s390/mm,fault: use get_kernel_nofault() to dereference in dump_pagetable()

The page table dumper uses get_kernel_nofault() to test if dereferencing
page table entries is possible. Use the result, which is the required page
table entry, instead of throwing it away and dereferencing a second time
without any safe guard.

Reviewed-by: Claudio Imbrenda <imbrenda@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/mm/fault.c

@@ -112,59 +112,52 @@ static __always_inline bool fault_is_write(struct pt_regs *regs)
 	return false;
 }
 
-static int bad_address(void *p)
-{
-	unsigned long dummy;
-
-	return get_kernel_nofault(dummy, (unsigned long *)p);
-}
-
 static void dump_pagetable(unsigned long asce, unsigned long address)
 {
-	unsigned long *table = __va(asce & _ASCE_ORIGIN);
+	unsigned long entry, *table = __va(asce & _ASCE_ORIGIN);
 
 	pr_alert("AS:%016lx ", asce);
 	switch (asce & _ASCE_TYPE_MASK) {
 	case _ASCE_TYPE_REGION1:
 		table += (address & _REGION1_INDEX) >> _REGION1_SHIFT;
-		if (bad_address(table))
+		if (get_kernel_nofault(entry, table))
 			goto bad;
-		pr_cont("R1:%016lx ", *table);
-		if (*table & _REGION_ENTRY_INVALID)
+		pr_cont("R1:%016lx ", entry);
+		if (entry & _REGION_ENTRY_INVALID)
 			goto out;
-		table = __va(*table & _REGION_ENTRY_ORIGIN);
+		table = __va(entry & _REGION_ENTRY_ORIGIN);
 		fallthrough;
 	case _ASCE_TYPE_REGION2:
 		table += (address & _REGION2_INDEX) >> _REGION2_SHIFT;
-		if (bad_address(table))
+		if (get_kernel_nofault(entry, table))
 			goto bad;
-		pr_cont("R2:%016lx ", *table);
-		if (*table & _REGION_ENTRY_INVALID)
+		pr_cont("R2:%016lx ", entry);
+		if (entry & _REGION_ENTRY_INVALID)
 			goto out;
-		table = __va(*table & _REGION_ENTRY_ORIGIN);
+		table = __va(entry & _REGION_ENTRY_ORIGIN);
 		fallthrough;
 	case _ASCE_TYPE_REGION3:
 		table += (address & _REGION3_INDEX) >> _REGION3_SHIFT;
-		if (bad_address(table))
+		if (get_kernel_nofault(entry, table))
 			goto bad;
-		pr_cont("R3:%016lx ", *table);
-		if (*table & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
+		pr_cont("R3:%016lx ", entry);
+		if (entry & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
 			goto out;
-		table = __va(*table & _REGION_ENTRY_ORIGIN);
+		table = __va(entry & _REGION_ENTRY_ORIGIN);
 		fallthrough;
 	case _ASCE_TYPE_SEGMENT:
 		table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
-		if (bad_address(table))
+		if (get_kernel_nofault(entry, table))
 			goto bad;
-		pr_cont("S:%016lx ", *table);
-		if (*table & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
+		pr_cont("S:%016lx ", entry);
+		if (entry & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
 			goto out;
-		table = __va(*table & _SEGMENT_ENTRY_ORIGIN);
+		table = __va(entry & _SEGMENT_ENTRY_ORIGIN);
 	}
 	table += (address & _PAGE_INDEX) >> _PAGE_SHIFT;
-	if (bad_address(table))
+	if (get_kernel_nofault(entry, table))
 		goto bad;
-	pr_cont("P:%016lx ", *table);
+	pr_cont("P:%016lx ", entry);
 out:
 	pr_cont("\n");
 	return;