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Work around missing TCGETS2/TCSETS2 on WSL.
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WSL appears to be lacking support for `TCGETS2` and `TCSETS2`, so teach
rustix's `tcgetattr` and `tcsetattr` how to fall back to `TCGETS` and
`TCSETS` as needed.

This approach preserves rustix's ability to support arbitrary speed values,
while falling back as needed to support WSL.

This is expected to fix crossterm-rs/crossterm#912.
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@sunfishcode
sunfishcode committed Aug 28, 2024
1 parent 629de02 commit 1bb5a13
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Showing 4 changed files with 255 additions and 79 deletions.
173 changes: 132 additions & 41 deletions src/backend/libc/termios/syscalls.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,8 @@ use crate::ffi::CStr;
)
))]
use core::mem::MaybeUninit;
#[cfg(linux_kernel)]
use core::sync::atomic::{AtomicBool, Ordering};
#[cfg(not(target_os = "wasi"))]
use {crate::io, crate::pid::Pid};
#[cfg(not(any(target_os = "espidf", target_os = "wasi")))]
Expand All @@ -28,6 +30,10 @@ use {
crate::utils::as_mut_ptr,
};

/// Is `TCGETS2` known to be available?
#[cfg(linux_kernel)]
static TCGETS2_KNOWN: AtomicBool = AtomicBool::new(false);

#[cfg(not(any(target_os = "espidf", target_os = "wasi")))]
pub(crate) fn tcgetattr(fd: BorrowedFd<'_>) -> io::Result<Termios> {
// If we have `TCGETS2`, use it, so that we fill in the `c_ispeed` and
Expand All @@ -38,7 +44,7 @@ pub(crate) fn tcgetattr(fd: BorrowedFd<'_>) -> io::Result<Termios> {
use crate::utils::default_array;

let termios2 = unsafe {
let mut termios2 = MaybeUninit::<c::termios2>::uninit();
let mut termios2 = MaybeUninit::<termios2>::uninit();

// QEMU's `TCGETS2` doesn't currently set `input_speed` or
// `output_speed` on PowerPC, so zero out the fields ourselves.
Expand All @@ -47,11 +53,26 @@ pub(crate) fn tcgetattr(fd: BorrowedFd<'_>) -> io::Result<Termios> {
termios2.write(core::mem::zeroed());
}

ret(c::ioctl(
let res = ret(c::ioctl(
borrowed_fd(fd),
c::TCGETS2 as _,
termios2.as_mut_ptr(),
))?;
));
match res {
Ok(()) => TCGETS2_KNOWN.store(true, Ordering::Relaxed),
Err(io::Errno::NOTTY) => tcgetattr_fallback(fd, &mut termios2)?,
Err(err) => {
TCGETS2_KNOWN.store(true, Ordering::Relaxed);
return Err(err);
}
}

// QEMU's `TCGETS2` doesn't currently set `input_speed` or
// `output_speed` on PowerPC, so set them manually if we can.
#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
{
infer_input_output_speed(termios2.assume_init_mut())
}

termios2.assume_init()
};
Expand All @@ -68,32 +89,6 @@ pub(crate) fn tcgetattr(fd: BorrowedFd<'_>) -> io::Result<Termios> {
output_speed: termios2.c_ospeed,
};

// QEMU's `TCGETS2` doesn't currently set `input_speed` or
// `output_speed` on PowerPC, so set them manually if we can.
#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
{
use crate::termios::speed;

if result.output_speed == 0 && (termios2.c_cflag & c::CBAUD) != c::BOTHER {
if let Some(output_speed) = speed::decode(termios2.c_cflag & c::CBAUD) {
result.output_speed = output_speed;
}
}
if result.input_speed == 0
&& ((termios2.c_cflag & c::CIBAUD) >> c::IBSHIFT) != c::BOTHER
{
// For input speeds, `B0` is special-cased to mean the input
// speed is the same as the output speed.
if ((termios2.c_cflag & c::CIBAUD) >> c::IBSHIFT) == c::B0 {
result.input_speed = result.output_speed;
} else if let Some(input_speed) =
speed::decode((termios2.c_cflag & c::CIBAUD) >> c::IBSHIFT)
{
result.input_speed = input_speed;
}
}
}

result.special_codes.0[..termios2.c_cc.len()].copy_from_slice(&termios2.c_cc);

Ok(result)
Expand All @@ -111,6 +106,65 @@ pub(crate) fn tcgetattr(fd: BorrowedFd<'_>) -> io::Result<Termios> {
}
}

/// Workaround for WSL where `TCGETS2` is unavailable.
#[cfg(linux_kernel)]
#[cold]
unsafe fn tcgetattr_fallback(
fd: BorrowedFd<'_>,
result: &mut MaybeUninit<termios2>,
) -> io::Result<()> {
// If we've already seen `TCGETS2` succeed or fail in a way other than
// `NOTTY`, then can trust a `NOTTY` error from it.
if TCGETS2_KNOWN.load(Ordering::Relaxed) {
return Err(io::Errno::NOTTY);
}

// Ensure that the `c_ispeed` and `c_ospeed` fields are initialized,
// because `TCGETS` won't write to them.
result.write(core::mem::zeroed());

let res = ret(c::ioctl(
borrowed_fd(fd),
c::TCGETS as _,
result.as_mut_ptr(),
));
match res {
Ok(()) => {
infer_input_output_speed(result.assume_init_mut());
Ok(())
}
Err(io::Errno::NOTTY) => Err(io::Errno::NOTTY),
Err(err) => {
TCGETS2_KNOWN.store(true, Ordering::Relaxed);
Err(err)
}
}
}

/// Fill in the `input_speed` and `output_speed` fields of `Termios` using
/// information available in other fields.
#[cfg(linux_kernel)]
#[cold]
fn infer_input_output_speed(result: &mut termios2) {
use crate::termios::speed;

if result.c_ospeed == 0 && (result.c_cflag & c::CBAUD) != c::BOTHER {
if let Some(output_speed) = speed::decode(result.c_cflag & c::CBAUD) {
result.c_ospeed = output_speed;
}
}
if result.c_ispeed == 0 && ((result.c_cflag & c::CIBAUD) >> c::IBSHIFT) != c::BOTHER {
// For input speeds, `B0` is special-cased to mean the input
// speed is the same as the output speed.
if ((result.c_cflag & c::CIBAUD) >> c::IBSHIFT) == c::B0 {
result.c_ispeed = result.c_ospeed;
} else if let Some(input_speed) = speed::decode((result.c_cflag & c::CIBAUD) >> c::IBSHIFT)
{
result.c_ispeed = input_speed;
}
}
}

#[cfg(not(target_os = "wasi"))]
pub(crate) fn tcgetpgrp(fd: BorrowedFd<'_>) -> io::Result<Pid> {
unsafe {
Expand All @@ -133,6 +187,22 @@ pub(crate) fn tcsetpgrp(fd: BorrowedFd<'_>, pid: Pid) -> io::Result<()> {
unsafe { ret(c::tcsetpgrp(borrowed_fd(fd), pid.as_raw_nonzero().get())) }
}

#[cfg(linux_kernel)]
use linux_raw_sys::general::termios2;

#[cfg(linux_kernel)]
#[cfg(not(any(target_arch = "sparc", target_arch = "sparc64")))]
use linux_raw_sys::ioctl::{TCSETS, TCSETS2};

// linux-raw-sys' ioctl-generation script for sparc isn't working yet,
// so as a temporary workaround, declare these manually.
#[cfg(linux_kernel)]
#[cfg(any(target_arch = "sparc", target_arch = "sparc64"))]
const TCSETS: u32 = 0x8024_5409;
#[cfg(linux_kernel)]
#[cfg(any(target_arch = "sparc", target_arch = "sparc64"))]
const TCSETS2: u32 = 0x802c_540d;

#[cfg(not(any(target_os = "espidf", target_os = "wasi")))]
pub(crate) fn tcsetattr(
fd: BorrowedFd<'_>,
Expand All @@ -145,17 +215,7 @@ pub(crate) fn tcsetattr(
{
use crate::termios::speed;
use crate::utils::default_array;
use linux_raw_sys::general::{termios2, BOTHER, CBAUD, IBSHIFT};

#[cfg(not(any(target_arch = "sparc", target_arch = "sparc64")))]
use linux_raw_sys::ioctl::{TCSETS, TCSETS2};

// linux-raw-sys' ioctl-generation script for sparc isn't working yet,
// so as a temporary workaround, declare these manually.
#[cfg(any(target_arch = "sparc", target_arch = "sparc64"))]
const TCSETS: u32 = 0x8024_5409;
#[cfg(any(target_arch = "sparc", target_arch = "sparc64"))]
const TCSETS2: u32 = 0x802c_540d;
use linux_raw_sys::general::{BOTHER, CBAUD, IBSHIFT};

// Translate from `optional_actions` into an ioctl request code. On
// MIPS, `optional_actions` already has `TCGETS` added to it.
Expand Down Expand Up @@ -194,7 +254,14 @@ pub(crate) fn tcsetattr(
.c_cc
.copy_from_slice(&termios.special_codes.0[..nccs]);

unsafe { ret(c::ioctl(borrowed_fd(fd), request as _, &termios2)) }
unsafe {
let res = ret(c::ioctl(borrowed_fd(fd), request as _, &termios2));
match res {
Ok(()) => Ok(()),
Err(io::Errno::NOTTY) => tcsetattr_fallback(fd, optional_actions, &termios2),
Err(err) => Err(err),
}
}
}

#[cfg(not(linux_kernel))]
Expand All @@ -207,6 +274,30 @@ pub(crate) fn tcsetattr(
}
}

/// Workaround for WSL where `TCSETS2` is unavailable.
#[cfg(linux_kernel)]
#[cold]
unsafe fn tcsetattr_fallback(
fd: BorrowedFd<'_>,
optional_actions: OptionalActions,
result: &termios2,
) -> io::Result<()> {
// Translate from `optional_actions` into an ioctl request code. On
// MIPS, `optional_actions` already has `TCGETS` added to it.
let request = if cfg!(any(
target_arch = "mips",
target_arch = "mips32r6",
target_arch = "mips64",
target_arch = "mips64r6"
)) {
optional_actions as u32
} else {
optional_actions as u32 + TCSETS
};

ret(c::ioctl(borrowed_fd(fd), request as _, result))
}

#[cfg(not(target_os = "wasi"))]
pub(crate) fn tcsendbreak(fd: BorrowedFd<'_>) -> io::Result<()> {
unsafe { ret(c::tcsendbreak(borrowed_fd(fd), 0)) }
Expand Down
2 changes: 1 addition & 1 deletion src/backend/linux_raw/c.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -190,7 +190,7 @@ pub(crate) use linux_raw_sys::{
VKILL, VLNEXT, VMIN, VQUIT, VREPRINT, VSTART, VSTOP, VSUSP, VSWTC, VT0, VT1, VTDLY, VTIME,
VWERASE, XCASE, XTABS,
},
ioctl::{TCGETS2, TCSETS2, TCSETSF2, TCSETSW2, TIOCEXCL, TIOCNXCL},
ioctl::{TCGETS, TCGETS2, TCSETS, TCSETS2, TCSETSF2, TCSETSW2, TIOCEXCL, TIOCNXCL},
};

// On MIPS, `TCSANOW` et al have `TCSETS` added to them, so we need it to
Expand Down
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