Vendor things

third-party/vendor/jobserver/src/unix.rs

@@ -0,0 +1,486 @@
+use libc::c_int;
+
+use crate::FromEnvErrorInner;
+use std::fs::{File, OpenOptions};
+use std::io::{self, Read, Write};
+use std::mem;
+use std::mem::MaybeUninit;
+use std::os::unix::prelude::*;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::ptr;
+use std::sync::{Arc, Once};
+use std::thread::{self, Builder, JoinHandle};
+use std::time::Duration;
+
+#[derive(Debug)]
+pub enum Client {
+    /// `--jobserver-auth=R,W`
+    Pipe { read: File, write: File },
+    /// `--jobserver-auth=fifo:PATH`
+    Fifo { file: File, path: PathBuf },
+}
+
+#[derive(Debug)]
+pub struct Acquired {
+    byte: u8,
+}
+
+impl Client {
+    pub fn new(mut limit: usize) -> io::Result<Client> {
+        let client = unsafe { Client::mk()? };
+
+        // I don't think the character written here matters, but I could be
+        // wrong!
+        const BUFFER: [u8; 128] = [b'|'; 128];
+
+        let mut write = client.write();
+
+        set_nonblocking(write.as_raw_fd(), true)?;
+
+        while limit > 0 {
+            let n = limit.min(BUFFER.len());
+
+            write.write_all(&BUFFER[..n])?;
+            limit -= n;
+        }
+
+        set_nonblocking(write.as_raw_fd(), false)?;
+
+        Ok(client)
+    }
+
+    unsafe fn mk() -> io::Result<Client> {
+        let mut pipes = [0; 2];
+
+        // Attempt atomically-create-with-cloexec if we can on Linux,
+        // detected by using the `syscall` function in `libc` to try to work
+        // with as many kernels/glibc implementations as possible.
+        #[cfg(target_os = "linux")]
+        {
+            use std::sync::atomic::{AtomicBool, Ordering};
+
+            static PIPE2_AVAILABLE: AtomicBool = AtomicBool::new(true);
+            if PIPE2_AVAILABLE.load(Ordering::SeqCst) {
+                match libc::syscall(libc::SYS_pipe2, pipes.as_mut_ptr(), libc::O_CLOEXEC) {
+                    -1 => {
+                        let err = io::Error::last_os_error();
+                        if err.raw_os_error() == Some(libc::ENOSYS) {
+                            PIPE2_AVAILABLE.store(false, Ordering::SeqCst);
+                        } else {
+                            return Err(err);
+                        }
+                    }
+                    _ => return Ok(Client::from_fds(pipes[0], pipes[1])),
+                }
+            }
+        }
+
+        cvt(libc::pipe(pipes.as_mut_ptr()))?;
+        drop(set_cloexec(pipes[0], true));
+        drop(set_cloexec(pipes[1], true));
+        Ok(Client::from_fds(pipes[0], pipes[1]))
+    }
+
+    pub(crate) unsafe fn open(s: &str, check_pipe: bool) -> Result<Client, FromEnvErrorInner> {
+        if let Some(client) = Self::from_fifo(s)? {
+            return Ok(client);
+        }
+        if let Some(client) = Self::from_pipe(s, check_pipe)? {
+            return Ok(client);
+        }
+        Err(FromEnvErrorInner::CannotParse(format!(
+            "expected `fifo:PATH` or `R,W`, found `{s}`"
+        )))
+    }
+
+    /// `--jobserver-auth=fifo:PATH`
+    fn from_fifo(s: &str) -> Result<Option<Client>, FromEnvErrorInner> {
+        let mut parts = s.splitn(2, ':');
+        if parts.next().unwrap() != "fifo" {
+            return Ok(None);
+        }
+        let path_str = parts.next().ok_or_else(|| {
+            FromEnvErrorInner::CannotParse("expected a path after `fifo:`".to_string())
+        })?;
+        let path = Path::new(path_str);
+        let file = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .open(path)
+            .map_err(|err| FromEnvErrorInner::CannotOpenPath(path_str.to_string(), err))?;
+        Ok(Some(Client::Fifo {
+            file,
+            path: path.into(),
+        }))
+    }
+
+    /// `--jobserver-auth=R,W`
+    unsafe fn from_pipe(s: &str, check_pipe: bool) -> Result<Option<Client>, FromEnvErrorInner> {
+        let mut parts = s.splitn(2, ',');
+        let read = parts.next().unwrap();
+        let write = match parts.next() {
+            Some(w) => w,
+            None => return Ok(None),
+        };
+        let read = read
+            .parse()
+            .map_err(|e| FromEnvErrorInner::CannotParse(format!("cannot parse `read` fd: {e}")))?;
+        let write = write
+            .parse()
+            .map_err(|e| FromEnvErrorInner::CannotParse(format!("cannot parse `write` fd: {e}")))?;
+
+        // If either or both of these file descriptors are negative,
+        // it means the jobserver is disabled for this process.
+        if read < 0 {
+            return Err(FromEnvErrorInner::NegativeFd(read));
+        }
+        if write < 0 {
+            return Err(FromEnvErrorInner::NegativeFd(write));
+        }
+
+        // Ok so we've got two integers that look like file descriptors, but
+        // for extra sanity checking let's see if they actually look like
+        // valid files and instances of a pipe if feature enabled before we
+        // return the client.
+        //
+        // If we're called from `make` *without* the leading + on our rule
+        // then we'll have `MAKEFLAGS` env vars but won't actually have
+        // access to the file descriptors.
+        //
+        // `NotAPipe` is a worse error, return it if it's reported for any of the two fds.
+        match (fd_check(read, check_pipe), fd_check(write, check_pipe)) {
+            (read_err @ Err(FromEnvErrorInner::NotAPipe(..)), _) => read_err?,
+            (_, write_err @ Err(FromEnvErrorInner::NotAPipe(..))) => write_err?,
+            (read_err, write_err) => {
+                read_err?;
+                write_err?;
+            }
+        }
+
+        drop(set_cloexec(read, true));
+        drop(set_cloexec(write, true));
+        Ok(Some(Client::from_fds(read, write)))
+    }
+
+    unsafe fn from_fds(read: c_int, write: c_int) -> Client {
+        Client::Pipe {
+            read: File::from_raw_fd(read),
+            write: File::from_raw_fd(write),
+        }
+    }
+
+    /// Gets the read end of our jobserver client.
+    fn read(&self) -> &File {
+        match self {
+            Client::Pipe { read, .. } => read,
+            Client::Fifo { file, .. } => file,
+        }
+    }
+
+    /// Gets the write end of our jobserver client.
+    fn write(&self) -> &File {
+        match self {
+            Client::Pipe { write, .. } => write,
+            Client::Fifo { file, .. } => file,
+        }
+    }
+
+    pub fn acquire(&self) -> io::Result<Acquired> {
+        // Ignore interrupts and keep trying if that happens
+        loop {
+            if let Some(token) = self.acquire_allow_interrupts()? {
+                return Ok(token);
+            }
+        }
+    }
+
+    /// Block waiting for a token, returning `None` if we're interrupted with
+    /// EINTR.
+    fn acquire_allow_interrupts(&self) -> io::Result<Option<Acquired>> {
+        // We don't actually know if the file descriptor here is set in
+        // blocking or nonblocking mode. AFAIK all released versions of
+        // `make` use blocking fds for the jobserver, but the unreleased
+        // version of `make` doesn't. In the unreleased version jobserver
+        // fds are set to nonblocking and combined with `pselect`
+        // internally.
+        //
+        // Here we try to be compatible with both strategies. We optimistically
+        // try to read from the file descriptor which then may block, return
+        // a token or indicate that polling is needed.
+        // Blocking reads (if possible) allows the kernel to be more selective
+        // about which readers to wake up when a token is written to the pipe.
+        //
+        // We use `poll` here to block this thread waiting for read
+        // readiness, and then afterwards we perform the `read` itself. If
+        // the `read` returns that it would block then we start over and try
+        // again.
+        //
+        // Also note that we explicitly don't handle EINTR here. That's used
+        // to shut us down, so we otherwise punt all errors upwards.
+        unsafe {
+            let mut fd: libc::pollfd = mem::zeroed();
+            let mut read = self.read();
+            fd.fd = read.as_raw_fd();
+            fd.events = libc::POLLIN;
+            loop {
+                let mut buf = [0];
+                match read.read(&mut buf) {
+                    Ok(1) => return Ok(Some(Acquired { byte: buf[0] })),
+                    Ok(_) => {
+                        return Err(io::Error::new(
+                            io::ErrorKind::Other,
+                            "early EOF on jobserver pipe",
+                        ));
+                    }
+                    Err(e) => match e.kind() {
+                        io::ErrorKind::WouldBlock => { /* fall through to polling */ }
+                        io::ErrorKind::Interrupted => return Ok(None),
+                        _ => return Err(e),
+                    },
+                }
+
+                loop {
+                    fd.revents = 0;
+                    if libc::poll(&mut fd, 1, -1) == -1 {
+                        let e = io::Error::last_os_error();
+                        return match e.kind() {
+                            io::ErrorKind::Interrupted => Ok(None),
+                            _ => Err(e),
+                        };
+                    }
+                    if fd.revents != 0 {
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+    pub fn release(&self, data: Option<&Acquired>) -> io::Result<()> {
+        // Note that the fd may be nonblocking but we're going to go ahead
+        // and assume that the writes here are always nonblocking (we can
+        // always quickly release a token). If that turns out to not be the
+        // case we'll get an error anyway!
+        let byte = data.map(|d| d.byte).unwrap_or(b'+');
+        match self.write().write(&[byte])? {
+            1 => Ok(()),
+            _ => Err(io::Error::new(
+                io::ErrorKind::Other,
+                "failed to write token back to jobserver",
+            )),
+        }
+    }
+
+    pub fn string_arg(&self) -> String {
+        match self {
+            Client::Pipe { read, write } => format!("{},{}", read.as_raw_fd(), write.as_raw_fd()),
+            Client::Fifo { path, .. } => format!("fifo:{}", path.to_str().unwrap()),
+        }
+    }
+
+    pub fn available(&self) -> io::Result<usize> {
+        let mut len = MaybeUninit::<c_int>::uninit();
+        cvt(unsafe { libc::ioctl(self.read().as_raw_fd(), libc::FIONREAD, len.as_mut_ptr()) })?;
+        Ok(unsafe { len.assume_init() } as usize)
+    }
+
+    pub fn configure(&self, cmd: &mut Command) {
+        match self {
+            // We `File::open`ed it when inheriting from environment,
+            // so no need to set cloexec for fifo.
+            Client::Fifo { .. } => return,
+            Client::Pipe { .. } => {}
+        };
+        // Here we basically just want to say that in the child process
+        // we'll configure the read/write file descriptors to *not* be
+        // cloexec, so they're inherited across the exec and specified as
+        // integers through `string_arg` above.
+        let read = self.read().as_raw_fd();
+        let write = self.write().as_raw_fd();
+        unsafe {
+            cmd.pre_exec(move || {
+                set_cloexec(read, false)?;
+                set_cloexec(write, false)?;
+                Ok(())
+            });
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Helper {
+    thread: JoinHandle<()>,
+    state: Arc<super::HelperState>,
+}
+
+pub(crate) fn spawn_helper(
+    client: crate::Client,
+    state: Arc<super::HelperState>,
+    mut f: Box<dyn FnMut(io::Result<crate::Acquired>) + Send>,
+) -> io::Result<Helper> {
+    static USR1_INIT: Once = Once::new();
+    let mut err = None;
+    USR1_INIT.call_once(|| unsafe {
+        let mut new: libc::sigaction = mem::zeroed();
+        #[cfg(target_os = "aix")]
+        {
+            new.sa_union.__su_sigaction = sigusr1_handler;
+        }
+        #[cfg(not(target_os = "aix"))]
+        {
+            new.sa_sigaction = sigusr1_handler as usize;
+        }
+        new.sa_flags = libc::SA_SIGINFO as _;
+        if libc::sigaction(libc::SIGUSR1, &new, ptr::null_mut()) != 0 {
+            err = Some(io::Error::last_os_error());
+        }
+    });
+
+    if let Some(e) = err.take() {
+        return Err(e);
+    }
+
+    let state2 = state.clone();
+    let thread = Builder::new().spawn(move || {
+        state2.for_each_request(|helper| loop {
+            match client.inner.acquire_allow_interrupts() {
+                Ok(Some(data)) => {
+                    break f(Ok(crate::Acquired {
+                        client: client.inner.clone(),
+                        data,
+                        disabled: false,
+                    }));
+                }
+                Err(e) => break f(Err(e)),
+                Ok(None) if helper.producer_done() => break,
+                Ok(None) => {}
+            }
+        });
+    })?;
+
+    Ok(Helper { thread, state })
+}
+
+impl Helper {
+    pub fn join(self) {
+        let dur = Duration::from_millis(10);
+        let mut state = self.state.lock();
+        debug_assert!(state.producer_done);
+
+        // We need to join our helper thread, and it could be blocked in one
+        // of two locations. First is the wait for a request, but the
+        // initial drop of `HelperState` will take care of that. Otherwise
+        // it may be blocked in `client.acquire()`. We actually have no way
+        // of interrupting that, so resort to `pthread_kill` as a fallback.
+        // This signal should interrupt any blocking `read` call with
+        // `io::ErrorKind::Interrupt` and cause the thread to cleanly exit.
+        //
+        // Note that we don't do this forever though since there's a chance
+        // of bugs, so only do this opportunistically to make a best effort
+        // at clearing ourselves up.
+        for _ in 0..100 {
+            if state.consumer_done {
+                break;
+            }
+            unsafe {
+                // Ignore the return value here of `pthread_kill`,
+                // apparently on OSX if you kill a dead thread it will
+                // return an error, but on other platforms it may not. In
+                // that sense we don't actually know if this will succeed or
+                // not!
+                libc::pthread_kill(self.thread.as_pthread_t() as _, libc::SIGUSR1);
+            }
+            state = self
+                .state
+                .cvar
+                .wait_timeout(state, dur)
+                .unwrap_or_else(|e| e.into_inner())
+                .0;
+            thread::yield_now(); // we really want the other thread to run
+        }
+
+        // If we managed to actually see the consumer get done, then we can
+        // definitely wait for the thread. Otherwise it's... off in the ether
+        // I guess?
+        if state.consumer_done {
+            drop(self.thread.join());
+        }
+    }
+}
+
+unsafe fn fcntl_check(fd: c_int) -> Result<(), FromEnvErrorInner> {
+    match libc::fcntl(fd, libc::F_GETFD) {
+        -1 => Err(FromEnvErrorInner::CannotOpenFd(
+            fd,
+            io::Error::last_os_error(),
+        )),
+        _ => Ok(()),
+    }
+}
+
+unsafe fn fd_check(fd: c_int, check_pipe: bool) -> Result<(), FromEnvErrorInner> {
+    if check_pipe {
+        let mut stat = mem::zeroed();
+        if libc::fstat(fd, &mut stat) == -1 {
+            let last_os_error = io::Error::last_os_error();
+            fcntl_check(fd)?;
+            Err(FromEnvErrorInner::NotAPipe(fd, Some(last_os_error)))
+        } else {
+            // On android arm and i686 mode_t is u16 and st_mode is u32,
+            // this generates a type mismatch when S_IFIFO (declared as mode_t)
+            // is used in operations with st_mode, so we use this workaround
+            // to get the value of S_IFIFO with the same type of st_mode.
+            #[allow(unused_assignments)]
+            let mut s_ififo = stat.st_mode;
+            s_ififo = libc::S_IFIFO as _;
+            if stat.st_mode & s_ififo == s_ififo {
+                return Ok(());
+            }
+            Err(FromEnvErrorInner::NotAPipe(fd, None))
+        }
+    } else {
+        fcntl_check(fd)
+    }
+}
+
+fn set_cloexec(fd: c_int, set: bool) -> io::Result<()> {
+    unsafe {
+        let previous = cvt(libc::fcntl(fd, libc::F_GETFD))?;
+        let new = if set {
+            previous | libc::FD_CLOEXEC
+        } else {
+            previous & !libc::FD_CLOEXEC
+        };
+        if new != previous {
+            cvt(libc::fcntl(fd, libc::F_SETFD, new))?;
+        }
+        Ok(())
+    }
+}
+
+fn set_nonblocking(fd: c_int, set: bool) -> io::Result<()> {
+    let status_flag = if set { libc::O_NONBLOCK } else { 0 };
+
+    unsafe {
+        cvt(libc::fcntl(fd, libc::F_SETFL, status_flag))?;
+    }
+
+    Ok(())
+}
+
+fn cvt(t: c_int) -> io::Result<c_int> {
+    if t == -1 {
+        Err(io::Error::last_os_error())
+    } else {
+        Ok(t)
+    }
+}
+
+extern "C" fn sigusr1_handler(
+    _signum: c_int,
+    _info: *mut libc::siginfo_t,
+    _ptr: *mut libc::c_void,
+) {
+    // nothing to do
+}