Add a linked list allocator for heap that can now do 256 mib due to

frame allocator optimizations, make a basic init function in arch that
will initialize everything for a given arch. Add tests in kmain for
alloc, and add a Locked struct used for static mutables and the linked
list.

kernel/src/util.rs

@@ -0,0 +1,36 @@
+use spin::{Mutex, MutexGuard};
+
+pub struct LinkedNode {
+    pub size: usize,
+    pub next: Option<&'static mut LinkedNode>,
+}
+
+impl LinkedNode {
+    pub const fn new(size: usize) -> LinkedNode {
+        LinkedNode { size, next: None }
+    }
+
+    pub fn start_addr(&self) -> usize {
+        self as *const Self as usize
+    }
+
+    pub fn end_addr(&self) -> usize {
+        self.start_addr() + self.size
+    }
+}
+
+pub struct Locked<A> {
+    inner: Mutex<A>,
+}
+
+impl<A> Locked<A> {
+    pub const fn new(inner: A) -> Self {
+        Locked {
+            inner: Mutex::new(inner),
+        }
+    }
+
+    pub fn lock(&self) -> MutexGuard<A> {
+        self.inner.lock()
+    }
+}