[linux-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>

#include "common.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 work)
{
	long ret = 0;

	/*
	 * Handle Syscall User Dispatch.  This must comes first, since
	 * the ABI here can be something that doesn't make sense for
	 * other syscall_work features.
	 */
	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
		if (syscall_user_dispatch(regs))
			return -1L;
	}

	/* 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);

	if (work & SYSCALL_WORK_ENTER)
		syscall = syscall_trace_enter(regs, syscall, 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 work)
{
	bool step;

	/*
	 * If the syscall was rolled back due to syscall user dispatching,
	 * then the tracers below are not invoked for the same reason as
	 * the entry side was not invoked in syscall_trace_enter(): The ABI
	 * of these syscalls is unknown.
	 */
	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
		if (unlikely(current->syscall_dispatch.on_dispatch)) {
			current->syscall_dispatch.on_dispatch = false;
			return;
		}
	}

	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);
	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))
		syscall_exit_work(regs, 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	7
11894468 GKB	8	#include "common.h"
11894468 GKB	9
142781e1 TG	10	#define CREATE_TRACE_POINTS
	11	#include <trace/events/syscalls.h>
	12
	13	/**
6666bb71	14	* __enter_from_user_mode - Establish state when coming from user mode
142781e1 TG	15	*
	16	* Syscall/interrupt entry disables interrupts, but user mode is traced as
	17	* interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
	18	*
	19	* 1) Tell lockdep that interrupts are disabled
	20	* 2) Invoke context tracking if enabled to reactivate RCU
	21	* 3) Trace interrupts off state
	22	*/
6666bb71	23	static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
142781e1 TG	24	{
	25	arch_check_user_regs(regs);
	26	lockdep_hardirqs_off(CALLER_ADDR0);
	27
	28	CT_WARN_ON(ct_state() != CONTEXT_USER);
	29	user_exit_irqoff();
	30
	31	instrumentation_begin();
	32	trace_hardirqs_off_finish();
	33	instrumentation_end();
	34	}
	35
	36	static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
	37	{
	38	if (unlikely(audit_context())) {
	39	unsigned long args[6];
	40
	41	syscall_get_arguments(current, regs, args);
	42	audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
	43	}
	44	}
	45
	46	static long syscall_trace_enter(struct pt_regs *regs, long syscall,
29915524	47	unsigned long work)
142781e1 TG	48	{
	49	long ret = 0;
	50
11894468 GKB	51	/*
	52	* Handle Syscall User Dispatch. This must comes first, since
	53	* the ABI here can be something that doesn't make sense for
	54	* other syscall_work features.
	55	*/
	56	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
	57	if (syscall_user_dispatch(regs))
	58	return -1L;
	59	}
	60
142781e1	61	/* Handle ptrace */
64eb35f7	62	if (work & (SYSCALL_WORK_SYSCALL_TRACE \| SYSCALL_WORK_SYSCALL_EMU)) {
142781e1	63	ret = arch_syscall_enter_tracehook(regs);
64eb35f7	64	if (ret \|\| (work & SYSCALL_WORK_SYSCALL_EMU))
142781e1 TG	65	return -1L;
	66	}
	67
	68	/* Do seccomp after ptrace, to catch any tracer changes. */
23d67a54	69	if (work & SYSCALL_WORK_SECCOMP) {
142781e1 TG	70	ret = __secure_computing(NULL);
	71	if (ret == -1L)
	72	return ret;
	73	}
	74
b6ec4134 KC	75	/* Either of the above might have changed the syscall number */
	76	syscall = syscall_get_nr(current, regs);
	77
524666cb	78	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
142781e1 TG	79	trace_sys_enter(regs, syscall);
	80
	81	syscall_enter_audit(regs, syscall);
	82
	83	return ret ? : syscall;
	84	}
	85
4facb95b TG	86	static __always_inline long
4facb95b TG	87	__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
142781e1	88	{
b86678cf	89	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
142781e1	90
29915524 GKB	91	if (work & SYSCALL_WORK_ENTER)
29915524 GKB	92	syscall = syscall_trace_enter(regs, syscall, work);
142781e1 TG	93
	94	return syscall;
	95	}
	96
4facb95b TG	97	long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
	98	{
	99	return __syscall_enter_from_user_work(regs, syscall);
	100	}
	101
	102	noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
	103	{
	104	long ret;
	105
6666bb71	106	__enter_from_user_mode(regs);
4facb95b TG	107
	108	instrumentation_begin();
	109	local_irq_enable();
	110	ret = __syscall_enter_from_user_work(regs, syscall);
	111	instrumentation_end();
	112
	113	return ret;
	114	}
	115
	116	noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
	117	{
6666bb71	118	__enter_from_user_mode(regs);
4facb95b TG	119	instrumentation_begin();
	120	local_irq_enable();
	121	instrumentation_end();
	122	}
	123
a9f3a74a	124	/**
bb793562	125	* __exit_to_user_mode - Fixup state when exiting to user mode
a9f3a74a TG	126	*
	127	* Syscall/interupt exit enables interrupts, but the kernel state is
	128	* interrupts disabled when this is invoked. Also tell RCU about it.
	129	*
	130	* 1) Trace interrupts on state
	131	* 2) Invoke context tracking if enabled to adjust RCU state
	132	* 3) Invoke architecture specific last minute exit code, e.g. speculation
	133	* mitigations, etc.
	134	* 4) Tell lockdep that interrupts are enabled
	135	*/
bb793562	136	static __always_inline void __exit_to_user_mode(void)
a9f3a74a TG	137	{
	138	instrumentation_begin();
	139	trace_hardirqs_on_prepare();
	140	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	141	instrumentation_end();
	142
	143	user_enter_irqoff();
	144	arch_exit_to_user_mode();
	145	lockdep_hardirqs_on(CALLER_ADDR0);
	146	}
	147
	148	/* Workaround to allow gradual conversion of architecture code */
12db8b69 JA	149	void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }
	150
	151	static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
	152	{
	153	if (ti_work & _TIF_NOTIFY_SIGNAL)
	154	tracehook_notify_signal();
	155
	156	arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
	157	}
a9f3a74a TG	158
	159	static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
	160	unsigned long ti_work)
	161	{
	162	/*
	163	* Before returning to user space ensure that all pending work
	164	* items have been completed.
	165	*/
	166	while (ti_work & EXIT_TO_USER_MODE_WORK) {
	167
	168	local_irq_enable_exit_to_user(ti_work);
	169
	170	if (ti_work & _TIF_NEED_RESCHED)
	171	schedule();
	172
	173	if (ti_work & _TIF_UPROBE)
	174	uprobe_notify_resume(regs);
	175
	176	if (ti_work & _TIF_PATCH_PENDING)
	177	klp_update_patch_state(current);
	178
12db8b69 JA	179	if (ti_work & (_TIF_SIGPENDING \| _TIF_NOTIFY_SIGNAL))
12db8b69 JA	180	handle_signal_work(regs, ti_work);
a9f3a74a TG	181
a9f3a74a TG	182	if (ti_work & _TIF_NOTIFY_RESUME) {
a9f3a74a TG	183	tracehook_notify_resume(regs);
	184	rseq_handle_notify_resume(NULL, regs);
	185	}
	186
	187	/* Architecture specific TIF work */
	188	arch_exit_to_user_mode_work(regs, ti_work);
	189
	190	/*
	191	* Disable interrupts and reevaluate the work flags as they
	192	* might have changed while interrupts and preemption was
	193	* enabled above.
	194	*/
	195	local_irq_disable_exit_to_user();
	196	ti_work = READ_ONCE(current_thread_info()->flags);
	197	}
	198
	199	/* Return the latest work state for arch_exit_to_user_mode() */
	200	return ti_work;
	201	}
	202
	203	static void exit_to_user_mode_prepare(struct pt_regs *regs)
	204	{
	205	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
	206
	207	lockdep_assert_irqs_disabled();
	208
	209	if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
	210	ti_work = exit_to_user_mode_loop(regs, ti_work);
	211
	212	arch_exit_to_user_mode_prepare(regs, ti_work);
	213
	214	/* Ensure that the address limit is intact and no locks are held */
	215	addr_limit_user_check();
	216	lockdep_assert_irqs_disabled();
	217	lockdep_sys_exit();
	218	}
	219
	220	#ifndef _TIF_SINGLESTEP
64eb35f7	221	static inline bool report_single_step(unsigned long work)
a9f3a74a TG	222	{
	223	return false;
	224	}
	225	#else
	226	/*
64eb35f7	227	* If SYSCALL_EMU is set, then the only reason to report is when
a9f3a74a	228	* TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
900ffe39	229	* instruction has been already reported in syscall_enter_from_user_mode().
a9f3a74a	230	*/
64eb35f7	231	static inline bool report_single_step(unsigned long work)
a9f3a74a	232	{
64eb35f7 GKB	233	if (!(work & SYSCALL_WORK_SYSCALL_EMU))
	234	return false;
	235
	236	return !!(current_thread_info()->flags & _TIF_SINGLESTEP);
a9f3a74a TG	237	}
	238	#endif
	239
29915524 GKB	240
29915524 GKB	241	static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
a9f3a74a TG	242	{
	243	bool step;
	244
11894468 GKB	245	/*
	246	* If the syscall was rolled back due to syscall user dispatching,
	247	* then the tracers below are not invoked for the same reason as
	248	* the entry side was not invoked in syscall_trace_enter(): The ABI
	249	* of these syscalls is unknown.
	250	*/
	251	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
	252	if (unlikely(current->syscall_dispatch.on_dispatch)) {
	253	current->syscall_dispatch.on_dispatch = false;
	254	return;
	255	}
	256	}
	257
a9f3a74a TG	258	audit_syscall_exit(regs);
a9f3a74a TG	259
524666cb	260	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
a9f3a74a TG	261	trace_sys_exit(regs, syscall_get_return_value(current, regs));
a9f3a74a TG	262
64eb35f7	263	step = report_single_step(work);
64c19ba2	264	if (step \|\| work & SYSCALL_WORK_SYSCALL_TRACE)
a9f3a74a TG	265	arch_syscall_exit_tracehook(regs, step);
	266	}
	267
	268	/*
	269	* Syscall specific exit to user mode preparation. Runs with interrupts
	270	* enabled.
	271	*/
	272	static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
	273	{
b86678cf	274	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
a9f3a74a TG	275	unsigned long nr = syscall_get_nr(current, regs);
	276
	277	CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
	278
	279	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
	280	if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
	281	local_irq_enable();
	282	}
	283
	284	rseq_syscall(regs);
	285
	286	/*
	287	* Do one-time syscall specific work. If these work items are
	288	* enabled, we want to run them exactly once per syscall exit with
	289	* interrupts enabled.
	290	*/
29915524 GKB	291	if (unlikely(work & SYSCALL_WORK_EXIT))
29915524 GKB	292	syscall_exit_work(regs, work);
a9f3a74a TG	293	}
	294
	295	__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
	296	{
	297	instrumentation_begin();
	298	syscall_exit_to_user_mode_prepare(regs);
	299	local_irq_disable_exit_to_user();
	300	exit_to_user_mode_prepare(regs);
	301	instrumentation_end();
bb793562	302	__exit_to_user_mode();
a9f3a74a TG	303	}
a9f3a74a TG	304
142781e1 TG	305	noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
142781e1 TG	306	{
6666bb71	307	__enter_from_user_mode(regs);
142781e1	308	}
a9f3a74a TG	309
	310	noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
	311	{
	312	instrumentation_begin();
	313	exit_to_user_mode_prepare(regs);
	314	instrumentation_end();
bb793562	315	__exit_to_user_mode();
a9f3a74a	316	}
a5497bab	317
aadfc2f9	318	noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
a5497bab TG	319	{
	320	irqentry_state_t ret = {
	321	.exit_rcu = false,
	322	};
	323
	324	if (user_mode(regs)) {
	325	irqentry_enter_from_user_mode(regs);
	326	return ret;
	327	}
	328
	329	/*
	330	* If this entry hit the idle task invoke rcu_irq_enter() whether
	331	* RCU is watching or not.
	332	*
78a56e04	333	* Interrupts can nest when the first interrupt invokes softirq
a5497bab TG	334	* processing on return which enables interrupts.
	335	*
	336	* Scheduler ticks in the idle task can mark quiescent state and
	337	* terminate a grace period, if and only if the timer interrupt is
	338	* not nested into another interrupt.
	339	*
7f2a53c2	340	* Checking for rcu_is_watching() here would prevent the nesting
a5497bab TG	341	* interrupt to invoke rcu_irq_enter(). If that nested interrupt is
	342	* the tick then rcu_flavor_sched_clock_irq() would wrongfully
	343	* assume that it is the first interupt and eventually claim
78a56e04	344	* quiescent state and end grace periods prematurely.
a5497bab TG	345	*
	346	* Unconditionally invoke rcu_irq_enter() so RCU state stays
	347	* consistent.
	348	*
	349	* TINY_RCU does not support EQS, so let the compiler eliminate
	350	* this part when enabled.
	351	*/
	352	if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
	353	/*
	354	* If RCU is not watching then the same careful
	355	* sequence vs. lockdep and tracing is required
45ff5105	356	* as in irqentry_enter_from_user_mode().
a5497bab TG	357	*/
	358	lockdep_hardirqs_off(CALLER_ADDR0);
	359	rcu_irq_enter();
	360	instrumentation_begin();
	361	trace_hardirqs_off_finish();
	362	instrumentation_end();
	363
	364	ret.exit_rcu = true;
	365	return ret;
	366	}
	367
	368	/*
	369	* If RCU is watching then RCU only wants to check whether it needs
	370	* to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
	371	* already contains a warning when RCU is not watching, so no point
	372	* in having another one here.
	373	*/
9d820f68	374	lockdep_hardirqs_off(CALLER_ADDR0);
a5497bab TG	375	instrumentation_begin();
a5497bab TG	376	rcu_irq_enter_check_tick();
9d820f68	377	trace_hardirqs_off_finish();
a5497bab TG	378	instrumentation_end();
	379
	380	return ret;
	381	}
	382
	383	void irqentry_exit_cond_resched(void)
	384	{
	385	if (!preempt_count()) {
	386	/* Sanity check RCU and thread stack */
	387	rcu_irq_exit_check_preempt();
	388	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
	389	WARN_ON_ONCE(!on_thread_stack());
	390	if (need_resched())
	391	preempt_schedule_irq();
	392	}
	393	}
	394
aadfc2f9	395	noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
a5497bab TG	396	{
	397	lockdep_assert_irqs_disabled();
	398
	399	/* Check whether this returns to user mode */
	400	if (user_mode(regs)) {
	401	irqentry_exit_to_user_mode(regs);
	402	} else if (!regs_irqs_disabled(regs)) {
	403	/*
	404	* If RCU was not watching on entry this needs to be done
	405	* carefully and needs the same ordering of lockdep/tracing
	406	* and RCU as the return to user mode path.
	407	*/
	408	if (state.exit_rcu) {
	409	instrumentation_begin();
	410	/* Tell the tracer that IRET will enable interrupts */
	411	trace_hardirqs_on_prepare();
	412	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	413	instrumentation_end();
	414	rcu_irq_exit();
	415	lockdep_hardirqs_on(CALLER_ADDR0);
	416	return;
	417	}
	418
	419	instrumentation_begin();
	420	if (IS_ENABLED(CONFIG_PREEMPTION))
	421	irqentry_exit_cond_resched();
	422	/* Covers both tracing and lockdep */
	423	trace_hardirqs_on();
	424	instrumentation_end();
	425	} else {
	426	/*
	427	* IRQ flags state is correct already. Just tell RCU if it
	428	* was not watching on entry.
	429	*/
	430	if (state.exit_rcu)
	431	rcu_irq_exit();
	432	}
	433	}
b6be002b TG	434
	435	irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
	436	{
	437	irqentry_state_t irq_state;
	438
	439	irq_state.lockdep = lockdep_hardirqs_enabled();
	440
	441	__nmi_enter();
	442	lockdep_hardirqs_off(CALLER_ADDR0);
	443	lockdep_hardirq_enter();
	444	rcu_nmi_enter();
	445
	446	instrumentation_begin();
	447	trace_hardirqs_off_finish();
	448	ftrace_nmi_enter();
	449	instrumentation_end();
	450
	451	return irq_state;
	452	}
	453
	454	void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
	455	{
	456	instrumentation_begin();
	457	ftrace_nmi_exit();
	458	if (irq_state.lockdep) {
	459	trace_hardirqs_on_prepare();
	460	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
	461	}
	462	instrumentation_end();
	463
	464	rcu_nmi_exit();
	465	lockdep_hardirq_exit();
	466	if (irq_state.lockdep)
	467	lockdep_hardirqs_on(CALLER_ADDR0);
	468	__nmi_exit();
	469	}