arm64: klib: Optimised string functions

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

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

1 files changed, 42 insertions, 0 deletions

diff --git a/arch/arm64/lib/strchr.S b/arch/arm64/lib/strchr.S
new file mode 100644
index 000000000000..dae0cf5591f9
--- /dev/null
+++ b/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)