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