Re: More breakage in native_rdtsc out of line in git-x86 II

I think the problem is that the vsyscall/vdso code calls it through
vread and for that it has to be exported. There seems to be also
another bug with the old style vsyscalls not using the TSC vread
that masks it on older glibc

Stepping with gdb through old style vgettimeofday() confirms that RDTSC is
not used.

A long time ago we had a similar problem once and it was because of a
problem exporting the vsyscall variables in vmlinux.lds.S -- looks like that
has reappeared.

I think the new glibc shows it because it uses the vDSO not
the older vsyscall and the new vDSO probably still works. Anyways haven't
investigated why that is in detail yet, but that's a separate
regression.

Actually that seems to be because the test system using the older
glibc didn't use the TSC because it was marked unstable due a
unsynchronized TSC. It should not have been -- this is a Core2
dual core single socket. Will investigate later what happened
there.

-Andi
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