dev-libs/glib-2.30 has optional support for systemtap and dtrace, please keyword dev-util/systemtap-1.6 I've temporarily masked USE=systemtap in base/package.use.mask and unmasked it only for amd64/x86. If you don't want systemtap support, please *also* mask it in your profile, because I'll remove the base/ mask in a month or so. Note that systemtap requires kernel support (see ebuild). Thanks!
[CCing arches, forgot initially] Not adding alpha or hppa because according to investigation by plaes, they don't have kprobes support in the kernel. Arches, please see the previous comment, thanks!
*** This bug has been marked as a duplicate of bug 351931 ***