LXR linux/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
  24struct 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
  37static 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
  44static 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
  54static 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
  86static 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
 115static 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 */
 160static 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
 174const 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
 184