powerpc/32: Handle bookE debugging in C in exception entry

The handling of SPRN_DBCR0 and other registers can easily
be done in C instead of ASM.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6d6b2497115890b90cfa72a2b3ab1da5f78123c2.1615552866.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/interrupt.h

@@ -65,6 +65,8 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup
 	if (user_mode(regs))
 		account_cpu_user_entry();
 #endif
+
+	booke_restore_dbcr0();
 }
 
 /*

arch/powerpc/kernel/entry_32.S

@@ -146,32 +146,9 @@ transfer_to_handler:
 	addi	r2, r12, -THREAD
 	addi	r11,r1,STACK_FRAME_OVERHEAD
 	stw	r11,PT_REGS(r12)
-#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
-	/* Check to see if the dbcr0 register is set up to debug.  Use the
-	   internal debug mode bit to do this. */
-	lwz	r12,THREAD_DBCR0(r12)
-	andis.	r12,r12,DBCR0_IDM@h
-#endif
 #ifdef CONFIG_PPC_BOOK3S_32
 	kuep_lock r11, r12
 #endif
-#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
-	beq+	3f
-	/* From user and task is ptraced - load up global dbcr0 */
-	li	r12,-1			/* clear all pending debug events */
-	mtspr	SPRN_DBSR,r12
-	lis	r11,global_dbcr0@ha
-	tophys_novmstack r11,r11
-	addi	r11,r11,global_dbcr0@l
-#ifdef CONFIG_SMP
-	lwz	r9,TASK_CPU(r2)
-	slwi	r9,r9,2
-	add	r11,r11,r9
-#endif
-	lwz	r12,0(r11)
-	mtspr	SPRN_DBCR0,r12
-#endif
-
 	b	3f
 
 2:	/* if from kernel, check interrupted DOZE/NAP mode and