Automerge: [lldb] Add function to tell if a section is a GOT section (#165936)

A global offset table is a section that holds the address of functions
that are dynamically linked. The Swift plugin needs to know if sections
are a global offset table or not.

Author: augusto2112

lldb/include/lldb/Core/Section.h

@@ -273,6 +273,9 @@ class Section : public std::enable_shared_from_this<Section>,
   /// return true.
   bool ContainsOnlyDebugInfo() const;
 
+  /// Returns true if this is a global offset table section.
+  bool IsGOTSection() const;
+
 protected:
   ObjectFile *m_obj_file;   // The object file that data for this section should
                             // be read from

lldb/include/lldb/Symbol/ObjectFile.h

@@ -758,6 +758,12 @@ class ObjectFile : public std::enable_shared_from_this<ObjectFile>,
     return false;
   }
 
+  /// Returns true if the section is a global offset table section.
+  virtual bool IsGOTSection(const lldb_private::Section &section) const {
+    assert(section.GetObjectFile() == this && "Wrong object file!");
+    return false;
+  }
+
   /// Get a hash that can be used for caching object file releated information.
   ///
   /// Data for object files can be cached between runs of debug sessions and

lldb/source/Core/Section.cpp

@@ -471,6 +471,10 @@ bool Section::ContainsOnlyDebugInfo() const {
   return false;
 }
 
+bool Section::IsGOTSection() const {
+  return GetObjectFile()->IsGOTSection(*this);
+}
+
 #pragma mark SectionList
 
 SectionList &SectionList::operator=(const SectionList &rhs) {

lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp

@@ -5936,6 +5936,20 @@ Section *ObjectFileMachO::GetMachHeaderSection() {
   return nullptr;
 }
 
+bool ObjectFileMachO::IsGOTSection(const lldb_private::Section &section) const {
+  assert(section.GetObjectFile() == this && "Wrong object file!");
+  SectionSP segment = section.GetParent();
+  if (!segment)
+    return false;
+
+  const bool is_data_const_got =
+      segment->GetName() == "__DATA_CONST" && section.GetName() == "__got";
+  const bool is_auth_const_ptr =
+      segment->GetName() == "__AUTH_CONST" &&
+      (section.GetName() == "__auth_got" || section.GetName() == "__auth_ptr");
+  return is_data_const_got || is_auth_const_ptr;
+}
+
 bool ObjectFileMachO::SectionIsLoadable(const Section *section) {
   if (!section)
     return false;

lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.h

@@ -162,6 +162,8 @@ class ObjectFileMachO : public lldb_private::ObjectFile {
 
   lldb_private::Section *GetMachHeaderSection();
 
+  bool IsGOTSection(const lldb_private::Section &section) const override;
+
   // PluginInterface protocol
   llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }