UBUNTU: Ubuntu-4.15.0-96.97

[mirror_ubuntu-bionic-kernel.git] / drivers / s390 / char / vmlogrdr.c

// SPDX-License-Identifier: GPL-2.0
/*
 *      character device driver for reading z/VM system service records
 *
 *
 *      Copyright IBM Corp. 2004, 2009
 *      character device driver for reading z/VM system service records,
 *      Version 1.0
 *      Author(s): Xenia Tkatschow <xenia@us.ibm.com>
 *                 Stefan Weinhuber <wein@de.ibm.com>
 *
 */

#define KMSG_COMPONENT "vmlogrdr"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
#include <linux/uaccess.h>
#include <asm/cpcmd.h>
#include <asm/debug.h>
#include <asm/ebcdic.h>
#include <net/iucv/iucv.h>
#include <linux/kmod.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/string.h>

MODULE_AUTHOR
        ("(C) 2004 IBM Corporation by Xenia Tkatschow (xenia@us.ibm.com)\n"
         "                            Stefan Weinhuber (wein@de.ibm.com)");
MODULE_DESCRIPTION ("Character device driver for reading z/VM "
                    "system service records.");
MODULE_LICENSE("GPL");


/*
 * The size of the buffer for iucv data transfer is one page,
 * but in addition to the data we read from iucv we also
 * place an integer and some characters into that buffer,
 * so the maximum size for record data is a little less then
 * one page.
 */
#define NET_BUFFER_SIZE (PAGE_SIZE - sizeof(int) - sizeof(FENCE))

/*
 * The elements that are concurrently accessed by bottom halves are
 * connection_established, iucv_path_severed, local_interrupt_buffer
 * and receive_ready. The first three can be protected by
 * priv_lock.  receive_ready is atomic, so it can be incremented and
 * decremented without holding a lock.
 * The variable dev_in_use needs to be protected by the lock, since
 * it's a flag used by open to make sure that the device is opened only
 * by one user at the same time.
 */
struct vmlogrdr_priv_t {
        char system_service[8];
        char internal_name[8];
        char recording_name[8];
        struct iucv_path *path;
        int connection_established;
        int iucv_path_severed;
        struct iucv_message local_interrupt_buffer;
        atomic_t receive_ready;
        int minor_num;
        char * buffer;
        char * current_position;
        int remaining;
        ulong residual_length;
        int buffer_free;
        int dev_in_use; /* 1: already opened, 0: not opened*/
        spinlock_t priv_lock;
        struct device  *device;
        struct device  *class_device;
        int autorecording;
        int autopurge;
};


/*
 * File operation structure for vmlogrdr devices
 */
static int vmlogrdr_open(struct inode *, struct file *);
static int vmlogrdr_release(struct inode *, struct file *);
static ssize_t vmlogrdr_read (struct file *filp, char __user *data,
                              size_t count, loff_t * ppos);

static const struct file_operations vmlogrdr_fops = {
        .owner   = THIS_MODULE,
        .open    = vmlogrdr_open,
        .release = vmlogrdr_release,
        .read    = vmlogrdr_read,
        .llseek  = no_llseek,
};


static void vmlogrdr_iucv_path_complete(struct iucv_path *, u8 *ipuser);
static void vmlogrdr_iucv_path_severed(struct iucv_path *, u8 *ipuser);
static void vmlogrdr_iucv_message_pending(struct iucv_path *,
                                          struct iucv_message *);


static struct iucv_handler vmlogrdr_iucv_handler = {
        .path_complete   = vmlogrdr_iucv_path_complete,
        .path_severed    = vmlogrdr_iucv_path_severed,
        .message_pending = vmlogrdr_iucv_message_pending,
};


static DECLARE_WAIT_QUEUE_HEAD(conn_wait_queue);
static DECLARE_WAIT_QUEUE_HEAD(read_wait_queue);

/*
 * pointer to system service private structure
 * minor number 0 --> logrec
 * minor number 1 --> account
 * minor number 2 --> symptom
 */

static struct vmlogrdr_priv_t sys_ser[] = {
        { .system_service = "*LOGREC ",
          .internal_name  = "logrec",
          .recording_name = "EREP",
          .minor_num      = 0,
          .buffer_free    = 1,
          .priv_lock      = __SPIN_LOCK_UNLOCKED(sys_ser[0].priv_lock),
          .autorecording  = 1,
          .autopurge      = 1,
        },
        { .system_service = "*ACCOUNT",
          .internal_name  = "account",
          .recording_name = "ACCOUNT",
          .minor_num      = 1,
          .buffer_free    = 1,
          .priv_lock      = __SPIN_LOCK_UNLOCKED(sys_ser[1].priv_lock),
          .autorecording  = 1,
          .autopurge      = 1,
        },
        { .system_service = "*SYMPTOM",
          .internal_name  = "symptom",
          .recording_name = "SYMPTOM",
          .minor_num      = 2,
          .buffer_free    = 1,
          .priv_lock      = __SPIN_LOCK_UNLOCKED(sys_ser[2].priv_lock),
          .autorecording  = 1,
          .autopurge      = 1,
        }
};

#define MAXMINOR  (sizeof(sys_ser)/sizeof(struct vmlogrdr_priv_t))

static char FENCE[] = {"EOR"};
static int vmlogrdr_major = 0;
static struct cdev  *vmlogrdr_cdev = NULL;
static int recording_class_AB;


static void vmlogrdr_iucv_path_complete(struct iucv_path *path, u8 *ipuser)
{
        struct vmlogrdr_priv_t * logptr = path->private;

        spin_lock(&logptr->priv_lock);
        logptr->connection_established = 1;
        spin_unlock(&logptr->priv_lock);
        wake_up(&conn_wait_queue);
}


static void vmlogrdr_iucv_path_severed(struct iucv_path *path, u8 *ipuser)
{
        struct vmlogrdr_priv_t * logptr = path->private;
        u8 reason = (u8) ipuser[8];

        pr_err("vmlogrdr: connection severed with reason %i\n", reason);

        iucv_path_sever(path, NULL);
        kfree(path);
        logptr->path = NULL;

        spin_lock(&logptr->priv_lock);
        logptr->connection_established = 0;
        logptr->iucv_path_severed = 1;
        spin_unlock(&logptr->priv_lock);

        wake_up(&conn_wait_queue);
        /* just in case we're sleeping waiting for a record */
        wake_up_interruptible(&read_wait_queue);
}


static void vmlogrdr_iucv_message_pending(struct iucv_path *path,
                                          struct iucv_message *msg)
{
        struct vmlogrdr_priv_t * logptr = path->private;

        /*
         * This function is the bottom half so it should be quick.
         * Copy the external interrupt data into our local eib and increment
         * the usage count
         */
        spin_lock(&logptr->priv_lock);
        memcpy(&logptr->local_interrupt_buffer, msg, sizeof(*msg));
        atomic_inc(&logptr->receive_ready);
        spin_unlock(&logptr->priv_lock);
        wake_up_interruptible(&read_wait_queue);
}


static int vmlogrdr_get_recording_class_AB(void)
{
        static const char cp_command[] = "QUERY COMMAND RECORDING ";
        char cp_response[80];
        char *tail;
        int len,i;

        cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);
        len = strnlen(cp_response,sizeof(cp_response));
        // now the parsing
        tail=strnchr(cp_response,len,'=');
        if (!tail)
                return 0;
        tail++;
        if (!strncmp("ANY",tail,3))
                return 1;
        if (!strncmp("NONE",tail,4))
                return 0;
        /*
         * expect comma separated list of classes here, if one of them
         * is A or B return 1 otherwise 0
         */
        for (i=tail-cp_response; i<len; i++)
                if ( cp_response[i]=='A' || cp_response[i]=='B' )
                        return 1;
        return 0;
}


static int vmlogrdr_recording(struct vmlogrdr_priv_t * logptr,
                              int action, int purge)
{

        char cp_command[80];
        char cp_response[160];
        char *onoff, *qid_string;
        int rc;

        onoff = ((action == 1) ? "ON" : "OFF");
        qid_string = ((recording_class_AB == 1) ? " QID * " : "");

        /*
         * The recording commands needs to be called with option QID
         * for guests that have previlege classes A or B.
         * Purging has to be done as separate step, because recording
         * can't be switched on as long as records are on the queue.
         * Doing both at the same time doesn't work.
         */
        if (purge && (action == 1)) {
                memset(cp_command, 0x00, sizeof(cp_command));
                memset(cp_response, 0x00, sizeof(cp_response));
                snprintf(cp_command, sizeof(cp_command),
                         "RECORDING %s PURGE %s",
                         logptr->recording_name,
                         qid_string);
                cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);
        }

        memset(cp_command, 0x00, sizeof(cp_command));
        memset(cp_response, 0x00, sizeof(cp_response));
        snprintf(cp_command, sizeof(cp_command), "RECORDING %s %s %s",
                logptr->recording_name,
                onoff,
                qid_string);
        cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);
        /* The recording command will usually answer with 'Command complete'
         * on success, but when the specific service was never connected
         * before then there might be an additional informational message
         * 'HCPCRC8072I Recording entry not found' before the
         * 'Command complete'. So I use strstr rather then the strncmp.
         */
        if (strstr(cp_response,"Command complete"))
                rc = 0;
        else
                rc = -EIO;
        /*
         * If we turn recording off, we have to purge any remaining records
         * afterwards, as a large number of queued records may impact z/VM
         * performance.
         */
        if (purge && (action == 0)) {
                memset(cp_command, 0x00, sizeof(cp_command));
                memset(cp_response, 0x00, sizeof(cp_response));
                snprintf(cp_command, sizeof(cp_command),
                         "RECORDING %s PURGE %s",
                         logptr->recording_name,
                         qid_string);
                cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);
        }

        return rc;
}


static int vmlogrdr_open (struct inode *inode, struct file *filp)
{
        int dev_num = 0;
        struct vmlogrdr_priv_t * logptr = NULL;
        int connect_rc = 0;
        int ret;

        dev_num = iminor(inode);
        if (dev_num >= MAXMINOR)
                return -ENODEV;
        logptr = &sys_ser[dev_num];

        /*
         * only allow for blocking reads to be open
         */
        if (filp->f_flags & O_NONBLOCK)
                return -EOPNOTSUPP;

        /* Besure this device hasn't already been opened */
        spin_lock_bh(&logptr->priv_lock);
        if (logptr->dev_in_use) {
                spin_unlock_bh(&logptr->priv_lock);
                return -EBUSY;
        }
        logptr->dev_in_use = 1;
        logptr->connection_established = 0;
        logptr->iucv_path_severed = 0;
        atomic_set(&logptr->receive_ready, 0);
        logptr->buffer_free = 1;
        spin_unlock_bh(&logptr->priv_lock);

        /* set the file options */
        filp->private_data = logptr;

        /* start recording for this service*/
        if (logptr->autorecording) {
                ret = vmlogrdr_recording(logptr,1,logptr->autopurge);
                if (ret)
                        pr_warn("vmlogrdr: failed to start recording automatically\n");
        }

        /* create connection to the system service */
        logptr->path = iucv_path_alloc(10, 0, GFP_KERNEL);
        if (!logptr->path)
                goto out_dev;
        connect_rc = iucv_path_connect(logptr->path, &vmlogrdr_iucv_handler,
                                       logptr->system_service, NULL, NULL,
                                       logptr);
        if (connect_rc) {
                pr_err("vmlogrdr: iucv connection to %s "
                       "failed with rc %i \n",
                       logptr->system_service, connect_rc);
                goto out_path;
        }

        /* We've issued the connect and now we must wait for a
         * ConnectionComplete or ConnectinSevered Interrupt
         * before we can continue to process.
         */
        wait_event(conn_wait_queue, (logptr->connection_established)
                   || (logptr->iucv_path_severed));
        if (logptr->iucv_path_severed)
                goto out_record;
        nonseekable_open(inode, filp);
        return 0;

out_record:
        if (logptr->autorecording)
                vmlogrdr_recording(logptr,0,logptr->autopurge);
out_path:
        kfree(logptr->path);    /* kfree(NULL) is ok. */
        logptr->path = NULL;
out_dev:
        logptr->dev_in_use = 0;
        return -EIO;
}


static int vmlogrdr_release (struct inode *inode, struct file *filp)
{
        int ret;

        struct vmlogrdr_priv_t * logptr = filp->private_data;

        iucv_path_sever(logptr->path, NULL);
        kfree(logptr->path);
        logptr->path = NULL;
        if (logptr->autorecording) {
                ret = vmlogrdr_recording(logptr,0,logptr->autopurge);
                if (ret)
                        pr_warn("vmlogrdr: failed to stop recording automatically\n");
        }
        logptr->dev_in_use = 0;

        return 0;
}


static int vmlogrdr_receive_data(struct vmlogrdr_priv_t *priv)
{
        int rc, *temp;
        /* we need to keep track of two data sizes here:
         * The number of bytes we need to receive from iucv and
         * the total number of bytes we actually write into the buffer.
         */
        int user_data_count, iucv_data_count;
        char * buffer;

        if (atomic_read(&priv->receive_ready)) {
                spin_lock_bh(&priv->priv_lock);
                if (priv->residual_length){
                        /* receive second half of a record */
                        iucv_data_count = priv->residual_length;
                        user_data_count = 0;
                        buffer = priv->buffer;
                } else {
                        /* receive a new record:
                         * We need to return the total length of the record
                         * + size of FENCE in the first 4 bytes of the buffer.
                         */
                        iucv_data_count = priv->local_interrupt_buffer.length;
                        user_data_count = sizeof(int);
                        temp = (int*)priv->buffer;
                        *temp= iucv_data_count + sizeof(FENCE);
                        buffer = priv->buffer + sizeof(int);
                }
                /*
                 * If the record is bigger than our buffer, we receive only
                 * a part of it. We can get the rest later.
                 */
                if (iucv_data_count > NET_BUFFER_SIZE)
                        iucv_data_count = NET_BUFFER_SIZE;
                rc = iucv_message_receive(priv->path,
                                          &priv->local_interrupt_buffer,
                                          0, buffer, iucv_data_count,
                                          &priv->residual_length);
                spin_unlock_bh(&priv->priv_lock);
                /* An rc of 5 indicates that the record was bigger than
                 * the buffer, which is OK for us. A 9 indicates that the
                 * record was purged befor we could receive it.
                 */
                if (rc == 5)
                        rc = 0;
                if (rc == 9)
                        atomic_set(&priv->receive_ready, 0);
        } else {
                rc = 1;
        }
        if (!rc) {
                priv->buffer_free = 0;
                user_data_count += iucv_data_count;
                priv->current_position = priv->buffer;
                if (priv->residual_length == 0){
                        /* the whole record has been captured,
                         * now add the fence */
                        atomic_dec(&priv->receive_ready);
                        buffer = priv->buffer + user_data_count;
                        memcpy(buffer, FENCE, sizeof(FENCE));
                        user_data_count += sizeof(FENCE);
                }
                priv->remaining = user_data_count;
        }

        return rc;
}


static ssize_t vmlogrdr_read(struct file *filp, char __user *data,
                             size_t count, loff_t * ppos)
{
        int rc;
        struct vmlogrdr_priv_t * priv = filp->private_data;

        while (priv->buffer_free) {
                rc = vmlogrdr_receive_data(priv);
                if (rc) {
                        rc = wait_event_interruptible(read_wait_queue,
                                        atomic_read(&priv->receive_ready));
                        if (rc)
                                return rc;
                }
        }
        /* copy only up to end of record */
        if (count > priv->remaining)
                count = priv->remaining;

        if (copy_to_user(data, priv->current_position, count))
                return -EFAULT;

        *ppos += count;
        priv->current_position += count;
        priv->remaining -= count;

        /* if all data has been transferred, set buffer free */
        if (priv->remaining == 0)
                priv->buffer_free = 1;

        return count;
}

static ssize_t vmlogrdr_autopurge_store(struct device * dev,
                                        struct device_attribute *attr,
                                        const char * buf, size_t count)
{
        struct vmlogrdr_priv_t *priv = dev_get_drvdata(dev);
        ssize_t ret = count;

        switch (buf[0]) {
        case '0':
                priv->autopurge=0;
                break;
        case '1':
                priv->autopurge=1;
                break;
        default:
                ret = -EINVAL;
        }
        return ret;
}


static ssize_t vmlogrdr_autopurge_show(struct device *dev,
                                       struct device_attribute *attr,
                                       char *buf)
{
        struct vmlogrdr_priv_t *priv = dev_get_drvdata(dev);
        return sprintf(buf, "%u\n", priv->autopurge);
}


static DEVICE_ATTR(autopurge, 0644, vmlogrdr_autopurge_show,
                   vmlogrdr_autopurge_store);


static ssize_t vmlogrdr_purge_store(struct device * dev,
                                    struct device_attribute *attr,
                                    const char * buf, size_t count)
{

        char cp_command[80];
        char cp_response[80];
        struct vmlogrdr_priv_t *priv = dev_get_drvdata(dev);

        if (buf[0] != '1')
                return -EINVAL;

        memset(cp_command, 0x00, sizeof(cp_command));
        memset(cp_response, 0x00, sizeof(cp_response));

        /*
         * The recording command needs to be called with option QID
         * for guests that have previlege classes A or B.
         * Other guests will not recognize the command and we have to
         * issue the same command without the QID parameter.
         */

        if (recording_class_AB)
                snprintf(cp_command, sizeof(cp_command),
                         "RECORDING %s PURGE QID * ",
                         priv->recording_name);
        else
                snprintf(cp_command, sizeof(cp_command),
                         "RECORDING %s PURGE ",
                         priv->recording_name);

        cpcmd(cp_command, cp_response, sizeof(cp_response), NULL);

        return count;
}


static DEVICE_ATTR(purge, 0200, NULL, vmlogrdr_purge_store);


static ssize_t vmlogrdr_autorecording_store(struct device *dev,
                                            struct device_attribute *attr,
                                            const char *buf, size_t count)
{
        struct vmlogrdr_priv_t *priv = dev_get_drvdata(dev);
        ssize_t ret = count;

        switch (buf[0]) {
        case '0':
                priv->autorecording=0;
                break;
        case '1':
                priv->autorecording=1;
                break;
        default:
                ret = -EINVAL;
        }
        return ret;
}


static ssize_t vmlogrdr_autorecording_show(struct device *dev,
                                           struct device_attribute *attr,
                                           char *buf)
{
        struct vmlogrdr_priv_t *priv = dev_get_drvdata(dev);
        return sprintf(buf, "%u\n", priv->autorecording);
}


static DEVICE_ATTR(autorecording, 0644, vmlogrdr_autorecording_show,
                   vmlogrdr_autorecording_store);


static ssize_t vmlogrdr_recording_store(struct device * dev,
                                        struct device_attribute *attr,
                                        const char * buf, size_t count)
{
        struct vmlogrdr_priv_t *priv = dev_get_drvdata(dev);
        ssize_t ret;

        switch (buf[0]) {
        case '0':
                ret = vmlogrdr_recording(priv,0,0);
                break;
        case '1':
                ret = vmlogrdr_recording(priv,1,0);
                break;
        default:
                ret = -EINVAL;
        }
        if (ret)
                return ret;
        else
                return count;

}


static DEVICE_ATTR(recording, 0200, NULL, vmlogrdr_recording_store);


static ssize_t recording_status_show(struct device_driver *driver, char *buf)
{
        static const char cp_command[] = "QUERY RECORDING ";
        int len;

        cpcmd(cp_command, buf, 4096, NULL);
        len = strlen(buf);
        return len;
}
static DRIVER_ATTR_RO(recording_status);
static struct attribute *vmlogrdr_drv_attrs[] = {
        &driver_attr_recording_status.attr,
        NULL,
};
static struct attribute_group vmlogrdr_drv_attr_group = {
        .attrs = vmlogrdr_drv_attrs,
};
static const struct attribute_group *vmlogrdr_drv_attr_groups[] = {
        &vmlogrdr_drv_attr_group,
        NULL,
};

static struct attribute *vmlogrdr_attrs[] = {
        &dev_attr_autopurge.attr,
        &dev_attr_purge.attr,
        &dev_attr_autorecording.attr,
        &dev_attr_recording.attr,
        NULL,
};
static struct attribute_group vmlogrdr_attr_group = {
        .attrs = vmlogrdr_attrs,
};
static const struct attribute_group *vmlogrdr_attr_groups[] = {
        &vmlogrdr_attr_group,
        NULL,
};

static int vmlogrdr_pm_prepare(struct device *dev)
{
        int rc;
        struct vmlogrdr_priv_t *priv = dev_get_drvdata(dev);

        rc = 0;
        if (priv) {
                spin_lock_bh(&priv->priv_lock);
                if (priv->dev_in_use)
                        rc = -EBUSY;
                spin_unlock_bh(&priv->priv_lock);
        }
        if (rc)
                pr_err("vmlogrdr: device %s is busy. Refuse to suspend.\n",
                       dev_name(dev));
        return rc;
}


static const struct dev_pm_ops vmlogrdr_pm_ops = {
        .prepare = vmlogrdr_pm_prepare,
};

static struct class *vmlogrdr_class;
static struct device_driver vmlogrdr_driver = {
        .name = "vmlogrdr",
        .bus  = &iucv_bus,
        .pm = &vmlogrdr_pm_ops,
        .groups = vmlogrdr_drv_attr_groups,
};

static int vmlogrdr_register_driver(void)
{
        int ret;

        /* Register with iucv driver */
        ret = iucv_register(&vmlogrdr_iucv_handler, 1);
        if (ret)
                goto out;

        ret = driver_register(&vmlogrdr_driver);
        if (ret)
                goto out_iucv;

        vmlogrdr_class = class_create(THIS_MODULE, "vmlogrdr");
        if (IS_ERR(vmlogrdr_class)) {
                ret = PTR_ERR(vmlogrdr_class);
                vmlogrdr_class = NULL;
                goto out_driver;
        }
        return 0;

out_driver:
        driver_unregister(&vmlogrdr_driver);
out_iucv:
        iucv_unregister(&vmlogrdr_iucv_handler, 1);
out:
        return ret;
}


static void vmlogrdr_unregister_driver(void)
{
        class_destroy(vmlogrdr_class);
        vmlogrdr_class = NULL;
        driver_unregister(&vmlogrdr_driver);
        iucv_unregister(&vmlogrdr_iucv_handler, 1);
}


static int vmlogrdr_register_device(struct vmlogrdr_priv_t *priv)
{
        struct device *dev;
        int ret;

        dev = kzalloc(sizeof(struct device), GFP_KERNEL);
        if (dev) {
                dev_set_name(dev, "%s", priv->internal_name);
                dev->bus = &iucv_bus;
                dev->parent = iucv_root;
                dev->driver = &vmlogrdr_driver;
                dev->groups = vmlogrdr_attr_groups;
                dev_set_drvdata(dev, priv);
                /*
                 * The release function could be called after the
                 * module has been unloaded. It's _only_ task is to
                 * free the struct. Therefore, we specify kfree()
                 * directly here. (Probably a little bit obfuscating
                 * but legitime ...).
                 */
                dev->release = (void (*)(struct device *))kfree;
        } else
                return -ENOMEM;
        ret = device_register(dev);
        if (ret) {
                put_device(dev);
                return ret;
        }

        priv->class_device = device_create(vmlogrdr_class, dev,
                                           MKDEV(vmlogrdr_major,
                                                 priv->minor_num),
                                           priv, "%s", dev_name(dev));
        if (IS_ERR(priv->class_device)) {
                ret = PTR_ERR(priv->class_device);
                priv->class_device=NULL;
                device_unregister(dev);
                return ret;
        }
        priv->device = dev;
        return 0;
}


static int vmlogrdr_unregister_device(struct vmlogrdr_priv_t *priv)
{
        device_destroy(vmlogrdr_class, MKDEV(vmlogrdr_major, priv->minor_num));
        if (priv->device != NULL) {
                device_unregister(priv->device);
                priv->device=NULL;
        }
        return 0;
}


static int vmlogrdr_register_cdev(dev_t dev)
{
        int rc = 0;
        vmlogrdr_cdev = cdev_alloc();
        if (!vmlogrdr_cdev) {
                return -ENOMEM;
        }
        vmlogrdr_cdev->owner = THIS_MODULE;
        vmlogrdr_cdev->ops = &vmlogrdr_fops;
        rc = cdev_add(vmlogrdr_cdev, dev, MAXMINOR);
        if (!rc)
                return 0;

        // cleanup: cdev is not fully registered, no cdev_del here!
        kobject_put(&vmlogrdr_cdev->kobj);
        vmlogrdr_cdev=NULL;
        return rc;
}


static void vmlogrdr_cleanup(void)
{
        int i;

        if (vmlogrdr_cdev) {
                cdev_del(vmlogrdr_cdev);
                vmlogrdr_cdev=NULL;
        }
        for (i=0; i < MAXMINOR; ++i ) {
                vmlogrdr_unregister_device(&sys_ser[i]);
                free_page((unsigned long)sys_ser[i].buffer);
        }
        vmlogrdr_unregister_driver();
        if (vmlogrdr_major) {
                unregister_chrdev_region(MKDEV(vmlogrdr_major, 0), MAXMINOR);
                vmlogrdr_major=0;
        }
}


static int __init vmlogrdr_init(void)
{
        int rc;
        int i;
        dev_t dev;

        if (! MACHINE_IS_VM) {
                pr_err("not running under VM, driver not loaded.\n");
                return -ENODEV;
        }

        recording_class_AB = vmlogrdr_get_recording_class_AB();

        rc = alloc_chrdev_region(&dev, 0, MAXMINOR, "vmlogrdr");
        if (rc)
                return rc;
        vmlogrdr_major = MAJOR(dev);

        rc=vmlogrdr_register_driver();
        if (rc)
                goto cleanup;

        for (i=0; i < MAXMINOR; ++i ) {
                sys_ser[i].buffer = (char *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
                if (!sys_ser[i].buffer) {
                        rc = -ENOMEM;
                        break;
                }
                sys_ser[i].current_position = sys_ser[i].buffer;
                rc=vmlogrdr_register_device(&sys_ser[i]);
                if (rc)
                        break;
        }
        if (rc)
                goto cleanup;

        rc = vmlogrdr_register_cdev(dev);
        if (rc)
                goto cleanup;
        return 0;

cleanup:
        vmlogrdr_cleanup();
        return rc;
}


static void __exit vmlogrdr_exit(void)
{
        vmlogrdr_cleanup();
        return;
}


module_init(vmlogrdr_init);
module_exit(vmlogrdr_exit);