[linux-2.6-block.git] / kernel / entry / common.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/context_tracking.h>
#include <linux/entry-common.h>
#include <linux/livepatch.h>
#include <linux/audit.h>

#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>

/**
 * enter_from_user_mode - Establish state when coming from user mode
 *
 * Syscall/interrupt entry disables interrupts, but user mode is traced as
 * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
 *
 * 1) Tell lockdep that interrupts are disabled
 * 2) Invoke context tracking if enabled to reactivate RCU
 * 3) Trace interrupts off state
 */
static __always_inline void enter_from_user_mode(struct pt_regs *regs)
{
	arch_check_user_regs(regs);
	lockdep_hardirqs_off(CALLER_ADDR0);

	CT_WARN_ON(ct_state() != CONTEXT_USER);
	user_exit_irqoff();

	instrumentation_begin();
	trace_hardirqs_off_finish();
	instrumentation_end();
}

static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
{
	if (unlikely(audit_context())) {
		unsigned long args[6];

		syscall_get_arguments(current, regs, args);
		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
	}
}

static long syscall_trace_enter(struct pt_regs *regs, long syscall,
				unsigned long ti_work, unsigned long work)
{
	long ret = 0;

	/* Handle ptrace */
	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
		ret = arch_syscall_enter_tracehook(regs);
		if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
			return -1L;
	}

	/* Do seccomp after ptrace, to catch any tracer changes. */
	if (work & SYSCALL_WORK_SECCOMP) {
		ret = __secure_computing(NULL);
		if (ret == -1L)
			return ret;
	}

	/* Either of the above might have changed the syscall number */
	syscall = syscall_get_nr(current, regs);

	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
		trace_sys_enter(regs, syscall);

	syscall_enter_audit(regs, syscall);

	return ret ? : syscall;
}

static __always_inline long
__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
{
	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
	unsigned long ti_work;

	ti_work = READ_ONCE(current_thread_info()->flags);
	if (work & SYSCALL_WORK_ENTER || ti_work & SYSCALL_ENTER_WORK)
		syscall = syscall_trace_enter(regs, syscall, ti_work, work);

	return syscall;
}

long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
{
	return __syscall_enter_from_user_work(regs, syscall);
}

noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
{
	long ret;

	enter_from_user_mode(regs);

	instrumentation_begin();
	local_irq_enable();
	ret = __syscall_enter_from_user_work(regs, syscall);
	instrumentation_end();

	return ret;
}

noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
{
	enter_from_user_mode(regs);
	instrumentation_begin();
	local_irq_enable();
	instrumentation_end();
}

/**
 * exit_to_user_mode - Fixup state when exiting to user mode
 *
 * Syscall/interupt exit enables interrupts, but the kernel state is
 * interrupts disabled when this is invoked. Also tell RCU about it.
 *
 * 1) Trace interrupts on state
 * 2) Invoke context tracking if enabled to adjust RCU state
 * 3) Invoke architecture specific last minute exit code, e.g. speculation
 *    mitigations, etc.
 * 4) Tell lockdep that interrupts are enabled
 */
static __always_inline void exit_to_user_mode(void)
{
	instrumentation_begin();
	trace_hardirqs_on_prepare();
	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	instrumentation_end();

	user_enter_irqoff();
	arch_exit_to_user_mode();
	lockdep_hardirqs_on(CALLER_ADDR0);
}

/* Workaround to allow gradual conversion of architecture code */
void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }

static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
{
	if (ti_work & _TIF_NOTIFY_SIGNAL)
		tracehook_notify_signal();

	arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
}

static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
					    unsigned long ti_work)
{
	/*
	 * Before returning to user space ensure that all pending work
	 * items have been completed.
	 */
	while (ti_work & EXIT_TO_USER_MODE_WORK) {

		local_irq_enable_exit_to_user(ti_work);

		if (ti_work & _TIF_NEED_RESCHED)
			schedule();

		if (ti_work & _TIF_UPROBE)
			uprobe_notify_resume(regs);

		if (ti_work & _TIF_PATCH_PENDING)
			klp_update_patch_state(current);

		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
			handle_signal_work(regs, ti_work);

		if (ti_work & _TIF_NOTIFY_RESUME) {
			tracehook_notify_resume(regs);
			rseq_handle_notify_resume(NULL, regs);
		}

		/* Architecture specific TIF work */
		arch_exit_to_user_mode_work(regs, ti_work);

		/*
		 * Disable interrupts and reevaluate the work flags as they
		 * might have changed while interrupts and preemption was
		 * enabled above.
		 */
		local_irq_disable_exit_to_user();
		ti_work = READ_ONCE(current_thread_info()->flags);
	}

	/* Return the latest work state for arch_exit_to_user_mode() */
	return ti_work;
}

static void exit_to_user_mode_prepare(struct pt_regs *regs)
{
	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);

	lockdep_assert_irqs_disabled();

	if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
		ti_work = exit_to_user_mode_loop(regs, ti_work);

	arch_exit_to_user_mode_prepare(regs, ti_work);

	/* Ensure that the address limit is intact and no locks are held */
	addr_limit_user_check();
	lockdep_assert_irqs_disabled();
	lockdep_sys_exit();
}

#ifndef _TIF_SINGLESTEP
static inline bool report_single_step(unsigned long work)
{
	return false;
}
#else
/*
 * If SYSCALL_EMU is set, then the only reason to report is when
 * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).  This syscall
 * instruction has been already reported in syscall_enter_from_user_mode().
 */
static inline bool report_single_step(unsigned long work)
{
	if (!(work & SYSCALL_WORK_SYSCALL_EMU))
		return false;

	return !!(current_thread_info()->flags & _TIF_SINGLESTEP);
}
#endif

static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work,
			      unsigned long work)
{
	bool step;

	audit_syscall_exit(regs);

	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
		trace_sys_exit(regs, syscall_get_return_value(current, regs));

	step = report_single_step(work);
	if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
		arch_syscall_exit_tracehook(regs, step);
}

/*
 * Syscall specific exit to user mode preparation. Runs with interrupts
 * enabled.
 */
static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
{
	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
	u32 cached_flags = READ_ONCE(current_thread_info()->flags);
	unsigned long nr = syscall_get_nr(current, regs);

	CT_WARN_ON(ct_state() != CONTEXT_KERNEL);

	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
		if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
			local_irq_enable();
	}

	rseq_syscall(regs);

	/*
	 * Do one-time syscall specific work. If these work items are
	 * enabled, we want to run them exactly once per syscall exit with
	 * interrupts enabled.
	 */
	if (unlikely(work & SYSCALL_WORK_EXIT || cached_flags & SYSCALL_EXIT_WORK))
		syscall_exit_work(regs, cached_flags, work);
}

__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
{
	instrumentation_begin();
	syscall_exit_to_user_mode_prepare(regs);
	local_irq_disable_exit_to_user();
	exit_to_user_mode_prepare(regs);
	instrumentation_end();
	exit_to_user_mode();
}

noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
{
	enter_from_user_mode(regs);
}

noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
{
	instrumentation_begin();
	exit_to_user_mode_prepare(regs);
	instrumentation_end();
	exit_to_user_mode();
}

noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
{
	irqentry_state_t ret = {
		.exit_rcu = false,
	};

	if (user_mode(regs)) {
		irqentry_enter_from_user_mode(regs);
		return ret;
	}

	/*
	 * If this entry hit the idle task invoke rcu_irq_enter() whether
	 * RCU is watching or not.
	 *
	 * Interrupts can nest when the first interrupt invokes softirq
	 * processing on return which enables interrupts.
	 *
	 * Scheduler ticks in the idle task can mark quiescent state and
	 * terminate a grace period, if and only if the timer interrupt is
	 * not nested into another interrupt.
	 *
	 * Checking for rcu_is_watching() here would prevent the nesting
	 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
	 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
	 * assume that it is the first interupt and eventually claim
	 * quiescent state and end grace periods prematurely.
	 *
	 * Unconditionally invoke rcu_irq_enter() so RCU state stays
	 * consistent.
	 *
	 * TINY_RCU does not support EQS, so let the compiler eliminate
	 * this part when enabled.
	 */
	if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
		/*
		 * If RCU is not watching then the same careful
		 * sequence vs. lockdep and tracing is required
		 * as in irqentry_enter_from_user_mode().
		 */
		lockdep_hardirqs_off(CALLER_ADDR0);
		rcu_irq_enter();
		instrumentation_begin();
		trace_hardirqs_off_finish();
		instrumentation_end();

		ret.exit_rcu = true;
		return ret;
	}

	/*
	 * If RCU is watching then RCU only wants to check whether it needs
	 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
	 * already contains a warning when RCU is not watching, so no point
	 * in having another one here.
	 */
	lockdep_hardirqs_off(CALLER_ADDR0);
	instrumentation_begin();
	rcu_irq_enter_check_tick();
	trace_hardirqs_off_finish();
	instrumentation_end();

	return ret;
}

void irqentry_exit_cond_resched(void)
{
	if (!preempt_count()) {
		/* Sanity check RCU and thread stack */
		rcu_irq_exit_check_preempt();
		if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
			WARN_ON_ONCE(!on_thread_stack());
		if (need_resched())
			preempt_schedule_irq();
	}
}

noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
{
	lockdep_assert_irqs_disabled();

	/* Check whether this returns to user mode */
	if (user_mode(regs)) {
		irqentry_exit_to_user_mode(regs);
	} else if (!regs_irqs_disabled(regs)) {
		/*
		 * If RCU was not watching on entry this needs to be done
		 * carefully and needs the same ordering of lockdep/tracing
		 * and RCU as the return to user mode path.
		 */
		if (state.exit_rcu) {
			instrumentation_begin();
			/* Tell the tracer that IRET will enable interrupts */
			trace_hardirqs_on_prepare();
			lockdep_hardirqs_on_prepare(CALLER_ADDR0);
			instrumentation_end();
			rcu_irq_exit();
			lockdep_hardirqs_on(CALLER_ADDR0);
			return;
		}

		instrumentation_begin();
		if (IS_ENABLED(CONFIG_PREEMPTION))
			irqentry_exit_cond_resched();
		/* Covers both tracing and lockdep */
		trace_hardirqs_on();
		instrumentation_end();
	} else {
		/*
		 * IRQ flags state is correct already. Just tell RCU if it
		 * was not watching on entry.
		 */
		if (state.exit_rcu)
			rcu_irq_exit();
	}
}

irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
{
	irqentry_state_t irq_state;

	irq_state.lockdep = lockdep_hardirqs_enabled();

	__nmi_enter();
	lockdep_hardirqs_off(CALLER_ADDR0);
	lockdep_hardirq_enter();
	rcu_nmi_enter();

	instrumentation_begin();
	trace_hardirqs_off_finish();
	ftrace_nmi_enter();
	instrumentation_end();

	return irq_state;
}

void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
{
	instrumentation_begin();
	ftrace_nmi_exit();
	if (irq_state.lockdep) {
		trace_hardirqs_on_prepare();
		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	}
	instrumentation_end();

	rcu_nmi_exit();
	lockdep_hardirq_exit();
	if (irq_state.lockdep)
		lockdep_hardirqs_on(CALLER_ADDR0);
	__nmi_exit();
}
Commit	Line	Data
142781e1 TG	1	// SPDX-License-Identifier: GPL-2.0
	2
	3	#include <linux/context_tracking.h>
	4	#include <linux/entry-common.h>
a9f3a74a TG	5	#include <linux/livepatch.h>
a9f3a74a TG	6	#include <linux/audit.h>
142781e1 TG	7
	8	#define CREATE_TRACE_POINTS
	9	#include <trace/events/syscalls.h>
	10
	11	/**
	12	* enter_from_user_mode - Establish state when coming from user mode
	13	*
	14	* Syscall/interrupt entry disables interrupts, but user mode is traced as
	15	* interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
	16	*
	17	* 1) Tell lockdep that interrupts are disabled
	18	* 2) Invoke context tracking if enabled to reactivate RCU
	19	* 3) Trace interrupts off state
	20	*/
	21	static __always_inline void enter_from_user_mode(struct pt_regs *regs)
	22	{
	23	arch_check_user_regs(regs);
	24	lockdep_hardirqs_off(CALLER_ADDR0);
	25
	26	CT_WARN_ON(ct_state() != CONTEXT_USER);
	27	user_exit_irqoff();
	28
	29	instrumentation_begin();
	30	trace_hardirqs_off_finish();
	31	instrumentation_end();
	32	}
	33
	34	static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
	35	{
	36	if (unlikely(audit_context())) {
	37	unsigned long args[6];
	38
	39	syscall_get_arguments(current, regs, args);
	40	audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
	41	}
	42	}
	43
	44	static long syscall_trace_enter(struct pt_regs *regs, long syscall,
b86678cf	45	unsigned long ti_work, unsigned long work)
142781e1 TG	46	{
	47	long ret = 0;
	48
	49	/* Handle ptrace */
64eb35f7	50	if (work & (SYSCALL_WORK_SYSCALL_TRACE \| SYSCALL_WORK_SYSCALL_EMU)) {
142781e1	51	ret = arch_syscall_enter_tracehook(regs);
64eb35f7	52	if (ret \|\| (work & SYSCALL_WORK_SYSCALL_EMU))
142781e1 TG	53	return -1L;
	54	}
	55
	56	/* Do seccomp after ptrace, to catch any tracer changes. */
23d67a54	57	if (work & SYSCALL_WORK_SECCOMP) {
142781e1 TG	58	ret = __secure_computing(NULL);
	59	if (ret == -1L)
	60	return ret;
	61	}
	62
b6ec4134 KC	63	/* Either of the above might have changed the syscall number */
	64	syscall = syscall_get_nr(current, regs);
	65
524666cb	66	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
142781e1 TG	67	trace_sys_enter(regs, syscall);
	68
	69	syscall_enter_audit(regs, syscall);
	70
	71	return ret ? : syscall;
	72	}
	73
4facb95b TG	74	static __always_inline long
4facb95b TG	75	__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
142781e1	76	{
b86678cf	77	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
142781e1 TG	78	unsigned long ti_work;
142781e1 TG	79
142781e1	80	ti_work = READ_ONCE(current_thread_info()->flags);
b86678cf GKB	81	if (work & SYSCALL_WORK_ENTER \|\| ti_work & SYSCALL_ENTER_WORK)
b86678cf GKB	82	syscall = syscall_trace_enter(regs, syscall, ti_work, work);
142781e1 TG	83
	84	return syscall;
	85	}
	86
4facb95b TG	87	long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
	88	{
	89	return __syscall_enter_from_user_work(regs, syscall);
	90	}
	91
	92	noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
	93	{
	94	long ret;
	95
	96	enter_from_user_mode(regs);
	97
	98	instrumentation_begin();
	99	local_irq_enable();
	100	ret = __syscall_enter_from_user_work(regs, syscall);
	101	instrumentation_end();
	102
	103	return ret;
	104	}
	105
	106	noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
	107	{
	108	enter_from_user_mode(regs);
	109	instrumentation_begin();
	110	local_irq_enable();
	111	instrumentation_end();
	112	}
	113
a9f3a74a TG	114	/**
	115	* exit_to_user_mode - Fixup state when exiting to user mode
	116	*
	117	* Syscall/interupt exit enables interrupts, but the kernel state is
	118	* interrupts disabled when this is invoked. Also tell RCU about it.
	119	*
	120	* 1) Trace interrupts on state
	121	* 2) Invoke context tracking if enabled to adjust RCU state
	122	* 3) Invoke architecture specific last minute exit code, e.g. speculation
	123	* mitigations, etc.
	124	* 4) Tell lockdep that interrupts are enabled
	125	*/
	126	static __always_inline void exit_to_user_mode(void)
	127	{
	128	instrumentation_begin();
	129	trace_hardirqs_on_prepare();
	130	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	131	instrumentation_end();
	132
	133	user_enter_irqoff();
	134	arch_exit_to_user_mode();
	135	lockdep_hardirqs_on(CALLER_ADDR0);
	136	}
	137
	138	/* Workaround to allow gradual conversion of architecture code */
12db8b69 JA	139	void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }
	140
	141	static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
	142	{
	143	if (ti_work & _TIF_NOTIFY_SIGNAL)
	144	tracehook_notify_signal();
	145
	146	arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
	147	}
a9f3a74a TG	148
	149	static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
	150	unsigned long ti_work)
	151	{
	152	/*
	153	* Before returning to user space ensure that all pending work
	154	* items have been completed.
	155	*/
	156	while (ti_work & EXIT_TO_USER_MODE_WORK) {
	157
	158	local_irq_enable_exit_to_user(ti_work);
	159
	160	if (ti_work & _TIF_NEED_RESCHED)
	161	schedule();
	162
	163	if (ti_work & _TIF_UPROBE)
	164	uprobe_notify_resume(regs);
	165
	166	if (ti_work & _TIF_PATCH_PENDING)
	167	klp_update_patch_state(current);
	168
12db8b69 JA	169	if (ti_work & (_TIF_SIGPENDING \| _TIF_NOTIFY_SIGNAL))
12db8b69 JA	170	handle_signal_work(regs, ti_work);
a9f3a74a TG	171
a9f3a74a TG	172	if (ti_work & _TIF_NOTIFY_RESUME) {
a9f3a74a TG	173	tracehook_notify_resume(regs);
	174	rseq_handle_notify_resume(NULL, regs);
	175	}
	176
	177	/* Architecture specific TIF work */
	178	arch_exit_to_user_mode_work(regs, ti_work);
	179
	180	/*
	181	* Disable interrupts and reevaluate the work flags as they
	182	* might have changed while interrupts and preemption was
	183	* enabled above.
	184	*/
	185	local_irq_disable_exit_to_user();
	186	ti_work = READ_ONCE(current_thread_info()->flags);
	187	}
	188
	189	/* Return the latest work state for arch_exit_to_user_mode() */
	190	return ti_work;
	191	}
	192
	193	static void exit_to_user_mode_prepare(struct pt_regs *regs)
	194	{
	195	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
	196
	197	lockdep_assert_irqs_disabled();
	198
	199	if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
	200	ti_work = exit_to_user_mode_loop(regs, ti_work);
	201
	202	arch_exit_to_user_mode_prepare(regs, ti_work);
	203
	204	/* Ensure that the address limit is intact and no locks are held */
	205	addr_limit_user_check();
	206	lockdep_assert_irqs_disabled();
	207	lockdep_sys_exit();
	208	}
	209
	210	#ifndef _TIF_SINGLESTEP
64eb35f7	211	static inline bool report_single_step(unsigned long work)
a9f3a74a TG	212	{
	213	return false;
	214	}
	215	#else
	216	/*
64eb35f7	217	* If SYSCALL_EMU is set, then the only reason to report is when
a9f3a74a	218	* TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
900ffe39	219	* instruction has been already reported in syscall_enter_from_user_mode().
a9f3a74a	220	*/
64eb35f7	221	static inline bool report_single_step(unsigned long work)
a9f3a74a	222	{
64eb35f7 GKB	223	if (!(work & SYSCALL_WORK_SYSCALL_EMU))
	224	return false;
	225
	226	return !!(current_thread_info()->flags & _TIF_SINGLESTEP);
a9f3a74a TG	227	}
	228	#endif
	229
b86678cf GKB	230	static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work,
b86678cf GKB	231	unsigned long work)
a9f3a74a TG	232	{
	233	bool step;
	234
	235	audit_syscall_exit(regs);
	236
524666cb	237	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
a9f3a74a TG	238	trace_sys_exit(regs, syscall_get_return_value(current, regs));
a9f3a74a TG	239
64eb35f7	240	step = report_single_step(work);
64c19ba2	241	if (step \|\| work & SYSCALL_WORK_SYSCALL_TRACE)
a9f3a74a TG	242	arch_syscall_exit_tracehook(regs, step);
	243	}
	244
	245	/*
	246	* Syscall specific exit to user mode preparation. Runs with interrupts
	247	* enabled.
	248	*/
	249	static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
	250	{
b86678cf	251	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
a9f3a74a TG	252	u32 cached_flags = READ_ONCE(current_thread_info()->flags);
	253	unsigned long nr = syscall_get_nr(current, regs);
	254
	255	CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
	256
	257	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
	258	if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
	259	local_irq_enable();
	260	}
	261
	262	rseq_syscall(regs);
	263
	264	/*
	265	* Do one-time syscall specific work. If these work items are
	266	* enabled, we want to run them exactly once per syscall exit with
	267	* interrupts enabled.
	268	*/
b86678cf GKB	269	if (unlikely(work & SYSCALL_WORK_EXIT \|\| cached_flags & SYSCALL_EXIT_WORK))
b86678cf GKB	270	syscall_exit_work(regs, cached_flags, work);
a9f3a74a TG	271	}
	272
	273	__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
	274	{
	275	instrumentation_begin();
	276	syscall_exit_to_user_mode_prepare(regs);
	277	local_irq_disable_exit_to_user();
	278	exit_to_user_mode_prepare(regs);
	279	instrumentation_end();
	280	exit_to_user_mode();
	281	}
	282
142781e1 TG	283	noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
	284	{
	285	enter_from_user_mode(regs);
	286	}
a9f3a74a TG	287
	288	noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
	289	{
	290	instrumentation_begin();
	291	exit_to_user_mode_prepare(regs);
	292	instrumentation_end();
	293	exit_to_user_mode();
	294	}
a5497bab	295
aadfc2f9	296	noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
a5497bab TG	297	{
	298	irqentry_state_t ret = {
	299	.exit_rcu = false,
	300	};
	301
	302	if (user_mode(regs)) {
	303	irqentry_enter_from_user_mode(regs);
	304	return ret;
	305	}
	306
	307	/*
	308	* If this entry hit the idle task invoke rcu_irq_enter() whether
	309	* RCU is watching or not.
	310	*
78a56e04	311	* Interrupts can nest when the first interrupt invokes softirq
a5497bab TG	312	* processing on return which enables interrupts.
	313	*
	314	* Scheduler ticks in the idle task can mark quiescent state and
	315	* terminate a grace period, if and only if the timer interrupt is
	316	* not nested into another interrupt.
	317	*
7f2a53c2	318	* Checking for rcu_is_watching() here would prevent the nesting
a5497bab TG	319	* interrupt to invoke rcu_irq_enter(). If that nested interrupt is
	320	* the tick then rcu_flavor_sched_clock_irq() would wrongfully
	321	* assume that it is the first interupt and eventually claim
78a56e04	322	* quiescent state and end grace periods prematurely.
a5497bab TG	323	*
	324	* Unconditionally invoke rcu_irq_enter() so RCU state stays
	325	* consistent.
	326	*
	327	* TINY_RCU does not support EQS, so let the compiler eliminate
	328	* this part when enabled.
	329	*/
	330	if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
	331	/*
	332	* If RCU is not watching then the same careful
	333	* sequence vs. lockdep and tracing is required
45ff5105	334	* as in irqentry_enter_from_user_mode().
a5497bab TG	335	*/
	336	lockdep_hardirqs_off(CALLER_ADDR0);
	337	rcu_irq_enter();
	338	instrumentation_begin();
	339	trace_hardirqs_off_finish();
	340	instrumentation_end();
	341
	342	ret.exit_rcu = true;
	343	return ret;
	344	}
	345
	346	/*
	347	* If RCU is watching then RCU only wants to check whether it needs
	348	* to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
	349	* already contains a warning when RCU is not watching, so no point
	350	* in having another one here.
	351	*/
9d820f68	352	lockdep_hardirqs_off(CALLER_ADDR0);
a5497bab TG	353	instrumentation_begin();
a5497bab TG	354	rcu_irq_enter_check_tick();
9d820f68	355	trace_hardirqs_off_finish();
a5497bab TG	356	instrumentation_end();
	357
	358	return ret;
	359	}
	360
	361	void irqentry_exit_cond_resched(void)
	362	{
	363	if (!preempt_count()) {
	364	/* Sanity check RCU and thread stack */
	365	rcu_irq_exit_check_preempt();
	366	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
	367	WARN_ON_ONCE(!on_thread_stack());
	368	if (need_resched())
	369	preempt_schedule_irq();
	370	}
	371	}
	372
aadfc2f9	373	noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
a5497bab TG	374	{
	375	lockdep_assert_irqs_disabled();
	376
	377	/* Check whether this returns to user mode */
	378	if (user_mode(regs)) {
	379	irqentry_exit_to_user_mode(regs);
	380	} else if (!regs_irqs_disabled(regs)) {
	381	/*
	382	* If RCU was not watching on entry this needs to be done
	383	* carefully and needs the same ordering of lockdep/tracing
	384	* and RCU as the return to user mode path.
	385	*/
	386	if (state.exit_rcu) {
	387	instrumentation_begin();
	388	/* Tell the tracer that IRET will enable interrupts */
	389	trace_hardirqs_on_prepare();
	390	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	391	instrumentation_end();
	392	rcu_irq_exit();
	393	lockdep_hardirqs_on(CALLER_ADDR0);
	394	return;
	395	}
	396
	397	instrumentation_begin();
	398	if (IS_ENABLED(CONFIG_PREEMPTION))
	399	irqentry_exit_cond_resched();
	400	/* Covers both tracing and lockdep */
	401	trace_hardirqs_on();
	402	instrumentation_end();
	403	} else {
	404	/*
	405	* IRQ flags state is correct already. Just tell RCU if it
	406	* was not watching on entry.
	407	*/
	408	if (state.exit_rcu)
	409	rcu_irq_exit();
	410	}
	411	}
b6be002b TG	412
	413	irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
	414	{
	415	irqentry_state_t irq_state;
	416
	417	irq_state.lockdep = lockdep_hardirqs_enabled();
	418
	419	__nmi_enter();
	420	lockdep_hardirqs_off(CALLER_ADDR0);
	421	lockdep_hardirq_enter();
	422	rcu_nmi_enter();
	423
	424	instrumentation_begin();
	425	trace_hardirqs_off_finish();
	426	ftrace_nmi_enter();
	427	instrumentation_end();
	428
	429	return irq_state;
	430	}
	431
	432	void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
	433	{
	434	instrumentation_begin();
	435	ftrace_nmi_exit();
	436	if (irq_state.lockdep) {
	437	trace_hardirqs_on_prepare();
	438	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	439	}
	440	instrumentation_end();
	441
	442	rcu_nmi_exit();
	443	lockdep_hardirq_exit();
	444	if (irq_state.lockdep)
	445	lockdep_hardirqs_on(CALLER_ADDR0);
	446	__nmi_exit();
	447	}