support ZVirtioConsoleDevice for linux vm (#364)

* support ZVirtioConsoleDevice for linux vm, user can control the vm via serial port with screen command

* cleanup code, fix indent

* add --serial option to tart

* remove serial in vmconfig, fix Serial.swift

---------

Co-authored-by: peternguyen93 <peternguyen9321@gmail.com>
Co-authored-by: peter <peter@starlabs.sg>

Sources/tart/Commands/Run.swift

@@ -20,6 +20,11 @@ struct Run: AsyncParsableCommand {
     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"))
+  var serial: Bool = false
+
   @Flag(help: "Force open a UI window, even when VNC is enabled.")
   var graphics: Bool = false
 
@@ -122,7 +127,8 @@ struct Run: AsyncParsableCommand {
       vmDir: vmDir,
       network: userSpecifiedNetwork(vmDir: vmDir) ?? NetworkShared(),
       additionalDiskAttachments: additionalDiskAttachments,
-      directorySharingDevices: directoryShares() + rosettaDirectoryShare()
+      directorySharingDevices: directoryShares() + rosettaDirectoryShare(),
+      serial: serial
     )
 
     let vncImpl: VNC? = try {

Sources/tart/Serial.swift

@@ -0,0 +1,52 @@
+//
+//  File.swift
+//  
+//
+//  Created by Peter Nguyen on 19/12/2022.
+//
+
+import Foundation
+
+func createPTY() -> Int32
+{
+  var tty_fd: Int32 = -1
+  var sfd: Int32 = -1
+  var termios_ = termios()
+  let tty_path = UnsafeMutablePointer<CChar>.allocate(capacity: 1024)
+    
+  var res = openpty(&tty_fd, &sfd, tty_path, nil, nil);
+  if(res < 0 ){
+    perror("openpty error")
+    return -1
+  }
+    
+  // close slave file descriptor
+  close(sfd)
+        
+  res = fcntl(tty_fd, F_GETFL)
+  if(res < 0){
+    perror("fcntl F_GETFL error")
+    return res
+  }
+    
+  // set serial nonblocking
+  res = fcntl(tty_fd, F_SETFL, res | O_NONBLOCK)
+  if(res < 0){
+    perror("fcntl F_SETFL O_NONBLOCK error")
+    return res
+  }
+    
+  // set baudrate to 115200
+  tcgetattr(tty_fd, &termios_)
+  cfsetispeed(&termios_, speed_t(B115200))
+  cfsetospeed(&termios_, speed_t(B115200))
+  if(tcsetattr(tty_fd, TCSANOW, &termios_) != 0){
+    perror("tcsetattr error")
+    return -1
+  }
+    
+  print("Successfully open pty \(String(cString: tty_path))")
+    
+  tty_path.deallocate()
+  return tty_fd
+}

Sources/tart/VM.swift

@@ -40,7 +40,8 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
   init(vmDir: VMDirectory,
        network: Network = NetworkShared(),
        additionalDiskAttachments: [VZDiskImageStorageDeviceAttachment] = [],
-       directorySharingDevices: [VZDirectorySharingDeviceConfiguration] = []
+       directorySharingDevices: [VZDirectorySharingDeviceConfiguration] = [],
+       serial: Bool = false
   ) throws {
     name = vmDir.name
     config = try VMConfig.init(fromURL: vmDir.configURL)
@@ -54,7 +55,8 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     let configuration = try Self.craftConfiguration(diskURL: vmDir.diskURL,
                                                     nvramURL: vmDir.nvramURL, vmConfig: config,
                                                     network: network, additionalDiskAttachments: additionalDiskAttachments,
-                                                    directorySharingDevices: directorySharingDevices
+                                                    directorySharingDevices: directorySharingDevices,
+                                                    serial: serial
     )
     virtualMachine = VZVirtualMachine(configuration: configuration)
 
@@ -132,7 +134,8 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     diskSizeGB: UInt16,
     network: Network = NetworkShared(),
     additionalDiskAttachments: [VZDiskImageStorageDeviceAttachment] = [],
-    directorySharingDevices: [VZDirectorySharingDeviceConfiguration] = []
+    directorySharingDevices: [VZDirectorySharingDeviceConfiguration] = [],
+    serial: Bool = false
   ) async throws {
     var ipswURL = ipswURL
 
@@ -179,7 +182,8 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     let configuration = try Self.craftConfiguration(diskURL: vmDir.diskURL, nvramURL: vmDir.nvramURL,
                                                     vmConfig: config, network: network,
                                                     additionalDiskAttachments: additionalDiskAttachments,
-                                                    directorySharingDevices: directorySharingDevices
+                                                    directorySharingDevices: directorySharingDevices,
+                                                    serial: serial
     )
     virtualMachine = VZVirtualMachine(configuration: configuration)
 
@@ -261,7 +265,8 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     vmConfig: VMConfig,
     network: Network = NetworkShared(),
     additionalDiskAttachments: [VZDiskImageStorageDeviceAttachment],
-    directorySharingDevices: [VZDirectorySharingDeviceConfiguration]
+    directorySharingDevices: [VZDirectorySharingDeviceConfiguration],
+    serial: Bool
   ) throws -> VZVirtualMachineConfiguration {
     let configuration = VZVirtualMachineConfiguration()
 
@@ -308,6 +313,23 @@ class VM: NSObject, VZVirtualMachineDelegate, ObservableObject {
     // Directory sharing devices
     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
+      }
+    }
+
     try configuration.validate()
 
     return configuration