stos: mm: Add virtual page allocation

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

paw/stos/head/mm/vad.h

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: VAD management
+ * Author:      Chloe M.
+ */
+
+#ifndef _MM_VAD_H_
+#define _MM_VAD_H_ 1
+
+#include <stdef.h>
+
+#define VAD_FROM_VMA(VMA) \
+    ((MM_VAD *)(VMA))
+
+/*
+ * A virtual address descriptor represents a specific
+ * page of memory.
+ *
+ * @Next:  Next free page
+ * @Prev:  Previous free page
+ */
+typedef struct _MM_VAD {
+    struct _MM_VAD *Next;
+    struct _MM_VAD *Prev;
+} MM_VAD;
+
+/*
+ * Represents a virtual address descriptor list
+ *
+ * @First: First entry in VAD list
+ * @Last:  Last entry in VAD list
+ */
+typedef struct {
+    MM_VAD *First;
+    MM_VAD *Last;
+} MM_VAD_LIST;
+
+/*
+ * Append a VAD to VAD list
+ *
+ * @List: VAD list to append to
+ * @Vad:  VAD list to append
+ */
+VOID MmVadListAppend(MM_VAD_LIST *List, MM_VAD *Vad);
+
+/*
+ * Pop a VAD from a VAD list
+ *
+ * @List: VAD list to pop from
+ *
+ * Returns NULL if no more entries
+ */
+MM_VAD *MmVadListPop(MM_VAD_LIST *List);
+
+#endif  /* !_MM_VAD_H_ */

paw/stos/head/mm/vmm.h

@@ -24,4 +24,13 @@
  */
 VOID MmInitVmm(VOID);
 
+/*
+ * Allocate a number of contiguous pages
+ *
+ * @Count: Number of pages to allocate
+ *
+ * Returns NULL on failure
+ */
+VOID *MmAllocPages(USIZE Count);
+
 #endif  /* !_MM_VMM_H_ */