[lldb] [Process/elf-core] Disable for FreeBSD vmcores

[mgorny]

Summary

Recognize FreeBSD vmcores (kernel core dumps) through OS ABI = 0xFF
+ ELF version = 0, and do not process them via the elf-core plugin.
While these files use ELF as a container format, they contain raw memory
dump rather than proper VM segments and therefore are not usable
to the elf-core plugin.

[emaste]

lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp

67 ↗

(On Diff #391358)

Maybe "FreeBSD full ELF vmcore" or such? We may have three different FreeBSD vmcore formats to deal with

1. kernel-generated ELF dumps (sysctl debug.minidump=0)
2. kernel-generated minidumps (sysctl debug.minidump=1)
3. minidump post-processed by (a fixed version of) https://reviews.freebsd.org/D19253

[mgorny]

Try making the comment more precise.

[mgorny]

Fix thinko.

lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp

67 ↗

(On Diff #391358)

Good idea. I've changed it to use "full memory dump" to follow the Handbook, and added "raw" to make it clearer we're not talking of the converted version.

[mgorny]

Add arm64 support, simplify logic in ThreadFreeBSDKernel, handle unsupported architectures gracefully (instead of crashing).

[mgorny]

Sorry, accidentally uploaded the patch to the wrong revision.

lldb/source/Plugins/Process/CMakeLists.txt

elseif (CMAKE_SYSTEM_NAME MATCHES "Darwin")
   add_subdirectory(MacOSX-Kernel)
 endif()
 add_subdirectory(scripted)
 add_subdirectory(gdb-remote)
 add_subdirectory(Utility)
 add_subdirectory(elf-core)
 add_subdirectory(mach-core)
 add_subdirectory(minidump)
+add_subdirectory(FreeBSDKernel)

lldb/source/Plugins/Process/FreeBSDKernel/CMakeLists.txt

+find_library(FBSDVMCORE fbsdvmcore)
+
+if (NOT FBSDVMCORE)
+  message(STATUS "Skipping FreeBSDKernel plugin due to missing libfbsdvmcore")
+  return()
+endif()
+
+add_lldb_library(lldbPluginProcessFreeBSDKernel PLUGIN
+  ProcessFreeBSDKernel.cpp
+  RegisterContextFreeBSDKernel_arm64.cpp
+  RegisterContextFreeBSDKernel_x86_64.cpp
+  ThreadFreeBSDKernel.cpp
+
+  LINK_LIBS
+    lldbCore
+    lldbTarget
+    ${FBSDVMCORE}
+  LINK_COMPONENTS
+    Support
+  )

lldb/source/Plugins/Process/FreeBSDKernel/ProcessFreeBSDKernel.h

+//===-- ProcessFreeBSDKernel.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_PROCESS_FREEBSDKERNEL_PROCESSFREEBSDKERNEL_H
+#define LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_PROCESSFREEBSDKERNEL_H
+
+#include "lldb/Target/PostMortemProcess.h"
+
+class ProcessFreeBSDKernel : public lldb_private::PostMortemProcess {
+public:
+  ProcessFreeBSDKernel(lldb::TargetSP target_sp, lldb::ListenerSP listener,
+                       const lldb_private::FileSpec &core_file, void *fvc);
+
+  ~ProcessFreeBSDKernel() override;
+
+  static lldb::ProcessSP
+  CreateInstance(lldb::TargetSP target_sp, lldb::ListenerSP listener,
+                 const lldb_private::FileSpec *crash_file_path,
+                 bool can_connect);
+
+  static void Initialize();
+
+  static void Terminate();
+
+  static llvm::StringRef GetPluginNameStatic() { return "freebsd-kernel"; }
+
+  static llvm::StringRef GetPluginDescriptionStatic() {
+    return "FreeBSD kernel vmcore debugging plug-in.";
+  }
+
+  llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }
+
+  lldb_private::Status DoDestroy() override;
+
+  bool CanDebug(lldb::TargetSP target_sp,
+                bool plugin_specified_by_name) override;
+
+  void RefreshStateAfterStop() override;
+
+  lldb_private::Status DoLoadCore() override;
+
+  size_t DoReadMemory(lldb::addr_t addr, void *buf, size_t size,
+                      lldb_private::Status &error) override;
+
+protected:
+  bool DoUpdateThreadList(lldb_private::ThreadList &old_thread_list,
+                          lldb_private::ThreadList &new_thread_list) override;
+
+private:
+  void *m_fvc;
+};
+
+#endif // LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_PROCESSFREEBSDKERNEL_H

lldb/source/Plugins/Process/FreeBSDKernel/ProcessFreeBSDKernel.cpp

+//===-- ProcessFreeBSDKernel.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 "lldb/Core/Module.h"
+#include "lldb/Core/PluginManager.h"
+
+#include "ProcessFreeBSDKernel.h"
+#include "ThreadFreeBSDKernel.h"
+
+#include <fvc.h>
+
+using namespace lldb;
+using namespace lldb_private;
+
+LLDB_PLUGIN_DEFINE(ProcessFreeBSDKernel)
+
+ProcessFreeBSDKernel::ProcessFreeBSDKernel(lldb::TargetSP target_sp,
+                                           ListenerSP listener_sp,
+                                           const FileSpec &core_file, void *fvc)
+    : PostMortemProcess(target_sp, listener_sp), m_fvc(fvc) {}
+
+ProcessFreeBSDKernel::~ProcessFreeBSDKernel() {
+  if (m_fvc)
+    fvc_close(static_cast<fvc_t *>(m_fvc));
+}
+
+lldb::ProcessSP ProcessFreeBSDKernel::CreateInstance(lldb::TargetSP target_sp,
+                                                     ListenerSP listener_sp,
+                                                     const FileSpec *crash_file,
+                                                     bool can_connect) {
+  lldb::ProcessSP process_sp;
+  if (crash_file && !can_connect) {
+    fvc_t *fvc = fvc_open(
+        target_sp->GetExecutableModule()->GetFileSpec().GetPath().c_str(),
+        crash_file->GetPath().c_str(), nullptr, nullptr, nullptr);
+    if (fvc)
+      process_sp = std::make_shared<ProcessFreeBSDKernel>(
+          target_sp, listener_sp, *crash_file, fvc);
+  }
+  return process_sp;
+}
+
+void ProcessFreeBSDKernel::Initialize() {
+  static llvm::once_flag g_once_flag;
+
+  llvm::call_once(g_once_flag, []() {
+    PluginManager::RegisterPlugin(GetPluginNameStatic(),
+                                  GetPluginDescriptionStatic(), CreateInstance);
+  });
+}
+
+void ProcessFreeBSDKernel::Terminate() {
+  PluginManager::UnregisterPlugin(ProcessFreeBSDKernel::CreateInstance);
+}
+
+Status ProcessFreeBSDKernel::DoDestroy() { return Status(); }
+
+bool ProcessFreeBSDKernel::CanDebug(lldb::TargetSP target_sp,
+                                    bool plugin_specified_by_name) {
+  return true;
+}
+
+void ProcessFreeBSDKernel::RefreshStateAfterStop() {}
+
+bool ProcessFreeBSDKernel::DoUpdateThreadList(ThreadList &old_thread_list,
+                                              ThreadList &new_thread_list) {
+  if (old_thread_list.GetSize(false) == 0) {
+    // Make up the thread the first time this is called so we can set our one
+    // and only core thread state up.
+
+    // We cannot construct a thread without a register context as that crashes
+    // LLDB but we can construct a process without threads to provide minimal
+    // memory reading support.
+    switch (GetTarget().GetArchitecture().GetMachine()) {
+    case llvm::Triple::aarch64:
+    case llvm::Triple::x86_64:
+      break;
+    default:
+      return false;
+    }
+
+    const Symbol *pcb_sym =
+        GetTarget().GetExecutableModule()->FindFirstSymbolWithNameAndType(
+            ConstString("dumppcb"));
+    ThreadSP thread_sp(new ThreadFreeBSDKernel(
+        *this, 1, pcb_sym ? pcb_sym->GetFileAddress() : LLDB_INVALID_ADDRESS));
+    new_thread_list.AddThread(thread_sp);
+  } else {
+    const uint32_t num_threads = old_thread_list.GetSize(false);
+    for (uint32_t i = 0; i < num_threads; ++i)
+      new_thread_list.AddThread(old_thread_list.GetThreadAtIndex(i, false));
+  }
+  return new_thread_list.GetSize(false) > 0;
+}
+
+Status ProcessFreeBSDKernel::DoLoadCore() {
+  // The core is already loaded by CreateInstance().
+  return Status();
+}
+
+size_t ProcessFreeBSDKernel::DoReadMemory(lldb::addr_t addr, void *buf,
+                                          size_t size, Status &error) {
+  ssize_t rd = fvc_read(static_cast<fvc_t *>(m_fvc), addr, buf, size);
+  if (rd < 0 || static_cast<size_t>(rd) != size) {
+    error.SetErrorStringWithFormat("Reading memory failed: %s",
+                                   fvc_geterr(static_cast<fvc_t *>(m_fvc)));
+    return rd > 0 ? rd : 0;
+  }
+  return rd;
+}

lldb/source/Plugins/Process/FreeBSDKernel/RegisterContextFreeBSDKernel_arm64.h

+//===-- RegisterContextFreeBSDKernel_arm64.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_PROCESS_FREEBSDKERNEL_REGISTERCONTEXTFREEBSDKERNEL_ARM64_H
+#define LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_REGISTERCONTEXTFREEBSDKERNEL_ARM64_H
+
+#include "Plugins/Process/Utility/RegisterContextPOSIX_arm64.h"
+#include "Plugins/Process/elf-core/RegisterUtilities.h"
+
+class RegisterContextFreeBSDKernel_arm64 : public RegisterContextPOSIX_arm64 {
+public:
+  RegisterContextFreeBSDKernel_arm64(
+      lldb_private::Thread &thread,
+      std::unique_ptr<RegisterInfoPOSIX_arm64> register_info_up,
+      lldb::addr_t pcb_addr);
+
+  bool ReadRegister(const lldb_private::RegisterInfo *reg_info,
+                    lldb_private::RegisterValue &value) override;
+
+  bool WriteRegister(const lldb_private::RegisterInfo *reg_info,
+                     const lldb_private::RegisterValue &value) override;
+
+protected:
+  bool ReadGPR() override;
+
+  bool ReadFPR() override;
+
+  bool WriteGPR() override;
+
+  bool WriteFPR() override;
+
+private:
+  lldb::addr_t m_pcb_addr;
+};
+
+#endif // LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_REGISTERCONTEXTFREEBSDKERNEL_ARM64_H

lldb/source/Plugins/Process/FreeBSDKernel/RegisterContextFreeBSDKernel_arm64.cpp

+//===-- RegisterContextFreeBSDKernel_arm64.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 "RegisterContextFreeBSDKernel_arm64.h"
+#include "Plugins/Process/Utility/lldb-arm64-register-enums.h"
+
+#include "lldb/Target/Process.h"
+#include "lldb/Target/Thread.h"
+#include "lldb/Utility/RegisterValue.h"
+#include "llvm/Support/Endian.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+RegisterContextFreeBSDKernel_arm64::RegisterContextFreeBSDKernel_arm64(
+    Thread &thread, std::unique_ptr<RegisterInfoPOSIX_arm64> register_info_up,
+    lldb::addr_t pcb_addr)
+    : RegisterContextPOSIX_arm64(thread, std::move(register_info_up)),
+      m_pcb_addr(pcb_addr) {}
+
+bool RegisterContextFreeBSDKernel_arm64::ReadGPR() { return true; }
+
+bool RegisterContextFreeBSDKernel_arm64::ReadFPR() { return true; }
+
+bool RegisterContextFreeBSDKernel_arm64::WriteGPR() {
+  assert(0);
+  return false;
+}
+
+bool RegisterContextFreeBSDKernel_arm64::WriteFPR() {
+  assert(0);
+  return false;
+}
+
+bool RegisterContextFreeBSDKernel_arm64::ReadRegister(
+    const RegisterInfo *reg_info, RegisterValue &value) {
+  if (m_pcb_addr == LLDB_INVALID_ADDRESS)
+    return false;
+
+  struct {
+    llvm::support::ulittle64_t x[30];
+    llvm::support::ulittle64_t lr;
+    llvm::support::ulittle64_t _reserved;
+    llvm::support::ulittle64_t sp;
+  } pcb;
+
+  Status error;
+  size_t rd =
+      m_thread.GetProcess()->ReadMemory(m_pcb_addr, &pcb, sizeof(pcb), error);
+  if (rd != sizeof(pcb))
+    return false;
+
+  uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
+  switch (reg) {
+  case gpr_x0_arm64:
+  case gpr_x1_arm64:
+  case gpr_x2_arm64:
+  case gpr_x3_arm64:
+  case gpr_x4_arm64:
+  case gpr_x5_arm64:
+  case gpr_x6_arm64:
+  case gpr_x7_arm64:
+  case gpr_x8_arm64:
+  case gpr_x9_arm64:
+  case gpr_x10_arm64:
+  case gpr_x11_arm64:
+  case gpr_x12_arm64:
+  case gpr_x13_arm64:
+  case gpr_x14_arm64:
+  case gpr_x15_arm64:
+  case gpr_x16_arm64:
+  case gpr_x17_arm64:
+  case gpr_x18_arm64:
+  case gpr_x19_arm64:
+  case gpr_x20_arm64:
+  case gpr_x21_arm64:
+  case gpr_x22_arm64:
+  case gpr_x23_arm64:
+  case gpr_x24_arm64:
+  case gpr_x25_arm64:
+  case gpr_x26_arm64:
+  case gpr_x27_arm64:
+  case gpr_x28_arm64:
+  case gpr_fp_arm64:
+    assert(gpr_fp_arm64 - gpr_x0_arm64 == 30);
+    value = pcb.x[reg - gpr_x0_arm64];
+    break;
+  case gpr_sp_arm64:
+    value = pcb.sp;
+    break;
+  case gpr_pc_arm64:
+    // The pc of crashing thread is stored in lr.
+    value = pcb.lr;
+    break;
+  default:
+    return false;
+  }
+  return true;
+}
+
+bool RegisterContextFreeBSDKernel_arm64::WriteRegister(
+    const RegisterInfo *reg_info, const RegisterValue &value) {
+  return false;
+}

lldb/source/Plugins/Process/FreeBSDKernel/RegisterContextFreeBSDKernel_x86_64.h

+//===-- RegisterContextFreeBSDKernel_x86_64.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_PROCESS_FREEBSDKERNEL_REGISTERCONTEXTFREEBSDKERNEL_X86_64_H
+#define LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_REGISTERCONTEXTFREEBSDKERNEL_X86_64_H
+
+#include "Plugins/Process/Utility/RegisterContextPOSIX_x86.h"
+#include "Plugins/Process/elf-core/RegisterUtilities.h"
+
+class RegisterContextFreeBSDKernel_x86_64 : public RegisterContextPOSIX_x86 {
+public:
+  RegisterContextFreeBSDKernel_x86_64(
+      lldb_private::Thread &thread,
+      lldb_private::RegisterInfoInterface *register_info,
+      lldb::addr_t pcb_addr);
+
+  bool ReadRegister(const lldb_private::RegisterInfo *reg_info,
+                    lldb_private::RegisterValue &value) override;
+
+  bool WriteRegister(const lldb_private::RegisterInfo *reg_info,
+                     const lldb_private::RegisterValue &value) override;
+
+protected:
+  bool ReadGPR() override;
+
+  bool ReadFPR() override;
+
+  bool WriteGPR() override;
+
+  bool WriteFPR() override;
+
+private:
+  lldb::addr_t m_pcb_addr;
+};
+
+#endif // LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_REGISTERCONTEXTFREEBSDKERNEL_X86_64_H

lldb/source/Plugins/Process/FreeBSDKernel/RegisterContextFreeBSDKernel_x86_64.cpp

+//===-- RegisterContextFreeBSDKernel_x86_64.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 "RegisterContextFreeBSDKernel_x86_64.h"
+
+#include "lldb/Target/Process.h"
+#include "lldb/Target/Thread.h"
+#include "lldb/Utility/RegisterValue.h"
+#include "llvm/Support/Endian.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+RegisterContextFreeBSDKernel_x86_64::RegisterContextFreeBSDKernel_x86_64(
+    Thread &thread, RegisterInfoInterface *register_info, lldb::addr_t pcb_addr)
+    : RegisterContextPOSIX_x86(thread, 0, register_info), m_pcb_addr(pcb_addr) {
+}
+
+bool RegisterContextFreeBSDKernel_x86_64::ReadGPR() { return true; }
+
+bool RegisterContextFreeBSDKernel_x86_64::ReadFPR() { return true; }
+
+bool RegisterContextFreeBSDKernel_x86_64::WriteGPR() {
+  assert(0);
+  return false;
+}
+
+bool RegisterContextFreeBSDKernel_x86_64::WriteFPR() {
+  assert(0);
+  return false;
+}
+
+bool RegisterContextFreeBSDKernel_x86_64::ReadRegister(
+    const RegisterInfo *reg_info, RegisterValue &value) {
+  if (m_pcb_addr == LLDB_INVALID_ADDRESS)
+    return false;
+
+  struct {
+    llvm::support::ulittle64_t r15;
+    llvm::support::ulittle64_t r14;
+    llvm::support::ulittle64_t r13;
+    llvm::support::ulittle64_t r12;
+    llvm::support::ulittle64_t rbp;
+    llvm::support::ulittle64_t rsp;
+    llvm::support::ulittle64_t rbx;
+    llvm::support::ulittle64_t rip;
+  } pcb;
+
+  Status error;
+  size_t rd =
+      m_thread.GetProcess()->ReadMemory(m_pcb_addr, &pcb, sizeof(pcb), error);
+  if (rd != sizeof(pcb))
+    return false;
+
+  uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
+  switch (reg) {
+#define REG(x)                                                                 \
+  case lldb_##x##_x86_64:                                                      \
+    value = pcb.x;                                                             \
+    break;
+
+    REG(r15);
+    REG(r14);
+    REG(r13);
+    REG(r12);
+    REG(rbp);
+    REG(rsp);
+    REG(rbx);
+    REG(rip);
+
+#undef REG
+
+  default:
+    return false;
+  }
+
+  return true;
+}
+
+bool RegisterContextFreeBSDKernel_x86_64::WriteRegister(
+    const RegisterInfo *reg_info, const RegisterValue &value) {
+  return false;
+}

lldb/source/Plugins/Process/FreeBSDKernel/ThreadFreeBSDKernel.h

+//===-- ThreadFreeBSDKernel.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_PROCESS_FREEBSDKERNEL_THREADFREEBSDKERNEL_H
+#define LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_THREADFREEBSDKERNEL_H
+
+#include "lldb/Target/Thread.h"
+
+class ThreadFreeBSDKernel : public lldb_private::Thread {
+public:
+  ThreadFreeBSDKernel(lldb_private::Process &process, lldb::tid_t tid,
+                      lldb::addr_t pcb_addr);
+
+  ~ThreadFreeBSDKernel() override;
+
+  void RefreshStateAfterStop() override;
+
+  lldb::RegisterContextSP GetRegisterContext() override;
+
+  lldb::RegisterContextSP
+  CreateRegisterContextForFrame(lldb_private::StackFrame *frame) override;
+
+protected:
+  bool CalculateStopInfo() override;
+
+private:
+  lldb::RegisterContextSP m_thread_reg_ctx_sp;
+  lldb::addr_t m_pcb_addr;
+};
+
+#endif // LLDB_SOURCE_PLUGINS_PROCESS_FREEBSDKERNEL_THREADFREEBSDKERNEL_H

lldb/source/Plugins/Process/FreeBSDKernel/ThreadFreeBSDKernel.cpp

+//===-- ThreadFreeBSDKernel.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 "ThreadFreeBSDKernel.h"
+
+#include "lldb/Target/Unwind.h"
+#include "lldb/Utility/Log.h"
+
+#include "Plugins/Process/Utility/RegisterContextFreeBSD_x86_64.h"
+#include "Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h"
+#include "ProcessFreeBSDKernel.h"
+#include "RegisterContextFreeBSDKernel_arm64.h"
+#include "RegisterContextFreeBSDKernel_x86_64.h"
+#include "ThreadFreeBSDKernel.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+ThreadFreeBSDKernel::ThreadFreeBSDKernel(Process &process, lldb::tid_t tid,
+                                         lldb::addr_t pcb_addr)
+    : Thread(process, tid), m_pcb_addr(pcb_addr) {}
+
+ThreadFreeBSDKernel::~ThreadFreeBSDKernel() {}
+
+void ThreadFreeBSDKernel::RefreshStateAfterStop() {}
+
+lldb::RegisterContextSP ThreadFreeBSDKernel::GetRegisterContext() {
+  if (!m_reg_context_sp)
+    m_reg_context_sp = CreateRegisterContextForFrame(nullptr);
+  return m_reg_context_sp;
+}
+
+lldb::RegisterContextSP
+ThreadFreeBSDKernel::CreateRegisterContextForFrame(StackFrame *frame) {
+  RegisterContextSP reg_ctx_sp;
+  uint32_t concrete_frame_idx = 0;
+
+  if (frame)
+    concrete_frame_idx = frame->GetConcreteFrameIndex();
+
+  if (concrete_frame_idx == 0) {
+    if (m_thread_reg_ctx_sp)
+      return m_thread_reg_ctx_sp;
+
+    ProcessFreeBSDKernel *process =
+        static_cast<ProcessFreeBSDKernel *>(GetProcess().get());
+    ArchSpec arch = process->GetTarget().GetArchitecture();
+
+    switch (arch.GetMachine()) {
+    case llvm::Triple::aarch64:
+      m_thread_reg_ctx_sp =
+          std::make_shared<RegisterContextFreeBSDKernel_arm64>(
+              *this, std::make_unique<RegisterInfoPOSIX_arm64>(arch, 0),
+              m_pcb_addr);
+      break;
+    case llvm::Triple::x86_64:
+      m_thread_reg_ctx_sp =
+          std::make_shared<RegisterContextFreeBSDKernel_x86_64>(
+              *this, new RegisterContextFreeBSD_x86_64(arch), m_pcb_addr);
+      break;
+    default:
+      assert(false && "Unsupported architecture passed to ThreadFreeBSDKernel");
+      break;
+    }
+
+    reg_ctx_sp = m_thread_reg_ctx_sp;
+  } else {
+    reg_ctx_sp = GetUnwinder().CreateRegisterContextForFrame(frame);
+  }
+  return reg_ctx_sp;
+}
+
+bool ThreadFreeBSDKernel::CalculateStopInfo() { return false; }