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  * Copyright (C) 2019 Intel Corporation
   8  */
   9
  10 #include <linux/clockchips.h>
  11 #include <linux/init.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/jiffies.h>
  14 #include <linux/mm.h>
  15 #include <linux/sched.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/threads.h>
  18 #include <asm/irq.h>
  19 #include <asm/param.h>
  20 #include <kern_util.h>
  21 #include <os.h>
  22 #include <linux/time-internal.h>
  23 #include <linux/um_timetravel.h>
  24 #include <shared/init.h>
  25
  26 #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
  27 enum time_travel_mode time_travel_mode;
  28 EXPORT_SYMBOL_GPL(time_travel_mode);
  29
  30 static bool time_travel_start_set;
  31 static unsigned long long time_travel_start;
  32 static unsigned long long time_travel_time;
  33 static LIST_HEAD(time_travel_events);
  34 static LIST_HEAD(time_travel_irqs);
  35 static unsigned long long time_travel_timer_interval;
  36 static unsigned long long time_travel_next_event;
  37 static struct time_travel_event time_travel_timer_event;
  38 static int time_travel_ext_fd = -1;
  39 static unsigned int time_travel_ext_waiting;
  40 static bool time_travel_ext_prev_request_valid;
  41 static unsigned long long time_travel_ext_prev_request;
  42 static bool time_travel_ext_free_until_valid;
  43 static unsigned long long time_travel_ext_free_until;
  44
  45 static void time_travel_set_time(unsigned long long ns)
  46 {
  47         if (unlikely(ns < time_travel_time))
  48                 panic("time-travel: time goes backwards %lld -> %lld\n",
  49                       time_travel_time, ns);
  50         else if (unlikely(ns >= S64_MAX))
  51                 panic("The system was going to sleep forever, aborting");
  52
  53         time_travel_time = ns;
  54 }
  55
  56 enum time_travel_message_handling {
  57         TTMH_IDLE,
  58         TTMH_POLL,
  59         TTMH_READ,
  60 };
  61
  62 static void time_travel_handle_message(struct um_timetravel_msg *msg,
  63                                        enum time_travel_message_handling mode)
  64 {
  65         struct um_timetravel_msg resp = {
  66                 .op = UM_TIMETRAVEL_ACK,
  67         };
  68         int ret;
  69
  70         /*
  71          * We can't unlock here, but interrupt signals with a timetravel_handler
  72          * (see um_request_irq_tt) get to the timetravel_handler anyway.
  73          */
  74         if (mode != TTMH_READ) {
  75                 BUG_ON(mode == TTMH_IDLE && !irqs_disabled());
  76
  77                 while (os_poll(1, &time_travel_ext_fd) != 0) {
  78                         /* nothing */
  79                 }
  80         }
  81
  82         ret = os_read_file(time_travel_ext_fd, msg, sizeof(*msg));
  83
  84         if (ret == 0)
  85                 panic("time-travel external link is broken\n");
  86         if (ret != sizeof(*msg))
  87                 panic("invalid time-travel message - %d bytes\n", ret);
  88
  89         switch (msg->op) {
  90         default:
  91                 WARN_ONCE(1, "time-travel: unexpected message %lld\n",
  92                           (unsigned long long)msg->op);
  93                 break;
  94         case UM_TIMETRAVEL_ACK:
  95                 return;
  96         case UM_TIMETRAVEL_RUN:
  97                 time_travel_set_time(msg->time);
  98                 break;
  99         case UM_TIMETRAVEL_FREE_UNTIL:
 100                 time_travel_ext_free_until_valid = true;
 101                 time_travel_ext_free_until = msg->time;
 102                 break;
 103         }
 104
 105         resp.seq = msg->seq;
 106         os_write_file(time_travel_ext_fd, &resp, sizeof(resp));
 107 }
 108
 109 static u64 time_travel_ext_req(u32 op, u64 time)
 110 {
 111         static int seq;
 112         int mseq = ++seq;
 113         struct um_timetravel_msg msg = {
 114                 .op = op,
 115                 .time = time,
 116                 .seq = mseq,
 117         };
 118
 119         /*
 120          * We need to block even the timetravel handlers of SIGIO here and
 121          * only restore their use when we got the ACK - otherwise we may
 122          * (will) get interrupted by that, try to queue the IRQ for future
 123          * processing and thus send another request while we're still waiting
 124          * for an ACK, but the peer doesn't know we got interrupted and will
 125          * send the ACKs in the same order as the message, but we'd need to
 126          * see them in the opposite order ...
 127          *
 128          * This wouldn't matter *too* much, but some ACKs carry the
 129          * current time (for UM_TIMETRAVEL_GET) and getting another
 130          * ACK without a time would confuse us a lot!
 131          *
 132          * The sequence number assignment that happens here lets us
 133          * debug such message handling issues more easily.
 134          */
 135         block_signals_hard();
 136         os_write_file(time_travel_ext_fd, &msg, sizeof(msg));
 137
 138         while (msg.op != UM_TIMETRAVEL_ACK)
 139                 time_travel_handle_message(&msg, TTMH_READ);
 140
 141         if (msg.seq != mseq)
 142                 panic("time-travel: ACK message has different seqno! op=%d, seq=%d != %d time=%lld\n",
 143                       msg.op, msg.seq, mseq, msg.time);
 144
 145         if (op == UM_TIMETRAVEL_GET)
 146                 time_travel_set_time(msg.time);
 147         unblock_signals_hard();
 148
 149         return msg.time;
 150 }
 151
 152 void __time_travel_wait_readable(int fd)
 153 {
 154         int fds[2] = { fd, time_travel_ext_fd };
 155         int ret;
 156
 157         if (time_travel_mode != TT_MODE_EXTERNAL)
 158                 return;
 159
 160         while ((ret = os_poll(2, fds))) {
 161                 struct um_timetravel_msg msg;
 162
 163                 if (ret == 1)
 164                         time_travel_handle_message(&msg, TTMH_READ);
 165         }
 166 }
 167 EXPORT_SYMBOL_GPL(__time_travel_wait_readable);
 168
 169 static void time_travel_ext_update_request(unsigned long long time)
 170 {
 171         if (time_travel_mode != TT_MODE_EXTERNAL)
 172                 return;
 173
 174         /* asked for exactly this time previously */
 175         if (time_travel_ext_prev_request_valid &&
 176             time == time_travel_ext_prev_request)
 177                 return;
 178
 179         /*
 180          * if we're running and are allowed to run past the request
 181          * then we don't need to update it either
 182          */
 183         if (!time_travel_ext_waiting && time_travel_ext_free_until_valid &&
 184             time < time_travel_ext_free_until)
 185                 return;
 186
 187         time_travel_ext_prev_request = time;
 188         time_travel_ext_prev_request_valid = true;
 189         time_travel_ext_req(UM_TIMETRAVEL_REQUEST, time);
 190 }
 191
 192 void __time_travel_propagate_time(void)
 193 {
 194         static unsigned long long last_propagated;
 195
 196         if (last_propagated == time_travel_time)
 197                 return;
 198
 199         time_travel_ext_req(UM_TIMETRAVEL_UPDATE, time_travel_time);
 200         last_propagated = time_travel_time;
 201 }
 202 EXPORT_SYMBOL_GPL(__time_travel_propagate_time);
 203
 204 /* returns true if we must do a wait to the simtime device */
 205 static bool time_travel_ext_request(unsigned long long time)
 206 {
 207         /*
 208          * If we received an external sync point ("free until") then we
 209          * don't have to request/wait for anything until then, unless
 210          * we're already waiting.
 211          */
 212         if (!time_travel_ext_waiting && time_travel_ext_free_until_valid &&
 213             time < time_travel_ext_free_until)
 214                 return false;
 215
 216         time_travel_ext_update_request(time);
 217         return true;
 218 }
 219
 220 static void time_travel_ext_wait(bool idle)
 221 {
 222         struct um_timetravel_msg msg = {
 223                 .op = UM_TIMETRAVEL_ACK,
 224         };
 225
 226         time_travel_ext_prev_request_valid = false;
 227         time_travel_ext_free_until_valid = false;
 228         time_travel_ext_waiting++;
 229
 230         time_travel_ext_req(UM_TIMETRAVEL_WAIT, -1);
 231
 232         /*
 233          * Here we are deep in the idle loop, so we have to break out of the
 234          * kernel abstraction in a sense and implement this in terms of the
 235          * UML system waiting on the VQ interrupt while sleeping, when we get
 236          * the signal it'll call time_travel_ext_vq_notify_done() completing the
 237          * call.
 238          */
 239         while (msg.op != UM_TIMETRAVEL_RUN)
 240                 time_travel_handle_message(&msg, idle ? TTMH_IDLE : TTMH_POLL);
 241
 242         time_travel_ext_waiting--;
 243
 244         /* we might request more stuff while polling - reset when we run */
 245         time_travel_ext_prev_request_valid = false;
 246 }
 247
 248 static void time_travel_ext_get_time(void)
 249 {
 250         time_travel_ext_req(UM_TIMETRAVEL_GET, -1);
 251 }
 252
 253 static void __time_travel_update_time(unsigned long long ns, bool idle)
 254 {
 255         if (time_travel_mode == TT_MODE_EXTERNAL && time_travel_ext_request(ns))
 256                 time_travel_ext_wait(idle);
 257         else
 258                 time_travel_set_time(ns);
 259 }
 260
 261 static struct time_travel_event *time_travel_first_event(void)
 262 {
 263         return list_first_entry_or_null(&time_travel_events,
 264                                         struct time_travel_event,
 265                                         list);
 266 }
 267
 268 static void __time_travel_add_event(struct time_travel_event *e,
 269                                     unsigned long long time)
 270 {
 271         struct time_travel_event *tmp;
 272         bool inserted = false;
 273         unsigned long flags;
 274
 275         if (e->pending)
 276                 return;
 277
 278         e->pending = true;
 279         e->time = time;
 280
 281         local_irq_save(flags);
 282         list_for_each_entry(tmp, &time_travel_events, list) {
 283                 /*
 284                  * Add the new entry before one with higher time,
 285                  * or if they're equal and both on stack, because
 286                  * in that case we need to unwind the stack in the
 287                  * right order, and the later event (timer sleep
 288                  * or such) must be dequeued first.
 289                  */
 290                 if ((tmp->time > e->time) ||
 291                     (tmp->time == e->time && tmp->onstack && e->onstack)) {
 292                         list_add_tail(&e->list, &tmp->list);
 293                         inserted = true;
 294                         break;
 295                 }
 296         }
 297
 298         if (!inserted)
 299                 list_add_tail(&e->list, &time_travel_events);
 300
 301         tmp = time_travel_first_event();
 302         time_travel_ext_update_request(tmp->time);
 303         time_travel_next_event = tmp->time;
 304         local_irq_restore(flags);
 305 }
 306
 307 static void time_travel_add_event(struct time_travel_event *e,
 308                                   unsigned long long time)
 309 {
 310         if (WARN_ON(!e->fn))
 311                 return;
 312
 313         __time_travel_add_event(e, time);
 314 }
 315
 316 void time_travel_add_event_rel(struct time_travel_event *e,
 317                                unsigned long long delay_ns)
 318 {
 319         time_travel_add_event(e, time_travel_time + delay_ns);
 320 }
 321
 322 void time_travel_periodic_timer(struct time_travel_event *e)
 323 {
 324         time_travel_add_event(&time_travel_timer_event,
 325                               time_travel_time + time_travel_timer_interval);
 326         deliver_alarm();
 327 }
 328
 329 void deliver_time_travel_irqs(void)
 330 {
 331         struct time_travel_event *e;
 332         unsigned long flags;
 333
 334         /*
 335          * Don't do anything for most cases. Note that because here we have
 336          * to disable IRQs (and re-enable later) we'll actually recurse at
 337          * the end of the function, so this is strictly necessary.
 338          */
 339         if (likely(list_empty(&time_travel_irqs)))
 340                 return;
 341
 342         local_irq_save(flags);
 343         irq_enter();
 344         while ((e = list_first_entry_or_null(&time_travel_irqs,
 345                                              struct time_travel_event,
 346                                              list))) {
 347                 list_del(&e->list);
 348                 e->pending = false;
 349                 e->fn(e);
 350         }
 351         irq_exit();
 352         local_irq_restore(flags);
 353 }
 354
 355 static void time_travel_deliver_event(struct time_travel_event *e)
 356 {
 357         if (e == &time_travel_timer_event) {
 358                 /*
 359                  * deliver_alarm() does the irq_enter/irq_exit
 360                  * by itself, so must handle it specially here
 361                  */
 362                 e->fn(e);
 363         } else if (irqs_disabled()) {
 364                 list_add_tail(&e->list, &time_travel_irqs);
 365                 /*
 366                  * set pending again, it was set to false when the
 367                  * event was deleted from the original list, but
 368                  * now it's still pending until we deliver the IRQ.
 369                  */
 370                 e->pending = true;
 371         } else {
 372                 unsigned long flags;
 373
 374                 local_irq_save(flags);
 375                 irq_enter();
 376                 e->fn(e);
 377                 irq_exit();
 378                 local_irq_restore(flags);
 379         }
 380 }
 381
 382 bool time_travel_del_event(struct time_travel_event *e)
 383 {
 384         unsigned long flags;
 385
 386         if (!e->pending)
 387                 return false;
 388         local_irq_save(flags);
 389         list_del(&e->list);
 390         e->pending = false;
 391         local_irq_restore(flags);
 392         return true;
 393 }
 394
 395 static void time_travel_update_time(unsigned long long next, bool idle)
 396 {
 397         struct time_travel_event ne = {
 398                 .onstack = true,
 399         };
 400         struct time_travel_event *e;
 401         bool finished = idle;
 402
 403         /* add it without a handler - we deal with that specifically below */
 404         __time_travel_add_event(&ne, next);
 405
 406         do {
 407                 e = time_travel_first_event();
 408
 409                 BUG_ON(!e);
 410                 __time_travel_update_time(e->time, idle);
 411
 412                 /* new events may have been inserted while we were waiting */
 413                 if (e == time_travel_first_event()) {
 414                         BUG_ON(!time_travel_del_event(e));
 415                         BUG_ON(time_travel_time != e->time);
 416
 417                         if (e == &ne) {
 418                                 finished = true;
 419                         } else {
 420                                 if (e->onstack)
 421                                         panic("On-stack event dequeued outside of the stack! time=%lld, event time=%lld, event=%pS\n",
 422                                               time_travel_time, e->time, e);
 423                                 time_travel_deliver_event(e);
 424                         }
 425                 }
 426
 427                 e = time_travel_first_event();
 428                 if (e)
 429                         time_travel_ext_update_request(e->time);
 430         } while (ne.pending && !finished);
 431
 432         time_travel_del_event(&ne);
 433 }
 434
 435 void time_travel_ndelay(unsigned long nsec)
 436 {
 437         time_travel_update_time(time_travel_time + nsec, false);
 438 }
 439 EXPORT_SYMBOL(time_travel_ndelay);
 440
 441 void time_travel_add_irq_event(struct time_travel_event *e)
 442 {
 443         BUG_ON(time_travel_mode != TT_MODE_EXTERNAL);
 444
 445         time_travel_ext_get_time();
 446         /*
 447          * We could model interrupt latency here, for now just
 448          * don't have any latency at all and request the exact
 449          * same time (again) to run the interrupt...
 450          */
 451         time_travel_add_event(e, time_travel_time);
 452 }
 453 EXPORT_SYMBOL_GPL(time_travel_add_irq_event);
 454
 455 static void time_travel_oneshot_timer(struct time_travel_event *e)
 456 {
 457         deliver_alarm();
 458 }
 459
 460 void time_travel_sleep(void)
 461 {
 462         /*
 463          * Wait "forever" (using S64_MAX because there are some potential
 464          * wrapping issues, especially with the current TT_MODE_EXTERNAL
 465          * controller application.
 466          */
 467         unsigned long long next = S64_MAX;
 468
 469         if (time_travel_mode == TT_MODE_BASIC)
 470                 os_timer_disable();
 471
 472         time_travel_update_time(next, true);
 473
 474         if (time_travel_mode == TT_MODE_BASIC &&
 475             time_travel_timer_event.pending) {
 476                 if (time_travel_timer_event.fn == time_travel_periodic_timer) {
 477                         /*
 478                          * This is somewhat wrong - we should get the first
 479                          * one sooner like the os_timer_one_shot() below...
 480                          */
 481                         os_timer_set_interval(time_travel_timer_interval);
 482                 } else {
 483                         os_timer_one_shot(time_travel_timer_event.time - next);
 484                 }
 485         }
 486 }
 487
 488 static void time_travel_handle_real_alarm(void)
 489 {
 490         time_travel_set_time(time_travel_next_event);
 491
 492         time_travel_del_event(&time_travel_timer_event);
 493
 494         if (time_travel_timer_event.fn == time_travel_periodic_timer)
 495                 time_travel_add_event(&time_travel_timer_event,
 496                                       time_travel_time +
 497                                       time_travel_timer_interval);
 498 }
 499
 500 static void time_travel_set_interval(unsigned long long interval)
 501 {
 502         time_travel_timer_interval = interval;
 503 }
 504
 505 static int time_travel_connect_external(const char *socket)
 506 {
 507         const char *sep;
 508         unsigned long long id = (unsigned long long)-1;
 509         int rc;
 510
 511         if ((sep = strchr(socket, ':'))) {
 512                 char buf[25] = {};
 513                 if (sep - socket > sizeof(buf) - 1)
 514                         goto invalid_number;
 515
 516                 memcpy(buf, socket, sep - socket);
 517                 if (kstrtoull(buf, 0, &id)) {
 518 invalid_number:
 519                         panic("time-travel: invalid external ID in string '%s'\n",
 520                               socket);
 521                         return -EINVAL;
 522                 }
 523
 524                 socket = sep + 1;
 525         }
 526
 527         rc = os_connect_socket(socket);
 528         if (rc < 0) {
 529                 panic("time-travel: failed to connect to external socket %s\n",
 530                       socket);
 531                 return rc;
 532         }
 533
 534         time_travel_ext_fd = rc;
 535
 536         time_travel_ext_req(UM_TIMETRAVEL_START, id);
 537
 538         return 1;
 539 }
 540
 541 static void time_travel_set_start(void)
 542 {
 543         if (time_travel_start_set)
 544                 return;
 545
 546         switch (time_travel_mode) {
 547         case TT_MODE_EXTERNAL:
 548                 time_travel_start = time_travel_ext_req(UM_TIMETRAVEL_GET_TOD, -1);
 549                 /* controller gave us the *current* time, so adjust by that */
 550                 time_travel_ext_get_time();
 551                 time_travel_start -= time_travel_time;
 552                 break;
 553         case TT_MODE_INFCPU:
 554         case TT_MODE_BASIC:
 555                 if (!time_travel_start_set)
 556                         time_travel_start = os_persistent_clock_emulation();
 557                 break;
 558         case TT_MODE_OFF:
 559                 /* we just read the host clock with os_persistent_clock_emulation() */
 560                 break;
 561         }
 562
 563         time_travel_start_set = true;
 564 }
 565 #else /* CONFIG_UML_TIME_TRAVEL_SUPPORT */
 566 #define time_travel_start_set 0
 567 #define time_travel_start 0
 568 #define time_travel_time 0
 569 #define time_travel_ext_waiting 0
 570
 571 static inline void time_travel_update_time(unsigned long long ns, bool retearly)
 572 {
 573 }
 574
 575 static inline void time_travel_handle_real_alarm(void)
 576 {
 577 }
 578
 579 static void time_travel_set_interval(unsigned long long interval)
 580 {
 581 }
 582
 583 static inline void time_travel_set_start(void)
 584 {
 585 }
 586
 587 /* fail link if this actually gets used */
 588 extern u64 time_travel_ext_req(u32 op, u64 time);
 589
 590 /* these are empty macros so the struct/fn need not exist */
 591 #define time_travel_add_event(e, time) do { } while (0)
 592 /* externally not usable - redefine here so we can */
 593 #undef time_travel_del_event
 594 #define time_travel_del_event(e) do { } while (0)
 595 #endif
 596
 597 void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 598 {
 599         unsigned long flags;
 600
 601         /*
 602          * In basic time-travel mode we still get real interrupts
 603          * (signals) but since we don't read time from the OS, we
 604          * must update the simulated time here to the expiry when
 605          * we get a signal.
 606          * This is not the case in inf-cpu mode, since there we
 607          * never get any real signals from the OS.
 608          */
 609         if (time_travel_mode == TT_MODE_BASIC)
 610                 time_travel_handle_real_alarm();
 611
 612         local_irq_save(flags);
 613         do_IRQ(TIMER_IRQ, regs);
 614         local_irq_restore(flags);
 615 }
 616
 617 static int itimer_shutdown(struct clock_event_device *evt)
 618 {
 619         if (time_travel_mode != TT_MODE_OFF)
 620                 time_travel_del_event(&time_travel_timer_event);
 621
 622         if (time_travel_mode != TT_MODE_INFCPU &&
 623             time_travel_mode != TT_MODE_EXTERNAL)
 624                 os_timer_disable();
 625
 626         return 0;
 627 }
 628
 629 static int itimer_set_periodic(struct clock_event_device *evt)
 630 {
 631         unsigned long long interval = NSEC_PER_SEC / HZ;
 632
 633         if (time_travel_mode != TT_MODE_OFF) {
 634                 time_travel_del_event(&time_travel_timer_event);
 635                 time_travel_set_event_fn(&time_travel_timer_event,
 636                                          time_travel_periodic_timer);
 637                 time_travel_set_interval(interval);
 638                 time_travel_add_event(&time_travel_timer_event,
 639                                       time_travel_time + interval);
 640         }
 641
 642         if (time_travel_mode != TT_MODE_INFCPU &&
 643             time_travel_mode != TT_MODE_EXTERNAL)
 644                 os_timer_set_interval(interval);
 645
 646         return 0;
 647 }
 648
 649 static int itimer_next_event(unsigned long delta,
 650                              struct clock_event_device *evt)
 651 {
 652         delta += 1;
 653
 654         if (time_travel_mode != TT_MODE_OFF) {
 655                 time_travel_del_event(&time_travel_timer_event);
 656                 time_travel_set_event_fn(&time_travel_timer_event,
 657                                          time_travel_oneshot_timer);
 658                 time_travel_add_event(&time_travel_timer_event,
 659                                       time_travel_time + delta);
 660         }
 661
 662         if (time_travel_mode != TT_MODE_INFCPU &&
 663             time_travel_mode != TT_MODE_EXTERNAL)
 664                 return os_timer_one_shot(delta);
 665
 666         return 0;
 667 }
 668
 669 static int itimer_one_shot(struct clock_event_device *evt)
 670 {
 671         return itimer_next_event(0, evt);
 672 }
 673
 674 static struct clock_event_device timer_clockevent = {
 675         .name                   = "posix-timer",
 676         .rating                 = 250,
 677         .cpumask                = cpu_possible_mask,
 678         .features               = CLOCK_EVT_FEAT_PERIODIC |
 679                                   CLOCK_EVT_FEAT_ONESHOT,
 680         .set_state_shutdown     = itimer_shutdown,
 681         .set_state_periodic     = itimer_set_periodic,
 682         .set_state_oneshot      = itimer_one_shot,
 683         .set_next_event         = itimer_next_event,
 684         .shift                  = 0,
 685         .max_delta_ns           = 0xffffffff,
 686         .max_delta_ticks        = 0xffffffff,
 687         .min_delta_ns           = TIMER_MIN_DELTA,
 688         .min_delta_ticks        = TIMER_MIN_DELTA, // microsecond resolution should be enough for anyone, same as 640K RAM
 689         .irq                    = 0,
 690         .mult                   = 1,
 691 };
 692
 693 static irqreturn_t um_timer(int irq, void *dev)
 694 {
 695         if (get_current()->mm != NULL)
 696         {
 697         /* userspace - relay signal, results in correct userspace timers */
 698                 os_alarm_process(get_current()->mm->context.id.u.pid);
 699         }
 700
 701         (*timer_clockevent.event_handler)(&timer_clockevent);
 702
 703         return IRQ_HANDLED;
 704 }
 705
 706 static u64 timer_read(struct clocksource *cs)
 707 {
 708         if (time_travel_mode != TT_MODE_OFF) {
 709                 /*
 710                  * We make reading the timer cost a bit so that we don't get
 711                  * stuck in loops that expect time to move more than the
 712                  * exact requested sleep amount, e.g. python's socket server,
 713                  * see https://bugs.python.org/issue37026.
 714                  *
 715                  * However, don't do that when we're in interrupt or such as
 716                  * then we might recurse into our own processing, and get to
 717                  * even more waiting, and that's not good - it messes up the
 718                  * "what do I do next" and onstack event we use to know when
 719                  * to return from time_travel_update_time().
 720                  */
 721                 if (!irqs_disabled() && !in_interrupt() && !in_softirq() &&
 722                     !time_travel_ext_waiting)
 723                         time_travel_update_time(time_travel_time +
 724                                                 TIMER_MULTIPLIER,
 725                                                 false);
 726                 return time_travel_time / TIMER_MULTIPLIER;
 727         }
 728
 729         return os_nsecs() / TIMER_MULTIPLIER;
 730 }
 731
 732 static struct clocksource timer_clocksource = {
 733         .name           = "timer",
 734         .rating         = 300,
 735         .read           = timer_read,
 736         .mask           = CLOCKSOURCE_MASK(64),
 737         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 738 };
 739
 740 static void __init um_timer_setup(void)
 741 {
 742         int err;
 743
 744         err = request_irq(TIMER_IRQ, um_timer, IRQF_TIMER, "hr timer", NULL);
 745         if (err != 0)
 746                 printk(KERN_ERR "register_timer : request_irq failed - "
 747                        "errno = %d\n", -err);
 748
 749         err = os_timer_create();
 750         if (err != 0) {
 751                 printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
 752                 return;
 753         }
 754
 755         err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
 756         if (err) {
 757                 printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
 758                 return;
 759         }
 760         clockevents_register_device(&timer_clockevent);
 761 }
 762
 763 void read_persistent_clock64(struct timespec64 *ts)
 764 {
 765         long long nsecs;
 766
 767         time_travel_set_start();
 768
 769         if (time_travel_mode != TT_MODE_OFF)
 770                 nsecs = time_travel_start + time_travel_time;
 771         else
 772                 nsecs = os_persistent_clock_emulation();
 773
 774         set_normalized_timespec64(ts, nsecs / NSEC_PER_SEC,
 775                                   nsecs % NSEC_PER_SEC);
 776 }
 777
 778 void __init time_init(void)
 779 {
 780         timer_set_signal_handler();
 781         late_time_init = um_timer_setup;
 782 }
 783
 784 #ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
 785 unsigned long calibrate_delay_is_known(void)
 786 {
 787         if (time_travel_mode == TT_MODE_INFCPU ||
 788             time_travel_mode == TT_MODE_EXTERNAL)
 789                 return 1;
 790         return 0;
 791 }
 792
 793 int setup_time_travel(char *str)
 794 {
 795         if (strcmp(str, "=inf-cpu") == 0) {
 796                 time_travel_mode = TT_MODE_INFCPU;
 797                 timer_clockevent.name = "time-travel-timer-infcpu";
 798                 timer_clocksource.name = "time-travel-clock";
 799                 return 1;
 800         }
 801
 802         if (strncmp(str, "=ext:", 5) == 0) {
 803                 time_travel_mode = TT_MODE_EXTERNAL;
 804                 timer_clockevent.name = "time-travel-timer-external";
 805                 timer_clocksource.name = "time-travel-clock-external";
 806                 return time_travel_connect_external(str + 5);
 807         }
 808
 809         if (!*str) {
 810                 time_travel_mode = TT_MODE_BASIC;
 811                 timer_clockevent.name = "time-travel-timer";
 812                 timer_clocksource.name = "time-travel-clock";
 813                 return 1;
 814         }
 815
 816         return -EINVAL;
 817 }
 818
 819 __setup("time-travel", setup_time_travel);
 820 __uml_help(setup_time_travel,
 821 "time-travel\n"
 822 "This option just enables basic time travel mode, in which the clock/timers\n"
 823 "inside the UML instance skip forward when there's nothing to do, rather than\n"
 824 "waiting for real time to elapse. However, instance CPU speed is limited by\n"
 825 "the real CPU speed, so e.g. a 10ms timer will always fire after ~10ms wall\n"
 826 "clock (but quicker when there's nothing to do).\n"
 827 "\n"
 828 "time-travel=inf-cpu\n"
 829 "This enables time travel mode with infinite processing power, in which there\n"
 830 "are no wall clock timers, and any CPU processing happens - as seen from the\n"
 831 "guest - instantly. This can be useful for accurate simulation regardless of\n"
 832 "debug overhead, physical CPU speed, etc. but is somewhat dangerous as it can\n"
 833 "easily lead to getting stuck (e.g. if anything in the system busy loops).\n"
 834 "\n"
 835 "time-travel=ext:[ID:]/path/to/socket\n"
 836 "This enables time travel mode similar to =inf-cpu, except the system will\n"
 837 "use the given socket to coordinate with a central scheduler, in order to\n"
 838 "have more than one system simultaneously be on simulated time. The virtio\n"
 839 "driver code in UML knows about this so you can also simulate networks and\n"
 840 "devices using it, assuming the device has the right capabilities.\n"
 841 "The optional ID is a 64-bit integer that's sent to the central scheduler.\n");
 842
 843 int setup_time_travel_start(char *str)
 844 {
 845         int err;
 846
 847         err = kstrtoull(str, 0, &time_travel_start);
 848         if (err)
 849                 return err;
 850
 851         time_travel_start_set = 1;
 852         return 1;
 853 }
 854
 855 __setup("time-travel-start", setup_time_travel_start);
 856 __uml_help(setup_time_travel_start,
 857 "time-travel-start=<seconds>\n"
 858 "Configure the UML instance's wall clock to start at this value rather than\n"
 859 "the host's wall clock at the time of UML boot.\n");
 860 #endif