stos/amd64: Add processor primitives

Signed-off-by: Chloe M. <chloe@mensia.org>

paw/stos/head/arch/amd64/prim.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Processor primitives
+ * Author:      Chloe M.
+ */
+
+#ifndef _MACHINE_PRIM_H_
+#define _MACHINE_PRIM_H_ 1
+
+#include <stdef.h>
+
+#define MdCpuSuspend()  ASMV("hlt")
+#define MdCpuSpinWait() ASMV("pause")
+
+/*
+ * Atomic swap operation
+ *
+ * @Ptr: Location to swap with @Value
+ * @Value: Value to swap to @Ptr
+ */
+ALWAYS_INLINE static inline QUAD
+MdCpuAswap(QUAD *Ptr, QUAD Value)
+{
+    QUAD RetVal;
+
+    if (Ptr == NULL) {
+        return 0;
+    }
+
+    RetVal = *(volatile QUAD *)Ptr;
+    ASMV(
+        "xchg %0, %1\n"
+        : "+m" (*Ptr), "+r" (Value)
+        :
+        : "memory"
+    );
+
+    return RetVal;
+}
+
+#endif  /* !_MACHINE_PRIM_H_ */

paw/stos/head/hal/prim.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Processor primitives
+ * Author:      Chloe M.
+ */
+
+#ifndef _HAL_PRIM_H_
+#define _HAL_PRIM_H_ 1
+
+#include <machine/prim.h>
+
+#define HalCpuSuspend  MdCpuSuspend
+#define HalCpuSpinWait MdCpuSpinWait
+#define HalCpuAswap    MdCpuAswap
+
+#endif  /* !_HAL_PRIM_H_ */