Search for kext variants is searching from parent directory when it should not be

[jasonmolenda]

Summary

There's a small perf issue after the changes to r334205; the patch is intended to search all the executables in a kext bundle to discover variants, e.g.

/System/Library/Extensions/AppleUSB.kext

everything under the AppleUSB.kext subdir should be searched. But the patch used the FileSpec's GetDirectory method, so we ended up recursively searching all the kexts in the parent directory.

Functionally, these are equivalent - recursively searching from the parent dir will yield the same result because we require a binary's UUID match before we use it. But it has a high performance cost if we search from the wrong base directory.

rdar://problem/41227170

[JDevlieghere]

Thanks Jason, good catch!

lldb/trunk/source/Plugins/Platform/MacOSX/PlatformDarwinKernel.h

GetKernelsAndKextsInDirectoryNoRecursion(
       const lldb_private::FileSpec &file_spec);
 
   static lldb_private::FileSpec::EnumerateDirectoryResult
   GetKernelsAndKextsInDirectoryHelper(void *baton, llvm::sys::fs::file_type ft,
                                       const lldb_private::FileSpec &file_spec,
                                       bool recurse);
 
   static std::vector<lldb_private::FileSpec>
-  SearchForExecutablesRecursively(const lldb_private::ConstString &dir);
+  SearchForExecutablesRecursively(const std::string &dir);
 
   static void AddKextToMap(PlatformDarwinKernel *thisp,
                            const lldb_private::FileSpec &file_spec);
 
   // Returns true if there is a .dSYM bundle next to the kext, or next to the
   // binary inside the kext.
   static bool
   KextHasdSYMSibling(const lldb_private::FileSpec &kext_bundle_filepath);

lldb/trunk/source/Plugins/Platform/MacOSX/PlatformDarwinKernel.cpp

for (auto possible_kernel : m_kernel_binaries_without_dsyms) {
       }
     }
   }
 
   return error;
 }
 
 std::vector<lldb_private::FileSpec>
-PlatformDarwinKernel::SearchForExecutablesRecursively(const ConstString &dir) {
+PlatformDarwinKernel::SearchForExecutablesRecursively(const std::string &dir) {
   std::vector<FileSpec> executables;
   std::error_code EC;
-  for (llvm::sys::fs::recursive_directory_iterator it(dir.GetStringRef(), EC),
+  for (llvm::sys::fs::recursive_directory_iterator it(dir.c_str(), EC),
        end;
        it != end && !EC; it.increment(EC)) {
     auto status = it->status();
     if (!status)
       break;
     if (llvm::sys::fs::is_regular_file(*status) &&
         llvm::sys::fs::can_execute(it->path()))
       executables.emplace_back(it->path(), false);
   }
   return executables;
 }
 
 Status PlatformDarwinKernel::ExamineKextForMatchingUUID(
     const FileSpec &kext_bundle_path, const lldb_private::UUID &uuid,
     const ArchSpec &arch, ModuleSP &exe_module_sp) {
   for (const auto &exe_file :
-       SearchForExecutablesRecursively(kext_bundle_path.GetDirectory())) {
+       SearchForExecutablesRecursively(kext_bundle_path.GetPath())) {
     if (exe_file.Exists()) {
       ModuleSpec exe_spec(exe_file);
       exe_spec.GetUUID() = uuid;
       if (!uuid.IsValid()) {
         exe_spec.GetArchitecture() = arch;
       }
 
       // First try to create a ModuleSP with the file / arch and see if the UUID