Add a final fallback technique to the old Darwin dynamic loader plugin to find the dyld_all_image_infos structure

[jasonmolenda]

Summary

When lldb is running on a userland corefile (the only case where DynamicLoaderMacOSX is still used today), lldb finds dyld in the corefile by exhaustive search, then reads the symbol table in the corefile to find the "dyld_all_image_infos" symbol. Using this object in the corefile, we can find the filepaths & load addresses of all other binaries.

This patch adds an additional fallback if we can't find the symbol name "dyld_all_image_infos" - by looking for the named section in dyld that is used specifically to identify this object. It is only used after the two function names we try have failed, at the point where we have no other possible ways to find the dyld_all_image_infos object in the corefile.

[JDevlieghere]

LGTM

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

if (m_dyld.header.filetype == llvm::MachO::MH_DYLINKER) {
         if (!symbol) {
           symbol = dyld_module_sp->FindFirstSymbolWithNameAndType(
               g_new_dyld_all_image_infos, eSymbolTypeData);
         }
         if (symbol)
           m_dyld_all_image_infos_addr = symbol->GetLoadAddress(&target);
       }
 
+      if (m_dyld_all_image_infos_addr == LLDB_INVALID_ADDRESS) {
+        ConstString g_sect_name("__all_image_info");
+        SectionSP dyld_aii_section_sp =
+            dyld_module_sp->GetSectionList()->FindSectionByName(g_sect_name);
+        if (dyld_aii_section_sp) {
+          Address dyld_aii_addr(dyld_aii_section_sp, 0);
+          m_dyld_all_image_infos_addr = dyld_aii_addr.GetLoadAddress(&target);
+        }
+      }
+
       // Update all image infos
       InitializeFromAllImageInfos();
 
       // If we didn't have an executable before, but now we do, then the dyld
       // module shared pointer might be unique and we may need to add it again
       // (since Target::SetExecutableModule() will clear the images). So append
       // the dyld module back to the list if it is
       /// unique!