Index: lib/libpuffs/callcontext.c
===================================================================
RCS file: /cvsroot/src/lib/libpuffs/callcontext.c,v
retrieving revision 1.26
diff -u -p -u -r1.26 callcontext.c
--- lib/libpuffs/callcontext.c	2 Nov 2011 16:43:04 -0000	1.26
+++ lib/libpuffs/callcontext.c	6 Dec 2011 18:19:53 -0000
@@ -201,7 +201,11 @@ slowccalloc(struct puffs_usermount *pu)
 	pcc = sp;
 	memset(pcc, 0, sizeof(struct puffs_cc));
 
+#ifndef __MACHINE_STACK_GROWS_UP
 	mprotect((uint8_t *)sp + psize, (size_t)psize, PROT_NONE);
+#else
+	mprotect((uint8_t *)sp + stacksize - psize, (size_t)psize, PROT_NONE);
+#endif
 
 	/* initialize both ucontext's */
 	if (getcontext(&pcc->pcc_uc) == -1) {
@@ -245,6 +249,8 @@ puffs__cc_create(struct puffs_usermount 
 		pcc->pcc_func = func;
 		pcc->pcc_farg = pcc;
 	} else {
+		const long psize = sysconf(_SC_PAGESIZE);
+
 		/* link context */
 		pcc->pcc_uc.uc_link = &pcc->pcc_uc_ret;
 
@@ -254,8 +260,8 @@ puffs__cc_create(struct puffs_usermount 
 		 * swapcontext().  However, it gets lost.  So reinit it.
 		 */
 		st = &pcc->pcc_uc.uc_stack;
-		st->ss_sp = pcc;
-		st->ss_size = stacksize;
+		st->ss_sp = ((uint8_t *)(void *)pcc) + psize;
+		st->ss_size = stacksize - psize;
 		st->ss_flags = 0;
 
 		/*