[PATCH 4.14 06/53] s390: Correct register corruption in critical section cleanup

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christian Borntraeger <borntraeger@de.ibm.com>

commit 891f6a726cacbb87e5b06076693ffab53bd378d7 upstream.

In the critical section cleanup we must not mess with r1.  For march=z9
or older, larl + ex (instead of exrl) are used with r1 as a temporary
register. This can clobber r1 in several interrupt handlers. Fix this by
using r11 as a temp register.  r11 is being saved by all callers of
cleanup_critical.

Fixes: 6dd85fbb87 ("s390: move expoline assembler macros to a header")
Cc: stable@vger.kernel.org #v4.16
Reported-by: Oliver Kurz <okurz@suse.com>
Reported-by: Petr Tesařík <ptesarik@suse.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/s390/kernel/entry.S |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -1244,7 +1244,7 @@ cleanup_critical:
 	jl	0f
 	clg	%r9,BASED(.Lcleanup_table+104)	# .Lload_fpu_regs_end
 	jl	.Lcleanup_load_fpu_regs
-0:	BR_EX	%r14
+0:	BR_EX	%r14,%r11
 
 	.align	8
 .Lcleanup_table:
@@ -1280,7 +1280,7 @@ cleanup_critical:
 	ni	__SIE_PROG0C+3(%r9),0xfe	# no longer in SIE
 	lctlg	%c1,%c1,__LC_USER_ASCE		# load primary asce
 	larl	%r9,sie_exit			# skip forward to sie_exit
-	BR_EX	%r14
+	BR_EX	%r14,%r11
 #endif
 
 .Lcleanup_system_call: