futex_waitv

wait for FUTEX_WAKE operation on a vector of futexes

sys_futex_waitv(struct futex_waitv *waiters, unsigned int nr_futexes, unsigned int flags, struct __kernel_timespec *timeout, clockid_t clockid)

register	value
`x8`	449, the syscall number
`x0`	struct futex_waitv *waiters
`x1`	unsigned int nr_futexes
`x2`	unsigned int flags
`x3`	struct __kernel_timespec *timeout
`x4`	clockid_t clockid
`x0`	the return value

Then run svc #0 to enter the kernel.

Same syscall on other architectures