From 7a6d57235c41df877b3fb2322cf770e65e864058 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Fri, 12 Aug 2022 14:59:30 -0400
Subject: [PATCH] Costmestic change (thanks Harry Porter)

---
 kernel/syscall.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/syscall.c b/kernel/syscall.c
index 95b9f70..dd7a33e 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -12,7 +12,7 @@ int
 fetchaddr(uint64 addr, uint64 *ip)
 {
   struct proc *p = myproc();
-  if(addr >= p->sz || addr+sizeof(uint64) > p->sz)
+  if(addr >= p->sz || addr+sizeof(uint64) > p->sz) // both tests needed, in case of overflow
     return -1;
   if(copyin(p->pagetable, (char *)ip, addr, sizeof(*ip)) != 0)
     return -1;
@@ -25,9 +25,8 @@ int
 fetchstr(uint64 addr, char *buf, int max)
 {
   struct proc *p = myproc();
-  int err = copyinstr(p->pagetable, buf, addr, max);
-  if(err < 0)
-    return err;
+  if(copyinstr(p->pagetable, buf, addr, max) < 0)
+    return -1;
   return strlen(buf);
 }