x86: Default to vsyscall=emulate

This essentially reverts:

  2b666859ec32: x86: Default to vsyscall=native for now

The ABI breakage should now be fixed by:

 commit 48c4206f5b02f28c4c78a1f5b491d3772fb64fb9
 Author: Andy Lutomirski <luto@mit.edu>
 Date:   Thu Oct 20 08:48:19 2011 -0700

    x86-64: Set siginfo and context on vsyscall emulation faults

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: richard -rw- weinberger <richard.weinberger@gmail.com>
Cc: Adrian Bunk <bunk@stusta.de>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/93154af3b2b6d208906ae02d80d92cf60c6fa94f.1320712291.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a0c5c5f..ce7fc8b 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2750,11 +2750,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        functions are at fixed addresses, they make nice
                        targets for exploits that can control RIP.
 
-                       emulate     Vsyscalls turn into traps and are emulated
-                                   reasonably safely.
+                       emulate     [default] Vsyscalls turn into traps and are
+                                   emulated reasonably safely.
 
-                       native      [default] Vsyscalls are native syscall
-                                   instructions.
+                       native      Vsyscalls are native syscall instructions.
                                    This is a little bit faster than trapping
                                    and makes a few dynamic recompilers work
                                    better than they would in emulation mode.

diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 8084bec..b07ba93 100644 (file)
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -57,7 +57,7 @@ DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data) =
        .lock = __SEQLOCK_UNLOCKED(__vsyscall_gtod_data.lock),
 };
 
-static enum { EMULATE, NATIVE, NONE } vsyscall_mode = NATIVE;
+static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
 
 static int __init vsyscall_setup(char *str)
 {