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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>
This commit is contained in:
Andy Lutomirski 2011-11-07 16:33:41 -08:00 committed by Ingo Molnar
parent 4fc3490114
commit 2e57ae0515
2 changed files with 4 additions and 5 deletions
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7
Documentation/kernel-parameters.txt
View File

@ -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.

2
arch/x86/kernel/vsyscall_64.c
View File

@ -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)
{