recvmmsg

receive multiple messages on a socket

sys_recvmmsg(int fd, struct mmsghdr *mmsg, unsigned int vlen, unsigned int flags, struct __kernel_timespec *timeout)

register	value
`a7`	243, the syscall number
`a0`	int fd
`a1`	struct mmsghdr *mmsg
`a2`	unsigned int vlen
`a3`	unsigned int flags
`a4`	struct __kernel_timespec *timeout
`a0`	the return value

Then run ecall to enter the kernel.

Same syscall on other architectures