1 //===-- asan_thread.h -------------------------------------------*- C++ -*-===//
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 // ASan-private header for asan_thread.cpp.
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef ASAN_THREAD_H
15 #define ASAN_THREAD_H
16 
17 #include "asan_allocator.h"
18 #include "asan_fake_stack.h"
19 #include "asan_internal.h"
20 #include "asan_stats.h"
21 #include "sanitizer_common/sanitizer_common.h"
22 #include "sanitizer_common/sanitizer_libc.h"
23 #include "sanitizer_common/sanitizer_thread_arg_retval.h"
24 #include "sanitizer_common/sanitizer_thread_registry.h"
25 
26 namespace __sanitizer {
27 struct DTLS;
28 }  // namespace __sanitizer
29 
30 namespace __asan {
31 
32 class AsanThread;
33 
34 // These objects are created for every thread and are never deleted,
35 // so we can find them by tid even if the thread is long dead.
36 class AsanThreadContext final : public ThreadContextBase {
37  public:
AsanThreadContext(int tid)38   explicit AsanThreadContext(int tid)
39       : ThreadContextBase(tid), announced(false),
40         destructor_iterations(GetPthreadDestructorIterations()), stack_id(0),
41         thread(nullptr) {}
42   bool announced;
43   u8 destructor_iterations;
44   u32 stack_id;
45   AsanThread *thread;
46 
47   void OnCreated(void *arg) override;
48   void OnFinished() override;
49 
50   struct CreateThreadContextArgs {
51     AsanThread *thread;
52     StackTrace *stack;
53   };
54 };
55 
56 // AsanThreadContext objects are never freed, so we need many of them.
57 COMPILER_CHECK(sizeof(AsanThreadContext) <= 256);
58 
59 #if defined(_MSC_VER) && !defined(__clang__)
60 // MSVC raises a warning about a nonstandard extension being used for the 0
61 // sized element in this array. Disable this for warn-as-error builds.
62 #  pragma warning(push)
63 #  pragma warning(disable : 4200)
64 #endif
65 
66 // AsanThread are stored in TSD and destroyed when the thread dies.
67 class AsanThread {
68  public:
69   template <typename T>
Create(const T & data,u32 parent_tid,StackTrace * stack,bool detached)70   static AsanThread *Create(const T &data, u32 parent_tid, StackTrace *stack,
71                             bool detached) {
72     return Create(&data, sizeof(data), parent_tid, stack, detached);
73   }
Create(u32 parent_tid,StackTrace * stack,bool detached)74   static AsanThread *Create(u32 parent_tid, StackTrace *stack, bool detached) {
75     return Create(nullptr, 0, parent_tid, stack, detached);
76   }
77   static void TSDDtor(void *tsd);
78   void Destroy();
79 
80   struct InitOptions;
81   void Init(const InitOptions *options = nullptr);
82 
83   void ThreadStart(tid_t os_id);
84   thread_return_t RunThread();
85 
86   uptr stack_top();
87   uptr stack_bottom();
88   uptr stack_size();
tls_begin()89   uptr tls_begin() { return tls_begin_; }
tls_end()90   uptr tls_end() { return tls_end_; }
dtls()91   DTLS *dtls() { return dtls_; }
tid()92   u32 tid() { return context_->tid; }
context()93   AsanThreadContext *context() { return context_; }
set_context(AsanThreadContext * context)94   void set_context(AsanThreadContext *context) { context_ = context; }
95 
96   struct StackFrameAccess {
97     uptr offset;
98     uptr frame_pc;
99     const char *frame_descr;
100   };
101   bool GetStackFrameAccessByAddr(uptr addr, StackFrameAccess *access);
102 
103   // Returns a pointer to the start of the stack variable's shadow memory.
104   uptr GetStackVariableShadowStart(uptr addr);
105 
106   bool AddrIsInStack(uptr addr);
107 
DeleteFakeStack(int tid)108   void DeleteFakeStack(int tid) {
109     if (!fake_stack_) return;
110     FakeStack *t = fake_stack_;
111     fake_stack_ = nullptr;
112     SetTLSFakeStack(nullptr);
113     t->Destroy(tid);
114   }
115 
116   void StartSwitchFiber(FakeStack **fake_stack_save, uptr bottom, uptr size);
117   void FinishSwitchFiber(FakeStack *fake_stack_save, uptr *bottom_old,
118                          uptr *size_old);
119 
get_fake_stack()120   FakeStack *get_fake_stack() {
121     if (atomic_load(&stack_switching_, memory_order_relaxed))
122       return nullptr;
123     if (reinterpret_cast<uptr>(fake_stack_) <= 1)
124       return nullptr;
125     return fake_stack_;
126   }
127 
get_or_create_fake_stack()128   FakeStack *get_or_create_fake_stack() {
129     if (atomic_load(&stack_switching_, memory_order_relaxed))
130       return nullptr;
131     if (reinterpret_cast<uptr>(fake_stack_) <= 1)
132       return AsyncSignalSafeLazyInitFakeStack();
133     return fake_stack_;
134   }
135 
136   // True is this thread is currently unwinding stack (i.e. collecting a stack
137   // trace). Used to prevent deadlocks on platforms where libc unwinder calls
138   // malloc internally. See PR17116 for more details.
isUnwinding()139   bool isUnwinding() const { return unwinding_; }
setUnwinding(bool b)140   void setUnwinding(bool b) { unwinding_ = b; }
141 
malloc_storage()142   AsanThreadLocalMallocStorage &malloc_storage() { return malloc_storage_; }
stats()143   AsanStats &stats() { return stats_; }
144 
extra_spill_area()145   void *extra_spill_area() { return &extra_spill_area_; }
146 
147   template <typename T>
GetStartData(T & data)148   void GetStartData(T &data) const {
149     GetStartData(&data, sizeof(data));
150   }
151 
152  private:
153   // NOTE: There is no AsanThread constructor. It is allocated
154   // via mmap() and *must* be valid in zero-initialized state.
155 
156   static AsanThread *Create(const void *start_data, uptr data_size,
157                             u32 parent_tid, StackTrace *stack, bool detached);
158 
159   void SetThreadStackAndTls(const InitOptions *options);
160 
161   void ClearShadowForThreadStackAndTLS();
162   FakeStack *AsyncSignalSafeLazyInitFakeStack();
163 
164   struct StackBounds {
165     uptr bottom;
166     uptr top;
167   };
168   StackBounds GetStackBounds() const;
169 
170   void GetStartData(void *out, uptr out_size) const;
171 
172   AsanThreadContext *context_;
173 
174   uptr stack_top_;
175   uptr stack_bottom_;
176   // these variables are used when the thread is about to switch stack
177   uptr next_stack_top_;
178   uptr next_stack_bottom_;
179   // true if switching is in progress
180   atomic_uint8_t stack_switching_;
181 
182   uptr tls_begin_;
183   uptr tls_end_;
184   DTLS *dtls_;
185 
186   FakeStack *fake_stack_;
187   AsanThreadLocalMallocStorage malloc_storage_;
188   AsanStats stats_;
189   bool unwinding_;
190   uptr extra_spill_area_;
191 
192   char start_data_[];
193 };
194 
195 #if defined(_MSC_VER) && !defined(__clang__)
196 #  pragma warning(pop)
197 #endif
198 
199 // Returns a single instance of registry.
200 ThreadRegistry &asanThreadRegistry();
201 ThreadArgRetval &asanThreadArgRetval();
202 
203 // Must be called under ThreadRegistryLock.
204 AsanThreadContext *GetThreadContextByTidLocked(u32 tid);
205 
206 // Get the current thread. May return 0.
207 AsanThread *GetCurrentThread();
208 void SetCurrentThread(AsanThread *t);
209 u32 GetCurrentTidOrInvalid();
210 AsanThread *FindThreadByStackAddress(uptr addr);
211 
212 // Used to handle fork().
213 void EnsureMainThreadIDIsCorrect();
214 } // namespace __asan
215 
216 #endif // ASAN_THREAD_H
217