[NFC][asan] Split fake_stack() into two funcions

compiler-rt/lib/asan/asan_fake_stack.cpp

@@ -187,7 +187,7 @@ void SetTLSFakeStack(FakeStack *fs) { }
 static FakeStack *GetFakeStack() {
   AsanThread *t = GetCurrentThread();
   if (!t) return nullptr;
-  return t->fake_stack();
+  return t->get_or_create_fake_stack();
 }
 
 static FakeStack *GetFakeStackFast() {

compiler-rt/lib/asan/asan_rtl.cpp

@@ -13,6 +13,7 @@
 
 #include "asan_activation.h"
 #include "asan_allocator.h"
+#include "asan_fake_stack.h"
 #include "asan_interceptors.h"
 #include "asan_interface_internal.h"
 #include "asan_internal.h"
@@ -586,8 +587,12 @@ static void UnpoisonDefaultStack() {
 
 static void UnpoisonFakeStack() {
   AsanThread *curr_thread = GetCurrentThread();
-  if (curr_thread && curr_thread->has_fake_stack())
-    curr_thread->fake_stack()->HandleNoReturn();
+  if (!curr_thread)
+    return;
+  FakeStack *stack = curr_thread->get_fake_stack();
+  if (!stack)
+    return;
+  stack->HandleNoReturn();
 }
 
 }  // namespace __asan

compiler-rt/lib/asan/asan_thread.cpp

@@ -339,8 +339,8 @@ bool AsanThread::GetStackFrameAccessByAddr(uptr addr,
   uptr bottom = 0;
   if (AddrIsInStack(addr)) {
     bottom = stack_bottom();
-  } else if (has_fake_stack()) {
-    bottom = fake_stack()->AddrIsInFakeStack(addr);
+  } else if (FakeStack *fake_stack = get_fake_stack()) {
+    bottom = fake_stack->AddrIsInFakeStack(addr);
     CHECK(bottom);
     access->offset = addr - bottom;
     access->frame_pc = ((uptr*)bottom)[2];
@@ -380,8 +380,8 @@ uptr AsanThread::GetStackVariableShadowStart(uptr addr) {
   uptr bottom = 0;
   if (AddrIsInStack(addr)) {
     bottom = stack_bottom();
-  } else if (has_fake_stack()) {
-    bottom = fake_stack()->AddrIsInFakeStack(addr);
+  } else if (FakeStack *fake_stack = get_fake_stack()) {
+    bottom = fake_stack->AddrIsInFakeStack(addr);
     if (bottom == 0) {
       return 0;
     }
@@ -415,9 +415,10 @@ static bool ThreadStackContainsAddress(ThreadContextBase *tctx_base,
     return false;
   if (t->AddrIsInStack((uptr)addr))
     return true;
-  if (t->has_fake_stack() && t->fake_stack()->AddrIsInFakeStack((uptr)addr))
-    return true;
-  return false;
+  FakeStack *fake_stack = t->get_fake_stack();
+  if (!fake_stack)
+    return false;
+  return fake_stack->AddrIsInFakeStack((uptr)addr);
 }
 
 AsanThread *GetCurrentThread() {
@@ -505,8 +506,12 @@ void GetAllThreadAllocatorCachesLocked(InternalMmapVector<uptr> *caches) {}
 void ForEachExtraStackRange(tid_t os_id, RangeIteratorCallback callback,
                             void *arg) {
   __asan::AsanThread *t = __asan::GetAsanThreadByOsIDLocked(os_id);
-  if (t && t->has_fake_stack())
-    t->fake_stack()->ForEachFakeFrame(callback, arg);
+  if (!t)
+    return;
+  __asan::FakeStack *fake_stack = t->get_fake_stack();
+  if (!fake_stack)
+    return;
+  fake_stack->ForEachFakeFrame(callback, arg);
 }
 
 void LockThreadRegistry() {

compiler-rt/lib/asan/asan_thread.h

@@ -104,17 +104,18 @@ class AsanThread {
   void FinishSwitchFiber(FakeStack *fake_stack_save, uptr *bottom_old,
                          uptr *size_old);
 
-  bool has_fake_stack() {
-    return !atomic_load(&stack_switching_, memory_order_relaxed) &&
-           (reinterpret_cast<uptr>(fake_stack_) > 1);
-  }
-
-  FakeStack *fake_stack() {
-    if (!__asan_option_detect_stack_use_after_return)
-      return nullptr;
+  FakeStack *get_fake_stack() {
     if (atomic_load(&stack_switching_, memory_order_relaxed))
       return nullptr;
-    if (!has_fake_stack())
+    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_;
   }