[lldb] Add IsFullyInitialized to DynamicLoader

On Darwin based systems, lldb will get notified by dyld before it itself
finished initializing, at which point it's not safe to call certain APIs
or SPIs. Add a method to the DynamicLoader to query that.

Differential revision: https://reviews.llvm.org/D99314

Author: JDevlieghere

lldb/include/lldb/Target/DynamicLoader.h

@@ -251,6 +251,14 @@ class DynamicLoader : public PluginInterface {
     return false;
   }
 
+  /// Return whether the dynamic loader is fully initialized and it's safe to
+  /// call its APIs.
+  ///
+  /// On some systems (e.g. Darwin based systems), lldb will get notified by
+  /// the dynamic loader before it itself finished initializing and it's not
+  /// safe to call certain APIs or SPIs.
+  virtual bool IsFullyInitialized() { return true; }
+
 protected:
   // Utility methods for derived classes
 
@@ -294,7 +302,7 @@ class DynamicLoader : public PluginInterface {
   // Read a pointer from memory at the given addr. Return LLDB_INVALID_ADDRESS
   // if the read fails.
   lldb::addr_t ReadPointer(lldb::addr_t addr);
-  
+
   // Calls into the Process protected method LoadOperatingSystemPlugin:
   void LoadOperatingSystemPlugin(bool flush);
 

lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.cpp

@@ -1114,6 +1114,12 @@ bool DynamicLoaderMacOSXDYLD::GetSharedCacheInformation(
   return false;
 }
 
+bool DynamicLoaderMacOSXDYLD::IsFullyInitialized() {
+  if (ReadAllImageInfosStructure())
+    return m_dyld_all_image_infos.libSystemInitialized;
+  return false;
+}
+
 void DynamicLoaderMacOSXDYLD::Initialize() {
   PluginManager::RegisterPlugin(GetPluginNameStatic(),
                                 GetPluginDescriptionStatic(), CreateInstance);

lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.h

@@ -68,6 +68,8 @@ class DynamicLoaderMacOSXDYLD : public lldb_private::DynamicLoaderDarwin {
 
   uint32_t GetPluginVersion() override;
 
+  bool IsFullyInitialized() override;
+
 protected:
   void PutToLog(lldb_private::Log *log) const;