[Windows] Added support of watchpoints to `NativeProcessWindows`

[aleksandr.urakov]

Summary

This patch adds support of watchpoints to the new NativeProcessWindows plugin. The same tests as in D67168 pass with these changes when the old plugin is turned off, so they will cover this functionality when the old plugin is gone.

[labath]

This looks mostly fine to me. There's still a lot more copy-pasta between the three kinds of register contexts than I'd like (e.g. on linux, all of these three cases are handled by a single class), but I don't have a clear idea what to do about that at this point.

lldb/source/Plugins/Process/Windows/Common/NativeProcessWindows.cpp

446–448

Though the std::stringstream classes are used in a couple of places, we usually try to stay away from all std::stream classes. In this case, I'd just do a llvm::formatv(...).str()

[labath]

Btw, in the context of D67954, I realized that I don't know how to actually enable the usage of lldb-server in lldb on windows. Can you share how you did that ?

[aleksandr.urakov]

Update the patch due to Pavel's request.

[aleksandr.urakov]

In D67222#1680613, @labath wrote:

Btw, in the context of D67954, I realized that I don't know how to actually enable the usage of lldb-server in lldb on windows. Can you share how you did that ?

Hi, Pavel! Thanks for taking a look. To be honest, I just have commented out content of the ProcessWindows::Initialize() function to test this :)

[labath]

Cool, maybe we should have a setting/environment variable/something to control which plugin is used. That would make it easier to switch between the two implementations.

[aleksandr.urakov]

Thank you! I've added a switch in a manner similar to one that Zachary has chosen for SymbolFilePDB/NativePDB plugins here: D68258

lldb/source/Plugins/Process/Windows/Common/NativeProcessWindows.cpp

NativeProcessWindows::OnDebugException(bool first_chance,
   static bool initial_stop = false;
   if (!first_chance) {
     SetState(eStateStopped, false);
   }
 
   ExceptionResult result = ExceptionResult::SendToApplication;
   switch (record.GetExceptionCode()) {
   case DWORD(STATUS_SINGLE_STEP):
-  case STATUS_WX86_SINGLE_STEP:
+  case STATUS_WX86_SINGLE_STEP: {
+    uint32_t wp_id = LLDB_INVALID_INDEX32;
+    if (NativeThreadWindows *thread = GetThreadByID(record.GetThreadID())) {
+      NativeRegisterContextWindows &reg_ctx = thread->GetRegisterContext();
+      Status error =
+          reg_ctx.GetWatchpointHitIndex(wp_id, record.GetExceptionAddress());
+      if (error.Fail())
+        LLDB_LOG(log,
+                 "received error while checking for watchpoint hits, pid = "
+                 "{0}, error = {1}",
+                 thread->GetID(), error);
+      if (wp_id != LLDB_INVALID_INDEX32) {
+        addr_t wp_addr = reg_ctx.GetWatchpointAddress(wp_id);
+        addr_t wp_hit_addr = reg_ctx.GetWatchpointHitAddress(wp_id);
+        std::string desc =
+            formatv("{0} {1} {2}", wp_addr, wp_id, wp_hit_addr).str();
+        StopThread(record.GetThreadID(), StopReason::eStopReasonWatchpoint,
+                   desc);
+      }
+    }
+    if (wp_id == LLDB_INVALID_INDEX32)
       StopThread(record.GetThreadID(), StopReason::eStopReasonTrace);
+
     SetState(eStateStopped, true);
 
     // Continue the debugger.
     return ExceptionResult::MaskException;
-
+  }
   case DWORD(STATUS_BREAKPOINT):
   case STATUS_WX86_BREAKPOINT:
     if (FindSoftwareBreakpoint(record.GetExceptionAddress())) {
       LLDB_LOG(log, "Hit non-loader breakpoint at address {0:x}.",
                record.GetExceptionAddress());
 
       StopThread(record.GetThreadID(), StopReason::eStopReasonBreakpoint);
 
else
       result = ExceptionResult::BreakInDebugger;
   }
 
   return result;
 }
 
 void NativeProcessWindows::OnCreateThread(const HostThread &new_thread) {
   llvm::sys::ScopedLock lock(m_mutex);
-  m_threads.push_back(
-      std::make_unique<NativeThreadWindows>(*this, new_thread));
+
+  auto thread = std::make_unique<NativeThreadWindows>(*this, new_thread);
+  thread->GetRegisterContext().ClearAllHardwareWatchpoints();
+  for (const auto &pair : GetWatchpointMap()) {
+    const NativeWatchpoint &wp = pair.second;
+    thread->SetWatchpoint(wp.m_addr, wp.m_size, wp.m_watch_flags,
+                          wp.m_hardware);
+  }
+
+  m_threads.push_back(std::move(thread));
 }
 
 void NativeProcessWindows::OnExitThread(lldb::tid_t thread_id,
                                         uint32_t exit_code) {
   llvm::sys::ScopedLock lock(m_mutex);
   NativeThreadWindows *thread = GetThreadByID(thread_id);
   if (!thread)
     return;

lldb/source/Plugins/Process/Windows/Common/NativeRegisterContextWindows_WoW64.h

Status GetWatchpointHitIndex(uint32_t &wp_index,
                                lldb::addr_t trap_addr) override;
 
   Status IsWatchpointVacant(uint32_t wp_index, bool &is_vacant) override;
 
   bool ClearHardwareWatchpoint(uint32_t wp_index) override;
 
   Status ClearAllHardwareWatchpoints() override;
 
-  Status SetHardwareWatchpointWithIndex(lldb::addr_t addr, size_t size,
-                                        uint32_t watch_flags,
-                                        uint32_t wp_index);
-
   uint32_t SetHardwareWatchpoint(lldb::addr_t addr, size_t size,
                                  uint32_t watch_flags) override;
 
   lldb::addr_t GetWatchpointAddress(uint32_t wp_index) override;
 
   uint32_t NumSupportedHardwareWatchpoints() override;
 
 protected:
   Status GPRRead(const uint32_t reg, RegisterValue &reg_value);
   Status GPRWrite(const uint32_t reg, const RegisterValue &reg_value);
 
+  Status DRRead(const uint32_t reg, RegisterValue &reg_value);
+  Status DRWrite(const uint32_t reg, const RegisterValue &reg_value);
+
 private:
+  Status ApplyHardwareBreakpoint(uint32_t wp_index, lldb::addr_t addr,
+                                 size_t size, uint32_t flags);
+
   bool IsGPR(uint32_t reg_index) const;
+  bool IsDR(uint32_t reg_index) const;
 };
 
 } // namespace lldb_private
 
 #endif // liblldb_NativeRegisterContextWindows_WoW64_h_
 #endif // defined(__x86_64__) || defined(_M_X64)

lldb/source/Plugins/Process/Windows/Common/NativeRegisterContextWindows_WoW64.cpp

 CreateRegisterInfoInterface(const ArchSpec &target_arch) {
   // i686 32bit instruction set.
   assert((target_arch.GetAddressByteSize() == 4 &&
           HostInfo::GetArchitecture().GetAddressByteSize() == 8) &&
          "Register setting path assumes this is a 64-bit host");
   return new RegisterContextWindows_i386(target_arch);
 }
 
-static Status GetWoW64ThreadContextHelper(lldb::thread_t thread_handle,
-                                          PWOW64_CONTEXT context_ptr) {
+static Status
+GetWoW64ThreadContextHelper(lldb::thread_t thread_handle,
+                            PWOW64_CONTEXT context_ptr,
+                            const DWORD control_flag = kWoW64ContextFlags) {
   Log *log = ProcessWindowsLog::GetLogIfAny(WINDOWS_LOG_REGISTERS);
   Status error;
   memset(context_ptr, 0, sizeof(::WOW64_CONTEXT));
-  context_ptr->ContextFlags = kWoW64ContextFlags;
+  context_ptr->ContextFlags = control_flag;
   if (!::Wow64GetThreadContext(thread_handle, context_ptr)) {
     error.SetError(GetLastError(), eErrorTypeWin32);
     LLDB_LOG(log, "{0} Wow64GetThreadContext failed with error {1}",
              __FUNCTION__, error);
     return error;
   }
   return Status();
 }
NativeRegisterContextWindows_WoW64::NativeRegisterContextWindows_WoW64(
     const ArchSpec &target_arch, NativeThreadProtocol &native_thread)
     : NativeRegisterContextWindows(native_thread,
                                    CreateRegisterInfoInterface(target_arch)) {}
 
 bool NativeRegisterContextWindows_WoW64::IsGPR(uint32_t reg_index) const {
   return (reg_index >= k_first_gpr_i386 && reg_index < k_first_alias_i386);
 }
 
+bool NativeRegisterContextWindows_WoW64::IsDR(uint32_t reg_index) const {
+  return (reg_index >= lldb_dr0_i386 && reg_index <= lldb_dr7_i386);
+}
+
 uint32_t NativeRegisterContextWindows_WoW64::GetRegisterSetCount() const {
   return k_num_register_sets;
 }
 
 const RegisterSet *
 NativeRegisterContextWindows_WoW64::GetRegisterSet(uint32_t set_index) const {
   if (set_index >= k_num_register_sets)
     return nullptr;
NativeRegisterContextWindows_WoW64::GPRWrite(const uint32_t reg,
   case lldb_es_i386:
     tls_context.SegEs = reg_value.GetAsUInt32();
     break;
   }
 
   return SetWoW64ThreadContextHelper(thread_handle, &tls_context);
 }
 
+Status NativeRegisterContextWindows_WoW64::DRRead(const uint32_t reg,
+                                                  RegisterValue &reg_value) {
+  ::WOW64_CONTEXT tls_context;
+  DWORD context_flag = CONTEXT_DEBUG_REGISTERS;
+  Status error = GetWoW64ThreadContextHelper(GetThreadHandle(), &tls_context,
+                                             context_flag);
+  if (error.Fail())
+    return error;
+
+  switch (reg) {
+  case lldb_dr0_i386:
+    reg_value.SetUInt32(tls_context.Dr0);
+    break;
+  case lldb_dr1_i386:
+    reg_value.SetUInt32(tls_context.Dr1);
+    break;
+  case lldb_dr2_i386:
+    reg_value.SetUInt32(tls_context.Dr2);
+    break;
+  case lldb_dr3_i386:
+    reg_value.SetUInt32(tls_context.Dr3);
+    break;
+  case lldb_dr4_i386:
+    return Status("register DR4 is obsolete");
+  case lldb_dr5_i386:
+    return Status("register DR5 is obsolete");
+  case lldb_dr6_i386:
+    reg_value.SetUInt32(tls_context.Dr6);
+    break;
+  case lldb_dr7_i386:
+    reg_value.SetUInt32(tls_context.Dr7);
+    break;
+  }
+
+  return {};
+}
+
+Status
+NativeRegisterContextWindows_WoW64::DRWrite(const uint32_t reg,
+                                            const RegisterValue &reg_value) {
+  ::WOW64_CONTEXT tls_context;
+  DWORD context_flag = CONTEXT_DEBUG_REGISTERS;
+  auto thread_handle = GetThreadHandle();
+  Status error =
+      GetWoW64ThreadContextHelper(thread_handle, &tls_context, context_flag);
+  if (error.Fail())
+    return error;
+
+  switch (reg) {
+  case lldb_dr0_i386:
+    tls_context.Dr0 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr1_i386:
+    tls_context.Dr1 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr2_i386:
+    tls_context.Dr2 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr3_i386:
+    tls_context.Dr3 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr4_i386:
+    return Status("register DR4 is obsolete");
+  case lldb_dr5_i386:
+    return Status("register DR5 is obsolete");
+  case lldb_dr6_i386:
+    tls_context.Dr6 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr7_i386:
+    tls_context.Dr7 = reg_value.GetAsUInt32();
+    break;
+  }
+
+  return SetWoW64ThreadContextHelper(thread_handle, &tls_context);
+}
+
 Status
 NativeRegisterContextWindows_WoW64::ReadRegister(const RegisterInfo *reg_info,
                                                  RegisterValue &reg_value) {
   Status error;
   if (!reg_info) {
     error.SetErrorString("reg_info NULL");
     return error;
   }
 
   const uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
   if (reg == LLDB_INVALID_REGNUM) {
     // This is likely an internal register for lldb use only and should not be
     // directly queried.
     error.SetErrorStringWithFormat("register \"%s\" is an internal-only lldb "
                                    "register, cannot read directly",
                                    reg_info->name);
     return error;
   }
 
   if (IsGPR(reg))
     return GPRRead(reg, reg_value);
 
+  if (IsDR(reg))
+    return DRRead(reg, reg_value);
+
   return Status("unimplemented");
 }
 
 Status NativeRegisterContextWindows_WoW64::WriteRegister(
     const RegisterInfo *reg_info, const RegisterValue &reg_value) {
   Status error;
 
   if (!reg_info) {
error.SetErrorStringWithFormat("register \"%s\" is an internal-only lldb "
                                    "register, cannot write directly",
                                    reg_info->name);
     return error;
   }
 
   if (IsGPR(reg))
     return GPRWrite(reg, reg_value);
 
+  if (IsDR(reg))
+    return DRWrite(reg, reg_value);
+
   return Status("unimplemented");
 }
 
 Status NativeRegisterContextWindows_WoW64::ReadAllRegisterValues(
     lldb::DataBufferSP &data_sp) {
   const size_t data_size = REG_CONTEXT_SIZE;
   data_sp = std::make_shared<DataBufferHeap>(data_size, 0);
   ::WOW64_CONTEXT tls_context;
Status NativeRegisterContextWindows_WoW64::WriteAllRegisterValues(
 
   ::WOW64_CONTEXT tls_context;
   memcpy(&tls_context, data_sp->GetBytes(), data_size);
   return SetWoW64ThreadContextHelper(GetThreadHandle(), &tls_context);
 }
 
 Status NativeRegisterContextWindows_WoW64::IsWatchpointHit(uint32_t wp_index,
                                                            bool &is_hit) {
-  return Status("unimplemented");
+  is_hit = false;
+
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return Status("watchpoint index out of range");
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr6_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  is_hit = reg_value.GetAsUInt32() & (1 << wp_index);
+
+  return {};
 }
 
 Status NativeRegisterContextWindows_WoW64::GetWatchpointHitIndex(
     uint32_t &wp_index, lldb::addr_t trap_addr) {
-  return Status("unimplemented");
+  wp_index = LLDB_INVALID_INDEX32;
+
+  for (uint32_t i = 0; i < NumSupportedHardwareWatchpoints(); i++) {
+    bool is_hit;
+    Status error = IsWatchpointHit(i, is_hit);
+    if (error.Fail())
+      return error;
+
+    if (is_hit) {
+      wp_index = i;
+      return {};
+    }
+  }
+
+  return {};
 }
 
 Status NativeRegisterContextWindows_WoW64::IsWatchpointVacant(uint32_t wp_index,
                                                               bool &is_vacant) {
-  return Status("unimplemented");
-}
+  is_vacant = false;
 
-Status NativeRegisterContextWindows_WoW64::SetHardwareWatchpointWithIndex(
-    lldb::addr_t addr, size_t size, uint32_t watch_flags, uint32_t wp_index) {
-  return Status("unimplemented");
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return Status("Watchpoint index out of range");
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  is_vacant = !(reg_value.GetAsUInt32() & (1 << (2 * wp_index)));
+
+  return error;
 }
 
 bool NativeRegisterContextWindows_WoW64::ClearHardwareWatchpoint(
     uint32_t wp_index) {
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return false;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, clear bits 0, 1, 2, or 3 of
+  // the debug status register (DR6)
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr6_i386, reg_value);
+  if (error.Fail())
+    return false;
+
+  uint32_t bit_mask = 1 << wp_index;
+  uint32_t status_bits = reg_value.GetAsUInt32() & ~bit_mask;
+  error = DRWrite(lldb_dr6_i386, RegisterValue(status_bits));
+  if (error.Fail())
+    return false;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, clear bits {0-1,16-19},
+  // {2-3,20-23}, {4-5,24-27}, or {6-7,28-31} of the debug control register
+  // (DR7)
+
+  error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
     return false;
+
+  bit_mask = (0x3 << (2 * wp_index)) | (0xF << (16 + 4 * wp_index));
+  uint32_t control_bits = reg_value.GetAsUInt32() & ~bit_mask;
+  return DRWrite(lldb_dr7_i386, RegisterValue(control_bits)).Success();
 }
 
 Status NativeRegisterContextWindows_WoW64::ClearAllHardwareWatchpoints() {
-  return Status("unimplemented");
+  RegisterValue reg_value;
+
+  // clear bits {0-4} of the debug status register (DR6)
+
+  Status error = DRRead(lldb_dr6_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  uint32_t status_bits = reg_value.GetAsUInt32() & ~0xF;
+  error = DRWrite(lldb_dr6_i386, RegisterValue(status_bits));
+  if (error.Fail())
+    return error;
+
+  // clear bits {0-7,16-31} of the debug control register (DR7)
+
+  error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  uint32_t control_bits = reg_value.GetAsUInt32() & ~0xFFFF00FF;
+  return DRWrite(lldb_dr7_i386, RegisterValue(control_bits));
 }
 
 uint32_t NativeRegisterContextWindows_WoW64::SetHardwareWatchpoint(
     lldb::addr_t addr, size_t size, uint32_t watch_flags) {
+  switch (size) {
+  case 1:
+  case 2:
+  case 4:
+    break;
+  default:
     return LLDB_INVALID_INDEX32;
   }
 
+  if (watch_flags == 0x2)
+    watch_flags = 0x3;
+
+  if (watch_flags != 0x1 && watch_flags != 0x3)
+    return LLDB_INVALID_INDEX32;
+
+  for (uint32_t wp_index = 0; wp_index < NumSupportedHardwareWatchpoints();
+       ++wp_index) {
+    bool is_vacant;
+    if (IsWatchpointVacant(wp_index, is_vacant).Fail())
+      return LLDB_INVALID_INDEX32;
+
+    if (is_vacant) {
+      if (!ClearHardwareWatchpoint(wp_index))
+        return LLDB_INVALID_INDEX32;
+
+      if (ApplyHardwareBreakpoint(wp_index, addr, size, watch_flags).Fail())
+        return LLDB_INVALID_INDEX32;
+
+      return wp_index;
+    }
+  }
+  return LLDB_INVALID_INDEX32;
+}
+
+Status NativeRegisterContextWindows_WoW64::ApplyHardwareBreakpoint(
+    uint32_t wp_index, lldb::addr_t addr, size_t size, uint32_t flags) {
+  RegisterValue reg_value;
+  auto error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, set bits 1, 3, 5, or 7
+  uint32_t enable_bit = 1 << (2 * wp_index);
+
+  // set bits 16-17, 20-21, 24-25, or 28-29
+  // with 0b01 for write, and 0b11 for read/write
+  uint32_t rw_bits = flags << (16 + 4 * wp_index);
+
+  // set bits 18-19, 22-23, 26-27, or 30-31
+  // with 0b00, 0b01, 0b10, or 0b11
+  // for 1, 2, 8 (if supported), or 4 bytes, respectively
+  uint32_t size_bits = (size == 8 ? 0x2 : size - 1) << (18 + 4 * wp_index);
+
+  uint32_t bit_mask = (0x3 << (2 * wp_index)) | (0xF << (16 + 4 * wp_index));
+
+  uint32_t control_bits = reg_value.GetAsUInt32() & ~bit_mask;
+  control_bits |= enable_bit | rw_bits | size_bits;
+
+  error = DRWrite(lldb_dr7_i386, RegisterValue(control_bits));
+  if (error.Fail())
+    return error;
+
+  error = DRWrite(lldb_dr0_i386 + wp_index, RegisterValue(addr));
+  if (error.Fail())
+    return error;
+
+  return {};
+}
+
 lldb::addr_t
 NativeRegisterContextWindows_WoW64::GetWatchpointAddress(uint32_t wp_index) {
+  if (wp_index >= NumSupportedHardwareWatchpoints())
     return LLDB_INVALID_ADDRESS;
+
+  RegisterValue reg_value;
+  if (DRRead(lldb_dr0_i386 + wp_index, reg_value).Fail())
+    return LLDB_INVALID_ADDRESS;
+
+  return reg_value.GetAsUInt32();
 }
 
 uint32_t NativeRegisterContextWindows_WoW64::NumSupportedHardwareWatchpoints() {
-  // Not implemented
-  return 0;
+  return 4;
 }
 
 #endif // defined(__x86_64__) || defined(_M_X64)

lldb/source/Plugins/Process/Windows/Common/NativeRegisterContextWindows_i386.h

Status GetWatchpointHitIndex(uint32_t &wp_index,
                                lldb::addr_t trap_addr) override;
 
   Status IsWatchpointVacant(uint32_t wp_index, bool &is_vacant) override;
 
   bool ClearHardwareWatchpoint(uint32_t wp_index) override;
 
   Status ClearAllHardwareWatchpoints() override;
 
-  Status SetHardwareWatchpointWithIndex(lldb::addr_t addr, size_t size,
-                                        uint32_t watch_flags,
-                                        uint32_t wp_index);
-
   uint32_t SetHardwareWatchpoint(lldb::addr_t addr, size_t size,
                                  uint32_t watch_flags) override;
 
   lldb::addr_t GetWatchpointAddress(uint32_t wp_index) override;
 
   uint32_t NumSupportedHardwareWatchpoints() override;
 
 protected:
   Status GPRRead(const uint32_t reg, RegisterValue &reg_value);
   Status GPRWrite(const uint32_t reg, const RegisterValue &reg_value);
 
+  Status DRRead(const uint32_t reg, RegisterValue &reg_value);
+  Status DRWrite(const uint32_t reg, const RegisterValue &reg_value);
+
 private:
+  Status ApplyHardwareBreakpoint(uint32_t wp_index, lldb::addr_t addr,
+                                 size_t size, uint32_t flags);
+
   bool IsGPR(uint32_t reg_index) const;
+  bool IsDR(uint32_t reg_index) const;
 };
 
 } // namespace lldb_private
 
 #endif // liblldb_NativeRegisterContextWindows_i386_h_
 #endif // defined(__i386__) || defined(_M_IX86)

lldb/source/Plugins/Process/Windows/Common/NativeRegisterContextWindows_i386.cpp

static Status SetThreadContextHelper(lldb::thread_t thread_handle,
   }
   return Status();
 }
 
 std::unique_ptr<NativeRegisterContextWindows>
 NativeRegisterContextWindows::CreateHostNativeRegisterContextWindows(
     const ArchSpec &target_arch, NativeThreadProtocol &native_thread) {
   return std::make_unique<NativeRegisterContextWindows_i386>(target_arch,
-                                                              native_thread);
 }
 
 NativeRegisterContextWindows_i386::NativeRegisterContextWindows_i386(
     const ArchSpec &target_arch, NativeThreadProtocol &native_thread)
     : NativeRegisterContextWindows(native_thread,
                                    CreateRegisterInfoInterface(target_arch)) {}
 
 bool NativeRegisterContextWindows_i386::IsGPR(uint32_t reg_index) const {
   return (reg_index < k_first_alias_i386);
 }
 
+bool NativeRegisterContextWindows_i386::IsDR(uint32_t reg_index) const {
+  return (reg_index >= lldb_dr0_i386 && reg_index <= lldb_dr7_i386);
+}
+
 uint32_t NativeRegisterContextWindows_i386::GetRegisterSetCount() const {
   return k_num_register_sets;
 }
 
 const RegisterSet *
 NativeRegisterContextWindows_i386::GetRegisterSet(uint32_t set_index) const {
   if (set_index >= k_num_register_sets)
     return nullptr;
NativeRegisterContextWindows_i386::GPRWrite(const uint32_t reg,
   case lldb_es_i386:
     tls_context.SegEs = reg_value.GetAsUInt32();
     break;
   }
 
   return SetThreadContextHelper(thread_handle, &tls_context);
 }
 
+Status NativeRegisterContextWindows_i386::DRRead(const uint32_t reg,
+                                                 RegisterValue &reg_value) {
+  ::CONTEXT tls_context;
+  DWORD context_flag = CONTEXT_DEBUG_REGISTERS;
+  Status error =
+      GetThreadContextHelper(GetThreadHandle(), &tls_context, context_flag);
+  if (error.Fail())
+    return error;
+
+  switch (reg) {
+  case lldb_dr0_i386:
+    reg_value.SetUInt32(tls_context.Dr0);
+    break;
+  case lldb_dr1_i386:
+    reg_value.SetUInt32(tls_context.Dr1);
+    break;
+  case lldb_dr2_i386:
+    reg_value.SetUInt32(tls_context.Dr2);
+    break;
+  case lldb_dr3_i386:
+    reg_value.SetUInt32(tls_context.Dr3);
+    break;
+  case lldb_dr4_i386:
+    return Status("register DR4 is obsolete");
+  case lldb_dr5_i386:
+    return Status("register DR5 is obsolete");
+  case lldb_dr6_i386:
+    reg_value.SetUInt32(tls_context.Dr6);
+    break;
+  case lldb_dr7_i386:
+    reg_value.SetUInt32(tls_context.Dr7);
+    break;
+  }
+
+  return {};
+}
+
+Status
+NativeRegisterContextWindows_i386::DRWrite(const uint32_t reg,
+                                           const RegisterValue &reg_value) {
+  ::CONTEXT tls_context;
+  DWORD context_flag = CONTEXT_DEBUG_REGISTERS;
+  auto thread_handle = GetThreadHandle();
+  Status error =
+      GetThreadContextHelper(thread_handle, &tls_context, context_flag);
+  if (error.Fail())
+    return error;
+
+  switch (reg) {
+  case lldb_dr0_i386:
+    tls_context.Dr0 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr1_i386:
+    tls_context.Dr1 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr2_i386:
+    tls_context.Dr2 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr3_i386:
+    tls_context.Dr3 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr4_i386:
+    return Status("register DR4 is obsolete");
+  case lldb_dr5_i386:
+    return Status("register DR5 is obsolete");
+  case lldb_dr6_i386:
+    tls_context.Dr6 = reg_value.GetAsUInt32();
+    break;
+  case lldb_dr7_i386:
+    tls_context.Dr7 = reg_value.GetAsUInt32();
+    break;
+  }
+
+  return SetThreadContextHelper(thread_handle, &tls_context);
+}
+
 Status
 NativeRegisterContextWindows_i386::ReadRegister(const RegisterInfo *reg_info,
                                                 RegisterValue &reg_value) {
   Status error;
 
   if (!reg_info) {
     error.SetErrorString("reg_info NULL");
     return error;
   }
 
   const uint32_t reg = reg_info->kinds[lldb::eRegisterKindLLDB];
   if (reg == LLDB_INVALID_REGNUM) {
     // This is likely an internal register for lldb use only and should not be
     // directly queried.
     error.SetErrorStringWithFormat("register \"%s\" is an internal-only lldb "
                                    "register, cannot read directly",
                                    reg_info->name);
     return error;
   }
 
   if (IsGPR(reg))
     return GPRRead(reg, reg_value);
 
+  if (IsDR(reg))
+    return DRRead(reg, reg_value);
+
   return Status("unimplemented");
 }
 
 Status NativeRegisterContextWindows_i386::WriteRegister(
     const RegisterInfo *reg_info, const RegisterValue &reg_value) {
   Status error;
 
   if (!reg_info) {
error.SetErrorStringWithFormat("register \"%s\" is an internal-only lldb "
                                    "register, cannot write directly",
                                    reg_info->name);
     return error;
   }
 
   if (IsGPR(reg))
     return GPRWrite(reg, reg_value);
 
+  if (IsDR(reg))
+    return DRWrite(reg, reg_value);
+
   return Status("unimplemented");
 }
 
 Status NativeRegisterContextWindows_i386::ReadAllRegisterValues(
     lldb::DataBufferSP &data_sp) {
   const size_t data_size = REG_CONTEXT_SIZE;
   data_sp = std::make_shared<DataBufferHeap>(data_size, 0);
   ::CONTEXT tls_context;
Status NativeRegisterContextWindows_i386::WriteAllRegisterValues(
 
   ::CONTEXT tls_context;
   memcpy(&tls_context, data_sp->GetBytes(), data_size);
   return SetThreadContextHelper(GetThreadHandle(), &tls_context);
 }
 
 Status NativeRegisterContextWindows_i386::IsWatchpointHit(uint32_t wp_index,
                                                           bool &is_hit) {
-  return Status("unimplemented");
+  is_hit = false;
+
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return Status("watchpoint index out of range");
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr6_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  is_hit = reg_value.GetAsUInt32() & (1 << wp_index);
+
+  return {};
 }
 
 Status NativeRegisterContextWindows_i386::GetWatchpointHitIndex(
     uint32_t &wp_index, lldb::addr_t trap_addr) {
-  return Status("unimplemented");
+  wp_index = LLDB_INVALID_INDEX32;
+
+  for (uint32_t i = 0; i < NumSupportedHardwareWatchpoints(); i++) {
+    bool is_hit;
+    Status error = IsWatchpointHit(i, is_hit);
+    if (error.Fail())
+      return error;
+
+    if (is_hit) {
+      wp_index = i;
+      return {};
+    }
+  }
+
+  return {};
 }
 
 Status NativeRegisterContextWindows_i386::IsWatchpointVacant(uint32_t wp_index,
                                                              bool &is_vacant) {
-  return Status("unimplemented");
-}
+  is_vacant = false;
 
-Status NativeRegisterContextWindows_i386::SetHardwareWatchpointWithIndex(
-    lldb::addr_t addr, size_t size, uint32_t watch_flags, uint32_t wp_index) {
-  return Status("unimplemented");
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return Status("Watchpoint index out of range");
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  is_vacant = !(reg_value.GetAsUInt32() & (1 << (2 * wp_index)));
+
+  return error;
 }
 
 bool NativeRegisterContextWindows_i386::ClearHardwareWatchpoint(
     uint32_t wp_index) {
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return false;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, clear bits 0, 1, 2, or 3 of
+  // the debug status register (DR6)
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr6_i386, reg_value);
+  if (error.Fail())
+    return false;
+
+  uint32_t bit_mask = 1 << wp_index;
+  uint32_t status_bits = reg_value.GetAsUInt32() & ~bit_mask;
+  error = DRWrite(lldb_dr6_i386, RegisterValue(status_bits));
+  if (error.Fail())
+    return false;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, clear bits {0-1,16-19},
+  // {2-3,20-23}, {4-5,24-27}, or {6-7,28-31} of the debug control register
+  // (DR7)
+
+  error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
     return false;
+
+  bit_mask = (0x3 << (2 * wp_index)) | (0xF << (16 + 4 * wp_index));
+  uint32_t control_bits = reg_value.GetAsUInt32() & ~bit_mask;
+  return DRWrite(lldb_dr7_i386, RegisterValue(control_bits)).Success();
 }
 
 Status NativeRegisterContextWindows_i386::ClearAllHardwareWatchpoints() {
-  return Status("unimplemented");
+  RegisterValue reg_value;
+
+  // clear bits {0-4} of the debug status register (DR6)
+
+  Status error = DRRead(lldb_dr6_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  uint32_t status_bits = reg_value.GetAsUInt32() & ~0xF;
+  error = DRWrite(lldb_dr6_i386, RegisterValue(status_bits));
+  if (error.Fail())
+    return error;
+
+  // clear bits {0-7,16-31} of the debug control register (DR7)
+
+  error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  uint32_t control_bits = reg_value.GetAsUInt32() & ~0xFFFF00FF;
+  return DRWrite(lldb_dr7_i386, RegisterValue(control_bits));
 }
 
 uint32_t NativeRegisterContextWindows_i386::SetHardwareWatchpoint(
     lldb::addr_t addr, size_t size, uint32_t watch_flags) {
+  switch (size) {
+  case 1:
+  case 2:
+  case 4:
+    break;
+  default:
+    return LLDB_INVALID_INDEX32;
+  }
+
+  if (watch_flags == 0x2)
+    watch_flags = 0x3;
+
+  if (watch_flags != 0x1 && watch_flags != 0x3)
+    return LLDB_INVALID_INDEX32;
+
+  for (uint32_t wp_index = 0; wp_index < NumSupportedHardwareWatchpoints();
+       ++wp_index) {
+    bool is_vacant;
+    if (IsWatchpointVacant(wp_index, is_vacant).Fail())
+      return LLDB_INVALID_INDEX32;
+
+    if (is_vacant) {
+      if (!ClearHardwareWatchpoint(wp_index))
+        return LLDB_INVALID_INDEX32;
+
+      if (ApplyHardwareBreakpoint(wp_index, addr, size, watch_flags).Fail())
+        return LLDB_INVALID_INDEX32;
+
+      return wp_index;
+    }
+  }
   return LLDB_INVALID_INDEX32;
 }
 
+Status NativeRegisterContextWindows_i386::ApplyHardwareBreakpoint(
+    uint32_t wp_index, lldb::addr_t addr, size_t size, uint32_t flags) {
+  RegisterValue reg_value;
+  auto error = DRRead(lldb_dr7_i386, reg_value);
+  if (error.Fail())
+    return error;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, set bits 1, 3, 5, or 7
+  uint32_t enable_bit = 1 << (2 * wp_index);
+
+  // set bits 16-17, 20-21, 24-25, or 28-29
+  // with 0b01 for write, and 0b11 for read/write
+  uint32_t rw_bits = flags << (16 + 4 * wp_index);
+
+  // set bits 18-19, 22-23, 26-27, or 30-31
+  // with 0b00, 0b01, 0b10, or 0b11
+  // for 1, 2, 8 (if supported), or 4 bytes, respectively
+  uint32_t size_bits = (size == 8 ? 0x2 : size - 1) << (18 + 4 * wp_index);
+
+  uint32_t bit_mask = (0x3 << (2 * wp_index)) | (0xF << (16 + 4 * wp_index));
+
+  uint32_t control_bits = reg_value.GetAsUInt32() & ~bit_mask;
+  control_bits |= enable_bit | rw_bits | size_bits;
+
+  error = DRWrite(lldb_dr7_i386, RegisterValue(control_bits));
+  if (error.Fail())
+    return error;
+
+  error = DRWrite(lldb_dr0_i386 + wp_index, RegisterValue(addr));
+  if (error.Fail())
+    return error;
+
+  return {};
+}
+
 lldb::addr_t
 NativeRegisterContextWindows_i386::GetWatchpointAddress(uint32_t wp_index) {
+  if (wp_index >= NumSupportedHardwareWatchpoints())
     return LLDB_INVALID_ADDRESS;
+
+  RegisterValue reg_value;
+  if (DRRead(lldb_dr0_i386 + wp_index, reg_value).Fail())
+    return LLDB_INVALID_ADDRESS;
+
+  return reg_value.GetAsUInt32();
 }
 
 uint32_t NativeRegisterContextWindows_i386::NumSupportedHardwareWatchpoints() {
-  // Not implemented
-  return 0;
+  return 4;
 }
 
 #endif

lldb/source/Plugins/Process/Windows/Common/NativeRegisterContextWindows_x86_64.h

Status GetWatchpointHitIndex(uint32_t &wp_index,
                                lldb::addr_t trap_addr) override;
 
   Status IsWatchpointVacant(uint32_t wp_index, bool &is_vacant) override;
 
   bool ClearHardwareWatchpoint(uint32_t wp_index) override;
 
   Status ClearAllHardwareWatchpoints() override;
 
-  Status SetHardwareWatchpointWithIndex(lldb::addr_t addr, size_t size,
-                                        uint32_t watch_flags,
-                                        uint32_t wp_index);
-
   uint32_t SetHardwareWatchpoint(lldb::addr_t addr, size_t size,
                                  uint32_t watch_flags) override;
 
   lldb::addr_t GetWatchpointAddress(uint32_t wp_index) override;
 
   uint32_t NumSupportedHardwareWatchpoints() override;
 
 protected:
   Status GPRRead(const uint32_t reg, RegisterValue &reg_value);
-
   Status GPRWrite(const uint32_t reg, const RegisterValue &reg_value);
 
   Status FPRRead(const uint32_t reg, RegisterValue &reg_value);
-
   Status FPRWrite(const uint32_t reg, const RegisterValue &reg_value);
 
+  Status DRRead(const uint32_t reg, RegisterValue &reg_value);
+  Status DRWrite(const uint32_t reg, const RegisterValue &reg_value);
+
 private:
-  bool IsGPR(uint32_t reg_index) const;
+  Status ApplyHardwareBreakpoint(uint32_t wp_index, lldb::addr_t addr,
+                                 size_t size, uint32_t flags);
 
+  bool IsGPR(uint32_t reg_index) const;
   bool IsFPR(uint32_t reg_index) const;
+  bool IsDR(uint32_t reg_index) const;
 };
 
 } // namespace lldb_private
 
 #endif // liblldb_NativeRegisterContextWindows_x86_64_h_
 #endif // defined(__x86_64__) || defined(_M_X64)

lldb/source/Plugins/Process/Windows/Common/NativeRegisterContextWindows_x86_64.cpp

 }
 
 std::unique_ptr<NativeRegisterContextWindows>
 NativeRegisterContextWindows::CreateHostNativeRegisterContextWindows(
     const ArchSpec &target_arch, NativeThreadProtocol &native_thread) {
   // Register context for a WoW64 application.
   if (target_arch.GetAddressByteSize() == 4)
     return std::make_unique<NativeRegisterContextWindows_WoW64>(target_arch,
-                                                                 native_thread);
 
   // Register context for a native 64-bit application.
   return std::make_unique<NativeRegisterContextWindows_x86_64>(target_arch,
-                                                                native_thread);
 }
 
 NativeRegisterContextWindows_x86_64::NativeRegisterContextWindows_x86_64(
     const ArchSpec &target_arch, NativeThreadProtocol &native_thread)
     : NativeRegisterContextWindows(native_thread,
                                    CreateRegisterInfoInterface(target_arch)) {}
 
 bool NativeRegisterContextWindows_x86_64::IsGPR(uint32_t reg_index) const {
   return (reg_index >= k_first_gpr_x86_64 && reg_index < k_first_alias_x86_64);
 }
 
 bool NativeRegisterContextWindows_x86_64::IsFPR(uint32_t reg_index) const {
   return (reg_index >= lldb_xmm0_x86_64 && reg_index <= k_last_fpr_x86_64);
 }
 
+bool NativeRegisterContextWindows_x86_64::IsDR(uint32_t reg_index) const {
+  return (reg_index >= lldb_dr0_x86_64 && reg_index <= lldb_dr7_x86_64);
+}
+
 uint32_t NativeRegisterContextWindows_x86_64::GetRegisterSetCount() const {
   return k_num_register_sets;
 }
 
 const RegisterSet *
 NativeRegisterContextWindows_x86_64::GetRegisterSet(uint32_t set_index) const {
   if (set_index >= k_num_register_sets)
     return nullptr;
NativeRegisterContextWindows_x86_64::FPRWrite(const uint32_t reg,
   case lldb_xmm15_x86_64:
     memcpy(&tls_context.Xmm15, reg_value.GetBytes(), 16);
     break;
   }
 
   return SetThreadContextHelper(thread_handle, &tls_context);
 }
 
+Status NativeRegisterContextWindows_x86_64::DRRead(const uint32_t reg,
+                                                   RegisterValue &reg_value) {
+  ::CONTEXT tls_context;
+  DWORD context_flag = CONTEXT_DEBUG_REGISTERS;
+  Status error =
+      GetThreadContextHelper(GetThreadHandle(), &tls_context, context_flag);
+  if (error.Fail())
+    return error;
+
+  switch (reg) {
+  case lldb_dr0_x86_64:
+    reg_value.SetUInt64(tls_context.Dr0);
+    break;
+  case lldb_dr1_x86_64:
+    reg_value.SetUInt64(tls_context.Dr1);
+    break;
+  case lldb_dr2_x86_64:
+    reg_value.SetUInt64(tls_context.Dr2);
+    break;
+  case lldb_dr3_x86_64:
+    reg_value.SetUInt64(tls_context.Dr3);
+    break;
+  case lldb_dr4_x86_64:
+    return Status("register DR4 is obsolete");
+  case lldb_dr5_x86_64:
+    return Status("register DR5 is obsolete");
+  case lldb_dr6_x86_64:
+    reg_value.SetUInt64(tls_context.Dr6);
+    break;
+  case lldb_dr7_x86_64:
+    reg_value.SetUInt64(tls_context.Dr7);
+    break;
+  }
+
+  return {};
+}
+
+Status
+NativeRegisterContextWindows_x86_64::DRWrite(const uint32_t reg,
+                                             const RegisterValue &reg_value) {
+  ::CONTEXT tls_context;
+  DWORD context_flag = CONTEXT_DEBUG_REGISTERS;
+  auto thread_handle = GetThreadHandle();
+  Status error =
+      GetThreadContextHelper(thread_handle, &tls_context, context_flag);
+  if (error.Fail())
+    return error;
+
+  switch (reg) {
+  case lldb_dr0_x86_64:
+    tls_context.Dr0 = reg_value.GetAsUInt64();
+    break;
+  case lldb_dr1_x86_64:
+    tls_context.Dr1 = reg_value.GetAsUInt64();
+    break;
+  case lldb_dr2_x86_64:
+    tls_context.Dr2 = reg_value.GetAsUInt64();
+    break;
+  case lldb_dr3_x86_64:
+    tls_context.Dr3 = reg_value.GetAsUInt64();
+    break;
+  case lldb_dr4_x86_64:
+    return Status("register DR4 is obsolete");
+  case lldb_dr5_x86_64:
+    return Status("register DR5 is obsolete");
+  case lldb_dr6_x86_64:
+    tls_context.Dr6 = reg_value.GetAsUInt64();
+    break;
+  case lldb_dr7_x86_64:
+    tls_context.Dr7 = reg_value.GetAsUInt64();
+    break;
+  }
+
+  return SetThreadContextHelper(thread_handle, &tls_context);
+}
+
 Status
 NativeRegisterContextWindows_x86_64::ReadRegister(const RegisterInfo *reg_info,
                                                   RegisterValue &reg_value) {
   Status error;
   if (!reg_info) {
     error.SetErrorString("reg_info NULL");
     return error;
   }
NativeRegisterContextWindows_x86_64::ReadRegister(const RegisterInfo *reg_info,
   }
 
   if (IsGPR(reg))
     return GPRRead(reg, reg_value);
 
   if (IsFPR(reg))
     return FPRRead(reg, reg_value);
 
+  if (IsDR(reg))
+    return DRRead(reg, reg_value);
+
   return Status("unimplemented");
 }
 
 Status NativeRegisterContextWindows_x86_64::WriteRegister(
     const RegisterInfo *reg_info, const RegisterValue &reg_value) {
   Status error;
 
   if (!reg_info) {
Status NativeRegisterContextWindows_x86_64::WriteRegister(
   }
 
   if (IsGPR(reg))
     return GPRWrite(reg, reg_value);
 
   if (IsFPR(reg))
     return FPRWrite(reg, reg_value);
 
+  if (IsDR(reg))
+    return DRWrite(reg, reg_value);
+
   return Status("unimplemented");
 }
 
 Status NativeRegisterContextWindows_x86_64::ReadAllRegisterValues(
     lldb::DataBufferSP &data_sp) {
   const size_t data_size = REG_CONTEXT_SIZE;
   data_sp = std::make_shared<DataBufferHeap>(data_size, 0);
   ::CONTEXT tls_context;
Status NativeRegisterContextWindows_x86_64::WriteAllRegisterValues(
 
   ::CONTEXT tls_context;
   memcpy(&tls_context, data_sp->GetBytes(), data_size);
   return SetThreadContextHelper(GetThreadHandle(), &tls_context);
 }
 
 Status NativeRegisterContextWindows_x86_64::IsWatchpointHit(uint32_t wp_index,
                                                             bool &is_hit) {
-  return Status("unimplemented");
+  is_hit = false;
+
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return Status("watchpoint index out of range");
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr6_x86_64, reg_value);
+  if (error.Fail())
+    return error;
+
+  is_hit = reg_value.GetAsUInt64() & (1ULL << wp_index);
+
+  return {};
 }
 
 Status NativeRegisterContextWindows_x86_64::GetWatchpointHitIndex(
     uint32_t &wp_index, lldb::addr_t trap_addr) {
-  return Status("unimplemented");
+  wp_index = LLDB_INVALID_INDEX32;
+
+  for (uint32_t i = 0; i < NumSupportedHardwareWatchpoints(); i++) {
+    bool is_hit;
+    Status error = IsWatchpointHit(i, is_hit);
+    if (error.Fail())
+      return error;
+
+    if (is_hit) {
+      wp_index = i;
+      return {};
+    }
+  }
+
+  return {};
 }
 
 Status
 NativeRegisterContextWindows_x86_64::IsWatchpointVacant(uint32_t wp_index,
                                                         bool &is_vacant) {
-  return Status("unimplemented");
-}
+  is_vacant = false;
 
-Status NativeRegisterContextWindows_x86_64::SetHardwareWatchpointWithIndex(
-    lldb::addr_t addr, size_t size, uint32_t watch_flags, uint32_t wp_index) {
-  return Status("unimplemented");
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return Status("Watchpoint index out of range");
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr7_x86_64, reg_value);
+  if (error.Fail())
+    return error;
+
+  is_vacant = !(reg_value.GetAsUInt64() & (1ULL << (2 * wp_index)));
+
+  return error;
 }
 
 bool NativeRegisterContextWindows_x86_64::ClearHardwareWatchpoint(
     uint32_t wp_index) {
+  if (wp_index >= NumSupportedHardwareWatchpoints())
+    return false;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, clear bits 0, 1, 2, or 3 of
+  // the debug status register (DR6)
+
+  RegisterValue reg_value;
+  Status error = DRRead(lldb_dr6_x86_64, reg_value);
+  if (error.Fail())
+    return false;
+
+  uint64_t bit_mask = 1ULL << wp_index;
+  uint64_t status_bits = reg_value.GetAsUInt64() & ~bit_mask;
+  error = DRWrite(lldb_dr6_x86_64, RegisterValue(status_bits));
+  if (error.Fail())
+    return false;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, clear bits {0-1,16-19},
+  // {2-3,20-23}, {4-5,24-27}, or {6-7,28-31} of the debug control register
+  // (DR7)
+
+  error = DRRead(lldb_dr7_x86_64, reg_value);
+  if (error.Fail())
     return false;
+
+  bit_mask = (0x3 << (2 * wp_index)) | (0xF << (16 + 4 * wp_index));
+  uint64_t control_bits = reg_value.GetAsUInt64() & ~bit_mask;
+  return DRWrite(lldb_dr7_x86_64, RegisterValue(control_bits)).Success();
 }
 
 Status NativeRegisterContextWindows_x86_64::ClearAllHardwareWatchpoints() {
-  return Status("unimplemented");
+  RegisterValue reg_value;
+
+  // clear bits {0-4} of the debug status register (DR6)
+
+  Status error = DRRead(lldb_dr6_x86_64, reg_value);
+  if (error.Fail())
+    return error;
+
+  uint64_t status_bits = reg_value.GetAsUInt64() & ~0xFULL;
+  error = DRWrite(lldb_dr6_x86_64, RegisterValue(status_bits));
+  if (error.Fail())
+    return error;
+
+  // clear bits {0-7,16-31} of the debug control register (DR7)
+
+  error = DRRead(lldb_dr7_x86_64, reg_value);
+  if (error.Fail())
+    return error;
+
+  uint64_t control_bits = reg_value.GetAsUInt64() & ~0xFFFF00FFULL;
+  return DRWrite(lldb_dr7_x86_64, RegisterValue(control_bits));
 }
 
 uint32_t NativeRegisterContextWindows_x86_64::SetHardwareWatchpoint(
     lldb::addr_t addr, size_t size, uint32_t watch_flags) {
+  switch (size) {
+  case 1:
+  case 2:
+  case 4:
+  case 8:
+    break;
+  default:
+    return LLDB_INVALID_INDEX32;
+  }
+
+  if (watch_flags == 0x2)
+    watch_flags = 0x3;
+
+  if (watch_flags != 0x1 && watch_flags != 0x3)
+    return LLDB_INVALID_INDEX32;
+
+  for (uint32_t wp_index = 0; wp_index < NumSupportedHardwareWatchpoints();
+       ++wp_index) {
+    bool is_vacant;
+    if (IsWatchpointVacant(wp_index, is_vacant).Fail())
+      return LLDB_INVALID_INDEX32;
+
+    if (is_vacant) {
+      if (!ClearHardwareWatchpoint(wp_index))
+        return LLDB_INVALID_INDEX32;
+
+      if (ApplyHardwareBreakpoint(wp_index, addr, size, watch_flags).Fail())
+        return LLDB_INVALID_INDEX32;
+
+      return wp_index;
+    }
+  }
   return LLDB_INVALID_INDEX32;
 }
 
+Status NativeRegisterContextWindows_x86_64::ApplyHardwareBreakpoint(
+    uint32_t wp_index, lldb::addr_t addr, size_t size, uint32_t flags) {
+  RegisterValue reg_value;
+  auto error = DRRead(lldb_dr7_x86_64, reg_value);
+  if (error.Fail())
+    return error;
+
+  // for watchpoints 0, 1, 2, or 3, respectively, set bits 1, 3, 5, or 7
+  uint64_t enable_bit = 1ULL << (2 * wp_index);
+
+  // set bits 16-17, 20-21, 24-25, or 28-29
+  // with 0b01 for write, and 0b11 for read/write
+  uint64_t rw_bits = flags << (16 + 4 * wp_index);
+
+  // set bits 18-19, 22-23, 26-27, or 30-31
+  // with 0b00, 0b01, 0b10, or 0b11
+  // for 1, 2, 8 (if supported), or 4 bytes, respectively
+  uint64_t size_bits = (size == 8 ? 0x2 : size - 1) << (18 + 4 * wp_index);
+
+  uint64_t bit_mask = (0x3 << (2 * wp_index)) | (0xF << (16 + 4 * wp_index));
+
+  uint64_t control_bits = reg_value.GetAsUInt64() & ~bit_mask;
+  control_bits |= enable_bit | rw_bits | size_bits;
+
+  error = DRWrite(lldb_dr7_x86_64, RegisterValue(control_bits));
+  if (error.Fail())
+    return error;
+
+  error = DRWrite(lldb_dr0_x86_64 + wp_index, RegisterValue(addr));
+  if (error.Fail())
+    return error;
+
+  return {};
+}
+
 lldb::addr_t
 NativeRegisterContextWindows_x86_64::GetWatchpointAddress(uint32_t wp_index) {
+  if (wp_index >= NumSupportedHardwareWatchpoints())
     return LLDB_INVALID_ADDRESS;
+
+  RegisterValue reg_value;
+  if (DRRead(lldb_dr0_x86_64 + wp_index, reg_value).Fail())
+    return LLDB_INVALID_ADDRESS;
+
+  return reg_value.GetAsUInt64();
 }
 
 uint32_t
 NativeRegisterContextWindows_x86_64::NumSupportedHardwareWatchpoints() {
-  // Not implemented
-  return 0;
+  return 4;
 }
 
 #endif // defined(__x86_64__) || defined(_M_X64)

lldb/source/Plugins/Process/Windows/Common/NativeThreadWindows.cpp

case eStateDetached:
     }
     return false;
   }
   llvm_unreachable("unhandled StateType!");
 }
 
 Status NativeThreadWindows::SetWatchpoint(lldb::addr_t addr, size_t size,
                                           uint32_t watch_flags, bool hardware) {
-  return Status("unimplemented.");
+  if (!hardware)
+    return Status("not implemented");
+  if (m_state == eStateLaunching)
+    return Status();
+  Status error = RemoveWatchpoint(addr);
+  if (error.Fail())
+    return error;
+  uint32_t wp_index =
+      m_reg_context_up->SetHardwareWatchpoint(addr, size, watch_flags);
+  if (wp_index == LLDB_INVALID_INDEX32)
+    return Status("Setting hardware watchpoint failed.");
+  m_watchpoint_index_map.insert({addr, wp_index});
+  return Status();
 }
 
 Status NativeThreadWindows::RemoveWatchpoint(lldb::addr_t addr) {
-  return Status("unimplemented");
+  auto wp = m_watchpoint_index_map.find(addr);
+  if (wp == m_watchpoint_index_map.end())
+    return Status();
+  uint32_t wp_index = wp->second;
+  m_watchpoint_index_map.erase(wp);
+  if (m_reg_context_up->ClearHardwareWatchpoint(wp_index))
+    return Status();
+  return Status("Clearing hardware watchpoint failed.");
 }
 
 Status NativeThreadWindows::SetHardwareBreakpoint(lldb::addr_t addr,
                                                   size_t size) {
   return Status("unimplemented.");
 }
 
 Status NativeThreadWindows::RemoveHardwareBreakpoint(lldb::addr_t addr) {
   return Status("unimplemented.");
 }