// SPDX-License-Identifier: GPL-2.0
/*
 * Deliver z/VM CP special messages (SMSG) as uevents.
 *
 * The driver registers for z/VM CP special messages with the
 * "APP" prefix. Incoming messages are delivered to user space
 * as uevents.
 *
 * Copyright IBM Corp. 2010
 * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
 *
 */
#define pr_fmt(fmt) "smsgiucv_app: " fmt

#include <linux/ctype.h>
#include <linux/err.h>
#include <linux/device.h>
#include <linux/list.h>
#include <linux/kobject.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <net/iucv/iucv.h>
#include <asm/machine.h>
#include "smsgiucv.h"

/* prefix used for SMSG registration */
#define SMSG_PREFIX             "APP"

/* SMSG related uevent environment variables */
#define ENV_SENDER_STR          "SMSG_SENDER="
#define ENV_SENDER_LEN          (strlen(ENV_SENDER_STR) + 8 + 1)
#define ENV_PREFIX_STR          "SMSG_ID="
#define ENV_PREFIX_LEN          (strlen(ENV_PREFIX_STR) + \
                                 strlen(SMSG_PREFIX) + 1)
#define ENV_TEXT_STR            "SMSG_TEXT="
#define ENV_TEXT_LEN(msg)       (strlen(ENV_TEXT_STR) + strlen((msg)) + 1)

/* z/VM user ID which is permitted to send SMSGs
 * If the value is undefined or empty (""), special messages are
 * accepted from any z/VM user ID. */
static char *sender;
module_param(sender, charp, 0400);
MODULE_PARM_DESC(sender, "z/VM user ID from which CP SMSGs are accepted");

/* SMSG device representation */
static struct device *smsg_app_dev;

/* list element for queuing received messages for delivery */
struct smsg_app_event {
        struct list_head list;
        char *buf;
        char *envp[4];
};

/* queue for outgoing uevents */
static LIST_HEAD(smsg_event_queue);
static DEFINE_SPINLOCK(smsg_event_queue_lock);

static void smsg_app_event_free(struct smsg_app_event *ev)
{
        kfree(ev->buf);
        kfree(ev);
}

static struct smsg_app_event *smsg_app_event_alloc(const char *from,
                                                   const char *msg)
{
        struct smsg_app_event *ev;

        ev = kzalloc_obj(*ev, GFP_ATOMIC);
        if (!ev)
                return NULL;

        ev->buf = kzalloc(ENV_SENDER_LEN + ENV_PREFIX_LEN +
                          ENV_TEXT_LEN(msg), GFP_ATOMIC);
        if (!ev->buf) {
                kfree(ev);
                return NULL;
        }

        /* setting up environment pointers into buf */
        ev->envp[0] = ev->buf;
        ev->envp[1] = ev->envp[0] + ENV_SENDER_LEN;
        ev->envp[2] = ev->envp[1] + ENV_PREFIX_LEN;
        ev->envp[3] = NULL;

        /* setting up environment: sender, prefix name, and message text */
        scnprintf(ev->envp[0], ENV_SENDER_LEN, ENV_SENDER_STR "%s", from);
        scnprintf(ev->envp[1], ENV_PREFIX_LEN, ENV_PREFIX_STR "%s",
                  SMSG_PREFIX);
        scnprintf(ev->envp[2], ENV_TEXT_LEN(msg), ENV_TEXT_STR "%s", msg);

        return ev;
}

static void smsg_event_work_fn(struct work_struct *work)
{
        LIST_HEAD(event_queue);
        struct smsg_app_event *p, *n;
        struct device *dev;

        dev = get_device(smsg_app_dev);
        if (!dev)
                return;

        spin_lock_bh(&smsg_event_queue_lock);
        list_splice_init(&smsg_event_queue, &event_queue);
        spin_unlock_bh(&smsg_event_queue_lock);

        list_for_each_entry_safe(p, n, &event_queue, list) {
                list_del(&p->list);
                kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, p->envp);
                smsg_app_event_free(p);
        }

        put_device(dev);
}
static DECLARE_WORK(smsg_event_work, smsg_event_work_fn);

static void smsg_app_callback(const char *from, char *msg)
{
        struct smsg_app_event *se;

        /* check if the originating z/VM user ID matches
         * the configured sender. */
        if (sender && strlen(sender) > 0 && strcmp(from, sender) != 0)
                return;

        /* get start of message text (skip prefix and leading blanks) */
        msg += strlen(SMSG_PREFIX);
        while (*msg && isspace(*msg))
                msg++;
        if (*msg == '\0')
                return;

        /* allocate event list element and its environment */
        se = smsg_app_event_alloc(from, msg);
        if (!se)
                return;

        /* queue event and schedule work function */
        spin_lock(&smsg_event_queue_lock);
        list_add_tail(&se->list, &smsg_event_queue);
        spin_unlock(&smsg_event_queue_lock);

        schedule_work(&smsg_event_work);
        return;
}

static int __init smsgiucv_app_init(void)
{
        struct device_driver *smsgiucv_drv;
        int rc;

        if (!machine_is_vm())
                return -ENODEV;

        smsgiucv_drv = driver_find(SMSGIUCV_DRV_NAME, &iucv_bus);
        if (!smsgiucv_drv)
                return -ENODEV;

        smsg_app_dev = iucv_alloc_device(NULL, smsgiucv_drv, NULL, "smsgiucv_app");
        if (!smsg_app_dev)
                return -ENOMEM;

        rc = device_register(smsg_app_dev);
        if (rc) {
                put_device(smsg_app_dev);
                goto fail;
        }

        /* convert sender to uppercase characters */
        if (sender) {
                int len = strlen(sender);
                while (len--)
                        sender[len] = toupper(sender[len]);
        }

        /* register with the smsgiucv device driver */
        rc = smsg_register_callback(SMSG_PREFIX, smsg_app_callback);
        if (rc) {
                device_unregister(smsg_app_dev);
                goto fail;
        }

        rc = 0;
fail:
        return rc;
}
module_init(smsgiucv_app_init);

static void __exit smsgiucv_app_exit(void)
{
        /* unregister callback */
        smsg_unregister_callback(SMSG_PREFIX, smsg_app_callback);

        /* cancel pending work and flush any queued event work */
        cancel_work_sync(&smsg_event_work);
        smsg_event_work_fn(&smsg_event_work);

        device_unregister(smsg_app_dev);
}
module_exit(smsgiucv_app_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Deliver z/VM CP SMSG as uevents");
MODULE_AUTHOR("Hendrik Brueckner <brueckner@linux.vnet.ibm.com>");