src/starnix/kernel/core/fs/devpts.rs

// Copyright 2021 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use crate::device::DeviceMode;
use crate::device::kobject::DeviceMetadata;
use crate::device::terminal::{Terminal, TtyState};
use crate::fs::sysfs::build_device_directory;
use crate::mm::MemoryAccessorExt;
use crate::task::{CurrentTask, EventHandler, Kernel, KernelOrTask, WaitCanceler, Waiter};
use crate::vfs::buffers::{InputBuffer, OutputBuffer};
use crate::vfs::pseudo::vec_directory::{VecDirectory, VecDirectoryEntry};
use crate::vfs::{
    CacheMode, DirectoryEntryType, FileHandle, FileObject, FileObjectState, FileOps, FileSystem,
    FileSystemHandle, FileSystemOps, FileSystemOptions, FsNode, FsNodeHandle, FsNodeInfo,
    FsNodeOps, FsStr, FsString, LookupContext, NamespaceNode, SpecialNode, SymlinkMode,
    fileops_impl_nonseekable, fileops_impl_noop_sync, fs_node_impl_dir_readonly,
};
use starnix_logging::track_stub;
use starnix_sync::{
    FileOpsCore, LockBefore, LockEqualOrBefore, Locked, ProcessGroupState, Unlocked,
};
use starnix_syscalls::{SUCCESS, SyscallArg, SyscallResult};
use starnix_types::vfs::default_statfs;
use starnix_uapi::auth::FsCred;
use starnix_uapi::device_type::{DeviceType, TTY_ALT_MAJOR};
use starnix_uapi::errors::Errno;
use starnix_uapi::file_mode::mode;
use starnix_uapi::open_flags::OpenFlags;
use starnix_uapi::signals::SIGWINCH;
use starnix_uapi::user_address::{UserAddress, UserRef};
use starnix_uapi::vfs::FdEvents;
use starnix_uapi::{
    DEVPTS_SUPER_MAGIC, FIOASYNC, FIOCLEX, FIONBIO, FIONCLEX, FIONREAD, FIOQSIZE, TCFLSH, TCGETA,
    TCGETS, TCGETX, TCSBRK, TCSBRKP, TCSETA, TCSETAF, TCSETAW, TCSETS, TCSETSF, TCSETSW, TCSETX,
    TCSETXF, TCSETXW, TCXONC, TIOCCBRK, TIOCCONS, TIOCEXCL, TIOCGETD, TIOCGICOUNT, TIOCGLCKTRMIOS,
    TIOCGPGRP, TIOCGPTLCK, TIOCGPTN, TIOCGRS485, TIOCGSERIAL, TIOCGSID, TIOCGSOFTCAR, TIOCGWINSZ,
    TIOCLINUX, TIOCMBIC, TIOCMBIS, TIOCMGET, TIOCMIWAIT, TIOCMSET, TIOCNOTTY, TIOCNXCL, TIOCOUTQ,
    TIOCPKT, TIOCSBRK, TIOCSCTTY, TIOCSERCONFIG, TIOCSERGETLSR, TIOCSERGETMULTI, TIOCSERGSTRUCT,
    TIOCSERGWILD, TIOCSERSETMULTI, TIOCSERSWILD, TIOCSETD, TIOCSLCKTRMIOS, TIOCSPGRP, TIOCSPTLCK,
    TIOCSRS485, TIOCSSERIAL, TIOCSSOFTCAR, TIOCSTI, TIOCSWINSZ, TIOCVHANGUP, errno, error, gid_t,
    ino_t, pid_t, statfs, uapi, uid_t,
};
use std::sync::{Arc, Weak};

// See https://www.kernel.org/doc/Documentation/admin-guide/devices.txt
const DEVPTS_FIRST_MAJOR: u32 = 136;
const DEVPTS_MAJOR_COUNT: u32 = 4;
// The device identifier is encoded through the major and minor device identifier of the
// device. Each major identifier can contain 256 pts replicas.
pub const DEVPTS_COUNT: u32 = DEVPTS_MAJOR_COUNT * 256;
// The block size of the node in the devpts file system. Value has been taken from
// https://github.com/google/gvisor/blob/master/test/syscalls/linux/pty.cc
const BLOCK_SIZE: usize = 1024;

// The node identifier of the different node in the devpts filesystem.
const ROOT_NODE_ID: ino_t = 1;
const PTMX_NODE_ID: ino_t = 2;
const FIRST_PTS_NODE_ID: ino_t = 3;

pub fn dev_pts_fs(
    locked: &mut Locked<Unlocked>,
    current_task: &CurrentTask,
    options: FileSystemOptions,
) -> Result<FileSystemHandle, Errno> {
    new_pts_fs(locked, &current_task.kernel(), options)
}

pub fn new_pts_fs(
    locked: &mut Locked<Unlocked>,
    kernel: &Kernel,
    options: FileSystemOptions,
) -> Result<FileSystemHandle, Errno> {
    let state = if options.params.get(b"newinstance").is_some() {
        Arc::new(TtyState::default())
    } else {
        kernel.expando.get::<TtyState>()
    };

    new_pts_fs_with_state(locked, kernel, options, state)
}

pub fn new_pts_fs_with_state(
    locked: &mut Locked<Unlocked>,
    kernel: &Kernel,
    options: FileSystemOptions,
    state: Arc<TtyState>,
) -> Result<FileSystemHandle, Errno> {
    let parse_octal = |m: &str| u32::from_str_radix(m, 8);
    let uid = options.params.get_as::<uid_t>(b"uid")?;
    let gid = options.params.get_as::<gid_t>(b"gid")?;
    let mode = options.params.get_with(b"mode", parse_octal)?.unwrap_or(0o600);
    let ptmxmode = options.params.get_with(b"ptmxmode", parse_octal)?.unwrap_or(0);

    let dev_pts_fs = DevPtsFs { state: state.clone(), uid, gid, mode, ptmxmode };

    let fs = FileSystem::new(locked, kernel, CacheMode::Uncached, dev_pts_fs, options)
        .expect("devpts filesystem constructed with valid options");
    fs.create_root(ROOT_NODE_ID, DevPtsRootDir { state });
    Ok(fs)
}

/// Creates a terminal and returns the main pty and an associated replica pts.
///
/// This function assumes that `/dev/ptmx` is the `DevPtmxFile` and that devpts
/// is mounted at `/dev/pts`. These assumptions are necessary so that the
/// `FileHandle` objects returned have appropriate `NamespaceNode` objects.
pub fn create_main_and_replica(
    locked: &mut Locked<Unlocked>,
    current_task: &CurrentTask,
    window_size: uapi::winsize,
) -> Result<(FileHandle, FileHandle), Errno> {
    let pty_file = current_task.open_file(locked, "/dev/ptmx".into(), OpenFlags::RDWR)?;
    let pty = pty_file.downcast_file::<DevPtmxFile>().ok_or_else(|| errno!(ENOTTY))?;
    {
        let mut terminal = pty.terminal.write();
        terminal.locked = false;
        terminal.window_size = window_size;
    }
    let pts_path = FsString::from(format!("/dev/pts/{}", pty.terminal.id));
    let pts_file = current_task.open_file(locked, pts_path.as_ref(), OpenFlags::RDWR)?;
    Ok((pty_file, pts_file))
}

pub fn tty_device_init<'a, L>(
    locked: &mut Locked<L>,
    kernel_or_task: impl KernelOrTask<'a>,
) -> Result<(), Errno>
where
    L: LockEqualOrBefore<FileOpsCore>,
{
    let kernel = kernel_or_task.kernel();

    let registry = &kernel.device_registry;

    // Register /dev/pts/X device type.
    for n in 0..DEVPTS_MAJOR_COUNT {
        registry
            .register_major(
                locked.cast_locked(),
                "pts".into(),
                DeviceMode::Char,
                DEVPTS_FIRST_MAJOR + n,
                open_dev_pts_device,
            )
            .expect("can register pts{n} device");
    }

    // Register tty and ptmx device types.
    kernel
        .device_registry
        .register_major(
            locked.cast_locked(),
            "/dev/tty".into(),
            DeviceMode::Char,
            TTY_ALT_MAJOR,
            open_dev_pts_device,
        )
        .expect("can register tty device");

    let tty_class = registry.objects.tty_class();
    registry.add_device(
        locked,
        kernel_or_task,
        "tty".into(),
        DeviceMetadata::new("tty".into(), DeviceType::TTY, DeviceMode::Char),
        tty_class.clone(),
        build_device_directory,
    )?;
    registry.add_device(
        locked,
        kernel_or_task,
        "ptmx".into(),
        DeviceMetadata::new("ptmx".into(), DeviceType::PTMX, DeviceMode::Char),
        tty_class,
        build_device_directory,
    )?;
    Ok(())
}

struct DevPtsFs {
    state: Arc<TtyState>,
    uid: Option<uid_t>,
    gid: Option<gid_t>,
    mode: u32,
    ptmxmode: u32,
}

impl FileSystemOps for DevPtsFs {
    fn statfs(
        &self,
        _locked: &mut Locked<FileOpsCore>,
        _fs: &FileSystem,
        _current_task: &CurrentTask,
    ) -> Result<statfs, Errno> {
        Ok(default_statfs(DEVPTS_SUPER_MAGIC))
    }
    fn name(&self) -> &'static FsStr {
        "devpts".into()
    }

    fn uses_external_node_ids(&self) -> bool {
        false
    }
}

impl DevPtsFs {
    fn pty_creds_for(&self, current_task: &CurrentTask) -> FsCred {
        let uid = self.uid.unwrap_or_else(|| current_task.with_current_creds(|creds| creds.uid));
        let gid = self.gid.unwrap_or_else(|| current_task.with_current_creds(|creds| creds.gid));
        FsCred { uid, gid }
    }
}

// Construct the DeviceType associated with the given pts replicas.
pub fn get_device_type_for_pts(id: u32) -> DeviceType {
    DeviceType::new(DEVPTS_FIRST_MAJOR + id / 256, id % 256)
}

struct DevPtsRootDir {
    state: Arc<TtyState>,
}

impl FsNodeOps for DevPtsRootDir {
    fs_node_impl_dir_readonly!();

    fn create_file_ops(
        &self,
        _locked: &mut Locked<FileOpsCore>,
        _node: &FsNode,
        _current_task: &CurrentTask,
        _flags: OpenFlags,
    ) -> Result<Box<dyn FileOps>, Errno> {
        let mut result = vec![];
        result.push(VecDirectoryEntry {
            entry_type: DirectoryEntryType::CHR,
            name: "ptmx".into(),
            inode: Some(PTMX_NODE_ID),
        });
        for (id, terminal) in self.state.terminals.read().iter() {
            if let Some(terminal) = terminal.upgrade() {
                if !terminal.read().is_main_closed() {
                    result.push(VecDirectoryEntry {
                        entry_type: DirectoryEntryType::CHR,
                        name: format!("{id}").into(),
                        inode: Some((*id as ino_t) + FIRST_PTS_NODE_ID),
                    });
                }
            }
        }
        Ok(VecDirectory::new_file(result))
    }

    fn lookup(
        &self,
        _locked: &mut Locked<FileOpsCore>,
        node: &FsNode,
        _current_task: &CurrentTask,
        name: &FsStr,
    ) -> Result<FsNodeHandle, Errno> {
        let fs = node.fs();
        let devptsfs =
            fs.downcast_ops::<DevPtsFs>().expect("DevPts should only handle `DevPtsFs`s");
        let name = std::str::from_utf8(name).map_err(|_| errno!(ENOENT))?;
        if name == "ptmx" {
            let mut info = FsNodeInfo::new(mode!(IFCHR, devptsfs.ptmxmode), FsCred::root());
            info.rdev = DeviceType::PTMX;
            info.blksize = BLOCK_SIZE;
            let node = fs.create_node(PTMX_NODE_ID, SpecialNode, info);
            return Ok(node);
        }
        if let Ok(id) = name.parse::<u32>() {
            let terminal = self.state.terminals.read().get(&id).and_then(Weak::upgrade);
            if let Some(terminal) = terminal {
                if !terminal.read().is_main_closed() {
                    let ino = (id as ino_t) + FIRST_PTS_NODE_ID;
                    let mut info =
                        FsNodeInfo::new(mode!(IFCHR, devptsfs.mode), terminal.fscred.clone());
                    info.rdev = get_device_type_for_pts(id);
                    info.blksize = BLOCK_SIZE;
                    let node = fs.create_node(ino, SpecialNode, info);
                    return Ok(node);
                }
            }
        }
        error!(ENOENT)
    }
}

fn open_dev_pts_device(
    locked: &mut Locked<FileOpsCore>,
    current_task: &CurrentTask,
    id: DeviceType,
    node: &NamespaceNode,
    flags: OpenFlags,
) -> Result<Box<dyn FileOps>, Errno> {
    match id {
        // /dev/ptmx and /dev/pts/ptmx
        DeviceType::PTMX => {
            let fs = node.entry.node.fs();
            let Some(devpts_fs) = fs.downcast_ops::<DevPtsFs>() else {
                // The device is not in ptmx, let try to find something at pts/ptmx relative to
                // the parent of the node
                let parent = node.parent().ok_or_else(|| errno!(EINVAL))?;
                let mut lookup_context = LookupContext::new(SymlinkMode::Follow);
                let ptmx_node = current_task.lookup_path(
                    locked,
                    &mut lookup_context,
                    parent,
                    "pts/ptmx".into(),
                )?;
                return open_dev_pts_device(locked, current_task, id, &ptmx_node, flags);
            };

            let terminal = devpts_fs
                .state
                .get_next_terminal(fs.root().clone(), devpts_fs.pty_creds_for(current_task))?;
            Ok(Box::new(DevPtmxFile::new(terminal)))
        }
        // /dev/tty
        DeviceType::TTY => {
            let controlling_terminal = current_task
                .thread_group()
                .read()
                .process_group
                .session
                .read()
                .controlling_terminal
                .clone();
            if let Some(controlling_terminal) = controlling_terminal {
                if controlling_terminal.is_main {
                    Ok(Box::new(DevPtmxFile::new(controlling_terminal.terminal)))
                } else {
                    Ok(Box::new(TtyFile::new(controlling_terminal.terminal)))
                }
            } else {
                error!(ENXIO)
            }
        }
        _ if id.major() < DEVPTS_FIRST_MAJOR
            || id.major() >= DEVPTS_FIRST_MAJOR + DEVPTS_MAJOR_COUNT =>
        {
            error!(ENODEV)
        }
        // /dev/pts/??
        _ => {
            let fs = node.entry.node.fs();
            let Some(devpts_fs) = fs.downcast_ops::<DevPtsFs>() else {
                return error!(ENOTSUP);
            };
            let pts_id = (id.major() - DEVPTS_FIRST_MAJOR) * 256 + id.minor();
            let terminal = devpts_fs
                .state
                .terminals
                .read()
                .get(&pts_id)
                .and_then(Weak::upgrade)
                .ok_or_else(|| errno!(EIO))?;
            if terminal.read().locked {
                return error!(EIO);
            }
            if !flags.contains(OpenFlags::NOCTTY) {
                // Opening a replica sets the process' controlling TTY when possible. An error indicates it cannot
                // be set, and is ignored silently.
                let _ = current_task.thread_group().set_controlling_terminal(
                    current_task,
                    &terminal,
                    false, /* is_main */
                    false, /* steal */
                    flags.can_read(),
                );
            }
            Ok(Box::new(TtyFile::new(terminal)))
        }
    }
}

struct DevPtmxFile {
    terminal: Arc<Terminal>,
}

impl DevPtmxFile {
    pub fn new(terminal: Arc<Terminal>) -> Self {
        terminal.main_open();
        Self { terminal }
    }
}

impl FileOps for DevPtmxFile {
    fileops_impl_nonseekable!();
    fileops_impl_noop_sync!();

    fn close(
        self: Box<Self>,
        _locked: &mut Locked<FileOpsCore>,
        _file: &FileObjectState,
        _current_task: &CurrentTask,
    ) {
        self.terminal.main_close();
    }

    fn read(
        &self,
        locked: &mut Locked<FileOpsCore>,
        file: &FileObject,
        current_task: &CurrentTask,
        offset: usize,
        data: &mut dyn OutputBuffer,
    ) -> Result<usize, Errno> {
        debug_assert!(offset == 0);
        file.blocking_op(
            locked,
            current_task,
            FdEvents::POLLIN | FdEvents::POLLHUP,
            None,
            |locked| self.terminal.main_read(locked, data),
        )
    }

    fn write(
        &self,
        locked: &mut Locked<FileOpsCore>,
        file: &FileObject,
        current_task: &CurrentTask,
        offset: usize,
        data: &mut dyn InputBuffer,
    ) -> Result<usize, Errno> {
        debug_assert!(offset == 0);
        file.blocking_op(
            locked,
            current_task,
            FdEvents::POLLOUT | FdEvents::POLLHUP,
            None,
            |locked| self.terminal.main_write(locked, data),
        )
    }

    fn wait_async(
        &self,
        _locked: &mut Locked<FileOpsCore>,
        _file: &FileObject,
        _current_task: &CurrentTask,
        waiter: &Waiter,
        events: FdEvents,
        handler: EventHandler,
    ) -> Option<WaitCanceler> {
        Some(self.terminal.main_wait_async(waiter, events, handler))
    }

    fn query_events(
        &self,
        _locked: &mut Locked<FileOpsCore>,
        _file: &FileObject,
        _current_task: &CurrentTask,
    ) -> Result<FdEvents, Errno> {
        Ok(self.terminal.main_query_events())
    }

    fn ioctl(
        &self,
        locked: &mut Locked<Unlocked>,
        _file: &FileObject,
        current_task: &CurrentTask,
        request: u32,
        arg: SyscallArg,
    ) -> Result<SyscallResult, Errno> {
        let user_addr = UserAddress::from(arg);
        match request {
            TIOCGPTN => {
                // Get the terminal id.
                let value: u32 = self.terminal.id;
                current_task.write_object(UserRef::<u32>::new(user_addr), &value)?;
                Ok(SUCCESS)
            }
            TIOCGPTLCK => {
                // Get the lock status.
                let value = i32::from(self.terminal.read().locked);
                current_task.write_object(UserRef::<i32>::new(user_addr), &value)?;
                Ok(SUCCESS)
            }
            TIOCSPTLCK => {
                // Lock/Unlock the terminal.
                let value = current_task.read_object(UserRef::<i32>::new(user_addr))?;
                self.terminal.write().locked = value != 0;
                Ok(SUCCESS)
            }
            _ => shared_ioctl(locked, &self.terminal, true, _file, current_task, request, arg),
        }
    }
}

pub struct TtyFile {
    terminal: Arc<Terminal>,
}

impl TtyFile {
    pub fn new(terminal: Arc<Terminal>) -> Self {
        terminal.replica_open();
        Self { terminal }
    }
}

impl FileOps for TtyFile {
    fileops_impl_nonseekable!();
    fileops_impl_noop_sync!();

    fn close(
        self: Box<Self>,
        _locked: &mut Locked<FileOpsCore>,
        _file: &FileObjectState,
        _current_task: &CurrentTask,
    ) {
        self.terminal.replica_close();
    }

    fn read(
        &self,
        locked: &mut Locked<FileOpsCore>,
        file: &FileObject,
        current_task: &CurrentTask,
        offset: usize,
        data: &mut dyn OutputBuffer,
    ) -> Result<usize, Errno> {
        debug_assert!(offset == 0);
        file.blocking_op(
            locked,
            current_task,
            FdEvents::POLLIN | FdEvents::POLLHUP,
            None,
            |locked| self.terminal.replica_read(locked, data),
        )
    }

    fn write(
        &self,
        locked: &mut Locked<FileOpsCore>,
        file: &FileObject,
        current_task: &CurrentTask,
        offset: usize,
        data: &mut dyn InputBuffer,
    ) -> Result<usize, Errno> {
        debug_assert!(offset == 0);
        file.blocking_op(
            locked,
            current_task,
            FdEvents::POLLOUT | FdEvents::POLLHUP,
            None,
            |locked| self.terminal.replica_write(locked, data),
        )
    }

    fn wait_async(
        &self,
        _locked: &mut Locked<FileOpsCore>,
        _file: &FileObject,
        _current_task: &CurrentTask,
        waiter: &Waiter,
        events: FdEvents,
        handler: EventHandler,
    ) -> Option<WaitCanceler> {
        Some(self.terminal.replica_wait_async(waiter, events, handler))
    }

    fn query_events(
        &self,
        _locked: &mut Locked<FileOpsCore>,
        _file: &FileObject,
        _current_task: &CurrentTask,
    ) -> Result<FdEvents, Errno> {
        Ok(self.terminal.replica_query_events())
    }

    fn ioctl(
        &self,
        locked: &mut Locked<Unlocked>,
        file: &FileObject,
        current_task: &CurrentTask,
        request: u32,
        arg: SyscallArg,
    ) -> Result<SyscallResult, Errno> {
        shared_ioctl(locked, &self.terminal, false, file, current_task, request, arg)
    }
}

fn into_termios(value: uapi::termio) -> uapi::termios {
    let mut cc = [0; 19];
    cc[0..8].copy_from_slice(&value.c_cc[0..8]);
    uapi::termios {
        c_iflag: value.c_iflag as uapi::tcflag_t,
        c_oflag: value.c_oflag as uapi::tcflag_t,
        c_cflag: value.c_cflag as uapi::tcflag_t,
        c_lflag: value.c_lflag as uapi::tcflag_t,
        c_line: value.c_line as uapi::cc_t,
        c_cc: cc,
    }
}

fn into_termio(value: uapi::termios) -> uapi::termio {
    let mut cc = [0; 8];
    cc.copy_from_slice(&value.c_cc[0..8]);
    uapi::termio {
        c_iflag: value.c_iflag as u16,
        c_oflag: value.c_oflag as u16,
        c_cflag: value.c_cflag as u16,
        c_lflag: value.c_lflag as u16,
        c_line: value.c_line,
        c_cc: cc,
        ..Default::default()
    }
}

/// The ioctl behaviour common to main and replica terminal file descriptors.
fn shared_ioctl<L>(
    locked: &mut Locked<L>,
    terminal: &Terminal,
    is_main: bool,
    file: &FileObject,
    current_task: &CurrentTask,
    request: u32,
    arg: SyscallArg,
) -> Result<SyscallResult, Errno>
where
    L: LockBefore<ProcessGroupState>,
{
    let user_addr = UserAddress::from(arg);
    match request {
        FIONREAD => {
            // Get the main terminal available bytes for reading.
            let value = terminal.read().get_available_read_size(is_main) as u32;
            current_task.write_object(UserRef::<u32>::new(user_addr), &value)?;
            Ok(SUCCESS)
        }
        TIOCSCTTY => {
            // Make the given terminal the controlling terminal of the calling process.
            let steal = bool::from(arg);
            current_task.thread_group().set_controlling_terminal(
                current_task,
                terminal,
                is_main,
                steal,
                file.can_read(),
            )?;
            Ok(SUCCESS)
        }
        TIOCNOTTY => {
            // Release the controlling terminal.
            current_task.thread_group().release_controlling_terminal(
                locked,
                current_task,
                terminal,
                is_main,
            )?;
            Ok(SUCCESS)
        }
        TIOCGPGRP => {
            // Get the foreground process group.
            let pgid = current_task.thread_group().get_foreground_process_group(terminal)?;
            current_task.write_object(UserRef::<pid_t>::new(user_addr), &pgid)?;
            Ok(SUCCESS)
        }
        TIOCSPGRP => {
            // Set the foreground process group.
            let pgid = current_task.read_object(UserRef::<pid_t>::new(user_addr))?;
            current_task.thread_group().set_foreground_process_group(
                locked,
                current_task,
                terminal,
                pgid,
            )?;
            Ok(SUCCESS)
        }
        TIOCGWINSZ => {
            // Get the window size
            current_task.write_object(
                UserRef::<uapi::winsize>::new(user_addr),
                &terminal.read().window_size,
            )?;
            Ok(SUCCESS)
        }
        TIOCSWINSZ => {
            // Set the window size
            terminal.write().window_size =
                current_task.read_object(UserRef::<uapi::winsize>::new(user_addr))?;

            // Send a SIGWINCH signal to the foreground process group.
            let foreground_process_group =
                terminal.read().controller.as_ref().and_then(|terminal_controller| {
                    terminal_controller.get_foreground_process_group()
                });
            if let Some(process_group) = foreground_process_group {
                process_group.send_signals(locked, &[SIGWINCH]);
            }
            Ok(SUCCESS)
        }
        TCGETA => {
            let termio = into_termio(*terminal.read().termios());
            current_task.write_object(UserRef::<uapi::termio>::new(user_addr), &termio)?;
            Ok(SUCCESS)
        }
        TCGETS => {
            // N.B. TCGETS on the main terminal actually returns the configuration of the replica
            // end.
            current_task.write_object(
                UserRef::<uapi::termios>::new(user_addr),
                terminal.read().termios(),
            )?;
            Ok(SUCCESS)
        }
        TCSETA => {
            let termio = current_task.read_object(UserRef::<uapi::termio>::new(user_addr))?;
            terminal.set_termios(locked, into_termios(termio));
            Ok(SUCCESS)
        }
        TCSETS => {
            // N.B. TCSETS on the main terminal actually affects the configuration of the replica
            // end.
            let termios = current_task.read_object(UserRef::<uapi::termios>::new(user_addr))?;
            terminal.set_termios(locked, termios);
            Ok(SUCCESS)
        }
        TCSETAF => {
            // This should drain the output queue and discard the pending input first.
            let termio = current_task.read_object(UserRef::<uapi::termio>::new(user_addr))?;
            terminal.set_termios(locked, into_termios(termio));
            Ok(SUCCESS)
        }
        TCSETSF => {
            // This should drain the output queue and discard the pending input first.
            let termios = current_task.read_object(UserRef::<uapi::termios>::new(user_addr))?;
            terminal.set_termios(locked, termios);
            Ok(SUCCESS)
        }
        TCSETAW => {
            track_stub!(TODO("https://fxbug.dev/322873281"), "TCSETAW drain output queue first");
            let termio = current_task.read_object(UserRef::<uapi::termio>::new(user_addr))?;
            terminal.set_termios(locked, into_termios(termio));
            Ok(SUCCESS)
        }
        TCSETSW => {
            track_stub!(TODO("https://fxbug.dev/322873281"), "TCSETSW drain output queue first");
            let termios = current_task.read_object(UserRef::<uapi::termios>::new(user_addr))?;
            terminal.set_termios(locked, termios);
            Ok(SUCCESS)
        }
        TIOCSETD => {
            track_stub!(
                TODO("https://fxbug.dev/322874060"),
                "devpts setting line discipline",
                is_main
            );
            error!(EINVAL)
        }
        TCSBRK => Ok(SUCCESS),
        TCXONC => {
            track_stub!(TODO("https://fxbug.dev/322892912"), "devpts ioctl TCXONC", is_main);
            error!(ENOSYS)
        }
        TCFLSH => {
            track_stub!(TODO("https://fxbug.dev/322893703"), "devpts ioctl TCFLSH", is_main);
            error!(ENOSYS)
        }
        TIOCEXCL => {
            track_stub!(TODO("https://fxbug.dev/322893449"), "devpts ioctl TIOCEXCL", is_main);
            error!(ENOSYS)
        }
        TIOCNXCL => {
            track_stub!(TODO("https://fxbug.dev/322893393"), "devpts ioctl TIOCNXCL", is_main);
            error!(ENOSYS)
        }
        TIOCOUTQ => {
            track_stub!(TODO("https://fxbug.dev/322893723"), "devpts ioctl TIOCOUTQ", is_main);
            error!(ENOSYS)
        }
        TIOCSTI => {
            track_stub!(TODO("https://fxbug.dev/322893780"), "devpts ioctl TIOCSTI", is_main);
            error!(ENOSYS)
        }
        TIOCMGET => {
            track_stub!(TODO("https://fxbug.dev/322893681"), "devpts ioctl TIOCMGET", is_main);
            error!(ENOSYS)
        }
        TIOCMBIS => {
            track_stub!(TODO("https://fxbug.dev/322893709"), "devpts ioctl TIOCMBIS", is_main);
            error!(ENOSYS)
        }
        TIOCMBIC => {
            track_stub!(TODO("https://fxbug.dev/322893610"), "devpts ioctl TIOCMBIC", is_main);
            error!(ENOSYS)
        }
        TIOCMSET => {
            track_stub!(TODO("https://fxbug.dev/322893211"), "devpts ioctl TIOCMSET", is_main);
            error!(ENOSYS)
        }
        TIOCGSOFTCAR => {
            track_stub!(TODO("https://fxbug.dev/322893365"), "devpts ioctl TIOCGSOFTCAR", is_main);
            error!(ENOSYS)
        }
        TIOCSSOFTCAR => {
            track_stub!(TODO("https://fxbug.dev/322894074"), "devpts ioctl TIOCSSOFTCAR", is_main);
            error!(ENOSYS)
        }
        TIOCLINUX => {
            track_stub!(TODO("https://fxbug.dev/322893147"), "devpts ioctl TIOCLINUX", is_main);
            error!(ENOSYS)
        }
        TIOCCONS => {
            track_stub!(TODO("https://fxbug.dev/322893267"), "devpts ioctl TIOCCONS", is_main);
            error!(ENOSYS)
        }
        TIOCGSERIAL => {
            track_stub!(TODO("https://fxbug.dev/322893503"), "devpts ioctl TIOCGSERIAL", is_main);
            error!(ENOSYS)
        }
        TIOCSSERIAL => {
            track_stub!(TODO("https://fxbug.dev/322893663"), "devpts ioctl TIOCSSERIAL", is_main);
            error!(ENOSYS)
        }
        TIOCPKT => {
            track_stub!(TODO("https://fxbug.dev/322893148"), "devpts ioctl TIOCPKT", is_main);
            error!(ENOSYS)
        }
        FIONBIO => {
            track_stub!(TODO("https://fxbug.dev/322893957"), "devpts ioctl FIONBIO", is_main);
            error!(ENOSYS)
        }
        TIOCGETD => {
            track_stub!(TODO("https://fxbug.dev/322893974"), "devpts ioctl TIOCGETD", is_main);
            error!(ENOSYS)
        }
        TCSBRKP => Ok(SUCCESS),
        TIOCSBRK => {
            track_stub!(TODO("https://fxbug.dev/322893936"), "devpts ioctl TIOCSBRK", is_main);
            error!(ENOSYS)
        }
        TIOCCBRK => {
            track_stub!(TODO("https://fxbug.dev/322893213"), "devpts ioctl TIOCCBRK", is_main);
            error!(ENOSYS)
        }
        TIOCGSID => {
            track_stub!(TODO("https://fxbug.dev/322894076"), "devpts ioctl TIOCGSID", is_main);
            error!(ENOSYS)
        }
        TIOCGRS485 => {
            track_stub!(TODO("https://fxbug.dev/322893728"), "devpts ioctl TIOCGRS485", is_main);
            error!(ENOSYS)
        }
        TIOCSRS485 => {
            track_stub!(TODO("https://fxbug.dev/322893783"), "devpts ioctl TIOCSRS485", is_main);
            error!(ENOSYS)
        }
        TCGETX => {
            track_stub!(TODO("https://fxbug.dev/322893327"), "devpts ioctl TCGETX", is_main);
            error!(ENOSYS)
        }
        TCSETX => {
            track_stub!(TODO("https://fxbug.dev/322893741"), "devpts ioctl TCSETX", is_main);
            error!(ENOSYS)
        }
        TCSETXF => {
            track_stub!(TODO("https://fxbug.dev/322893937"), "devpts ioctl TCSETXF", is_main);
            error!(ENOSYS)
        }
        TCSETXW => {
            track_stub!(TODO("https://fxbug.dev/322893899"), "devpts ioctl TCSETXW", is_main);
            error!(ENOSYS)
        }
        TIOCVHANGUP => {
            track_stub!(TODO("https://fxbug.dev/322893742"), "devpts ioctl TIOCVHANGUP", is_main);
            error!(ENOSYS)
        }
        FIONCLEX => {
            track_stub!(TODO("https://fxbug.dev/322893938"), "devpts ioctl FIONCLEX", is_main);
            error!(ENOSYS)
        }
        FIOCLEX => {
            track_stub!(TODO("https://fxbug.dev/322894214"), "devpts ioctl FIOCLEX", is_main);
            error!(ENOSYS)
        }
        FIOASYNC => {
            track_stub!(TODO("https://fxbug.dev/322893269"), "devpts ioctl FIOASYNC", is_main);
            error!(ENOSYS)
        }
        TIOCSERCONFIG => {
            track_stub!(TODO("https://fxbug.dev/322893881"), "devpts ioctl TIOCSERCONFIG", is_main);
            error!(ENOSYS)
        }
        TIOCSERGWILD => {
            track_stub!(TODO("https://fxbug.dev/322893686"), "devpts ioctl TIOCSERGWILD", is_main);
            error!(ENOSYS)
        }
        TIOCSERSWILD => {
            track_stub!(TODO("https://fxbug.dev/322893837"), "devpts ioctl TIOCSERSWILD", is_main);
            error!(ENOSYS)
        }
        TIOCGLCKTRMIOS => {
            track_stub!(
                TODO("https://fxbug.dev/322894114"),
                "devpts ioctl TIOCGLCKTRMIOS",
                is_main
            );
            error!(ENOSYS)
        }
        TIOCSLCKTRMIOS => {
            track_stub!(
                TODO("https://fxbug.dev/322893711"),
                "devpts ioctl TIOCSLCKTRMIOS",
                is_main
            );
            error!(ENOSYS)
        }
        TIOCSERGSTRUCT => {
            track_stub!(
                TODO("https://fxbug.dev/322893828"),
                "devpts ioctl TIOCSERGSTRUCT",
                is_main
            );
            error!(ENOSYS)
        }
        TIOCSERGETLSR => {
            track_stub!(TODO("https://fxbug.dev/322894083"), "devpts ioctl TIOCSERGETLSR", is_main);
            error!(ENOSYS)
        }
        TIOCSERGETMULTI => {
            track_stub!(
                TODO("https://fxbug.dev/322893962"),
                "devpts ioctl TIOCSERGETMULTI",
                is_main
            );
            error!(ENOSYS)
        }
        TIOCSERSETMULTI => {
            track_stub!(
                TODO("https://fxbug.dev/322893273"),
                "devpts ioctl TIOCSERSETMULTI",
                is_main
            );
            error!(ENOSYS)
        }
        TIOCMIWAIT => {
            track_stub!(TODO("https://fxbug.dev/322894005"), "devpts ioctl TIOCMIWAIT", is_main);
            error!(ENOSYS)
        }
        TIOCGICOUNT => {
            track_stub!(TODO("https://fxbug.dev/322893862"), "devpts ioctl TIOCGICOUNT", is_main);
            error!(ENOSYS)
        }
        FIOQSIZE => {
            track_stub!(TODO("https://fxbug.dev/322893770"), "devpts ioctl FIOQSIZE", is_main);
            error!(ENOSYS)
        }
        other => {
            track_stub!(TODO("https://fxbug.dev/322893712"), "devpts unknown ioctl", other);
            error!(ENOTTY)
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::fs::devpts::tty_device_init;
    use crate::fs::tmpfs::TmpFs;
    use crate::testing::*;
    use crate::vfs::buffers::{VecInputBuffer, VecOutputBuffer};
    use crate::vfs::fs_args::MountParams;
    use crate::vfs::{MountInfo, NamespaceNode};
    use starnix_uapi::auth::Credentials;
    use starnix_uapi::file_mode::{AccessCheck, FileMode};
    use starnix_uapi::signals::{SIGCHLD, SIGTTOU};

    fn new_pts_fs(locked: &mut Locked<Unlocked>, kernel: &Kernel) -> FileSystemHandle {
        let mut options = FileSystemOptions::default();
        options.params = MountParams::parse("ptmxmode=666".into()).expect("parse option");
        super::new_pts_fs(locked, &kernel, options).expect("create new_pts_fs")
    }

    fn ioctl<T: zerocopy::IntoBytes + zerocopy::FromBytes + zerocopy::Immutable + Copy>(
        locked: &mut Locked<Unlocked>,
        current_task: &CurrentTask,
        file: &FileHandle,
        command: u32,
        value: &T,
    ) -> Result<T, Errno> {
        let address = map_memory(
            locked,
            current_task,
            UserAddress::default(),
            std::mem::size_of::<T>() as u64,
        );
        let address_ref = UserRef::<T>::new(address);
        current_task.write_object(address_ref, value)?;
        file.ioctl(locked, current_task, command, address.into())?;
        current_task.read_object(address_ref)
    }

    fn set_controlling_terminal(
        locked: &mut Locked<Unlocked>,
        current_task: &CurrentTask,
        file: &FileHandle,
        steal: bool,
    ) -> Result<SyscallResult, Errno> {
        #[allow(clippy::bool_to_int_with_if)]
        file.ioctl(locked, current_task, TIOCSCTTY, steal.into())
    }

    fn lookup_node<L>(
        locked: &mut Locked<L>,
        task: &CurrentTask,
        fs: &FileSystemHandle,
        name: &FsStr,
    ) -> Result<NamespaceNode, Errno>
    where
        L: LockEqualOrBefore<FileOpsCore>,
    {
        let root = NamespaceNode::new_anonymous(fs.root().clone());
        root.lookup_child(locked, task, &mut Default::default(), name)
    }

    fn open_file_with_flags(
        locked: &mut Locked<Unlocked>,
        current_task: &CurrentTask,
        fs: &FileSystemHandle,
        name: &FsStr,
        flags: OpenFlags,
    ) -> Result<FileHandle, Errno> {
        let node = lookup_node(locked, current_task, fs, name)?;
        node.open(locked, current_task, flags, AccessCheck::default())
    }

    fn open_file(
        locked: &mut Locked<Unlocked>,
        current_task: &CurrentTask,
        fs: &FileSystemHandle,
        name: &FsStr,
    ) -> Result<FileHandle, Errno> {
        open_file_with_flags(locked, current_task, fs, name, OpenFlags::RDWR | OpenFlags::NOCTTY)
    }

    fn open_ptmx_and_unlock(
        locked: &mut Locked<Unlocked>,
        current_task: &CurrentTask,
        fs: &FileSystemHandle,
    ) -> Result<FileHandle, Errno> {
        let file = open_file_with_flags(locked, current_task, fs, "ptmx".into(), OpenFlags::RDWR)?;

        // Unlock terminal
        ioctl::<i32>(locked, current_task, &file, TIOCSPTLCK, &0)?;

        Ok(file)
    }

    #[fuchsia::test]
    async fn opening_ptmx_creates_pts() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            lookup_node(locked, task, &fs, "0".into()).unwrap_err();
            let _ptmx = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            lookup_node(locked, task, &fs, "0".into()).expect("pty");
        })
        .await;
    }

    #[fuchsia::test]
    async fn closing_ptmx_closes_pts() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            lookup_node(locked, task, &fs, "0".into()).unwrap_err();
            let ptmx = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            let _pts = open_file(locked, task, &fs, "0".into()).expect("open file");
            std::mem::drop(ptmx);
            task.trigger_delayed_releaser(locked);
            lookup_node(locked, task, &fs, "0".into()).unwrap_err();
        })
        .await;
    }

    #[fuchsia::test]
    async fn pts_are_reused() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);

            let _ptmx0 = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            let mut _ptmx1 = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            let _ptmx2 = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");

            lookup_node(locked, task, &fs, "0".into()).expect("component_lookup");
            lookup_node(locked, task, &fs, "1".into()).expect("component_lookup");
            lookup_node(locked, task, &fs, "2".into()).expect("component_lookup");

            std::mem::drop(_ptmx1);
            task.trigger_delayed_releaser(locked);

            lookup_node(locked, task, &fs, "1".into()).unwrap_err();

            _ptmx1 = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            lookup_node(locked, task, &fs, "1".into()).expect("component_lookup");
        })
        .await;
    }

    #[fuchsia::test]
    async fn opening_inexistant_replica_fails() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            // Initialize pts devices
            new_pts_fs(locked, kernel);
            let fs = TmpFs::new_fs(locked, kernel);
            let mount = MountInfo::detached();
            let pts = fs
                .root()
                .create_entry(
                    locked,
                    task,
                    &mount,
                    "custom_pts".into(),
                    |locked, dir, mount, name| {
                        dir.create_node(
                            locked,
                            task,
                            mount,
                            name,
                            mode!(IFCHR, 0o666),
                            DeviceType::new(DEVPTS_FIRST_MAJOR, 0),
                            FsCred::root(),
                        )
                    },
                )
                .expect("custom_pts");
            let node = NamespaceNode::new_anonymous(pts.clone());
            assert!(node.open(locked, task, OpenFlags::RDONLY, AccessCheck::skip()).is_err());
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_open_tty() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            let devfs = crate::fs::devtmpfs::DevTmpFs::from_kernel(locked, kernel);

            let ptmx = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            set_controlling_terminal(locked, task, &ptmx, false).expect("set_controlling_terminal");
            let tty = open_file_with_flags(locked, task, &devfs, "tty".into(), OpenFlags::RDWR)
                .expect("tty");
            // Check that tty is the main terminal by calling the ioctl TIOCGPTN and checking it is
            // has the same result as on ptmx.
            assert_eq!(
                ioctl::<i32>(locked, task, &tty, TIOCGPTN, &0),
                ioctl::<i32>(locked, task, &ptmx, TIOCGPTN, &0)
            );

            // Detach the controlling terminal.
            ioctl::<i32>(locked, task, &ptmx, TIOCNOTTY, &0).expect("detach terminal");
            let pts = open_file(locked, task, &fs, "0".into()).expect("open file");
            set_controlling_terminal(locked, task, &pts, false).expect("set_controlling_terminal");
            let tty = open_file_with_flags(locked, task, &devfs, "tty".into(), OpenFlags::RDWR)
                .expect("tty");
            // TIOCGPTN is not implemented on replica terminals
            assert!(ioctl::<i32>(locked, task, &tty, TIOCGPTN, &0).is_err());
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_unknown_ioctl() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);

            let ptmx = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            assert_eq!(ptmx.ioctl(locked, task, 42, Default::default()), error!(ENOTTY));

            let pts_file = open_file(locked, task, &fs, "0".into()).expect("open file");
            assert_eq!(pts_file.ioctl(locked, task, 42, Default::default()), error!(ENOTTY));
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_tiocgptn_ioctl() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            let ptmx0 = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            let ptmx1 = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");

            let pts0 = ioctl::<u32>(locked, task, &ptmx0, TIOCGPTN, &0).expect("ioctl");
            assert_eq!(pts0, 0);

            let pts1 = ioctl::<u32>(locked, task, &ptmx1, TIOCGPTN, &0).expect("ioctl");
            assert_eq!(pts1, 1);
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_new_terminal_is_locked() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            let _ptmx_file = open_file(locked, task, &fs, "ptmx".into()).expect("open file");

            let pts = lookup_node(locked, task, &fs, "0".into()).expect("component_lookup");
            assert_eq!(
                pts.open(locked, task, OpenFlags::RDONLY, AccessCheck::default()).map(|_| ()),
                error!(EIO)
            );
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_lock_ioctls() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            let ptmx = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            let pts = lookup_node(locked, task, &fs, "0".into()).expect("component_lookup");

            // Check that the lock is not set.
            assert_eq!(ioctl::<i32>(locked, task, &ptmx, TIOCGPTLCK, &0), Ok(0));
            // /dev/pts/0 can be opened
            pts.open(locked, task, OpenFlags::RDONLY, AccessCheck::default()).expect("open");

            // Lock the terminal
            ioctl::<i32>(locked, task, &ptmx, TIOCSPTLCK, &42).expect("ioctl");
            // Check that the lock is set.
            assert_eq!(ioctl::<i32>(locked, task, &ptmx, TIOCGPTLCK, &0), Ok(1));
            // /dev/pts/0 cannot be opened
            assert_eq!(
                pts.open(locked, task, OpenFlags::RDONLY, AccessCheck::default()).map(|_| ()),
                error!(EIO)
            );
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_ptmx_stats() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            task.set_creds(Credentials::with_ids(22, 22));
            let fs = new_pts_fs(locked, kernel);
            let ptmx = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            let ptmx_stat = ptmx.node().stat(locked, task).expect("stat");
            assert_eq!(ptmx_stat.st_blksize as usize, BLOCK_SIZE);
            let pts = open_file(locked, task, &fs, "0".into()).expect("open file");
            let pts_stats = pts.node().stat(locked, task).expect("stat");
            assert_eq!(pts_stats.st_mode & FileMode::PERMISSIONS.bits(), 0o600);
            assert_eq!(pts_stats.st_uid, 22);
            // TODO(qsr): Check that gid is tty.
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_attach_terminal_when_open() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            let _opened_main = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            // Opening the main terminal should not set the terminal of the session.
            assert!(
                task.thread_group()
                    .read()
                    .process_group
                    .session
                    .read()
                    .controlling_terminal
                    .is_none()
            );
            // Opening the terminal should not set the terminal of the session with the NOCTTY flag.
            let _opened_replica2 = open_file_with_flags(
                locked,
                task,
                &fs,
                "0".into(),
                OpenFlags::RDWR | OpenFlags::NOCTTY,
            )
            .expect("open file");
            assert!(
                task.thread_group()
                    .read()
                    .process_group
                    .session
                    .read()
                    .controlling_terminal
                    .is_none()
            );

            // Opening the replica terminal should set the terminal of the session.
            let _opened_replica2 =
                open_file_with_flags(locked, task, &fs, "0".into(), OpenFlags::RDWR)
                    .expect("open file");
            assert!(
                task.thread_group()
                    .read()
                    .process_group
                    .session
                    .read()
                    .controlling_terminal
                    .is_some()
            );
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_attach_terminal() {
        spawn_kernel_and_run(async |locked, task1| {
            let kernel = task1.kernel();
            tty_device_init(locked, &*task1).expect("tty_device_init");
            let task2 = task1.clone_task_for_test(locked, 0, Some(SIGCHLD));
            task2.thread_group().setsid(locked).expect("setsid");

            let fs = new_pts_fs(locked, kernel);
            let opened_main = open_ptmx_and_unlock(locked, task1, &fs).expect("ptmx");
            let opened_replica = open_file(locked, &task2, &fs, "0".into()).expect("open file");

            assert_eq!(ioctl::<i32>(locked, task1, &opened_main, TIOCGPGRP, &0), error!(ENOTTY));
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCGPGRP, &0),
                error!(ENOTTY)
            );

            set_controlling_terminal(locked, task1, &opened_main, false).unwrap();
            assert_eq!(
                ioctl::<i32>(locked, task1, &opened_main, TIOCGPGRP, &0),
                Ok(task1.thread_group().read().process_group.leader)
            );
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCGPGRP, &0),
                error!(ENOTTY)
            );

            // Cannot steal terminal using the replica.
            assert_eq!(
                set_controlling_terminal(locked, &task2, &opened_replica, false),
                error!(EPERM)
            );
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCGPGRP, &0),
                error!(ENOTTY)
            );
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_steal_terminal() {
        spawn_kernel_and_run(async |locked, task1| {
            let kernel = task1.kernel();
            tty_device_init(locked, &*task1).expect("tty_device_init");
            task1.set_creds(Credentials::with_ids(1, 1));

            let task2 = task1.clone_task_for_test(locked, 0, Some(SIGCHLD));

            let fs = new_pts_fs(locked, kernel);
            let _opened_main = open_ptmx_and_unlock(locked, task1, &fs).expect("ptmx");
            let wo_opened_replica = open_file_with_flags(
                locked,
                task1,
                &fs,
                "0".into(),
                OpenFlags::WRONLY | OpenFlags::NOCTTY,
            )
            .expect("open file");
            assert!(!wo_opened_replica.can_read());

            // FD must be readable for setting the terminal.
            assert_eq!(
                set_controlling_terminal(locked, task1, &wo_opened_replica, false),
                error!(EPERM)
            );

            let opened_replica = open_file(locked, &task2, &fs, "0".into()).expect("open file");
            // Task must be session leader for setting the terminal.
            assert_eq!(
                set_controlling_terminal(locked, &task2, &opened_replica, false),
                error!(EINVAL)
            );

            // Associate terminal to task1.
            set_controlling_terminal(locked, task1, &opened_replica, false)
                .expect("Associate terminal to task1");

            // One cannot associate a terminal to a process that has already one
            assert_eq!(
                set_controlling_terminal(locked, task1, &opened_replica, false),
                error!(EINVAL)
            );

            task2.thread_group().setsid(locked).expect("setsid");

            // One cannot associate a terminal that is already associated with another process.
            assert_eq!(
                set_controlling_terminal(locked, &task2, &opened_replica, false),
                error!(EPERM)
            );

            // One cannot steal a terminal without the CAP_SYS_ADMIN capacility
            assert_eq!(
                set_controlling_terminal(locked, &task2, &opened_replica, true),
                error!(EPERM)
            );

            // One can steal a terminal with the CAP_SYS_ADMIN capacility
            task2.set_creds(Credentials::with_ids(0, 0));
            // But not without specifying that one wants to steal it.
            assert_eq!(
                set_controlling_terminal(locked, &task2, &opened_replica, false),
                error!(EPERM)
            );
            set_controlling_terminal(locked, &task2, &opened_replica, true)
                .expect("Associate terminal to task2");

            assert!(
                task1
                    .thread_group()
                    .read()
                    .process_group
                    .session
                    .read()
                    .controlling_terminal
                    .is_none()
            );
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_set_foreground_process() {
        spawn_kernel_and_run(async |locked, init| {
            let kernel = init.kernel();
            tty_device_init(locked, &*init).expect("tty_device_init");
            let task1 = init.clone_task_for_test(locked, 0, Some(SIGCHLD));
            task1.thread_group().setsid(locked).expect("setsid");
            let task2 = task1.clone_task_for_test(locked, 0, Some(SIGCHLD));
            task2.thread_group().setpgid(locked, &task2, &task2, 0).expect("setpgid");
            let task2_pgid = task2.thread_group().read().process_group.leader;

            assert_ne!(task2_pgid, task1.thread_group().read().process_group.leader);

            let fs = new_pts_fs(locked, kernel);
            let _opened_main = open_ptmx_and_unlock(locked, init, &fs).expect("ptmx");
            let opened_replica = open_file(locked, &task2, &fs, "0".into()).expect("open file");

            // Cannot change the foreground process group if the terminal is not the controlling
            // terminal
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCSPGRP, &task2_pgid),
                error!(ENOTTY)
            );

            // Attach terminal to task1 and task2 session.
            set_controlling_terminal(locked, &task1, &opened_replica, false).unwrap();
            // The foreground process group should be the one of task1
            assert_eq!(
                ioctl::<i32>(locked, &task1, &opened_replica, TIOCGPGRP, &0),
                Ok(task1.thread_group().read().process_group.leader)
            );

            // Cannot change the foreground process group to a negative pid.
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCSPGRP, &-1),
                error!(EINVAL)
            );

            // Cannot change the foreground process group to a invalid process group.
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCSPGRP, &255),
                error!(ESRCH)
            );

            // Cannot change the foreground process group to a process group in another session.
            let init_pgid = init.thread_group().read().process_group.leader;
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCSPGRP, &init_pgid),
                error!(EPERM)
            );

            // Changing the foreground process while being in background generates SIGTTOU and fails.
            assert_eq!(
                ioctl::<i32>(locked, &task2, &opened_replica, TIOCSPGRP, &task2_pgid),
                error!(EINTR)
            );
            assert!(task2.read().has_signal_pending(SIGTTOU));

            // Set the foreground process to task2 process group
            ioctl::<i32>(locked, &task1, &opened_replica, TIOCSPGRP, &task2_pgid).unwrap();

            // Check that the foreground process has been changed.
            let terminal = Arc::clone(
                &task1
                    .thread_group()
                    .read()
                    .process_group
                    .session
                    .read()
                    .controlling_terminal
                    .as_ref()
                    .unwrap()
                    .terminal,
            );
            assert_eq!(
                terminal
                    .read()
                    .controller
                    .as_ref()
                    .unwrap()
                    .session
                    .upgrade()
                    .unwrap()
                    .read()
                    .get_foreground_process_group_leader(),
                task2_pgid
            );
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_detach_session() {
        spawn_kernel_and_run(async |locked, task1| {
            let kernel = task1.kernel();
            tty_device_init(locked, &*task1).expect("tty_device_init");
            let task2 = task1.clone_task_for_test(locked, 0, Some(SIGCHLD));
            task2.thread_group().setsid(locked).expect("setsid");

            let fs = new_pts_fs(locked, kernel);
            let _opened_main = open_ptmx_and_unlock(locked, task1, &fs).expect("ptmx");
            let opened_replica = open_file(locked, task1, &fs, "0".into()).expect("open file");

            // Cannot detach the controlling terminal when none is attached terminal
            assert_eq!(ioctl::<i32>(locked, task1, &opened_replica, TIOCNOTTY, &0), error!(ENOTTY));

            set_controlling_terminal(locked, &task2, &opened_replica, false)
                .expect("set controlling terminal");

            // Cannot detach the controlling terminal when not the session leader.
            assert_eq!(ioctl::<i32>(locked, task1, &opened_replica, TIOCNOTTY, &0), error!(ENOTTY));

            // Detach the terminal
            ioctl::<i32>(locked, &task2, &opened_replica, TIOCNOTTY, &0).expect("detach terminal");
            assert!(
                task2
                    .thread_group()
                    .read()
                    .process_group
                    .session
                    .read()
                    .controlling_terminal
                    .is_none()
            );
        })
        .await;
    }

    #[fuchsia::test]
    async fn test_send_data_back_and_forth() {
        spawn_kernel_and_run(async |locked, task| {
            let kernel = task.kernel();
            tty_device_init(locked, &*task).expect("tty_device_init");
            let fs = new_pts_fs(locked, kernel);
            let ptmx = open_ptmx_and_unlock(locked, task, &fs).expect("ptmx");
            let pts = open_file(locked, task, &fs, "0".into()).expect("open file");

            let has_data_ready_to_read = |locked: &mut Locked<Unlocked>, fd: &FileHandle| {
                fd.query_events(locked, task).expect("query_events").contains(FdEvents::POLLIN)
            };

            let write_and_assert = |locked: &mut Locked<Unlocked>, fd: &FileHandle, data: &[u8]| {
                assert_eq!(
                    fd.write(locked, task, &mut VecInputBuffer::new(data)).expect("write"),
                    data.len()
                );
            };

            let read_and_check = |locked: &mut Locked<Unlocked>, fd: &FileHandle, data: &[u8]| {
                assert!(has_data_ready_to_read(locked, fd));
                let mut buffer = VecOutputBuffer::new(data.len() + 1);
                assert_eq!(fd.read(locked, task, &mut buffer).expect("read"), data.len());
                assert_eq!(data, buffer.data());
            };

            let hello_buffer = b"hello\n";
            let hello_transformed_buffer = b"hello\r\n";

            // Main to replica
            write_and_assert(locked, &ptmx, hello_buffer);
            read_and_check(locked, &pts, hello_buffer);

            // Data has been echoed
            read_and_check(locked, &ptmx, hello_transformed_buffer);

            // Replica to main
            write_and_assert(locked, &pts, hello_buffer);
            read_and_check(locked, &ptmx, hello_transformed_buffer);

            // Data has not been echoed
            assert!(!has_data_ready_to_read(locked, &pts));
        })
        .await;
    }
}