diff --git a/xen/arch/arm/arm32/lib/memchr.S b/xen/arch/arm/arm32/lib/memchr.S
index 7dae4ab6a6..f38374a43e 100644
--- a/xen/arch/arm/arm32/lib/memchr.S
+++ b/xen/arch/arm/arm32/lib/memchr.S
@@ -14,6 +14,7 @@
 	.text
 	.align	5
 ENTRY(memchr)
+	and	r1, r1, #0xff
 1:	subs	r2, r2, #1
 	bmi	2f
 	ldrb	r3, [r0], #1
diff --git a/xen/arch/arm/arm32/lib/memset.S b/xen/arch/arm/arm32/lib/memset.S
index 5a1dadf767..ce82c45910 100644
--- a/xen/arch/arm/arm32/lib/memset.S
+++ b/xen/arch/arm/arm32/lib/memset.S
@@ -15,6 +15,7 @@
 	.align	5
 
 ENTRY(memset)
+	and	r1, r1, #0xff
 	ands	r3, r0, #3		@ 1 unaligned?
 	mov	ip, r0			@ preserve r0 as return value
 	bne	6f			@ 1
diff --git a/xen/arch/arm/arm32/lib/strrchr.S b/xen/arch/arm/arm32/lib/strrchr.S
index ec4d40de5e..374ce3e59d 100644
--- a/xen/arch/arm/arm32/lib/strrchr.S
+++ b/xen/arch/arm/arm32/lib/strrchr.S
@@ -14,6 +14,7 @@
 		.text
 		.align	5
 ENTRY(strrchr)
+		and	r1, r1, #0xff
 		mov	r3, #0
 1:		ldrb	r2, [r0], #1
 		teq	r2, r1