/*
 * This file is provided under the GPLv2 license.
 *
 * GPL LICENSE SUMMARY
 *
 * Copyright(c) 2014 Intel Mobile Communications GmbH
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * The full GNU General Public License is included in this distribution
 * in the file called COPYING.
 *
 * Contact Information:
 *  Intel Linux Wireless <ilw@linux.intel.com>
 * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
 *
 * Author: Johannes Berg <johannes@sipsolutions.net>
 */
#include <linux/module.h>
#include <linux/device.h>
#include <linux/devcoredump.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/workqueue.h>

static struct class devcd_class;

/* global disable flag, for security purposes */
static bool devcd_disabled;

/* if data isn't read by userspace after 5 minutes then delete it */
#define DEVCD_TIMEOUT   (HZ * 60 * 5)

struct devcd_entry {
        struct device devcd_dev;
        const void *data;
        size_t datalen;
        struct module *owner;
        ssize_t (*read)(char *buffer, loff_t offset, size_t count,
                        const void *data, size_t datalen);
        void (*free)(const void *data);
        struct delayed_work del_wk;
        struct device *failing_dev;
};

static struct devcd_entry *dev_to_devcd(struct device *dev)
{
        return container_of(dev, struct devcd_entry, devcd_dev);
}

static void devcd_dev_release(struct device *dev)
{
        struct devcd_entry *devcd = dev_to_devcd(dev);

        devcd->free(devcd->data);
        module_put(devcd->owner);

        /*
         * this seems racy, but I don't see a notifier or such on
         * a struct device to know when it goes away?
         */
        if (devcd->failing_dev->kobj.sd)
                sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
                                  "devcoredump");

        put_device(devcd->failing_dev);
        kfree(devcd);
}

static void devcd_del(struct work_struct *wk)
{
        struct devcd_entry *devcd;

        devcd = container_of(wk, struct devcd_entry, del_wk.work);

        device_del(&devcd->devcd_dev);
        put_device(&devcd->devcd_dev);
}

static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
                               struct bin_attribute *bin_attr,
                               char *buffer, loff_t offset, size_t count)
{
        struct device *dev = kobj_to_dev(kobj);
        struct devcd_entry *devcd = dev_to_devcd(dev);

        return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
}

static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
                                struct bin_attribute *bin_attr,
                                char *buffer, loff_t offset, size_t count)
{
        struct device *dev = kobj_to_dev(kobj);
        struct devcd_entry *devcd = dev_to_devcd(dev);

        mod_delayed_work(system_wq, &devcd->del_wk, 0);

        return count;
}

static struct bin_attribute devcd_attr_data = {
        .attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
        .size = 0,
        .read = devcd_data_read,
        .write = devcd_data_write,
};

static struct bin_attribute *devcd_dev_bin_attrs[] = {
        &devcd_attr_data, NULL,
};

static const struct attribute_group devcd_dev_group = {
        .bin_attrs = devcd_dev_bin_attrs,
};

static const struct attribute_group *devcd_dev_groups[] = {
        &devcd_dev_group, NULL,
};

static int devcd_free(struct device *dev, void *data)
{
        struct devcd_entry *devcd = dev_to_devcd(dev);

        flush_delayed_work(&devcd->del_wk);
        return 0;
}

static ssize_t disabled_show(struct class *class, struct class_attribute *attr,
                             char *buf)
{
        return sprintf(buf, "%d\n", devcd_disabled);
}

static ssize_t disabled_store(struct class *class, struct class_attribute *attr,
                              const char *buf, size_t count)
{
        long tmp = simple_strtol(buf, NULL, 10);

        /*
         * This essentially makes the attribute write-once, since you can't
         * go back to not having it disabled. This is intentional, it serves
         * as a system lockdown feature.
         */
        if (tmp != 1)
                return -EINVAL;

        devcd_disabled = true;

        class_for_each_device(&devcd_class, NULL, NULL, devcd_free);

        return count;
}

static struct class_attribute devcd_class_attrs[] = {
        __ATTR_RW(disabled),
        __ATTR_NULL
};

static struct class devcd_class = {
        .name           = "devcoredump",
        .owner          = THIS_MODULE,
        .dev_release    = devcd_dev_release,
        .dev_groups     = devcd_dev_groups,
        .class_attrs    = devcd_class_attrs,
};

static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
                           const void *data, size_t datalen)
{
        if (offset > datalen)
                return -EINVAL;

        if (offset + count > datalen)
                count = datalen - offset;

        if (count)
                memcpy(buffer, ((u8 *)data) + offset, count);

        return count;
}

/**
 * dev_coredumpv - create device coredump with vmalloc data
 * @dev: the struct device for the crashed device
 * @data: vmalloc data containing the device coredump
 * @datalen: length of the data
 * @gfp: allocation flags
 *
 * This function takes ownership of the vmalloc'ed data and will free
 * it when it is no longer used. See dev_coredumpm() for more information.
 */
void dev_coredumpv(struct device *dev, const void *data, size_t datalen,
                   gfp_t gfp)
{
        dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, vfree);
}
EXPORT_SYMBOL_GPL(dev_coredumpv);

static int devcd_match_failing(struct device *dev, const void *failing)
{
        struct devcd_entry *devcd = dev_to_devcd(dev);

        return devcd->failing_dev == failing;
}

/**
 * dev_coredumpm - create device coredump with read/free methods
 * @dev: the struct device for the crashed device
 * @owner: the module that contains the read/free functions, use %THIS_MODULE
 * @data: data cookie for the @read/@free functions
 * @datalen: length of the data
 * @gfp: allocation flags
 * @read: function to read from the given buffer
 * @free: function to free the given buffer
 *
 * Creates a new device coredump for the given device. If a previous one hasn't
 * been read yet, the new coredump is discarded. The data lifetime is determined
 * by the device coredump framework and when it is no longer needed the @free
 * function will be called to free the data.
 */
void dev_coredumpm(struct device *dev, struct module *owner,
                   const void *data, size_t datalen, gfp_t gfp,
                   ssize_t (*read)(char *buffer, loff_t offset, size_t count,
                                   const void *data, size_t datalen),
                   void (*free)(const void *data))
{
        static atomic_t devcd_count = ATOMIC_INIT(0);
        struct devcd_entry *devcd;
        struct device *existing;

        if (devcd_disabled)
                goto free;

        existing = class_find_device(&devcd_class, NULL, dev,
                                     devcd_match_failing);
        if (existing) {
                put_device(existing);
                goto free;
        }

        if (!try_module_get(owner))
                goto free;

        devcd = kzalloc(sizeof(*devcd), gfp);
        if (!devcd)
                goto put_module;

        devcd->owner = owner;
        devcd->data = data;
        devcd->datalen = datalen;
        devcd->read = read;
        devcd->free = free;
        devcd->failing_dev = get_device(dev);

        device_initialize(&devcd->devcd_dev);

        dev_set_name(&devcd->devcd_dev, "devcd%d",
                     atomic_inc_return(&devcd_count));
        devcd->devcd_dev.class = &devcd_class;

        if (device_add(&devcd->devcd_dev))
                goto put_device;

        if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
                              "failing_device"))
                /* nothing - symlink will be missing */;

        if (sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
                              "devcoredump"))
                /* nothing - symlink will be missing */;

        INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
        schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);

        return;
 put_device:
        put_device(&devcd->devcd_dev);
 put_module:
        module_put(owner);
 free:
        free(data);
}
EXPORT_SYMBOL_GPL(dev_coredumpm);

static int __init devcoredump_init(void)
{
        return class_register(&devcd_class);
}
__initcall(devcoredump_init);

static void __exit devcoredump_exit(void)
{
        class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
        class_unregister(&devcd_class);
}
__exitcall(devcoredump_exit);