x86/vsyscall: Change the default vsyscall mode to xonly
The use case for full emulation over xonly is very esoteric, e.g. magic
instrumentation tools.
Change the default to the safer xonly mode.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Kernel Hardening <kernel-hardening@lists.openwall.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/30539f8072d2376b9c9efcc07e6ed0d6bf20e882.1561610354.git.luto@kernel.org
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0182d2c..32028ed 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2285,7 +2285,7 @@
choice
prompt "vsyscall table for legacy applications"
depends on X86_64
- default LEGACY_VSYSCALL_EMULATE
+ default LEGACY_VSYSCALL_XONLY
help
Legacy user code that does not know how to find the vDSO expects
to be able to issue three syscalls by calling fixed addresses in