x86/asm/traps: Disable tracing and kprobes in fixup_bad_iret and sync_regs

x86/asm/traps: Disable tracing and kprobes in fixup_bad_iret and sync_regs

commit 7ddc6a2199f1da405a2fb68c40db8899b1a8cd87 upstream.

These functions can be executed on the int3 stack, so kprobes
are dangerous. Tracing is probably a bad idea, too.

Fixes: b645af2d5905 ("x86_64, traps: Rework bad_iret")
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/50e33d26adca60816f3ba968875801652507d0c4.1416870125.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.2:
 - Use __kprobes instead of NOKPROBE_SYMBOL()
 - Don't use __visible]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Zefan Li <lizefan@huawei.com>