[lldb] [Process/NetBSD] Copy watchpoints to newly-created threads

NetBSD ptrace interface does not populate watchpoints to newly-created
threads.  Solve this via copying the watchpoints from the current thread
when new thread is reported via TRAP_LWP.

Add a test that verifies that when the user does not have permissions
to set watchpoints on NetBSD, the 'watchpoint set' errors out gracefully
and thread monitoring does not crash on being unable to copy watchpoints
to new threads.

Differential Revision: https://reviews.llvm.org/D70023

7 files changed, 54 insertions, 8 deletions

diff --git a/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp b/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
index 0b21c7862b0..372ac059cb5 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
+++ b/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
@@ -272,12 +272,21 @@ void NativeProcessNetBSD::MonitorSIGTRAP(lldb::pid_t pid) {
     }
 
     switch (pst.pe_report_event) {
-      case PTRACE_LWP_CREATE:
+      case PTRACE_LWP_CREATE: {
         LLDB_LOG(log,
                  "monitoring new thread, pid = {0}, LWP = {1}", pid,
                  pst.pe_lwp);
-        AddThread(pst.pe_lwp);
-        break;
+        NativeThreadNetBSD& t = AddThread(pst.pe_lwp);
+        error = t.CopyWatchpointsFrom(
+            static_cast<NativeThreadNetBSD &>(*GetCurrentThread()));
+        if (error.Fail()) {
+          LLDB_LOG(log,
+                   "failed to copy watchpoints to new thread {0}: {1}",
+                   pst.pe_lwp, error);
+          SetState(StateType::eStateInvalid);
+          return;
+        }
+      } break;
       case PTRACE_LWP_EXIT:
         LLDB_LOG(log,
                  "removing exited thread, pid = {0}, LWP = {1}", pid,
diff --git a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.cpp b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.cpp
index 3a9caaad74c..a8afa0b2030 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.cpp
+++ b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.cpp
@@ -8,6 +8,8 @@
 
 #include "NativeRegisterContextNetBSD.h"
 
+#include "Plugins/Process/NetBSD/NativeProcessNetBSD.h"
+
 #include "lldb/Host/common/NativeProcessProtocol.h"
 
 using namespace lldb_private;
diff --git a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.h b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.h
index f5dd0c33b67..2947454af2d 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.h
+++ b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD.h
@@ -11,12 +11,13 @@
 
 #include "lldb/Host/common/NativeThreadProtocol.h"
 
-#include "Plugins/Process/NetBSD/NativeProcessNetBSD.h"
 #include "Plugins/Process/Utility/NativeRegisterContextRegisterInfo.h"
 
 namespace lldb_private {
 namespace process_netbsd {
 
+class NativeProcessNetBSD;
+
 class NativeRegisterContextNetBSD : public NativeRegisterContextRegisterInfo {
 public:
   NativeRegisterContextNetBSD(NativeThreadProtocol &native_thread,
@@ -30,6 +31,8 @@ public:
   static NativeRegisterContextNetBSD *
   CreateHostNativeRegisterContextNetBSD(const ArchSpec &target_arch,
                                         NativeThreadProtocol &native_thread);
+  virtual Status
+  CopyHardwareWatchpointsFrom(NativeRegisterContextNetBSD &source) = 0;
 
 protected:
   Status DoRegisterSet(int req, void *buf);
diff --git a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp
index 35ebbedf26a..afb62b8170e 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp
+++ b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.cpp
@@ -988,4 +988,19 @@ uint32_t NativeRegisterContextNetBSD_x86_64::NumSupportedHardwareWatchpoints() {
   return 4;
 }
 
+Status NativeRegisterContextNetBSD_x86_64::CopyHardwareWatchpointsFrom(
+    NativeRegisterContextNetBSD &source) {
+  auto &r_source = static_cast<NativeRegisterContextNetBSD_x86_64&>(source);
+  Status res = r_source.ReadRegisterSet(DBRegSet);
+  if (!res.Fail()) {
+    // copy dbregs only if any watchpoints were set
+    if ((r_source.m_dbr_x86_64.dr[7] & 0xFF) == 0)
+      return res;
+
+    m_dbr_x86_64 = r_source.m_dbr_x86_64;
+    res = WriteRegisterSet(DBRegSet);
+  }
+  return res;
+}
+
 #endif // defined(__x86_64__)
diff --git a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.h b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.h
index 4ef8989ae93..0da0351a7b0 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.h
+++ b/lldb/source/Plugins/Process/NetBSD/NativeRegisterContextNetBSD_x86_64.h
@@ -71,6 +71,9 @@ public:
 
   uint32_t NumSupportedHardwareWatchpoints() override;
 
+  Status
+  CopyHardwareWatchpointsFrom(NativeRegisterContextNetBSD &source) override;
+
 private:
   // Private member types.
   enum { GPRegSet, FPRegSet, XStateRegSet, DBRegSet };
diff --git a/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.cpp b/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.cpp
index c3251c88a42..3dd14f0e1f6 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.cpp
+++ b/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.cpp
@@ -221,9 +221,9 @@ bool NativeThreadNetBSD::GetStopReason(ThreadStopInfo &stop_info,
   llvm_unreachable("unhandled StateType!");
 }
 
-NativeRegisterContext& NativeThreadNetBSD::GetRegisterContext() {
+NativeRegisterContextNetBSD &NativeThreadNetBSD::GetRegisterContext() {
   assert(m_reg_context_up);
-return  *m_reg_context_up;
+  return *m_reg_context_up;
 }
 
 Status NativeThreadNetBSD::SetWatchpoint(lldb::addr_t addr, size_t size,
@@ -284,3 +284,13 @@ Status NativeThreadNetBSD::RemoveHardwareBreakpoint(lldb::addr_t addr) {
 
   return Status("Clearing hardware breakpoint failed.");
 }
+
+Status NativeThreadNetBSD::CopyWatchpointsFrom(NativeThreadNetBSD &source) {
+  Status s = GetRegisterContext().CopyHardwareWatchpointsFrom(
+      source.GetRegisterContext());
+  if (!s.Fail()) {
+    m_watchpoint_index_map = source.m_watchpoint_index_map;
+    m_hw_break_index_map = source.m_hw_break_index_map;
+  }
+  return s;
+}
diff --git a/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.h b/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.h
index f944b50efe0..89b61ef8672 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.h
+++ b/lldb/source/Plugins/Process/NetBSD/NativeThreadNetBSD.h
@@ -11,6 +11,8 @@
 
 #include "lldb/Host/common/NativeThreadProtocol.h"
 
+#include "Plugins/Process/NetBSD/NativeRegisterContextNetBSD.h"
+
 #include <csignal>
 #include <map>
 #include <string>
@@ -34,7 +36,7 @@ public:
   bool GetStopReason(ThreadStopInfo &stop_info,
                      std::string &description) override;
 
-  NativeRegisterContext& GetRegisterContext() override;
+  NativeRegisterContextNetBSD &GetRegisterContext() override;
 
   Status SetWatchpoint(lldb::addr_t addr, size_t size, uint32_t watch_flags,
                        bool hardware) override;
@@ -62,10 +64,12 @@ private:
   void SetRunning();
   void SetStepping();
 
+  Status CopyWatchpointsFrom(NativeThreadNetBSD& source);
+
   // Member Variables
   lldb::StateType m_state;
   ThreadStopInfo m_stop_info;
-  std::unique_ptr<NativeRegisterContext> m_reg_context_up;
+  std::unique_ptr<NativeRegisterContextNetBSD> m_reg_context_up;
   std::string m_stop_description;
   using WatchpointIndexMap = std::map<lldb::addr_t, uint32_t>;
   WatchpointIndexMap m_watchpoint_index_map;