lib/asan/asan_thread.h

//===-- asan_thread.h -------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is a part of AddressSanitizer, an address sanity checker.
//
// ASan-private header for asan_thread.cpp.
//===----------------------------------------------------------------------===//

#ifndef ASAN_THREAD_H
#define ASAN_THREAD_H

#include "asan_allocator.h"
#include "asan_fake_stack.h"
#include "asan_internal.h"
#include "asan_stats.h"
#include "sanitizer_common/sanitizer_common.h"
#include "sanitizer_common/sanitizer_libc.h"
#include "sanitizer_common/sanitizer_thread_arg_retval.h"
#include "sanitizer_common/sanitizer_thread_registry.h"

namespace __sanitizer {
struct DTLS;
}  // namespace __sanitizer

namespace __asan {

class AsanThread;

// These objects are created for every thread and are never deleted,
// so we can find them by tid even if the thread is long dead.
class AsanThreadContext final : public ThreadContextBase {
 public:
  explicit AsanThreadContext(int tid)
      : ThreadContextBase(tid), announced(false),
        destructor_iterations(GetPthreadDestructorIterations()), stack_id(0),
        thread(nullptr) {}
  bool announced;
  u8 destructor_iterations;
  u32 stack_id;
  AsanThread *thread;

  void OnCreated(void *arg) override;
  void OnFinished() override;

  struct CreateThreadContextArgs {
    AsanThread *thread;
    StackTrace *stack;
  };
};

// AsanThreadContext objects are never freed, so we need many of them.
COMPILER_CHECK(sizeof(AsanThreadContext) <= 256);

#if defined(_MSC_VER) && !defined(__clang__)
// MSVC raises a warning about a nonstandard extension being used for the 0
// sized element in this array. Disable this for warn-as-error builds.
#  pragma warning(push)
#  pragma warning(disable : 4200)
#endif

// AsanThread are stored in TSD and destroyed when the thread dies.
class AsanThread {
 public:
  template <typename T>
  static AsanThread *Create(const T &data, u32 parent_tid, StackTrace *stack,
                            bool detached) {
    return Create(&data, sizeof(data), parent_tid, stack, detached);
  }
  static AsanThread *Create(u32 parent_tid, StackTrace *stack, bool detached) {
    return Create(nullptr, 0, parent_tid, stack, detached);
  }
  static void TSDDtor(void *tsd);
  void Destroy();

  struct InitOptions;
  void Init(const InitOptions *options = nullptr);

  void ThreadStart(tid_t os_id);
  thread_return_t RunThread();

  uptr stack_top();
  uptr stack_bottom();
  uptr stack_size();
  uptr tls_begin() { return tls_begin_; }
  uptr tls_end() { return tls_end_; }
  DTLS *dtls() { return dtls_; }
  u32 tid() { return context_->tid; }
  AsanThreadContext *context() { return context_; }
  void set_context(AsanThreadContext *context) { context_ = context; }

  struct StackFrameAccess {
    uptr offset;
    uptr frame_pc;
    const char *frame_descr;
  };
  bool GetStackFrameAccessByAddr(uptr addr, StackFrameAccess *access);

  // Returns a pointer to the start of the stack variable's shadow memory.
  uptr GetStackVariableShadowStart(uptr addr);

  bool AddrIsInStack(uptr addr);

  void DeleteFakeStack(int tid) {
    if (!fake_stack_) return;
    FakeStack *t = fake_stack_;
    fake_stack_ = nullptr;
    SetTLSFakeStack(nullptr);
    t->Destroy(tid);
  }

  void StartSwitchFiber(FakeStack **fake_stack_save, uptr bottom, uptr size);
  void FinishSwitchFiber(FakeStack *fake_stack_save, uptr *bottom_old,
                         uptr *size_old);

  FakeStack *get_fake_stack() {
    if (atomic_load(&stack_switching_, memory_order_relaxed))
      return nullptr;
    if (reinterpret_cast<uptr>(fake_stack_) <= 1)
      return nullptr;
    return fake_stack_;
  }

  FakeStack *get_or_create_fake_stack() {
    if (atomic_load(&stack_switching_, memory_order_relaxed))
      return nullptr;
    if (reinterpret_cast<uptr>(fake_stack_) <= 1)
      return AsyncSignalSafeLazyInitFakeStack();
    return fake_stack_;
  }

  // True is this thread is currently unwinding stack (i.e. collecting a stack
  // trace). Used to prevent deadlocks on platforms where libc unwinder calls
  // malloc internally. See PR17116 for more details.
  bool isUnwinding() const { return unwinding_; }
  void setUnwinding(bool b) { unwinding_ = b; }

  AsanThreadLocalMallocStorage &malloc_storage() { return malloc_storage_; }
  AsanStats &stats() { return stats_; }

  void *extra_spill_area() { return &extra_spill_area_; }

  template <typename T>
  void GetStartData(T &data) const {
    GetStartData(&data, sizeof(data));
  }

 private:
  // NOTE: There is no AsanThread constructor. It is allocated
  // via mmap() and *must* be valid in zero-initialized state.

  static AsanThread *Create(const void *start_data, uptr data_size,
                            u32 parent_tid, StackTrace *stack, bool detached);

  void SetThreadStackAndTls(const InitOptions *options);

  void ClearShadowForThreadStackAndTLS();
  FakeStack *AsyncSignalSafeLazyInitFakeStack();

  struct StackBounds {
    uptr bottom;
    uptr top;
  };
  StackBounds GetStackBounds() const;

  void GetStartData(void *out, uptr out_size) const;

  AsanThreadContext *context_;

  uptr stack_top_;
  uptr stack_bottom_;
  // these variables are used when the thread is about to switch stack
  uptr next_stack_top_;
  uptr next_stack_bottom_;
  // true if switching is in progress
  atomic_uint8_t stack_switching_;

  uptr tls_begin_;
  uptr tls_end_;
  DTLS *dtls_;

  FakeStack *fake_stack_;
  AsanThreadLocalMallocStorage malloc_storage_;
  AsanStats stats_;
  bool unwinding_;
  uptr extra_spill_area_;

  char start_data_[];
};

#if defined(_MSC_VER) && !defined(__clang__)
#  pragma warning(pop)
#endif

// Returns a single instance of registry.
ThreadRegistry &asanThreadRegistry();
ThreadArgRetval &asanThreadArgRetval();

// Must be called under ThreadRegistryLock.
AsanThreadContext *GetThreadContextByTidLocked(u32 tid);

// Get the current thread. May return 0.
AsanThread *GetCurrentThread();
void SetCurrentThread(AsanThread *t);
u32 GetCurrentTidOrInvalid();
AsanThread *FindThreadByStackAddress(uptr addr);

// Used to handle fork().
void EnsureMainThreadIDIsCorrect();
} // namespace __asan

#endif // ASAN_THREAD_H