feat: add Rust userspace support; fix TLS layout for p_align < 16; kill whole process on sibling-thread faults

programs/rust/montauk-rt/src/io.rs

@@ -0,0 +1,82 @@
+//! Terminal output. `print!`/`println!` format into a stack buffer and hand
+//! it to SYS_PRINT in NUL-terminated chunks, so one call is one (or a few)
+//! syscalls rather than libc write()'s one SYS_PUTCHAR per byte.
+
+use core::fmt::{self, Write};
+
+use crate::sys;
+
+const CHUNK: usize = 256;
+
+/// Buffered writer to the process's terminal (stdout).
+pub struct Stdout {
+    buf: [u8; CHUNK],
+    len: usize,
+}
+
+impl Stdout {
+    pub const fn new() -> Self {
+        Stdout { buf: [0; CHUNK], len: 0 }
+    }
+
+    pub fn write_bytes(&mut self, bytes: &[u8]) {
+        for &b in bytes {
+            if b == 0 {
+                // SYS_PRINT stops at NUL; send it on its own.
+                self.flush();
+                unsafe { sys::syscall1(sys::SYS_PUTCHAR, 0) };
+                continue;
+            }
+            if self.len == CHUNK - 1 {
+                self.flush();
+            }
+            self.buf[self.len] = b;
+            self.len += 1;
+        }
+    }
+
+    pub fn flush(&mut self) {
+        if self.len == 0 {
+            return;
+        }
+        self.buf[self.len] = 0;
+        unsafe { sys::syscall1(sys::SYS_PRINT, self.buf.as_ptr() as u64) };
+        self.len = 0;
+    }
+}
+
+impl Default for Stdout {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Write for Stdout {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_bytes(s.as_bytes());
+        Ok(())
+    }
+}
+
+impl Drop for Stdout {
+    fn drop(&mut self) {
+        self.flush();
+    }
+}
+
+#[doc(hidden)]
+pub fn _print(args: fmt::Arguments) {
+    let mut out = Stdout::new();
+    let _ = out.write_fmt(args);
+}
+
+#[macro_export]
+macro_rules! print {
+    ($($arg:tt)*) => { $crate::io::_print(format_args!($($arg)*)) };
+}
+
+#[macro_export]
+macro_rules! println {
+    () => { $crate::print!("\n") };
+    ($($arg:tt)*) => { $crate::io::_print(format_args!("{}\n", format_args!($($arg)*))) };
+}