arch/um/kernel/time.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
   4  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
   5  * Copyright (C) 2012-2014 Cisco Systems
   6  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   7  */
   8
   9 #include <linux/clockchips.h>
  10 #include <linux/init.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/jiffies.h>
  13 #include <linux/mm.h>
  14 #include <linux/sched.h>
  15 #include <linux/spinlock.h>
  16 #include <linux/threads.h>
  17 #include <asm/irq.h>
  18 #include <asm/param.h>
  19 #include <kern_util.h>
  20 #include <os.h>
  21 #include <timer-internal.h>
  22 #include <shared/init.h>
  23
  24 #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
  25 enum time_travel_mode time_travel_mode;
  26 unsigned long long time_travel_time;
  27 enum time_travel_timer_mode time_travel_timer_mode;
  28 unsigned long long time_travel_timer_expiry;
  29 unsigned long long time_travel_timer_interval;
  30
  31 static bool time_travel_start_set;
  32 static unsigned long long time_travel_start;
  33 #else
  34 #define time_travel_start_set 0
  35 #define time_travel_start 0
  36 #endif
  37
  38 void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
  39 {
  40         unsigned long flags;
  41
  42         /*
  43          * In basic time-travel mode we still get real interrupts
  44          * (signals) but since we don't read time from the OS, we
  45          * must update the simulated time here to the expiry when
  46          * we get a signal.
  47          * This is not the case in inf-cpu mode, since there we
  48          * never get any real signals from the OS.
  49          */
  50         if (time_travel_mode == TT_MODE_BASIC)
  51                 time_travel_set_time(time_travel_timer_expiry);
  52
  53         local_irq_save(flags);
  54         do_IRQ(TIMER_IRQ, regs);
  55         local_irq_restore(flags);
  56 }
  57
  58 static int itimer_shutdown(struct clock_event_device *evt)
  59 {
  60         if (time_travel_mode != TT_MODE_OFF)
  61                 time_travel_set_timer_mode(TT_TMR_DISABLED);
  62
  63         if (time_travel_mode != TT_MODE_INFCPU)
  64                 os_timer_disable();
  65
  66         return 0;
  67 }
  68
  69 static int itimer_set_periodic(struct clock_event_device *evt)
  70 {
  71         unsigned long long interval = NSEC_PER_SEC / HZ;
  72
  73         if (time_travel_mode != TT_MODE_OFF) {
  74                 time_travel_set_timer_mode(TT_TMR_PERIODIC);
  75                 time_travel_set_timer_expiry(time_travel_time + interval);
  76                 time_travel_set_timer_interval(interval);
  77         }
  78
  79         if (time_travel_mode != TT_MODE_INFCPU)
  80                 os_timer_set_interval(interval);
  81
  82         return 0;
  83 }
  84
  85 static int itimer_next_event(unsigned long delta,
  86                              struct clock_event_device *evt)
  87 {
  88         delta += 1;
  89
  90         if (time_travel_mode != TT_MODE_OFF) {
  91                 time_travel_set_timer_mode(TT_TMR_ONESHOT);
  92                 time_travel_set_timer_expiry(time_travel_time + delta);
  93         }
  94
  95         if (time_travel_mode != TT_MODE_INFCPU)
  96                 return os_timer_one_shot(delta);
  97
  98         return 0;
  99 }
 100
 101 static int itimer_one_shot(struct clock_event_device *evt)
 102 {
 103         return itimer_next_event(0, evt);
 104 }
 105
 106 static struct clock_event_device timer_clockevent = {
 107         .name                   = "posix-timer",
 108         .rating                 = 250,
 109         .cpumask                = cpu_possible_mask,
 110         .features               = CLOCK_EVT_FEAT_PERIODIC |
 111                                   CLOCK_EVT_FEAT_ONESHOT,
 112         .set_state_shutdown     = itimer_shutdown,
 113         .set_state_periodic     = itimer_set_periodic,
 114         .set_state_oneshot      = itimer_one_shot,
 115         .set_next_event         = itimer_next_event,
 116         .shift                  = 0,
 117         .max_delta_ns           = 0xffffffff,
 118         .max_delta_ticks        = 0xffffffff,
 119         .min_delta_ns           = TIMER_MIN_DELTA,
 120         .min_delta_ticks        = TIMER_MIN_DELTA, // microsecond resolution should be enough for anyone, same as 640K RAM
 121         .irq                    = 0,
 122         .mult                   = 1,
 123 };
 124
 125 static irqreturn_t um_timer(int irq, void *dev)
 126 {
 127         if (get_current()->mm != NULL)
 128         {
 129         /* userspace - relay signal, results in correct userspace timers */
 130                 os_alarm_process(get_current()->mm->context.id.u.pid);
 131         }
 132
 133         (*timer_clockevent.event_handler)(&timer_clockevent);
 134
 135         return IRQ_HANDLED;
 136 }
 137
 138 static u64 timer_read(struct clocksource *cs)
 139 {
 140         if (time_travel_mode != TT_MODE_OFF) {
 141                 /*
 142                  * We make reading the timer cost a bit so that we don't get
 143                  * stuck in loops that expect time to move more than the
 144                  * exact requested sleep amount, e.g. python's socket server,
 145                  * see https://bugs.python.org/issue37026.
 146                  */
 147                 time_travel_set_time(time_travel_time + TIMER_MULTIPLIER);
 148                 return time_travel_time / TIMER_MULTIPLIER;
 149         }
 150
 151         return os_nsecs() / TIMER_MULTIPLIER;
 152 }
 153
 154 static struct clocksource timer_clocksource = {
 155         .name           = "timer",
 156         .rating         = 300,
 157         .read           = timer_read,
 158         .mask           = CLOCKSOURCE_MASK(64),
 159         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 160 };
 161
 162 static void __init um_timer_setup(void)
 163 {
 164         int err;
 165
 166         err = request_irq(TIMER_IRQ, um_timer, IRQF_TIMER, "hr timer", NULL);
 167         if (err != 0)
 168                 printk(KERN_ERR "register_timer : request_irq failed - "
 169                        "errno = %d\n", -err);
 170
 171         err = os_timer_create();
 172         if (err != 0) {
 173                 printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
 174                 return;
 175         }
 176
 177         err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
 178         if (err) {
 179                 printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
 180                 return;
 181         }
 182         clockevents_register_device(&timer_clockevent);
 183 }
 184
 185 void read_persistent_clock64(struct timespec64 *ts)
 186 {
 187         long long nsecs;
 188
 189         if (time_travel_start_set)
 190                 nsecs = time_travel_start + time_travel_time;
 191         else
 192                 nsecs = os_persistent_clock_emulation();
 193
 194         set_normalized_timespec64(ts, nsecs / NSEC_PER_SEC,
 195                                   nsecs % NSEC_PER_SEC);
 196 }
 197
 198 void __init time_init(void)
 199 {
 200         timer_set_signal_handler();
 201         late_time_init = um_timer_setup;
 202 }
 203
 204 #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
 205 unsigned long calibrate_delay_is_known(void)
 206 {
 207         if (time_travel_mode == TT_MODE_INFCPU)
 208                 return 1;
 209         return 0;
 210 }
 211
 212 int setup_time_travel(char *str)
 213 {
 214         if (strcmp(str, "=inf-cpu") == 0) {
 215                 time_travel_mode = TT_MODE_INFCPU;
 216                 timer_clockevent.name = "time-travel-timer-infcpu";
 217                 timer_clocksource.name = "time-travel-clock";
 218                 return 1;
 219         }
 220
 221         if (!*str) {
 222                 time_travel_mode = TT_MODE_BASIC;
 223                 timer_clockevent.name = "time-travel-timer";
 224                 timer_clocksource.name = "time-travel-clock";
 225                 return 1;
 226         }
 227
 228         return -EINVAL;
 229 }
 230
 231 __setup("time-travel", setup_time_travel);
 232 __uml_help(setup_time_travel,
 233 "time-travel\n"
 234 "This option just enables basic time travel mode, in which the clock/timers\n"
 235 "inside the UML instance skip forward when there's nothing to do, rather than\n"
 236 "waiting for real time to elapse. However, instance CPU speed is limited by\n"
 237 "the real CPU speed, so e.g. a 10ms timer will always fire after ~10ms wall\n"
 238 "clock (but quicker when there's nothing to do).\n"
 239 "\n"
 240 "time-travel=inf-cpu\n"
 241 "This enables time travel mode with infinite processing power, in which there\n"
 242 "are no wall clock timers, and any CPU processing happens - as seen from the\n"
 243 "guest - instantly. This can be useful for accurate simulation regardless of\n"
 244 "debug overhead, physical CPU speed, etc. but is somewhat dangerous as it can\n"
 245 "easily lead to getting stuck (e.g. if anything in the system busy loops).\n");
 246
 247 int setup_time_travel_start(char *str)
 248 {
 249         int err;
 250
 251         err = kstrtoull(str, 0, &time_travel_start);
 252         if (err)
 253                 return err;
 254
 255         time_travel_start_set = 1;
 256         return 1;
 257 }
 258
 259 __setup("time-travel-start", setup_time_travel_start);
 260 __uml_help(setup_time_travel_start,
 261 "time-travel-start=<seconds>\n"
 262 "Configure the UML instance's wall clock to start at this value rather than\n"
 263 "the host's wall clock at the time of UML boot.\n");
 264 #endif