compiler-rt/lib/asan/asan_globals.cpp

   1 //===-- asan_globals.cpp --------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file is a part of AddressSanitizer, an address sanity checker.
  10 //
  11 // Handle globals.
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "asan_interceptors.h"
  15 #include "asan_internal.h"
  16 #include "asan_mapping.h"
  17 #include "asan_poisoning.h"
  18 #include "asan_report.h"
  19 #include "asan_stack.h"
  20 #include "asan_stats.h"
  21 #include "asan_suppressions.h"
  22 #include "asan_thread.h"
  23 #include "sanitizer_common/sanitizer_common.h"
  24 #include "sanitizer_common/sanitizer_mutex.h"
  25 #include "sanitizer_common/sanitizer_placement_new.h"
  26 #include "sanitizer_common/sanitizer_stackdepot.h"
  27 #include "sanitizer_common/sanitizer_symbolizer.h"
  28
  29 namespace __asan {
  30
  31 typedef __asan_global Global;
  32
  33 struct ListOfGlobals {
  34   const Global *g;
  35   ListOfGlobals *next;
  36 };
  37
  38 static Mutex mu_for_globals;
  39 static ListOfGlobals *list_of_all_globals;
  40
  41 static const int kDynamicInitGlobalsInitialCapacity = 512;
  42 struct DynInitGlobal {
  43   Global g;
  44   bool initialized;
  45 };
  46 typedef InternalMmapVector<DynInitGlobal> VectorOfGlobals;
  47 // Lazy-initialized and never deleted.
  48 static VectorOfGlobals *dynamic_init_globals;
  49
  50 // We want to remember where a certain range of globals was registered.
  51 struct GlobalRegistrationSite {
  52   u32 stack_id;
  53   Global *g_first, *g_last;
  54 };
  55 typedef InternalMmapVector<GlobalRegistrationSite> GlobalRegistrationSiteVector;
  56 static GlobalRegistrationSiteVector *global_registration_site_vector;
  57
  58 ALWAYS_INLINE void PoisonShadowForGlobal(const Global *g, u8 value) {
  59   FastPoisonShadow(g->beg, g->size_with_redzone, value);
  60 }
  61
  62 ALWAYS_INLINE void PoisonRedZones(const Global &g) {
  63   uptr aligned_size = RoundUpTo(g.size, ASAN_SHADOW_GRANULARITY);
  64   FastPoisonShadow(g.beg + aligned_size, g.size_with_redzone - aligned_size,
  65                    kAsanGlobalRedzoneMagic);
  66   if (g.size != aligned_size) {
  67     FastPoisonShadowPartialRightRedzone(
  68         g.beg + RoundDownTo(g.size, ASAN_SHADOW_GRANULARITY),
  69         g.size % ASAN_SHADOW_GRANULARITY, ASAN_SHADOW_GRANULARITY,
  70         kAsanGlobalRedzoneMagic);
  71   }
  72 }
  73
  74 const uptr kMinimalDistanceFromAnotherGlobal = 64;
  75
  76 static bool IsAddressNearGlobal(uptr addr, const __asan_global &g) {
  77   if (addr <= g.beg - kMinimalDistanceFromAnotherGlobal) return false;
  78   if (addr >= g.beg + g.size_with_redzone) return false;
  79   return true;
  80 }
  81
  82 static void ReportGlobal(const Global &g, const char *prefix) {
  83   Report(
  84       "%s Global[%p]: beg=%p size=%zu/%zu name=%s module=%s dyn_init=%zu "
  85       "odr_indicator=%p\n",
  86       prefix, (void *)&g, (void *)g.beg, g.size, g.size_with_redzone, g.name,
  87       g.module_name, g.has_dynamic_init, (void *)g.odr_indicator);
  88
  89   DataInfo info;
  90   if (Symbolizer::GetOrInit()->SymbolizeData(g.beg, &info) && info.line != 0) {
  91     Report("  location: name=%s, %d\n", info.file, static_cast<int>(info.line));
  92   } else if (g.gcc_location != 0) {
  93     // Fallback to Global::gcc_location
  94     Report("  location: name=%s, %d\n", g.gcc_location->filename, g.gcc_location->line_no);
  95   }
  96 }
  97
  98 static u32 FindRegistrationSite(const Global *g) {
  99   mu_for_globals.CheckLocked();
 100   CHECK(global_registration_site_vector);
 101   for (uptr i = 0, n = global_registration_site_vector->size(); i < n; i++) {
 102     GlobalRegistrationSite &grs = (*global_registration_site_vector)[i];
 103     if (g >= grs.g_first && g <= grs.g_last)
 104       return grs.stack_id;
 105   }
 106   return 0;
 107 }
 108
 109 int GetGlobalsForAddress(uptr addr, Global *globals, u32 *reg_sites,
 110                          int max_globals) {
 111   if (!flags()->report_globals) return 0;
 112   Lock lock(&mu_for_globals);
 113   int res = 0;
 114   for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
 115     const Global &g = *l->g;
 116     if (flags()->report_globals >= 2)
 117       ReportGlobal(g, "Search");
 118     if (IsAddressNearGlobal(addr, g)) {
 119       internal_memcpy(&globals[res], &g, sizeof(g));
 120       if (reg_sites)
 121         reg_sites[res] = FindRegistrationSite(&g);
 122       res++;
 123       if (res == max_globals)
 124         break;
 125     }
 126   }
 127   return res;
 128 }
 129
 130 enum GlobalSymbolState {
 131   UNREGISTERED = 0,
 132   REGISTERED = 1
 133 };
 134
 135 // Check ODR violation for given global G via special ODR indicator. We use
 136 // this method in case compiler instruments global variables through their
 137 // local aliases.
 138 static void CheckODRViolationViaIndicator(const Global *g) {
 139   // Instrumentation requests to skip ODR check.
 140   if (g->odr_indicator == UINTPTR_MAX)
 141     return;
 142   u8 *odr_indicator = reinterpret_cast<u8 *>(g->odr_indicator);
 143   if (*odr_indicator == UNREGISTERED) {
 144     *odr_indicator = REGISTERED;
 145     return;
 146   }
 147   // If *odr_indicator is DEFINED, some module have already registered
 148   // externally visible symbol with the same name. This is an ODR violation.
 149   for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
 150     if (g->odr_indicator == l->g->odr_indicator &&
 151         (flags()->detect_odr_violation >= 2 || g->size != l->g->size) &&
 152         !IsODRViolationSuppressed(g->name))
 153       ReportODRViolation(g, FindRegistrationSite(g),
 154                          l->g, FindRegistrationSite(l->g));
 155   }
 156 }
 157
 158 // Check ODR violation for given global G by checking if it's already poisoned.
 159 // We use this method in case compiler doesn't use private aliases for global
 160 // variables.
 161 static void CheckODRViolationViaPoisoning(const Global *g) {
 162   if (__asan_region_is_poisoned(g->beg, g->size_with_redzone)) {
 163     // This check may not be enough: if the first global is much larger
 164     // the entire redzone of the second global may be within the first global.
 165     for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
 166       if (g->beg == l->g->beg &&
 167           (flags()->detect_odr_violation >= 2 || g->size != l->g->size) &&
 168           !IsODRViolationSuppressed(g->name))
 169         ReportODRViolation(g, FindRegistrationSite(g),
 170                            l->g, FindRegistrationSite(l->g));
 171     }
 172   }
 173 }
 174
 175 // Clang provides two different ways for global variables protection:
 176 // it can poison the global itself or its private alias. In former
 177 // case we may poison same symbol multiple times, that can help us to
 178 // cheaply detect ODR violation: if we try to poison an already poisoned
 179 // global, we have ODR violation error.
 180 // In latter case, we poison each symbol exactly once, so we use special
 181 // indicator symbol to perform similar check.
 182 // In either case, compiler provides a special odr_indicator field to Global
 183 // structure, that can contain two kinds of values:
 184 //   1) Non-zero value. In this case, odr_indicator is an address of
 185 //      corresponding indicator variable for given global.
 186 //   2) Zero. This means that we don't use private aliases for global variables
 187 //      and can freely check ODR violation with the first method.
 188 //
 189 // This routine chooses between two different methods of ODR violation
 190 // detection.
 191 static inline bool UseODRIndicator(const Global *g) {
 192   return g->odr_indicator > 0;
 193 }
 194
 195 // Register a global variable.
 196 // This function may be called more than once for every global
 197 // so we store the globals in a map.
 198 static void RegisterGlobal(const Global *g) {
 199   CHECK(asan_inited);
 200   if (flags()->report_globals >= 2)
 201     ReportGlobal(*g, "Added");
 202   CHECK(flags()->report_globals);
 203   CHECK(AddrIsInMem(g->beg));
 204   if (!AddrIsAlignedByGranularity(g->beg)) {
 205     Report("The following global variable is not properly aligned.\n");
 206     Report("This may happen if another global with the same name\n");
 207     Report("resides in another non-instrumented module.\n");
 208     Report("Or the global comes from a C file built w/o -fno-common.\n");
 209     Report("In either case this is likely an ODR violation bug,\n");
 210     Report("but AddressSanitizer can not provide more details.\n");
 211     ReportODRViolation(g, FindRegistrationSite(g), g, FindRegistrationSite(g));
 212     CHECK(AddrIsAlignedByGranularity(g->beg));
 213   }
 214   CHECK(AddrIsAlignedByGranularity(g->size_with_redzone));
 215   if (flags()->detect_odr_violation) {
 216     // Try detecting ODR (One Definition Rule) violation, i.e. the situation
 217     // where two globals with the same name are defined in different modules.
 218     if (UseODRIndicator(g))
 219       CheckODRViolationViaIndicator(g);
 220     else
 221       CheckODRViolationViaPoisoning(g);
 222   }
 223   if (CanPoisonMemory())
 224     PoisonRedZones(*g);
 225   ListOfGlobals *l = new (GetGlobalLowLevelAllocator()) ListOfGlobals;
 226   l->g = g;
 227   l->next = list_of_all_globals;
 228   list_of_all_globals = l;
 229   if (g->has_dynamic_init) {
 230     if (!dynamic_init_globals) {
 231       dynamic_init_globals = new (GetGlobalLowLevelAllocator()) VectorOfGlobals;
 232       dynamic_init_globals->reserve(kDynamicInitGlobalsInitialCapacity);
 233     }
 234     DynInitGlobal dyn_global = { *g, false };
 235     dynamic_init_globals->push_back(dyn_global);
 236   }
 237 }
 238
 239 static void UnregisterGlobal(const Global *g) {
 240   CHECK(asan_inited);
 241   if (flags()->report_globals >= 2)
 242     ReportGlobal(*g, "Removed");
 243   CHECK(flags()->report_globals);
 244   CHECK(AddrIsInMem(g->beg));
 245   CHECK(AddrIsAlignedByGranularity(g->beg));
 246   CHECK(AddrIsAlignedByGranularity(g->size_with_redzone));
 247   if (CanPoisonMemory())
 248     PoisonShadowForGlobal(g, 0);
 249   // We unpoison the shadow memory for the global but we do not remove it from
 250   // the list because that would require O(n^2) time with the current list
 251   // implementation. It might not be worth doing anyway.
 252
 253   // Release ODR indicator.
 254   if (UseODRIndicator(g) && g->odr_indicator != UINTPTR_MAX) {
 255     u8 *odr_indicator = reinterpret_cast<u8 *>(g->odr_indicator);
 256     *odr_indicator = UNREGISTERED;
 257   }
 258 }
 259
 260 void StopInitOrderChecking() {
 261   Lock lock(&mu_for_globals);
 262   if (!flags()->check_initialization_order || !dynamic_init_globals)
 263     return;
 264   flags()->check_initialization_order = false;
 265   for (uptr i = 0, n = dynamic_init_globals->size(); i < n; ++i) {
 266     DynInitGlobal &dyn_g = (*dynamic_init_globals)[i];
 267     const Global *g = &dyn_g.g;
 268     // Unpoison the whole global.
 269     PoisonShadowForGlobal(g, 0);
 270     // Poison redzones back.
 271     PoisonRedZones(*g);
 272   }
 273 }
 274
 275 static bool IsASCII(unsigned char c) { return /*0x00 <= c &&*/ c <= 0x7F; }
 276
 277 const char *MaybeDemangleGlobalName(const char *name) {
 278   // We can spoil names of globals with C linkage, so use an heuristic
 279   // approach to check if the name should be demangled.
 280   bool should_demangle = false;
 281   if (name[0] == '_' && name[1] == 'Z')
 282     should_demangle = true;
 283   else if (SANITIZER_WINDOWS && name[0] == '\01' && name[1] == '?')
 284     should_demangle = true;
 285
 286   return should_demangle ? Symbolizer::GetOrInit()->Demangle(name) : name;
 287 }
 288
 289 // Check if the global is a zero-terminated ASCII string. If so, print it.
 290 void PrintGlobalNameIfASCII(InternalScopedString *str, const __asan_global &g) {
 291   for (uptr p = g.beg; p < g.beg + g.size - 1; p++) {
 292     unsigned char c = *(unsigned char *)p;
 293     if (c == '\0' || !IsASCII(c)) return;
 294   }
 295   if (*(char *)(g.beg + g.size - 1) != '\0') return;
 296   str->AppendF("  '%s' is ascii string '%s'\n", MaybeDemangleGlobalName(g.name),
 297                (char *)g.beg);
 298 }
 299
 300 void PrintGlobalLocation(InternalScopedString *str, const __asan_global &g) {
 301   DataInfo info;
 302   if (Symbolizer::GetOrInit()->SymbolizeData(g.beg, &info) && info.line != 0) {
 303     str->AppendF("%s:%d", info.file, static_cast<int>(info.line));
 304   } else if (g.gcc_location != 0) {
 305     // Fallback to Global::gcc_location
 306     str->AppendF("%s", g.gcc_location->filename ? g.gcc_location->filename
 307                                                 : g.module_name);
 308     if (g.gcc_location->line_no)
 309       str->AppendF(":%d", g.gcc_location->line_no);
 310     if (g.gcc_location->column_no)
 311       str->AppendF(":%d", g.gcc_location->column_no);
 312   } else {
 313     str->AppendF("%s", g.module_name);
 314   }
 315 }
 316
 317 } // namespace __asan
 318
 319 // ---------------------- Interface ---------------- {{{1
 320 using namespace __asan;
 321
 322 // Apply __asan_register_globals to all globals found in the same loaded
 323 // executable or shared library as `flag'. The flag tracks whether globals have
 324 // already been registered or not for this image.
 325 void __asan_register_image_globals(uptr *flag) {
 326   if (*flag)
 327     return;
 328   AsanApplyToGlobals(__asan_register_globals, flag);
 329   *flag = 1;
 330 }
 331
 332 // This mirrors __asan_register_image_globals.
 333 void __asan_unregister_image_globals(uptr *flag) {
 334   if (!*flag)
 335     return;
 336   AsanApplyToGlobals(__asan_unregister_globals, flag);
 337   *flag = 0;
 338 }
 339
 340 void __asan_register_elf_globals(uptr *flag, void *start, void *stop) {
 341   if (*flag) return;
 342   if (!start) return;
 343   CHECK_EQ(0, ((uptr)stop - (uptr)start) % sizeof(__asan_global));
 344   __asan_global *globals_start = (__asan_global*)start;
 345   __asan_global *globals_stop = (__asan_global*)stop;
 346   __asan_register_globals(globals_start, globals_stop - globals_start);
 347   *flag = 1;
 348 }
 349
 350 void __asan_unregister_elf_globals(uptr *flag, void *start, void *stop) {
 351   if (!*flag) return;
 352   if (!start) return;
 353   CHECK_EQ(0, ((uptr)stop - (uptr)start) % sizeof(__asan_global));
 354   __asan_global *globals_start = (__asan_global*)start;
 355   __asan_global *globals_stop = (__asan_global*)stop;
 356   __asan_unregister_globals(globals_start, globals_stop - globals_start);
 357   *flag = 0;
 358 }
 359
 360 // Register an array of globals.
 361 void __asan_register_globals(__asan_global *globals, uptr n) {
 362   if (!flags()->report_globals) return;
 363   GET_STACK_TRACE_MALLOC;
 364   u32 stack_id = StackDepotPut(stack);
 365   Lock lock(&mu_for_globals);
 366   if (!global_registration_site_vector) {
 367     global_registration_site_vector =
 368         new (GetGlobalLowLevelAllocator()) GlobalRegistrationSiteVector;
 369     global_registration_site_vector->reserve(128);
 370   }
 371   GlobalRegistrationSite site = {stack_id, &globals[0], &globals[n - 1]};
 372   global_registration_site_vector->push_back(site);
 373   if (flags()->report_globals >= 2) {
 374     PRINT_CURRENT_STACK();
 375     Printf("=== ID %d; %p %p\n", stack_id, (void *)&globals[0],
 376            (void *)&globals[n - 1]);
 377   }
 378   for (uptr i = 0; i < n; i++) {
 379     if (SANITIZER_WINDOWS && globals[i].beg == 0) {
 380       // The MSVC incremental linker may pad globals out to 256 bytes. As long
 381       // as __asan_global is less than 256 bytes large and its size is a power
 382       // of two, we can skip over the padding.
 383       static_assert(
 384           sizeof(__asan_global) < 256 &&
 385               (sizeof(__asan_global) & (sizeof(__asan_global) - 1)) == 0,
 386           "sizeof(__asan_global) incompatible with incremental linker padding");
 387       // If these are padding bytes, the rest of the global should be zero.
 388       CHECK(globals[i].size == 0 && globals[i].size_with_redzone == 0 &&
 389             globals[i].name == nullptr && globals[i].module_name == nullptr &&
 390             globals[i].odr_indicator == 0);
 391       continue;
 392     }
 393     RegisterGlobal(&globals[i]);
 394   }
 395
 396   // Poison the metadata. It should not be accessible to user code.
 397   PoisonShadow(reinterpret_cast<uptr>(globals), n * sizeof(__asan_global),
 398                kAsanGlobalRedzoneMagic);
 399 }
 400
 401 // Unregister an array of globals.
 402 // We must do this when a shared objects gets dlclosed.
 403 void __asan_unregister_globals(__asan_global *globals, uptr n) {
 404   if (!flags()->report_globals) return;
 405   Lock lock(&mu_for_globals);
 406   for (uptr i = 0; i < n; i++) {
 407     if (SANITIZER_WINDOWS && globals[i].beg == 0) {
 408       // Skip globals that look like padding from the MSVC incremental linker.
 409       // See comment in __asan_register_globals.
 410       continue;
 411     }
 412     UnregisterGlobal(&globals[i]);
 413   }
 414
 415   // Unpoison the metadata.
 416   PoisonShadow(reinterpret_cast<uptr>(globals), n * sizeof(__asan_global), 0);
 417 }
 418
 419 // This method runs immediately prior to dynamic initialization in each TU,
 420 // when all dynamically initialized globals are unpoisoned.  This method
 421 // poisons all global variables not defined in this TU, so that a dynamic
 422 // initializer can only touch global variables in the same TU.
 423 void __asan_before_dynamic_init(const char *module_name) {
 424   if (!flags()->check_initialization_order ||
 425       !CanPoisonMemory() ||
 426       !dynamic_init_globals)
 427     return;
 428   bool strict_init_order = flags()->strict_init_order;
 429   CHECK(module_name);
 430   CHECK(asan_inited);
 431   Lock lock(&mu_for_globals);
 432   if (flags()->report_globals >= 3)
 433     Printf("DynInitPoison module: %s\n", module_name);
 434   for (uptr i = 0, n = dynamic_init_globals->size(); i < n; ++i) {
 435     DynInitGlobal &dyn_g = (*dynamic_init_globals)[i];
 436     const Global *g = &dyn_g.g;
 437     if (dyn_g.initialized)
 438       continue;
 439     if (g->module_name != module_name)
 440       PoisonShadowForGlobal(g, kAsanInitializationOrderMagic);
 441     else if (!strict_init_order)
 442       dyn_g.initialized = true;
 443   }
 444 }
 445
 446 // This method runs immediately after dynamic initialization in each TU, when
 447 // all dynamically initialized globals except for those defined in the current
 448 // TU are poisoned.  It simply unpoisons all dynamically initialized globals.
 449 void __asan_after_dynamic_init() {
 450   if (!flags()->check_initialization_order ||
 451       !CanPoisonMemory() ||
 452       !dynamic_init_globals)
 453     return;
 454   CHECK(asan_inited);
 455   Lock lock(&mu_for_globals);
 456   // FIXME: Optionally report that we're unpoisoning globals from a module.
 457   for (uptr i = 0, n = dynamic_init_globals->size(); i < n; ++i) {
 458     DynInitGlobal &dyn_g = (*dynamic_init_globals)[i];
 459     const Global *g = &dyn_g.g;
 460     if (!dyn_g.initialized) {
 461       // Unpoison the whole global.
 462       PoisonShadowForGlobal(g, 0);
 463       // Poison redzones back.
 464       PoisonRedZones(*g);
 465     }
 466   }
 467 }