1 files changed, 89 insertions, 0 deletions
diff --git a/library/std/src/sys/stdio/teeos.rs b/library/std/src/sys/stdio/teeos.rs
new file mode 100644
index 00000000000..67e251812da
--- /dev/null
+++ b/library/std/src/sys/stdio/teeos.rs
@@ -0,0 +1,89 @@
+#![deny(unsafe_op_in_unsafe_fn)]
+
+use core::arch::asm;
+
+use crate::io;
+
+pub struct Stdin;
+pub struct Stdout;
+pub struct Stderr;
+
+const KCALL_DEBUG_CMD_PUT_BYTES: i64 = 2;
+
+unsafe fn debug_call(cap_ref: u64, call_no: i64, arg1: u64, arg2: u64) -> i32 {
+    let ret: u64;
+    unsafe {
+        asm!(
+            "svc #99",
+            inout("x0") cap_ref => ret,
+            in("x1") call_no,
+            in("x2") arg1,
+            in("x3") arg2,
+        );
+    }
+
+    ret as i32
+}
+
+fn print_buf(s: &[u8]) -> io::Result<usize> {
+    // Corresponds to `HM_DEBUG_PUT_BYTES_LIMIT`.
+    const MAX_LEN: usize = 512;
+    let len = if s.len() > MAX_LEN { MAX_LEN } else { s.len() };
+    let result = unsafe { debug_call(0, KCALL_DEBUG_CMD_PUT_BYTES, s.as_ptr() as u64, len as u64) };
+
+    if result == 0 { Ok(len) } else { Err(io::Error::from(io::ErrorKind::InvalidInput)) }
+}
+
+impl Stdin {
+    pub const fn new() -> Stdin {
+        Stdin
+    }
+}
+
+impl io::Read for Stdin {
+    fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
+        Ok(0)
+    }
+}
+
+impl Stdout {
+    pub const fn new() -> Stdout {
+        Stdout
+    }
+}
+
+impl io::Write for Stdout {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        print_buf(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl Stderr {
+    pub const fn new() -> Stderr {
+        Stderr
+    }
+}
+
+impl io::Write for Stderr {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        print_buf(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+pub const STDIN_BUF_SIZE: usize = 0;
+
+pub fn is_ebadf(err: &io::Error) -> bool {
+    err.raw_os_error() == Some(libc::EBADF as i32)
+}
+
+pub fn panic_output() -> Option<impl io::Write> {
+    Some(Stderr::new())
+}