powerpc/kuap: Wire-up KUAP on 44x

This adds KUAP support to 44x. This is done by checking
the content of SPRN_PID at the time it is read and written
into SPRN_MMUCR.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7d6c3f1978a26feada74b084f651e8cf1e3b3a47.1634627931.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/head_44x.S

@@ -334,6 +334,10 @@ interrupt_base:
 	mfspr	r12,SPRN_MMUCR
 	mfspr   r13,SPRN_PID		/* Get PID */
 	rlwimi	r12,r13,0,24,31		/* Set TID */
+#ifdef CONFIG_PPC_KUAP
+	cmpwi	r13,0
+	beq	2f			/* KUAP Fault */
+#endif
 
 4:
 	mtspr	SPRN_MMUCR,r12
@@ -444,6 +448,10 @@ interrupt_base:
 	mfspr	r12,SPRN_MMUCR
 	mfspr   r13,SPRN_PID		/* Get PID */
 	rlwimi	r12,r13,0,24,31		/* Set TID */
+#ifdef CONFIG_PPC_KUAP
+	cmpwi	r13,0
+	beq	2f			/* KUAP Fault */
+#endif
 
 4:
 	mtspr	SPRN_MMUCR,r12
@@ -572,6 +580,10 @@ finish_tlb_load_44x:
 3:	mfspr	r11,SPRN_SPRG3
 	lwz	r11,PGDIR(r11)
 	mfspr   r12,SPRN_PID		/* Get PID */
+#ifdef CONFIG_PPC_KUAP
+	cmpwi	r12,0
+	beq	2f			/* KUAP Fault */
+#endif
 4:	mtspr	SPRN_MMUCR,r12		/* Set MMUCR */
 
 	/* Mask of required permission bits. Note that while we
@@ -669,6 +681,10 @@ finish_tlb_load_44x:
 3:	mfspr	r11,SPRN_SPRG_THREAD
 	lwz	r11,PGDIR(r11)
 	mfspr   r12,SPRN_PID		/* Get PID */
+#ifdef CONFIG_PPC_KUAP
+	cmpwi	r12,0
+	beq	2f			/* KUAP Fault */
+#endif
 4:	mtspr	SPRN_MMUCR,r12		/* Set MMUCR */
 
 	/* Make up the required permissions */

arch/powerpc/platforms/Kconfig.cputype

@@ -64,6 +64,7 @@ config 44x
 	select PHYS_64BIT
 	select PPC_HAVE_KUEP
 	select PPC_KUEP
+	select PPC_HAVE_KUAP
 
 endchoice