parisc: Provide an extru_safe() macro to extract unsigned bits

The extru instruction leaves the most significant 32 bits of the
target register in an undefined state on PA 2.0 systems.
Provide a macro to safely use extru on 32- and 64-bit machines.

Suggested-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/include/asm/assembly.h

@@ -147,6 +147,17 @@
 	extrd,u \r, 63-(\sa), 64-(\sa), \t
 	.endm
 
+	/* Extract unsigned for 32- and 64-bit
+	 * The extru instruction leaves the most significant 32 bits of the
+	 * target register in an undefined state on PA 2.0 systems. */
+	.macro extru_safe r, p, len, t
+#ifdef CONFIG_64BIT
+	extrd,u	\r, 32+(\p), \len, \t
+#else
+	extru	\r, \p, \len, \t
+#endif
+	.endm
+
 	/* load 32-bit 'value' into 'reg' compensating for the ldil
 	 * sign-extension when running in wide mode.
 	 * WARNING!! neither 'value' nor 'reg' can be expressions