Simple, unsafe context switch

kernel/context/mod.rs

@@ -1,6 +1,8 @@
 //! Context management
 
+use alloc::boxed::Box;
 use collections::{BTreeMap, Vec};
+use core::mem;
 use core::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
 use spin::{Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
 
@@ -61,6 +63,15 @@ impl ContextList {
         let context_lock = self.new_context()?;
         {
             let mut context = context_lock.write();
+            let mut stack = Box::new([0; 4096]);
+            let offset = stack.len() - mem::size_of::<usize>();
+            unsafe {
+                let offset = stack.len() - mem::size_of::<usize>();
+                let func_ptr = stack.as_mut_ptr().offset(offset as isize);
+                *(func_ptr as *mut usize) = func as usize;
+            }
+            context.arch.set_stack(stack.as_ptr() as usize + offset);
+            context.kstack = Some(stack);
             print!("{}", format!("{}: {:X}\n", context.id, func as usize));
         }
         Ok(context_lock)
@@ -108,6 +119,8 @@ pub struct Context {
     pub id: usize,
     /// The architecture specific context
     pub arch: ArchContext,
+    /// Kernel stack
+    pub kstack: Option<Box<[u8]>>,
     /// The open files in the scheme
     pub files: Vec<Option<file::File>>
 }
@@ -118,6 +131,7 @@ impl Context {
         Context {
             id: id,
             arch: ArchContext::new(),
+            kstack: None,
             files: Vec::new()
         }
     }

kernel/lib.rs

@@ -134,8 +134,24 @@ pub extern fn kmain() {
 
     print!("{}", format!("BSP: {:?}\n", syscall::getpid()));
 
-    if let Ok(context) = context::contexts_mut().spawn(context_test) {
+    let to_ptr = if let Ok(context_lock) = context::contexts_mut().spawn(context_test) {
+        print!("Spawned context\n");
+        let mut context = context_lock.write();
+        &mut context.arch as *mut arch::context::Context
+    } else {
+        0 as *mut arch::context::Context
+    };
 
+    let from_ptr = if let Some(context_lock) = context::contexts().current() {
+        let mut context = context_lock.write();
+        &mut context.arch as *mut arch::context::Context
+    } else {
+        0 as *mut arch::context::Context
+    };
+
+    if to_ptr as usize != 0 && from_ptr as usize != 0 {
+        print!("Switching\n");
+        unsafe { (&mut *from_ptr).switch_to(&mut *to_ptr); }
     }
 
     loop {