2 files changed, 33 insertions, 0 deletions
diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h
index e5ccb926c903..aece7d895153 100644
--- a/tools/include/nolibc/arch-x86_64.h
+++ b/tools/include/nolibc/arch-x86_64.h
@@ -173,4 +173,33 @@ void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
 	__builtin_unreachable();
 }
 
+#define NOLIBC_ARCH_HAS_MEMMOVE
+void *memmove(void *dst, const void *src, size_t len);
+
+#define NOLIBC_ARCH_HAS_MEMCPY
+void *memcpy(void *dst, const void *src, size_t len);
+
+__asm__ (
+".section .text.nolibc_memmove_memcpy\n"
+".weak memmove\n"
+".weak memcpy\n"
+"memmove:\n"
+"memcpy:\n"
+	"movq %rdx, %rcx\n\t"
+	"movq %rdi, %rax\n\t"
+	"movq %rdi, %rdx\n\t"
+	"subq %rsi, %rdx\n\t"
+	"cmpq %rcx, %rdx\n\t"
+	"jb   .Lbackward_copy\n\t"
+	"rep movsb\n\t"
+	"retq\n"
+".Lbackward_copy:"
+	"leaq -1(%rdi, %rcx, 1), %rdi\n\t"
+	"leaq -1(%rsi, %rcx, 1), %rsi\n\t"
+	"std\n\t"
+	"rep movsb\n\t"
+	"cld\n\t"
+	"retq\n"
+);
+
 #endif /* _NOLIBC_ARCH_X86_64_H */
diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
index 0c2e06c7c477..6eca267ec6fa 100644
--- a/tools/include/nolibc/string.h
+++ b/tools/include/nolibc/string.h
@@ -49,6 +49,7 @@ void *_nolibc_memcpy_down(void *dst, const void *src, size_t len)
 	return dst;
 }
 
+#ifndef NOLIBC_ARCH_HAS_MEMMOVE
 /* might be ignored by the compiler without -ffreestanding, then found as
  * missing.
  */
@@ -72,13 +73,16 @@ void *memmove(void *dst, const void *src, size_t len)
 	}
 	return dst;
 }
+#endif /* #ifndef NOLIBC_ARCH_HAS_MEMMOVE */
 
+#ifndef NOLIBC_ARCH_HAS_MEMCPY
 /* must be exported, as it's used by libgcc on ARM */
 __attribute__((weak,unused,section(".text.nolibc_memcpy")))
 void *memcpy(void *dst, const void *src, size_t len)
 {
 	return _nolibc_memcpy_up(dst, src, len);
 }
+#endif /* #ifndef NOLIBC_ARCH_HAS_MEMCPY */
 
 /* might be ignored by the compiler without -ffreestanding, then found as
  * missing.