[lldb] [llgs server] Support creating core dumps on NetBSD

Add a new SaveCore() process method that can be used to request a core
dump.  This is currently implemented on NetBSD via the PT_DUMPCORE
ptrace(2) request, and enabled via 'savecore' extension.

Protocol-wise, a new qSaveCore packet is introduced.  It accepts zero
or more semicolon-separated key:value options, invokes the core dump
and returns a key:value response.  Currently the only option supported
is "path-hint", and the return value contains the "path" actually used.
The support for the feature is exposed via qSaveCore qSupported feature.

Differential Revision: https://reviews.llvm.org/D101285

5 files changed, 73 insertions, 1 deletions

diff --git a/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp b/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
index 9ea1a16..0420d00 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
+++ b/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
@@ -136,7 +136,8 @@ NativeProcessNetBSD::Factory::Attach(
 NativeProcessNetBSD::Extension
 NativeProcessNetBSD::Factory::GetSupportedExtensions() const {
   return Extension::multiprocess | Extension::fork | Extension::vfork |
-         Extension::pass_signals | Extension::auxv | Extension::libraries_svr4;
+         Extension::pass_signals | Extension::auxv | Extension::libraries_svr4 |
+         Extension::savecore;
 }
 
 // Public Instance Methods
@@ -1073,3 +1074,27 @@ void NativeProcessNetBSD::MonitorClone(::pid_t child_pid, bool is_vfork,
     }
   }
 }
+
+llvm::Expected<std::string>
+NativeProcessNetBSD::SaveCore(llvm::StringRef path_hint) {
+  llvm::SmallString<128> path{path_hint};
+  Status error;
+
+  // Try with the suggested path first.
+  if (!path.empty()) {
+    error = PtraceWrapper(PT_DUMPCORE, GetID(), path.data(), path.size());
+    if (!error.Fail())
+      return path.str().str();
+
+    // If the request errored, fall back to a generic temporary file.
+  }
+
+  if (std::error_code errc =
+          llvm::sys::fs::createTemporaryFile("lldb", "core", path))
+    return llvm::createStringError(errc, "Unable to create a temporary file");
+
+  error = PtraceWrapper(PT_DUMPCORE, GetID(), path.data(), path.size());
+  if (error.Fail())
+    return error.ToError();
+  return path.str().str();
+}
diff --git a/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.h b/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.h
index 90d32aa..3f54d02 100644
--- a/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.h
+++ b/lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.h
@@ -88,6 +88,8 @@ public:
   static Status PtraceWrapper(int req, lldb::pid_t pid, void *addr = nullptr,
                               int data = 0, int *result = nullptr);
 
+  llvm::Expected<std::string> SaveCore(llvm::StringRef path_hint) override;
+
 private:
   MainLoop::SignalHandleUP m_sigchld_handle;
   ArchSpec m_arch;
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
index 8e1f6bc..5d0ce3a 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp
@@ -226,6 +226,10 @@ void GDBRemoteCommunicationServerLLGS::RegisterPacketHandlers() {
                           quit = true;
                           return this->Handle_k(packet);
                         });
+
+  RegisterMemberFunctionHandler(
+      StringExtractorGDBRemote::eServerPacketType_qLLDBSaveCore,
+      &GDBRemoteCommunicationServerLLGS::Handle_qSaveCore);
 }
 
 void GDBRemoteCommunicationServerLLGS::SetLaunchInfo(const ProcessLaunchInfo &info) {
@@ -3604,6 +3608,41 @@ GDBRemoteCommunicationServerLLGS::Handle_QMemTags(
   return status.Success() ? SendOKResponse() : SendErrorResponse(1);
 }
 
+GDBRemoteCommunication::PacketResult
+GDBRemoteCommunicationServerLLGS::Handle_qSaveCore(
+    StringExtractorGDBRemote &packet) {
+  // Fail if we don't have a current process.
+  if (!m_current_process ||
+      (m_current_process->GetID() == LLDB_INVALID_PROCESS_ID))
+    return SendErrorResponse(Status("Process not running."));
+
+  std::string path_hint;
+
+  StringRef packet_str{packet.GetStringRef()};
+  bool cf = packet_str.consume_front("qSaveCore");
+  assert(cf);
+  if (packet_str.consume_front(";")) {
+    llvm::SmallVector<llvm::StringRef, 2> fields;
+    packet_str.split(fields, ';');
+
+    for (auto x : fields) {
+      if (x.consume_front("path-hint:"))
+        StringExtractor(x).GetHexByteString(path_hint);
+      else
+        return SendErrorResponse(Status("Unsupported qSaveCore option"));
+    }
+  }
+
+  llvm::Expected<std::string> ret = m_current_process->SaveCore(path_hint);
+  if (!ret)
+    return SendErrorResponse(std::move(ret.takeError()));
+
+  StreamString response;
+  response.PutCString("core-path:");
+  response.PutStringAsRawHex8(ret.get());
+  return SendPacketNoLock(response.GetString());
+}
+
 void GDBRemoteCommunicationServerLLGS::MaybeCloseInferiorTerminalConnection() {
   Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_PROCESS));
 
@@ -3800,6 +3839,8 @@ std::vector<std::string> GDBRemoteCommunicationServerLLGS::HandleFeatures(
     ret.push_back("qXfer:libraries-svr4:read+");
   if (bool(plugin_features & Extension::memory_tagging))
     ret.push_back("memory-tagging+");
+  if (bool(plugin_features & Extension::savecore))
+    ret.push_back("qSaveCore+");
 
   // check for client features
   m_extensions_supported = {};
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
index 04d0605..f054e37 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.h
@@ -214,6 +214,8 @@ protected:
 
   PacketResult Handle_QPassSignals(StringExtractorGDBRemote &packet);
 
+  PacketResult Handle_qSaveCore(StringExtractorGDBRemote &packet);
+
   PacketResult Handle_g(StringExtractorGDBRemote &packet);
 
   PacketResult Handle_qMemTags(StringExtractorGDBRemote &packet);
diff --git a/lldb/source/Utility/StringExtractorGDBRemote.cpp b/lldb/source/Utility/StringExtractorGDBRemote.cpp
index 29cf585..7279075 100644
--- a/lldb/source/Utility/StringExtractorGDBRemote.cpp
+++ b/lldb/source/Utility/StringExtractorGDBRemote.cpp
@@ -260,6 +260,8 @@ StringExtractorGDBRemote::GetServerPacketType() const {
       break;
 
     case 'S':
+      if (PACKET_STARTS_WITH("qSaveCore"))
+        return eServerPacketType_qLLDBSaveCore;
       if (PACKET_STARTS_WITH("qSpeedTest:"))
         return eServerPacketType_qSpeedTest;
       if (PACKET_MATCHES("qShlibInfoAddr"))