s390/pfault: cleanup inline assemblies

Cleanup the pfault inline assemblies:
- Use symbolic names for operands
- Add extra linebreaks, and whitespace to improve readability

In addition, change __pfault_init() to return -EOPNOTSUPP in case of
an exception, and don't return a made up valid diag 258 return value
(aka "8").
This allows to simplify the inline assembly, and makes debugging
easier, in case something is broken.

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: hcahca

arch/s390/include/asm/pfault.h

@@ -5,14 +5,16 @@
 #ifndef _ASM_S390_PFAULT_H
 #define _ASM_S390_PFAULT_H
 
+#include <linux/errno.h>
+
 int __pfault_init(void);
 void __pfault_fini(void);
 
 static inline int pfault_init(void)
 {
 	if (IS_ENABLED(CONFIG_PFAULT))
 		return __pfault_init();
-	return -1;
+	return -EOPNOTSUPP;
 }
 
 static inline void pfault_fini(void)

arch/s390/mm/pfault.c

@@ -51,20 +51,19 @@ static struct pfault_refbk pfault_init_refbk = {
 
 int __pfault_init(void)
 {
-        int rc;
+	int rc = -EOPNOTSUPP;
 
 	if (pfault_disable)
-		return -1;
+		return rc;
 	diag_stat_inc(DIAG_STAT_X258);
 	asm volatile(
-		"	diag	%1,%0,0x258\n"
-		"0:	j	2f\n"
-		"1:	la	%0,8\n"
-		"2:\n"
-		EX_TABLE(0b,1b)
-		: "=d" (rc)
-		: "a" (&pfault_init_refbk), "m" (pfault_init_refbk) : "cc");
-        return rc;
+		"	diag	%[refbk],%[rc],0x258\n"
+		"0:	nopr	%%r7\n"
+		EX_TABLE(0b, 0b)
+		: [rc] "+d" (rc)
+		: [refbk] "a" (&pfault_init_refbk), "m" (pfault_init_refbk)
+		: "cc");
+	return rc;
 }
 
 static struct pfault_refbk pfault_fini_refbk = {
@@ -76,15 +75,16 @@ static struct pfault_refbk pfault_fini_refbk = {
 
 void __pfault_fini(void)
 {
-
 	if (pfault_disable)
 		return;
 	diag_stat_inc(DIAG_STAT_X258);
 	asm volatile(
-		"	diag	%0,0,0x258\n"
+		"	diag	%[refbk],0,0x258\n"
 		"0:	nopr	%%r7\n"
-		EX_TABLE(0b,0b)
-		: : "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk) : "cc");
+		EX_TABLE(0b, 0b)
+		:
+		: [refbk] "a" (&pfault_fini_refbk), "m" (pfault_fini_refbk)
+		: "cc");
 }
 
 static DEFINE_SPINLOCK(pfault_lock);