asan_rtl.cc revision fca72fd2741372d2e947366277258bff1092e73e
1//===-- asan_rtl.cc ---------------------------------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file is a part of AddressSanitizer, an address sanity checker. 11// 12// Main file of the ASan run-time library. 13//===----------------------------------------------------------------------===// 14#include "asan_allocator.h" 15#include "asan_interceptors.h" 16#include "asan_interface.h" 17#include "asan_internal.h" 18#include "asan_lock.h" 19#include "asan_mapping.h" 20#include "asan_stack.h" 21#include "asan_stats.h" 22#include "asan_thread.h" 23#include "asan_thread_registry.h" 24 25namespace __asan { 26 27// -------------------------- Flags ------------------------- {{{1 28static const size_t kMallocContextSize = 30; 29static int FLAG_atexit; 30 31size_t FLAG_redzone; // power of two, >= 32 32size_t FLAG_quarantine_size; 33int FLAG_demangle; 34bool FLAG_symbolize; 35int FLAG_v; 36int FLAG_debug; 37bool FLAG_poison_shadow; 38int FLAG_report_globals; 39size_t FLAG_malloc_context_size = kMallocContextSize; 40uintptr_t FLAG_large_malloc; 41bool FLAG_handle_segv; 42bool FLAG_use_sigaltstack; 43bool FLAG_replace_str; 44bool FLAG_replace_intrin; 45bool FLAG_replace_cfallocator; // Used on Mac only. 46size_t FLAG_max_malloc_fill_size = 0; 47bool FLAG_use_fake_stack; 48bool FLAG_abort_on_error; 49int FLAG_exitcode = ASAN_DEFAULT_FAILURE_EXITCODE; 50bool FLAG_allow_user_poisoning; 51int FLAG_sleep_before_dying; 52bool FLAG_unmap_shadow_on_exit; 53bool FLAG_disable_core; 54bool FLAG_check_malloc_usable_size; 55 56// -------------------------- Globals --------------------- {{{1 57int asan_inited; 58bool asan_init_is_running; 59static void (*death_callback)(void); 60static void (*error_report_callback)(const char*); 61char *error_message_buffer = NULL; 62size_t error_message_buffer_pos = 0; 63size_t error_message_buffer_size = 0; 64 65// -------------------------- Misc ---------------- {{{1 66void ShowStatsAndAbort() { 67 __asan_print_accumulated_stats(); 68 AsanDie(); 69} 70 71static void PrintBytes(const char *before, uintptr_t *a) { 72 uint8_t *bytes = (uint8_t*)a; 73 size_t byte_num = (__WORDSIZE) / 8; 74 Printf("%s%p:", before, (void*)a); 75 for (size_t i = 0; i < byte_num; i++) { 76 Printf(" %x%x", bytes[i] >> 4, bytes[i] & 15); 77 } 78 Printf("\n"); 79} 80 81size_t ReadFileToBuffer(const char *file_name, char **buff, 82 size_t *buff_size, size_t max_len) { 83 const size_t kMinFileLen = kPageSize; 84 size_t read_len = 0; 85 *buff = 0; 86 *buff_size = 0; 87 // The files we usually open are not seekable, so try different buffer sizes. 88 for (size_t size = kMinFileLen; size <= max_len; size *= 2) { 89 int fd = AsanOpenReadonly(file_name); 90 if (fd < 0) return 0; 91 AsanUnmapOrDie(*buff, *buff_size); 92 *buff = (char*)AsanMmapSomewhereOrDie(size, __FUNCTION__); 93 *buff_size = size; 94 // Read up to one page at a time. 95 read_len = 0; 96 bool reached_eof = false; 97 while (read_len + kPageSize <= size) { 98 size_t just_read = AsanRead(fd, *buff + read_len, kPageSize); 99 if (just_read == 0) { 100 reached_eof = true; 101 break; 102 } 103 read_len += just_read; 104 } 105 AsanClose(fd); 106 if (reached_eof) // We've read the whole file. 107 break; 108 } 109 return read_len; 110} 111 112void AsanDie() { 113 static int num_calls = 0; 114 if (AtomicInc(&num_calls) > 1) { 115 // Don't die twice - run a busy loop. 116 while (1) { } 117 } 118 if (FLAG_sleep_before_dying) { 119 Report("Sleeping for %d second(s)\n", FLAG_sleep_before_dying); 120 SleepForSeconds(FLAG_sleep_before_dying); 121 } 122 if (FLAG_unmap_shadow_on_exit) 123 AsanUnmapOrDie((void*)kLowShadowBeg, kHighShadowEnd - kLowShadowBeg); 124 if (death_callback) 125 death_callback(); 126 if (FLAG_abort_on_error) 127 Abort(); 128 Exit(FLAG_exitcode); 129} 130 131// ---------------------- mmap -------------------- {{{1 132void OutOfMemoryMessageAndDie(const char *mem_type, size_t size) { 133 Report("ERROR: AddressSanitizer failed to allocate " 134 "0x%zx (%zd) bytes of %s\n", 135 size, size, mem_type); 136 PRINT_CURRENT_STACK(); 137 ShowStatsAndAbort(); 138} 139 140// Reserve memory range [beg, end]. 141static void ReserveShadowMemoryRange(uintptr_t beg, uintptr_t end) { 142 CHECK((beg % kPageSize) == 0); 143 CHECK(((end + 1) % kPageSize) == 0); 144 size_t size = end - beg + 1; 145 void *res = AsanMmapFixedNoReserve(beg, size); 146 CHECK(res == (void*)beg && "ReserveShadowMemoryRange failed"); 147} 148 149// ---------------------- LowLevelAllocator ------------- {{{1 150void *LowLevelAllocator::Allocate(size_t size) { 151 CHECK((size & (size - 1)) == 0 && "size must be a power of two"); 152 if (allocated_end_ - allocated_current_ < size) { 153 size_t size_to_allocate = Max(size, kPageSize); 154 allocated_current_ = 155 (char*)AsanMmapSomewhereOrDie(size_to_allocate, __FUNCTION__); 156 allocated_end_ = allocated_current_ + size_to_allocate; 157 PoisonShadow((uintptr_t)allocated_current_, size_to_allocate, 158 kAsanInternalHeapMagic); 159 } 160 CHECK(allocated_end_ - allocated_current_ >= size); 161 void *res = allocated_current_; 162 allocated_current_ += size; 163 return res; 164} 165 166// ---------------------- DescribeAddress -------------------- {{{1 167static bool DescribeStackAddress(uintptr_t addr, uintptr_t access_size) { 168 AsanThread *t = asanThreadRegistry().FindThreadByStackAddress(addr); 169 if (!t) return false; 170 const intptr_t kBufSize = 4095; 171 char buf[kBufSize]; 172 uintptr_t offset = 0; 173 const char *frame_descr = t->GetFrameNameByAddr(addr, &offset); 174 // This string is created by the compiler and has the following form: 175 // "FunctioName n alloc_1 alloc_2 ... alloc_n" 176 // where alloc_i looks like "offset size len ObjectName ". 177 CHECK(frame_descr); 178 // Report the function name and the offset. 179 const char *name_end = internal_strchr(frame_descr, ' '); 180 CHECK(name_end); 181 buf[0] = 0; 182 internal_strncat(buf, frame_descr, 183 Min(kBufSize, 184 static_cast<intptr_t>(name_end - frame_descr))); 185 Printf("Address %p is located at offset %zu " 186 "in frame <%s> of T%d's stack:\n", 187 addr, offset, buf, t->tid()); 188 // Report the number of stack objects. 189 char *p; 190 size_t n_objects = internal_simple_strtoll(name_end, &p, 10); 191 CHECK(n_objects > 0); 192 Printf(" This frame has %zu object(s):\n", n_objects); 193 // Report all objects in this frame. 194 for (size_t i = 0; i < n_objects; i++) { 195 size_t beg, size; 196 intptr_t len; 197 beg = internal_simple_strtoll(p, &p, 10); 198 size = internal_simple_strtoll(p, &p, 10); 199 len = internal_simple_strtoll(p, &p, 10); 200 if (beg <= 0 || size <= 0 || len < 0 || *p != ' ') { 201 Printf("AddressSanitizer can't parse the stack frame descriptor: |%s|\n", 202 frame_descr); 203 break; 204 } 205 p++; 206 buf[0] = 0; 207 internal_strncat(buf, p, Min(kBufSize, len)); 208 p += len; 209 Printf(" [%zu, %zu) '%s'\n", beg, beg + size, buf); 210 } 211 Printf("HINT: this may be a false positive if your program uses " 212 "some custom stack unwind mechanism\n" 213 " (longjmp and C++ exceptions *are* supported)\n"); 214 t->summary()->Announce(); 215 return true; 216} 217 218static NOINLINE void DescribeAddress(uintptr_t addr, uintptr_t access_size) { 219 // Check if this is a global. 220 if (DescribeAddrIfGlobal(addr)) 221 return; 222 223 if (DescribeStackAddress(addr, access_size)) 224 return; 225 226 // finally, check if this is a heap. 227 DescribeHeapAddress(addr, access_size); 228} 229 230// -------------------------- Run-time entry ------------------- {{{1 231// exported functions 232#define ASAN_REPORT_ERROR(type, is_write, size) \ 233extern "C" NOINLINE ASAN_INTERFACE_ATTRIBUTE \ 234void __asan_report_ ## type ## size(uintptr_t addr); \ 235void __asan_report_ ## type ## size(uintptr_t addr) { \ 236 GET_CALLER_PC_BP_SP; \ 237 __asan_report_error(pc, bp, sp, addr, is_write, size); \ 238} 239 240ASAN_REPORT_ERROR(load, false, 1) 241ASAN_REPORT_ERROR(load, false, 2) 242ASAN_REPORT_ERROR(load, false, 4) 243ASAN_REPORT_ERROR(load, false, 8) 244ASAN_REPORT_ERROR(load, false, 16) 245ASAN_REPORT_ERROR(store, true, 1) 246ASAN_REPORT_ERROR(store, true, 2) 247ASAN_REPORT_ERROR(store, true, 4) 248ASAN_REPORT_ERROR(store, true, 8) 249ASAN_REPORT_ERROR(store, true, 16) 250 251// Force the linker to keep the symbols for various ASan interface functions. 252// We want to keep those in the executable in order to let the instrumented 253// dynamic libraries access the symbol even if it is not used by the executable 254// itself. This should help if the build system is removing dead code at link 255// time. 256static NOINLINE void force_interface_symbols() { 257 volatile int fake_condition = 0; // prevent dead condition elimination. 258 if (fake_condition) { 259 __asan_report_load1(0); 260 __asan_report_load2(0); 261 __asan_report_load4(0); 262 __asan_report_load8(0); 263 __asan_report_load16(0); 264 __asan_report_store1(0); 265 __asan_report_store2(0); 266 __asan_report_store4(0); 267 __asan_report_store8(0); 268 __asan_report_store16(0); 269 __asan_register_global(0, 0, NULL); 270 __asan_register_globals(NULL, 0); 271 __asan_unregister_globals(NULL, 0); 272 __asan_set_death_callback(NULL); 273 __asan_set_error_report_callback(NULL); 274 __asan_handle_no_return(); 275 } 276} 277 278// -------------------------- Init ------------------- {{{1 279static int64_t IntFlagValue(const char *flags, const char *flag, 280 int64_t default_val) { 281 if (!flags) return default_val; 282 const char *str = internal_strstr(flags, flag); 283 if (!str) return default_val; 284 return internal_atoll(str + internal_strlen(flag)); 285} 286 287static void asan_atexit() { 288 Printf("AddressSanitizer exit stats:\n"); 289 __asan_print_accumulated_stats(); 290} 291 292void CheckFailed(const char *cond, const char *file, int line) { 293 Report("CHECK failed: %s at %s:%d\n", cond, file, line); 294 PRINT_CURRENT_STACK(); 295 ShowStatsAndAbort(); 296} 297 298} // namespace __asan 299 300// ---------------------- Interface ---------------- {{{1 301using namespace __asan; // NOLINT 302 303int __asan_set_error_exit_code(int exit_code) { 304 int old = FLAG_exitcode; 305 FLAG_exitcode = exit_code; 306 return old; 307} 308 309void NOINLINE __asan_handle_no_return() { 310 int local_stack; 311 AsanThread *curr_thread = asanThreadRegistry().GetCurrent(); 312 CHECK(curr_thread); 313 uintptr_t top = curr_thread->stack_top(); 314 uintptr_t bottom = ((uintptr_t)&local_stack - kPageSize) & ~(kPageSize-1); 315 PoisonShadow(bottom, top - bottom, 0); 316} 317 318void NOINLINE __asan_set_death_callback(void (*callback)(void)) { 319 death_callback = callback; 320} 321 322void NOINLINE __asan_set_error_report_callback(void (*callback)(const char*)) { 323 error_report_callback = callback; 324 if (callback) { 325 error_message_buffer_size = 1 << 16; 326 error_message_buffer = 327 (char*)AsanMmapSomewhereOrDie(error_message_buffer_size, __FUNCTION__); 328 error_message_buffer_pos = 0; 329 } 330} 331 332void __asan_report_error(uintptr_t pc, uintptr_t bp, uintptr_t sp, 333 uintptr_t addr, bool is_write, size_t access_size) { 334 // Do not print more than one report, otherwise they will mix up. 335 static int num_calls = 0; 336 if (AtomicInc(&num_calls) > 1) return; 337 338 Printf("=================================================================\n"); 339 const char *bug_descr = "unknown-crash"; 340 if (AddrIsInMem(addr)) { 341 uint8_t *shadow_addr = (uint8_t*)MemToShadow(addr); 342 // If we are accessing 16 bytes, look at the second shadow byte. 343 if (*shadow_addr == 0 && access_size > SHADOW_GRANULARITY) 344 shadow_addr++; 345 // If we are in the partial right redzone, look at the next shadow byte. 346 if (*shadow_addr > 0 && *shadow_addr < 128) 347 shadow_addr++; 348 switch (*shadow_addr) { 349 case kAsanHeapLeftRedzoneMagic: 350 case kAsanHeapRightRedzoneMagic: 351 bug_descr = "heap-buffer-overflow"; 352 break; 353 case kAsanHeapFreeMagic: 354 bug_descr = "heap-use-after-free"; 355 break; 356 case kAsanStackLeftRedzoneMagic: 357 bug_descr = "stack-buffer-underflow"; 358 break; 359 case kAsanStackMidRedzoneMagic: 360 case kAsanStackRightRedzoneMagic: 361 case kAsanStackPartialRedzoneMagic: 362 bug_descr = "stack-buffer-overflow"; 363 break; 364 case kAsanStackAfterReturnMagic: 365 bug_descr = "stack-use-after-return"; 366 break; 367 case kAsanUserPoisonedMemoryMagic: 368 bug_descr = "use-after-poison"; 369 break; 370 case kAsanGlobalRedzoneMagic: 371 bug_descr = "global-buffer-overflow"; 372 break; 373 } 374 } 375 376 AsanThread *curr_thread = asanThreadRegistry().GetCurrent(); 377 int curr_tid = asanThreadRegistry().GetCurrentTidOrMinusOne(); 378 379 if (curr_thread) { 380 // We started reporting an error message. Stop using the fake stack 381 // in case we will call an instrumented function from a symbolizer. 382 curr_thread->fake_stack().StopUsingFakeStack(); 383 } 384 385 Report("ERROR: AddressSanitizer %s on address " 386 "%p at pc 0x%zx bp 0x%zx sp 0x%zx\n", 387 bug_descr, addr, pc, bp, sp); 388 389 Printf("%s of size %zu at %p thread T%d\n", 390 access_size ? (is_write ? "WRITE" : "READ") : "ACCESS", 391 access_size, addr, curr_tid); 392 393 if (FLAG_debug) { 394 PrintBytes("PC: ", (uintptr_t*)pc); 395 } 396 397 GET_STACK_TRACE_WITH_PC_AND_BP(kStackTraceMax, pc, bp); 398 stack.PrintStack(); 399 400 CHECK(AddrIsInMem(addr)); 401 402 DescribeAddress(addr, access_size); 403 404 uintptr_t shadow_addr = MemToShadow(addr); 405 Report("ABORTING\n"); 406 __asan_print_accumulated_stats(); 407 Printf("Shadow byte and word:\n"); 408 Printf(" %p: %x\n", shadow_addr, *(unsigned char*)shadow_addr); 409 uintptr_t aligned_shadow = shadow_addr & ~(kWordSize - 1); 410 PrintBytes(" ", (uintptr_t*)(aligned_shadow)); 411 Printf("More shadow bytes:\n"); 412 PrintBytes(" ", (uintptr_t*)(aligned_shadow-4*kWordSize)); 413 PrintBytes(" ", (uintptr_t*)(aligned_shadow-3*kWordSize)); 414 PrintBytes(" ", (uintptr_t*)(aligned_shadow-2*kWordSize)); 415 PrintBytes(" ", (uintptr_t*)(aligned_shadow-1*kWordSize)); 416 PrintBytes("=>", (uintptr_t*)(aligned_shadow+0*kWordSize)); 417 PrintBytes(" ", (uintptr_t*)(aligned_shadow+1*kWordSize)); 418 PrintBytes(" ", (uintptr_t*)(aligned_shadow+2*kWordSize)); 419 PrintBytes(" ", (uintptr_t*)(aligned_shadow+3*kWordSize)); 420 PrintBytes(" ", (uintptr_t*)(aligned_shadow+4*kWordSize)); 421 if (error_report_callback) { 422 error_report_callback(error_message_buffer); 423 } 424 AsanDie(); 425} 426 427static void ParseAsanOptions(const char *options) { 428 FLAG_malloc_context_size = 429 IntFlagValue(options, "malloc_context_size=", kMallocContextSize); 430 CHECK(FLAG_malloc_context_size <= kMallocContextSize); 431 432 FLAG_max_malloc_fill_size = 433 IntFlagValue(options, "max_malloc_fill_size=", 0); 434 435 FLAG_v = IntFlagValue(options, "verbosity=", 0); 436 437 FLAG_redzone = IntFlagValue(options, "redzone=", 438 (ASAN_LOW_MEMORY) ? 64 : 128); 439 CHECK(FLAG_redzone >= 32); 440 CHECK((FLAG_redzone & (FLAG_redzone - 1)) == 0); 441 442 FLAG_atexit = IntFlagValue(options, "atexit=", 0); 443 FLAG_poison_shadow = IntFlagValue(options, "poison_shadow=", 1); 444 FLAG_report_globals = IntFlagValue(options, "report_globals=", 1); 445 FLAG_handle_segv = IntFlagValue(options, "handle_segv=", ASAN_NEEDS_SEGV); 446 FLAG_use_sigaltstack = IntFlagValue(options, "use_sigaltstack=", 0); 447 FLAG_symbolize = IntFlagValue(options, "symbolize=", 1); 448 FLAG_demangle = IntFlagValue(options, "demangle=", 1); 449 FLAG_debug = IntFlagValue(options, "debug=", 0); 450 FLAG_replace_cfallocator = IntFlagValue(options, "replace_cfallocator=", 1); 451 FLAG_replace_str = IntFlagValue(options, "replace_str=", 1); 452 FLAG_replace_intrin = IntFlagValue(options, "replace_intrin=", 1); 453 FLAG_use_fake_stack = IntFlagValue(options, "use_fake_stack=", 1); 454 FLAG_exitcode = IntFlagValue(options, "exitcode=", 455 ASAN_DEFAULT_FAILURE_EXITCODE); 456 FLAG_allow_user_poisoning = IntFlagValue(options, 457 "allow_user_poisoning=", 1); 458 FLAG_sleep_before_dying = IntFlagValue(options, "sleep_before_dying=", 0); 459 FLAG_abort_on_error = IntFlagValue(options, "abort_on_error=", 0); 460 FLAG_unmap_shadow_on_exit = IntFlagValue(options, "unmap_shadow_on_exit=", 0); 461 // By default, disable core dumper on 64-bit -- 462 // it makes little sense to dump 16T+ core. 463 FLAG_disable_core = IntFlagValue(options, "disable_core=", __WORDSIZE == 64); 464 465 // Allow the users to work around the bug in Nvidia drivers prior to 295.*. 466 FLAG_check_malloc_usable_size = 467 IntFlagValue(options, "check_malloc_usable_size=", 1); 468 469 FLAG_quarantine_size = IntFlagValue(options, "quarantine_size=", 470 (ASAN_LOW_MEMORY) ? 1UL << 24 : 1UL << 28); 471} 472 473void __asan_init() { 474 if (asan_inited) return; 475 asan_init_is_running = true; 476 477 // Make sure we are not statically linked. 478 AsanDoesNotSupportStaticLinkage(); 479 480 // flags 481 const char *options = AsanGetEnv("ASAN_OPTIONS"); 482 483 if (FLAG_v) { 484 Report("Parsed ASAN_OPTIONS: %s\n", options); 485 } 486 487 ParseAsanOptions(options); 488 489 if (FLAG_atexit) { 490 Atexit(asan_atexit); 491 } 492 493 // interceptors 494 InitializeAsanInterceptors(); 495 496 ReplaceSystemMalloc(); 497 ReplaceOperatorsNewAndDelete(); 498 499 if (FLAG_v) { 500 Printf("|| `[%p, %p]` || HighMem ||\n", kHighMemBeg, kHighMemEnd); 501 Printf("|| `[%p, %p]` || HighShadow ||\n", 502 kHighShadowBeg, kHighShadowEnd); 503 Printf("|| `[%p, %p]` || ShadowGap ||\n", 504 kShadowGapBeg, kShadowGapEnd); 505 Printf("|| `[%p, %p]` || LowShadow ||\n", 506 kLowShadowBeg, kLowShadowEnd); 507 Printf("|| `[%p, %p]` || LowMem ||\n", kLowMemBeg, kLowMemEnd); 508 Printf("MemToShadow(shadow): %p %p %p %p\n", 509 MEM_TO_SHADOW(kLowShadowBeg), 510 MEM_TO_SHADOW(kLowShadowEnd), 511 MEM_TO_SHADOW(kHighShadowBeg), 512 MEM_TO_SHADOW(kHighShadowEnd)); 513 Printf("red_zone=%zu\n", (size_t)FLAG_redzone); 514 Printf("malloc_context_size=%zu\n", (size_t)FLAG_malloc_context_size); 515 516 Printf("SHADOW_SCALE: %zx\n", (size_t)SHADOW_SCALE); 517 Printf("SHADOW_GRANULARITY: %zx\n", (size_t)SHADOW_GRANULARITY); 518 Printf("SHADOW_OFFSET: %zx\n", (size_t)SHADOW_OFFSET); 519 CHECK(SHADOW_SCALE >= 3 && SHADOW_SCALE <= 7); 520 } 521 522 if (FLAG_disable_core) { 523 AsanDisableCoreDumper(); 524 } 525 526 if (AsanShadowRangeIsAvailable()) { 527 if (kLowShadowBeg != kLowShadowEnd) { 528 // mmap the low shadow plus at least one page. 529 ReserveShadowMemoryRange(kLowShadowBeg - kMmapGranularity, kLowShadowEnd); 530 } 531 // mmap the high shadow. 532 ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd); 533 // protect the gap 534 void *prot = AsanMprotect(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1); 535 CHECK(prot == (void*)kShadowGapBeg); 536 } else { 537 Report("Shadow memory range interleaves with an existing memory mapping. " 538 "ASan cannot proceed correctly. ABORTING.\n"); 539 AsanDumpProcessMap(); 540 AsanDie(); 541 } 542 543 InstallSignalHandlers(); 544 545 // On Linux AsanThread::ThreadStart() calls malloc() that's why asan_inited 546 // should be set to 1 prior to initializing the threads. 547 asan_inited = 1; 548 asan_init_is_running = false; 549 550 asanThreadRegistry().Init(); 551 asanThreadRegistry().GetMain()->ThreadStart(); 552 force_interface_symbols(); // no-op. 553 554 if (FLAG_v) { 555 Report("AddressSanitizer Init done\n"); 556 } 557} 558 559#if defined(ASAN_USE_PREINIT_ARRAY) 560 // On Linux, we force __asan_init to be called before anyone else 561 // by placing it into .preinit_array section. 562 // FIXME: do we have anything like this on Mac? 563 __attribute__((section(".preinit_array"))) 564 typeof(__asan_init) *__asan_preinit =__asan_init; 565#elif defined(_WIN32) && defined(_DLL) 566 // On Windows, when using dynamic CRT (/MD), we can put a pointer 567 // to __asan_init into the global list of C initializers. 568 // See crt0dat.c in the CRT sources for the details. 569 #pragma section(".CRT$XIB", long, read) // NOLINT 570 __declspec(allocate(".CRT$XIB")) void (*__asan_preinit)() = __asan_init; 571#endif 572