powerpc/kuap: Use MMU_FTR_KUAP on all and refactor disabling kuap

All but book3s/64 use a static branch key for disabling kuap.
book3s/64 uses an mmu feature.

Refactor all targets to use MMU_FTR_KUAP like book3s/64.

For PPC32 that implies updating mmu features fixups once KUAP
has been initialised.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/6b3d7c977bad73378ea368bc6818e9c94ea95ab0.1689091022.git.christophe.leroy@csgroup.eu

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

@@ -9,10 +9,6 @@
 
 #ifndef __ASSEMBLY__
 
-#include <linux/jump_label.h>
-
-extern struct static_key_false disable_kuap_key;
-
 #ifdef CONFIG_PPC_KUAP
 
 #include <linux/sched.h>
@@ -20,11 +16,6 @@ extern struct static_key_false disable_kuap_key;
 #define KUAP_NONE	(~0UL)
 #define KUAP_ALL	(~1UL)
 
-static __always_inline bool kuap_is_disabled(void)
-{
-	return static_branch_unlikely(&disable_kuap_key);
-}
-
 static inline void kuap_lock_one(unsigned long addr)
 {
 	mtsr(mfsr(addr) | SR_KS, addr);

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

@@ -230,11 +230,6 @@ static inline u64 current_thread_iamr(void)
 
 #ifdef CONFIG_PPC_KUAP
 
-static __always_inline bool kuap_is_disabled(void)
-{
-	return !mmu_has_feature(MMU_FTR_KUAP);
-}
-
 static inline void kuap_user_restore(struct pt_regs *regs)
 {
 	bool restore_amr = false, restore_iamr = false;

arch/powerpc/include/asm/kup.h

@@ -6,6 +6,12 @@
 #define KUAP_WRITE	2
 #define KUAP_READ_WRITE	(KUAP_READ | KUAP_WRITE)
 
+#ifndef __ASSEMBLY__
+#include <linux/types.h>
+
+static __always_inline bool kuap_is_disabled(void);
+#endif
+
 #ifdef CONFIG_PPC_BOOK3S_64
 #include <asm/book3s/64/kup.h>
 #endif
@@ -41,6 +47,11 @@ void setup_kuep(bool disabled);
 
 #ifdef CONFIG_PPC_KUAP
 void setup_kuap(bool disabled);
+
+static __always_inline bool kuap_is_disabled(void)
+{
+	return !mmu_has_feature(MMU_FTR_KUAP);
+}
 #else
 static inline void setup_kuap(bool disabled) { }
 

arch/powerpc/include/asm/nohash/32/kup-8xx.h

@@ -9,17 +9,8 @@
 
 #ifndef __ASSEMBLY__
 
-#include <linux/jump_label.h>
-
 #include <asm/reg.h>
 
-extern struct static_key_false disable_kuap_key;
-
-static __always_inline bool kuap_is_disabled(void)
-{
-	return static_branch_unlikely(&disable_kuap_key);
-}
-
 static inline void __kuap_save_and_lock(struct pt_regs *regs)
 {
 	regs->kuap = mfspr(SPRN_MD_AP);

arch/powerpc/include/asm/nohash/kup-booke.h

@@ -13,18 +13,10 @@
 
 #else
 
-#include <linux/jump_label.h>
 #include <linux/sched.h>
 
 #include <asm/reg.h>
 
-extern struct static_key_false disable_kuap_key;
-
-static __always_inline bool kuap_is_disabled(void)
-{
-	return static_branch_unlikely(&disable_kuap_key);
-}
-
 static inline void __kuap_lock(void)
 {
 	mtspr(SPRN_PID, 0);

arch/powerpc/kernel/cputable.c

@@ -75,6 +75,10 @@ static struct cpu_spec * __init setup_cpu_spec(unsigned long offset,
 		t->cpu_features |= old.cpu_features & CPU_FTR_PMAO_BUG;
 	}
 
+	/* Set kuap ON at startup, will be disabled later if cmdline has 'nosmap' */
+	if (IS_ENABLED(CONFIG_PPC_KUAP) && IS_ENABLED(CONFIG_PPC32))
+		t->mmu_features |= MMU_FTR_KUAP;
+
 	*PTRRELOC(&cur_cpu_spec) = &the_cpu_spec;
 
 	/*

arch/powerpc/mm/book3s32/kuap.c

@@ -3,9 +3,6 @@
 #include <asm/kup.h>
 #include <asm/smp.h>
 
-struct static_key_false disable_kuap_key;
-EXPORT_SYMBOL(disable_kuap_key);
-
 void kuap_lock_all_ool(void)
 {
 	kuap_lock_all();
@@ -30,7 +27,7 @@ void setup_kuap(bool disabled)
 		return;
 
 	if (disabled)
-		static_branch_enable(&disable_kuap_key);
+		cur_cpu_spec->mmu_features &= ~MMU_FTR_KUAP;
 	else
 		pr_info("Activating Kernel Userspace Access Protection\n");
 }

arch/powerpc/mm/init_32.c

@@ -126,6 +126,8 @@ void __init MMU_init(void)
 
 	setup_kup();
 
+	update_mmu_feature_fixups(MMU_FTR_KUAP);
+
 	/* Shortly after that, the entire linear mapping will be available */
 	memblock_set_current_limit(lowmem_end_addr);
 }

arch/powerpc/mm/nohash/kup.c

@@ -5,7 +5,6 @@
 
 #include <linux/export.h>
 #include <linux/init.h>
-#include <linux/jump_label.h>
 #include <linux/printk.h>
 #include <linux/smp.h>
 
@@ -13,16 +12,13 @@
 #include <asm/smp.h>
 
 #ifdef CONFIG_PPC_KUAP
-struct static_key_false disable_kuap_key;
-EXPORT_SYMBOL(disable_kuap_key);
-
 void setup_kuap(bool disabled)
 {
 	if (disabled) {
 		if (IS_ENABLED(CONFIG_40x))
 			disable_kuep = true;
 		if (smp_processor_id() == boot_cpuid)
-			static_branch_enable(&disable_kuap_key);
+			cur_cpu_spec->mmu_features &= ~MMU_FTR_KUAP;
 		return;
 	}