Add a Stack convenience class

kernel/src/arch/CPU.h

@@ -13,7 +13,7 @@ namespace CPU
 
     [[noreturn]] void efficient_halt();
 
-    void idle_loop();
+    [[noreturn]] void idle_loop();
 
     void switch_kernel_stack(u64 top);
 

kernel/src/arch/x86_64/CPU.cpp

@@ -430,7 +430,7 @@ namespace CPU
         goto loop;           // Safeguard: if we ever wake up, start our low-power rest again
     }
 
-    void idle_loop()
+    [[noreturn]] void idle_loop()
     {
         asm volatile("sti");
     loop:

kernel/src/arch/x86_64/CPU.h

@@ -1,3 +1,4 @@
+#pragma once
 #include <luna/Types.h>
 
 struct Registers // Saved CPU registers for x86-64

luna/include/luna/Stack.h

@@ -0,0 +1,23 @@
+#pragma once
+#include <luna/Types.h>
+
+struct Stack
+{
+    Stack(u64 base, usize bytes);
+
+    u64 bottom()
+    {
+        return m_base;
+    }
+
+    u64 top();
+
+    usize bytes()
+    {
+        return m_bytes;
+    }
+
+  private:
+    u64 m_base;
+    usize m_bytes;
+};

luna/src/Bitmap.cpp

@@ -62,11 +62,14 @@ void Bitmap::clear_region(usize start, usize bits, bool value)
     expect(initialized(), "Bitmap was never initialized");
     expect((start + bits) <= size(), "Bitmap clear out of range");
 
+    if (!bits) return;
+
     // Set individual bits while not on a byte boundary.
-    while ((start % 8) && bits--)
+    while ((start % 8) && bits)
     {
         set(start, value);
         start++;
+        bits--;
     }
 
     // Clear out the rest in bytes.

luna/src/Stack.cpp

@@ -0,0 +1,10 @@
+#include <luna/Stack.h>
+
+Stack::Stack(u64 base, usize bytes) : m_base(base), m_bytes(bytes)
+{
+}
+
+u64 Stack::top()
+{
+    return (m_base + m_bytes) - sizeof(void*);
+}