powerpc/kuap: Prepare for supporting KUAP on BOOK3E/64

Also call kuap_lock() and kuap_save_and_lock() from
interrupt functions with CONFIG_PPC64.

For book3s/64 we keep them empty as it is done in assembly.

Also do the locked assert when switching task unless it is
book3s/64.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1cbf94e26e6d6e2e028fd687588a7e6622d454a6.1634627931.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/book3s/64/kup.h

@@ -298,6 +298,15 @@ static inline unsigned long __kuap_get_and_assert_locked(void)
 	return amr;
 }
 
+/* Do nothing, book3s/64 does that in ASM */
+static inline void __kuap_lock(void)
+{
+}
+
+static inline void __kuap_save_and_lock(struct pt_regs *regs)
+{
+}
+
 /*
  * We support individually allowing read or write, but we don't support nesting
  * because that would require an expensive read/modify write of the AMR.

arch/powerpc/include/asm/interrupt.h

@@ -154,12 +154,14 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup
 	local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
 
 	if (user_mode(regs)) {
+		kuap_lock();
 		CT_WARN_ON(ct_state() != CONTEXT_USER);
 		user_exit_irqoff();
 
 		account_cpu_user_entry();
 		account_stolen_time();
 	} else {
+		kuap_save_and_lock(regs);
 		/*
 		 * CT_WARN_ON comes here via program_check_exception,
 		 * so avoid recursion.

arch/powerpc/include/asm/kup.h

@@ -91,7 +91,6 @@ static __always_inline void kuap_assert_locked(void)
 		__kuap_get_and_assert_locked();
 }
 
-#ifdef CONFIG_PPC32
 static __always_inline void kuap_lock(void)
 {
 	if (kuap_is_disabled())
@@ -107,7 +106,6 @@ static __always_inline void kuap_save_and_lock(struct pt_regs *regs)
 
 	__kuap_save_and_lock(regs);
 }
-#endif
 
 static __always_inline void kuap_kernel_restore(struct pt_regs *regs, unsigned long amr)
 {

arch/powerpc/kernel/process.c

@@ -1315,9 +1315,9 @@ struct task_struct *__switch_to(struct task_struct *prev,
 
 	set_return_regs_changed(); /* _switch changes stack (and regs) */
 
-#ifdef CONFIG_PPC32
-	kuap_assert_locked();
-#endif
+	if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64))
+		kuap_assert_locked();
+
 	last = _switch(old_thread, new_thread);
 
 	/*