[POWERPC] Fix manual assembly WARN_ON() in enter_rtas().

When we switched over to the generic BUG mechanism we forgot to change
the assembly code which open-codes a WARN_ON() in enter_rtas(), so the
bug table got corrupted.

This patch provides an EMIT_BUG_ENTRY macro for use in assembly code,
and uses it in entry_64.S. Tested with CONFIG_DEBUG_BUGVERBOSE on ppc64
but not without -- I tried to turn it off but it wouldn't go away; I
suspect Aunt Tillie probably needed it.

This version gets __FILE__ and __LINE__ right in the assembly version --
rather than saying include/asm-powerpc/bug.h line 21 every time which is
a little suboptimal.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/asm-offsets.c

@@ -303,5 +303,8 @@ int main(void)
 	DEFINE(NSEC_PER_SEC, NSEC_PER_SEC);
 	DEFINE(CLOCK_REALTIME_RES, TICK_NSEC);
 
+#ifdef CONFIG_BUG
+	DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));
+#endif
 	return 0;
 }

arch/powerpc/kernel/entry_64.S

@@ -28,6 +28,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/cputable.h>
 #include <asm/firmware.h>
+#include <asm/bug.h>
 
 /*
  * System calls.
@@ -634,19 +635,15 @@ _GLOBAL(enter_rtas)
 	li	r0,0
 	mtcr	r0
 
+#ifdef CONFIG_BUG	
 	/* There is no way it is acceptable to get here with interrupts enabled,
 	 * check it with the asm equivalent of WARN_ON
 	 */
 	lbz	r0,PACASOFTIRQEN(r13)
 1:	tdnei	r0,0
-.section __bug_table,"a"
-	.llong	1b,__LINE__ + 0x1000000, 1f, 2f
-.previous
-.section .rodata,"a"
-1:	.asciz	__FILE__
-2:	.asciz "enter_rtas"
-.previous
-
+	EMIT_BUG_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
+#endif
+	
 	/* Hard-disable interrupts */
 	mfmsr	r6
 	rldicl	r7,r6,48,1