Implement sched_yield, enable interrupts in userspace

kernel/syscall/mod.rs

@@ -30,6 +30,8 @@ pub enum Call {
     Exec = 11,
     /// Get process ID
     GetPid = 20,
+    /// Yield to scheduler
+    SchedYield = 158
 }
 
 /// Convert numbers to calls
@@ -44,6 +46,7 @@ impl Call {
             6 => Ok(Call::Close),
             11 => Ok(Call::Exec),
             20 => Ok(Call::GetPid),
+            158 => Ok(Call::SchedYield),
             _ => Err(Error::NoCall)
         }
     }
@@ -97,6 +100,7 @@ pub fn handle(a: usize, b: usize, c: usize, d: usize, e: usize, _f: usize) -> Re
         Call::Close => close(b),
         Call::Exec => exec(convert_slice(b as *const u8, c)?, convert_slice(d as *const [usize; 2], e)?),
         Call::GetPid => getpid(),
+        Call::SchedYield => sched_yield()
     }
 }
 

kernel/syscall/process.rs

@@ -28,3 +28,8 @@ pub fn getpid() -> Result<usize> {
     let context = context_lock.read();
     Ok(context.id)
 }
+
+pub fn sched_yield() -> Result<usize> {
+    unsafe { context::switch(); }
+    Ok(0)
+}