vmm: pre-create console devices

vmm/src/console_devices.rs

@@ -0,0 +1,303 @@
+// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE-BSD-3-Clause file.
+//
+// Copyright © 2019 Intel Corporation
+// Copyright © 2024 Microsoft Corporation
+//
+// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
+//
+
+use crate::sigwinch_listener::listen_for_sigwinch_on_tty;
+use crate::vm_config::ConsoleOutputMode;
+use crate::Vmm;
+use libc::cfmakeraw;
+use libc::isatty;
+use libc::tcgetattr;
+use libc::tcsetattr;
+use libc::termios;
+use libc::TCSANOW;
+use std::fs::read_link;
+use std::fs::File;
+use std::fs::OpenOptions;
+use std::io;
+#[cfg(target_arch = "x86_64")]
+use std::io::stdout;
+use std::mem::zeroed;
+use std::os::fd::AsRawFd;
+use std::os::fd::FromRawFd;
+use std::os::fd::IntoRawFd;
+use std::os::fd::RawFd;
+use std::os::unix::fs::OpenOptionsExt;
+use std::os::unix::net::UnixListener;
+use std::path::PathBuf;
+use std::result;
+use std::sync::Arc;
+use std::sync::Mutex;
+use thiserror::Error;
+
+const TIOCSPTLCK: libc::c_int = 0x4004_5431;
+const TIOCGPTPEER: libc::c_int = 0x5441;
+
+/// Errors associated with console devices
+#[derive(Debug, Error)]
+pub enum ConsoleDeviceError {
+    /// Error creating console device
+    #[error("Error creating console device: {0}")]
+    CreateConsoleDevice(#[source] io::Error),
+
+    /// Error setting pty raw mode
+    #[error("Error setting pty raw mode: {0}")]
+    SetPtyRaw(#[source] vmm_sys_util::errno::Error),
+
+    /// Cannot duplicate file descriptor
+    #[error("Cannot duplicate file descriptor: {0}")]
+    DupFd(#[source] vmm_sys_util::errno::Error),
+
+    /// Error starting sigwinch listener
+    #[error("Error starting sigwinch listener: {0}")]
+    StartSigwinchListener(#[source] std::io::Error),
+}
+
+type ConsoleDeviceResult<T> = result::Result<T, ConsoleDeviceError>;
+
+#[derive(Default, Clone)]
+pub struct ConsoleInfo {
+    // For each of File, Pty, Tty and Socket modes, below fields  hold the FD
+    // of console, serial and debug devices.
+    pub console_main_fd: Option<RawFd>,
+    pub serial_main_fd: Option<RawFd>,
+    #[cfg(target_arch = "x86_64")]
+    pub debug_main_fd: Option<RawFd>,
+}
+
+fn modify_mode<F: FnOnce(&mut termios)>(
+    fd: RawFd,
+    f: F,
+    original_termios_opt: Arc<Mutex<Option<termios>>>,
+) -> vmm_sys_util::errno::Result<()> {
+    // SAFETY: safe because we check the return value of isatty.
+    if unsafe { isatty(fd) } != 1 {
+        return Ok(());
+    }
+
+    // SAFETY: The following pair are safe because termios gets totally overwritten by tcgetattr
+    // and we check the return result.
+    let mut termios: termios = unsafe { zeroed() };
+    // SAFETY: see above
+    let ret = unsafe { tcgetattr(fd, &mut termios as *mut _) };
+    if ret < 0 {
+        return vmm_sys_util::errno::errno_result();
+    }
+    let mut original_termios_opt = original_termios_opt.lock().unwrap();
+    if original_termios_opt.is_none() {
+        original_termios_opt.replace(termios);
+    }
+
+    f(&mut termios);
+    // SAFETY: Safe because the syscall will only read the extent of termios and we check
+    // the return result.
+    let ret = unsafe { tcsetattr(fd, TCSANOW, &termios as *const _) };
+    if ret < 0 {
+        return vmm_sys_util::errno::errno_result();
+    }
+
+    Ok(())
+}
+
+fn set_raw_mode(
+    f: &dyn AsRawFd,
+    original_termios_opt: Arc<Mutex<Option<termios>>>,
+) -> ConsoleDeviceResult<()> {
+    modify_mode(
+        f.as_raw_fd(),
+        // SAFETY: FFI call. Variable t is guaranteed to be a valid termios from modify_mode.
+        |t| unsafe { cfmakeraw(t) },
+        original_termios_opt,
+    )
+    .map_err(ConsoleDeviceError::SetPtyRaw)
+}
+
+fn create_pty() -> io::Result<(File, File, PathBuf)> {
+    // Try to use /dev/pts/ptmx first then fall back to /dev/ptmx
+    // This is done to try and use the devpts filesystem that
+    // could be available for use in the process's namespace first.
+    // Ideally these are all the same file though but different
+    // kernels could have things setup differently.
+    // See https://www.kernel.org/doc/Documentation/filesystems/devpts.txt
+    // for further details.
+
+    let custom_flags = libc::O_NONBLOCK;
+    let main = match OpenOptions::new()
+        .read(true)
+        .write(true)
+        .custom_flags(custom_flags)
+        .open("/dev/pts/ptmx")
+    {
+        Ok(f) => f,
+        _ => OpenOptions::new()
+            .read(true)
+            .write(true)
+            .custom_flags(custom_flags)
+            .open("/dev/ptmx")?,
+    };
+    let mut unlock: libc::c_ulong = 0;
+    // SAFETY: FFI call into libc, trivially safe
+    unsafe { libc::ioctl(main.as_raw_fd(), TIOCSPTLCK as _, &mut unlock) };
+
+    // SAFETY: FFI call into libc, trivially safe
+    let sub_fd = unsafe {
+        libc::ioctl(
+            main.as_raw_fd(),
+            TIOCGPTPEER as _,
+            libc::O_NOCTTY | libc::O_RDWR,
+        )
+    };
+    if sub_fd == -1 {
+        return vmm_sys_util::errno::errno_result().map_err(|e| e.into());
+    }
+
+    let proc_path = PathBuf::from(format!("/proc/self/fd/{sub_fd}"));
+    let path = read_link(proc_path)?;
+
+    // SAFETY: sub_fd is checked to be valid before being wrapped in File
+    Ok((main, unsafe { File::from_raw_fd(sub_fd) }, path))
+}
+
+pub(crate) fn pre_create_console_devices(vmm: &mut Vmm) -> ConsoleDeviceResult<ConsoleInfo> {
+    let vm_config = vmm.vm_config.as_mut().unwrap().clone();
+    let mut vmconfig = vm_config.lock().unwrap();
+    let mut console_info = ConsoleInfo::default();
+
+    match vmconfig.console.mode {
+        ConsoleOutputMode::File => {
+            let file = File::create(vmconfig.console.file.as_ref().unwrap())
+                .map_err(ConsoleDeviceError::CreateConsoleDevice)?;
+            console_info.console_main_fd = Some(file.into_raw_fd());
+        }
+        ConsoleOutputMode::Pty => {
+            let (main_fd, sub_fd, path) =
+                create_pty().map_err(ConsoleDeviceError::CreateConsoleDevice)?;
+            console_info.console_main_fd = Some(main_fd.into_raw_fd());
+            set_raw_mode(&sub_fd.as_raw_fd(), vmm.original_termios_opt.clone())?;
+            vmconfig.console.file = Some(path.clone());
+            vmm.console_resize_pipe = Some(
+                listen_for_sigwinch_on_tty(
+                    sub_fd,
+                    &vmm.seccomp_action,
+                    vmm.hypervisor.hypervisor_type(),
+                )
+                .map_err(ConsoleDeviceError::StartSigwinchListener)?,
+            );
+        }
+        ConsoleOutputMode::Tty => {
+            // Duplicating the file descriptors like this is needed as otherwise
+            // they will be closed on a reboot and the numbers reused
+
+            // SAFETY: FFI call to dup. Trivially safe.
+            let stdout = unsafe { libc::dup(libc::STDOUT_FILENO) };
+            if stdout == -1 {
+                return vmm_sys_util::errno::errno_result().map_err(ConsoleDeviceError::DupFd);
+            }
+            // SAFETY: stdout is valid and owned solely by us.
+            let stdout = unsafe { File::from_raw_fd(stdout) };
+
+            // SAFETY: FFI call. Trivially safe.
+            if unsafe { libc::isatty(stdout.as_raw_fd()) } == 1 {
+                vmm.console_resize_pipe = Some(
+                    listen_for_sigwinch_on_tty(
+                        stdout.try_clone().unwrap(),
+                        &vmm.seccomp_action,
+                        vmm.hypervisor.hypervisor_type(),
+                    )
+                    .map_err(ConsoleDeviceError::StartSigwinchListener)?,
+                );
+            }
+
+            // Make sure stdout is in raw mode, if it's a terminal.
+            set_raw_mode(&stdout, vmm.original_termios_opt.clone())?;
+            console_info.console_main_fd = Some(stdout.into_raw_fd());
+        }
+        ConsoleOutputMode::Null | ConsoleOutputMode::Socket | ConsoleOutputMode::Off => {}
+    }
+
+    match vmconfig.serial.mode {
+        ConsoleOutputMode::File => {
+            let file = File::create(vmconfig.serial.file.as_ref().unwrap())
+                .map_err(ConsoleDeviceError::CreateConsoleDevice)?;
+            console_info.serial_main_fd = Some(file.into_raw_fd());
+        }
+        ConsoleOutputMode::Pty => {
+            let (main_fd, sub_fd, path) =
+                create_pty().map_err(ConsoleDeviceError::CreateConsoleDevice)?;
+            console_info.serial_main_fd = Some(main_fd.into_raw_fd());
+            set_raw_mode(&sub_fd.as_raw_fd(), vmm.original_termios_opt.clone())?;
+            vmconfig.serial.file = Some(path.clone());
+        }
+        ConsoleOutputMode::Tty => {
+            // During vm_shutdown, when serial device is closed, FD#2(STDOUT)
+            // will be closed and FD#2 could be reused in a future boot of the
+            // guest by a different file.
+            //
+            // To ensure FD#2 always points to STANDARD OUT, a `dup` of STDOUT
+            // is passed to serial device. Doing so, even if the serial device
+            // were to be closed, FD#2 will continue to point to STANDARD OUT.
+
+            // SAFETY: FFI call to dup. Trivially safe.
+            let stdout = unsafe { libc::dup(libc::STDOUT_FILENO) };
+            if stdout == -1 {
+                return vmm_sys_util::errno::errno_result().map_err(ConsoleDeviceError::DupFd);
+            }
+            // SAFETY: stdout is valid and owned solely by us.
+            let stdout = unsafe { File::from_raw_fd(stdout) };
+
+            // SAFETY: FFI call. Trivially safe.
+            if unsafe { libc::isatty(stdout.as_raw_fd()) } == 1 {
+                vmm.console_resize_pipe = Some(
+                    listen_for_sigwinch_on_tty(
+                        stdout.try_clone().unwrap(),
+                        &vmm.seccomp_action,
+                        vmm.hypervisor.hypervisor_type(),
+                    )
+                    .map_err(ConsoleDeviceError::StartSigwinchListener)?,
+                );
+            }
+
+            // Make sure stdout is in raw mode, if it's a terminal.
+            set_raw_mode(&stdout, vmm.original_termios_opt.clone())?;
+            console_info.serial_main_fd = Some(stdout.into_raw_fd());
+        }
+        ConsoleOutputMode::Socket => {
+            let listener = UnixListener::bind(vmconfig.serial.socket.as_ref().unwrap())
+                .map_err(ConsoleDeviceError::CreateConsoleDevice)?;
+            console_info.serial_main_fd = Some(listener.into_raw_fd());
+        }
+        ConsoleOutputMode::Null | ConsoleOutputMode::Off => {}
+    }
+
+    #[cfg(target_arch = "x86_64")]
+    match vmconfig.debug_console.mode {
+        ConsoleOutputMode::File => {
+            let file = File::create(vmconfig.debug_console.file.as_ref().unwrap())
+                .map_err(ConsoleDeviceError::CreateConsoleDevice)?;
+            console_info.debug_main_fd = Some(file.into_raw_fd());
+        }
+        ConsoleOutputMode::Pty => {
+            let (main_fd, sub_fd, path) =
+                create_pty().map_err(ConsoleDeviceError::CreateConsoleDevice)?;
+            console_info.debug_main_fd = Some(main_fd.into_raw_fd());
+            set_raw_mode(&sub_fd.as_raw_fd(), vmm.original_termios_opt.clone())?;
+            vmconfig.debug_console.file = Some(path.clone());
+        }
+        ConsoleOutputMode::Tty => {
+            let out = stdout();
+            console_info.debug_main_fd = Some(out.as_raw_fd());
+            set_raw_mode(&out, vmm.original_termios_opt.clone())?;
+        }
+        ConsoleOutputMode::Null | ConsoleOutputMode::Socket | ConsoleOutputMode::Off => {}
+    }
+
+    Ok(console_info)
+}