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>
diff --git a/arch/s390/include/asm/nmi.h b/arch/s390/include/asm/nmi.h
index 3027a5a..4c1cd41 100644
--- a/arch/s390/include/asm/nmi.h
+++ b/arch/s390/include/asm/nmi.h
@@ -11,8 +11,16 @@
 #ifndef _ASM_S390_NMI_H
 #define _ASM_S390_NMI_H
 
+#include <linux/const.h>
 #include <linux/types.h>
 
+#define MCCK_CODE_SYSTEM_DAMAGE		_BITUL(63)
+#define MCCK_CODE_CPU_TIMER_VALID	_BITUL(63 - 46)
+#define MCCK_CODE_PSW_MWP_VALID		_BITUL(63 - 20)
+#define MCCK_CODE_PSW_IA_VALID		_BITUL(63 - 23)
+
+#ifndef __ASSEMBLY__
+
 struct mci {
 	__u32 sd :  1; /* 00 system damage */
 	__u32 pd :  1; /* 01 instruction-processing damage */
@@ -63,4 +71,5 @@
 extern void s390_handle_mcck(void);
 extern void s390_do_machine_check(struct pt_regs *regs);
 
+#endif /* __ASSEMBLY__ */
 #endif /* _ASM_S390_NMI_H */