[lldb] Add DynamicLoader for FreeBSD Kernel post-mortem debug facility

[aokblast]

Change loaded DynamicLoader plugin for ProcessFreeBSDKernel

[aokblast]

Add relocatable file support for kernel module

[aokblast]

Add subdirectory for DynamicLoader Plugin directory

[emaste]

lldb/source/Plugins/DynamicLoader/FreeBSD-Kernel/DynamicLoaderFreeBSDKernel.cpp

116–117

kFreeBSD indicates a FreeBSD kernel, typically with some other userland (e.g. Debian GNU/kFreeBSD is Debian's standard userland, with FreeBSD instead of Linux as the kernel). But these projects are mostly not active anymore and I'm not sure how we'd test.

184

Add return false; for now as well?

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

943 ↗

(On Diff #554237)

The indentation looks wrong on a few lines here,

[aokblast]

Add "real comment" for commented code
Some of my code is commented without showing the reason.
In this comment, I add the reason for it.

[aokblast]

This change fix the indentation for the ObjectFileELF.cpp

lldb/source/Plugins/DynamicLoader/FreeBSD-Kernel/CMakeLists.txt

+add_lldb_library(lldbPluginDynamicLoaderFreeBSDKernel PLUGIN
+  DynamicLoaderFreeBSDKernel.cpp
+
+  LINK_LIBS
+    lldbBreakpoint
+    lldbCore
+    lldbHost
+    lldbInterpreter
+    lldbSymbol
+    lldbTarget
+    lldbUtility
+    lldbPluginObjectFileELF
+  )

lldb/source/Plugins/DynamicLoader/FreeBSD-Kernel/DynamicLoaderFreeBSDKernel.h

+#ifndef LLDB_SOURCE_PLUGINS_DYNAMICLOADER_FREEBSD_KERNEL_DYNAMICLOADERFREEBSDKERNEL_H
+#define LLDB_SOURCE_PLUGINS_DYNAMICLOADER_FREEBSD_KERNEL_DYNAMICLOADERFREEBSDKERNEL_H
+
+#include <mutex>
+#include <string>
+#include <vector>
+
+#include "lldb/Target/DynamicLoader.h"
+#include "lldb/Target/Process.h"
+#include "lldb/Utility/FileSpec.h"
+#include "lldb/Utility/UUID.h"
+#include "llvm/BinaryFormat/ELF.h"
+
+class DynamicLoaderFreeBSDKernel : public lldb_private::DynamicLoader {
+public:
+  DynamicLoaderFreeBSDKernel(lldb_private::Process *process,
+                             lldb::addr_t kernel_addr);
+
+  ~DynamicLoaderFreeBSDKernel() override;
+
+  // Static Functions
+
+  static void Initialize();
+
+  static void Terminate();
+
+  static llvm::StringRef GetPluginNameStatic() {
+    return "DynamicLoaderFreeBSDKernel";
+  }
+
+  static llvm::StringRef GetPluginDescriptionStatic();
+
+  static lldb_private::DynamicLoader *
+  CreateInstance(lldb_private::Process *process, bool force);
+
+  static void DebuggerInit(lldb_private::Debugger &debugger);
+
+  static lldb::addr_t FindFreeBSDKernel(lldb_private::Process *process);
+
+  // Hooks for time point that after attach to some proccess
+  void DidAttach() override;
+
+  void DidLaunch() override;
+
+  lldb::ThreadPlanSP GetStepThroughTrampolinePlan(lldb_private::Thread &thread,
+                                                  bool stop_others) override;
+
+  lldb_private::Status CanLoadImage() override;
+
+  llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }
+
+protected:
+  class KModImageInfo {
+  public:
+    KModImageInfo()
+        : m_module_sp(), m_memory_module_sp(), m_uuid(), m_name(), m_path() {}
+
+    void Clear() {
+      m_load_address = LLDB_INVALID_ADDRESS;
+      m_name.clear();
+      m_uuid.Clear();
+      m_module_sp.reset();
+      m_memory_module_sp.reset();
+      m_stop_id = UINT32_MAX;
+      m_path.clear();
+    }
+
+    void SetLoadAddress(lldb::addr_t load_address) {
+      m_load_address = load_address;
+    }
+
+    lldb::addr_t GetLoadAddress() const { return m_load_address; }
+
+    void SetUUID(const lldb_private::UUID uuid) { m_uuid = uuid; }
+
+    lldb_private::UUID GetUUID() const { return m_uuid; }
+
+    void SetName(const char *name) { m_name = name; }
+
+    std::string GetName() const { return m_name; }
+
+    void SetPath(const char *path) { m_path = path; }
+
+    std::string GetPath() const { return m_path; }
+
+    void SetModule(lldb::ModuleSP module) { m_module_sp = module; }
+
+    lldb::ModuleSP GetModule() { return m_module_sp; }
+
+    void SetIsKernel(bool is_kernel) { m_is_kernel = is_kernel; }
+
+    bool IsKernel() const { return m_is_kernel; };
+
+    void SetStopID(uint32_t stop_id) { m_stop_id = stop_id; }
+
+    uint32_t GetStopID() { return m_stop_id; }
+
+    bool IsLoaded() const { return m_stop_id != UINT32_MAX; };
+
+    bool ReadMemoryModule(lldb_private::Process *process);
+
+    bool LoadImageUsingMemoryModule(lldb_private::Process *process);
+
+    bool LoadImageUsingFileAddress(lldb_private::Process *process);
+
+    using collection_type = std::vector<KModImageInfo>;
+
+  private:
+    lldb::ModuleSP m_module_sp;
+    lldb::ModuleSP m_memory_module_sp;
+    lldb::addr_t m_load_address = LLDB_INVALID_ADDRESS;
+    lldb_private::UUID m_uuid;
+    bool m_is_kernel = false;
+    std::string m_name;
+    std::string m_path;
+    uint32_t m_stop_id = UINT32_MAX;
+  };
+
+  void PrivateInitialize(lldb_private::Process *process);
+
+  void Clear(bool clear_process);
+
+  void Update();
+
+  void LoadKernelModules();
+
+  bool ReadAllKmods();
+
+  bool ReadAllKmods(lldb_private::Address linker_files_head_address,
+                    KModImageInfo::collection_type &kmods_list);
+
+  bool ReadKmodsListHeader();
+
+  bool ParseKmods(lldb_private::Address linker_files_head_address);
+
+  void SetNotificationBreakPoint();
+
+  static lldb_private::UUID
+  CheckForKernelImageAtAddress(lldb_private::Process *process,
+                               lldb::addr_t address,
+                               bool *read_error = nullptr);
+
+  static lldb::addr_t FindKernelAtLoadAddress(lldb_private::Process *process);
+
+  static bool ReadELFHeader(lldb_private::Process *process,
+                            lldb::addr_t address, llvm::ELF::Elf32_Ehdr &header,
+                            bool *read_error = nullptr);
+
+  lldb_private::Process *m_process;
+  lldb_private::Address m_linker_file_list_struct_addr;
+  lldb_private::Address m_linker_file_head_addr;
+  lldb::addr_t m_kernel_load_address;
+  KModImageInfo m_kernel_image_info;
+  KModImageInfo::collection_type m_linker_files_list;
+  std::recursive_mutex m_mutex;
+  std::unordered_map<std::string, lldb_private::UUID> m_kld_name_to_uuid;
+
+private:
+  DynamicLoaderFreeBSDKernel(const DynamicLoaderFreeBSDKernel &) = delete;
+
+  const DynamicLoaderFreeBSDKernel &
+  operator=(const DynamicLoaderFreeBSDKernel &) = delete;
+};
+
+#endif

lldb/source/Plugins/DynamicLoader/FreeBSD-Kernel/DynamicLoaderFreeBSDKernel.cpp

+#include "lldb/Breakpoint/StoppointCallbackContext.h"
+#include "lldb/Core/Debugger.h"
+#include "lldb/Core/Module.h"
+#include "lldb/Core/ModuleSpec.h"
+#include "lldb/Core/PluginManager.h"
+#include "lldb/Core/Section.h"
+#include "lldb/Core/StreamFile.h"
+#include "lldb/Interpreter/OptionValueProperties.h"
+#include "lldb/Symbol/LocateSymbolFile.h"
+#include "lldb/Symbol/ObjectFile.h"
+#include "lldb/Target/OperatingSystem.h"
+#include "lldb/Target/RegisterContext.h"
+#include "lldb/Target/StackFrame.h"
+#include "lldb/Target/Target.h"
+#include "lldb/Target/Thread.h"
+#include "lldb/Target/ThreadPlanRunToAddress.h"
+#include "lldb/Utility/DataBuffer.h"
+#include "lldb/Utility/DataBufferHeap.h"
+#include "lldb/Utility/LLDBLog.h"
+#include "lldb/Utility/Log.h"
+#include "lldb/Utility/State.h"
+
+#include "Plugins/ObjectFile/ELF/ObjectFileELF.h"
+
+#include "DynamicLoaderFreeBSDKernel.h"
+#include <memory>
+#include <mutex>
+
+using namespace lldb;
+using namespace lldb_private;
+
+LLDB_PLUGIN_DEFINE(DynamicLoaderFreeBSDKernel)
+
+// class PluginProperties : public Properties {
+// public:
+//     static ConstString &GetSettingName() {
+//         static ConstString g_setting_name("freebsd-kernel");
+//         return g_setting_name;
+//     }
+
+//     PluginProperties() : Properties() {
+//         m_collection_sp =
+//         std::make_shared<OptionValueProperties>(GetSettingName());
+//     }
+
+//     ~PluginProperties() override = default;
+// };
+
+// static PluginProperties &GetGlobalProperties() {
+//     static PluginProperties g_settings;
+//     return g_settings;
+// }
+
+void DynamicLoaderFreeBSDKernel::Initialize() {
+  PluginManager::RegisterPlugin(GetPluginNameStatic(),
+                                GetPluginDescriptionStatic(), CreateInstance,
+                                DebuggerInit);
+}
+
+void DynamicLoaderFreeBSDKernel::Terminate() {
+  PluginManager::UnregisterPlugin(CreateInstance);
+}
+
+llvm::StringRef DynamicLoaderFreeBSDKernel::GetPluginDescriptionStatic() {
+  return "The Dynamic Loader Plugin For FreeBSD Kernel";
+}
+
+static bool is_kernel(Module *module) {
+  if (!module)
+    return false;
+
+  ObjectFile *objfile = module->GetObjectFile();
+  if (!objfile)
+    return false;
+  if (objfile->GetType() != ObjectFile::eTypeExecutable)
+    return false;
+  if (objfile->GetStrata() != ObjectFile::eStrataUnknown &&
+      objfile->GetStrata() != ObjectFile::eStrataUser)
+    return false;
+
+  return true;
+}
+
+static bool is_kmod(Module *module) {
+  if (!module)
+    return false;
+  if (!module->GetObjectFile())
+    return false;
+  ObjectFile *objfile = module->GetObjectFile();
+  if (objfile->GetType() != ObjectFile::eTypeObjectFile)
+    return false;
+
+  return true;
+}
+
+// Instantiate Function of the FreeBSD Kernel Dynamic Loader Plugin called when
+// Register the Plugin
+DynamicLoader *
+DynamicLoaderFreeBSDKernel::CreateInstance(lldb_private::Process *process,
+                                           bool force) {
+  // Check the environment when the plugin is not force loaded
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+  LLDB_LOGF(log, "DynamicLoaderFreeBSDKernel::CreateInstance: "
+                 "Try to create instance");
+  if (!force) {
+    Module *exec = process->GetTarget().GetExecutableModulePointer();
+    // Check if the target is kernel
+    if (exec && !is_kernel(exec)) {
+      return nullptr;
+    }
+
+    const llvm::Triple &triple_ref =
+        process->GetTarget().GetArchitecture().GetTriple();
+    // TODO: If we need to check unknow OS triple like armv7-unknown-unknown?
+    // TODO: I don't know if kFreeBSD is a type of FreeBSD and should we accept
+    // this Triple? Check the type of kernel
+    if (!triple_ref.isOSFreeBSD()) {
+      return nullptr;
+    }
+  }
+
+  // At this point we have checked the target is a FreeBSD kernel and all we
+  // have to do is to find the kernel address
+  const addr_t kernel_address = FindFreeBSDKernel(process);
+
+  if (CheckForKernelImageAtAddress(process, kernel_address).IsValid())
+    return new DynamicLoaderFreeBSDKernel(process, kernel_address);
+
+  return nullptr;
+}
+
+addr_t
+DynamicLoaderFreeBSDKernel::FindFreeBSDKernel(lldb_private::Process *process) {
+  addr_t kernel_addr = process->GetImageInfoAddress();
+  if (kernel_addr == LLDB_INVALID_ADDRESS)
+    kernel_addr = FindKernelAtLoadAddress(process);
+  return kernel_addr;
+}
+
+// Get the kernel address if the kernel is not loaded with a slide
+addr_t DynamicLoaderFreeBSDKernel::FindKernelAtLoadAddress(
+    lldb_private::Process *process) {
+  Module *exe_module = process->GetTarget().GetExecutableModulePointer();
+
+  if (!is_kernel(exe_module))
+    return LLDB_INVALID_ADDRESS;
+
+  ObjectFile *exe_objfile = exe_module->GetObjectFile();
+
+  if (!exe_objfile->GetBaseAddress().IsValid())
+    return LLDB_INVALID_ADDRESS;
+
+  // TODO: check the uuid same as runtime
+  if (CheckForKernelImageAtAddress(
+          process, exe_objfile->GetBaseAddress().GetFileAddress())
+          .IsValid())
+    return exe_objfile->GetBaseAddress().GetFileAddress();
+
+  return LLDB_INVALID_ADDRESS;
+}
+
+// TODO: Check for big endian
+// Read ELF header from memry and return
+bool DynamicLoaderFreeBSDKernel::ReadELFHeader(Process *process,
+                                               lldb::addr_t addr,
+                                               llvm::ELF::Elf32_Ehdr &header,
+                                               bool *read_error) {
+  Status error;
+  if (read_error)
+    *read_error = false;
+
+  if (process->ReadMemory(addr, &header, sizeof(header), error) !=
+      sizeof(header)) {
+    if (read_error)
+      *read_error = true;
+    return false;
+  }
+
+  if (!header.checkMagic())
+    return false;
+
+  if (header.getDataEncoding() == llvm::ELF::ELFDATA2MSB) {
+    // TODO: swap byte order for big endian
+  }
+
+  return true;
+}
+
+// Check the correctness of Kernel and return UUID
+lldb_private::UUID DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress(
+    Process *process, lldb::addr_t addr, bool *read_error) {
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+
+  if (addr == LLDB_INVALID_ADDRESS) {
+    if (read_error)
+      *read_error = true;
+    return UUID();
+  }
+
+  LLDB_LOGF(log,
+            "DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress: "
+            "looking for kernel binary at 0x%" PRIx64,
+            addr);
+
+  llvm::ELF::Elf32_Ehdr header;
+  if (!ReadELFHeader(process, addr, header))
+    return UUID();
+
+  // Check header type
+  if (header.e_type != llvm::ELF::ET_EXEC)
+    return UUID();
+
+  ModuleSP memory_module_sp =
+      process->ReadModuleFromMemory(FileSpec("temp_freebsd_kernel"), addr);
+  if (!memory_module_sp.get())
+    return UUID();
+
+  ObjectFile *exe_objfile = memory_module_sp->GetObjectFile();
+  if (exe_objfile == nullptr) {
+    LLDB_LOGF(log,
+              "DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress "
+              "found a binary at 0x%" PRIx64
+              " but could not create an object file from memory",
+              addr);
+    return UUID();
+  }
+
+  if (is_kernel(memory_module_sp.get())) {
+    ArchSpec kernel_arch(
+        llvm::ELF::convertEMachineToArchName(header.e_machine));
+
+    if (!process->GetTarget().GetArchitecture().IsCompatibleMatch(kernel_arch))
+      process->GetTarget().SetArchitecture(kernel_arch);
+
+    if (log) {
+      std::string uuid_str;
+      if (memory_module_sp->GetUUID().IsValid()) {
+        uuid_str = "with UUID ";
+        uuid_str += memory_module_sp->GetUUID().GetAsString();
+      } else {
+        uuid_str = "and no LC_UUID found in load commands ";
+      }
+      LLDB_LOGF(log,
+                "DynamicLoaderFreeBSDKernel::CheckForKernelImageAtAddress: "
+                "kernel binary image found at 0x%" PRIx64 " with arch '%s' %s",
+                addr, kernel_arch.GetTriple().str().c_str(), uuid_str.c_str());
+    }
+
+    return memory_module_sp->GetUUID();
+  }
+
+  return UUID();
+}
+
+void DynamicLoaderFreeBSDKernel::DebuggerInit(
+    lldb_private::Debugger &debugger) {
+  //   if (!PluginManager::GetSettingForDynamicLoaderPlugin(debugger,
+  //   PluginProperties::GetSettingName())) {
+  //     const bool is_global_setting = true;
+  //     PluginManager::CreateSettingForDynamicLoaderPlugin(
+  //         debugger, GetGlobalProperties().GetValueProperties(),
+  //         "Properties for the DynamicLoaderFreeBSDKernel plug-in." ,
+  //         is_global_setting);
+  // }
+}
+
+DynamicLoaderFreeBSDKernel::DynamicLoaderFreeBSDKernel(Process *process,
+                                                       addr_t kernel_address)
+  : DynamicLoader(process), m_process(process),
+    m_linker_file_list_struct_addr(LLDB_INVALID_ADDRESS),
+    m_linker_file_head_addr(LLDB_INVALID_ADDRESS),
+    m_kernel_load_address(kernel_address),
+    m_mutex() {
+  process->SetCanRunCode(false);
+}
+
+DynamicLoaderFreeBSDKernel::~DynamicLoaderFreeBSDKernel() { Clear(true); }
+
+void DynamicLoaderFreeBSDKernel::Update() {
+  LoadKernelModules();
+  SetNotificationBreakPoint();
+}
+
+// Create in memory Module at the load address
+bool DynamicLoaderFreeBSDKernel::KModImageInfo::ReadMemoryModule(
+    lldb_private::Process *process) {
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+  if (m_memory_module_sp)
+    return true;
+  if (m_load_address == LLDB_INVALID_ADDRESS)
+    return false;
+
+  FileSpec file_spec(m_name.c_str());
+
+  ModuleSP memory_module_sp;
+
+  llvm::ELF::Elf32_Ehdr elf_eheader;
+  size_t size_to_read = 512;
+
+  // TODO:: If we have to check if the pheader entry is not follow after eheader
+  if (ReadELFHeader(process, m_load_address, elf_eheader)) {
+    if (elf_eheader.e_ident[llvm::ELF::EI_CLASS] == llvm::ELF::ELFCLASS32) {
+      size_to_read = sizeof(llvm::ELF::Elf32_Ehdr) +
+                     elf_eheader.e_phnum * elf_eheader.e_phentsize;
+    } else if (elf_eheader.e_ident[llvm::ELF::EI_CLASS] ==
+               llvm::ELF::ELFCLASS64) {
+      llvm::ELF::Elf64_Ehdr elf_eheader;
+      Status error;
+      if (process->ReadMemory(m_load_address, &elf_eheader, sizeof(elf_eheader),
+                              error) == sizeof(elf_eheader))
+        size_to_read = sizeof(llvm::ELF::Elf64_Ehdr) +
+                       elf_eheader.e_phnum * elf_eheader.e_phentsize;
+    }
+  }
+
+  memory_module_sp =
+      process->ReadModuleFromMemory(file_spec, m_load_address, size_to_read);
+
+  if (!memory_module_sp)
+    return false;
+
+  bool this_is_kernel = is_kernel(memory_module_sp.get());
+
+  // If the kernel specify what UUID should be found, we should match it
+  // if (m_uuid.IsValid() && m_uuid != memory_module_sp->GetUUID()) {
+  //     if (log) {
+  //         LLDB_LOGF(log,
+  //                   "KextImageInfo::ReadMemoryModule the kernel said to find
+  //                   " "uuid %s at 0x%" PRIx64 " but instead we found uuid %s,
+  //                   throwing it away", m_uuid.GetAsString().c_str(),
+  //                   m_load_address,
+  //                   memory_module_sp->GetUUID().GetAsString().c_str());
+  //     }
+  //     return false;
+  // }
+
+  if (!m_uuid.IsValid() && memory_module_sp->GetUUID().IsValid())
+    m_uuid = memory_module_sp->GetUUID();
+
+  m_memory_module_sp = memory_module_sp;
+  m_is_kernel = this_is_kernel;
+
+  // The kernel binary is from memory
+  if (this_is_kernel) {
+    if (log)
+      LLDB_LOGF(log,
+                "KextImageInfo::ReadMemoryModule read the kernel binary out "
+                "of memory");
+
+    if (memory_module_sp->GetArchitecture().IsValid())
+      process->GetTarget().SetArchitecture(memory_module_sp->GetArchitecture());
+  }
+
+  return true;
+}
+
+bool DynamicLoaderFreeBSDKernel::KModImageInfo::LoadImageUsingMemoryModule(
+    lldb_private::Process *process) {
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+
+  if (IsLoaded())
+    return true;
+
+  Target &target = process->GetTarget();
+
+  if (IsKernel() && m_uuid.IsValid()) {
+    Stream &s = target.GetDebugger().GetOutputStream();
+    s.Printf("Kernel UUID: %s\n", m_uuid.GetAsString().c_str());
+    s.Printf("Load Address: 0x%" PRIx64 "\n", m_load_address);
+
+    // Delete more than one kernel image that accidently add by user
+    // ModuleList incorrect_kernels;
+    // for (ModuleSP module_sp : target.GetImages().Modules()) {
+    //   if (is_kernel(module_sp.get()) && module_sp->GetUUID() != m_uuid) {
+    //         incorrect_kernels.Append(module_sp);
+    // }
+    // target.GetImages().Remove(incorrect_kernels);
+  }
+
+  // Test if the module is loaded into the taget,
+  // maybe the module is loaded manually by user by doing target module add
+  // So that we have to create the module manually
+  if (!m_module_sp) {
+    const ModuleList &target_images = target.GetImages();
+    m_module_sp = target_images.FindModule(m_uuid);
+
+    // Search in the file system
+    if (!m_module_sp) {
+      ModuleSpec module_spec(FileSpec(GetPath()), target.GetArchitecture());
+      if (IsKernel()) {
+        Status error;
+        if (Symbols::DownloadObjectAndSymbolFile(module_spec, error, true)) {
+          if (FileSystem::Instance().Exists(module_spec.GetFileSpec()))
+            m_module_sp = std::make_shared<Module>(module_spec.GetFileSpec(),
+                                                   target.GetArchitecture());
+        }
+      }
+
+      if (!m_module_sp)
+        m_module_sp = target.GetOrCreateModule(module_spec, true);
+      if (IsKernel() && !m_module_sp) {
+        Stream &s = target.GetDebugger().GetOutputStream();
+        s.Printf("WARNING: Unable to locate kernel binary on the debugger "
+                 "system.\n");
+      }
+    }
+
+    if (m_module_sp) {
+      // If the file is not kernel or kmod, the target should be loaded once and
+      // don't reload again
+      if (!IsKernel() && !is_kmod(m_module_sp.get())) {
+        ModuleSP existing_module_sp = target.GetImages().FindModule(m_uuid);
+        if (existing_module_sp &&
+            existing_module_sp->IsLoadedInTarget(&target)) {
+          LLDB_LOGF(log,
+                    "'%s' with UUID %s is not a kmod or kernel, and is "
+                    "already registered in target, not loading.",
+                    m_name.c_str(), m_uuid.GetAsString().c_str());
+          return true;
+        }
+      }
+      m_uuid = m_module_sp->GetUUID();
+
+      // or append to the images
+      target.GetImages().AppendIfNeeded(m_module_sp, false);
+    }
+  }
+
+  // If this file is kernel module, adjust it's section(PT_LOAD segment) and return
+  // Because the kernel module's load address is the text section.
+  // lldb cannot create full memory module upon relocatable file
+  // So what we do is to set the load address only.
+  if (is_kmod(m_module_sp.get())) {
+    m_stop_id = process->GetStopID();
+    bool changed;
+    m_module_sp->SetLoadAddress(target, m_load_address, true, changed);
+    return true;
+  }
+
+  if (m_module_sp)
+    ReadMemoryModule(process);
+
+  // Calculate the slides of in memory module
+  if (!m_memory_module_sp || !m_module_sp) {
+    m_module_sp.reset();
+    return false;
+  }
+
+  // TODO: figure out why UUID is not same in FreeBSD Kernel dump
+  // if (m_memory_module_sp->GetUUID() != m_module_sp->GetUUID())
+  //     m_module_sp.reset();
+
+  ObjectFile *ondisk_object_file = m_module_sp->GetObjectFile();
+  ObjectFile *memory_object_file = m_memory_module_sp->GetObjectFile();
+
+  if (!ondisk_object_file || !memory_object_file)
+    m_module_sp.reset();
+
+  // Find the slide address
+  addr_t fixed_slide = LLDB_INVALID_ADDRESS;
+  if (ObjectFileELF *memory_objfile_elf =
+          llvm::dyn_cast<ObjectFileELF>(memory_object_file)) {
+    addr_t load_address = memory_object_file->GetBaseAddress().GetFileAddress();
+
+    if (load_address != LLDB_INVALID_ADDRESS &&
+        m_load_address != load_address) {
+      fixed_slide = m_load_address - load_address;
+      LLDB_LOGF(log,
+                "kmod %s in-memory LOAD vmaddr is not correct, using a "
+                "fixed slide of 0x%" PRIx64,
+                m_name.c_str(), fixed_slide);
+    }
+  }
+
+  SectionList *ondisk_section_list = ondisk_object_file->GetSectionList();
+  SectionList *memory_section_list = memory_object_file->GetSectionList();
+
+  if (memory_section_list && ondisk_object_file) {
+    const uint32_t num_ondisk_sections = ondisk_section_list->GetSize();
+    uint32_t num_load_sections = 0;
+
+    for (uint32_t section_idx = 0; section_idx < num_ondisk_sections;
+         ++section_idx) {
+      SectionSP on_disk_section_sp =
+          ondisk_section_list->GetSectionAtIndex(section_idx);
+
+      if (!on_disk_section_sp)
+        continue;
+      if (fixed_slide != LLDB_INVALID_ADDRESS) {
+        target.SetSectionLoadAddress(on_disk_section_sp,
+                                     on_disk_section_sp->GetFileAddress() +
+                                         fixed_slide);
+
+      } else {
+        const Section *memory_section =
+            memory_section_list
+                ->FindSectionByName(on_disk_section_sp->GetName())
+                .get();
+        if (memory_section) {
+          target.SetSectionLoadAddress(on_disk_section_sp,
+                                       memory_section->GetFileAddress());
+          ++num_load_sections;
+        }
+      }
+    }
+
+    if (num_load_sections)
+      m_stop_id = process->GetStopID();
+    else
+      m_module_sp.reset();
+  } else {
+    m_module_sp.reset();
+  }
+
+  if (IsLoaded() && m_module_sp && IsKernel()) {
+    Stream &s = target.GetDebugger().GetOutputStream();
+    ObjectFile *kernel_object_file = m_module_sp->GetObjectFile();
+    if (kernel_object_file) {
+      addr_t file_address =
+          kernel_object_file->GetBaseAddress().GetFileAddress();
+      if (m_load_address != LLDB_INVALID_ADDRESS &&
+          file_address != LLDB_INVALID_ADDRESS) {
+        s.Printf("Kernel slide 0x%" PRIx64 " in memory.\n",
+                 m_load_address - file_address);
+        s.Printf("Loaded kernel file %s\n",
+                 m_module_sp->GetFileSpec().GetPath().c_str());
+      }
+    }
+    s.Flush();
+  }
+
+  return IsLoaded();
+}
+
+// This function is work for kernel file, others it wil reset load address and
+// return false
+bool DynamicLoaderFreeBSDKernel::KModImageInfo::LoadImageUsingFileAddress(
+    lldb_private::Process *process) {
+  if (IsLoaded())
+    return true;
+
+  if (m_module_sp) {
+    bool changed = false;
+    if (m_module_sp->SetLoadAddress(process->GetTarget(), 0, true, changed))
+      m_stop_id = process->GetStopID();
+  }
+
+  return false;
+}
+
+// Get the head of found_list
+bool DynamicLoaderFreeBSDKernel::ReadKmodsListHeader() {
+  std::lock_guard<decltype(m_mutex)> guard(m_mutex);
+
+  if (m_linker_file_list_struct_addr.IsValid()) {
+    // Get tqh_first struct element from linker_files
+    Status error;
+    addr_t address = m_process->ReadPointerFromMemory(
+        m_linker_file_list_struct_addr.GetLoadAddress(&m_process->GetTarget()),
+        error);
+    if (address != LLDB_INVALID_ADDRESS && error.Success()) {
+      m_linker_file_head_addr = Address(address);
+    } else {
+      m_linker_file_list_struct_addr.Clear();
+      return false;
+    }
+
+    if (!m_linker_file_head_addr.IsValid() ||
+        m_linker_file_head_addr.GetFileAddress() == 0) {
+      m_linker_file_list_struct_addr.Clear();
+      return false;
+    }
+  }
+  return true;
+}
+
+// Parse Kmod info in found_list
+bool DynamicLoaderFreeBSDKernel::ParseKmods(Address linker_files_head_addr) {
+  std::lock_guard<decltype(m_mutex)> guard(m_mutex);
+  KModImageInfo::collection_type linker_files_list;
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+
+  if (!ReadAllKmods(linker_files_head_addr, linker_files_list))
+    return false;
+  LLDB_LOGF(
+      log,
+      "Kmod-changed breakpoint hit, there are %lu kernel modules currently.\n",
+      linker_files_list.size());
+
+  ModuleList &modules = m_process->GetTarget().GetImages();
+  ModuleList remove_modules;
+  ModuleList add_modules;
+
+  for (ModuleSP module : modules.Modules()) {
+    if (is_kernel(module.get()))
+      continue;
+    if (is_kmod(module.get()))
+      remove_modules.AppendIfNeeded(module);
+  }
+
+  m_process->GetTarget().ModulesDidUnload(remove_modules, false);
+
+  for (KModImageInfo &image_info : linker_files_list) {
+    if (m_kld_name_to_uuid.find(image_info.GetName()) !=
+        m_kld_name_to_uuid.end())
+      image_info.SetUUID(m_kld_name_to_uuid[image_info.GetName()]);
+    bool failed_to_load = false;
+    if (!image_info.LoadImageUsingMemoryModule(m_process)) {
+      image_info.LoadImageUsingFileAddress(m_process);
+      failed_to_load = true;
+    } else {
+      m_linker_files_list.push_back(image_info);
+      m_kld_name_to_uuid[image_info.GetName()] = image_info.GetUUID();
+    }
+
+    if (!failed_to_load)
+      add_modules.AppendIfNeeded(image_info.GetModule());
+  }
+  m_process->GetTarget().ModulesDidLoad(add_modules);
+  return true;
+}
+
+// Read all kmod from a given arrays of list
+bool DynamicLoaderFreeBSDKernel::ReadAllKmods(
+    Address linker_files_head_addr,
+    KModImageInfo::collection_type &kmods_list) {
+
+  // Get offset of next member and load address symbol
+  static ConstString kld_off_address_symbol_name("kld_off_address");
+  static ConstString kld_off_next_symbol_name("kld_off_next");
+  static ConstString kld_off_filename_symbol_name("kld_off_filename");
+  static ConstString kld_off_pathname_symbol_name("kld_off_pathname");
+  const Symbol *kld_off_address_symbol =
+      m_kernel_image_info.GetModule()->FindFirstSymbolWithNameAndType(
+          kld_off_address_symbol_name, eSymbolTypeData);
+  const Symbol *kld_off_next_symbol =
+      m_kernel_image_info.GetModule()->FindFirstSymbolWithNameAndType(
+          kld_off_next_symbol_name, eSymbolTypeData);
+  const Symbol *kld_off_filename_symbol =
+      m_kernel_image_info.GetModule()->FindFirstSymbolWithNameAndType(
+          kld_off_filename_symbol_name, eSymbolTypeData);
+  const Symbol *kld_off_pathname_symbol =
+      m_kernel_image_info.GetModule()->FindFirstSymbolWithNameAndType(
+          kld_off_pathname_symbol_name, eSymbolTypeData);
+
+  if (!kld_off_address_symbol || !kld_off_next_symbol ||
+      !kld_off_filename_symbol || !kld_off_pathname_symbol)
+    return false;
+  Status error;
+  const int32_t kld_off_address = m_process->ReadSignedIntegerFromMemory(
+      kld_off_address_symbol->GetAddress().GetLoadAddress(
+          &m_process->GetTarget()),
+      4, 0, error);
+  if (error.Fail())
+    return false;
+  const int32_t kld_off_next = m_process->ReadSignedIntegerFromMemory(
+      kld_off_next_symbol->GetAddress().GetLoadAddress(&m_process->GetTarget()),
+      4, 0, error);
+  if (error.Fail())
+    return false;
+  const int32_t kld_off_filename = m_process->ReadSignedIntegerFromMemory(
+      kld_off_filename_symbol->GetAddress().GetLoadAddress(
+          &m_process->GetTarget()),
+      4, 0, error);
+  if (error.Fail())
+    return false;
+
+  const int32_t kld_off_pathname = m_process->ReadSignedIntegerFromMemory(
+      kld_off_pathname_symbol->GetAddress().GetLoadAddress(
+          &m_process->GetTarget()),
+      4, 0, error);
+  if (error.Fail())
+    return false;
+
+  // Parse KMods
+  addr_t kld_load_addr(LLDB_INVALID_ADDRESS);
+  char kld_filename[255];
+  char kld_pathname[255];
+  addr_t current_kld =
+      linker_files_head_addr.GetLoadAddress(&m_process->GetTarget());
+
+  while (current_kld != 0) {
+    m_process->ReadCStringFromMemory(
+        m_process->ReadPointerFromMemory(current_kld + kld_off_filename, error),
+        kld_filename, sizeof(kld_filename), error);
+    m_process->ReadCStringFromMemory(
+        m_process->ReadPointerFromMemory(current_kld + kld_off_pathname, error),
+        kld_pathname, sizeof(kld_pathname), error);
+    kld_load_addr =
+        m_process->ReadPointerFromMemory(current_kld + kld_off_address, error);
+
+    kmods_list.emplace_back();
+    KModImageInfo &kmod_info = kmods_list.back();
+    kmod_info.SetName(kld_filename);
+    kmod_info.SetLoadAddress(kld_load_addr);
+    kmod_info.SetPath(kld_pathname);
+    current_kld =
+        m_process->ReadPointerFromMemory(current_kld + kld_off_next, error);
+    if (kmod_info.GetName() == "kernel")
+      kmods_list.pop_back();
+    if (error.Fail())
+      return false;
+  }
+
+  return true;
+}
+
+// Read all kmods
+bool DynamicLoaderFreeBSDKernel::ReadAllKmods() {
+  std::lock_guard<decltype(m_mutex)> guard(m_mutex);
+
+  if (ReadKmodsListHeader()) {
+
+    if (m_linker_file_head_addr.IsValid()) {
+      if (!ParseKmods(m_linker_file_head_addr))
+        m_linker_files_list.clear();
+      return true;
+    }
+  }
+
+  return false;
+}
+
+// Load all Kernel Modules
+void DynamicLoaderFreeBSDKernel::LoadKernelModules() {
+  Log *log = GetLog(LLDBLog::DynamicLoader);
+  LLDB_LOGF(log, "DynamicLoaderFreeBSDKernel::LoadKernelModules "
+                 "Start loading Kernel Module");
+
+  // Initialize Kernel Image Information at the first time
+  if (m_kernel_image_info.GetLoadAddress() == LLDB_INVALID_ADDRESS) {
+    ModuleSP module_sp = m_process->GetTarget().GetExecutableModule();
+    if (is_kernel(module_sp.get())) {
+      m_kernel_image_info.SetModule(module_sp);
+      m_kernel_image_info.SetIsKernel(true);
+    }
+
+    // Set name for kernel
+    ConstString kernel_name("freebsd_kernel");
+    module_sp = m_kernel_image_info.GetModule();
+    if (module_sp.get() && module_sp->GetObjectFile() &&
+        !module_sp->GetObjectFile()->GetFileSpec().GetFilename().IsEmpty())
+      kernel_name = module_sp->GetObjectFile()->GetFileSpec().GetFilename();
+    m_kernel_image_info.SetName(kernel_name.AsCString());
+
+    if (m_kernel_image_info.GetLoadAddress() == LLDB_INVALID_ADDRESS) {
+      m_kernel_image_info.SetLoadAddress(m_kernel_load_address);
+
+      // TODO: using file address if not found in the memory
+    }
+
+    // Build In memory Module
+    if (m_kernel_image_info.GetLoadAddress() != LLDB_INVALID_ADDRESS) {
+      // If the kernel is not loaded in the memory, use file to load
+      if (!m_kernel_image_info.LoadImageUsingMemoryModule(m_process))
+        m_kernel_image_info.LoadImageUsingFileAddress(m_process);
+    }
+  }
+
+  LoadOperatingSystemPlugin(false);
+
+  if (!m_kernel_image_info.IsLoaded() || !m_kernel_image_info.GetModule()) {
+    m_kernel_image_info.Clear();
+    return;
+  }
+
+  static ConstString modlist_symbol_name("linker_files");
+
+  const Symbol *symbol =
+      m_kernel_image_info.GetModule()->FindFirstSymbolWithNameAndType(
+          modlist_symbol_name, lldb::eSymbolTypeData);
+
+  if (symbol) {
+    m_linker_file_list_struct_addr = symbol->GetAddress();
+    ReadAllKmods();
+  } else {
+    LLDB_LOGF(log, "DynamicLoaderFreeBSDKernel::LoadKernelModules "
+                   "cannot file modlist symbol");
+  }
+
+  // TODO: Fix Code address and Data Address for other architecture (ARM)
+}
+
+// Update symbol when use kldload by setting callback function on kldload
+void DynamicLoaderFreeBSDKernel::SetNotificationBreakPoint() {}
+
+// Hook called when attach to a process
+void DynamicLoaderFreeBSDKernel::DidAttach() {
+  PrivateInitialize(m_process);
+  Update();
+}
+
+// Hook called after attach to a process
+void DynamicLoaderFreeBSDKernel::DidLaunch() {
+  PrivateInitialize(m_process);
+  Update();
+}
+
+// Clear all member except kernel address
+void DynamicLoaderFreeBSDKernel::Clear(bool clear_process) {
+  std::lock_guard<decltype(m_mutex)> guard(m_mutex);
+  if (clear_process)
+    m_process = nullptr;
+  m_linker_file_head_addr.Clear();
+  m_linker_file_list_struct_addr.Clear();
+  m_kernel_image_info.Clear();
+  m_linker_files_list.clear();
+}
+
+// Reinitialize class
+void DynamicLoaderFreeBSDKernel::PrivateInitialize(Process *process) {
+  Clear(true);
+  m_process = process;
+}
+
+ThreadPlanSP DynamicLoaderFreeBSDKernel::GetStepThroughTrampolinePlan(
+    lldb_private::Thread &thread, bool stop_others) {
+  Log *log = GetLog(LLDBLog::Step);
+  LLDB_LOGF(log, "Could not find symbol for step through.");
+  return {};
+}
+
+Status DynamicLoaderFreeBSDKernel::CanLoadImage() {
+  Status error("shared object cannot be loaded into kernel");
+  return error;
+}