> libc/sysdeps/mach/hurd/ioctl.c is where the `ioctl' function is > defined. Try following its execution.
Is that a dare? ;-) This particular function is not for the faint of heart. Each distinct ioctl request on an fd (except for FIO*, which are special cases handled in libc/hurd/hurdioctl.c) is transmogrified into an RPC on the io port underlying the fd. Currently the only example of a set of such RPCs that are actually implemented is TIOC*, see <hurd/tioctl.defs>. To get a start on understanding, imagine for example that tcgetattr instead of calling ioctl(,TIOCGETA,) did the equivalent thing of using the MiG stub tioctl_tiocgeta. > How did I know this? I already knew that libc/sysdeps/mach/hurd and > libc/hurd are generally the places to look when you want to start > understanding how a C library call is implemented on the Hurd, so I > just looked for files named '*ioctl*' in those directories. I cannot recommend highly enough using glimpseindex on each and every source tree you hack on, and using glimpse as casually as you use your eyelids (M-x grep works great with glimpse -n).
