how does this command(at+cfun=1,1) works?

Hi Everyone, When this command (at+cfun=1,1) is executed on phone, it does a reboot. I want to know which and how this command calls the kernel level functions. I googled this, but seems like all the data explains only about AT command and not as to how this reboot process is done. Coz what I know is that reboot process needs a syncing of filesystem, so this command must be calling some kernel functions to do that. Please if anyone can give more detail on this. Thank you Ritesh