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s390/vtime: fix inline assembly clobber list 

commit b29c5093820d333eef22f58cd04ec0d089059c39 upstream.

The stck/stckf instruction used within the inline assembly within
do_account_vtime() changes the condition code. This is not reflected
with the clobber list, and therefore might result in incorrect code
generation.

It seems unlikely that the compiler could generate incorrect code
considering the surrounding C code, but it must still be fixed.

Cc: <stable@vger.kernel.org>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Heiko Carstens 2021-02-02 16:45:37 +01:00 committed by Greg Kroah-Hartman
parent 0733277166
commit 8e6c8cfa9a
1 changed files with 2 additions and 1 deletions
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3
arch/s390/kernel/vtime.c
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@ -136,7 +136,8 @@ static int do_account_vtime(struct task_struct *tsk)
" stck %1" /* Store current tod clock value */
#endif
: "=Q" (S390_lowcore.last_update_timer),
"=Q" (S390_lowcore.last_update_clock));
"=Q" (S390_lowcore.last_update_clock)
: : "cc");
clock = S390_lowcore.last_update_clock - clock;
timer -= S390_lowcore.last_update_timer;