powerpc/syscall: Save r3 in regs->orig_r3

Save r3 in regs->orig_r3 in system_call_exception()
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/9a90805ab6b9101b46daf56470f457a57acd86fc.1612796617.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/entry_64.S

@@ -108,7 +108,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_TM)
 	li	r11,\trapnr
 	std	r11,_TRAP(r1)
 	std	r12,_CCR(r1)
-	std	r3,ORIG_GPR3(r1)
 	addi	r10,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
 	std	r11,-16(r10)		/* "regshere" marker */
@@ -284,7 +283,6 @@ END_BTB_FLUSH_SECTION
 	std	r10,_LINK(r1)
 	std	r11,_TRAP(r1)
 	std	r12,_CCR(r1)
-	std	r3,ORIG_GPR3(r1)
 	addi	r10,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
 	std	r11,-16(r10)		/* "regshere" marker */

arch/powerpc/kernel/interrupt.c

@@ -29,6 +29,8 @@ notrace long system_call_exception(long r3, long r4, long r5,
 {
 	syscall_fn f;
 
+	regs->orig_gpr3 = r3;
+
 	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
 		BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);