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authorAdrian Bunk <bunk@stusta.de>2011-10-06 00:40:47 +0300
committerIngo Molnar <mingo@elte.hu>2011-10-11 08:23:34 +0200
commit2b666859ec323403ac9a3a441d16eab30945404b (patch)
treea2db4a7fc4cc386deda62584379713fa5a5d6bbb /Documentation
parent65112dccf8a113737684366349d7f9ec373ddc47 (diff)
downloadlinux-linaro-precise-2b666859ec323403ac9a3a441d16eab30945404b.tar.gz
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: Adrian Bunk <bunk@kernel.org> Acked-by: Andrew 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: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt7
1 files changed, 4 insertions, 3 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 854ed5ca7e3..d6e6724446c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -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.