replay/replay.c

/*
 * replay.c
 *
 * Copyright (c) 2010-2015 Institute for System Programming
 *                         of the Russian Academy of Sciences.
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#include "qemu/osdep.h"
#include "qapi/error.h"
#include "sysemu/cpu-timers.h"
#include "sysemu/replay.h"
#include "sysemu/runstate.h"
#include "replay-internal.h"
#include "qemu/main-loop.h"
#include "qemu/option.h"
#include "sysemu/cpus.h"
#include "qemu/error-report.h"

/* Current version of the replay mechanism.
   Increase it when file format changes. */
#define REPLAY_VERSION              0xe0200a
/* Size of replay log header */
#define HEADER_SIZE                 (sizeof(uint32_t) + sizeof(uint64_t))

ReplayMode replay_mode = REPLAY_MODE_NONE;
char *replay_snapshot;

/* Name of replay file  */
static char *replay_filename;
ReplayState replay_state;
static GSList *replay_blockers;

/* Replay breakpoints */
uint64_t replay_break_icount = -1ULL;
QEMUTimer *replay_break_timer;

bool replay_next_event_is(int event)
{
    bool res = false;

    /* nothing to skip - not all instructions used */
    if (replay_state.instruction_count != 0) {
        assert(replay_state.data_kind == EVENT_INSTRUCTION);
        return event == EVENT_INSTRUCTION;
    }

    while (true) {
        unsigned int data_kind = replay_state.data_kind;
        if (event == data_kind) {
            res = true;
        }
        switch (data_kind) {
        case EVENT_SHUTDOWN ... EVENT_SHUTDOWN_LAST:
            replay_finish_event();
            qemu_system_shutdown_request(data_kind - EVENT_SHUTDOWN);
            break;
        default:
            /* clock, time_t, checkpoint and other events */
            return res;
        }
    }
    return res;
}

uint64_t replay_get_current_icount(void)
{
    return icount_get_raw();
}

int replay_get_instructions(void)
{
    int res = 0;
    replay_mutex_lock();
    if (replay_next_event_is(EVENT_INSTRUCTION)) {
        res = replay_state.instruction_count;
        if (replay_break_icount != -1LL) {
            uint64_t current = replay_get_current_icount();
            assert(replay_break_icount >= current);
            if (current + res > replay_break_icount) {
                res = replay_break_icount - current;
            }
        }
    }
    replay_mutex_unlock();
    return res;
}

void replay_account_executed_instructions(void)
{
    if (replay_mode == REPLAY_MODE_PLAY) {
        g_assert(replay_mutex_locked());
        if (replay_state.instruction_count > 0) {
            int count = (int)(replay_get_current_icount()
                              - replay_state.current_icount);

            /* Time can only go forward */
            assert(count >= 0);

            replay_state.instruction_count -= count;
            replay_state.current_icount += count;
            if (replay_state.instruction_count == 0) {
                assert(replay_state.data_kind == EVENT_INSTRUCTION);
                replay_finish_event();
                /* Wake up iothread. This is required because
                   timers will not expire until clock counters
                   will be read from the log. */
                qemu_notify_event();
            }
            /* Execution reached the break step */
            if (replay_break_icount == replay_state.current_icount) {
                /* Cannot make callback directly from the vCPU thread */
                timer_mod_ns(replay_break_timer,
                    qemu_clock_get_ns(QEMU_CLOCK_REALTIME));
            }
        }
    }
}

bool replay_exception(void)
{

    if (replay_mode == REPLAY_MODE_RECORD) {
        g_assert(replay_mutex_locked());
        replay_save_instructions();
        replay_put_event(EVENT_EXCEPTION);
        return true;
    } else if (replay_mode == REPLAY_MODE_PLAY) {
        g_assert(replay_mutex_locked());
        bool res = replay_has_exception();
        if (res) {
            replay_finish_event();
        }
        return res;
    }

    return true;
}

bool replay_has_exception(void)
{
    bool res = false;
    if (replay_mode == REPLAY_MODE_PLAY) {
        g_assert(replay_mutex_locked());
        replay_account_executed_instructions();
        res = replay_next_event_is(EVENT_EXCEPTION);
    }

    return res;
}

bool replay_interrupt(void)
{
    if (replay_mode == REPLAY_MODE_RECORD) {
        g_assert(replay_mutex_locked());
        replay_save_instructions();
        replay_put_event(EVENT_INTERRUPT);
        return true;
    } else if (replay_mode == REPLAY_MODE_PLAY) {
        g_assert(replay_mutex_locked());
        bool res = replay_has_interrupt();
        if (res) {
            replay_finish_event();
        }
        return res;
    }

    return true;
}

bool replay_has_interrupt(void)
{
    bool res = false;
    if (replay_mode == REPLAY_MODE_PLAY) {
        g_assert(replay_mutex_locked());
        replay_account_executed_instructions();
        res = replay_next_event_is(EVENT_INTERRUPT);
    }
    return res;
}

void replay_shutdown_request(ShutdownCause cause)
{
    if (replay_mode == REPLAY_MODE_RECORD) {
        g_assert(replay_mutex_locked());
        replay_put_event(EVENT_SHUTDOWN + cause);
    }
}

bool replay_checkpoint(ReplayCheckpoint checkpoint)
{
    bool res = false;
    static bool in_checkpoint;
    assert(EVENT_CHECKPOINT + checkpoint <= EVENT_CHECKPOINT_LAST);

    if (!replay_file) {
        return true;
    }

    if (in_checkpoint) {
        /* If we are already in checkpoint, then there is no need
           for additional synchronization.
           Recursion occurs when HW event modifies timers.
           Timer modification may invoke the checkpoint and
           proceed to recursion. */
        return true;
    }
    in_checkpoint = true;

    replay_save_instructions();

    if (replay_mode == REPLAY_MODE_PLAY) {
        g_assert(replay_mutex_locked());
        if (replay_next_event_is(EVENT_CHECKPOINT + checkpoint)) {
            replay_finish_event();
        } else if (replay_state.data_kind != EVENT_ASYNC) {
            res = false;
            goto out;
        }
        replay_read_events(checkpoint);
        /* replay_read_events may leave some unread events.
           Return false if not all of the events associated with
           checkpoint were processed */
        res = replay_state.data_kind != EVENT_ASYNC;
    } else if (replay_mode == REPLAY_MODE_RECORD) {
        g_assert(replay_mutex_locked());
        replay_put_event(EVENT_CHECKPOINT + checkpoint);
        /* This checkpoint belongs to several threads.
           Processing events from different threads is
           non-deterministic */
        if (checkpoint != CHECKPOINT_CLOCK_WARP_START
            /* FIXME: this is temporary fix, other checkpoints
                      may also be invoked from the different threads someday.
                      Asynchronous event processing should be refactored
                      to create additional replay event kind which is
                      nailed to the one of the threads and which processes
                      the event queue. */
            && checkpoint != CHECKPOINT_CLOCK_VIRTUAL) {
            replay_save_events(checkpoint);
        }
        res = true;
    }
out:
    in_checkpoint = false;
    return res;
}

bool replay_has_checkpoint(void)
{
    bool res = false;
    if (replay_mode == REPLAY_MODE_PLAY) {
        g_assert(replay_mutex_locked());
        replay_account_executed_instructions();
        res = EVENT_CHECKPOINT <= replay_state.data_kind
              && replay_state.data_kind <= EVENT_CHECKPOINT_LAST;
    }
    return res;
}

static void replay_enable(const char *fname, int mode)
{
    const char *fmode = NULL;
    assert(!replay_file);

    switch (mode) {
    case REPLAY_MODE_RECORD:
        fmode = "wb";
        break;
    case REPLAY_MODE_PLAY:
        fmode = "rb";
        break;
    default:
        fprintf(stderr, "Replay: internal error: invalid replay mode\n");
        exit(1);
    }

    atexit(replay_finish);

    replay_file = fopen(fname, fmode);
    if (replay_file == NULL) {
        fprintf(stderr, "Replay: open %s: %s\n", fname, strerror(errno));
        exit(1);
    }

    replay_filename = g_strdup(fname);
    replay_mode = mode;
    replay_mutex_init();

    replay_state.data_kind = -1;
    replay_state.instruction_count = 0;
    replay_state.current_icount = 0;
    replay_state.has_unread_data = 0;

    /* skip file header for RECORD and check it for PLAY */
    if (replay_mode == REPLAY_MODE_RECORD) {
        fseek(replay_file, HEADER_SIZE, SEEK_SET);
    } else if (replay_mode == REPLAY_MODE_PLAY) {
        unsigned int version = replay_get_dword();
        if (version != REPLAY_VERSION) {
            fprintf(stderr, "Replay: invalid input log file version\n");
            exit(1);
        }
        /* go to the beginning */
        fseek(replay_file, HEADER_SIZE, SEEK_SET);
        replay_fetch_data_kind();
    }

    replay_init_events();
}

void replay_configure(QemuOpts *opts)
{
    const char *fname;
    const char *rr;
    ReplayMode mode = REPLAY_MODE_NONE;
    Location loc;

    if (!opts) {
        return;
    }

    loc_push_none(&loc);
    qemu_opts_loc_restore(opts);

    rr = qemu_opt_get(opts, "rr");
    if (!rr) {
        /* Just enabling icount */
        goto out;
    } else if (!strcmp(rr, "record")) {
        mode = REPLAY_MODE_RECORD;
    } else if (!strcmp(rr, "replay")) {
        mode = REPLAY_MODE_PLAY;
    } else {
        error_report("Invalid icount rr option: %s", rr);
        exit(1);
    }

    fname = qemu_opt_get(opts, "rrfile");
    if (!fname) {
        error_report("File name not specified for replay");
        exit(1);
    }

    replay_snapshot = g_strdup(qemu_opt_get(opts, "rrsnapshot"));
    replay_vmstate_register();
    replay_enable(fname, mode);

out:
    loc_pop(&loc);
}

void replay_start(void)
{
    if (replay_mode == REPLAY_MODE_NONE) {
        return;
    }

    if (replay_blockers) {
        error_reportf_err(replay_blockers->data, "Record/replay: ");
        exit(1);
    }
    if (!icount_enabled()) {
        error_report("Please enable icount to use record/replay");
        exit(1);
    }

    /* Timer for snapshotting will be set up here. */

    replay_enable_events();
}

void replay_finish(void)
{
    if (replay_mode == REPLAY_MODE_NONE) {
        return;
    }

    replay_save_instructions();

    /* finalize the file */
    if (replay_file) {
        if (replay_mode == REPLAY_MODE_RECORD) {
            /*
             * Can't do it in the signal handler, therefore
             * add shutdown event here for the case of Ctrl-C.
             */
            replay_shutdown_request(SHUTDOWN_CAUSE_HOST_SIGNAL);
            /* write end event */
            replay_put_event(EVENT_END);

            /* write header */
            fseek(replay_file, 0, SEEK_SET);
            replay_put_dword(REPLAY_VERSION);
        }

        fclose(replay_file);
        replay_file = NULL;
    }
    if (replay_filename) {
        g_free(replay_filename);
        replay_filename = NULL;
    }

    g_free(replay_snapshot);
    replay_snapshot = NULL;

    replay_mode = REPLAY_MODE_NONE;

    replay_finish_events();
}

void replay_add_blocker(Error *reason)
{
    replay_blockers = g_slist_prepend(replay_blockers, reason);
}

const char *replay_get_filename(void)
{
    return replay_filename;
}