[PATCH v2 0/3] x86_64: Tidy up vsyscall emulation and make it optional

[Andy Lutomirski <luto@amacapital.net>]

Now that arch/x86/kernel/vsyscall_64.c contains only vsyscall
emulation code, clean it up and make it optional.

Patch 1 makes vsyscall=none work be a bit more self-consistent: it
actually removes the fake vsyscall page instead of just segfaulting
anyone who tries to use it.

Patch 2 is pure cosmetic cleanup.

Patch 3 is the meat: it lets vsyscall emulation be configured out.
The config option to disable it is hidden under CONFIG_EXPERT, since
it will break legacy code.

Note that, last I checked, current userspace is unlikely to work if
the vDSO *and* vsyscalls are off.  Take it up with the glibc
maintainers.

This applies on top of tip/x86/vdso.

Changes from v1:
 - Added Josh's Reviewed-by
 - Fixup up Xen bits in patch 3

Andy Lutomirski (3):
  x86_64,vsyscall: Turn vsyscalls all the way off when vsyscall=none
  x86_64,vsyscall: Rewrite comment and clean up headers in vsyscall code
  x86_64,vsyscall: Make vsyscall emulation configurable

 arch/x86/Kconfig                | 18 ++++++++++++
 arch/x86/include/asm/fixmap.h   |  2 ++
 arch/x86/include/asm/page_64.h  |  4 ++-
 arch/x86/include/asm/vsyscall.h |  8 +++++
 arch/x86/kernel/Makefile        |  3 +-
 arch/x86/kernel/setup.c         |  2 --
 arch/x86/kernel/vsyscall_64.c   | 65 +++++++++++++++++------------------------
 arch/x86/xen/mmu.c              |  6 ++--
 8 files changed, 63 insertions(+), 45 deletions(-)

-- 
1.9.3