diff --git a/kernel/kalloc.c b/kernel/kalloc.c
index fa6a0ac..0699e7e 100644
--- a/kernel/kalloc.c
+++ b/kernel/kalloc.c
@@ -39,7 +39,7 @@ freerange(void *pa_start, void *pa_end)
     kfree(p);
 }
 
-// Free the page of physical memory pointed at by v,
+// Free the page of physical memory pointed at by pa,
 // which normally should have been returned by a
 // call to kalloc().  (The exception is when
 // initializing the allocator; see kinit above.)
diff --git a/kernel/printf.c b/kernel/printf.c
index e1347de..1a50203 100644
--- a/kernel/printf.c
+++ b/kernel/printf.c
@@ -109,6 +109,7 @@ printf(char *fmt, ...)
       break;
     }
   }
+  va_end(ap);
 
   if(locking)
     release(&pr.lock);
diff --git a/mkfs/mkfs.c b/mkfs/mkfs.c
index 9ad4abb..1ec326b 100644
--- a/mkfs/mkfs.c
+++ b/mkfs/mkfs.c
@@ -42,7 +42,7 @@ uint ialloc(ushort type);
 void iappend(uint inum, void *p, int n);
 void die(const char *);
 
-// convert to intel byte order
+// convert to riscv byte order
 ushort
 xshort(ushort x)
 {
diff --git a/user/ls.c b/user/ls.c
index b54d951..c67b84b 100644
--- a/user/ls.c
+++ b/user/ls.c
@@ -42,6 +42,7 @@ ls(char *path)
   }
 
   switch(st.type){
+  case T_DEVICE:
   case T_FILE:
     printf("%s %d %d %l\n", fmtname(path), st.type, st.ino, st.size);
     break;