migration/global_state.c

/*
 * Global State configuration
 *
 * Copyright (c) 2014-2017 Red Hat Inc
 *
 * Authors:
 *  Juan Quintela <quintela@redhat.com>
 *
 * 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 "qemu/cutils.h"
#include "qemu/error-report.h"
#include "qapi/error.h"
#include "migration.h"
#include "migration/global_state.h"
#include "migration/vmstate.h"
#include "trace.h"

typedef struct {
    uint32_t size;
    uint8_t runstate[100];
    RunState state;
    bool received;
} GlobalState;

static GlobalState global_state;

int global_state_store(void)
{
    if (!runstate_store((char *)global_state.runstate,
                        sizeof(global_state.runstate))) {
        error_report("runstate name too big: %s", global_state.runstate);
        trace_migrate_state_too_big();
        return -EINVAL;
    }
    return 0;
}

void global_state_store_running(void)
{
    const char *state = RunState_str(RUN_STATE_RUNNING);
    assert(strlen(state) < sizeof(global_state.runstate));
    strncpy((char *)global_state.runstate,
           state, sizeof(global_state.runstate));
}

bool global_state_received(void)
{
    return global_state.received;
}

RunState global_state_get_runstate(void)
{
    return global_state.state;
}

static bool global_state_needed(void *opaque)
{
    GlobalState *s = opaque;
    char *runstate = (char *)s->runstate;

    /* If it is not optional, it is mandatory */

    if (migrate_get_current()->store_global_state) {
        return true;
    }

    /* If state is running or paused, it is not needed */

    if (strcmp(runstate, "running") == 0 ||
        strcmp(runstate, "paused") == 0) {
        return false;
    }

    /* for any other state it is needed */
    return true;
}

static int global_state_post_load(void *opaque, int version_id)
{
    GlobalState *s = opaque;
    Error *local_err = NULL;
    int r;
    char *runstate = (char *)s->runstate;

    s->received = true;
    trace_migrate_global_state_post_load(runstate);

    if (strnlen((char *)s->runstate,
                sizeof(s->runstate)) == sizeof(s->runstate)) {
        /*
         * This condition should never happen during migration, because
         * all runstate names are shorter than 100 bytes (the size of
         * s->runstate). However, a malicious stream could overflow
         * the qapi_enum_parse() call, so we force the last character
         * to a NUL byte.
         */
        s->runstate[sizeof(s->runstate) - 1] = '\0';
    }
    r = qapi_enum_parse(&RunState_lookup, runstate, -1, &local_err);

    if (r == -1) {
        if (local_err) {
            error_report_err(local_err);
        }
        return -EINVAL;
    }
    s->state = r;

    return 0;
}

static int global_state_pre_save(void *opaque)
{
    GlobalState *s = opaque;

    trace_migrate_global_state_pre_save((char *)s->runstate);
    s->size = strnlen((char *)s->runstate, sizeof(s->runstate)) + 1;
    assert(s->size <= sizeof(s->runstate));

    return 0;
}

static const VMStateDescription vmstate_globalstate = {
    .name = "globalstate",
    .version_id = 1,
    .minimum_version_id = 1,
    .post_load = global_state_post_load,
    .pre_save = global_state_pre_save,
    .needed = global_state_needed,
    .fields = (VMStateField[]) {
        VMSTATE_UINT32(size, GlobalState),
        VMSTATE_BUFFER(runstate, GlobalState),
        VMSTATE_END_OF_LIST()
    },
};

void register_global_state(void)
{
    /* We would use it independently that we receive it */
    strcpy((char *)&global_state.runstate, "");
    global_state.received = false;
    vmstate_register(NULL, 0, &vmstate_globalstate, &global_state);
}