> This adds configurable sysenter support on x86. This saves about 5k on
> small systems.

You not only remove the sysenter support but also the vdso.  And the
later is a very bad idea.  It is already today basically impossible to
have reliable backtraces without the vdso and the unwind info it
contains for signal handlers.  And things can only get worse in future.
 The magic heuristics in the compiler are not reliable.  It's simply the
wrong face, this in a interface between the kernel and the libc, the
compiler should not have such knowledge.

The vdso should be mandatory for all configurations.

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖