[lldb] Support SaveCore() from gdb-remote client

Extend PluginManager::SaveCore() to support saving core dumps
via Process plugins.  Implement the client-side part of qSaveCore
request in the gdb-remote plugin, that creates the core dump
on the remote host and then uses vFile packets to transfer it.

Differential Revision: https://reviews.llvm.org/D101329

lldb/include/lldb/Target/Process.h

@@ -687,6 +687,18 @@ public:
                                    "Not implemented");
   }
 
+  /// Save core dump into the specified file.
+  ///
+  /// \param[in] outfile
+  ///     Path to store core dump in.
+  ///
+  /// \return
+  ///     true if saved successfully, false if saving the core dump
+  ///     is not supported by the plugin, error otherwise.
+  virtual llvm::Expected<bool> SaveCore(llvm::StringRef outfile) {
+    return false;
+  }
+
 protected:
   virtual JITLoaderList &GetJITLoaders();
 

lldb/source/Core/PluginManager.cpp

@@ -12,6 +12,7 @@
 #include "lldb/Host/FileSystem.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Interpreter/OptionValueProperties.h"
+#include "lldb/Target/Process.h"
 #include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/FileSpec.h"
 #include "lldb/Utility/Status.h"
@@ -687,6 +688,16 @@ Status PluginManager::SaveCore(const lldb::ProcessSP &process_sp,
                                const FileSpec &outfile,
                                lldb::SaveCoreStyle &core_style,
                                const ConstString plugin_name) {
+  if (!plugin_name) {
+    // Try saving core directly from the process plugin first.
+    llvm::Expected<bool> ret = process_sp->SaveCore(outfile.GetPath());
+    if (!ret)
+      return Status(std::move(ret.takeError()));
+    if (ret.get())
+      return Status();
+  }
+
+  // Fall back to object plugins.
   Status error;
   auto &instances = GetObjectFileInstances().GetInstances();
   for (auto &instance : instances) {

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp

@@ -257,6 +257,7 @@ void GDBRemoteCommunicationClient::ResetDiscoverableSettings(bool did_exec) {
     m_attach_or_wait_reply = eLazyBoolCalculate;
     m_avoid_g_packets = eLazyBoolCalculate;
     m_supports_multiprocess = eLazyBoolCalculate;
+    m_supports_qSaveCore = eLazyBoolCalculate;
     m_supports_qXfer_auxv_read = eLazyBoolCalculate;
     m_supports_qXfer_libraries_read = eLazyBoolCalculate;
     m_supports_qXfer_libraries_svr4_read = eLazyBoolCalculate;
@@ -312,6 +313,7 @@ void GDBRemoteCommunicationClient::GetRemoteQSupported() {
   m_supports_qEcho = eLazyBoolNo;
   m_supports_QPassSignals = eLazyBoolNo;
   m_supports_memory_tagging = eLazyBoolNo;
+  m_supports_qSaveCore = eLazyBoolNo;
 
   m_max_packet_size = UINT64_MAX; // It's supposed to always be there, but if
                                   // not, we assume no limit
@@ -359,6 +361,8 @@ void GDBRemoteCommunicationClient::GetRemoteQSupported() {
         m_supports_multiprocess = eLazyBoolYes;
       else if (x == "memory-tagging+")
         m_supports_memory_tagging = eLazyBoolYes;
+      else if (x == "qSaveCore+")
+        m_supports_qSaveCore = eLazyBoolYes;
       // Look for a list of compressions in the features list e.g.
       // qXfer:features:read+;PacketSize=20000;qEcho+;SupportedCompressions=zlib-
       // deflate,lzma
@@ -501,6 +505,10 @@ LazyBool GDBRemoteCommunicationClient::GetThreadPacketSupported(
   return eLazyBoolNo;
 }
 
+bool GDBRemoteCommunicationClient::GetSaveCoreSupported() const {
+  return m_supports_qSaveCore == eLazyBoolYes;
+}
+
 StructuredData::ObjectSP GDBRemoteCommunicationClient::GetThreadsInfo() {
   // Get information on all threads at one using the "jThreadsInfo" packet
   StructuredData::ObjectSP object_sp;

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h

@@ -547,6 +547,8 @@ public:
   SendTraceGetBinaryData(const TraceGetBinaryDataRequest &request,
                          std::chrono::seconds interrupt_timeout);
 
+  bool GetSaveCoreSupported() const;
+
 protected:
   LazyBool m_supports_not_sending_acks = eLazyBoolCalculate;
   LazyBool m_supports_thread_suffix = eLazyBoolCalculate;
@@ -585,6 +587,7 @@ protected:
   LazyBool m_supports_error_string_reply = eLazyBoolCalculate;
   LazyBool m_supports_multiprocess = eLazyBoolCalculate;
   LazyBool m_supports_memory_tagging = eLazyBoolCalculate;
+  LazyBool m_supports_qSaveCore = eLazyBoolCalculate;
 
   bool m_supports_qProcessInfoPID : 1, m_supports_qfProcessInfo : 1,
       m_supports_qUserName : 1, m_supports_qGroupName : 1,

lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp

@@ -5147,6 +5147,58 @@ void ProcessGDBRemote::HandleStopReply() {
   BuildDynamicRegisterInfo(true);
 }
 
+llvm::Expected<bool> ProcessGDBRemote::SaveCore(llvm::StringRef outfile) {
+  if (!m_gdb_comm.GetSaveCoreSupported())
+    return false;
+
+  StreamString packet;
+  packet.PutCString("qSaveCore;path-hint:");
+  packet.PutStringAsRawHex8(outfile);
+
+  StringExtractorGDBRemote response;
+  if (m_gdb_comm.SendPacketAndWaitForResponse(packet.GetString(), response) ==
+      GDBRemoteCommunication::PacketResult::Success) {
+    // TODO: grab error message from the packet?  StringExtractor seems to
+    // be missing a method for that
+    if (response.IsErrorResponse())
+      return llvm::createStringError(
+          llvm::inconvertibleErrorCode(),
+          llvm::formatv("qSaveCore returned an error"));
+
+    std::string path;
+
+    // process the response
+    llvm::SmallVector<llvm::StringRef, 1> reply_data;
+    response.GetStringRef().split(reply_data, ';');
+    for (auto x : reply_data) {
+      if (x.consume_front("core-path:"))
+        StringExtractor(x).GetHexByteString(path);
+    }
+
+    // verify that we've gotten what we need
+    if (path.empty())
+      return llvm::createStringError(llvm::inconvertibleErrorCode(),
+                                     "qSaveCore returned no core path");
+
+    // now transfer the core file
+    FileSpec remote_core{llvm::StringRef(path)};
+    Platform &platform = *GetTarget().GetPlatform();
+    Status error = platform.GetFile(remote_core, FileSpec(outfile));
+
+    if (platform.IsRemote()) {
+      // NB: we unlink the file on error too
+      platform.Unlink(remote_core);
+      if (error.Fail())
+        return error.ToError();
+    }
+
+    return true;
+  }
+
+  return llvm::createStringError(llvm::inconvertibleErrorCode(),
+                                 "Unable to send qSaveCore");
+}
+
 static const char *const s_async_json_packet_prefix = "JSON-async:";
 
 static StructuredData::ObjectSP

lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h

@@ -235,6 +235,8 @@ public:
   void DidVForkDone() override;
   void DidExec() override;
 
+  llvm::Expected<bool> SaveCore(llvm::StringRef outfile) override;
+
 protected:
   friend class ThreadGDBRemote;
   friend class GDBRemoteCommunicationClient;

lldb/test/API/functionalities/process_save_core/TestProcessSaveCore.py

@@ -63,3 +63,31 @@ class ProcessSaveCoreTestCase(TestBase):
             self.assertTrue(self.dbg.DeleteTarget(target))
             if (os.path.isfile(core)):
                 os.unlink(core)
+
+    @skipUnlessPlatform(["netbsd"])
+    def test_save_core_via_process_plugin(self):
+        self.build()
+        exe = self.getBuildArtifact("a.out")
+        core = self.getBuildArtifact("a.out.core")
+        try:
+            target = self.dbg.CreateTarget(exe)
+            breakpoint = target.BreakpointCreateByName("bar")
+            process = target.LaunchSimple(
+                None, None, self.get_process_working_directory())
+            self.assertEqual(process.GetState(), lldb.eStateStopped)
+            self.assertTrue(process.SaveCore(core))
+            self.assertTrue(os.path.isfile(core))
+            self.assertTrue(process.Kill().Success())
+            pid = process.GetProcessID()
+
+            target = self.dbg.CreateTarget(None)
+            process = target.LoadCore(core)
+            self.assertTrue(process, PROCESS_IS_VALID)
+            self.assertEqual(process.GetProcessID(), pid)
+
+        finally:
+            self.assertTrue(self.dbg.DeleteTarget(target))
+            try:
+                os.unlink(core)
+            except OSError:
+                pass