ptyd: expose PTS number via dup(master, ptsname) for getty slave open

ptyd/src/main.rs

@@ -7,6 +7,7 @@ use syscall::data::TimeSpec;
 
 mod controlterm;
 mod pgrp;
+mod ptsname;
 mod pty;
 mod resource;
 mod scheme;

ptyd/src/ptsname.rs

@@ -0,0 +1,86 @@
+use std::cell::RefCell;
+use std::rc::Weak;
+
+use syscall::error::{Error, Result, EBADF, EINVAL, EPIPE};
+use syscall::flag::{EventFlags, F_GETFL, F_SETFL, O_ACCMODE};
+
+use crate::pty::Pty;
+use crate::resource::Resource;
+
+/// Read-only resource exposing the PTY's numeric id.
+///
+/// relibc's `ptsname`/`ptsname_r` resolve the subterminal path via the
+/// `TIOCGPTN` ioctl, which does `dup(master, "ptsname")` and reads a
+/// `c_int` (4 bytes) — the PTS number — then formats `/scheme/pty/<n>`.
+/// Without this handler ptyd's `dup` returned `EINVAL` for "ptsname", so
+/// `ptsname` failed, getty resolved a bogus slave path, and it panicked
+/// with "failed to open slave stdin: No such file or directory". Because
+/// `Pty::id` is also the master's scheme handle id, returning it here makes
+/// the subsequent `/scheme/pty/<n>` slave open resolve to the right master.
+pub struct PtyPtsname {
+    pty: Weak<RefCell<Pty>>,
+    flags: usize,
+}
+
+impl PtyPtsname {
+    pub fn new(pty: Weak<RefCell<Pty>>, flags: usize) -> Self {
+        PtyPtsname { pty, flags }
+    }
+}
+
+impl Resource for PtyPtsname {
+    fn pty(&self) -> Weak<RefCell<Pty>> {
+        self.pty.clone()
+    }
+
+    fn flags(&self) -> usize {
+        self.flags
+    }
+
+    fn path(&mut self, buf: &mut [u8]) -> Result<usize> {
+        if let Some(pty_lock) = self.pty.upgrade() {
+            pty_lock.borrow_mut().path(buf)
+        } else {
+            Err(Error::new(EPIPE))
+        }
+    }
+
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
+        if let Some(pty_lock) = self.pty.upgrade() {
+            let id = pty_lock.borrow().id as i32;
+            let bytes = id.to_ne_bytes();
+            let n = core::cmp::min(buf.len(), bytes.len());
+            buf[..n].copy_from_slice(&bytes[..n]);
+            Ok(n)
+        } else {
+            Ok(0)
+        }
+    }
+
+    fn write(&mut self, _buf: &[u8]) -> Result<usize> {
+        Err(Error::new(EINVAL))
+    }
+
+    fn sync(&mut self) -> Result<()> {
+        Ok(())
+    }
+
+    fn fcntl(&mut self, cmd: usize, arg: usize) -> Result<usize> {
+        match cmd {
+            F_GETFL => Ok(self.flags),
+            F_SETFL => {
+                self.flags = (self.flags & O_ACCMODE) | (arg & !O_ACCMODE);
+                Ok(0)
+            }
+            _ => Err(Error::new(EINVAL)),
+        }
+    }
+
+    fn fevent(&mut self) -> Result<EventFlags> {
+        Err(Error::new(EBADF))
+    }
+
+    fn events(&mut self) -> EventFlags {
+        EventFlags::empty()
+    }
+}

ptyd/src/scheme.rs

@@ -12,6 +12,7 @@ use syscall::schemev2::NewFdFlags;
 
 use crate::controlterm::PtyControlTerm;
 use crate::pgrp::PtyPgrp;
+use crate::ptsname::PtyPtsname;
 use crate::pty::Pty;
 use crate::resource::Resource;
 use crate::subterm::PtySubTerm;
@@ -126,6 +127,8 @@ impl SchemeSync for PtyScheme {
                 Box::new(PtyTermios::new(old_resource.pty(), old_resource.flags()))
             } else if buf == b"winsize" {
                 Box::new(PtyWinsize::new(old_resource.pty(), old_resource.flags()))
+            } else if buf == b"ptsname" {
+                Box::new(PtyPtsname::new(old_resource.pty(), old_resource.flags()))
             } else {
                 return Err(Error::new(EINVAL));
             }