powerpc/32s: Remove capability to disable KUEP at boottime

[ Upstream commit df415cd758 ]

Disabling KUEP at boottime makes things unnecessarily complex.

Still allow disabling KUEP at build time, but when it's built-in
it is always there.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/96f583f82423a29a4205c60b9721079111b35567.1634627931.git.christophe.leroy@csgroup.eu
Stable-dep-of: f0eee815ba ("powerpc/47x: Fix 47x syscall return crash")
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/powerpc/include/asm/book3s/32/kup.h

@@ -12,7 +12,6 @@
 #include <linux/jump_label.h>
 
 extern struct static_key_false disable_kuap_key;
-extern struct static_key_false disable_kuep_key;
 
 static __always_inline bool kuap_is_disabled(void)
 {
@@ -21,7 +20,7 @@ static __always_inline bool kuap_is_disabled(void)
 
 static __always_inline bool kuep_is_disabled(void)
 {
-	return !IS_ENABLED(CONFIG_PPC_KUEP) || static_branch_unlikely(&disable_kuep_key);
+	return !IS_ENABLED(CONFIG_PPC_KUEP);
 }
 
 static inline void kuep_lock(void)

arch/powerpc/mm/book3s32/kuep.c

@@ -3,18 +3,12 @@
 #include <asm/kup.h>
 #include <asm/smp.h>
 
-struct static_key_false disable_kuep_key;
-
 void setup_kuep(bool disabled)
 {
-	if (!disabled)
-		kuep_lock();
+	kuep_lock();
 
 	if (smp_processor_id() != boot_cpuid)
 		return;
 
-	if (disabled)
-		static_branch_enable(&disable_kuep_key);
-	else
-		pr_info("Activating Kernel Userspace Execution Prevention\n");
+	pr_info("Activating Kernel Userspace Execution Prevention\n");
 }