just thinking about it.
Two changes need to be made to allow 'config kernel swap generic' to
work properly without requiring any compile-time flags:
/usr/src/usr.sbin/config/mkswapconf.c: we need to define a dummy stub
for the setconf() function to replace the one in swapgeneric.c that
isn't available in non-generic configurations.
/usr/src/sys/i386/i386/autoconf.c: the -a boot flag causes setroot()
to be skipped and lets setconf() prompt the user for a root device.
If you skip setroot() in a non-generic kernel, you could get severely
hosed. To avoid this, we silently ignore the -a flag if rootdev != NODEV.
(rootdev is always initialized to NODEV in swapgeneric.c, so if
we find that rootdev is something other than NODEV, we know we're
not using a generic configuration.)