[RemoteMirror] Only look through Task wait adapters when there's a dependency record.

When the RunJob pointer is set to adapters, we try to get the "real" run pointer from the context. However, there are cases where the context can be a dangling pointer, when the task has finished with it but hasn't reset the pointer to anything else. For cases where that can happen, the context is legitimate only when there's a dependency record. Check for a dependency record before trying to read the context in those cases.

In most uses this will fail gracefully or return a garbage run pointer, but swift-reflection-test uses an in-process memory reader which can crash when trying to chase this pointer, resulting in test failures.

rdar://149252404

Author: mikeash

include/swift/RemoteInspection/ReflectionContext.h

@@ -1929,12 +1929,17 @@ class ReflectionContext
                 Fptr == target_task_wait_throwing_resume_adapter) ||
                (target_task_future_wait_resume_adapter &&
                 Fptr == target_task_future_wait_resume_adapter)) {
-      auto ContextBytes = getReader().readBytes(RemoteAddress(ResumeContextPtr),
-                                                sizeof(AsyncContext<Runtime>));
-      if (ContextBytes) {
-        auto ContextPtr =
-            reinterpret_cast<const AsyncContext<Runtime> *>(ContextBytes.get());
-        return stripSignedPointer(ContextPtr->ResumeParent);
+      // It's only safe to look through these adapters when there's a dependency
+      // record. If there isn't a dependency record, then the task was resumed
+      // and the pointers are potentially stale.
+      if (AsyncTaskObj->PrivateStorage.DependencyRecord) {
+        auto ContextBytes = getReader().readBytes(
+            RemoteAddress(ResumeContextPtr), sizeof(AsyncContext<Runtime>));
+        if (ContextBytes) {
+          auto ContextPtr = reinterpret_cast<const AsyncContext<Runtime> *>(
+              ContextBytes.get());
+          return stripSignedPointer(ContextPtr->ResumeParent);
+        }
       }
     }
 

include/swift/RemoteInspection/RuntimeInternals.h

@@ -82,8 +82,7 @@ template <typename Runtime>
 struct StackAllocator {
   typename Runtime::StoredPointer LastAllocation;
   typename Runtime::StoredPointer FirstSlab;
-  int32_t NumAllocatedSlabs;
-  bool FirstSlabIsPreallocated;
+  int32_t NumAllocatedSlabsAndFirstSlabIsPreallocated;
 
   struct Slab {
     typename Runtime::StoredPointer Metadata;
@@ -123,7 +122,8 @@ struct AsyncTaskPrivateStorage {
   StackAllocator<Runtime> Allocator;
   typename Runtime::StoredPointer Local;
   uint32_t Id;
-  uint32_t BasePriority;
+  typename Runtime::StoredSize BasePriority;
+  typename Runtime::StoredPointer DependencyRecord;
 };
 
 template <typename Runtime, typename ActiveTaskStatus>