Option to pass externally created serial console (#448)

* Option to pass externally created serial console

See https://github.com/cirruslabs/tart/pull/364#issuecomment-1472111742 for details

* Fixed compilation

* Apply suggestions from code review

Co-authored-by: Nikolay Edigaryev <edigaryev@gmail.com>

---------

Co-authored-by: Nikolay Edigaryev <edigaryev@gmail.com>

Sources/tart/Commands/Run.swift

@@ -17,18 +17,24 @@ struct Run: AsyncParsableCommand {
 
   @Flag(help: ArgumentHelp(
     "Don't open a UI window.",
-    discussion: "Useful for integrating Tart VMs into other tools.\nUse `tart ip` in order to get an IP for SSHing or VNCing into the VM.")) 
+    discussion: "Useful for integrating Tart VMs into other tools.\nUse `tart ip` in order to get an IP for SSHing or VNCing into the VM."))
   var noGraphics: Bool = false
 
   @Flag(help: ArgumentHelp(
     "Open serial console in /dev/ttySXX",
-    discussion: "Useful for debugging Linux Kernel"))
+    discussion: "Useful for debugging Linux Kernel."))
   var serial: Bool = false
 
+  @Option(help: ArgumentHelp(
+    "Attach an externally created serial console",
+    discussion: "Alternative to `--serial` flag for programmatic integrations."
+  ))
+  var serialPath: String?
+
   @Flag(help: "Force open a UI window, even when VNC is enabled.")
   var graphics: Bool = false
 
-  @Flag(help: "Boot into recovery mode") 
+  @Flag(help: "Boot into recovery mode")
   var recovery: Bool = false
 
   @Flag(help: ArgumentHelp(
@@ -123,12 +129,30 @@ struct Run: AsyncParsableCommand {
       }
     }
 
+    var serialPorts: [VZSerialPortConfiguration] = []
+    if serial {
+      let tty_fd = createPTY()
+      if (tty_fd < 0) {
+        throw RuntimeError.VMConfigurationError("Failed to create PTY")
+      }
+      let tty_read = FileHandle.init(fileDescriptor: tty_fd)
+      let tty_write = FileHandle.init(fileDescriptor: tty_fd)
+      serialPorts.append(createSerialPortConfiguration(tty_read, tty_write))
+    } else if serialPath != nil {
+      let tty_read = FileHandle.init(forReadingAtPath: serialPath!)
+      let tty_write = FileHandle.init(forWritingAtPath: serialPath!)
+      if (tty_read == nil || tty_write == nil) {
+        throw RuntimeError.VMConfigurationError("Failed to open PTY")
+      }
+      serialPorts.append(createSerialPortConfiguration(tty_read!, tty_write!))
+    }
+
     vm = try VM(
       vmDir: vmDir,
       network: userSpecifiedNetwork(vmDir: vmDir) ?? NetworkShared(),
       additionalDiskAttachments: additionalDiskAttachments,
       directorySharingDevices: directoryShares() + rosettaDirectoryShare(),
-      serial: serial
+      serialPorts: serialPorts
     )
 
     let vncImpl: VNC? = try {
@@ -204,6 +228,16 @@ struct Run: AsyncParsableCommand {
     }
   }
 
+  private func createSerialPortConfiguration(_ tty_read: FileHandle, _ tty_write: FileHandle) -> VZVirtioConsoleDeviceSerialPortConfiguration {
+    let serialPortConfiguration = VZVirtioConsoleDeviceSerialPortConfiguration()
+    let serialPortAttachment = VZFileHandleSerialPortAttachment(
+      fileHandleForReading: tty_read,
+      fileHandleForWriting: tty_write)
+
+    serialPortConfiguration.attachment = serialPortAttachment
+    return serialPortConfiguration
+  }
+
   func isInteractiveSession() -> Bool {
     isatty(STDOUT_FILENO) == 1
   }

Sources/tart/VM.swift

@@ -41,7 +41,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
        network: Network = NetworkShared(),
        additionalDiskAttachments: [VZDiskImageStorageDeviceAttachment] = [],
        directorySharingDevices: [VZDirectorySharingDeviceConfiguration] = [],
-       serial: Bool = false
+       serialPorts: [VZSerialPortConfiguration] = []
   ) throws {
     name = vmDir.name
     config = try VMConfig.init(fromURL: vmDir.configURL)
@@ -56,7 +56,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
                                                     nvramURL: vmDir.nvramURL, vmConfig: config,
                                                     network: network, additionalDiskAttachments: additionalDiskAttachments,
                                                     directorySharingDevices: directorySharingDevices,
-                                                    serial: serial
+                                                    serialPorts: serialPorts
     )
     virtualMachine = VZVirtualMachine(configuration: configuration)
 
@@ -135,7 +135,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     network: Network = NetworkShared(),
     additionalDiskAttachments: [VZDiskImageStorageDeviceAttachment] = [],
     directorySharingDevices: [VZDirectorySharingDeviceConfiguration] = [],
-    serial: Bool = false
+    serialPorts: [VZSerialPortConfiguration] = []
   ) async throws {
     var ipswURL = ipswURL
 
@@ -183,7 +183,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
                                                     vmConfig: config, network: network,
                                                     additionalDiskAttachments: additionalDiskAttachments,
                                                     directorySharingDevices: directorySharingDevices,
-                                                    serial: serial
+                                                    serialPorts: serialPorts
     )
     virtualMachine = VZVirtualMachine(configuration: configuration)
 
@@ -266,7 +266,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     network: Network = NetworkShared(),
     additionalDiskAttachments: [VZDiskImageStorageDeviceAttachment],
     directorySharingDevices: [VZDirectorySharingDeviceConfiguration],
-    serial: Bool
+    serialPorts: [VZSerialPortConfiguration]
   ) throws -> VZVirtualMachineConfiguration {
     let configuration = VZVirtualMachineConfiguration()
 
@@ -314,21 +314,7 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     configuration.directorySharingDevices = directorySharingDevices
 
     // Serial Port
-    if serial {
-      let tty_fd = createPTY()
-      if(tty_fd > -1){
-        let tty_read = FileHandle.init(fileDescriptor: tty_fd)
-        let tty_write = FileHandle.init(fileDescriptor: tty_fd)
-
-
-        configuration.serialPorts = [VZVirtioConsoleDeviceSerialPortConfiguration()]
-        let serialPortAttachment = VZFileHandleSerialPortAttachment(
-          fileHandleForReading: tty_read,
-          fileHandleForWriting: tty_write)
-
-        configuration.serialPorts[0].attachment = serialPortAttachment
-      }
-    }
+    configuration.serialPorts = serialPorts
 
     try configuration.validate()
 

Sources/tart/VMStorageHelper.swift

@@ -41,6 +41,7 @@ extension Error {
 }
 
 enum RuntimeError : Error {
+  case VMConfigurationError(_ message: String)
   case VMDoesNotExist(name: String)
   case VMMissingFiles(_ message: String)
   case VMNotRunning(_ message: String)
@@ -65,6 +66,8 @@ protocol HasExitCode {
 extension RuntimeError : CustomStringConvertible {
   public var description: String {
     switch self {
+    case .VMConfigurationError(let message):
+      return message
     case .VMDoesNotExist(let name):
       return "the specified VM \"\(name)\" does not exist"
     case .VMMissingFiles(let message):