drivers/char/tpm/tpm-dev.c

   1 /*
   2  * Copyright (C) 2004 IBM Corporation
   3  * Authors:
   4  * Leendert van Doorn <leendert@watson.ibm.com>
   5  * Dave Safford <safford@watson.ibm.com>
   6  * Reiner Sailer <sailer@watson.ibm.com>
   7  * Kylene Hall <kjhall@us.ibm.com>
   8  *
   9  * Copyright (C) 2013 Obsidian Research Corp
  10  * Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
  11  *
  12  * Device file system interface to the TPM
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License as
  16  * published by the Free Software Foundation, version 2 of the
  17  * License.
  18  *
  19  */
  20 #include <linux/slab.h>
  21 #include <linux/uaccess.h>
  22 #include "tpm.h"
  23
  24 struct file_priv {
  25         struct tpm_chip *chip;
  26
  27         /* Data passed to and from the tpm via the read/write calls */
  28         atomic_t data_pending;
  29         struct mutex buffer_mutex;
  30
  31         struct timer_list user_read_timer;      /* user needs to claim result */
  32         struct work_struct work;
  33
  34         u8 data_buffer[TPM_BUFSIZE];
  35 };
  36
  37 static void user_reader_timeout(unsigned long ptr)
  38 {
  39         struct file_priv *priv = (struct file_priv *)ptr;
  40
  41         schedule_work(&priv->work);
  42 }
  43
  44 static void timeout_work(struct work_struct *work)
  45 {
  46         struct file_priv *priv = container_of(work, struct file_priv, work);
  47
  48         mutex_lock(&priv->buffer_mutex);
  49         atomic_set(&priv->data_pending, 0);
  50         memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
  51         mutex_unlock(&priv->buffer_mutex);
  52 }
  53
  54 static int tpm_open(struct inode *inode, struct file *file)
  55 {
  56         struct tpm_chip *chip =
  57                 container_of(inode->i_cdev, struct tpm_chip, cdev);
  58         struct file_priv *priv;
  59
  60         /* It's assured that the chip will be opened just once,
  61          * by the check of is_open variable, which is protected
  62          * by driver_lock. */
  63         if (test_and_set_bit(0, &chip->is_open)) {
  64                 dev_dbg(chip->pdev, "Another process owns this TPM\n");
  65                 return -EBUSY;
  66         }
  67
  68         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  69         if (priv == NULL) {
  70                 clear_bit(0, &chip->is_open);
  71                 return -ENOMEM;
  72         }
  73
  74         priv->chip = chip;
  75         atomic_set(&priv->data_pending, 0);
  76         mutex_init(&priv->buffer_mutex);
  77         setup_timer(&priv->user_read_timer, user_reader_timeout,
  78                         (unsigned long)priv);
  79         INIT_WORK(&priv->work, timeout_work);
  80
  81         file->private_data = priv;
  82         get_device(chip->pdev);
  83         return 0;
  84 }
  85
  86 static ssize_t tpm_read(struct file *file, char __user *buf,
  87                         size_t size, loff_t *off)
  88 {
  89         struct file_priv *priv = file->private_data;
  90         ssize_t ret_size;
  91         int rc;
  92
  93         del_singleshot_timer_sync(&priv->user_read_timer);
  94         flush_work(&priv->work);
  95         ret_size = atomic_read(&priv->data_pending);
  96         if (ret_size > 0) {     /* relay data */
  97                 ssize_t orig_ret_size = ret_size;
  98                 if (size < ret_size)
  99                         ret_size = size;
 100
 101                 mutex_lock(&priv->buffer_mutex);
 102                 rc = copy_to_user(buf, priv->data_buffer, ret_size);
 103                 memset(priv->data_buffer, 0, orig_ret_size);
 104                 if (rc)
 105                         ret_size = -EFAULT;
 106
 107                 mutex_unlock(&priv->buffer_mutex);
 108         }
 109
 110         atomic_set(&priv->data_pending, 0);
 111
 112         return ret_size;
 113 }
 114
 115 static ssize_t tpm_write(struct file *file, const char __user *buf,
 116                          size_t size, loff_t *off)
 117 {
 118         struct file_priv *priv = file->private_data;
 119         size_t in_size = size;
 120         ssize_t out_size;
 121
 122         /* cannot perform a write until the read has cleared
 123            either via tpm_read or a user_read_timer timeout.
 124            This also prevents splitted buffered writes from blocking here.
 125         */
 126         if (atomic_read(&priv->data_pending) != 0)
 127                 return -EBUSY;
 128
 129         if (in_size > TPM_BUFSIZE)
 130                 return -E2BIG;
 131
 132         mutex_lock(&priv->buffer_mutex);
 133
 134         if (copy_from_user
 135             (priv->data_buffer, (void __user *) buf, in_size)) {
 136                 mutex_unlock(&priv->buffer_mutex);
 137                 return -EFAULT;
 138         }
 139
 140         /* atomic tpm command send and result receive */
 141         out_size = tpm_transmit(priv->chip, priv->data_buffer,
 142                                 sizeof(priv->data_buffer));
 143         if (out_size < 0) {
 144                 mutex_unlock(&priv->buffer_mutex);
 145                 return out_size;
 146         }
 147
 148         atomic_set(&priv->data_pending, out_size);
 149         mutex_unlock(&priv->buffer_mutex);
 150
 151         /* Set a timeout by which the reader must come claim the result */
 152         mod_timer(&priv->user_read_timer, jiffies + (60 * HZ));
 153
 154         return in_size;
 155 }
 156
 157 /*
 158  * Called on file close
 159  */
 160 static int tpm_release(struct inode *inode, struct file *file)
 161 {
 162         struct file_priv *priv = file->private_data;
 163
 164         del_singleshot_timer_sync(&priv->user_read_timer);
 165         flush_work(&priv->work);
 166         file->private_data = NULL;
 167         atomic_set(&priv->data_pending, 0);
 168         clear_bit(0, &priv->chip->is_open);
 169         put_device(priv->chip->pdev);
 170         kfree(priv);
 171         return 0;
 172 }
 173
 174 const struct file_operations tpm_fops = {
 175         .owner = THIS_MODULE,
 176         .llseek = no_llseek,
 177         .open = tpm_open,
 178         .read = tpm_read,
 179         .write = tpm_write,
 180         .release = tpm_release,
 181 };
 182
 183