From: Jiri Slaby <jslaby@suse.cz>
Date: Fri, 18 May 2018 08:47:11 +0200
Subject: x86/stacktrace: Do not fail for ORC with regs on stack
Git-commit: 0c414367c04eeb00c3ebfee0b74c9e7f3b95fd62
Patch-mainline: v4.19-rc1
References: bnc#1058115

save_stack_trace_reliable now returns "non reliable" when there are
kernel pt_regs on stack. This means an interrupt or exception happened
somewhere down the route. It is a problem for the frame pointer
unwinder, because the frame might not have been set up yet when the irq
happened, so the unwinder might fail to unwind from the interrupted
function.

With ORC, this is not a problem, as ORC has out-of-band data. We can
find ORC data even for the IP in the interrupted function and always
unwind one level up reliably.

So lift the check to apply only when CONFIG_FRAME_POINTER=y is enabled.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/lkml/20180518064713.26440-4-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/stacktrace.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -106,7 +106,8 @@ __save_stack_trace_reliable(struct stack
 			 * unreliable.
 			 */
 
-			return -EINVAL;
+			if (IS_ENABLED(CONFIG_FRAME_POINTER))
+				return -EINVAL;
 		}
 
 		addr = unwind_get_return_address(&state);