From a490ff13ae8477f6387773317d294ff7f509bb5d Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jackpot51@gmail.com>
Date: Sun, 14 Aug 2016 15:58:35 -0600
Subject: [PATCH] Add syscall module

---
 kernel/lib.rs             |  6 +++
 kernel/syscall/fs.rs      | 27 +++++++++++
 kernel/syscall/mod.rs     | 95 +++++++++++++++++++++++++++++++++++++++
 kernel/syscall/process.rs | 10 +++++
 4 files changed, 138 insertions(+)
 create mode 100644 kernel/syscall/fs.rs
 create mode 100644 kernel/syscall/mod.rs
 create mode 100644 kernel/syscall/process.rs

diff --git a/kernel/lib.rs b/kernel/lib.rs
index 5927692..1d0e884 100644
--- a/kernel/lib.rs
+++ b/kernel/lib.rs
@@ -65,6 +65,7 @@
 //! In this case, it is recommended to add one page, 4096 bytes, to the buffer and retry.
 
 #![feature(lang_items)]
+#![feature(question_mark)]
 #![no_std]
 
 #[macro_use]
@@ -85,6 +86,9 @@ extern crate arch_x86_64 as arch;
 /// Intrinsics for panic handling
 pub mod panic;
 
+/// Syscall handlers
+pub mod syscall;
+
 /// Tests
 #[cfg(test)]
 pub mod tests;
@@ -93,6 +97,8 @@ pub mod tests;
 pub extern fn kmain() {
     println!("TEST");
 
+    println!("{:?}", syscall::open(b"file:/test/file", 0));
+
     unsafe { set_interrupts() };
     loop {
         unsafe { halt() };
diff --git a/kernel/syscall/fs.rs b/kernel/syscall/fs.rs
new file mode 100644
index 0000000..d3c6a15
--- /dev/null
+++ b/kernel/syscall/fs.rs
@@ -0,0 +1,27 @@
+//! Filesystem syscalls
+
+use super::Result;
+
+/// Read syscall
+pub fn read(fd: usize, buf: &mut [u8]) -> Result<usize> {
+    println!("Read {}: {}", fd, buf.len());
+    Ok(0)
+}
+
+/// Write syscall
+pub fn write(fd: usize, buf: &[u8]) -> Result<usize> {
+    println!("Write {}: {}", fd, buf.len());
+    Ok(0)
+}
+
+/// Open syscall
+pub fn open(path: &[u8], flags: usize) -> Result<usize> {
+    println!("Open {:?}: {:X}", ::core::str::from_utf8(path), flags);
+    Ok(0)
+}
+
+/// Close syscall
+pub fn close(fd: usize) -> Result<usize> {
+    println!("Close {}", fd);
+    Ok(0)
+}
diff --git a/kernel/syscall/mod.rs b/kernel/syscall/mod.rs
new file mode 100644
index 0000000..cd71b76
--- /dev/null
+++ b/kernel/syscall/mod.rs
@@ -0,0 +1,95 @@
+///! Syscall handlers
+
+use core::slice;
+
+pub use self::fs::*;
+pub use self::process::*;
+
+/// Filesystem syscalls
+pub mod fs;
+
+/// Process syscalls
+pub mod process;
+
+/// System call list
+#[derive(Copy, Clone, Debug)]
+pub enum Call {
+    /// Exit syscall
+    Exit,
+    /// Read syscall
+    Read,
+    /// Write syscall
+    Write,
+    /// Open syscall
+    Open,
+    /// Close syscall
+    Close,
+    /// Unknown syscall
+    Unknown
+}
+
+/// Convert numbers to calls
+/// See http://syscalls.kernelgrok.com/
+impl From<usize> for Call {
+    fn from(number: usize) -> Call {
+        match number {
+            1 => Call::Exit,
+            3 => Call::Read,
+            4 => Call::Write,
+            5 => Call::Open,
+            6 => Call::Close,
+            _ => Call::Unknown
+        }
+    }
+}
+
+/// The error number for an invalid value
+#[derive(Copy, Clone, Debug)]
+pub enum Error {
+    /// Operation not permitted
+    NotPermitted,
+    /// No such file or directory
+    NoEntry,
+    /// Invalid argument
+    InvalidValue,
+    /// Syscall not implemented
+    NoCall
+}
+
+/// Convert errors to numbers
+/// See http://www-numi.fnal.gov/offline_software/srt_public_context/WebDocs/Errors/unix_system_errors.html
+impl From<Error> for usize {
+    fn from(err: Error) -> usize {
+        match err {
+            Error::NotPermitted => 1,
+            Error::NoEntry => 2,
+            Error::InvalidValue => 22,
+            Error::NoCall => 38
+        }
+    }
+}
+
+pub type Result<T> = ::core::result::Result<T, Error>;
+
+/// Convert a pointer and length to slice, if valid
+/// TODO: Check validity
+pub fn convert_slice(ptr: usize, len: usize) -> Result<&'static [u8]> {
+    Ok(unsafe { slice::from_raw_parts(ptr as *const u8, len) })
+}
+
+/// Convert a pointer and length to slice, if valid
+/// TODO: Check validity
+pub fn convert_slice_mut(ptr: usize, len: usize) -> Result<&'static mut [u8]> {
+    Ok(unsafe { slice::from_raw_parts_mut(ptr as *mut u8, len) })
+}
+
+pub fn handle(a: usize, b: usize, c: usize, d: usize) -> ::core::result::Result<usize, usize> {
+    match Call::from(a) {
+        Call::Exit => exit(b),
+        Call::Read => read(b, convert_slice_mut(c, d)?),
+        Call::Write => write(b, convert_slice(c, d)?),
+        Call::Open => open(convert_slice(b, c)?, d),
+        Call::Close => close(b),
+        Call::Unknown => Err(Error::NoCall)
+    }.map_err(|err| err.into())
+}
diff --git a/kernel/syscall/process.rs b/kernel/syscall/process.rs
new file mode 100644
index 0000000..6cbe1ec
--- /dev/null
+++ b/kernel/syscall/process.rs
@@ -0,0 +1,10 @@
+///! Process syscalls
+
+use arch::interrupt::halt;
+
+pub fn exit(status: usize) -> ! {
+    println!("Exit {}", status);
+    loop {
+        unsafe { halt() };
+    }
+}