Index: lldb/source/Plugins/Process/OpenBSDKernel/RegisterContextOpenBSDKernel_i386.cpp
--- lldb/source/Plugins/Process/OpenBSDKernel/RegisterContextOpenBSDKernel_i386.cpp.orig
+++ lldb/source/Plugins/Process/OpenBSDKernel/RegisterContextOpenBSDKernel_i386.cpp
@@ -0,0 +1,114 @@
+//===-- RegisterContextOpenBSDKernel_i386.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
+//
+//===----------------------------------------------------------------------===//
+
+#if defined(__OpenBSD__)
+#include <sys/types.h>
+#include <sys/time.h>
+#define _KERNEL
+#include <machine/cpu.h>
+#undef _KERNEL
+#include <machine/pcb.h>
+#include <frame.h>
+#endif
+
+#include "RegisterContextOpenBSDKernel_i386.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;
+
+RegisterContextOpenBSDKernel_i386::RegisterContextOpenBSDKernel_i386(
+    Thread &thread, RegisterInfoInterface *register_info, lldb::addr_t pcb_addr)
+    : RegisterContextPOSIX_x86(thread, 0, register_info), m_pcb_addr(pcb_addr) {
+}
+
+bool RegisterContextOpenBSDKernel_i386::ReadGPR() { return true; }
+
+bool RegisterContextOpenBSDKernel_i386::ReadFPR() { return true; }
+
+bool RegisterContextOpenBSDKernel_i386::WriteGPR() {
+  assert(0);
+  return false;
+}
+
+bool RegisterContextOpenBSDKernel_i386::WriteFPR() {
+  assert(0);
+  return false;
+}
+
+bool RegisterContextOpenBSDKernel_i386::ReadRegister(
+    const RegisterInfo *reg_info, RegisterValue &value) {
+  if (m_pcb_addr == LLDB_INVALID_ADDRESS)
+    return false;
+
+#ifdef __i386__
+  struct pcb pcb;
+
+  Status error;
+  size_t rd =
+      m_thread.GetProcess()->ReadMemory(m_pcb_addr, &pcb, sizeof(pcb), error);
+  if (rd != sizeof(pcb))
+    return false;
+
+  if ((pcb.pcb_flags & PCB_SAVECTX) != 0) {
+    uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
+    switch (reg) {
+      return true;
+    case lldb_esp_i386:
+      value = (u_int32_t)pcb.pcb_ebp;
+      return true;
+    case lldb_ebp_i386:
+      value = m_thread.GetProcess()->ReadPointerFromMemory(pcb.pcb_ebp, error);
+    case lldb_eip_i386:
+      value = m_thread.GetProcess()->ReadPointerFromMemory(pcb.pcb_ebp + 4,
+							   error);
+      return true;
+    }
+    return false;
+  }
+
+  /*
+    Usually pcb is written in `cpu_switchto` function. This function writes
+    registers as same as the structure of  `swichframe`  in the stack.
+    We read the frame if it is.
+   */
+  struct switchframe sf;
+  rd = m_thread.GetProcess()->ReadMemory(pcb.pcb_esp, &sf, sizeof(sf), error);
+  if (rd != sizeof(sf))
+    return false;
+
+  uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
+  switch (reg) {
+#define PCBREG(x, offset)                                              \
+    case lldb_##x##_i386:                                              \
+      value = (u_int32_t)(pcb.pcb_##x + (offset));                     \
+      return true;
+#define SFREG(x)							\
+    case lldb_##x##_i386:						\
+      value = sf.sf_##x;						\
+      return true;
+
+    SFREG(edi);
+    SFREG(esi);
+    SFREG(ebx);
+    SFREG(eip);
+    PCBREG(ebp);
+    PCBREG(esp);
+  }
+#endif
+  return false;
+}
+
+bool RegisterContextOpenBSDKernel_i386::WriteRegister(
+    const RegisterInfo *reg_info, const RegisterValue &value) {
+  return false;
+}
