ptos: mm: Add page allocation helpers

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

service/ptos/head/mm/vm.h

@@ -45,6 +45,10 @@ typedef struct {
     USIZE Length;
 } MM_RANGE;
 
+/* Obtain a pointer from an &MM_RANGE pointer */
+#define RANGE_PTR(RANGE_P) \
+    ((VOID *)((RANGE_P)->VirtualBase))
+
 /*
  * Unmap a virtual memory range
  *
@@ -67,6 +71,14 @@ PT_STATUS MmMapRange(
     MM_PROT Prot, MMU_PAGESIZE PageSize
 );
 
+/*
+ * Allocate one or more pages
+ *
+ * @Count:  Number of pages to allocate
+ * @Result: Result is written back here
+ */
+PT_STATUS MmAllocatePages(USIZE Count, MM_RANGE *Result);
+
 /*
  * Initialize virtual memory
  */

service/ptos/mm/vm.c

@@ -39,6 +39,23 @@ static USIZE PageSizeTable[] = {
 static UPTR VallocBump = VALLOC_BASE;
 static MM_VAD_TREE VadTree;
 
+PT_STATUS
+MmAllocatePages(USIZE Count, MM_RANGE *Result)
+{
+    MM_VAD *Vad;
+
+    if (Count == 0 || Result == NULL) {
+        return STATUS_INVALID_PARAM;
+    }
+
+    Vad = MmVadTreeAllocate(&VadTree, Count);
+    if (Vad == NULL) {
+        return STATUS_NO_MEMORY;
+    }
+
+    *Result = Vad->Range;
+    return STATUS_SUCCESS;
+}
 
 PT_STATUS MmUnmapRange(MMU_VAS *Vas, const MM_RANGE *Range, MMU_PAGESIZE PageSize)
 {