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      1 //===-- asan_thread.cc ----------------------------------------------------===//
      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 // Thread-related code.
     13 //===----------------------------------------------------------------------===//
     14 #include "asan_allocator.h"
     15 #include "asan_interceptors.h"
     16 #include "asan_poisoning.h"
     17 #include "asan_stack.h"
     18 #include "asan_thread.h"
     19 #include "asan_mapping.h"
     20 #include "sanitizer_common/sanitizer_common.h"
     21 #include "sanitizer_common/sanitizer_placement_new.h"
     22 #include "sanitizer_common/sanitizer_stackdepot.h"
     23 #include "sanitizer_common/sanitizer_tls_get_addr.h"
     24 #include "lsan/lsan_common.h"
     25 
     26 namespace __asan {
     27 
     28 // AsanThreadContext implementation.
     29 
     30 struct CreateThreadContextArgs {
     31   AsanThread *thread;
     32   StackTrace *stack;
     33 };
     34 
     35 void AsanThreadContext::OnCreated(void *arg) {
     36   CreateThreadContextArgs *args = static_cast<CreateThreadContextArgs*>(arg);
     37   if (args->stack)
     38     stack_id = StackDepotPut(*args->stack);
     39   thread = args->thread;
     40   thread->set_context(this);
     41 }
     42 
     43 void AsanThreadContext::OnFinished() {
     44   // Drop the link to the AsanThread object.
     45   thread = 0;
     46 }
     47 
     48 // MIPS requires aligned address
     49 static ALIGNED(16) char thread_registry_placeholder[sizeof(ThreadRegistry)];
     50 static ThreadRegistry *asan_thread_registry;
     51 
     52 static BlockingMutex mu_for_thread_context(LINKER_INITIALIZED);
     53 static LowLevelAllocator allocator_for_thread_context;
     54 
     55 static ThreadContextBase *GetAsanThreadContext(u32 tid) {
     56   BlockingMutexLock lock(&mu_for_thread_context);
     57   return new(allocator_for_thread_context) AsanThreadContext(tid);
     58 }
     59 
     60 ThreadRegistry &asanThreadRegistry() {
     61   static bool initialized;
     62   // Don't worry about thread_safety - this should be called when there is
     63   // a single thread.
     64   if (!initialized) {
     65     // Never reuse ASan threads: we store pointer to AsanThreadContext
     66     // in TSD and can't reliably tell when no more TSD destructors will
     67     // be called. It would be wrong to reuse AsanThreadContext for another
     68     // thread before all TSD destructors will be called for it.
     69     asan_thread_registry = new(thread_registry_placeholder) ThreadRegistry(
     70         GetAsanThreadContext, kMaxNumberOfThreads, kMaxNumberOfThreads);
     71     initialized = true;
     72   }
     73   return *asan_thread_registry;
     74 }
     75 
     76 AsanThreadContext *GetThreadContextByTidLocked(u32 tid) {
     77   return static_cast<AsanThreadContext *>(
     78       asanThreadRegistry().GetThreadLocked(tid));
     79 }
     80 
     81 // AsanThread implementation.
     82 
     83 AsanThread *AsanThread::Create(thread_callback_t start_routine, void *arg,
     84                                u32 parent_tid, StackTrace *stack,
     85                                bool detached) {
     86   uptr PageSize = GetPageSizeCached();
     87   uptr size = RoundUpTo(sizeof(AsanThread), PageSize);
     88   AsanThread *thread = (AsanThread*)MmapOrDie(size, __func__);
     89   thread->start_routine_ = start_routine;
     90   thread->arg_ = arg;
     91   CreateThreadContextArgs args = { thread, stack };
     92   asanThreadRegistry().CreateThread(*reinterpret_cast<uptr *>(thread), detached,
     93                                     parent_tid, &args);
     94 
     95   return thread;
     96 }
     97 
     98 void AsanThread::TSDDtor(void *tsd) {
     99   AsanThreadContext *context = (AsanThreadContext*)tsd;
    100   VReport(1, "T%d TSDDtor\n", context->tid);
    101   if (context->thread)
    102     context->thread->Destroy();
    103 }
    104 
    105 void AsanThread::Destroy() {
    106   int tid = this->tid();
    107   VReport(1, "T%d exited\n", tid);
    108 
    109   malloc_storage().CommitBack();
    110   if (common_flags()->use_sigaltstack) UnsetAlternateSignalStack();
    111   asanThreadRegistry().FinishThread(tid);
    112   FlushToDeadThreadStats(&stats_);
    113   // We also clear the shadow on thread destruction because
    114   // some code may still be executing in later TSD destructors
    115   // and we don't want it to have any poisoned stack.
    116   ClearShadowForThreadStackAndTLS();
    117   DeleteFakeStack(tid);
    118   uptr size = RoundUpTo(sizeof(AsanThread), GetPageSizeCached());
    119   UnmapOrDie(this, size);
    120   DTLS_Destroy();
    121 }
    122 
    123 // We want to create the FakeStack lazyly on the first use, but not eralier
    124 // than the stack size is known and the procedure has to be async-signal safe.
    125 FakeStack *AsanThread::AsyncSignalSafeLazyInitFakeStack() {
    126   uptr stack_size = this->stack_size();
    127   if (stack_size == 0)  // stack_size is not yet available, don't use FakeStack.
    128     return 0;
    129   uptr old_val = 0;
    130   // fake_stack_ has 3 states:
    131   // 0   -- not initialized
    132   // 1   -- being initialized
    133   // ptr -- initialized
    134   // This CAS checks if the state was 0 and if so changes it to state 1,
    135   // if that was successful, it initializes the pointer.
    136   if (atomic_compare_exchange_strong(
    137       reinterpret_cast<atomic_uintptr_t *>(&fake_stack_), &old_val, 1UL,
    138       memory_order_relaxed)) {
    139     uptr stack_size_log = Log2(RoundUpToPowerOfTwo(stack_size));
    140     CHECK_LE(flags()->min_uar_stack_size_log, flags()->max_uar_stack_size_log);
    141     stack_size_log =
    142         Min(stack_size_log, static_cast<uptr>(flags()->max_uar_stack_size_log));
    143     stack_size_log =
    144         Max(stack_size_log, static_cast<uptr>(flags()->min_uar_stack_size_log));
    145     fake_stack_ = FakeStack::Create(stack_size_log);
    146     SetTLSFakeStack(fake_stack_);
    147     return fake_stack_;
    148   }
    149   return 0;
    150 }
    151 
    152 void AsanThread::Init() {
    153   fake_stack_ = 0;  // Will be initialized lazily if needed.
    154   CHECK_EQ(this->stack_size(), 0U);
    155   SetThreadStackAndTls();
    156   CHECK_GT(this->stack_size(), 0U);
    157   CHECK(AddrIsInMem(stack_bottom_));
    158   CHECK(AddrIsInMem(stack_top_ - 1));
    159   ClearShadowForThreadStackAndTLS();
    160   int local = 0;
    161   VReport(1, "T%d: stack [%p,%p) size 0x%zx; local=%p\n", tid(),
    162           (void *)stack_bottom_, (void *)stack_top_, stack_top_ - stack_bottom_,
    163           &local);
    164   AsanPlatformThreadInit();
    165 }
    166 
    167 thread_return_t AsanThread::ThreadStart(
    168     uptr os_id, atomic_uintptr_t *signal_thread_is_registered) {
    169   Init();
    170   asanThreadRegistry().StartThread(tid(), os_id, 0);
    171   if (signal_thread_is_registered)
    172     atomic_store(signal_thread_is_registered, 1, memory_order_release);
    173 
    174   if (common_flags()->use_sigaltstack) SetAlternateSignalStack();
    175 
    176   if (!start_routine_) {
    177     // start_routine_ == 0 if we're on the main thread or on one of the
    178     // OS X libdispatch worker threads. But nobody is supposed to call
    179     // ThreadStart() for the worker threads.
    180     CHECK_EQ(tid(), 0);
    181     return 0;
    182   }
    183 
    184   thread_return_t res = start_routine_(arg_);
    185 
    186   // On POSIX systems we defer this to the TSD destructor. LSan will consider
    187   // the thread's memory as non-live from the moment we call Destroy(), even
    188   // though that memory might contain pointers to heap objects which will be
    189   // cleaned up by a user-defined TSD destructor. Thus, calling Destroy() before
    190   // the TSD destructors have run might cause false positives in LSan.
    191   if (!SANITIZER_POSIX)
    192     this->Destroy();
    193 
    194   return res;
    195 }
    196 
    197 void AsanThread::SetThreadStackAndTls() {
    198   uptr tls_size = 0;
    199   GetThreadStackAndTls(tid() == 0, &stack_bottom_, &stack_size_, &tls_begin_,
    200                        &tls_size);
    201   stack_top_ = stack_bottom_ + stack_size_;
    202   tls_end_ = tls_begin_ + tls_size;
    203 
    204   int local;
    205   CHECK(AddrIsInStack((uptr)&local));
    206 }
    207 
    208 void AsanThread::ClearShadowForThreadStackAndTLS() {
    209   PoisonShadow(stack_bottom_, stack_top_ - stack_bottom_, 0);
    210   if (tls_begin_ != tls_end_)
    211     PoisonShadow(tls_begin_, tls_end_ - tls_begin_, 0);
    212 }
    213 
    214 bool AsanThread::GetStackFrameAccessByAddr(uptr addr,
    215                                            StackFrameAccess *access) {
    216   uptr bottom = 0;
    217   if (AddrIsInStack(addr)) {
    218     bottom = stack_bottom();
    219   } else if (has_fake_stack()) {
    220     bottom = fake_stack()->AddrIsInFakeStack(addr);
    221     CHECK(bottom);
    222     access->offset = addr - bottom;
    223     access->frame_pc = ((uptr*)bottom)[2];
    224     access->frame_descr = (const char *)((uptr*)bottom)[1];
    225     return true;
    226   }
    227   uptr aligned_addr = addr & ~(SANITIZER_WORDSIZE/8 - 1);  // align addr.
    228   u8 *shadow_ptr = (u8*)MemToShadow(aligned_addr);
    229   u8 *shadow_bottom = (u8*)MemToShadow(bottom);
    230 
    231   while (shadow_ptr >= shadow_bottom &&
    232          *shadow_ptr != kAsanStackLeftRedzoneMagic) {
    233     shadow_ptr--;
    234   }
    235 
    236   while (shadow_ptr >= shadow_bottom &&
    237          *shadow_ptr == kAsanStackLeftRedzoneMagic) {
    238     shadow_ptr--;
    239   }
    240 
    241   if (shadow_ptr < shadow_bottom) {
    242     return false;
    243   }
    244 
    245   uptr* ptr = (uptr*)SHADOW_TO_MEM((uptr)(shadow_ptr + 1));
    246   CHECK(ptr[0] == kCurrentStackFrameMagic);
    247   access->offset = addr - (uptr)ptr;
    248   access->frame_pc = ptr[2];
    249   access->frame_descr = (const char*)ptr[1];
    250   return true;
    251 }
    252 
    253 static bool ThreadStackContainsAddress(ThreadContextBase *tctx_base,
    254                                        void *addr) {
    255   AsanThreadContext *tctx = static_cast<AsanThreadContext*>(tctx_base);
    256   AsanThread *t = tctx->thread;
    257   if (!t) return false;
    258   if (t->AddrIsInStack((uptr)addr)) return true;
    259   if (t->has_fake_stack() && t->fake_stack()->AddrIsInFakeStack((uptr)addr))
    260     return true;
    261   return false;
    262 }
    263 
    264 AsanThread *GetCurrentThread() {
    265   AsanThreadContext *context =
    266       reinterpret_cast<AsanThreadContext *>(AsanTSDGet());
    267   if (!context) {
    268     if (SANITIZER_ANDROID) {
    269       // On Android, libc constructor is called _after_ asan_init, and cleans up
    270       // TSD. Try to figure out if this is still the main thread by the stack
    271       // address. We are not entirely sure that we have correct main thread
    272       // limits, so only do this magic on Android, and only if the found thread
    273       // is the main thread.
    274       AsanThreadContext *tctx = GetThreadContextByTidLocked(0);
    275       if (ThreadStackContainsAddress(tctx, &context)) {
    276         SetCurrentThread(tctx->thread);
    277         return tctx->thread;
    278       }
    279     }
    280     return 0;
    281   }
    282   return context->thread;
    283 }
    284 
    285 void SetCurrentThread(AsanThread *t) {
    286   CHECK(t->context());
    287   VReport(2, "SetCurrentThread: %p for thread %p\n", t->context(),
    288           (void *)GetThreadSelf());
    289   // Make sure we do not reset the current AsanThread.
    290   CHECK_EQ(0, AsanTSDGet());
    291   AsanTSDSet(t->context());
    292   CHECK_EQ(t->context(), AsanTSDGet());
    293 }
    294 
    295 u32 GetCurrentTidOrInvalid() {
    296   AsanThread *t = GetCurrentThread();
    297   return t ? t->tid() : kInvalidTid;
    298 }
    299 
    300 AsanThread *FindThreadByStackAddress(uptr addr) {
    301   asanThreadRegistry().CheckLocked();
    302   AsanThreadContext *tctx = static_cast<AsanThreadContext *>(
    303       asanThreadRegistry().FindThreadContextLocked(ThreadStackContainsAddress,
    304                                                    (void *)addr));
    305   return tctx ? tctx->thread : 0;
    306 }
    307 
    308 void EnsureMainThreadIDIsCorrect() {
    309   AsanThreadContext *context =
    310       reinterpret_cast<AsanThreadContext *>(AsanTSDGet());
    311   if (context && (context->tid == 0))
    312     context->os_id = GetTid();
    313 }
    314 
    315 __asan::AsanThread *GetAsanThreadByOsIDLocked(uptr os_id) {
    316   __asan::AsanThreadContext *context = static_cast<__asan::AsanThreadContext *>(
    317       __asan::asanThreadRegistry().FindThreadContextByOsIDLocked(os_id));
    318   if (!context) return 0;
    319   return context->thread;
    320 }
    321 }  // namespace __asan
    322 
    323 // --- Implementation of LSan-specific functions --- {{{1
    324 namespace __lsan {
    325 bool GetThreadRangesLocked(uptr os_id, uptr *stack_begin, uptr *stack_end,
    326                            uptr *tls_begin, uptr *tls_end,
    327                            uptr *cache_begin, uptr *cache_end) {
    328   __asan::AsanThread *t = __asan::GetAsanThreadByOsIDLocked(os_id);
    329   if (!t) return false;
    330   *stack_begin = t->stack_bottom();
    331   *stack_end = t->stack_top();
    332   *tls_begin = t->tls_begin();
    333   *tls_end = t->tls_end();
    334   // ASan doesn't keep allocator caches in TLS, so these are unused.
    335   *cache_begin = 0;
    336   *cache_end = 0;
    337   return true;
    338 }
    339 
    340 void ForEachExtraStackRange(uptr os_id, RangeIteratorCallback callback,
    341                             void *arg) {
    342   __asan::AsanThread *t = __asan::GetAsanThreadByOsIDLocked(os_id);
    343   if (t && t->has_fake_stack())
    344     t->fake_stack()->ForEachFakeFrame(callback, arg);
    345 }
    346 
    347 void LockThreadRegistry() {
    348   __asan::asanThreadRegistry().Lock();
    349 }
    350 
    351 void UnlockThreadRegistry() {
    352   __asan::asanThreadRegistry().Unlock();
    353 }
    354 
    355 void EnsureMainThreadIDIsCorrect() {
    356   __asan::EnsureMainThreadIDIsCorrect();
    357 }
    358 }  // namespace __lsan
    359