1 //===-- asan_globals.cc ---------------------------------------------------===//
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
7 //===----------------------------------------------------------------------===//
9 // This file is a part of AddressSanitizer, an address sanity checker.
12 //===----------------------------------------------------------------------===//
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"
31 typedef __asan_global Global;
33 struct ListOfGlobals {
38 static BlockingMutex mu_for_globals(LINKER_INITIALIZED);
39 static LowLevelAllocator allocator_for_globals;
40 static ListOfGlobals *list_of_all_globals;
42 static const int kDynamicInitGlobalsInitialCapacity = 512;
43 struct DynInitGlobal {
47 typedef InternalMmapVector<DynInitGlobal> VectorOfGlobals;
48 // Lazy-initialized and never deleted.
49 static VectorOfGlobals *dynamic_init_globals;
51 // We want to remember where a certain range of globals was registered.
52 struct GlobalRegistrationSite {
54 Global *g_first, *g_last;
56 typedef InternalMmapVector<GlobalRegistrationSite> GlobalRegistrationSiteVector;
57 static GlobalRegistrationSiteVector *global_registration_site_vector;
59 ALWAYS_INLINE void PoisonShadowForGlobal(const Global *g, u8 value) {
60 FastPoisonShadow(g->beg, g->size_with_redzone, value);
63 ALWAYS_INLINE void PoisonRedZones(const Global &g) {
64 uptr aligned_size = RoundUpTo(g.size, SHADOW_GRANULARITY);
65 FastPoisonShadow(g.beg + aligned_size, g.size_with_redzone - aligned_size,
66 kAsanGlobalRedzoneMagic);
67 if (g.size != aligned_size) {
68 FastPoisonShadowPartialRightRedzone(
69 g.beg + RoundDownTo(g.size, SHADOW_GRANULARITY),
70 g.size % SHADOW_GRANULARITY,
72 kAsanGlobalRedzoneMagic);
76 const uptr kMinimalDistanceFromAnotherGlobal = 64;
78 static bool IsAddressNearGlobal(uptr addr, const __asan_global &g) {
79 if (addr <= g.beg - kMinimalDistanceFromAnotherGlobal) return false;
80 if (addr >= g.beg + g.size_with_redzone) return false;
84 static void ReportGlobal(const Global &g, const char *prefix) {
86 "%s Global[%p]: beg=%p size=%zu/%zu name=%s module=%s dyn_init=%zu "
88 prefix, &g, (void *)g.beg, g.size, g.size_with_redzone, g.name,
89 g.module_name, g.has_dynamic_init, (void *)g.odr_indicator);
91 Report(" location (%p): name=%s[%p], %d %d\n", g.location,
92 g.location->filename, g.location->filename, g.location->line_no,
93 g.location->column_no);
97 static u32 FindRegistrationSite(const Global *g) {
98 mu_for_globals.CheckLocked();
99 CHECK(global_registration_site_vector);
100 for (uptr i = 0, n = global_registration_site_vector->size(); i < n; i++) {
101 GlobalRegistrationSite &grs = (*global_registration_site_vector)[i];
102 if (g >= grs.g_first && g <= grs.g_last)
108 int GetGlobalsForAddress(uptr addr, Global *globals, u32 *reg_sites,
110 if (!flags()->report_globals) return 0;
111 BlockingMutexLock lock(&mu_for_globals);
113 for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
114 const Global &g = *l->g;
115 if (flags()->report_globals >= 2)
116 ReportGlobal(g, "Search");
117 if (IsAddressNearGlobal(addr, g)) {
118 internal_memcpy(&globals[res], &g, sizeof(g));
120 reg_sites[res] = FindRegistrationSite(&g);
122 if (res == max_globals)
129 enum GlobalSymbolState {
134 // Check ODR violation for given global G via special ODR indicator. We use
135 // this method in case compiler instruments global variables through their
137 static void CheckODRViolationViaIndicator(const Global *g) {
138 // Instrumentation requests to skip ODR check.
139 if (g->odr_indicator == UINTPTR_MAX)
141 u8 *odr_indicator = reinterpret_cast<u8 *>(g->odr_indicator);
142 if (*odr_indicator == UNREGISTERED) {
143 *odr_indicator = REGISTERED;
146 // If *odr_indicator is DEFINED, some module have already registered
147 // externally visible symbol with the same name. This is an ODR violation.
148 for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
149 if (g->odr_indicator == l->g->odr_indicator &&
150 (flags()->detect_odr_violation >= 2 || g->size != l->g->size) &&
151 !IsODRViolationSuppressed(g->name))
152 ReportODRViolation(g, FindRegistrationSite(g),
153 l->g, FindRegistrationSite(l->g));
157 // Check ODR violation for given global G by checking if it's already poisoned.
158 // We use this method in case compiler doesn't use private aliases for global
160 static void CheckODRViolationViaPoisoning(const Global *g) {
161 if (__asan_region_is_poisoned(g->beg, g->size_with_redzone)) {
162 // This check may not be enough: if the first global is much larger
163 // the entire redzone of the second global may be within the first global.
164 for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
165 if (g->beg == l->g->beg &&
166 (flags()->detect_odr_violation >= 2 || g->size != l->g->size) &&
167 !IsODRViolationSuppressed(g->name))
168 ReportODRViolation(g, FindRegistrationSite(g),
169 l->g, FindRegistrationSite(l->g));
174 // Clang provides two different ways for global variables protection:
175 // it can poison the global itself or its private alias. In former
176 // case we may poison same symbol multiple times, that can help us to
177 // cheaply detect ODR violation: if we try to poison an already poisoned
178 // global, we have ODR violation error.
179 // In latter case, we poison each symbol exactly once, so we use special
180 // indicator symbol to perform similar check.
181 // In either case, compiler provides a special odr_indicator field to Global
182 // structure, that can contain two kinds of values:
183 // 1) Non-zero value. In this case, odr_indicator is an address of
184 // corresponding indicator variable for given global.
185 // 2) Zero. This means that we don't use private aliases for global variables
186 // and can freely check ODR violation with the first method.
188 // This routine chooses between two different methods of ODR violation
190 static inline bool UseODRIndicator(const Global *g) {
191 return g->odr_indicator > 0;
194 // Register a global variable.
195 // This function may be called more than once for every global
196 // so we store the globals in a map.
197 static void RegisterGlobal(const Global *g) {
199 if (flags()->report_globals >= 2)
200 ReportGlobal(*g, "Added");
201 CHECK(flags()->report_globals);
202 CHECK(AddrIsInMem(g->beg));
203 if (!AddrIsAlignedByGranularity(g->beg)) {
204 Report("The following global variable is not properly aligned.\n");
205 Report("This may happen if another global with the same name\n");
206 Report("resides in another non-instrumented module.\n");
207 Report("Or the global comes from a C file built w/o -fno-common.\n");
208 Report("In either case this is likely an ODR violation bug,\n");
209 Report("but AddressSanitizer can not provide more details.\n");
210 ReportODRViolation(g, FindRegistrationSite(g), g, FindRegistrationSite(g));
211 CHECK(AddrIsAlignedByGranularity(g->beg));
213 CHECK(AddrIsAlignedByGranularity(g->size_with_redzone));
214 if (flags()->detect_odr_violation) {
215 // Try detecting ODR (One Definition Rule) violation, i.e. the situation
216 // where two globals with the same name are defined in different modules.
217 if (UseODRIndicator(g))
218 CheckODRViolationViaIndicator(g);
220 CheckODRViolationViaPoisoning(g);
222 if (CanPoisonMemory())
224 ListOfGlobals *l = new(allocator_for_globals) ListOfGlobals;
226 l->next = list_of_all_globals;
227 list_of_all_globals = l;
228 if (g->has_dynamic_init) {
229 if (!dynamic_init_globals) {
230 dynamic_init_globals =
231 new (allocator_for_globals) VectorOfGlobals; // NOLINT
232 dynamic_init_globals->reserve(kDynamicInitGlobalsInitialCapacity);
234 DynInitGlobal dyn_global = { *g, false };
235 dynamic_init_globals->push_back(dyn_global);
239 static void UnregisterGlobal(const Global *g) {
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.
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;
260 void StopInitOrderChecking() {
261 BlockingMutexLock lock(&mu_for_globals);
262 if (!flags()->check_initialization_order || !dynamic_init_globals)
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.
275 static bool IsASCII(unsigned char c) { return /*0x00 <= c &&*/ c <= 0x7F; }
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;
286 return should_demangle ? Symbolizer::GetOrInit()->Demangle(name) : name;
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;
295 if (*(char *)(g.beg + g.size - 1) != '\0') return;
296 str->append(" '%s' is ascii string '%s'\n", MaybeDemangleGlobalName(g.name),
300 static const char *GlobalFilename(const __asan_global &g) {
301 const char *res = g.module_name;
302 // Prefer the filename from source location, if is available.
303 if (g.location) res = g.location->filename;
308 void PrintGlobalLocation(InternalScopedString *str, const __asan_global &g) {
309 str->append("%s", GlobalFilename(g));
310 if (!g.location) return;
311 if (g.location->line_no) str->append(":%d", g.location->line_no);
312 if (g.location->column_no) str->append(":%d", g.location->column_no);
315 } // namespace __asan
317 // ---------------------- Interface ---------------- {{{1
318 using namespace __asan; // NOLINT
321 // Apply __asan_register_globals to all globals found in the same loaded
322 // executable or shared library as `flag'. The flag tracks whether globals have
323 // already been registered or not for this image.
324 void __asan_register_image_globals(uptr *flag) {
327 AsanApplyToGlobals(__asan_register_globals, flag);
331 // This mirrors __asan_register_image_globals.
332 void __asan_unregister_image_globals(uptr *flag) {
335 AsanApplyToGlobals(__asan_unregister_globals, flag);
339 void __asan_register_elf_globals(uptr *flag, void *start, void *stop) {
342 CHECK_EQ(0, ((uptr)stop - (uptr)start) % sizeof(__asan_global));
343 __asan_global *globals_start = (__asan_global*)start;
344 __asan_global *globals_stop = (__asan_global*)stop;
345 __asan_register_globals(globals_start, globals_stop - globals_start);
349 void __asan_unregister_elf_globals(uptr *flag, void *start, void *stop) {
352 CHECK_EQ(0, ((uptr)stop - (uptr)start) % sizeof(__asan_global));
353 __asan_global *globals_start = (__asan_global*)start;
354 __asan_global *globals_stop = (__asan_global*)stop;
355 __asan_unregister_globals(globals_start, globals_stop - globals_start);
359 // Register an array of globals.
360 void __asan_register_globals(__asan_global *globals, uptr n) {
361 if (!flags()->report_globals) return;
362 GET_STACK_TRACE_MALLOC;
363 u32 stack_id = StackDepotPut(stack);
364 BlockingMutexLock lock(&mu_for_globals);
365 if (!global_registration_site_vector) {
366 global_registration_site_vector =
367 new (allocator_for_globals) GlobalRegistrationSiteVector; // NOLINT
368 global_registration_site_vector->reserve(128);
370 GlobalRegistrationSite site = {stack_id, &globals[0], &globals[n - 1]};
371 global_registration_site_vector->push_back(site);
372 if (flags()->report_globals >= 2) {
373 PRINT_CURRENT_STACK();
374 Printf("=== ID %d; %p %p\n", stack_id, &globals[0], &globals[n - 1]);
376 for (uptr i = 0; i < n; i++) {
377 if (SANITIZER_WINDOWS && globals[i].beg == 0) {
378 // The MSVC incremental linker may pad globals out to 256 bytes. As long
379 // as __asan_global is less than 256 bytes large and its size is a power
380 // of two, we can skip over the padding.
382 sizeof(__asan_global) < 256 &&
383 (sizeof(__asan_global) & (sizeof(__asan_global) - 1)) == 0,
384 "sizeof(__asan_global) incompatible with incremental linker padding");
385 // If these are padding bytes, the rest of the global should be zero.
386 CHECK(globals[i].size == 0 && globals[i].size_with_redzone == 0 &&
387 globals[i].name == nullptr && globals[i].module_name == nullptr &&
388 globals[i].odr_indicator == 0);
391 RegisterGlobal(&globals[i]);
394 // Poison the metadata. It should not be accessible to user code.
395 PoisonShadow(reinterpret_cast<uptr>(globals), n * sizeof(__asan_global),
396 kAsanGlobalRedzoneMagic);
399 // Unregister an array of globals.
400 // We must do this when a shared objects gets dlclosed.
401 void __asan_unregister_globals(__asan_global *globals, uptr n) {
402 if (!flags()->report_globals) return;
403 BlockingMutexLock lock(&mu_for_globals);
404 for (uptr i = 0; i < n; i++) {
405 if (SANITIZER_WINDOWS && globals[i].beg == 0) {
406 // Skip globals that look like padding from the MSVC incremental linker.
407 // See comment in __asan_register_globals.
410 UnregisterGlobal(&globals[i]);
413 // Unpoison the metadata.
414 PoisonShadow(reinterpret_cast<uptr>(globals), n * sizeof(__asan_global), 0);
417 // This method runs immediately prior to dynamic initialization in each TU,
418 // when all dynamically initialized globals are unpoisoned. This method
419 // poisons all global variables not defined in this TU, so that a dynamic
420 // initializer can only touch global variables in the same TU.
421 void __asan_before_dynamic_init(const char *module_name) {
422 if (!flags()->check_initialization_order ||
423 !CanPoisonMemory() ||
424 !dynamic_init_globals)
426 bool strict_init_order = flags()->strict_init_order;
429 BlockingMutexLock lock(&mu_for_globals);
430 if (flags()->report_globals >= 3)
431 Printf("DynInitPoison module: %s\n", module_name);
432 for (uptr i = 0, n = dynamic_init_globals->size(); i < n; ++i) {
433 DynInitGlobal &dyn_g = (*dynamic_init_globals)[i];
434 const Global *g = &dyn_g.g;
435 if (dyn_g.initialized)
437 if (g->module_name != module_name)
438 PoisonShadowForGlobal(g, kAsanInitializationOrderMagic);
439 else if (!strict_init_order)
440 dyn_g.initialized = true;
444 // This method runs immediately after dynamic initialization in each TU, when
445 // all dynamically initialized globals except for those defined in the current
446 // TU are poisoned. It simply unpoisons all dynamically initialized globals.
447 void __asan_after_dynamic_init() {
448 if (!flags()->check_initialization_order ||
449 !CanPoisonMemory() ||
450 !dynamic_init_globals)
453 BlockingMutexLock lock(&mu_for_globals);
454 // FIXME: Optionally report that we're unpoisoning globals from a module.
455 for (uptr i = 0, n = dynamic_init_globals->size(); i < n; ++i) {
456 DynInitGlobal &dyn_g = (*dynamic_init_globals)[i];
457 const Global *g = &dyn_g.g;
458 if (!dyn_g.initialized) {
459 // Unpoison the whole global.
460 PoisonShadowForGlobal(g, 0);
461 // Poison redzones back.