powerpc/32: move LOAD_MSR_KERNEL() into head_32.h and use it

As preparation for using head_32.h for head_40x.S, move
LOAD_MSR_KERNEL() there and use it to load r10 with MSR_KERNEL value.

In the mean time, this patch modifies it so that it takes into account
the size of the passed value to determine if 'li' can be used or if
'lis/ori' is needed instead of using the size of MSR_KERNEL. This is
done by using gas macro.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/entry_32.S

@@ -38,14 +38,7 @@
 #include <asm/barrier.h>
 #include <asm/kup.h>
 
-/*
- * MSR_KERNEL is > 0x10000 on 4xx/Book-E since it include MSR_CE.
- */
-#if MSR_KERNEL >= 0x10000
-#define LOAD_MSR_KERNEL(r, x)	lis r,(x)@h; ori r,r,(x)@l
-#else
-#define LOAD_MSR_KERNEL(r, x)	li r,(x)
-#endif
+#include "head_32.h"
 
 /*
  * Align to 4k in order to ensure that all functions modyfing srr0/srr1

arch/powerpc/kernel/head_32.h

@@ -4,6 +4,19 @@
 
 #include <asm/ptrace.h>	/* for STACK_FRAME_REGS_MARKER */
 
+/*
+ * MSR_KERNEL is > 0x8000 on 4xx/Book-E since it include MSR_CE.
+ */
+.macro __LOAD_MSR_KERNEL r, x
+.if \x >= 0x8000
+	lis \r, (\x)@h
+	ori \r, \r, (\x)@l
+.else
+	li \r, (\x)
+.endif
+.endm
+#define LOAD_MSR_KERNEL(r, x) __LOAD_MSR_KERNEL r, x
+
 /*
  * Exception entry code.  This code runs with address translation
  * turned off, i.e. using physical addresses.
@@ -89,7 +102,7 @@
 #define EXC_XFER_TEMPLATE(n, hdlr, trap, copyee, tfer, ret)	\
 	li	r10,trap;					\
 	stw	r10,_TRAP(r11);					\
-	li	r10,MSR_KERNEL;					\
+	LOAD_MSR_KERNEL(r10, MSR_KERNEL);			\
 	copyee(r10, r9);					\
 	bl	tfer;						\
 i##n:								\