xen: arm32: add optimised strchr and strrchr routines

Taken from Linux v3.14-rc7.

These aren't widely used enough to be critical, but we may as well have them.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Tim Deegan <tim@xen.org>

xen/arch/arm/arm32/lib/Makefile

@@ -2,4 +2,5 @@ obj-y += memcpy.o memmove.o memset.o memchr.o memzero.o
 obj-y += findbit.o setbit.o
 obj-y += setbit.o clearbit.o changebit.o
 obj-y += testsetbit.o testclearbit.o testchangebit.o
+obj-y += strchr.o strrchr.o
 obj-y += lib1funcs.o lshrdi3.o div64.o

xen/arch/arm/arm32/lib/strchr.S

@@ -0,0 +1,29 @@
+/*
+ *  linux/arch/arm/lib/strchr.S
+ *
+ *  Copyright (C) 1995-2000 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ *  ASM optimised string functions
+ */
+
+#include <xen/config.h>
+
+#include "assembler.h"
+
+		.text
+		.align	5
+ENTRY(strchr)
+		and	r1, r1, #0xff
+1:		ldrb	r2, [r0], #1
+		teq	r2, r1
+		teqne	r2, #0
+		bne	1b
+		teq	r2, r1
+		movne	r0, #0
+		subeq	r0, r0, #1
+		mov	pc, lr
+ENDPROC(strchr)

xen/arch/arm/arm32/lib/strrchr.S

@@ -0,0 +1,28 @@
+/*
+ *  linux/arch/arm/lib/strrchr.S
+ *
+ *  Copyright (C) 1995-2000 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ *  ASM optimised string functions
+ */
+
+#include <xen/config.h>
+
+#include "assembler.h"
+
+		.text
+		.align	5
+ENTRY(strrchr)
+		mov	r3, #0
+1:		ldrb	r2, [r0], #1
+		teq	r2, r1
+		subeq	r3, r0, #1
+		teq	r2, #0
+		bne	1b
+		mov	r0, r3
+		mov	pc, lr
+ENDPROC(strrchr)

xen/include/asm-arm/string.h

@@ -4,6 +4,18 @@
 #include <xen/config.h>
 
 #if defined(CONFIG_ARM_32)
+
+/*
+ * We don't do inline string functions, since the
+ * optimised inline asm versions are not small.
+ */
+
+#define __HAVE_ARCH_STRRCHR
+extern char * strrchr(const char * s, int c);
+
+#define __HAVE_ARCH_STRCHR
+extern char * strchr(const char * s, int c);
+
 #define __HAVE_ARCH_MEMCPY
 extern void * memcpy(void *, const void *, __kernel_size_t);