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->dev, "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         return 0;
  83 }
  84
  85 static ssize_t tpm_read(struct file *file, char __user *buf,
  86                         size_t size, loff_t *off)
  87 {
  88         struct file_priv *priv = file->private_data;
  89         ssize_t ret_size;
  90         int rc;
  91
  92         del_singleshot_timer_sync(&priv->user_read_timer);
  93         flush_work(&priv->work);
  94         ret_size = atomic_read(&priv->data_pending);
  95         if (ret_size > 0) {     /* relay data */
  96                 ssize_t orig_ret_size = ret_size;
  97                 if (size < ret_size)
  98                         ret_size = size;
  99
 100                 mutex_lock(&priv->buffer_mutex);
 101                 rc = copy_to_user(buf, priv->data_buffer, ret_size);
 102                 memset(priv->data_buffer, 0, orig_ret_size);
 103                 if (rc)
 104                         ret_size = -EFAULT;
 105
 106                 mutex_unlock(&priv->buffer_mutex);
 107         }
 108
 109         atomic_set(&priv->data_pending, 0);
 110
 111         return ret_size;
 112 }
 113
 114 static ssize_t tpm_write(struct file *file, const char __user *buf,
 115                          size_t size, loff_t *off)
 116 {
 117         struct file_priv *priv = file->private_data;
 118         size_t in_size = size;
 119         ssize_t out_size;
 120
 121         /* cannot perform a write until the read has cleared
 122            either via tpm_read or a user_read_timer timeout.
 123            This also prevents splitted buffered writes from blocking here.
 124         */
 125         if (atomic_read(&priv->data_pending) != 0)
 126                 return -EBUSY;
 127
 128         if (in_size > TPM_BUFSIZE)
 129                 return -E2BIG;
 130
 131         mutex_lock(&priv->buffer_mutex);
 132
 133         if (copy_from_user
 134             (priv->data_buffer, (void __user *) buf, in_size)) {
 135                 mutex_unlock(&priv->buffer_mutex);
 136                 return -EFAULT;
 137         }
 138
 139         /* atomic tpm command send and result receive. We only hold the ops
 140          * lock during this period so that the tpm can be unregistered even if
 141          * the char dev is held open.
 142          */
 143         if (tpm_try_get_ops(priv->chip)) {
 144                 mutex_unlock(&priv->buffer_mutex);
 145                 return -EPIPE;
 146         }
 147         out_size = tpm_transmit(priv->chip, priv->data_buffer,
 148                                 sizeof(priv->data_buffer), 0);
 149
 150         tpm_put_ops(priv->chip);
 151         if (out_size < 0) {
 152                 mutex_unlock(&priv->buffer_mutex);
 153                 return out_size;
 154         }
 155
 156         atomic_set(&priv->data_pending, out_size);
 157         mutex_unlock(&priv->buffer_mutex);
 158
 159         /* Set a timeout by which the reader must come claim the result */
 160         mod_timer(&priv->user_read_timer, jiffies + (60 * HZ));
 161
 162         return in_size;
 163 }
 164
 165 /*
 166  * Called on file close
 167  */
 168 static int tpm_release(struct inode *inode, struct file *file)
 169 {
 170         struct file_priv *priv = file->private_data;
 171
 172         del_singleshot_timer_sync(&priv->user_read_timer);
 173         flush_work(&priv->work);
 174         file->private_data = NULL;
 175         atomic_set(&priv->data_pending, 0);
 176         clear_bit(0, &priv->chip->is_open);
 177         kfree(priv);
 178         return 0;
 179 }
 180
 181 const struct file_operations tpm_fops = {
 182         .owner = THIS_MODULE,
 183         .llseek = no_llseek,
 184         .open = tpm_open,
 185         .read = tpm_read,
 186         .write = tpm_write,
 187         .release = tpm_release,
 188 };
 189
 190