parisc: Provide __ucmpdi2 to resolve undefined references in 32 bit builds.

commit ca0ad83d upstream.

The Debian experimental linux source package (3.8.5-1) build fails
with the following errors:
...
MODPOST 2016 modules
ERROR: "__ucmpdi2" [fs/btrfs/btrfs.ko] undefined!
ERROR: "__ucmpdi2" [drivers/md/dm-verity.ko] undefined!

The attached patch resolves this problem.  It is based on the s390
implementation of ucmpdi2.c.
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/parisc/kernel/parisc_ksyms.c

@@ -121,11 +121,13 @@ extern void __ashrdi3(void);
 extern void __ashldi3(void);
 extern void __lshrdi3(void);
 extern void __muldi3(void);
+extern void __ucmpdi2(void);
 
 EXPORT_SYMBOL(__ashrdi3);
 EXPORT_SYMBOL(__ashldi3);
 EXPORT_SYMBOL(__lshrdi3);
 EXPORT_SYMBOL(__muldi3);
+EXPORT_SYMBOL(__ucmpdi2);
 
 asmlinkage void * __canonicalize_funcptr_for_compare(void *);
 EXPORT_SYMBOL(__canonicalize_funcptr_for_compare);

arch/parisc/lib/Makefile

@@ -2,6 +2,7 @@
 # Makefile for parisc-specific library files
 #
 
-lib-y	:= lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o
+lib-y	:= lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o \
+	   ucmpdi2.o
 
 obj-y	:= iomap.o

arch/parisc/lib/ucmpdi2.c

+#include <linux/module.h>
+
+union ull_union {
+	unsigned long long ull;
+	struct {
+		unsigned int high;
+		unsigned int low;
+	} ui;
+};
+
+int __ucmpdi2(unsigned long long a, unsigned long long b)
+{
+	union ull_union au = {.ull = a};
+	union ull_union bu = {.ull = b};
+
+	if (au.ui.high < bu.ui.high)
+		return 0;
+	else if (au.ui.high > bu.ui.high)
+		return 2;
+	if (au.ui.low < bu.ui.low)
+		return 0;
+	else if (au.ui.low > bu.ui.low)
+		return 2;
+	return 1;
+}