linux/fs/efivarfs/file.c
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   1/*
   2 * Copyright (C) 2012 Red Hat, Inc.
   3 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
   4 *
   5 * This program is free software; you can redistribute it and/or modify
   6 * it under the terms of the GNU General Public License version 2 as
   7 * published by the Free Software Foundation.
   8 */
   9
  10#include <linux/efi.h>
  11#include <linux/fs.h>
  12#include <linux/slab.h>
  13
  14#include "internal.h"
  15
  16static ssize_t efivarfs_file_write(struct file *file,
  17                const char __user *userbuf, size_t count, loff_t *ppos)
  18{
  19        struct efivar_entry *var = file->private_data;
  20        void *data;
  21        u32 attributes;
  22        struct inode *inode = file->f_mapping->host;
  23        unsigned long datasize = count - sizeof(attributes);
  24        ssize_t bytes = 0;
  25        bool set = false;
  26
  27        if (count < sizeof(attributes))
  28                return -EINVAL;
  29
  30        if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
  31                return -EFAULT;
  32
  33        if (attributes & ~(EFI_VARIABLE_MASK))
  34                return -EINVAL;
  35
  36        data = kmalloc(datasize, GFP_KERNEL);
  37        if (!data)
  38                return -ENOMEM;
  39
  40        if (copy_from_user(data, userbuf + sizeof(attributes), datasize)) {
  41                bytes = -EFAULT;
  42                goto out;
  43        }
  44
  45        bytes = efivar_entry_set_get_size(var, attributes, &datasize,
  46                                          data, &set);
  47        if (!set && bytes) {
  48                if (bytes == -ENOENT)
  49                        bytes = -EIO;
  50                goto out;
  51        }
  52
  53        if (bytes == -ENOENT) {
  54                drop_nlink(inode);
  55                d_delete(file->f_dentry);
  56                dput(file->f_dentry);
  57        } else {
  58                mutex_lock(&inode->i_mutex);
  59                i_size_write(inode, datasize + sizeof(attributes));
  60                mutex_unlock(&inode->i_mutex);
  61        }
  62
  63        bytes = count;
  64
  65out:
  66        kfree(data);
  67
  68        return bytes;
  69}
  70
  71static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
  72                size_t count, loff_t *ppos)
  73{
  74        struct efivar_entry *var = file->private_data;
  75        unsigned long datasize = 0;
  76        u32 attributes;
  77        void *data;
  78        ssize_t size = 0;
  79        int err;
  80
  81        err = efivar_entry_size(var, &datasize);
  82
  83        /*
  84         * efivarfs represents uncommitted variables with
  85         * zero-length files. Reading them should return EOF.
  86         */
  87        if (err == -ENOENT)
  88                return 0;
  89        else if (err)
  90                return err;
  91
  92        data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
  93
  94        if (!data)
  95                return -ENOMEM;
  96
  97        size = efivar_entry_get(var, &attributes, &datasize,
  98                                data + sizeof(attributes));
  99        if (size)
 100                goto out_free;
 101
 102        memcpy(data, &attributes, sizeof(attributes));
 103        size = simple_read_from_buffer(userbuf, count, ppos,
 104                                       data, datasize + sizeof(attributes));
 105out_free:
 106        kfree(data);
 107
 108        return size;
 109}
 110
 111const struct file_operations efivarfs_file_operations = {
 112        .open   = simple_open,
 113        .read   = efivarfs_file_read,
 114        .write  = efivarfs_file_write,
 115        .llseek = no_llseek,
 116};
 117
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