diff --git a/user/usertests.c b/user/usertests.c
index aefbc9f..bdf6970 100644
--- a/user/usertests.c
+++ b/user/usertests.c
@@ -22,6 +22,92 @@
 char buf[BUFSZ];
 char name[3];
 
+void
+copyin1(char *s)
+{
+  int fd = open("copyin1", O_CREATE|O_WRONLY);
+  if(fd < 0){
+    printf("open(copyin1) failed\n");
+    exit(1);
+  }
+  int n = write(fd, (void*)0x80000000LL, 8192);
+  if(n >= 0){
+    printf("write(fd, 0x80000000LL, 8192) did not fail!\n");
+    exit(1);
+  }
+  close(fd);
+  unlink("copyin1");
+}
+
+void
+copyin2(char *s)
+{
+  int fd = open("copyin2", O_CREATE|O_WRONLY);
+  if(fd < 0){
+    printf("open(copyin2) failed\n");
+    exit(1);
+  }
+  int n = write(fd, (void*)0xffffffffffffffffLL, 8192);
+  if(n >= 0){
+    printf("write(fd, 0xffffffffffffffffLL, 8192) did not fail!\n");
+    exit(1);
+  }
+  close(fd);
+  unlink("copyin2");
+}
+
+void
+copyout1(char *s)
+{
+  int fd = open("README", 0);
+  if(fd < 0){
+    printf("open(README) failed\n");
+    exit(1);
+  }
+  int n = read(fd, (void*)0x80000000LL, 8192);
+  if(n >= 0){
+    printf("read(fd, 0x80000000LL, 8192) returned %d, not -1\n", n);
+    exit(1);
+  }
+  close(fd);
+}
+
+void
+copyout2(char *s)
+{
+  int fd = open("README", 0);
+  if(fd < 0){
+    printf("open(README) failed\n");
+    exit(1);
+  }
+  int n = read(fd, (void*)0xffffffffffffffffLL, 8192);
+  if(n >= 0){
+    printf("read(fd, 0xffffffffffffffff, 8192) returned %d, not -1\n", n);
+    exit(1);
+  }
+  close(fd);
+}
+
+void
+copyinstr1(char *s)
+{
+  int fd = open((char *)0x80000000LL, O_CREATE|O_WRONLY);
+  if(fd >= 0){
+    printf("open(0x80000000) returned %d, not -1\n", fd);
+    exit(1);
+  }
+}
+
+void
+copyinstr2(char *s)
+{
+  int fd = open((char *)0xffffffffffffffff, O_CREATE|O_WRONLY);
+  if(fd >= 0){
+    printf("open(0xffffffffffffffff) returned %d, not -1\n", fd);
+    exit(1);
+  }
+}
+
 // test O_TRUNC.
 void
 truncate1(char *s)
@@ -2307,6 +2393,12 @@ main(int argc, char *argv[])
     void (*f)(char *);
     char *s;
   } tests[] = {
+    {copyin1, "copyin1"},
+    {copyin2, "copyin2"},
+    {copyout1, "copyout1"},
+    {copyout2, "copyout2"},
+    {copyinstr1, "copyinstr1"},
+    {copyinstr2, "copyinstr2"},
     {truncate1, "truncate1"},
     {truncate2, "truncate2"},
     {truncate3, "truncate3"},