Auto merge of #116207 - Ayush1325:uefi_stdio, r=Mark-Simulacrum

Stdio support for UEFI

- Uses Simple Text Output Protocol and Simple Text Input Protocol
- Reading is done one character at a time
- Writing is done with max 4096 characters

# Quirks
## Output Newline
- UEFI uses CRLF for newline. So when running the application in UEFI shell (qemu VGA), the output of `println` looks weird.
- However, since the UEFI shell supports piping output, I am unsure if doing any output post-processing is a good idea. UEFI shell `cat` command seems to work fine with just LF.

## Input Newline
- `Stdin.read_line()` method is broken in UEFI shell. Pressing enter seems to be read as CR, which means LF is never encountered.
- Works fine with input redirection from file.

CC `@dvdhrm`

library/std/src/lib.rs

@@ -259,7 +259,7 @@
  all(target_vendor = "fortanix", target_env = "sgx"),
  feature(slice_index_methods, coerce_unsized, sgx_platform)
 )]
-#![cfg_attr(windows, feature(round_char_boundary))]
+#![cfg_attr(any(windows, target_os = "uefi"), feature(round_char_boundary))]
 #![cfg_attr(target_os = "xous", feature(slice_ptr_len))]
 //
 // Language features:

library/std/src/sys/uefi/mod.rs

@@ -36,7 +36,6 @@ pub mod path;
 pub mod pipe;
 #[path = "../unsupported/process.rs"]
 pub mod process;
-#[path = "../unsupported/stdio.rs"]
 pub mod stdio;
 #[path = "../unsupported/thread.rs"]
 pub mod thread;

library/std/src/sys/uefi/stdio.rs

@@ -0,0 +1,162 @@
+use crate::io;
+use crate::iter::Iterator;
+use crate::mem::MaybeUninit;
+use crate::os::uefi;
+use crate::ptr::NonNull;
+
+const MAX_BUFFER_SIZE: usize = 8192;
+
+pub struct Stdin;
+pub struct Stdout;
+pub struct Stderr;
+
+impl Stdin {
+ pub const fn new() -> Stdin {
+ Stdin
+ }
+}
+
+impl io::Read for Stdin {
+ fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+ let st: NonNull<r_efi::efi::SystemTable> = uefi::env::system_table().cast();
+ let stdin = unsafe { (*st.as_ptr()).con_in };
+
+ // Try reading any pending data
+ let inp = match read_key_stroke(stdin) {
+ Ok(x) => x,
+ Err(e) if e == r_efi::efi::Status::NOT_READY => {
+ // Wait for keypress for new data
+ wait_stdin(stdin)?;
+ read_key_stroke(stdin).map_err(|x| io::Error::from_raw_os_error(x.as_usize()))?
+ }
+ Err(e) => {
+ return Err(io::Error::from_raw_os_error(e.as_usize()));
+ }
+ };
+
+ // Check if the key is printiable character
+ if inp.scan_code != 0x00 {
+ return Err(io::const_io_error!(io::ErrorKind::Interrupted, "Special Key Press"));
+ }
+
+ // SAFETY: Iterator will have only 1 character since we are reading only 1 Key
+ // SAFETY: This character will always be UCS-2 and thus no surrogates.
+ let ch: char = char::decode_utf16([inp.unicode_char]).next().unwrap().unwrap();
+ if ch.len_utf8() > buf.len() {
+ return Ok(0);
+ }
+
+ ch.encode_utf8(buf);
+
+ Ok(ch.len_utf8())
+ }
+}
+
+impl Stdout {
+ pub const fn new() -> Stdout {
+ Stdout
+ }
+}
+
+impl io::Write for Stdout {
+ fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+ let st: NonNull<r_efi::efi::SystemTable> = uefi::env::system_table().cast();
+ let stdout = unsafe { (*st.as_ptr()).con_out };
+
+ write(stdout, 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> {
+ let st: NonNull<r_efi::efi::SystemTable> = uefi::env::system_table().cast();
+ let stderr = unsafe { (*st.as_ptr()).std_err };
+
+ write(stderr, buf)
+ }
+
+ fn flush(&mut self) -> io::Result<()> {
+ Ok(())
+ }
+}
+
+// UCS-2 character should occupy 3 bytes at most in UTF-8
+pub const STDIN_BUF_SIZE: usize = 3;
+
+pub fn is_ebadf(_err: &io::Error) -> bool {
+ true
+}
+
+pub fn panic_output() -> Option<impl io::Write> {
+ uefi::env::try_system_table().map(|_| Stderr::new())
+}
+
+fn write(
+ protocol: *mut r_efi::protocols::simple_text_output::Protocol,
+ buf: &[u8],
+) -> io::Result<usize> {
+ let mut utf16 = [0; MAX_BUFFER_SIZE / 2];
+
+ // Get valid UTF-8 buffer
+ let utf8 = match crate::str::from_utf8(buf) {
+ Ok(x) => x,
+ Err(e) => unsafe { crate::str::from_utf8_unchecked(&buf[..e.valid_up_to()]) },
+ };
+ // Clip UTF-8 buffer to max UTF-16 buffer we support
+ let utf8 = &utf8[..utf8.floor_char_boundary(utf16.len() - 1)];
+
+ for (i, ch) in utf8.encode_utf16().enumerate() {
+ utf16[i] = ch;
+ }
+
+ unsafe { simple_text_output(protocol, &mut utf16) }?;
+
+ Ok(utf8.len())
+}
+
+unsafe fn simple_text_output(
+ protocol: *mut r_efi::protocols::simple_text_output::Protocol,
+ buf: &mut [u16],
+) -> io::Result<()> {
+ let res = unsafe { ((*protocol).output_string)(protocol, buf.as_mut_ptr()) };
+ if res.is_error() { Err(io::Error::from_raw_os_error(res.as_usize())) } else { Ok(()) }
+}
+
+fn wait_stdin(stdin: *mut r_efi::protocols::simple_text_input::Protocol) -> io::Result<()> {
+ let boot_services: NonNull<r_efi::efi::BootServices> =
+ uefi::env::boot_services().unwrap().cast();
+ let wait_for_event = unsafe { (*boot_services.as_ptr()).wait_for_event };
+ let wait_for_key_event = unsafe { (*stdin).wait_for_key };
+
+ let r = {
+ let mut x: usize = 0;
+ (wait_for_event)(1, [wait_for_key_event].as_mut_ptr(), &mut x)
+ };
+ if r.is_error() { Err(io::Error::from_raw_os_error(r.as_usize())) } else { Ok(()) }
+}
+
+fn read_key_stroke(
+ stdin: *mut r_efi::protocols::simple_text_input::Protocol,
+) -> Result<r_efi::protocols::simple_text_input::InputKey, r_efi::efi::Status> {
+ let mut input_key: MaybeUninit<r_efi::protocols::simple_text_input::InputKey> =
+ MaybeUninit::uninit();
+
+ let r = unsafe { ((*stdin).read_key_stroke)(stdin, input_key.as_mut_ptr()) };
+
+ if r.is_error() {
+ Err(r)
+ } else {
+ let input_key = unsafe { input_key.assume_init() };
+ Ok(input_key)
+ }
+}

src/doc/rustc/src/platform-support/unknown-uefi.md

@@ -265,9 +265,12 @@ cargo build --target x86_64-unknown-uefi -Zbuild-std=std,panic_abort
 #### os_str
 - While the strings in UEFI should be valid UCS-2, in practice, many implementations just do not care and use UTF-16 strings.
 - Thus, the current implementation supports full UTF-16 strings.
+#### stdio
+- Uses `Simple Text Input Protocol` and `Simple Text Output Protocol`.
+- Note: UEFI uses CRLF for new line. This means Enter key is registered as CR instead of LF.
 
 ## Example: Hello World With std
-The following code features a valid UEFI application, including stdio and `alloc` (`OsString` and `Vec`):
+The following code features a valid UEFI application, including `stdio` and `alloc` (`OsString` and `Vec`):
 
 This example can be compiled as binary crate via `cargo` using the toolchain
 compiled from the above source (named custom):
@@ -286,6 +289,9 @@ use std::{
 };
 
 pub fn main() {
+ println!("Starting Rust Application...");
+
+ // Use System Table Directly
  let st = env::system_table().as_ptr() as *mut efi::SystemTable;
  let mut s: Vec<u16> = OsString::from("Hello World!\n").encode_wide().collect();
  s.push(0);