1 files changed, 50 insertions, 0 deletions
diff --git a/arch/arm64/lib/clear_user.S b/arch/arm64/lib/clear_user.S
new file mode 100644
index 000000000..48a3a26ef
--- /dev/null
+++ b/arch/arm64/lib/clear_user.S
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Based on arch/arm/lib/clear_user.S
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ */
+#include <linux/linkage.h>
+
+#include <asm/asm-uaccess.h>
+#include <asm/assembler.h>
+
+	.text
+
+/* Prototype: int __arch_clear_user(void *addr, size_t sz)
+ * Purpose  : clear some user memory
+ * Params   : addr - user memory address to clear
+ *          : sz   - number of bytes to clear
+ * Returns  : number of bytes NOT cleared
+ *
+ * Alignment fixed up by hardware.
+ */
+SYM_FUNC_START(__arch_clear_user)
+	mov	x2, x1			// save the size for fixup return
+	subs	x1, x1, #8
+	b.mi	2f
+1:
+uao_user_alternative 9f, str, sttr, xzr, x0, 8
+	subs	x1, x1, #8
+	b.pl	1b
+2:	adds	x1, x1, #4
+	b.mi	3f
+uao_user_alternative 9f, str, sttr, wzr, x0, 4
+	sub	x1, x1, #4
+3:	adds	x1, x1, #2
+	b.mi	4f
+uao_user_alternative 9f, strh, sttrh, wzr, x0, 2
+	sub	x1, x1, #2
+4:	adds	x1, x1, #1
+	b.mi	5f
+uao_user_alternative 9f, strb, sttrb, wzr, x0, 0
+5:	mov	x0, #0
+	ret
+SYM_FUNC_END(__arch_clear_user)
+EXPORT_SYMBOL(__arch_clear_user)
+
+	.section .fixup,"ax"
+	.align	2
+9:	mov	x0, x2			// return the original size
+	ret
+	.previous