S390: __div64_31 broken for CONFIG_MARCH_G5

commit 4fa81ed27781a12f6303b9263056635ae74e3e21 upstream.

The implementation of __div64_31 for G5 machines is broken. The comments
in __div64_31 are correct, only the code does not do what the comments
say. The part "If the remainder has overflown subtract base and increase
the quotient" is only partially realized, the base is subtracted correctly
but the quotient is only increased if the dividend had the last bit set.
Using the correct instruction fixes the problem.

Reported-by: Frans Pop <elendil@planet.nl>
Tested-by: Frans Pop <elendil@planet.nl>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/s390/lib/div64.c b/arch/s390/lib/div64.c
index a5f8300..d9e62c0 100644 (file)
--- a/arch/s390/lib/div64.c
+++ b/arch/s390/lib/div64.c
@@ -61,7 +61,7 @@ static uint32_t __div64_31(uint64_t *n, uint32_t base)
                "       clr     %0,%3\n"
                "       jl      0f\n"
                "       slr     %0,%3\n"
-               "       alr     %1,%2\n"
+               "       ahi     %1,1\n"
                "0:\n"
                : "+d" (reg2), "+d" (reg3), "=d" (tmp)
                : "d" (base), "2" (1UL) : "cc" );