[lldb] Support shared cache relative objc method types (#163663)

Support the types and name field in the relative method list to be
relative to a buffer in the shared cache, not relative to the field in
the method list itself.

A new magic bit, 0x20000000, is attached to method lists where the types
are encoded in this way. This is covered by the existing tests when
running against a shared cache that uses this encoding.

rdar://147545351

Author: JDevlieghere

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCClassDescriptorV2.cpp

@@ -260,6 +260,7 @@ bool ClassDescriptorV2::method_list_t::Read(Process *process,
   uint32_t entsize = extractor.GetU32_unchecked(&cursor);
   m_is_small = (entsize & 0x80000000) != 0;
   m_has_direct_selector = (entsize & 0x40000000) != 0;
+  m_has_relative_types = (entsize & 0x20000000) != 0;
   m_entsize = entsize & 0xfffc;
   m_count = extractor.GetU32_unchecked(&cursor);
   m_first_ptr = addr + cursor;
@@ -269,8 +270,9 @@ bool ClassDescriptorV2::method_list_t::Read(Process *process,
 
 llvm::SmallVector<ClassDescriptorV2::method_t, 0>
 ClassDescriptorV2::ReadMethods(llvm::ArrayRef<lldb::addr_t> addresses,
-                               lldb::addr_t relative_selector_base_addr,
-                               bool is_small, bool has_direct_sel) const {
+                               lldb::addr_t relative_string_base_addr,
+                               bool is_small, bool has_direct_sel,
+                               bool has_relative_types) const {
   lldb_private::Process *process = m_runtime.GetProcess();
   if (!process)
     return {};
@@ -297,17 +299,18 @@ ClassDescriptorV2::ReadMethods(llvm::ArrayRef<lldb::addr_t> addresses,
                             process->GetByteOrder(),
                             process->GetAddressByteSize());
     methods.push_back(method_t());
-    methods.back().Read(extractor, process, addr, relative_selector_base_addr,
-                        is_small, has_direct_sel);
+    methods.back().Read(extractor, process, addr, relative_string_base_addr,
+                        is_small, has_direct_sel, has_relative_types);
   }
 
   return methods;
 }
 
 bool ClassDescriptorV2::method_t::Read(DataExtractor &extractor,
                                        Process *process, lldb::addr_t addr,
-                                       lldb::addr_t relative_selector_base_addr,
-                                       bool is_small, bool has_direct_sel) {
+                                       lldb::addr_t relative_string_base_addr,
+                                       bool is_small, bool has_direct_sel,
+                                       bool has_relative_types) {
   lldb::offset_t cursor = 0;
 
   if (is_small) {
@@ -323,10 +326,13 @@ bool ClassDescriptorV2::method_t::Read(DataExtractor &extractor,
       m_name_ptr = process->ReadPointerFromMemory(m_name_ptr, error);
       if (error.Fail())
         return false;
-    } else if (relative_selector_base_addr != LLDB_INVALID_ADDRESS) {
-      m_name_ptr = relative_selector_base_addr + nameref_offset;
+    } else if (relative_string_base_addr != LLDB_INVALID_ADDRESS) {
+      m_name_ptr = relative_string_base_addr + nameref_offset;
     }
-    m_types_ptr = addr + 4 + types_offset;
+    if (has_relative_types)
+      m_types_ptr = relative_string_base_addr + types_offset;
+    else
+      m_types_ptr = addr + 4 + types_offset;
     m_imp_ptr = addr + 8 + imp_offset;
   } else {
     m_name_ptr = extractor.GetAddress_unchecked(&cursor);
@@ -481,7 +487,8 @@ bool ClassDescriptorV2::ProcessMethodList(
 
   llvm::SmallVector<method_t, 0> methods =
       ReadMethods(addresses, m_runtime.GetRelativeSelectorBaseAddr(),
-                  method_list.m_is_small, method_list.m_has_direct_selector);
+                  method_list.m_is_small, method_list.m_has_direct_selector,
+                  method_list.m_has_relative_types);
 
   for (const auto &method : methods)
     if (instance_method_func(method.m_name.c_str(), method.m_types.c_str()))

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCClassDescriptorV2.h

@@ -143,6 +143,7 @@ class ClassDescriptorV2 : public ObjCLanguageRuntime::ClassDescriptor {
     uint16_t m_entsize;
     bool m_is_small;
     bool m_has_direct_selector;
+    bool m_has_relative_types;
     uint32_t m_count;
     lldb::addr_t m_first_ptr;
 
@@ -173,14 +174,14 @@ class ClassDescriptorV2 : public ObjCLanguageRuntime::ClassDescriptor {
     }
 
     bool Read(DataExtractor &extractor, Process *process, lldb::addr_t addr,
-              lldb::addr_t relative_selector_base_addr, bool is_small,
-              bool has_direct_sel);
+              lldb::addr_t relative_string_base_addr, bool is_small,
+              bool has_direct_sel, bool has_relative_types);
   };
 
   llvm::SmallVector<method_t, 0>
   ReadMethods(llvm::ArrayRef<lldb::addr_t> addresses,
-              lldb::addr_t relative_selector_base_addr, bool is_small,
-              bool has_direct_sel) const;
+              lldb::addr_t relative_string_base_addr, bool is_small,
+              bool has_direct_sel, bool has_relative_types) const;
 
   struct ivar_list_t {
     uint32_t m_entsize;