pacman -Ss kdm doesn't return anything. Did Arch at some point decide to ditch KDM while I didn't look?
/etc/rc.d/kdm doesn't exist?
edit: hmm, a reïnstall off kdebase & kdelibs did the trick. Really weird. It was a fresh KDE and I got no file integrity errors during pacman -S kde.
It's probably due to the pacman bug.