Properly align the stack using _STACKALIGNBYTES, rather that the ALIGN()

macro which is unaware that stacks may need larger alignment.  This may
mean that some workarounds in crt0 can go away (here's looking at you
mips64..)
Tested on about half the architectures (the most special cases), so let's
see what happens.
with tobiasu

1 files changed, 10 insertions, 11 deletions

diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 68b237ef786..a6faedd19fe 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_exec.c,v 1.137 2014/01/21 01:48:44 tedu Exp $	*/
+/*	$OpenBSD: kern_exec.c,v 1.138 2014/03/19 00:01:56 deraadt Exp $	*/
 /*	$NetBSD: kern_exec.c,v 1.75 1996/02/09 18:59:28 christos Exp $	*/
 
 /*-
@@ -81,9 +81,8 @@
 int exec_sigcode_map(struct proc *, struct emul *);
 
 /*
- * stackgap_random specifies if the stackgap should have a random size added
- * to it. Must be a n^2. If non-zero, the stack gap will be calculated as:
- * (arc4random() * ALIGNBYTES) & (stackgap_random - 1) + STACKGAPLEN.
+ * If non-zero, stackgap_random specifies the upper limit of the random gap size
+ * added to the fixed stack gap. Must be n^2.
  */
 int stackgap_random = STACKGAP_RANDOM;
 
@@ -391,19 +390,19 @@ sys_execve(struct proc *p, void *v, register_t *retval)
 		}
 	}
 
-	dp = (char *)ALIGN(dp);
+	dp = (char *)(((long)dp + _STACKALIGNBYTES) & ~_STACKALIGNBYTES);
 
 	sgap = STACKGAPLEN;
-	if (stackgap_random != 0)
-		sgap += (arc4random() * ALIGNBYTES) & (stackgap_random - 1);
-#ifdef MACHINE_STACK_GROWS_UP
-	sgap = ALIGN(sgap);
-#endif
+	if (stackgap_random != 0) {
+		sgap += arc4random() & (stackgap_random - 1);
+		sgap = (sgap + _STACKALIGNBYTES) & ~_STACKALIGNBYTES;
+	}
+
 	/* Now check if args & environ fit into new stack */
 	len = ((argc + envc + 2 + pack.ep_emul->e_arglen) * sizeof(char *) +
 	    sizeof(long) + dp + sgap + sizeof(struct ps_strings)) - argp;
 
-	len = ALIGN(len);	/* make the stack "safely" aligned */
+	len = (len + _STACKALIGNBYTES) &~ _STACKALIGNBYTES;
 
 	if (len > pack.ep_ssize) { /* in effect, compare to initial limit */
 		error = ENOMEM;