powerpc/32: Perform normal function call in exception entry

Now that the MMU is re-enabled before calling the transfer function,
we don't need anymore that hack with the address of the handler and
the return function sitting just after the 'bl' to the transfer
fonction, that function is retrieving via a read relative to 'lr'.

Do a regular call to the transfer function, then to the handler,
then branch to the return function.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/73c00f3361ca280ef8fd7814c291bd1f5b6e2081.1615552867.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/entry_32.S

@@ -104,7 +104,7 @@ transfer_to_handler:
 #ifdef CONFIG_PPC_BOOK3S_32
 	kuep_lock r11, r12
 #endif
-	b	3f
+	blr
 
 	/* if from kernel, check interrupted DOZE/NAP mode */
 2:
@@ -118,13 +118,7 @@ transfer_to_handler:
 #endif /* CONFIG_PPC_BOOK3S_32 || CONFIG_E500 */
 	.globl transfer_to_handler_cont
 transfer_to_handler_cont:
-3:
-	mflr	r9
-	lwz	r11,0(r9)		/* virtual address of handler */
-	lwz	r9,4(r9)		/* where to go when done */
-	mtctr	r11
-	mtlr	r9
-	bctr				/* jump to handler */
+	blr
 
 #if defined (CONFIG_PPC_BOOK3S_32) || defined(CONFIG_E500)
 4:	rlwinm	r12,r12,0,~_TLF_NAPPING
@@ -404,8 +398,8 @@ fee_restarts:
 	stw	r10,_TRAP(r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	transfer_to_handler_full
-	.long	unrecoverable_exception
-	.long	ret_from_except
+	bl	unrecoverable_exception
+	b	ret_from_except
 #endif
 
 	.globl	ret_from_except_full

arch/powerpc/kernel/head_32.h

@@ -190,8 +190,8 @@ _ASM_NOKPROBE_SYMBOL(\name\()_virt)
 	li	r10,trap;					\
 	stw	r10,_TRAP(r11);					\
 	bl	tfer;						\
-	.long	hdlr;						\
-	.long	ret
+	bl	hdlr;						\
+	b	ret
 
 #define EXC_XFER_STD(n, hdlr)		\
 	EXC_XFER_TEMPLATE(hdlr, n, MSR_KERNEL, transfer_to_handler_full,	\

arch/powerpc/kernel/head_booke.h

@@ -322,9 +322,9 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV)
 #define EXC_XFER_TEMPLATE(hdlr, trap, msr, tfer, ret)	\
 	li	r10,trap;					\
 	stw	r10,_TRAP(r11);					\
-	bl	tfer;		 				\
-	.long	hdlr;						\
-	.long	ret
+	bl	tfer;						\
+	bl	hdlr;						\
+	b	ret;						\
 
 #define EXC_XFER_STD(n, hdlr)		\
 	EXC_XFER_TEMPLATE(hdlr, n, MSR_KERNEL, transfer_to_handler_full, \