X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Ftests%2Fuserprog%2Fsc-bad-arg.c;h=0b512a0e59797e0e7e3ae006d44dea83710d2508;hb=a03618133f7df0954802a470a4bee7674f7aed45;hp=2df966f3e623b8d03968652333d66001dace358a;hpb=615bf3b3d2a8573ed6fb9ddc0055745e163ac999;p=pintos-anon

diff --git a/src/tests/userprog/sc-bad-arg.c b/src/tests/userprog/sc-bad-arg.c
index 2df966f..0b512a0 100644
--- a/src/tests/userprog/sc-bad-arg.c
+++ b/src/tests/userprog/sc-bad-arg.c
@@ -1,3 +1,9 @@
+/* Sticks a system call number (SYS_EXIT) at the very top of the
+   stack, then invokes a system call with the stack pointer
+   (%esp) set to its address.  The process must be terminated
+   with -1 exit code because the argument to the system call
+   would be above the top of the user address space. */
+
 #include <syscall-nr.h>
 #include "tests/lib.h"
 #include "tests/main.h"
@@ -5,7 +11,7 @@
 void
 test_main (void) 
 {
-  asm volatile ("mov %%esp, 0xbffffffc; mov [dword ptr %%esp], %0; int 0x30"
-                :: "i" (SYS_exit));
+  asm volatile ("movl $0xbffffffc, %%esp; movl %0, (%%esp); int $0x30"
+                : : "i" (SYS_EXIT));
   fail ("should have called exit(-1)");
 }