diff --git a/kernel/proc.c b/kernel/proc.c
index 417e30a..1774add 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -175,8 +175,8 @@ proc_pagetable(struct proc *p)
 void
 proc_freepagetable(pagetable_t pagetable, uint64 sz)
 {
-  uvmunmap(pagetable, TRAMPOLINE, PGSIZE, 0);
-  uvmunmap(pagetable, TRAPFRAME, PGSIZE, 0);
+  uvmunmap(pagetable, TRAMPOLINE, 1, 0);
+  uvmunmap(pagetable, TRAPFRAME, 1, 0);
   uvmfree(pagetable, sz);
 }
 
diff --git a/kernel/vm.c b/kernel/vm.c
index b48a022..92a5ff7 100644
--- a/kernel/vm.c
+++ b/kernel/vm.c
@@ -167,24 +167,23 @@ mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm)
   return 0;
 }
 
-// Remove mappings from a page table. The mappings in
-// the given range must exist. Optionally free the
-// physical memory.
+// Remove npages of mappings starting from va. va must be
+// page-aligned. The mappings must exist.
+// Optionally free the physical memory.
 void
-uvmunmap(pagetable_t pagetable, uint64 va, uint64 size, int do_free)
+uvmunmap(pagetable_t pagetable, uint64 va, uint64 npages, int do_free)
 {
-  uint64 a, last;
+  uint64 a;
   pte_t *pte;
 
-  a = PGROUNDDOWN(va);
-  last = PGROUNDDOWN(va + size - 1);
-  for(;;){
+  if((va % PGSIZE) != 0)
+    panic("uvmunmap: not aligned");
+
+  for(a = va; a < va + npages*PGSIZE; a += PGSIZE){
     if((pte = walk(pagetable, a, 0)) == 0)
       panic("uvmunmap: walk");
-    if((*pte & PTE_V) == 0){
-      printf("va=%p pte=%p\n", a, *pte);
+    if((*pte & PTE_V) == 0)
       panic("uvmunmap: not mapped");
-    }
     if(PTE_FLAGS(*pte) == PTE_V)
       panic("uvmunmap: not a leaf");
     if(do_free){
@@ -192,9 +191,6 @@ uvmunmap(pagetable_t pagetable, uint64 va, uint64 size, int do_free)
       kfree((void*)pa);
     }
     *pte = 0;
-    if(a == last)
-      break;
-    a += PGSIZE;
   }
 }
 
@@ -265,9 +261,10 @@ uvmdealloc(pagetable_t pagetable, uint64 oldsz, uint64 newsz)
   if(newsz >= oldsz)
     return oldsz;
 
-  uint64 newup = PGROUNDUP(newsz);
-  if(newup < PGROUNDUP(oldsz))
-    uvmunmap(pagetable, newup, oldsz - newup, 1);
+  if(PGROUNDUP(newsz) < PGROUNDUP(oldsz)){
+    int npages = (PGROUNDUP(oldsz) - PGROUNDUP(newsz)) / PGSIZE;
+    uvmunmap(pagetable, PGROUNDUP(newsz), npages, 1);
+  }
 
   return newsz;
 }
@@ -298,7 +295,7 @@ void
 uvmfree(pagetable_t pagetable, uint64 sz)
 {
   if(sz > 0)
-    uvmunmap(pagetable, 0, sz, 1);
+    uvmunmap(pagetable, 0, PGROUNDUP(sz)/PGSIZE, 1);
   freewalk(pagetable);
 }
 
@@ -334,7 +331,7 @@ uvmcopy(pagetable_t old, pagetable_t new, uint64 sz)
   return 0;
 
  err:
-  uvmunmap(new, 0, i, 1);
+  uvmunmap(new, 0, i / PGSIZE, 1);
   return -1;
 }