Use alloc API to fix stack overflow in release mode.

kernel/src/fs.rs

@@ -30,7 +30,12 @@ pub fn shell() {
     let files = root.borrow().list().unwrap();
     println!("Available programs: {:?}", files);
 
-    let mut buf = Box::new([0; 64 << 12]);
+    // Avoid stack overflow in release mode
+    // Equal to: `buf = Box::new([0; 64 << 12])`
+    use alloc::alloc::{alloc, dealloc, Layout};
+    const BUF_SIZE: usize = 0x40000;
+    let layout = Layout::from_size_align(BUF_SIZE, 0x1000).unwrap();
+    let buf = unsafe{ slice::from_raw_parts_mut(alloc(layout), BUF_SIZE) };
     loop {
         print!(">> ");
         use console::get_line;
@@ -47,6 +52,7 @@ pub fn shell() {
             println!("Program not exist");
         }
     }
+    unsafe { dealloc(buf.as_mut_ptr(), layout) };
 }
 
 struct MemBuf(&'static [u8]);

kernel/src/memory.rs

@@ -26,14 +26,9 @@ pub fn dealloc_frame(target: usize) {
 
 // alloc from heap
 pub fn alloc_stack() -> Stack {
-    use alloc::boxed::Box;
+    use alloc::alloc::{alloc, Layout};
     const STACK_SIZE: usize = 0x8000;
-    // FIXME: This alignment will cause rsp align with 0x8000 in x86_64 release mode.
-    //        Because kernel stack is not large enough, it will trigger double fault.
-    #[repr(align(0x8000))]
-    struct StackData([u8; STACK_SIZE]);
-    let data = Box::new(StackData([0; STACK_SIZE]));
-    let bottom = Box::into_raw(data) as usize;
+    let bottom = unsafe{ alloc(Layout::from_size_align(STACK_SIZE, 0x8000).unwrap()) } as usize;
     let top = bottom + STACK_SIZE;
     Stack { top, bottom }
 }