[PATCH 1/2] riscv: Add memmove string operation.

[Nick Hu <nickhu@andestech.com>]

There are some features which need this string operation for compilation,
like KASAN. So the purpose of this porting is for the features like KASAN
which cannot be compiled without it.

KASAN's string operations would replace the original string operations and
call for the architecture defined string operations. Since we don't have
this in current kernel, this patch provides the implementation.

This porting refers to the 'arch/nds32/lib/memmove.S'.

Signed-off-by: Nick Hu <nickhu@andestech.com>
---
 arch/riscv/include/asm/string.h |    3 ++
 arch/riscv/kernel/riscv_ksyms.c |    1 +
 arch/riscv/lib/Makefile         |    1 +
 arch/riscv/lib/memmove.S        |   63 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 0 deletions(-)
 create mode 100644 arch/riscv/lib/memmove.S

diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h
index 1b5d445..11210f1 100644
--- a/arch/riscv/include/asm/string.h
+++ b/arch/riscv/include/asm/string.h
@@ -15,4 +15,7 @@
 #define __HAVE_ARCH_MEMCPY
 extern asmlinkage void *memcpy(void *, const void *, size_t);
 
+#define __HAVE_ARCH_MEMMOVE
+extern asmlinkage void *memmove(void *, const void *, size_t);
+
 #endif /* _ASM_RISCV_STRING_H */
diff --git a/arch/riscv/kernel/riscv_ksyms.c b/arch/riscv/kernel/riscv_ksyms.c
index 4800cf7..ffabaf1 100644
--- a/arch/riscv/kernel/riscv_ksyms.c
+++ b/arch/riscv/kernel/riscv_ksyms.c
@@ -14,3 +14,4 @@
 EXPORT_SYMBOL(__asm_copy_from_user);
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memcpy);
+EXPORT_SYMBOL(memmove);
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 8e364eb..9a4d5b3 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -2,6 +2,7 @@
 lib-y	+= delay.o
 lib-y	+= memcpy.o
 lib-y	+= memset.o
+lib-y	+= memmove.o
 lib-y	+= uaccess.o
 
 lib-$(CONFIG_64BIT) += tishift.o
diff --git a/arch/riscv/lib/memmove.S b/arch/riscv/lib/memmove.S
new file mode 100644
index 0000000..3657a06
--- /dev/null
+++ b/arch/riscv/lib/memmove.S
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+
+ENTRY(memmove)
+	move	t0, a0
+	move	t1, a1
+
+	beq 	a0, a1, exit_memcpy
+	beqz	a2, exit_memcpy
+	srli	t2, a2, 0x2
+
+	slt	t3, a0, a1
+	beqz	t3, do_reverse
+
+	andi	a2, a2, 0x3
+	li	t4, 1
+	beqz	t2, byte_copy
+
+word_copy:
+	lw	t3, 0(a1)
+	addi	t2, t2, -1
+	addi	a1, a1, 4
+	sw	t3, 0(a0)
+	addi	a0, a0, 4
+	bnez	t2, word_copy
+	beqz	a2, exit_memcpy
+	j	byte_copy
+
+do_reverse:
+	add	a0, a0, a2
+	add	a1, a1, a2
+	andi	a2, a2, 0x3
+	li	t4, -1
+	beqz	t2, reverse_byte_copy
+
+reverse_word_copy:
+	addi	a1, a1, -4
+	addi	t2, t2, -1
+	lw	t3, 0(a1)
+	addi	a0, a0, -4
+	sw	t3, 0(a0)
+	bnez	t2, reverse_word_copy
+	beqz	a2, exit_memcpy
+
+reverse_byte_copy:
+	addi	a0, a0, -1
+	addi	a1, a1, -1
+byte_copy:
+	lb	t3, 0(a1)
+	addi	a2, a2, -1
+	sb	t3, 0(a0)
+	add	a1, a1, t4
+	add	a0, a0, t4
+	bnez	a2, byte_copy
+
+exit_memcpy:
+	move a0, t0
+	move a1, t1
+	ret
+
+END(memmove)
-- 
1.7.1