monreader.c

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/*
 * Character device driver for reading z/VM *MONITOR service records.
 *
 * Copyright IBM Corp. 2004, 2009
 *
 * Author: Gerald Schaefer <[email protected]>
 */

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

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/ctype.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/poll.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <net/iucv/iucv.h>
#include <asm/uaccess.h>
#include <asm/ebcdic.h>
#include <asm/extmem.h>


#define MON_COLLECT_SAMPLE 0x80
#define MON_COLLECT_EVENT  0x40
#define MON_SERVICE    "*MONITOR"
#define MON_IN_USE     0x01
#define MON_MSGLIM     255

static char mon_dcss_name[9] = "MONDCSS\0";

struct mon_msg {
    u32 pos;
    u32 mca_offset;
    struct iucv_message msg;
    char msglim_reached;
    char replied_msglim;
};

struct mon_private {
    struct iucv_path *path;
    struct mon_msg *msg_array[MON_MSGLIM];
    unsigned int   write_index;
    unsigned int   read_index;
    atomic_t msglim_count;
    atomic_t read_ready;
    atomic_t iucv_connected;
    atomic_t iucv_severed;
};

static unsigned long mon_in_use = 0;

static unsigned long mon_dcss_start;
static unsigned long mon_dcss_end;

static DECLARE_WAIT_QUEUE_HEAD(mon_read_wait_queue);
static DECLARE_WAIT_QUEUE_HEAD(mon_conn_wait_queue);

static u8 user_data_connect[16] = {
    /* Version code, must be 0x01 for shared mode */
    0x01,
    /* what to collect */
    MON_COLLECT_SAMPLE | MON_COLLECT_EVENT,
    /* DCSS name in EBCDIC, 8 bytes padded with blanks */
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
};

static u8 user_data_sever[16] = {
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
};

static struct device *monreader_device;

/******************************************************************************
 *                             helper functions                               *
 *****************************************************************************/
/*
 * Create the 8 bytes EBCDIC DCSS segment name from
 * an ASCII name, incl. padding
 */
static void dcss_mkname(char *ascii_name, char *ebcdic_name)
{
    int i;

    for (i = 0; i < 8; i++) {
        if (ascii_name[i] == '\0')
            break;
        ebcdic_name[i] = toupper(ascii_name[i]);
    };
    for (; i < 8; i++)
        ebcdic_name[i] = ' ';
    ASCEBC(ebcdic_name, 8);
}

static inline unsigned long mon_mca_start(struct mon_msg *monmsg)
{
    return *(u32 *) &monmsg->msg.rmmsg;
}

static inline unsigned long mon_mca_end(struct mon_msg *monmsg)
{
    return *(u32 *) &monmsg->msg.rmmsg[4];
}

static inline u8 mon_mca_type(struct mon_msg *monmsg, u8 index)
{
    return *((u8 *) mon_mca_start(monmsg) + monmsg->mca_offset + index);
}

static inline u32 mon_mca_size(struct mon_msg *monmsg)
{
    return mon_mca_end(monmsg) - mon_mca_start(monmsg) + 1;
}

static inline u32 mon_rec_start(struct mon_msg *monmsg)
{
    return *((u32 *) (mon_mca_start(monmsg) + monmsg->mca_offset + 4));
}

static inline u32 mon_rec_end(struct mon_msg *monmsg)
{
    return *((u32 *) (mon_mca_start(monmsg) + monmsg->mca_offset + 8));
}

static int mon_check_mca(struct mon_msg *monmsg)
{
    if ((mon_rec_end(monmsg) <= mon_rec_start(monmsg)) ||
        (mon_rec_start(monmsg) < mon_dcss_start) ||
        (mon_rec_end(monmsg) > mon_dcss_end) ||
        (mon_mca_type(monmsg, 0) == 0) ||
        (mon_mca_size(monmsg) % 12 != 0) ||
        (mon_mca_end(monmsg) <= mon_mca_start(monmsg)) ||
        (mon_mca_end(monmsg) > mon_dcss_end) ||
        (mon_mca_start(monmsg) < mon_dcss_start) ||
        ((mon_mca_type(monmsg, 1) == 0) && (mon_mca_type(monmsg, 2) == 0)))
        return -EINVAL;
    return 0;
}

static int mon_send_reply(struct mon_msg *monmsg,
              struct mon_private *monpriv)
{
    int rc;

    rc = iucv_message_reply(monpriv->path, &monmsg->msg,
                IUCV_IPRMDATA, NULL, 0);
    atomic_dec(&monpriv->msglim_count);
    if (likely(!monmsg->msglim_reached)) {
        monmsg->pos = 0;
        monmsg->mca_offset = 0;
        monpriv->read_index = (monpriv->read_index + 1) %
                      MON_MSGLIM;
        atomic_dec(&monpriv->read_ready);
    } else
        monmsg->replied_msglim = 1;
    if (rc) {
        pr_err("Reading monitor data failed with rc=%i\n", rc);
        return -EIO;
    }
    return 0;
}

static void mon_free_mem(struct mon_private *monpriv)
{
    int i;

    for (i = 0; i < MON_MSGLIM; i++)
        if (monpriv->msg_array[i])
            kfree(monpriv->msg_array[i]);
    kfree(monpriv);
}

static struct mon_private *mon_alloc_mem(void)
{
    int i;
    struct mon_private *monpriv;

    monpriv = kzalloc(sizeof(struct mon_private), GFP_KERNEL);
    if (!monpriv)
        return NULL;
    for (i = 0; i < MON_MSGLIM; i++) {
        monpriv->msg_array[i] = kzalloc(sizeof(struct mon_msg),
                            GFP_KERNEL);
        if (!monpriv->msg_array[i]) {
            mon_free_mem(monpriv);
            return NULL;
        }
    }
    return monpriv;
}

static inline void mon_next_mca(struct mon_msg *monmsg)
{
    if (likely((mon_mca_size(monmsg) - monmsg->mca_offset) == 12))
        return;
    monmsg->mca_offset += 12;
    monmsg->pos = 0;
}

static struct mon_msg *mon_next_message(struct mon_private *monpriv)
{
    struct mon_msg *monmsg;

    if (!atomic_read(&monpriv->read_ready))
        return NULL;
    monmsg = monpriv->msg_array[monpriv->read_index];
    if (unlikely(monmsg->replied_msglim)) {
        monmsg->replied_msglim = 0;
        monmsg->msglim_reached = 0;
        monmsg->pos = 0;
        monmsg->mca_offset = 0;
        monpriv->read_index = (monpriv->read_index + 1) %
                      MON_MSGLIM;
        atomic_dec(&monpriv->read_ready);
        return ERR_PTR(-EOVERFLOW);
    }
    return monmsg;
}


/******************************************************************************
 *                               IUCV handler                                 *
 *****************************************************************************/
static void mon_iucv_path_complete(struct iucv_path *path, u8 ipuser[16])
{
    struct mon_private *monpriv = path->private;

    atomic_set(&monpriv->iucv_connected, 1);
    wake_up(&mon_conn_wait_queue);
}

static void mon_iucv_path_severed(struct iucv_path *path, u8 ipuser[16])
{
    struct mon_private *monpriv = path->private;

    pr_err("z/VM *MONITOR system service disconnected with rc=%i\n",
           ipuser[0]);
    iucv_path_sever(path, NULL);
    atomic_set(&monpriv->iucv_severed, 1);
    wake_up(&mon_conn_wait_queue);
    wake_up_interruptible(&mon_read_wait_queue);
}

static void mon_iucv_message_pending(struct iucv_path *path,
                     struct iucv_message *msg)
{
    struct mon_private *monpriv = path->private;

    memcpy(&monpriv->msg_array[monpriv->write_index]->msg,
           msg, sizeof(*msg));
    if (atomic_inc_return(&monpriv->msglim_count) == MON_MSGLIM) {
        pr_warning("The read queue for monitor data is full\n");
        monpriv->msg_array[monpriv->write_index]->msglim_reached = 1;
    }
    monpriv->write_index = (monpriv->write_index + 1) % MON_MSGLIM;
    atomic_inc(&monpriv->read_ready);
    wake_up_interruptible(&mon_read_wait_queue);
}

static struct iucv_handler monreader_iucv_handler = {
    .path_complete   = mon_iucv_path_complete,
    .path_severed    = mon_iucv_path_severed,
    .message_pending = mon_iucv_message_pending,
};

/******************************************************************************
 *                               file operations                              *
 *****************************************************************************/
static int mon_open(struct inode *inode, struct file *filp)
{
    struct mon_private *monpriv;
    int rc;

    /*
     * only one user allowed
     */
    rc = -EBUSY;
    if (test_and_set_bit(MON_IN_USE, &mon_in_use))
        goto out;

    rc = -ENOMEM;
    monpriv = mon_alloc_mem();
    if (!monpriv)
        goto out_use;

    /*
     * Connect to *MONITOR service
     */
    monpriv->path = iucv_path_alloc(MON_MSGLIM, IUCV_IPRMDATA, GFP_KERNEL);
    if (!monpriv->path)
        goto out_priv;
    rc = iucv_path_connect(monpriv->path, &monreader_iucv_handler,
                   MON_SERVICE, NULL, user_data_connect, monpriv);
    if (rc) {
        pr_err("Connecting to the z/VM *MONITOR system service "
               "failed with rc=%i\n", rc);
        rc = -EIO;
        goto out_path;
    }
    /*
     * Wait for connection confirmation
     */
    wait_event(mon_conn_wait_queue,
           atomic_read(&monpriv->iucv_connected) ||
           atomic_read(&monpriv->iucv_severed));
    if (atomic_read(&monpriv->iucv_severed)) {
        atomic_set(&monpriv->iucv_severed, 0);
        atomic_set(&monpriv->iucv_connected, 0);
        rc = -EIO;
        goto out_path;
    }
    filp->private_data = monpriv;
    dev_set_drvdata(monreader_device, monpriv);
    return nonseekable_open(inode, filp);

out_path:
    iucv_path_free(monpriv->path);
out_priv:
    mon_free_mem(monpriv);
out_use:
    clear_bit(MON_IN_USE, &mon_in_use);
out:
    return rc;
}

static int mon_close(struct inode *inode, struct file *filp)
{
    int rc, i;
    struct mon_private *monpriv = filp->private_data;

    /*
     * Close IUCV connection and unregister
     */
    if (monpriv->path) {
        rc = iucv_path_sever(monpriv->path, user_data_sever);
        if (rc)
            pr_warning("Disconnecting the z/VM *MONITOR system "
                   "service failed with rc=%i\n", rc);
        iucv_path_free(monpriv->path);
    }

    atomic_set(&monpriv->iucv_severed, 0);
    atomic_set(&monpriv->iucv_connected, 0);
    atomic_set(&monpriv->read_ready, 0);
    atomic_set(&monpriv->msglim_count, 0);
    monpriv->write_index  = 0;
    monpriv->read_index   = 0;
    dev_set_drvdata(monreader_device, NULL);

    for (i = 0; i < MON_MSGLIM; i++)
        kfree(monpriv->msg_array[i]);
    kfree(monpriv);
    clear_bit(MON_IN_USE, &mon_in_use);
    return 0;
}

static ssize_t mon_read(struct file *filp, char __user *data,
            size_t count, loff_t *ppos)
{
    struct mon_private *monpriv = filp->private_data;
    struct mon_msg *monmsg;
    int ret;
    u32 mce_start;

    monmsg = mon_next_message(monpriv);
    if (IS_ERR(monmsg))
        return PTR_ERR(monmsg);

    if (!monmsg) {
        if (filp->f_flags & O_NONBLOCK)
            return -EAGAIN;
        ret = wait_event_interruptible(mon_read_wait_queue,
                    atomic_read(&monpriv->read_ready) ||
                    atomic_read(&monpriv->iucv_severed));
        if (ret)
            return ret;
        if (unlikely(atomic_read(&monpriv->iucv_severed)))
            return -EIO;
        monmsg = monpriv->msg_array[monpriv->read_index];
    }

    if (!monmsg->pos)
        monmsg->pos = mon_mca_start(monmsg) + monmsg->mca_offset;
    if (mon_check_mca(monmsg))
        goto reply;

    /* read monitor control element (12 bytes) first */
    mce_start = mon_mca_start(monmsg) + monmsg->mca_offset;
    if ((monmsg->pos >= mce_start) && (monmsg->pos < mce_start + 12)) {
        count = min(count, (size_t) mce_start + 12 - monmsg->pos);
        ret = copy_to_user(data, (void *) (unsigned long) monmsg->pos,
                   count);
        if (ret)
            return -EFAULT;
        monmsg->pos += count;
        if (monmsg->pos == mce_start + 12)
            monmsg->pos = mon_rec_start(monmsg);
        goto out_copy;
    }

    /* read records */
    if (monmsg->pos <= mon_rec_end(monmsg)) {
        count = min(count, (size_t) mon_rec_end(monmsg) - monmsg->pos
                        + 1);
        ret = copy_to_user(data, (void *) (unsigned long) monmsg->pos,
                   count);
        if (ret)
            return -EFAULT;
        monmsg->pos += count;
        if (monmsg->pos > mon_rec_end(monmsg))
            mon_next_mca(monmsg);
        goto out_copy;
    }
reply:
    ret = mon_send_reply(monmsg, monpriv);
    return ret;

out_copy:
    *ppos += count;
    return count;
}

static unsigned int mon_poll(struct file *filp, struct poll_table_struct *p)
{
    struct mon_private *monpriv = filp->private_data;

    poll_wait(filp, &mon_read_wait_queue, p);
    if (unlikely(atomic_read(&monpriv->iucv_severed)))
        return POLLERR;
    if (atomic_read(&monpriv->read_ready))
        return POLLIN | POLLRDNORM;
    return 0;
}

static const struct file_operations mon_fops = {
    .owner   = THIS_MODULE,
    .open    = &mon_open,
    .release = &mon_close,
    .read    = &mon_read,
    .poll    = &mon_poll,
    .llseek  = noop_llseek,
};

static struct miscdevice mon_dev = {
    .name       = "monreader",
    .fops       = &mon_fops,
    .minor      = MISC_DYNAMIC_MINOR,
};


/******************************************************************************
 *              suspend / resume                  *
 *****************************************************************************/
static int monreader_freeze(struct device *dev)
{
    struct mon_private *monpriv = dev_get_drvdata(dev);
    int rc;

    if (!monpriv)
        return 0;
    if (monpriv->path) {
        rc = iucv_path_sever(monpriv->path, user_data_sever);
        if (rc)
            pr_warning("Disconnecting the z/VM *MONITOR system "
                   "service failed with rc=%i\n", rc);
        iucv_path_free(monpriv->path);
    }
    atomic_set(&monpriv->iucv_severed, 0);
    atomic_set(&monpriv->iucv_connected, 0);
    atomic_set(&monpriv->read_ready, 0);
    atomic_set(&monpriv->msglim_count, 0);
    monpriv->write_index  = 0;
    monpriv->read_index   = 0;
    monpriv->path = NULL;
    return 0;
}

static int monreader_thaw(struct device *dev)
{
    struct mon_private *monpriv = dev_get_drvdata(dev);
    int rc;

    if (!monpriv)
        return 0;
    rc = -ENOMEM;
    monpriv->path = iucv_path_alloc(MON_MSGLIM, IUCV_IPRMDATA, GFP_KERNEL);
    if (!monpriv->path)
        goto out;
    rc = iucv_path_connect(monpriv->path, &monreader_iucv_handler,
                   MON_SERVICE, NULL, user_data_connect, monpriv);
    if (rc) {
        pr_err("Connecting to the z/VM *MONITOR system service "
               "failed with rc=%i\n", rc);
        goto out_path;
    }
    wait_event(mon_conn_wait_queue,
           atomic_read(&monpriv->iucv_connected) ||
           atomic_read(&monpriv->iucv_severed));
    if (atomic_read(&monpriv->iucv_severed))
        goto out_path;
    return 0;
out_path:
    rc = -EIO;
    iucv_path_free(monpriv->path);
    monpriv->path = NULL;
out:
    atomic_set(&monpriv->iucv_severed, 1);
    return rc;
}

static int monreader_restore(struct device *dev)
{
    int rc;

    segment_unload(mon_dcss_name);
    rc = segment_load(mon_dcss_name, SEGMENT_SHARED,
              &mon_dcss_start, &mon_dcss_end);
    if (rc < 0) {
        segment_warning(rc, mon_dcss_name);
        panic("fatal monreader resume error: no monitor dcss\n");
    }
    return monreader_thaw(dev);
}

static const struct dev_pm_ops monreader_pm_ops = {
    .freeze  = monreader_freeze,
    .thaw    = monreader_thaw,
    .restore = monreader_restore,
};

static struct device_driver monreader_driver = {
    .name = "monreader",
    .bus  = &iucv_bus,
    .pm   = &monreader_pm_ops,
};


/******************************************************************************
 *                              module init/exit                              *
 *****************************************************************************/
static int __init mon_init(void)
{
    int rc;

    if (!MACHINE_IS_VM) {
        pr_err("The z/VM *MONITOR record device driver cannot be "
               "loaded without z/VM\n");
        return -ENODEV;
    }

    /*
     * Register with IUCV and connect to *MONITOR service
     */
    rc = iucv_register(&monreader_iucv_handler, 1);
    if (rc) {
        pr_err("The z/VM *MONITOR record device driver failed to "
               "register with IUCV\n");
        return rc;
    }

    rc = driver_register(&monreader_driver);
    if (rc)
        goto out_iucv;
    monreader_device = kzalloc(sizeof(struct device), GFP_KERNEL);
    if (!monreader_device) {
        rc = -ENOMEM;
        goto out_driver;
    }

    dev_set_name(monreader_device, "monreader-dev");
    monreader_device->bus = &iucv_bus;
    monreader_device->parent = iucv_root;
    monreader_device->driver = &monreader_driver;
    monreader_device->release = (void (*)(struct device *))kfree;
    rc = device_register(monreader_device);
    if (rc) {
        put_device(monreader_device);
        goto out_driver;
    }

    rc = segment_type(mon_dcss_name);
    if (rc < 0) {
        segment_warning(rc, mon_dcss_name);
        goto out_device;
    }
    if (rc != SEG_TYPE_SC) {
        pr_err("The specified *MONITOR DCSS %s does not have the "
               "required type SC\n", mon_dcss_name);
        rc = -EINVAL;
        goto out_device;
    }

    rc = segment_load(mon_dcss_name, SEGMENT_SHARED,
              &mon_dcss_start, &mon_dcss_end);
    if (rc < 0) {
        segment_warning(rc, mon_dcss_name);
        rc = -EINVAL;
        goto out_device;
    }
    dcss_mkname(mon_dcss_name, &user_data_connect[8]);

    /*
     * misc_register() has to be the last action in module_init(), because
     * file operations will be available right after this.
     */
    rc = misc_register(&mon_dev);
    if (rc < 0 )
        goto out;
    return 0;

out:
    segment_unload(mon_dcss_name);
out_device:
    device_unregister(monreader_device);
out_driver:
    driver_unregister(&monreader_driver);
out_iucv:
    iucv_unregister(&monreader_iucv_handler, 1);
    return rc;
}

static void __exit mon_exit(void)
{
    segment_unload(mon_dcss_name);
    misc_deregister(&mon_dev);
    device_unregister(monreader_device);
    driver_unregister(&monreader_driver);
    iucv_unregister(&monreader_iucv_handler, 1);
    return;
}


module_init(mon_init);
module_exit(mon_exit);

module_param_string(mondcss, mon_dcss_name, 9, 0444);
MODULE_PARM_DESC(mondcss, "Name of DCSS segment to be used for *MONITOR "
         "service, max. 8 chars. Default is MONDCSS");

MODULE_AUTHOR("Gerald Schaefer <[email protected]>");
MODULE_DESCRIPTION("Character device driver for reading z/VM "
           "monitor service records.");
MODULE_LICENSE("GPL");