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Commit 2b666859 authored by Adrian Bunk's avatar Adrian Bunk Committed by Ingo Molnar
Browse files

x86: Default to vsyscall=native for now 

This UML breakage:

  linux-2.6.30.1[3800] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb9c498 ax:ffffffffff600000 si:0 di:606790
  linux-2.6.30.1[3856] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb13168 ax:ffffffffff600000 si:0 di:606790

Is caused by commit 3ae36655 ("x86-64: Rework vsyscall emulation and add
vsyscall= parameter") - the vsyscall emulation code is not fully cooked
yet as UML relies on some rather fragile SIGSEGV semantics.

Linus suggested in https://lkml.org/lkml/2011/8/9/376

 to default
to vsyscall=native for now, this patch implements that.

Signed-off-by: default avatarAdrian Bunk <bunk@kernel.org>
Acked-by: default avatarAndrew Lutomirski <luto@mit.edu>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/20111005214047.GE14406@localhost.pp.htv.fi


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 65112dcc

Documentation/kernel-parameters.txt

+4 −3
Original line number Diff line number Diff line
@@ -2706,10 +2706,11 @@ 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     [default] Vsyscalls turn into traps and are

			            emulated reasonably safely.

			emulate     Vsyscalls turn into traps and are emulated

			            reasonably safely.



			native      Vsyscalls are native syscall instructions.

			native      [default] 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.

arch/x86/kernel/vsyscall_64.c

+1 −1
Original line number Diff line number Diff line
@@ -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 = EMULATE;

static enum { EMULATE, NATIVE, NONE } vsyscall_mode = NATIVE;



static int __init vsyscall_setup(char *str)

{