s390/boot: Convert diag500_storage_limit() to extable

Shorten diag500_storage_limit() and use regular EX_TABLE program check
handling.

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

Author: hcahca

arch/s390/boot/physmem_info.c

@@ -104,29 +104,15 @@ static int diag260(void)
 static int diag500_storage_limit(unsigned long *max_physmem_end)
 {
 	unsigned long storage_limit;
-	unsigned long reg1, reg2;
-	psw_t old;
 
 	asm volatile(
-		"	mvc	0(16,%[psw_old]),0(%[psw_pgm])\n"
-		"	epsw	%[reg1],%[reg2]\n"
-		"	st	%[reg1],0(%[psw_pgm])\n"
-		"	st	%[reg2],4(%[psw_pgm])\n"
-		"	larl	%[reg1],1f\n"
-		"	stg	%[reg1],8(%[psw_pgm])\n"
-		"	lghi	1,%[subcode]\n"
-		"	lghi	2,0\n"
-		"	diag	2,4,0x500\n"
-		"1:	mvc	0(16,%[psw_pgm]),0(%[psw_old])\n"
-		"	lgr	%[slimit],2\n"
-		: [reg1] "=&d" (reg1),
-		  [reg2] "=&a" (reg2),
-		  [slimit] "=d" (storage_limit),
-		  "=Q" (get_lowcore()->program_new_psw),
-		  "=Q" (old)
-		: [psw_old] "a" (&old),
-		  [psw_pgm] "a" (&get_lowcore()->program_new_psw),
-		  [subcode] "i" (DIAG500_SC_STOR_LIMIT)
+		"	lghi	%%r1,%[subcode]\n"
+		"	lghi	%%r2,0\n"
+		"	diag	%%r2,%%r4,0x500\n"
+		"0:	lgr	%[slimit],%%r2\n"
+		EX_TABLE(0b, 0b)
+		: [slimit] "=d" (storage_limit)
+		: [subcode] "i" (DIAG500_SC_STOR_LIMIT)
 		: "memory", "1", "2");
 	if (!storage_limit)
 		return -EINVAL;