drivers/char/tpm/tpm-dev-common.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 #include "tpm-dev.h"
  24
  25 static void user_reader_timeout(unsigned long ptr)
  26 {
  27         struct file_priv *priv = (struct file_priv *)ptr;
  28
  29         pr_warn("TPM user space timeout is deprecated (pid=%d)\n",
  30                 task_tgid_nr(current));
  31
  32         schedule_work(&priv->work);
  33 }
  34
  35 static void timeout_work(struct work_struct *work)
  36 {
  37         struct file_priv *priv = container_of(work, struct file_priv, work);
  38
  39         mutex_lock(&priv->buffer_mutex);
  40         atomic_set(&priv->data_pending, 0);
  41         memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
  42         mutex_unlock(&priv->buffer_mutex);
  43 }
  44
  45 void tpm_common_open(struct file *file, struct tpm_chip *chip,
  46                      struct file_priv *priv)
  47 {
  48         priv->chip = chip;
  49         atomic_set(&priv->data_pending, 0);
  50         mutex_init(&priv->buffer_mutex);
  51         setup_timer(&priv->user_read_timer, user_reader_timeout,
  52                         (unsigned long)priv);
  53         INIT_WORK(&priv->work, timeout_work);
  54
  55         file->private_data = priv;
  56 }
  57
  58 ssize_t tpm_common_read(struct file *file, char __user *buf,
  59                         size_t size, loff_t *off)
  60 {
  61         struct file_priv *priv = file->private_data;
  62         ssize_t ret_size;
  63         ssize_t orig_ret_size;
  64         int rc;
  65
  66         del_singleshot_timer_sync(&priv->user_read_timer);
  67         flush_work(&priv->work);
  68         ret_size = atomic_read(&priv->data_pending);
  69         if (ret_size > 0) {     /* relay data */
  70                 orig_ret_size = ret_size;
  71                 if (size < ret_size)
  72                         ret_size = size;
  73
  74                 mutex_lock(&priv->buffer_mutex);
  75                 rc = copy_to_user(buf, priv->data_buffer, ret_size);
  76                 memset(priv->data_buffer, 0, orig_ret_size);
  77                 if (rc)
  78                         ret_size = -EFAULT;
  79
  80                 mutex_unlock(&priv->buffer_mutex);
  81         }
  82
  83         atomic_set(&priv->data_pending, 0);
  84
  85         return ret_size;
  86 }
  87
  88 ssize_t tpm_common_write(struct file *file, const char __user *buf,
  89                          size_t size, loff_t *off, struct tpm_space *space)
  90 {
  91         struct file_priv *priv = file->private_data;
  92         size_t in_size = size;
  93         ssize_t out_size;
  94
  95         /* Cannot perform a write until the read has cleared either via
  96          * tpm_read or a user_read_timer timeout. This also prevents split
  97          * buffered writes from blocking here.
  98          */
  99         if (atomic_read(&priv->data_pending) != 0)
 100                 return -EBUSY;
 101
 102         if (in_size > TPM_BUFSIZE)
 103                 return -E2BIG;
 104
 105         mutex_lock(&priv->buffer_mutex);
 106
 107         if (copy_from_user
 108             (priv->data_buffer, (void __user *) buf, in_size)) {
 109                 mutex_unlock(&priv->buffer_mutex);
 110                 return -EFAULT;
 111         }
 112
 113         /* atomic tpm command send and result receive. We only hold the ops
 114          * lock during this period so that the tpm can be unregistered even if
 115          * the char dev is held open.
 116          */
 117         if (tpm_try_get_ops(priv->chip)) {
 118                 mutex_unlock(&priv->buffer_mutex);
 119                 return -EPIPE;
 120         }
 121         out_size = tpm_transmit(priv->chip, space, priv->data_buffer,
 122                                 sizeof(priv->data_buffer), 0);
 123
 124         tpm_put_ops(priv->chip);
 125         if (out_size < 0) {
 126                 mutex_unlock(&priv->buffer_mutex);
 127                 return out_size;
 128         }
 129
 130         atomic_set(&priv->data_pending, out_size);
 131         mutex_unlock(&priv->buffer_mutex);
 132
 133         /* Set a timeout by which the reader must come claim the result */
 134         mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
 135
 136         return in_size;
 137 }
 138
 139 /*
 140  * Called on file close
 141  */
 142 void tpm_common_release(struct file *file, struct file_priv *priv)
 143 {
 144         del_singleshot_timer_sync(&priv->user_read_timer);
 145         flush_work(&priv->work);
 146         file->private_data = NULL;
 147         atomic_set(&priv->data_pending, 0);
 148 }