s390: Correct register corruption in critical section cleanup

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>

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index f03402e..3891805 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -1265,7 +1265,7 @@ 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:
@@ -1301,7 +1301,7 @@ 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: