s390/alternatives: Convert runtime sanity check into compile time check

__apply_alternatives() contains a runtime check which verifies that the
size of the to be patched code area is even. Convert this to a compile time
check using a similar ".org" trick, which is already used to verify that
old and new code areas have the same size.
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/include/asm/alternative-asm.h

@@ -15,6 +15,7 @@
 	.long	\alt_start - .
 	.word	\feature
 	.byte	\orig_end - \orig_start
+	.org	. - ( \orig_end - \orig_start ) & 1
 	.org	. - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )
 	.org	. - ( \alt_end - \alt_start ) + ( \orig_end - \orig_start )
 .endm

arch/s390/include/asm/alternative.h

@@ -53,6 +53,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
 	"\t.word " __stringify(facility) "\n"	/* facility bit    */	\
 	"\t.byte " oldinstr_len "\n"		/* instruction len */	\
+	"\t.org . - (" oldinstr_len ") & 1\n"				\
 	"\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n"	\
 	"\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
 

arch/s390/kernel/alternative.c

@@ -33,13 +33,6 @@ static void __init_or_module __apply_alternatives(struct alt_instr *start,
 
 		if (!__test_facility(a->facility, alt_stfle_fac_list))
 			continue;
-
-		if (unlikely(a->instrlen % 2)) {
-			WARN_ONCE(1, "cpu alternatives instructions length is "
-				     "odd, skipping patching\n");
-			continue;
-		}
-
 		s390_kernel_write(instr, replacement, a->instrlen);
 	}
 }