Merge pull request 'add new syscalls; cross platform abstraction for io and rng seeding' (#1) from Monadic-Cat/libwasm:add-io-rand into master

Reviewed-on: https://git.ablecorp.us:443/able/libwasm/pulls/1

Cargo.toml

@@ -6,3 +6,19 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+once_cell = { version = "1.10.0", default-features = false, features = ["std"], optional = true }
+rand_core = { version = "0.6", default-features = false, optional = true }
+rand_pcg = { version = "0.3.1", default-features = false, optional = true }
+
+[target.'cfg(not(ableOS))'.dependencies]
+rand_core = { version = "0.6", default-features = false, optional = true, features = ["getrandom"] }
+
+
+[features]
+default = ["rng", "pcg_rng", "io"]
+# Controls availability of the `rand` module, which provides seeding for `rand` (the crate) RNGs.
+rng = ["dep:rand_core"]
+# Controls the availability of `obtain_rng`, which internally uses `rand_pcg`.
+pcg_rng = ["rng", "dep:rand_pcg"]
+# Controls the availability of the cross platform `io` module.
+io = ["dep:once_cell"]

src/io.rs

@@ -0,0 +1,144 @@
+//! This module provides cross platform I/O facilities. It takes inspiration from the Rust `std::io` module,
+//! and uses that for platform support outside of ableOS.
+//! One day, we might hope for this module to be superseded by real `std` support for ableOS.
+use ::std::io::{self, Read, BufRead, BufReader, IoSliceMut};
+
+/// Print a string to the console.
+fn print(x: &str) {
+    #[cfg(ableOS)] {
+        extern "C" {
+            fn print_char(x: u32);
+        }
+        fn print_byte(x: u8) {
+            unsafe { print_char(x as u32) }
+        }
+        for b in x.bytes() {
+            print_byte(b);
+        }
+    }
+    #[cfg(not(ableOS))] {
+        print!("{}", x)
+    }
+}
+/// Like [`print`], but starts a new line after.
+pub fn println(x: &str) {
+    print(x);
+    print("\n");
+}
+
+/// Like [`println`], but meant to print to a standard error output.
+pub fn eprintln(x: &str) {
+    #[cfg(ableOS)] {
+        println(x);
+    }
+    #[cfg(not(ableOS))] {
+        eprintln!("{}", x)
+    }
+}
+
+#[cfg(ableOS)]
+static STDIN: ::once_cell::sync::Lazy<::std::sync::Mutex<BufReader<AbleStdinRaw>>> = ::once_cell::sync::Lazy::new(|| {
+    ::std::sync::Mutex::new(BufReader::new(AbleStdinRaw))
+});
+
+#[cfg(ableOS)]
+struct AbleStdinRaw;
+#[cfg(ableOS)]
+impl Read for AbleStdinRaw {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        // TODO: detect EOF
+        loop {
+            let chr = unsafe { crate::syscalls::get_input() };
+            if chr != 0 {
+                break Ok(char::from_u32(chr as u32).unwrap().encode_utf8(buf).len())
+            }
+        }
+    }
+}
+
+/// A handle to the standard input stream of the process.
+/// See [`Stdin`](::std::io::Stdin) for roughly how this should be treated.
+pub struct Stdin {
+    #[cfg(ableOS)]
+    inner: &'static ::std::sync::Mutex<BufReader<AbleStdinRaw>>,
+    #[cfg(not(ableOS))]
+    inner: io::Stdin,
+}
+impl Stdin {
+    pub fn lock(&self) -> StdinLock<'_> {
+        #[cfg(ableOS)] {
+            StdinLock {
+                inner: self.inner.lock().unwrap()
+            }
+        }
+        #[cfg(not(ableOS))] {
+            StdinLock {
+                inner: self.inner.lock(),
+            }
+        }
+    }
+}
+
+/// A locked reference to the [`Stdin`] handle.
+/// See [`StdinLock`](::std::io::StdinLock) for roughly how this should be treated.
+pub struct StdinLock<'a> {
+    #[cfg(ableOS)]
+    inner: ::std::sync::MutexGuard<'a, BufReader<AbleStdinRaw>>,
+    #[cfg(not(ableOS))]
+    inner: io::StdinLock<'a>,
+}
+
+impl<'a> BufRead for StdinLock<'_> {
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        self.inner.fill_buf()
+    }
+
+    fn consume(&mut self, n: usize) {
+        self.inner.consume(n)
+    }
+
+    fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> io::Result<usize> {
+        self.inner.read_until(byte, buf)
+    }
+
+    fn read_line(&mut self, buf: &mut String) -> io::Result<usize> {
+        self.inner.read_line(buf)
+    }
+}
+impl Read for StdinLock<'_> {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+
+    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        self.inner.read_vectored(bufs)
+    }
+
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        self.inner.read_to_end(buf)
+    }
+
+    fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize> {
+        self.inner.read_to_string(buf)
+    }
+
+    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
+        self.inner.read_exact(buf)
+    }
+}
+
+/// Constructs a new handle to the standard input of the current process.
+/// Each handle returned is a reference to a shared global buffer whose access is synchronized via a mutex.
+/// If you need more explicit control over locking, see the [`Stdin::lock`] method.
+pub fn stdin() -> Stdin {
+    #[cfg(ableOS)] {
+        Stdin {
+            inner: &STDIN
+        }
+    }
+    #[cfg(not(ableOS))] {
+        Stdin {
+            inner: ::std::io::stdin(),
+        }
+    }
+}

src/lib.rs

@@ -1,13 +1,22 @@
-#![no_std]
+//! The base crate for writing guest programs to run on ableOS.
+//!
+//! ableOS is not a target known to rustc, and so we rely on a general `--cfg` switch
+//! to control the use of ableOS target specific code when underlying the portable
+//! abstractions defined in this crate.
+//!
+//! To target ableOS, set `cfg(ableOS)` and `--target=wasm32-unknown-unknown`.
+//! ```text
+//! RUSTFLAGS='--cfg=ableOS' cargo build --target=wasm32-unknown-unknown
+//! ```
 
 #[macro_use]
 pub mod logger;
 pub mod driver;
 pub mod process;
 pub mod syscalls;
+#[cfg(feature = "io")]
+pub mod io;
+#[cfg(feature = "rng")]
+pub mod rand;
 
 pub use core::*;
-
-extern "C" {
-    pub fn get_random() -> u32;
-}

src/rand.rs

@@ -0,0 +1,21 @@
+use ::rand_core::SeedableRng;
+
+/// Seed an RNG with system provided randomness.
+pub fn seed_rng<R: SeedableRng>() -> R {
+    #[cfg(ableOS)] {
+        let seed = unsafe {
+            let seed_a = crate::syscalls::get_random();
+            let seed_b = crate::syscalls::get_random();
+            (seed_a as u64) << 32 | seed_b as u64
+        };
+        R::seed_from_u64(seed)
+    }
+    #[cfg(not(ableOS))] {
+        R::from_entropy()
+    }
+}
+
+#[cfg(feature = "pcg_rng")]
+pub fn obtain_rng() -> impl ::rand_core::RngCore {
+    seed_rng::<::rand_pcg::Pcg32>()
+}

src/syscalls/mod.rs

@@ -1,12 +1,11 @@
 #![deny(missing_docs)]
-//! The module of syscalls.
+//! This module provides declarations for all host provided functions.
 
 use crate::process::{signals::Signals, PID};
 
 pub mod file_calls;
 pub mod time_calls;
 
-#[no_mangle]
 /// All system calls are defined here.
 extern "C" {
 
@@ -21,4 +20,11 @@ extern "C" {
     /// A temporary function to test the syscall interface
     pub fn add(a: u32, b: u32) -> u32;
 
+    // TODO: ascertain whether the ableOS host provides randomness good enough for CSPRNGs
+    /// The ableOS host provides entropy usable for seeding PRNGs.
+    pub fn get_random() -> u32;
+
+    // This currently has very x86 specific semantics.
+    /// Pops a byte from the key buffer.
+    pub fn get_input() -> i32;
 }