powerpc/64: CONFIG_RELOCATABLE support for hmi interrupts

The branch from hmi_exception_early to hmi_exception_realmode must use
a "relocatable-style" branch, because it is branching from unrelocated
exception code to beyond __end_interrupts.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/exception-64s.h

@@ -236,6 +236,11 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
 	mtctr	reg;							\
 	bctr
 
+#define BRANCH_LINK_TO_FAR(reg, label)					\
+	__LOAD_FAR_HANDLER(reg, label);					\
+	mtctr	reg;							\
+	bctrl
+
 /*
  * KVM requires __LOAD_FAR_HANDLER.
  *
@@ -260,6 +265,9 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
 #define BRANCH_TO_COMMON(reg, label)					\
 	b	label
 
+#define BRANCH_LINK_TO_FAR(reg, label)					\
+	bl	label
+
 #define BRANCH_TO_KVM(reg, label)					\
 	b	label
 

arch/powerpc/kernel/exceptions-64s.S

@@ -982,7 +982,7 @@ TRAMP_REAL_BEGIN(hmi_exception_early)
 	EXCEPTION_PROLOG_COMMON_2(PACA_EXGEN)
 	EXCEPTION_PROLOG_COMMON_3(0xe60)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	bl	hmi_exception_realmode
+	BRANCH_LINK_TO_FAR(r4, hmi_exception_realmode)
 	/* Windup the stack. */
 	/* Move original HSRR0 and HSRR1 into the respective regs */
 	ld	r9,_MSR(r1)