asm volatile()

in include/asm/uaccess.h [292:373]

• 78 lines of code
• 12 McCabe index (conditional complexity)

	asm volatile ("\n"						\
		"	move."#s1"	(%2)+,%3\n"			\
		"11:	"MOVES"."#s1"	%3,(%1)+\n"			\
		"12:	move."#s2"	(%2)+,%3\n"			\
		"21:	"MOVES"."#s2"	%3,(%1)+\n"			\
		"22:\n"							\
		"	.ifnc	\""#s3"\",\"\"\n"			\
		"	move."#s3"	(%2)+,%3\n"			\
		"31:	"MOVES"."#s3"	%3,(%1)+\n"			\
		"32:\n"							\
		"	.endif\n"					\
		"4:\n"							\
		"\n"							\
		"	.section __ex_table,\"a\"\n"			\
		"	.align	4\n"					\
		"	.long	11b,5f\n"				\
		"	.long	12b,5f\n"				\
		"	.long	21b,5f\n"				\
		"	.long	22b,5f\n"				\
		"	.ifnc	\""#s3"\",\"\"\n"			\
		"	.long	31b,5f\n"				\
		"	.long	32b,5f\n"				\
		"	.endif\n"					\
		"	.previous\n"					\
		"\n"							\
		"	.section .fixup,\"ax\"\n"			\
		"	.even\n"					\
		"5:	moveq.l	#"#n",%0\n"				\
		"	jra	4b\n"					\
		"	.previous\n"					\
		: "+d" (res), "+a" (to), "+a" (from), "=&d" (tmp)	\
		: : "memory")

static __always_inline unsigned long
__constant_copy_to_user(void __user *to, const void *from, unsigned long n)
{
	unsigned long res = 0, tmp;

	switch (n) {
	case 1:
		__put_user_asm(MOVES, res, *(u8 *)from, (u8 __user *)to,
				b, d, 1);
		break;
	case 2:
		__put_user_asm(MOVES, res, *(u16 *)from, (u16 __user *)to,
				w, r, 2);
		break;
	case 3:
		__constant_copy_to_user_asm(res, to, from, tmp, 3, w, b,);
		break;
	case 4:
		__put_user_asm(MOVES, res, *(u32 *)from, (u32 __user *)to,
				l, r, 4);
		break;
	case 5:
		__constant_copy_to_user_asm(res, to, from, tmp, 5, l, b,);
		break;
	case 6:
		__constant_copy_to_user_asm(res, to, from, tmp, 6, l, w,);
		break;
	case 7:
		__constant_copy_to_user_asm(res, to, from, tmp, 7, l, w, b);
		break;
	case 8:
		__constant_copy_to_user_asm(res, to, from, tmp, 8, l, l,);
		break;
	case 9:
		__constant_copy_to_user_asm(res, to, from, tmp, 9, l, l, b);
		break;
	case 10:
		__constant_copy_to_user_asm(res, to, from, tmp, 10, l, l, w);
		break;
	case 12:
		__constant_copy_to_user_asm(res, to, from, tmp, 12, l, l, l);
		break;
	default:
		/* limit the inlined version to 3 moves */
		return __generic_copy_to_user(to, from, n);
	}

	return res;
}