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, 43 insertions, 0 deletions

diff --git a/arch/arm64/lib/strrchr.S b/arch/arm64/lib/strrchr.S
new file mode 100644
index 000000000000..61eabd9a289a
--- /dev/null
+++ b/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)