s390/entry: add assembler macro to conveniently tests under mask

Various functions in entry.S perform test-under-mask instructions
to test for particular bits in memory.  Because test-under-mask uses
a mask value of one byte, the mask value and the offset into the
memory must be calculated manually.  This easily introduces errors
and is hard to review and read.

Introduce the TSTMSK assembler macro to specify a mask constant and
let the macro calculate the offset and the byte mask to generate a
test-under-mask instruction.  The benefit is that existing symbolic
constants can now be used for tests.  Also the macro checks for
zero mask values and mask values that consist of multiple bytes.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Hendrik Brueckner 2015-10-01 17:02:48 +02:00 • committed by Martin Schwidefsky
commit 83abeffbd5
3 changed files with 98 additions and 64 deletions