanitizerToolName = "AddressSanitizer";
 411   CHECK(!asan_init_is_running && "ASan init calls itself!");
 412   asan_init_is_running = true;
 413   InitializeHighMemEnd();
 414
 415   // Make sure we are not statically linked.
 416   AsanDoesNotSupportStaticLinkage();
 417
 418   // Install tool-specific callbacks in sanitizer_common.
 419   SetDieCallback(AsanDie);
 420   SetCheckFailedCallback(AsanCheckFailed);
 421   SetPrintfAndReportCallback(AppendToErrorMessageBuffer);
 422
 423   // Initialize flags. This must be done early, because most of the
 424   // initialization steps look at flags().
 425   const char *options = GetEnv("ASAN_OPTIONS");
 426   InitializeFlags(flags(), options);
 427   __sanitizer_set_report_path(flags()->log_path);
 428
 429   if (flags()->verbosity && options) {
 430     Report("Parsed ASAN_OPTIONS: %s\n", options);
 431   }
 432
 433   // Re-exec ourselves if we need to set additional env or command line args.
 434   MaybeReexec();
 435
 436   // Setup internal allocator callback.
 437   SetLowLevelAllocateCallback(OnLowLevelAllocate);
 438
 439   if (flags()->atexit) {
 440     Atexit(asan_atexit);
 441   }
 442
 443   // interceptors
 444   InitializeAsanInterceptors();
 445
 446   ReplaceSystemMalloc();
 447   ReplaceOperatorsNewAndDelete();
 448
 449   uptr shadow_start = kLowShadowBeg;
 450   if (kLowShadowBeg) shadow_start -= GetMmapGranularity();
 451   uptr shadow_end = kHighShadowEnd;
 452   bool full_shadow_is_available =
 453       MemoryRangeIsAvailable(shadow_start, shadow_end);
 454
 455 #if ASAN_LINUX && defined(__x86_64__) && !ASAN_FIXED_MAPPING
 456   if (!full_shadow_is_available) {
 457     kMidMemBeg = kLowMemEnd < 0x3000000000ULL ? 0x3000000000ULL : 0;
 458     kMidMemEnd = kLowMemEnd < 0x3000000000ULL ? 0x3fffffffffULL : 0;
 459   }
 460 #endif
 461
 462   if (flags()->verbosity)
 463     PrintAddressSpaceLayout();
 464
 465   if (flags()->disable_core) {
 466     DisableCoreDumper();
 467   }
 468
 469   if (full_shadow_is_available) {
 470     // mmap the low shadow plus at least one page at the left.
 471     if (kLowShadowBeg)
 472       ReserveShadowMemoryRange(shadow_start, kLowShadowEnd);
 473     // mmap the high shadow.
 474     ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd);
 475     // protect the gap.
 476     ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
 477   } else if (kMidMemBeg &&
 478       MemoryRangeIsAvailable(shadow_start, kMidMemBeg - 1) &&
 479       MemoryRangeIsAvailable(kMidMemEnd + 1, shadow_end)) {
 480     CHECK(kLowShadowBeg != kLowShadowEnd);
 481     // mmap the low shadow plus at least one page at the left.
 482     ReserveShadowMemoryRange(shadow_start, kLowShadowEnd);
 483     // mmap the mid shadow.
 484     ReserveShadowMemoryRange(kMidShadowBeg, kMidShadowEnd);
 485     // mmap the high shadow.
 486     ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd);
 487     // protect the gaps.
 488     ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
 489     ProtectGap(kShadowGap2Beg, kShadowGap2End - kShadowGap2Beg + 1);
 490     ProtectGap(kShadowGap3Beg, kShadowGap3End - kShadowGap3Beg + 1);
 491   } else {
 492     Report("Shadow memory range interleaves with an existing memory mapping. "
 493            "ASan cannot proceed correctly. ABORTING.\n");
 494     DumpProcessMap();
 495     Die();
 496   }
 497
 498   InstallSignalHandlers();
 499   // Start symbolizer process if necessary.
 500   if (flags()->symbolize) {
 501     const char *external_symbolizer = GetEnv("ASAN_SYMBOLIZER_PATH");
 502     if (external_symbolizer) {
 503       InitializeExternalSymbolizer(external_symbolizer);
 504     }
 505   }
 506
 507   // On Linux AsanThread::ThreadStart() calls malloc() that's why asan_inited
 508   // should be set to 1 prior to initializing the threads.
 509   asan_inited = 1;
 510   asan_init_is_running = false;
 511
 512   asanThreadRegistry().Init();
 513   asanThreadRegistry().GetMain()->ThreadStart();
 514   force_interface_symbols();  // no-op.
 515
 516   InitializeAllocator();
 517
 518   if (flags()->verbosity) {
 519     Report("AddressSanitizer Init done\n");
 520   }
 521 }
 522
 523 #if ASAN_USE_PREINIT_ARRAY
 524   // On Linux, we force __asan_init to be called before anyone else
 525   // by placing it into .preinit_array section.
 526   // FIXME: do we have anything like this on Mac?
 527   __attribute__((section(".preinit_array")))
 528   void (*__asan_preinit)(void) =__asan_init;
 529 #elif defined(_WIN32) && defined(_DLL)
 530   // On Windows, when using dynamic CRT (/MD), we can put a pointer
 531   // to __asan_init into the global list of C initializers.
 532   // See crt0dat.c in the CRT sources for the details.
 533   #pragma section(".CRT$XIB", long, read)  // NOLINT
 534   __declspec(allocate(".CRT$XIB")) void (*__asan_preinit)() = __asan_init;
 535 #endif