arm64: klib: Optimised string functions

This patch introduces AArch64-specific string functions (strchr,
strrchr).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/string.h

@@ -16,6 +16,12 @@
 #ifndef __ASM_STRING_H
 #define __ASM_STRING_H
 
+#define __HAVE_ARCH_STRRCHR
+extern char *strrchr(const char *, int c);
+
+#define __HAVE_ARCH_STRCHR
+extern char *strchr(const char *, int c);
+
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *, const void *, __kernel_size_t);
 

arch/arm64/kernel/arm64ksyms.c

@@ -48,6 +48,8 @@ EXPORT_SYMBOL(__atomic_hash);
 EXPORT_SYMBOL(memstart_addr);
 
 	/* string / mem functions */
+EXPORT_SYMBOL(strchr);
+EXPORT_SYMBOL(strrchr);
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memmove);

arch/arm64/lib/Makefile

@@ -2,4 +2,5 @@ lib-y		:= bitops.o delay.o					\
 		   strncpy_from_user.o strnlen_user.o clear_user.o	\
 		   copy_from_user.o copy_to_user.o copy_in_user.o	\
 		   copy_page.o clear_page.o				\
-		   memchr.o memcpy.o memmove.o memset.o
+		   memchr.o memcpy.o memmove.o memset.o			\
+		   strchr.o strrchr.o

arch/arm64/lib/strchr.S

@@ -0,0 +1,42 @@
+/*
+ * Based on arch/arm/lib/strchr.S
+ *
+ * Copyright (C) 1995-2000 Russell King
+ * Copyright (C) 2013 ARM Ltd.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Find the first occurrence of a character in a string.
+ *
+ * Parameters:
+ *	x0 - str
+ *	x1 - c
+ * Returns:
+ *	x0 - address of first occurrence of 'c' or 0
+ */
+ENTRY(strchr)
+	and	w1, w1, #0xff
+1:	ldrb	w2, [x0], #1
+	cmp	w2, w1
+	ccmp	w2, wzr, #4, ne
+	b.ne	1b
+	sub	x0, x0, #1
+	cmp	w2, w1
+	csel	x0, x0, xzr, eq
+	ret
+ENDPROC(strchr)

arch/arm64/lib/strrchr.S

@@ -0,0 +1,43 @@
+/*
+ * Based on arch/arm/lib/strrchr.S
+ *
+ * Copyright (C) 1995-2000 Russell King
+ * Copyright (C) 2013 ARM Ltd.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Find the last occurrence of a character in a string.
+ *
+ * Parameters:
+ *	x0 - str
+ *	x1 - c
+ * Returns:
+ *	x0 - address of last occurrence of 'c' or 0
+ */
+ENTRY(strrchr)
+	mov	x3, #0
+	and	w1, w1, #0xff
+1:	ldrb	w2, [x0], #1
+	cbz	w2, 2f
+	cmp	w2, w1
+	b.ne	1b
+	sub	x3, x0, #1
+	b	1b
+2:	mov	x0, x3
+	ret
+ENDPROC(strrchr)