[asan] Add argument to allow fake stack to be initialized during thread init

[waltl]

Summary

This will be used on RTEMS, where we prefer to allocate the memory up
front, rather than on first use which may be in a context
(i.e. interrupt handler) that is unable to allocate memory.

[kcc]

What if we try to just always call AsyncSignalSafeLazyInitFakeStack here?
There used to be a reason why this was done lazily, but I don't remember if we still have that reason.

[waltl]

In D46467#1088573, @kcc wrote:

What if we try to just always call AsyncSignalSafeLazyInitFakeStack here?
There used to be a reason why this was done lazily, but I don't remember if we still have that reason.

That would be great. I can prepare a commit for that.

[waltl]

In D46467#1090580, @waltl wrote:

In D46467#1088573, @kcc wrote:

What if we try to just always call AsyncSignalSafeLazyInitFakeStack here?
There used to be a reason why this was done lazily, but I don't remember if we still have that reason.

That would be great. I can prepare a commit for that.

See https://reviews.llvm.org/D46626.

[waltl]

Obsolete.

compiler-rt/lib/asan/asan_thread.h

 class AsanThread {
  public:
   static AsanThread *Create(thread_callback_t start_routine, void *arg,
                             u32 parent_tid, StackTrace *stack, bool detached);
   static void TSDDtor(void *tsd);
   void Destroy();
 
   struct InitOptions;
-  void Init(const InitOptions *options = nullptr);
+  void Init(const InitOptions *options = nullptr, bool init_fake_stack = false);
 
   thread_return_t ThreadStart(tid_t os_id,
                               atomic_uintptr_t *signal_thread_is_registered);
 
   uptr stack_top();
   uptr stack_bottom();
   uptr stack_size();
   uptr tls_begin() { return tls_begin_; }

compiler-rt/lib/asan/asan_thread.cc

stack_size_log =
         Max(stack_size_log, static_cast<uptr>(flags()->min_uar_stack_size_log));
     fake_stack_ = FakeStack::Create(stack_size_log);
     SetTLSFakeStack(fake_stack_);
     return fake_stack_;
   }
   return nullptr;
 }
 
-void AsanThread::Init(const InitOptions *options) {
+void AsanThread::Init(const InitOptions *options, bool init_fake_stack) {
   next_stack_top_ = next_stack_bottom_ = 0;
   atomic_store(&stack_switching_, false, memory_order_release);
-  fake_stack_ = nullptr;  // Will be initialized lazily if needed.
+  fake_stack_ = nullptr;  // Will be initialized below, or lazily if needed.
   CHECK_EQ(this->stack_size(), 0U);
   SetThreadStackAndTls(options);
   CHECK_GT(this->stack_size(), 0U);
   CHECK(AddrIsInMem(stack_bottom_));
   CHECK(AddrIsInMem(stack_top_ - 1));
   ClearShadowForThreadStackAndTLS();
+  if (__asan_option_detect_stack_use_after_return && init_fake_stack)
+    AsyncSignalSafeLazyInitFakeStack();
   int local = 0;
   VReport(1, "T%d: stack [%p,%p) size 0x%zx; local=%p\n", tid(),
           (void *)stack_bottom_, (void *)stack_top_, stack_top_ - stack_bottom_,
           &local);
 }
 
 // Fuchsia and RTEMS don't use ThreadStart.
 // asan_fuchsia.c/asan_rtems.c define CreateMainThread and