xv6: use stosb for memset

string.c

 #include "types.h"
+#include "x86.h"
 
 void*
 memset(void *dst, int c, uint n)
 {
-  char *d;
-
-  d = (char*)dst;
-  while(n-- > 0)
-    *d++ = c;
-
+  stosb(dst, c, n);
   return dst;
 }
 

ulib.c

@@ -2,6 +2,7 @@
 #include "stat.h"
 #include "fcntl.h"
 #include "user.h"
+#include "x86.h"
 
 char*
 strcpy(char *s, char *t)
@@ -35,11 +36,7 @@ strlen(char *s)
 void*
 memset(void *dst, int c, uint n)
 {
-  char *d;
-  
-  d = dst;
-  while(n-- > 0)
-    *d++ = c;
+  stosb(dst, c, n);
   return dst;
 }