powerpc/44x: Activate KUEP at all time

On 44x, KUEP is implemented by clearing SX bit during TLB miss
for user pages. The impact is minimal and not worth neither
boot time nor build time selection.

Activate it at all time.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2414d662558e7fb27d1ed41c8e47c591d576acac.1634627931.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/nohash/32/mmu-44x.h

@@ -113,7 +113,6 @@ typedef struct {
 
 /* patch sites */
 extern s32 patch__tlb_44x_hwater_D, patch__tlb_44x_hwater_I;
-extern s32 patch__tlb_44x_kuep, patch__tlb_47x_kuep;
 
 #endif /* !__ASSEMBLY__ */
 

arch/powerpc/kernel/head_44x.S

@@ -532,10 +532,7 @@ finish_tlb_load_44x:
 	andi.	r10,r12,_PAGE_USER		/* User page ? */
 	beq	1f				/* nope, leave U bits empty */
 	rlwimi	r11,r11,3,26,28			/* yes, copy S bits to U */
-#ifdef CONFIG_PPC_KUEP
-0:	rlwinm	r11,r11,0,~PPC44x_TLB_SX	/* Clear SX if User page */
-	patch_site 0b, patch__tlb_44x_kuep
-#endif
+	rlwinm	r11,r11,0,~PPC44x_TLB_SX	/* Clear SX if User page */
 1:	tlbwe	r11,r13,PPC44x_TLB_ATTRIB	/* Write ATTRIB */
 
 	/* Done...restore registers and get out of here.
@@ -747,10 +744,7 @@ finish_tlb_load_47x:
 	andi.	r10,r12,_PAGE_USER		/* User page ? */
 	beq	1f				/* nope, leave U bits empty */
 	rlwimi	r11,r11,3,26,28			/* yes, copy S bits to U */
-#ifdef CONFIG_PPC_KUEP
-0:	rlwinm	r11,r11,0,~PPC47x_TLB2_SX	/* Clear SX if User page */
-	patch_site 0b, patch__tlb_47x_kuep
-#endif
+	rlwinm	r11,r11,0,~PPC47x_TLB2_SX	/* Clear SX if User page */
 1:	tlbwe	r11,r13,2
 
 	/* Done...restore registers and get out of here.

arch/powerpc/mm/nohash/44x.c

@@ -247,12 +247,6 @@ void setup_kuep(bool disabled)
 	if (smp_processor_id() != boot_cpuid)
 		return;
 
-	if (disabled)
-		patch_instruction_site(&patch__tlb_44x_kuep, ppc_inst(PPC_RAW_NOP()));
-	else
-		pr_info("Activating Kernel Userspace Execution Prevention\n");
-
-	if (IS_ENABLED(CONFIG_PPC_47x) && disabled)
-		patch_instruction_site(&patch__tlb_47x_kuep, ppc_inst(PPC_RAW_NOP()));
+	pr_info("Activating Kernel Userspace Execution Prevention\n");
 }
 #endif

arch/powerpc/platforms/Kconfig.cputype

@@ -63,6 +63,7 @@ config 44x
 	select HAVE_PCI
 	select PHYS_64BIT
 	select PPC_HAVE_KUEP
+	select PPC_KUEP
 
 endchoice