tree e19b729126d28efa4f4325b21f834100d981e5bf
parent 75b99dbd634f9caf7b4e48ec5c2dcec8c1837372
author Heiko Carstens <heiko.carstens@de.ibm.com> 1389947835 +0100
committer David S. Miller <davem@davemloft.net> 1390013689 -0800

s390/bpf,jit: fix 32 bit divisions, use unsigned divide instructions

The s390 bpf jit compiler emits the signed divide instructions "dr" and "d"
for unsigned divisions.
This can cause problems: the dividend will be zero extended to a 64 bit value
and the divisor is the 32 bit signed value as specified A or X accumulator,
even though A and X are supposed to be treated as unsigned values.

The divide instrunctions will generate an exception if the result cannot be
expressed with a 32 bit signed value.
This is the case if e.g. the dividend is 0xffffffff and the divisor either 1
or also 0xffffffff (signed: -1).

To avoid all these issues simply use unsigned divide instructions.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>