Merge branch 'for-next/entry' into for-next/core

* for-next/entry:
  : More entry.S clean-ups and conversion to C.
  arm64: entry: call exit_to_user_mode() from C
  arm64: entry: move bulk of ret_to_user to C
  arm64: entry: clarify entry/exit helpers
  arm64: entry: consolidate entry/exit helpers

4 files changed, 162 insertions, 113 deletions

diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h
index 4afbc45b8bb0..339477dca551 100644
--- a/arch/arm64/include/asm/exception.h
+++ b/arch/arm64/include/asm/exception.h
@@ -55,8 +55,8 @@ asmlinkage void el0t_32_error_handler(struct pt_regs *regs);
 
 asmlinkage void call_on_irq_stack(struct pt_regs *regs,
 				  void (*func)(struct pt_regs *));
-asmlinkage void enter_from_user_mode(void);
-asmlinkage void exit_to_user_mode(void);
+asmlinkage void asm_exit_to_user_mode(struct pt_regs *regs);
+
 void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs);
 void do_undefinstr(struct pt_regs *regs);
 void do_bti(struct pt_regs *regs);
@@ -73,6 +73,7 @@ void do_el0_svc(struct pt_regs *regs);
 void do_el0_svc_compat(struct pt_regs *regs);
 void do_ptrauth_fault(struct pt_regs *regs, unsigned int esr);
 void do_serror(struct pt_regs *regs, unsigned int esr);
+void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags);
 
 void panic_bad_stack(struct pt_regs *regs, unsigned int esr, unsigned long far);
 #endif	/* __ASM_EXCEPTION_H */
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index db8b2e2d02c2..32f9796c4ffe 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -26,10 +26,14 @@
 #include <asm/system_misc.h>
 
 /*
+ * Handle IRQ/context state management when entering from kernel mode.
+ * Before this function is called it is not safe to call regular kernel code,
+ * intrumentable code, or any code which may trigger an exception.
+ *
  * This is intended to match the logic in irqentry_enter(), handling the kernel
  * mode transitions only.
  */
-static void noinstr enter_from_kernel_mode(struct pt_regs *regs)
+static __always_inline void __enter_from_kernel_mode(struct pt_regs *regs)
 {
 	regs->exit_rcu = false;
 
@@ -45,20 +49,26 @@ static void noinstr enter_from_kernel_mode(struct pt_regs *regs)
 	lockdep_hardirqs_off(CALLER_ADDR0);
 	rcu_irq_enter_check_tick();
 	trace_hardirqs_off_finish();
+}
 
+static void noinstr enter_from_kernel_mode(struct pt_regs *regs)
+{
+	__enter_from_kernel_mode(regs);
 	mte_check_tfsr_entry();
 }
 
 /*
+ * Handle IRQ/context state management when exiting to kernel mode.
+ * After this function returns it is not safe to call regular kernel code,
+ * intrumentable code, or any code which may trigger an exception.
+ *
  * This is intended to match the logic in irqentry_exit(), handling the kernel
  * mode transitions only, and with preemption handled elsewhere.
  */
-static void noinstr exit_to_kernel_mode(struct pt_regs *regs)
+static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs)
 {
 	lockdep_assert_irqs_disabled();
 
-	mte_check_tfsr_exit();
-
 	if (interrupts_enabled(regs)) {
 		if (regs->exit_rcu) {
 			trace_hardirqs_on_prepare();
@@ -75,6 +85,71 @@ static void noinstr exit_to_kernel_mode(struct pt_regs *regs)
 	}
 }
 
+static void noinstr exit_to_kernel_mode(struct pt_regs *regs)
+{
+	mte_check_tfsr_exit();
+	__exit_to_kernel_mode(regs);
+}
+
+/*
+ * Handle IRQ/context state management when entering from user mode.
+ * Before this function is called it is not safe to call regular kernel code,
+ * intrumentable code, or any code which may trigger an exception.
+ */
+static __always_inline void __enter_from_user_mode(void)
+{
+	lockdep_hardirqs_off(CALLER_ADDR0);
+	CT_WARN_ON(ct_state() != CONTEXT_USER);
+	user_exit_irqoff();
+	trace_hardirqs_off_finish();
+}
+
+static __always_inline void enter_from_user_mode(struct pt_regs *regs)
+{
+	__enter_from_user_mode();
+}
+
+/*
+ * Handle IRQ/context state management when exiting to user mode.
+ * After this function returns it is not safe to call regular kernel code,
+ * intrumentable code, or any code which may trigger an exception.
+ */
+static __always_inline void __exit_to_user_mode(void)
+{
+	trace_hardirqs_on_prepare();
+	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
+	user_enter_irqoff();
+	lockdep_hardirqs_on(CALLER_ADDR0);
+}
+
+static __always_inline void prepare_exit_to_user_mode(struct pt_regs *regs)
+{
+	unsigned long flags;
+
+	local_daif_mask();
+
+	flags = READ_ONCE(current_thread_info()->flags);
+	if (unlikely(flags & _TIF_WORK_MASK))
+		do_notify_resume(regs, flags);
+}
+
+static __always_inline void exit_to_user_mode(struct pt_regs *regs)
+{
+	prepare_exit_to_user_mode(regs);
+	mte_check_tfsr_exit();
+	__exit_to_user_mode();
+}
+
+asmlinkage void noinstr asm_exit_to_user_mode(struct pt_regs *regs)
+{
+	exit_to_user_mode(regs);
+}
+
+/*
+ * Handle IRQ/context state management when entering an NMI from user/kernel
+ * mode. Before this function is called it is not safe to call regular kernel
+ * code, intrumentable code, or any code which may trigger an exception.
+ */
 static void noinstr arm64_enter_nmi(struct pt_regs *regs)
 {
 	regs->lockdep_hardirqs = lockdep_hardirqs_enabled();
@@ -88,6 +163,11 @@ static void noinstr arm64_enter_nmi(struct pt_regs *regs)
 	ftrace_nmi_enter();
 }
 
+/*
+ * Handle IRQ/context state management when exiting an NMI from user/kernel
+ * mode. After this function returns it is not safe to call regular kernel
+ * code, intrumentable code, or any code which may trigger an exception.
+ */
 static void noinstr arm64_exit_nmi(struct pt_regs *regs)
 {
 	bool restore = regs->lockdep_hardirqs;
@@ -105,6 +185,40 @@ static void noinstr arm64_exit_nmi(struct pt_regs *regs)
 	__nmi_exit();
 }
 
+/*
+ * Handle IRQ/context state management when entering a debug exception from
+ * kernel mode. Before this function is called it is not safe to call regular
+ * kernel code, intrumentable code, or any code which may trigger an exception.
+ */
+static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs)
+{
+	regs->lockdep_hardirqs = lockdep_hardirqs_enabled();
+
+	lockdep_hardirqs_off(CALLER_ADDR0);
+	rcu_nmi_enter();
+
+	trace_hardirqs_off_finish();
+}
+
+/*
+ * Handle IRQ/context state management when exiting a debug exception from
+ * kernel mode. After this function returns it is not safe to call regular
+ * kernel code, intrumentable code, or any code which may trigger an exception.
+ */
+static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
+{
+	bool restore = regs->lockdep_hardirqs;
+
+	if (restore) {
+		trace_hardirqs_on_prepare();
+		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
+	}
+
+	rcu_nmi_exit();
+	if (restore)
+		lockdep_hardirqs_on(CALLER_ADDR0);
+}
+
 static void noinstr enter_el1_irq_or_nmi(struct pt_regs *regs)
 {
 	if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && !interrupts_enabled(regs))
@@ -265,30 +379,6 @@ static void noinstr el1_undef(struct pt_regs *regs)
 	exit_to_kernel_mode(regs);
 }
 
-static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs)
-{
-	regs->lockdep_hardirqs = lockdep_hardirqs_enabled();
-
-	lockdep_hardirqs_off(CALLER_ADDR0);
-	rcu_nmi_enter();
-
-	trace_hardirqs_off_finish();
-}
-
-static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
-{
-	bool restore = regs->lockdep_hardirqs;
-
-	if (restore) {
-		trace_hardirqs_on_prepare();
-		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
-	}
-
-	rcu_nmi_exit();
-	if (restore)
-		lockdep_hardirqs_on(CALLER_ADDR0);
-}
-
 static void noinstr el1_dbg(struct pt_regs *regs, unsigned long esr)
 {
 	unsigned long far = read_sysreg(far_el1);
@@ -382,31 +472,14 @@ asmlinkage void noinstr el1h_64_error_handler(struct pt_regs *regs)
 	arm64_exit_nmi(regs);
 }
 
-asmlinkage void noinstr enter_from_user_mode(void)
-{
-	lockdep_hardirqs_off(CALLER_ADDR0);
-	CT_WARN_ON(ct_state() != CONTEXT_USER);
-	user_exit_irqoff();
-	trace_hardirqs_off_finish();
-}
-
-asmlinkage void noinstr exit_to_user_mode(void)
-{
-	mte_check_tfsr_exit();
-
-	trace_hardirqs_on_prepare();
-	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
-	user_enter_irqoff();
-	lockdep_hardirqs_on(CALLER_ADDR0);
-}
-
 static void noinstr el0_da(struct pt_regs *regs, unsigned long esr)
 {
 	unsigned long far = read_sysreg(far_el1);
 
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_mem_abort(far, esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_ia(struct pt_regs *regs, unsigned long esr)
@@ -421,37 +494,42 @@ static void noinstr el0_ia(struct pt_regs *regs, unsigned long esr)
 	if (!is_ttbr0_addr(far))
 		arm64_apply_bp_hardening();
 
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_mem_abort(far, esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_fpsimd_acc(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_fpsimd_acc(esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_sve_acc(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_sve_acc(esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_fpsimd_exc(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_fpsimd_exc(esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_sys(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_sysinstr(esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_pc(struct pt_regs *regs, unsigned long esr)
@@ -461,37 +539,42 @@ static void noinstr el0_pc(struct pt_regs *regs, unsigned long esr)
 	if (!is_ttbr0_addr(instruction_pointer(regs)))
 		arm64_apply_bp_hardening();
 
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_sp_pc_abort(far, esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_sp(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_sp_pc_abort(regs->sp, esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_undef(struct pt_regs *regs)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_undefinstr(regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_bti(struct pt_regs *regs)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_bti(regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_inv(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	bad_el0_sync(regs, 0, esr);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_dbg(struct pt_regs *regs, unsigned long esr)
@@ -499,23 +582,26 @@ static void noinstr el0_dbg(struct pt_regs *regs, unsigned long esr)
 	/* Only watchpoints write FAR_EL1, otherwise its UNKNOWN */
 	unsigned long far = read_sysreg(far_el1);
 
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	do_debug_exception(far, esr, regs);
 	local_daif_restore(DAIF_PROCCTX);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_svc(struct pt_regs *regs)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	cortex_a76_erratum_1463225_svc_handler();
 	do_el0_svc(regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_fpac(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_ptrauth_fault(regs, esr);
+	exit_to_user_mode(regs);
 }
 
 asmlinkage void noinstr el0t_64_sync_handler(struct pt_regs *regs)
@@ -574,7 +660,7 @@ asmlinkage void noinstr el0t_64_sync_handler(struct pt_regs *regs)
 static void noinstr el0_interrupt(struct pt_regs *regs,
 				  void (*handler)(struct pt_regs *))
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 
 	write_sysreg(DAIF_PROCCTX_NOIRQ, daif);
 
@@ -582,6 +668,8 @@ static void noinstr el0_interrupt(struct pt_regs *regs,
 		arm64_apply_bp_hardening();
 
 	do_interrupt_handler(regs, handler);
+
+	exit_to_user_mode(regs);
 }
 
 static void noinstr __el0_irq_handler_common(struct pt_regs *regs)
@@ -608,12 +696,13 @@ static void noinstr __el0_error_handler_common(struct pt_regs *regs)
 {
 	unsigned long esr = read_sysreg(esr_el1);
 
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_ERRCTX);
 	arm64_enter_nmi(regs);
 	do_serror(regs, esr);
 	arm64_exit_nmi(regs);
 	local_daif_restore(DAIF_PROCCTX);
+	exit_to_user_mode(regs);
 }
 
 asmlinkage void noinstr el0t_64_error_handler(struct pt_regs *regs)
@@ -624,16 +713,18 @@ asmlinkage void noinstr el0t_64_error_handler(struct pt_regs *regs)
 #ifdef CONFIG_COMPAT
 static void noinstr el0_cp15(struct pt_regs *regs, unsigned long esr)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	local_daif_restore(DAIF_PROCCTX);
 	do_cp15instr(esr, regs);
+	exit_to_user_mode(regs);
 }
 
 static void noinstr el0_svc_compat(struct pt_regs *regs)
 {
-	enter_from_user_mode();
+	enter_from_user_mode(regs);
 	cortex_a76_erratum_1463225_svc_handler();
 	do_el0_svc_compat(regs);
+	exit_to_user_mode(regs);
 }
 
 asmlinkage void noinstr el0t_32_sync_handler(struct pt_regs *regs)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 572f72f20646..bc6d5a970a13 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -29,16 +29,6 @@
 #include <asm/asm-uaccess.h>
 #include <asm/unistd.h>
 
-/*
- * Context tracking and irqflag tracing need to instrument transitions between
- * user and kernel mode.
- */
-	.macro user_enter_irqoff
-#if defined(CONFIG_CONTEXT_TRACKING) || defined(CONFIG_TRACE_IRQFLAGS)
-	bl	exit_to_user_mode
-#endif
-	.endm
-
 	.macro	clear_gp_regs
 	.irp	n,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29
 	mov	x\n, xzr
@@ -492,18 +482,6 @@ SYM_CODE_END(__swpan_exit_el0)
 /* GPRs used by entry code */
 tsk	.req	x28		// current thread_info
 
-/*
- * Interrupt handling.
- */
-	.macro	gic_prio_kentry_setup, tmp:req
-#ifdef CONFIG_ARM64_PSEUDO_NMI
-	alternative_if ARM64_HAS_IRQ_PRIO_MASKING
-	mov	\tmp, #(GIC_PRIO_PSR_I_SET | GIC_PRIO_IRQON)
-	msr_s	SYS_ICC_PMR_EL1, \tmp
-	alternative_else_nop_endif
-#endif
-	.endm
-
 	.text
 
 /*
@@ -605,35 +583,13 @@ SYM_CODE_START_LOCAL(ret_to_kernel)
 	kernel_exit 1
 SYM_CODE_END(ret_to_kernel)
 
-/*
- * "slow" syscall return path.
- */
 SYM_CODE_START_LOCAL(ret_to_user)
-	disable_daif
-	gic_prio_kentry_setup tmp=x3
-#ifdef CONFIG_TRACE_IRQFLAGS
-	bl	trace_hardirqs_off
-#endif
-	ldr	x19, [tsk, #TSK_TI_FLAGS]
-	and	x2, x19, #_TIF_WORK_MASK
-	cbnz	x2, work_pending
-finish_ret_to_user:
-	user_enter_irqoff
+	ldr	x19, [tsk, #TSK_TI_FLAGS]	// re-check for single-step
 	enable_step_tsk x19, x2
 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
 	bl	stackleak_erase
 #endif
 	kernel_exit 0
-
-/*
- * Ok, we need to do extra processing, enter the slow path.
- */
-work_pending:
-	mov	x0, sp				// 'regs'
-	mov	x1, x19
-	bl	do_notify_resume
-	ldr	x19, [tsk, #TSK_TI_FLAGS]	// re-check for single-step
-	b	finish_ret_to_user
 SYM_CODE_END(ret_to_user)
 
 	.popsection				// .entry.text
@@ -799,6 +755,8 @@ SYM_CODE_START(ret_from_fork)
 	mov	x0, x20
 	blr	x19
 1:	get_current_task tsk
+	mov	x0, sp
+	bl	asm_exit_to_user_mode
 	b	ret_to_user
 SYM_CODE_END(ret_from_fork)
 NOKPROBE(ret_from_fork)
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 3b4c927d31ff..e93ffd7d38e1 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -929,8 +929,7 @@ static bool cpu_affinity_invalid(struct pt_regs *regs)
 				 system_32bit_el0_cpumask());
 }
 
-asmlinkage void do_notify_resume(struct pt_regs *regs,
-				 unsigned long thread_flags)
+void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
 {
 	do {
 		if (thread_flags & _TIF_NEED_RESCHED) {