Add nosegneg capability to the vsyscall page notes
authorJeremy Fitzhardinge <jeremy@xensource.com>
Wed, 18 Jul 2007 01:37:04 +0000 (18:37 -0700)
committerJeremy Fitzhardinge <jeremy@goop.org>
Wed, 18 Jul 2007 15:47:42 +0000 (08:47 -0700)
commit24037a8b69dbf15bfed8fd42a2a2e442d7b0395b
tree317e7d21bd253200aa09a7b1551d03c1e3985cc0
parent688340ea34c61ad12473ccd837325b59aada9a93
Add nosegneg capability to the vsyscall page notes

Add the "nosegneg" fake capabilty to the vsyscall page notes. This is
used by the runtime linker to select a glibc version which then
disables negative-offset accesses to the thread-local segment via
%gs. These accesses require emulation in Xen (because segments are
truncated to protect the hypervisor address space) and avoiding them
provides a measurable performance boost.

Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Acked-by: Zachary Amsden <zach@vmware.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ulrich Drepper <drepper@redhat.com>
arch/i386/kernel/vsyscall-note.S