[PATCH 2/2] x86: Default to vsyscall=emulate

[Andy Lutomirski]

This reverts commit 2b666859ec323403ac9a3a441d16eab30945404b.  The
ABI breakage should be fixed by:

commit 48c4206f5b02f28c4c78a1f5b491d3772fb64fb9
Author: Andy Lutomirski <luto@xxxxxxx>
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@xxxxxxxxxxxxxx>
---
 Documentation/kernel-parameters.txt |    7 +++----
 arch/x86/kernel/vsyscall_64.c       |    2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index d6e6724..854ed5ca 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2706,11 +2706,10 @@ 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 9b05546..02e980a 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -56,7 +56,7 @@ 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)
 {
-- 
1.7.6.4

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