// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2014  Google, Inc.
 */

#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include "internal.h"

static DEFINE_MUTEX(pmsg_lock);

static ssize_t write_pmsg(struct file *file, const char __user *buf,
                          size_t count, loff_t *ppos)
{
        struct pstore_record record;
        int ret;

        if (!count)
                return 0;

        pstore_record_init(&record, psinfo);
        record.type = PSTORE_TYPE_PMSG;
        record.size = count;

        /* check outside lock, page in any data. write_user also checks */
        if (!access_ok(buf, count))
                return -EFAULT;

        mutex_lock(&pmsg_lock);
        ret = psinfo->write_user(&record, buf);
        mutex_unlock(&pmsg_lock);
        return ret ? ret : count;
}

static const struct file_operations pmsg_fops = {
        .owner          = THIS_MODULE,
        .llseek         = noop_llseek,
        .write          = write_pmsg,
};

static struct class *pmsg_class;
static int pmsg_major;
#define PMSG_NAME "pmsg"
#undef pr_fmt
#define pr_fmt(fmt) PMSG_NAME ": " fmt

static char *pmsg_devnode(const struct device *dev, umode_t *mode)
{
        if (mode)
                *mode = 0220;
        return NULL;
}

void pstore_register_pmsg(void)
{
        struct device *pmsg_device;

        pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
        if (pmsg_major < 0) {
                pr_err("register_chrdev failed\n");
                goto err;
        }

        pmsg_class = class_create(PMSG_NAME);
        if (IS_ERR(pmsg_class)) {
                pr_err("device class file already in use\n");
                goto err_class;
        }
        pmsg_class->devnode = pmsg_devnode;

        pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
                                        NULL, "%s%d", PMSG_NAME, 0);
        if (IS_ERR(pmsg_device)) {
                pr_err("failed to create device\n");
                goto err_device;
        }
        return;

err_device:
        class_destroy(pmsg_class);
err_class:
        unregister_chrdev(pmsg_major, PMSG_NAME);
err:
        return;
}

void pstore_unregister_pmsg(void)
{
        device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
        class_destroy(pmsg_class);
        unregister_chrdev(pmsg_major, PMSG_NAME);
}