riscv: provide memmove implementation

The memmove used by the kernel feature like KASAN.

Signed-off-by: Nick Hu <nickhu@andestech.com>
Signed-off-by: Nick Hu <nick650823@gmail.com>
Signed-off-by: Nylon Chen <nylon7@andestech.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/include/asm/string.h

@@ -12,16 +12,16 @@
 #define __HAVE_ARCH_MEMSET
 extern asmlinkage void *memset(void *, int, size_t);
 extern asmlinkage void *__memset(void *, int, size_t);
-
 #define __HAVE_ARCH_MEMCPY
 extern asmlinkage void *memcpy(void *, const void *, size_t);
 extern asmlinkage void *__memcpy(void *, const void *, size_t);
-
+#define __HAVE_ARCH_MEMMOVE
+extern asmlinkage void *memmove(void *, const void *, size_t);
+extern asmlinkage void *__memmove(void *, const void *, size_t);
 /* For those files which don't want to check by kasan. */
 #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
-
 #define memcpy(dst, src, len) __memcpy(dst, src, len)
 #define memset(s, c, n) __memset(s, c, n)
-
+#define memmove(dst, src, len) __memmove(dst, src, len)
 #endif
 #endif /* _ASM_RISCV_STRING_H */

arch/riscv/kernel/riscv_ksyms.c

@@ -11,5 +11,7 @@
  */
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memcpy);
+EXPORT_SYMBOL(memmove);
 EXPORT_SYMBOL(__memset);
 EXPORT_SYMBOL(__memcpy);
+EXPORT_SYMBOL(__memmove);

arch/riscv/lib/Makefile

@@ -2,5 +2,6 @@
 lib-y			+= delay.o
 lib-y			+= memcpy.o
 lib-y			+= memset.o
+lib-y			+= memmove.o
 lib-$(CONFIG_MMU)	+= uaccess.o
 lib-$(CONFIG_64BIT)	+= tishift.o

arch/riscv/lib/memmove.S

@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+
+ENTRY(__memmove)
+WEAK(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)