path: root/arch/um/kernel/time.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
 * Copyright (C) 2012-2014 Cisco Systems
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Copyright (C) 2019 Intel Corporation
 */

#include <linux/clockchips.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/threads.h>
#include <asm/irq.h>
#include <asm/param.h>
#include <kern_util.h>
#include <os.h>
#include <linux/time-internal.h>
#include <shared/init.h>

#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
enum time_travel_mode time_travel_mode;

static bool time_travel_start_set;
static unsigned long long time_travel_start;
static unsigned long long time_travel_time;
static LIST_HEAD(time_travel_events);
static unsigned long long time_travel_timer_interval;
static unsigned long long time_travel_next_event;
static struct time_travel_event time_travel_timer_event;

static void time_travel_set_time(unsigned long long ns)
{
	if (unlikely(ns < time_travel_time))
		panic("time-travel: time goes backwards %lld -> %lld\n",
		      time_travel_time, ns);
	time_travel_time = ns;
}

static struct time_travel_event *time_travel_first_event(void)
{
	return list_first_entry_or_null(&time_travel_events,
					struct time_travel_event,
					list);
}

static void __time_travel_add_event(struct time_travel_event *e,
				    unsigned long long time)
{
	struct time_travel_event *tmp;
	bool inserted = false;

	if (WARN(time_travel_mode == TT_MODE_BASIC &&
		 e != &time_travel_timer_event,
		 "only timer events can be handled in basic mode"))
		return;

	if (e->pending)
		return;

	e->pending = true;
	e->time = time;

	list_for_each_entry(tmp, &time_travel_events, list) {
		/*
		 * Add the new entry before one with higher time,
		 * or if they're equal and both on stack, because
		 * in that case we need to unwind the stack in the
		 * right order, and the later event (timer sleep
		 * or such) must be dequeued first.
		 */
		if ((tmp->time > e->time) ||
		    (tmp->time == e->time && tmp->onstack && e->onstack)) {
			list_add_tail(&e->list, &tmp->list);
			inserted = true;
			break;
		}
	}

	if (!inserted)
		list_add_tail(&e->list, &time_travel_events);

	tmp = time_travel_first_event();
	time_travel_next_event = tmp->time;
}

static void time_travel_add_event(struct time_travel_event *e,
				  unsigned long long time)
{
	if (WARN_ON(!e->fn))
		return;

	__time_travel_add_event(e, time);
}

void time_travel_periodic_timer(struct time_travel_event *e)
{
	time_travel_add_event(&time_travel_timer_event,
			      time_travel_time + time_travel_timer_interval);
	deliver_alarm();
}

static void time_travel_deliver_event(struct time_travel_event *e)
{
	/* this is basically just deliver_alarm(), handles IRQs itself */
	e->fn(e);
}

static bool time_travel_del_event(struct time_travel_event *e)
{
	if (!e->pending)
		return false;
	list_del(&e->list);
	e->pending = false;
	return true;
}

static void time_travel_update_time(unsigned long long next, bool retearly)
{
	struct time_travel_event ne = {
		.onstack = true,
	};
	struct time_travel_event *e;
	bool finished = retearly;

	/* add it without a handler - we deal with that specifically below */
	__time_travel_add_event(&ne, next);

	do {
		e = time_travel_first_event();

		BUG_ON(!e);
		time_travel_set_time(e->time);

		/* new events may have been inserted while we were waiting */
		if (e == time_travel_first_event()) {
			BUG_ON(!time_travel_del_event(e));
			BUG_ON(time_travel_time != e->time);

			if (e == &ne) {
				finished = true;
			} else {
				if (e->onstack)
					panic("On-stack event dequeued outside of the stack! time=%lld, event time=%lld, event=%pS\n",
					      time_travel_time, e->time, e);
				time_travel_deliver_event(e);
			}
		}
	} while (!finished);

	time_travel_del_event(&ne);
}

static void time_travel_oneshot_timer(struct time_travel_event *e)
{
	deliver_alarm();
}

void time_travel_sleep(unsigned long long duration)
{
	unsigned long long next = time_travel_time + duration;

	if (time_travel_mode == TT_MODE_BASIC)
		os_timer_disable();

	time_travel_update_time(next, true);

	if (time_travel_mode == TT_MODE_BASIC &&
	    time_travel_timer_event.pending) {
		if (time_travel_timer_event.fn == time_travel_periodic_timer) {
			/*
			 * This is somewhat wrong - we should get the first
			 * one sooner like the os_timer_one_shot() below...
			 */
			os_timer_set_interval(time_travel_timer_interval);
		} else {
			os_timer_one_shot(time_travel_timer_event.time - next);
		}
	}
}

static void time_travel_handle_real_alarm(void)
{
	time_travel_set_time(time_travel_next_event);

	time_travel_del_event(&time_travel_timer_event);

	if (time_travel_timer_event.fn == time_travel_periodic_timer)
		time_travel_add_event(&time_travel_timer_event,
				      time_travel_time +
				      time_travel_timer_interval);
}

static void time_travel_set_interval(unsigned long long interval)
{
	time_travel_timer_interval = interval;
}
#else /* CONFIG_UML_TIME_TRAVEL_SUPPORT */
#define time_travel_start_set 0
#define time_travel_start 0
#define time_travel_time 0

static inline void time_travel_update_time(unsigned long long ns, bool retearly)
{
}

static inline void time_travel_handle_real_alarm(void)
{
}

static void time_travel_set_interval(unsigned long long interval)
{
}

/* these are empty macros so the struct/fn need not exist */
#define time_travel_add_event(e, time) do { } while (0)
#define time_travel_del_event(e) do { } while (0)
#endif

void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
{
	unsigned long flags;

	/*
	 * In basic time-travel mode we still get real interrupts
	 * (signals) but since we don't read time from the OS, we
	 * must update the simulated time here to the expiry when
	 * we get a signal.
	 * This is not the case in inf-cpu mode, since there we
	 * never get any real signals from the OS.
	 */
	if (time_travel_mode == TT_MODE_BASIC)
		time_travel_handle_real_alarm();

	local_irq_save(flags);
	do_IRQ(TIMER_IRQ, regs);
	local_irq_restore(flags);
}

static int itimer_shutdown(struct clock_event_device *evt)
{
	if (time_travel_mode != TT_MODE_OFF)
		time_travel_del_event(&time_travel_timer_event);

	if (time_travel_mode != TT_MODE_INFCPU)
		os_timer_disable();

	return 0;
}

static int itimer_set_periodic(struct clock_event_device *evt)
{
	unsigned long long interval = NSEC_PER_SEC / HZ;

	if (time_travel_mode != TT_MODE_OFF) {
		time_travel_del_event(&time_travel_timer_event);
		time_travel_set_event_fn(&time_travel_timer_event,
					 time_travel_periodic_timer);
		time_travel_set_interval(interval);
		time_travel_add_event(&time_travel_timer_event,
				      time_travel_time + interval);
	}

	if (time_travel_mode != TT_MODE_INFCPU)
		os_timer_set_interval(interval);

	return 0;
}

static int itimer_next_event(unsigned long delta,
			     struct clock_event_device *evt)
{
	delta += 1;

	if (time_travel_mode != TT_MODE_OFF) {
		time_travel_del_event(&time_travel_timer_event);
		time_travel_set_event_fn(&time_travel_timer_event,
					 time_travel_oneshot_timer);
		time_travel_add_event(&time_travel_timer_event,
				      time_travel_time + delta);
	}

	if (time_travel_mode != TT_MODE_INFCPU)
		return os_timer_one_shot(delta);

	return 0;
}

static int itimer_one_shot(struct clock_event_device *evt)
{
	return itimer_next_event(0, evt);
}

static struct clock_event_device timer_clockevent = {
	.name			= "posix-timer",
	.rating			= 250,
	.cpumask		= cpu_possible_mask,
	.features		= CLOCK_EVT_FEAT_PERIODIC |
				  CLOCK_EVT_FEAT_ONESHOT,
	.set_state_shutdown	= itimer_shutdown,
	.set_state_periodic	= itimer_set_periodic,
	.set_