Index: lldb/include/lldb/Symbol/ObjectContainer.h
===================================================================
--- lldb/include/lldb/Symbol/ObjectContainer.h
+++ lldb/include/lldb/Symbol/ObjectContainer.h
@@ -36,7 +36,7 @@
   /// more than one architecture or object.
   ObjectContainer(const lldb::ModuleSP &module_sp, const FileSpec *file,
                   lldb::offset_t file_offset, lldb::offset_t length,
-                  lldb::DataBufferSP &data_sp, lldb::offset_t data_offset)
+                  lldb::DataBufferSP data_sp, lldb::offset_t data_offset)
       : ModuleChild(module_sp),
         m_file(), // This file can be different than the module's file spec
         m_offset(file_offset), m_length(length) {
Index: lldb/include/lldb/Symbol/ObjectFile.h
===================================================================
--- lldb/include/lldb/Symbol/ObjectFile.h
+++ lldb/include/lldb/Symbol/ObjectFile.h
@@ -723,6 +723,8 @@
   /// file when storing cached data.
   uint32_t GetCacheHash();
 
+  static lldb::DataBufferSP MapFileData(const FileSpec &file, uint64_t Size,
+                                        uint64_t Offset);
 
 protected:
   // Member variables.
@@ -764,9 +766,6 @@
   /// The number of bytes to read when going through the plugins.
   static size_t g_initial_bytes_to_read;
 
-  static lldb::DataBufferSP MapFileData(const FileSpec &file, uint64_t Size,
-                                        uint64_t Offset);
-
 private:
   ObjectFile(const ObjectFile &) = delete;
   const ObjectFile &operator=(const ObjectFile &) = delete;
Index: lldb/source/Plugins/ObjectContainer/CMakeLists.txt
===================================================================
--- lldb/source/Plugins/ObjectContainer/CMakeLists.txt
+++ lldb/source/Plugins/ObjectContainer/CMakeLists.txt
@@ -1,2 +1,3 @@
 add_subdirectory(BSD-Archive)
 add_subdirectory(Universal-Mach-O)
+add_subdirectory(Mach-O-Fileset)
Index: lldb/source/Plugins/ObjectContainer/Mach-O-Fileset/CMakeLists.txt
===================================================================
--- /dev/null
+++ lldb/source/Plugins/ObjectContainer/Mach-O-Fileset/CMakeLists.txt
@@ -0,0 +1,10 @@
+add_lldb_library(lldbPluginObjectContainerMachOFileset PLUGIN
+  ObjectContainerMachOFileset.cpp
+
+  LINK_LIBS
+    lldbCore
+    lldbHost
+    lldbSymbol
+    lldbTarget
+    lldbUtility
+  )
Index: lldb/source/Plugins/ObjectContainer/Mach-O-Fileset/ObjectContainerMachOFileset.h
===================================================================
--- /dev/null
+++ lldb/source/Plugins/ObjectContainer/Mach-O-Fileset/ObjectContainerMachOFileset.h
@@ -0,0 +1,95 @@
+//===-- ObjectContainerMachOFileset.h ---------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_SOURCE_PLUGINS_OBJECTCONTAINER_MACH_O_FILESET_OBJECTCONTAINERMADCHOFILESET_H
+#define LLDB_SOURCE_PLUGINS_OBJECTCONTAINER_MACH_O_FILESET_OBJECTCONTAINERMADCHOFILESET_H
+
+#include "lldb/Host/SafeMachO.h"
+#include "lldb/Symbol/ObjectContainer.h"
+#include "lldb/Utility/FileSpec.h"
+
+namespace lldb_private {
+
+class ObjectContainerMachOFileset : public lldb_private::ObjectContainer {
+public:
+  ObjectContainerMachOFileset(const lldb::ModuleSP &module_sp,
+                              lldb::DataBufferSP &data_sp,
+                              lldb::offset_t data_offset,
+                              const lldb_private::FileSpec *file,
+                              lldb::offset_t offset, lldb::offset_t length);
+
+  ObjectContainerMachOFileset(const lldb::ModuleSP &module_sp,
+                              lldb::WritableDataBufferSP data_sp,
+                              const lldb::ProcessSP &process_sp,
+                              lldb::addr_t header_addr);
+
+  ~ObjectContainerMachOFileset() override;
+
+  static void Initialize();
+  static void Terminate();
+
+  static llvm::StringRef GetPluginNameStatic() { return "mach-o-fileset"; }
+
+  static llvm::StringRef GetPluginDescriptionStatic() {
+    return "Mach-O Fileset container reader.";
+  }
+
+  static lldb_private::ObjectContainer *
+  CreateInstance(const lldb::ModuleSP &module_sp, lldb::DataBufferSP &data_sp,
+                 lldb::offset_t data_offset, const lldb_private::FileSpec *file,
+                 lldb::offset_t offset, lldb::offset_t length);
+
+  static lldb_private::ObjectContainer *CreateMemoryInstance(
+      const lldb::ModuleSP &module_sp, lldb::WritableDataBufferSP data_sp,
+      const lldb::ProcessSP &process_sp, lldb::addr_t header_addr);
+
+  static size_t GetModuleSpecifications(const lldb_private::FileSpec &file,
+                                        lldb::DataBufferSP &data_sp,
+                                        lldb::offset_t data_offset,
+                                        lldb::offset_t file_offset,
+                                        lldb::offset_t length,
+                                        lldb_private::ModuleSpecList &specs);
+
+  static bool MagicBytesMatch(const lldb_private::DataExtractor &data);
+  static bool MagicBytesMatch(lldb::DataBufferSP data_sp,
+                              lldb::addr_t data_offset,
+                              lldb::addr_t data_length);
+
+  bool ParseHeader() override;
+
+  size_t GetNumObjects() const override { return m_entries.size(); }
+
+  lldb::ObjectFileSP GetObjectFile(const lldb_private::FileSpec *file) override;
+
+  llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }
+
+  struct Entry {
+    Entry(uint64_t vmaddr, uint64_t fileoff, std::string id)
+        : vmaddr(vmaddr), fileoff(fileoff), id(id) {}
+    uint64_t vmaddr;
+    uint64_t fileoff;
+    uint64_t slide;
+    std::string id;
+  };
+
+  Entry *FindEntry(llvm::StringRef id);
+
+private:
+  static bool ParseHeader(lldb_private::DataExtractor &data,
+                          const lldb_private::FileSpec &file,
+                          lldb::offset_t file_offset,
+                          std::vector<Entry> &entries);
+
+  std::vector<Entry> m_entries;
+  lldb::ProcessWP m_process_wp;
+  const lldb::addr_t m_memory_addr;
+};
+
+} // namespace lldb_private
+
+#endif // LLDB_SOURCE_PLUGINS_OBJECTCONTAINER_MACH_O_FILESET_OBJECTCONTAINERMADCHOFILESET_H
Index: lldb/source/Plugins/ObjectContainer/Mach-O-Fileset/ObjectContainerMachOFileset.cpp
===================================================================
--- /dev/null
+++ lldb/source/Plugins/ObjectContainer/Mach-O-Fileset/ObjectContainerMachOFileset.cpp
@@ -0,0 +1,286 @@
+//===-- ObjectContainerMachOFileset.cpp -----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "ObjectContainerMachOFileset.h"
+#include "lldb/Core/Module.h"
+#include "lldb/Core/ModuleSpec.h"
+#include "lldb/Core/PluginManager.h"
+#include "lldb/Symbol/ObjectFile.h"
+#include "lldb/Target/Target.h"
+#include "lldb/Utility/ArchSpec.h"
+#include "lldb/Utility/DataBuffer.h"
+#include "lldb/Utility/Stream.h"
+
+using namespace lldb;
+using namespace lldb_private;
+using namespace llvm::MachO;
+
+LLDB_PLUGIN_DEFINE(ObjectContainerMachOFileset)
+
+void ObjectContainerMachOFileset::Initialize() {
+  PluginManager::RegisterPlugin(GetPluginNameStatic(),
+                                GetPluginDescriptionStatic(), CreateInstance,
+                                GetModuleSpecifications);
+}
+
+void ObjectContainerMachOFileset::Terminate() {
+  PluginManager::UnregisterPlugin(CreateInstance);
+}
+
+ObjectContainerMachOFileset::ObjectContainerMachOFileset(
+    const lldb::ModuleSP &module_sp, lldb::DataBufferSP &data_sp,
+    lldb::offset_t data_offset, const lldb_private::FileSpec *file,
+    lldb::offset_t offset, lldb::offset_t length)
+    : ObjectContainer(module_sp, file, offset, length, data_sp, data_offset),
+      m_memory_addr(LLDB_INVALID_ADDRESS) {}
+
+ObjectContainerMachOFileset::ObjectContainerMachOFileset(
+    const lldb::ModuleSP &module_sp, lldb::WritableDataBufferSP data_sp,
+    const lldb::ProcessSP &process_sp, lldb::addr_t header_addr)
+    : ObjectContainer(module_sp, nullptr, 0, 0, data_sp, 0),
+      m_memory_addr(header_addr) {}
+
+ObjectContainer *ObjectContainerMachOFileset::CreateInstance(
+    const lldb::ModuleSP &module_sp, DataBufferSP &data_sp,
+    lldb::offset_t data_offset, const FileSpec *file,
+    lldb::offset_t file_offset, lldb::offset_t length) {
+  if (!data_sp)
+    return {};
+
+  DataExtractor data;
+  data.SetData(data_sp, data_offset, length);
+  if (!MagicBytesMatch(data))
+    return {};
+
+  auto container_up = std::make_unique<ObjectContainerMachOFileset>(
+      module_sp, data_sp, data_offset, file, file_offset, length);
+  if (!container_up->ParseHeader())
+    return {};
+
+  return container_up.release();
+}
+
+ObjectContainer *ObjectContainerMachOFileset::CreateMemoryInstance(
+    const lldb::ModuleSP &module_sp, lldb::WritableDataBufferSP data_sp,
+    const lldb::ProcessSP &process_sp, lldb::addr_t header_addr) {
+  if (!MagicBytesMatch(data_sp, 0, data_sp->GetByteSize()))
+    return {};
+
+  auto container_up = std::make_unique<ObjectContainerMachOFileset>(
+      module_sp, data_sp, process_sp, header_addr);
+  if (!container_up->ParseHeader())
+    return {};
+
+  return container_up.release();
+}
+
+ObjectContainerMachOFileset::~ObjectContainerMachOFileset() = default;
+
+static uint32_t MachHeaderSizeFromMagic(uint32_t magic) {
+  switch (magic) {
+  case MH_MAGIC:
+  case MH_CIGAM:
+    return sizeof(struct llvm::MachO::mach_header);
+  case MH_MAGIC_64:
+  case MH_CIGAM_64:
+    return sizeof(struct llvm::MachO::mach_header_64);
+  default:
+    return 0;
+  }
+}
+
+static llvm::Optional<llvm::MachO::mach_header>
+ParseMachOHeader(DataExtractor &data) {
+  lldb::offset_t offset = 0;
+  llvm::MachO::mach_header header;
+  header.magic = data.GetU32(&offset);
+  switch (header.magic) {
+  case MH_MAGIC:
+    data.SetByteOrder(endian::InlHostByteOrder());
+    data.SetAddressByteSize(4);
+    break;
+  case MH_MAGIC_64:
+    data.SetByteOrder(endian::InlHostByteOrder());
+    data.SetAddressByteSize(8);
+    break;
+  case MH_CIGAM:
+    data.SetByteOrder(endian::InlHostByteOrder() == eByteOrderBig
+                          ? eByteOrderLittle
+                          : eByteOrderBig);
+    data.SetAddressByteSize(4);
+    break;
+  case MH_CIGAM_64:
+    data.SetByteOrder(endian::InlHostByteOrder() == eByteOrderBig
+                          ? eByteOrderLittle
+                          : eByteOrderBig);
+    data.SetAddressByteSize(8);
+    break;
+  default:
+    return {};
+  }
+
+  header.cputype = data.GetU32(&offset);
+  header.cpusubtype = data.GetU32(&offset);
+  header.filetype = data.GetU32(&offset);
+  header.ncmds = data.GetU32(&offset);
+  header.sizeofcmds = data.GetU32(&offset);
+  return header;
+}
+
+static bool
+ParseFileset(DataExtractor &data, llvm::MachO::mach_header header,
+             std::vector<ObjectContainerMachOFileset::Entry> &entries) {
+  lldb::offset_t offset = MachHeaderSizeFromMagic(header.magic);
+  ;
+  for (uint32_t i = 0; i < header.ncmds; ++i) {
+    const lldb::offset_t load_cmd_offset = offset;
+    llvm::MachO::load_command lc = {};
+    if (data.GetU32(&offset, &lc.cmd, 2) == nullptr)
+      break;
+
+    if (lc.cmd == LC_FILESET_ENTRY) {
+      llvm::MachO::fileset_entry_command entry;
+      data.CopyData(load_cmd_offset, sizeof(llvm::MachO::fileset_entry_command),
+                    &entry);
+      lldb::offset_t entry_id_offset = load_cmd_offset + entry.entry_id;
+      const char *id = data.GetCStr(&entry_id_offset);
+      entries.emplace_back(entry.vmaddr, entry.fileoff, std::string(id));
+    }
+    offset = load_cmd_offset + lc.cmdsize;
+  }
+
+  return true;
+}
+
+bool ObjectContainerMachOFileset::ParseHeader(
+    DataExtractor &data, const lldb_private::FileSpec &file,
+    lldb::offset_t file_offset, std::vector<Entry> &entries) {
+  llvm::Optional<llvm::MachO::mach_header> header = ParseMachOHeader(data);
+
+  if (!header)
+    return false;
+
+  const size_t header_size = MachHeaderSizeFromMagic(header->magic);
+  const size_t header_and_lc_size = header_size + header->sizeofcmds;
+
+  if (data.GetByteSize() < header_and_lc_size) {
+    DataBufferSP data_sp =
+        ObjectFile::MapFileData(file, header_and_lc_size, file_offset);
+    data.SetData(data_sp, file_offset, header_and_lc_size);
+  }
+
+  return ParseFileset(data, *header, entries);
+}
+
+bool ObjectContainerMachOFileset::ParseHeader() {
+  ModuleSP module_sp(GetModule());
+  if (!module_sp)
+    return false;
+
+  std::lock_guard<std::recursive_mutex> guard(module_sp->GetMutex());
+
+  llvm::Optional<llvm::MachO::mach_header> header = ParseMachOHeader(m_data);
+  if (!header)
+    return false;
+
+  const size_t header_size = MachHeaderSizeFromMagic(header->magic);
+  const size_t header_and_lc_size = header_size + header->sizeofcmds;
+
+  if (m_data.GetByteSize() < header_and_lc_size) {
+    ProcessSP process_sp(m_process_wp.lock());
+    DataBufferSP data_sp =
+        process_sp
+            ? ObjectFile::ReadMemory(process_sp, m_memory_addr,
+                                     header_and_lc_size)
+            : ObjectFile::MapFileData(m_file, header_and_lc_size, m_offset);
+    m_data.SetData(data_sp, m_offset, header_and_lc_size);
+  }
+
+  return ParseFileset(m_data, *header, m_entries);
+}
+
+size_t ObjectContainerMachOFileset::GetModuleSpecifications(
+    const lldb_private::FileSpec &file, lldb::DataBufferSP &data_sp,
+    lldb::offset_t data_offset, lldb::offset_t file_offset,
+    lldb::offset_t file_size, lldb_private::ModuleSpecList &specs) {
+  const size_t initial_count = specs.GetSize();
+
+  DataExtractor data;
+  data.SetData(data_sp, data_offset, data_sp->GetByteSize());
+
+  if (MagicBytesMatch(data)) {
+    std::vector<Entry> entries;
+    if (ParseHeader(data, file, file_offset, entries)) {
+      for (const Entry &entry : entries) {
+        const lldb::offset_t entry_offset = entry.fileoff + file_offset;
+        if (ObjectFile::GetModuleSpecifications(
+                file, entry_offset, file_size - entry_offset, specs)) {
+          ModuleSpec &spec = specs.GetModuleSpecRefAtIndex(specs.GetSize() - 1);
+          spec.GetObjectName() = ConstString(entry.id);
+        }
+      }
+    }
+  }
+  return specs.GetSize() - initial_count;
+}
+
+bool ObjectContainerMachOFileset::MagicBytesMatch(DataBufferSP data_sp,
+                                                  lldb::addr_t data_offset,
+                                                  lldb::addr_t data_length) {
+  DataExtractor data;
+  data.SetData(data_sp, data_offset, data_length);
+  return MagicBytesMatch(data);
+}
+
+bool ObjectContainerMachOFileset::MagicBytesMatch(const DataExtractor &data) {
+  lldb::offset_t offset = 0;
+  uint32_t magic = data.GetU32(&offset);
+  switch (magic) {
+  case MH_MAGIC:
+  case MH_CIGAM:
+  case MH_MAGIC_64:
+  case MH_CIGAM_64:
+    break;
+  default:
+    return false;
+  }
+  offset += 4; // cputype
+  offset += 4; // cpusubtype
+  uint32_t filetype = data.GetU32(&offset);
+  return filetype == llvm::MachO::MH_FILESET;
+}
+
+ObjectFileSP
+ObjectContainerMachOFileset::GetObjectFile(const lldb_private::FileSpec *file) {
+  ModuleSP module_sp(GetModule());
+  if (!module_sp)
+    return {};
+
+  ConstString object_name = module_sp->GetObjectName();
+  if (!object_name)
+    return {};
+
+  Entry *entry = FindEntry(object_name.GetCString());
+  if (!entry)
+    return {};
+
+  DataBufferSP data_sp;
+  lldb::offset_t data_offset = 0;
+  return ObjectFile::FindPlugin(module_sp, file, m_offset + entry->fileoff,
+                                m_data.GetByteSize() - entry->fileoff, data_sp,
+                                data_offset);
+}
+
+ObjectContainerMachOFileset::Entry *
+ObjectContainerMachOFileset::FindEntry(llvm::StringRef id) {
+  for (Entry &entry : m_entries) {
+    if (entry.id == id)
+      return &entry;
+  }
+  return nullptr;
+}
Index: lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
===================================================================
--- lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -941,6 +941,17 @@
   data.SetData(data_sp, data_offset, data_length);
   lldb::offset_t offset = 0;
   uint32_t magic = data.GetU32(&offset);
+
+  offset += 4; // cputype
+  offset += 4; // cpusubtype
+  uint32_t filetype = data.GetU32(&offset);
+
+  // A fileset has a Mach-O header but is not an
+  // individual file and must be handled via an
+  // ObjectContainer plugin.
+  if (filetype == llvm::MachO::MH_FILESET)
+    return false;
+
   return MachHeaderSizeFromMagic(magic) != 0;
 }