diff options
Diffstat (limited to 'arch/um/kernel/time.c')
| -rw-r--r-- | arch/um/kernel/time.c | 764 |
1 files changed, 764 insertions, 0 deletions
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c new file mode 100644 index 000000000..8dafc3f2a --- /dev/null +++ b/arch/um/kernel/time.c @@ -0,0 +1,764 @@ +// 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 <linux/um_timetravel.h> +#include <shared/init.h> + +#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT +enum time_travel_mode time_travel_mode; +EXPORT_SYMBOL_GPL(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 int time_travel_ext_fd = -1; +static unsigned int time_travel_ext_waiting; +static bool time_travel_ext_prev_request_valid; +static unsigned long long time_travel_ext_prev_request; +static bool time_travel_ext_free_until_valid; +static unsigned long long time_travel_ext_free_until; + +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; +} + +enum time_travel_message_handling { + TTMH_IDLE, + TTMH_POLL, + TTMH_READ, +}; + +static void time_travel_handle_message(struct um_timetravel_msg *msg, + enum time_travel_message_handling mode) +{ + struct um_timetravel_msg resp = { + .op = UM_TIMETRAVEL_ACK, + }; + int ret; + + /* + * Poll outside the locked section (if we're not called to only read + * the response) so we can get interrupts for e.g. virtio while we're + * here, but then we need to lock to not get interrupted between the + * read of the message and write of the ACK. + */ + if (mode != TTMH_READ) { + bool disabled = irqs_disabled(); + + BUG_ON(mode == TTMH_IDLE && !disabled); + + if (disabled) + local_irq_enable(); + while (os_poll(1, &time_travel_ext_fd) != 0) { + /* nothing */ + } + if (disabled) + local_irq_disable(); + } + + ret = os_read_file(time_travel_ext_fd, msg, sizeof(*msg)); + + if (ret == 0) + panic("time-travel external link is broken\n"); + if (ret != sizeof(*msg)) + panic("invalid time-travel message - %d bytes\n", ret); + + switch (msg->op) { + default: + WARN_ONCE(1, "time-travel: unexpected message %lld\n", + (unsigned long long)msg->op); + break; + case UM_TIMETRAVEL_ACK: + return; + case UM_TIMETRAVEL_RUN: + time_travel_set_time(msg->time); + break; + case UM_TIMETRAVEL_FREE_UNTIL: + time_travel_ext_free_until_valid = true; + time_travel_ext_free_until = msg->time; + break; + } + + resp.seq = msg->seq; + os_write_file(time_travel_ext_fd, &resp, sizeof(resp)); +} + +static u64 time_travel_ext_req(u32 op, u64 time) +{ + static int seq; + int mseq = ++seq; + struct um_timetravel_msg msg = { + .op = op, + .time = time, + .seq = mseq, + }; + unsigned long flags; + + /* + * We need to save interrupts here and only restore when we + * got the ACK - otherwise we can get interrupted and send + * another request while we're still waiting for an ACK, but + * the peer doesn't know we got interrupted and will send + * the ACKs in the same order as the message, but we'd need + * to see them in the opposite order ... + * + * This wouldn't matter *too* much, but some ACKs carry the + * current time (for UM_TIMETRAVEL_GET) and getting another + * ACK without a time would confuse us a lot! + * + * The sequence number assignment that happens here lets us + * debug such message handling issues more easily. + */ + local_irq_save(flags); + os_write_file(time_travel_ext_fd, &msg, sizeof(msg)); + + while (msg.op != UM_TIMETRAVEL_ACK) + time_travel_handle_message(&msg, TTMH_READ); + + if (msg.seq != mseq) + panic("time-travel: ACK message has different seqno! op=%d, seq=%d != %d time=%lld\n", + msg.op, msg.seq, mseq, msg.time); + + if (op == UM_TIMETRAVEL_GET) + time_travel_set_time(msg.time); + local_irq_restore(flags); + + return msg.time; +} + +void __time_travel_wait_readable(int fd) +{ + int fds[2] = { fd, time_travel_ext_fd }; + int ret; + + if (time_travel_mode != TT_MODE_EXTERNAL) + return; + + while ((ret = os_poll(2, fds))) { + struct um_timetravel_msg msg; + + if (ret == 1) + time_travel_handle_message(&msg, TTMH_READ); + } +} +EXPORT_SYMBOL_GPL(__time_travel_wait_readable); + +static void time_travel_ext_update_request(unsigned long long time) +{ + if (time_travel_mode != TT_MODE_EXTERNAL) + return; + + /* asked for exactly this time previously */ + if (time_travel_ext_prev_request_valid && + time == time_travel_ext_prev_request) + return; + + time_travel_ext_prev_request = time; + time_travel_ext_prev_request_valid = true; + time_travel_ext_req(UM_TIMETRAVEL_REQUEST, time); +} + +void __time_travel_propagate_time(void) +{ + time_travel_ext_req(UM_TIMETRAVEL_UPDATE, time_travel_time); +} +EXPORT_SYMBOL_GPL(__time_travel_propagate_time); + +/* returns true if we must do a wait to the simtime device */ +static bool time_travel_ext_request(unsigned long long time) +{ + /* + * If we received an external sync point ("free until") then we + * don't have to request/wait for anything until then, unless + * we're already waiting. + */ + if (!time_travel_ext_waiting && time_travel_ext_free_until_valid && + time < time_travel_ext_free_until) + return false; + + time_travel_ext_update_request(time); + return true; +} + +static void time_travel_ext_wait(bool idle) +{ + struct um_timetravel_msg msg = { + .op = UM_TIMETRAVEL_ACK, + }; + + time_travel_ext_prev_request_valid = false; + time_travel_ext_waiting++; + + time_travel_ext_req(UM_TIMETRAVEL_WAIT, -1); + + /* + * Here we are deep in the idle loop, so we have to break out of the + * kernel abstraction in a sense and implement this in terms of the + * UML system waiting on the VQ interrupt while sleeping, when we get + * the signal it'll call time_travel_ext_vq_notify_done() completing the + * call. + */ + while (msg.op != UM_TIMETRAVEL_RUN) + time_travel_handle_message(&msg, idle ? TTMH_IDLE : TTMH_POLL); + + time_travel_ext_waiting--; + + /* we might request more stuff while polling - reset when we run */ + time_travel_ext_prev_request_valid = false; +} + +static void time_travel_ext_get_time(void) +{ + time_travel_ext_req(UM_TIMETRAVEL_GET, -1); +} + +static void __time_travel_update_time(unsigned long long ns, bool idle) +{ + if (time_travel_mode == TT_MODE_EXTERNAL && time_travel_ext_request(ns)) + time_travel_ext_wait(idle); + else + time_travel_set_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 (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_ext_update_request(tmp->time); + 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) +{ + if (e == &time_travel_timer_event) { + /* + * deliver_alarm() does the irq_enter/irq_exit + * by itself, so must handle it specially here + */ + e->fn(e); + } else { + unsigned long flags; + + local_irq_save(flags); + irq_enter(); + e->fn(e); + irq_exit(); + local_irq_restore(flags); + } +} + +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 idle) +{ + struct time_travel_event ne = { + .onstack = true, + }; + struct time_travel_event *e; + bool finished = idle; + + /* 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_update_time(e->time, idle); + + /* 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); + } + } + + e = time_travel_first_event(); + if (e) + time_travel_ext_update_request(e->time); + } while (ne.pending && !finished); + + time_travel_del_event(&ne); +} + +void time_travel_ndelay(unsigned long nsec) +{ + time_travel_update_time(time_travel_time + nsec, false); +} +EXPORT_SYMBOL(time_travel_ndelay); + +void time_travel_add_irq_event(struct time_travel_event *e) +{ + BUG_ON(time_travel_mode != TT_MODE_EXTERNAL); + + time_travel_ext_get_time(); + /* + * We could model interrupt latency here, for now just + * don't have any latency at all and request the exact + * same time (again) to run the interrupt... + */ + time_travel_add_event(e, time_travel_time); +} +EXPORT_SYMBOL_GPL(time_travel_add_irq_event); + +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; +} + +static int time_travel_connect_external(const char *socket) +{ + const char *sep; + unsigned long long id = (unsigned long long)-1; + int rc; + + if ((sep = strchr(socket, ':'))) { + char buf[25] = {}; + if (sep - socket > sizeof(buf) - 1) + goto invalid_number; + + memcpy(buf, socket, sep - socket); + if (kstrtoull(buf, 0, &id)) { +invalid_number: + panic("time-travel: invalid external ID in string '%s'\n", + socket); + return -EINVAL; + } + + socket = sep + 1; + } + + rc = os_connect_socket(socket); + if (rc < 0) { + panic("time-travel: failed to connect to external socket %s\n", + socket); + return rc; + } + + time_travel_ext_fd = rc; + + time_travel_ext_req(UM_TIMETRAVEL_START, id); + + return 1; +} +#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) +{ +} + +/* fail link if this actually gets used */ +extern u64 time_travel_ext_req(u32 op, u64 time); + +/* 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 && + time_travel_mode != TT_MODE_EXTERNAL) + 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 && + time_travel_mode != TT_MODE_EXTERNAL) + 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 && + time_travel_mode != TT_MODE_EXTERNAL) + 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_state_oneshot = itimer_one_shot, + .set_next_event = itimer_next_event, + .shift = 0, + .max_delta_ns = 0xffffffff, + .max_delta_ticks = 0xffffffff, + .min_delta_ns = TIMER_MIN_DELTA, + .min_delta_ticks = TIMER_MIN_DELTA, // microsecond resolution should be enough for anyone, same as 640K RAM + .irq = 0, + .mult = 1, +}; + +static irqreturn_t um_timer(int irq, void *dev) +{ + if (get_current()->mm != NULL) + { + /* userspace - relay signal, results in correct userspace timers */ + os_alarm_process(get_current()->mm->context.id.u.pid); + } + + (*timer_clockevent.event_handler)(&timer_clockevent); + + return IRQ_HANDLED; +} + +static u64 timer_read(struct clocksource *cs) +{ + if (time_travel_mode != TT_MODE_OFF) { + /* + * We make reading the timer cost a bit so that we don't get + * stuck in loops that expect time to move more than the + * exact requested sleep amount, e.g. python's socket server, + * see https://bugs.python.org/issue37026. + * + * However, don't do that when we're in interrupt or such as + * then we might recurse into our own processing, and get to + * even more waiting, and that's not good - it messes up the + * "what do I do next" and onstack event we use to know when + * to return from time_travel_update_time(). + */ + if (!irqs_disabled() && !in_interrupt() && !in_softirq()) + time_travel_update_time(time_travel_time + + TIMER_MULTIPLIER, + false); + return time_travel_time / TIMER_MULTIPLIER; + } + + return os_nsecs() / TIMER_MULTIPLIER; +} + +static struct clocksource timer_clocksource = { + .name = "timer", + .rating = 300, + .read = timer_read, + .mask = CLOCKSOURCE_MASK(64), + .flags = CLOCK_SOURCE_IS_CONTINUOUS, +}; + +static void __init um_timer_setup(void) +{ + int err; + + err = request_irq(TIMER_IRQ, um_timer, IRQF_TIMER, "hr timer", NULL); + if (err != 0) + printk(KERN_ERR "register_timer : request_irq failed - " + "errno = %d\n", -err); + + err = os_timer_create(); + if (err != 0) { + printk(KERN_ERR "creation of timer failed - errno = %d\n", -err); + return; + } + + err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER); + if (err) { + printk(KERN_ERR "clocksource_register_hz returned %d\n", err); + return; + } + clockevents_register_device(&timer_clockevent); +} + +void read_persistent_clock64(struct timespec64 *ts) +{ + long long nsecs; + + if (time_travel_start_set) + nsecs = time_travel_start + time_travel_time; + else if (time_travel_mode == TT_MODE_EXTERNAL) + nsecs = time_travel_ext_req(UM_TIMETRAVEL_GET_TOD, -1); + else + nsecs = os_persistent_clock_emulation(); + + set_normalized_timespec64(ts, nsecs / NSEC_PER_SEC, + nsecs % NSEC_PER_SEC); +} + +void __init time_init(void) +{ + timer_set_signal_handler(); + late_time_init = um_timer_setup; +} + +#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT +unsigned long calibrate_delay_is_known(void) +{ + if (time_travel_mode == TT_MODE_INFCPU || + time_travel_mode == TT_MODE_EXTERNAL) + return 1; + return 0; +} + +int setup_time_travel(char *str) +{ + if (strcmp(str, "=inf-cpu") == 0) { + time_travel_mode = TT_MODE_INFCPU; + timer_clockevent.name = "time-travel-timer-infcpu"; + timer_clocksource.name = "time-travel-clock"; + return 1; + } + + if (strncmp(str, "=ext:", 5) == 0) { + time_travel_mode = TT_MODE_EXTERNAL; + timer_clockevent.name = "time-travel-timer-external"; + timer_clocksource.name = "time-travel-clock-external"; + return time_travel_connect_external(str + 5); + } + + if (!*str) { + time_travel_mode = TT_MODE_BASIC; + timer_clockevent.name = "time-travel-timer"; + timer_clocksource.name = "time-travel-clock"; + return 1; + } + + return -EINVAL; +} + +__setup("time-travel", setup_time_travel); +__uml_help(setup_time_travel, +"time-travel\n" +"This option just enables basic time travel mode, in which the clock/timers\n" +"inside the UML instance skip forward when there's nothing to do, rather than\n" +"waiting for real time to elapse. However, instance CPU speed is limited by\n" +"the real CPU speed, so e.g. a 10ms timer will always fire after ~10ms wall\n" +"clock (but quicker when there's nothing to do).\n" +"\n" +"time-travel=inf-cpu\n" +"This enables time travel mode with infinite processing power, in which there\n" +"are no wall clock timers, and any CPU processing happens - as seen from the\n" +"guest - instantly. This can be useful for accurate simulation regardless of\n" +"debug overhead, physical CPU speed, etc. but is somewhat dangerous as it can\n" +"easily lead to getting stuck (e.g. if anything in the system busy loops).\n" +"\n" +"time-travel=ext:[ID:]/path/to/socket\n" +"This enables time travel mode similar to =inf-cpu, except the system will\n" +"use the given socket to coordinate with a central scheduler, in order to\n" +"have more than one system simultaneously be on simulated time. The virtio\n" +"driver code in UML knows about this so you can also simulate networks and\n" +"devices using it, assuming the device has the right capabilities.\n" +"The optional ID is a 64-bit integer that's sent to the central scheduler.\n"); + +int setup_time_travel_start(char *str) +{ + int err; + + err = kstrtoull(str, 0, &time_travel_start); + if (err) + return err; + + time_travel_start_set = 1; + return 1; +} + +__setup("time-travel-start", setup_time_travel_start); +__uml_help(setup_time_travel_start, +"time-travel-start=<seconds>\n" +"Configure the UML instance's wall clock to start at this value rather than\n" +"the host's wall clock at the time of UML boot.\n"); +#endif |