x86-64: vsyscall emulation cleanups

[cc list trimmed from the previous patches to include only people who seem
like they would care about this round of changes. My apologies if I missed anyone.]

This series applies to the x86/vdso branch of the -tip tree.

Patch 1/3 deletes some very outdated comments in vsyscall_64.c.

Patch 2/3 simplifies the vsyscall emulation int 0xcc mechanism and removes some ret instructions that are (as pointed out by the PaX team) possibly dangerous.

Patch 3/3 fixes what is arguably the most serious problem of all: people thought that CONFIG_COMPAT_VSYSCALLS controlled binary compatibility. It changes the Kconfig short description, help text, and feature removal entry to make it a lot more clear what's going on.

Andy Lutomirski (3):
x86-64: Fix outdated comments in vsyscall_64.c
x86-64: Clean up vsyscall emulation and remove fixed-address ret
x86-64: Clarify CONFIG_COMPAT_VSYSCALLS text

 Documentation/feature-removal-schedule.txt |   11 ++-
 arch/x86/Kconfig                           |   27 +++++----
 arch/x86/include/asm/vsyscall.h            |   10 +++-
 arch/x86/kernel/vsyscall_64.c              |   85 +++++++++-------------------
 arch/x86/kernel/vsyscall_emu_64.S          |   17 +-----
 5 files changed, 58 insertions(+), 92 deletions(-)

1.7.5.2