diff --git a/sys/arch/x86/x86/intr.c b/sys/arch/x86/x86/intr.c
index 94d4975a32c5..d0f52fb1a6dc 100644
--- a/sys/arch/x86/x86/intr.c
+++ b/sys/arch/x86/x86/intr.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: intr.c,v 1.29 2007/07/09 20:52:38 ad Exp $	*/
+/*	$NetBSD: intr.c,v 1.30 2007/08/29 22:21:51 dyoung Exp $	*/
 
 /*-
  * Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -140,8 +140,9 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: intr.c,v 1.29 2007/07/09 20:52:38 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: intr.c,v 1.30 2007/08/29 22:21:51 dyoung Exp $");
 
+#include "opt_noredzone.h"
 #include "opt_multiprocessor.h"
 #include "opt_acpi.h"
 
@@ -850,6 +851,16 @@ struct intrhand fake_ipi_intrhand;
 static const char *x86_ipi_names[X86_NIPI] = X86_IPI_NAMES;
 #endif
 
+static inline int
+redzone_const_or_zero(int x)
+{
+#ifdef NOREDZONE
+	return 0;
+#else
+	return x;
+#endif /* !NOREDZONE */
+}
+
 /*
  * Initialize all handlers that aren't dynamically allocated, and exist
  * for each CPU.
@@ -862,7 +873,7 @@ cpu_intr_init(struct cpu_info *ci)
 	int i;
 #endif
 #if defined(INTRSTACKSIZE)
-	char *cp;
+	vaddr_t istack;
 #endif /* defined(INTRSTACKSIZE) */
 
 	MALLOC(isp, struct intrsource *, sizeof (struct intrsource), M_DEVBUF,
@@ -939,8 +950,20 @@ cpu_intr_init(struct cpu_info *ci)
 	intr_calculatemasks(ci);
 
 #if defined(INTRSTACKSIZE)
-	cp = (char *)uvm_km_alloc(kernel_map, INTRSTACKSIZE, 0, UVM_KMF_WIRED);
-	ci->ci_intrstack = cp + INTRSTACKSIZE - sizeof(register_t);
+	/* If the red zone is activated, protect both the top and
+	 * the bottom of the stack with an unmapped page.
+	 */
+	istack = uvm_km_alloc(kernel_map,
+	    INTRSTACKSIZE + redzone_const_or_zero(2 * PAGE_SIZE), 0,
+	    UVM_KMF_WIRED);
+	if (redzone_const_or_zero(1)) {
+		pmap_kremove(istack, PAGE_SIZE);
+		pmap_kremove(istack + INTRSTACKSIZE + PAGE_SIZE, PAGE_SIZE);
+		pmap_update(pmap_kernel());
+	}
+	ci->ci_intrstack =
+	    (char *)istack + redzone_const_or_zero(PAGE_SIZE) + INTRSTACKSIZE -
+	    sizeof(register_t);
 	ci->ci_idepth = -1;
 #endif /* defined(INTRSTACKSIZE) */
 }