// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Red Hat, Inc.
 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
 */

#include <linux/efi.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/mount.h>

#include "internal.h"

static ssize_t efivarfs_file_write(struct file *file,
                const char __user *userbuf, size_t count, loff_t *ppos)
{
        struct efivar_entry *var = file->private_data;
        void *data;
        u32 attributes;
        struct inode *inode = file->f_mapping->host;
        unsigned long datasize = count - sizeof(attributes);
        ssize_t bytes;
        bool set = false;

        if (count < sizeof(attributes))
                return -EINVAL;

        if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
                return -EFAULT;

        if (attributes & ~(EFI_VARIABLE_MASK))
                return -EINVAL;

        data = memdup_user(userbuf + sizeof(attributes), datasize);
        if (IS_ERR(data))
                return PTR_ERR(data);

        inode_lock(inode);
        if (var->removed) {
                /*
                 * file got removed; don't allow a set.  Caused by an
                 * unsuccessful create or successful delete write
                 * racing with us.
                 */
                bytes = -EIO;
                goto out;
        }

        bytes = efivar_entry_set_get_size(var, attributes, &datasize,
                                          data, &set);
        if (!set) {
                if (bytes == -ENOENT)
                        bytes = -EIO;
                goto out;
        }

        if (bytes == -ENOENT) {
                /*
                 * zero size signals to release that the write deleted
                 * the variable
                 */
                i_size_write(inode, 0);
        } else {
                i_size_write(inode, datasize + sizeof(attributes));
                inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
        }

        bytes = count;

out:
        inode_unlock(inode);

        kfree(data);

        return bytes;
}

static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
                size_t count, loff_t *ppos)
{
        struct efivar_entry *var = file->private_data;
        unsigned long datasize = 0;
        u32 attributes;
        void *data;
        ssize_t size = 0;
        int err;

        while (!__ratelimit(&file->f_cred->user->ratelimit))
                msleep(50);

        err = efivar_entry_size(var, &datasize);

        /*
         * efivarfs represents uncommitted variables with
         * zero-length files. Reading them should return EOF.
         */
        if (err == -ENOENT)
                return 0;
        else if (err)
                return err;

        data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);

        if (!data)
                return -ENOMEM;

        size = efivar_entry_get(var, &attributes, &datasize,
                                data + sizeof(attributes));
        if (size)
                goto out_free;

        memcpy(data, &attributes, sizeof(attributes));
        size = simple_read_from_buffer(userbuf, count, ppos,
                                       data, datasize + sizeof(attributes));
out_free:
        kfree(data);

        return size;
}

static int efivarfs_file_release(struct inode *inode, struct file *file)
{
        struct efivar_entry *var = inode->i_private;

        inode_lock(inode);
        var->removed = (--var->open_count == 0 && i_size_read(inode) == 0);
        inode_unlock(inode);

        if (var->removed)
                simple_recursive_removal(file->f_path.dentry, NULL);

        return 0;
}

static int efivarfs_file_open(struct inode *inode, struct file *file)
{
        struct efivar_entry *entry = inode->i_private;

        file->private_data = entry;

        inode_lock(inode);
        entry->open_count++;
        inode_unlock(inode);

        return 0;
}

const struct file_operations efivarfs_file_operations = {
        .open           = efivarfs_file_open,
        .read           = efivarfs_file_read,
        .write          = efivarfs_file_write,
        .release        = efivarfs_file_release,
};