Made va and size page aligned in mappages

kernel/vm.c

@@ -136,8 +136,9 @@ kvmmap(pagetable_t kpgtbl, uint64 va, uint64 pa, uint64 sz, int perm)
 }
 
 // Create PTEs for virtual addresses starting at va that refer to
-// physical addresses starting at pa. va and size might not
-// be page-aligned. Returns 0 on success, -1 if walk() couldn't
+// physical addresses starting at pa.
+// va and size MUST be page-aligned.
+// Returns 0 on success, -1 if walk() couldn't
 // allocate a needed page-table page.
 int
 mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm)
@@ -145,11 +146,17 @@ mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm)
   uint64 a, last;
   pte_t *pte;
 
+  if((va % PGSIZE) != 0)
+    panic("mappages: va not aligned");
+
+  if((size % PGSIZE) != 0)
+    panic("mappages: size not aligned");
+
   if(size == 0)
     panic("mappages: size");
   
-  a = PGROUNDDOWN(va);
-  last = PGROUNDDOWN(va + size - 1);
+  a = va;
+  last = va + size - PGSIZE;
   for(;;){
     if((pte = walk(pagetable, a, 1)) == 0)
       return -1;