powerpc/kuap: Wire-up KUAP on 85xx in 32 bits mode.

This adds KUAP support to 85xx in 32 bits mode.
This is done by reading the content of SPRN_MAS1 and checking
the TID at the time user pgtable is loaded.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f8696f8980ca1532ada3a2f0e0a03e756269c7fe.1634627931.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/head_fsl_booke.S

@@ -462,6 +462,12 @@ END_BTB_FLUSH_SECTION
 	mfspr	r11,SPRN_SPRG_THREAD
 	lwz	r11,PGDIR(r11)
 
+#ifdef CONFIG_PPC_KUAP
+	mfspr	r12, SPRN_MAS1
+	rlwinm.	r12,r12,0,0x3fff0000
+	beq	2f			/* KUAP fault */
+#endif
+
 4:
 	/* Mask of required permission bits. Note that while we
 	 * do copy ESR:ST to _PAGE_RW position as trying to write
@@ -571,6 +577,12 @@ END_BTB_FLUSH_SECTION
 	mfspr	r11,SPRN_SPRG_THREAD
 	lwz	r11,PGDIR(r11)
 
+#ifdef CONFIG_PPC_KUAP
+	mfspr	r12, SPRN_MAS1
+	rlwinm.	r12,r12,0,0x3fff0000
+	beq	2f			/* KUAP fault */
+#endif
+
 	/* Make up the required permissions for user code */
 #ifdef CONFIG_PTE_64BIT
 	li	r13,_PAGE_PRESENT | _PAGE_BAP_UX

arch/powerpc/platforms/Kconfig.cputype

@@ -37,6 +37,7 @@ config PPC_BOOK3S_32
 config PPC_85xx
 	bool "Freescale 85xx"
 	select E500
+	select PPC_HAVE_KUAP
 
 config PPC_8xx
 	bool "Freescale 8xx"