rustix/
pty.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
//! Pseudoterminal operations.
//!
//! For the `openpty` and `login_tty` functions, see the
//! [rustix-openpty crate].
//!
//! [rustix-openpty crate]: https://crates.io/crates/rustix-openpty

#![allow(unsafe_code)]

use crate::backend::c;
use crate::fd::{AsFd, OwnedFd};
use crate::fs::OFlags;
use crate::{backend, io};
#[cfg(all(
    feature = "alloc",
    any(
        apple,
        linux_like,
        target_os = "freebsd",
        target_os = "fuchsia",
        target_os = "illumos"
    )
))]
use {crate::ffi::CString, alloc::vec::Vec};

#[cfg(target_os = "linux")]
use crate::{fd::FromRawFd, ioctl};

bitflags::bitflags! {
    /// `O_*` flags for use with [`openpt`] and [`ioctl_tiocgptpeer`].
    ///
    /// [`ioctl_tiocgptpeer`]: https://docs.rs/rustix/*/x86_64-unknown-linux-gnu/rustix/pty/fn.ioctl_tiocgptpeer.html
    #[repr(transparent)]
    #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
    pub struct OpenptFlags: u32 {
        /// `O_RDWR`
        const RDWR = c::O_RDWR as c::c_uint;

        /// `O_NOCTTY`
        #[cfg(not(any(target_os = "espidf", target_os = "l4re", target_os = "redox", target_os = "vita")))]
        const NOCTTY = c::O_NOCTTY as c::c_uint;

        /// `O_CLOEXEC`
        ///
        /// The standard `posix_openpt` function doesn't support `CLOEXEC`, but
        /// rustix supports it on Linux, and FreeBSD and NetBSD support it.
        #[cfg(any(linux_kernel, target_os = "freebsd", target_os = "netbsd"))]
        const CLOEXEC = c::O_CLOEXEC as c::c_uint;

        /// <https://docs.rs/bitflags/*/bitflags/#externally-defined-flags>
        const _ = !0;
    }
}

impl From<OpenptFlags> for OFlags {
    #[inline]
    fn from(flags: OpenptFlags) -> Self {
        // `OpenptFlags` is a subset of `OFlags`.
        Self::from_bits_retain(flags.bits() as _)
    }
}

/// `posix_openpt(flags)`—Open a pseudoterminal device.
///
/// On Linux, an additional `CLOEXEC` flag value may be passed to request the
/// close-on-exec flag be set.
///
/// On Linux, if the system has no free pseudoterminals available, the
/// underlying system call fails with [`io::Errno::NOSPC`], however this rustix
/// function translates that to [`io::Errno::AGAIN`], so that the linux_raw and
/// libc backends have the same behavior.
///
/// # References
///  - [POSIX]
///  - [Linux]
///  - [Apple]
///  - [FreeBSD]
///  - [DragonFly BSD]
///  - [NetBSD]
///  - [OpenBSD]
///  - [illumos]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/posix_openpt.html
/// [Linux]: https://man7.org/linux/man-pages/man3/posix_openpt.3.html
/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/posix_openpt.3.html
/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=posix_openpt&sektion=2
/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=posix_openpt&section=3
/// [NetBSD]: https://man.netbsd.org/posix_openpt.3
/// [OpenBSD]: https://man.openbsd.org/posix_openpt
/// [illumos]: https://illumos.org/man/3C/posix_openpt
#[inline]
#[doc(alias = "posix_openpt")]
pub fn openpt(flags: OpenptFlags) -> io::Result<OwnedFd> {
    // On Linux, open the device ourselves so that we can support `CLOEXEC`.
    #[cfg(linux_kernel)]
    {
        use crate::fs::{open, Mode};
        match open(cstr!("/dev/ptmx"), flags.into(), Mode::empty()) {
            // Match libc `openat` behavior with `ENOSPC`.
            Err(io::Errno::NOSPC) => Err(io::Errno::AGAIN),
            otherwise => otherwise,
        }
    }

    // On all other platforms, use `openpt`.
    #[cfg(not(linux_kernel))]
    {
        backend::pty::syscalls::openpt(flags)
    }
}

/// `ptsname(fd)`—Return the name of a pseudoterminal.
///
/// # References
///  - [POSIX]
///  - [Linux]
///  - [illumos]
///  - [glibc]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/ptsname.html
/// [Linux]: https://man7.org/linux/man-pages/man3/ptsname.3.html
/// [illumos]: https://www.illumos.org/man/3C/ptsname
/// [glibc]: https://sourceware.org/glibc/manual/latest/html_node/Allocation.html#index-ptsname
#[cfg(all(
    feature = "alloc",
    any(
        apple,
        linux_like,
        target_os = "freebsd",
        target_os = "fuchsia",
        target_os = "illumos"
    )
))]
#[inline]
#[doc(alias = "ptsname_r")]
pub fn ptsname<Fd: AsFd, B: Into<Vec<u8>>>(fd: Fd, reuse: B) -> io::Result<CString> {
    backend::pty::syscalls::ptsname(fd.as_fd(), reuse.into())
}

/// `unlockpt(fd)`—Unlock a pseudoterminal.
///
/// # References
///  - [POSIX]
///  - [Linux]
///  - [glibc]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/unlockpt.html
/// [Linux]: https://man7.org/linux/man-pages/man3/unlockpt.3.html
/// [glibc]: https://sourceware.org/glibc/manual/latest/html_node/Allocation.html#index-unlockpt
#[inline]
pub fn unlockpt<Fd: AsFd>(fd: Fd) -> io::Result<()> {
    backend::pty::syscalls::unlockpt(fd.as_fd())
}

/// `grantpt(fd)`—Grant access to the user side of a pseudoterminal.
///
/// On Linux, calling this function has no effect, as the kernel is expected to
/// grant the appropriate access. On all other platforms, this function has
/// unspecified behavior if the calling process has a [`Signal::Child`] signal
/// handler installed.
///
/// # References
///  - [POSIX]
///  - [Linux]
///  - [glibc]
///
/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/grantpt.html
/// [Linux]: https://man7.org/linux/man-pages/man3/grantpt.3.html
/// [glibc]: https://sourceware.org/glibc/manual/latest/html_node/Allocation.html#index-grantpt
/// [`Signal::Child`]: crate::process::Signal::Child
#[inline]
pub fn grantpt<Fd: AsFd>(fd: Fd) -> io::Result<()> {
    #[cfg(not(linux_kernel))]
    {
        backend::pty::syscalls::grantpt(fd.as_fd())
    }

    // On Linux, we assume the kernel has already granted the needed
    // permissions to the user side of the pseudoterminal.
    #[cfg(linux_kernel)]
    {
        let _ = fd;
        Ok(())
    }
}

/// `ioctl(fd, TIOCGPTPEER)`—Open the user side of a pseudoterminal.
///
/// This function is currently only implemented on Linux.
///
/// # References
///  - [Linux]
///
/// [Linux]: https://man7.org/linux/man-pages/man2/ioctl_tty.2.html
#[cfg(target_os = "linux")]
#[inline]
pub fn ioctl_tiocgptpeer<Fd: AsFd>(fd: Fd, flags: OpenptFlags) -> io::Result<OwnedFd> {
    unsafe { ioctl::ioctl(fd, Tiocgptpeer(flags)) }
}

#[cfg(target_os = "linux")]
struct Tiocgptpeer(OpenptFlags);

#[cfg(target_os = "linux")]
unsafe impl ioctl::Ioctl for Tiocgptpeer {
    type Output = OwnedFd;

    const IS_MUTATING: bool = false;
    const OPCODE: ioctl::Opcode = ioctl::Opcode::old(c::TIOCGPTPEER as ioctl::RawOpcode);

    fn as_ptr(&mut self) -> *mut c::c_void {
        self.0.bits() as *mut c::c_void
    }

    unsafe fn output_from_ptr(
        ret: ioctl::IoctlOutput,
        _arg: *mut c::c_void,
    ) -> io::Result<Self::Output> {
        Ok(OwnedFd::from_raw_fd(ret))
    }
}