__asm__ __volatile()

in include/asm/futex.h [25:114]

• 85 lines of code
• 9 McCabe index (conditional complexity)

	__asm__ __volatile(				\
	"1:	l32ex	%[oldval], %[addr]\n"		\
		insn "\n"				\
	"2:	s32ex	%[newval], %[addr]\n"		\
	"	getex	%[newval]\n"			\
	"	beqz	%[newval], 1b\n"		\
	"	movi	%[newval], 0\n"			\
	"3:\n"						\
	"	.section .fixup,\"ax\"\n"		\
	"	.align 4\n"				\
	"	.literal_position\n"			\
	"5:	movi	%[oldval], 3b\n"		\
	"	movi	%[newval], %[fault]\n"		\
	"	jx	%[oldval]\n"			\
	"	.previous\n"				\
	"	.section __ex_table,\"a\"\n"		\
	"	.long 1b, 5b, 2b, 5b\n"			\
	"	.previous\n"				\
	: [oldval] "=&r" (old), [newval] "=&r" (ret)	\
	: [addr] "r" (uaddr), [oparg] "r" (arg),	\
	  [fault] "I" (-EFAULT)				\
	: "memory")
#elif XCHAL_HAVE_S32C1I
#define __futex_atomic_op(insn, ret, old, uaddr, arg)	\
	__asm__ __volatile(				\
	"1:	l32i	%[oldval], %[mem]\n"		\
		insn "\n"				\
	"	wsr	%[oldval], scompare1\n"		\
	"2:	s32c1i	%[newval], %[mem]\n"		\
	"	bne	%[newval], %[oldval], 1b\n"	\
	"	movi	%[newval], 0\n"			\
	"3:\n"						\
	"	.section .fixup,\"ax\"\n"		\
	"	.align 4\n"				\
	"	.literal_position\n"			\
	"5:	movi	%[oldval], 3b\n"		\
	"	movi	%[newval], %[fault]\n"		\
	"	jx	%[oldval]\n"			\
	"	.previous\n"				\
	"	.section __ex_table,\"a\"\n"		\
	"	.long 1b, 5b, 2b, 5b\n"			\
	"	.previous\n"				\
	: [oldval] "=&r" (old), [newval] "=&r" (ret),	\
	  [mem] "+m" (*(uaddr))				\
	: [oparg] "r" (arg), [fault] "I" (-EFAULT)	\
	: "memory")
#endif

static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
		u32 __user *uaddr)
{
#if XCHAL_HAVE_S32C1I || XCHAL_HAVE_EXCLUSIVE
	int oldval = 0, ret;

	if (!access_ok(uaddr, sizeof(u32)))
		return -EFAULT;

	switch (op) {
	case FUTEX_OP_SET:
		__futex_atomic_op("mov %[newval], %[oparg]",
				  ret, oldval, uaddr, oparg);
		break;
	case FUTEX_OP_ADD:
		__futex_atomic_op("add %[newval], %[oldval], %[oparg]",
				  ret, oldval, uaddr, oparg);
		break;
	case FUTEX_OP_OR:
		__futex_atomic_op("or %[newval], %[oldval], %[oparg]",
				  ret, oldval, uaddr, oparg);
		break;
	case FUTEX_OP_ANDN:
		__futex_atomic_op("and %[newval], %[oldval], %[oparg]",
				  ret, oldval, uaddr, ~oparg);
		break;
	case FUTEX_OP_XOR:
		__futex_atomic_op("xor %[newval], %[oldval], %[oparg]",
				  ret, oldval, uaddr, oparg);
		break;
	default:
		ret = -ENOSYS;
	}

	if (!ret)
		*oval = oldval;

	return ret;
#else
	return futex_atomic_op_inuser_local(op, oparg, oval, uaddr);
#endif
}