drakvuf_loop - drakvuf_vmi_event_callback

void drakvuf_vmi_event_callback (int fd, void* data)
{
    UNUSED(fd);
    drakvuf_t drakvuf = *(drakvuf_t*) data;
    status_t status = vmi_events_listen(drakvuf->vmi, drakvuf->poll_rc);
    if (VMI_SUCCESS != status)
    {
        PRINT_DEBUG("Error waiting for events or timeout, quitting...\n");
        drakvuf->interrupted = -1;
    }
}

Inside drakvuf_init :

/* register the main VMI event callback */
    drakvuf_event_fd_add(*drakvuf, (*drakvuf)->xen->evtchn_fd, drakvuf_vmi_event_callback, drakvuf);
    PRINT_DEBUG("drakvuf_init: adding event_fd done\n");

int drakvuf_event_fd_add(drakvuf_t drakvuf, int fd, event_cb_t event_cb, void* data)
{
    PRINT_DEBUG("drakvuf_event_fd_add fd=%d\n", fd);
 
    /* add new fd_info */
    fd_info_t new_fd_info = (fd_info_t) g_try_malloc0(sizeof(struct fd_info));
    new_fd_info->fd = fd;
    new_fd_info->event_cb = event_cb;
    new_fd_info->data = data;
    /* the event_fd_info list is the authoritive data source used to
       create the event_fds and fd_info_lookup data structures */
    drakvuf->event_fd_info = g_slist_append(drakvuf->event_fd_info, new_fd_info);
    drakvuf->event_fd_cnt = g_slist_length(drakvuf->event_fd_info);
    PRINT_DEBUG("size of list=%d\n", drakvuf->event_fd_cnt);
    PRINT_DEBUG("regenerating event_fds and fd_info_lookup...\n");
    drakvuf_event_fd_generate(drakvuf);
    return 1;
}

static void drakvuf_event_fd_generate(drakvuf_t drakvuf)
{
    /* event_fds and fd_info_lookup are both generated based off of
       drakvuf->event_fd_info */
    if (drakvuf->event_fds != NULL)
    {
        PRINT_DEBUG("freeing existing event_fds\n");
        g_free(drakvuf->event_fds);
    }
    if (drakvuf->fd_info_lookup != NULL)
    {
        PRINT_DEBUG("freeing existing fd_info_lookup\n");
        g_free(drakvuf->fd_info_lookup);
    }
 
    /* allocate and populate new pollfd array and new fd_info_lookup array */
    drakvuf->event_fds = (struct pollfd*) g_try_malloc0(sizeof(struct pollfd) * \
            (g_slist_length(drakvuf->event_fd_info)));
 
    drakvuf->fd_info_lookup = (fd_info_t) g_try_malloc0(sizeof(struct fd_info) * \
            (g_slist_length(drakvuf->event_fd_info)));
 
    int i = 0;
    GSList* loop = drakvuf->event_fd_info;
    while (loop)
    {
        fd_info_t fd_info = (fd_info_t) loop->data;
        drakvuf->event_fds[i].fd = fd_info->fd;
        drakvuf->event_fds[i].events = POLLIN | POLLERR;
        PRINT_DEBUG("new event_fd i=%d for fd=%d\n", i, fd_info->fd);
 
        drakvuf->fd_info_lookup[i].fd = fd_info->fd;
        drakvuf->fd_info_lookup[i].event_cb = fd_info->event_cb;
        drakvuf->fd_info_lookup[i].data = fd_info->data;
        PRINT_DEBUG("new fd_info_lookup i=%d for fd=%d\n", i, fd_info->fd);
 
        loop = loop->next;
        i++;
    }
 
    return;
}

The events are consumed and the callback is executed in a loop, the main loop of drakvuf application:

void drakvuf_loop(drakvuf_t drakvuf, bool (*is_interrupted)(drakvuf_t, void*), void* data)
{
 
    PRINT_DEBUG("Started DRAKVUF polling loop\n");
 
    drakvuf->interrupted = 0;
    drakvuf_force_resume(drakvuf);
 
    while (!is_interrupted(drakvuf, data))
        drakvuf_poll(drakvuf, 1000);
 
    vmi_pause_vm(drakvuf->vmi);
 
    // Ensures all events are processed from the ring
    drakvuf_poll(drakvuf, 0);
 
    PRINT_DEBUG("DRAKVUF polling loop finished\n");
}

static void drakvuf_poll(drakvuf_t drakvuf, unsigned int timeout)
{
    int rc = poll(drakvuf->event_fds, drakvuf->event_fd_cnt, timeout);
    drakvuf->poll_rc = rc;
 
    if (!rc && timeout)
        return;
 
    else if (rc < 0)
    {
        PRINT_DEBUG("DRAKVUF loop broke unexpectedly: [Errno: %d] %s\n", errno, strerror(errno));
        if (errno != EINTR)
        {
            drakvuf->interrupted = -1;
        }
        return;
    }
 
    /* check and process each fd if it was raised */
    for (int poll_ix=0; poll_ix<drakvuf->event_fd_cnt; poll_ix++)
    {
        if (timeout && !(drakvuf->event_fds[poll_ix].revents & (POLLIN | POLLERR)) )
            continue;
 
        fd_info_t fd_info = &drakvuf->fd_info_lookup[poll_ix];
        fd_info->event_cb(fd_info->fd, fd_info->data);
    }
}

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