kexec_load

load a new kernel for later execution

sys_kexec_load(unsigned long entry, unsigned long nr_segments, struct kexec_segment *segments, unsigned long flags)

register	value
`v0`	448, the syscall number
`a0`	unsigned long entry
`a1`	unsigned long nr_segments
`a2`	struct kexec_segment *segments
`a3`	unsigned long flags
`v0`	the return value

Then run callsys to enter the kernel.

Same syscall on other architectures