tpm-dev.c
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/*
* Copyright (C) 2004 IBM Corporation
* Authors:
* Leendert van Doorn <leendert@watson.ibm.com>
* Dave Safford <safford@watson.ibm.com>
* Reiner Sailer <sailer@watson.ibm.com>
* Kylene Hall <kjhall@us.ibm.com>
*
* Copyright (C) 2013 Obsidian Research Corp
* Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
*
* Device file system interface to the TPM
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*
*/
#include <linux/slab.h>
#include <linux/uaccess.h>
#include "tpm.h"
struct file_priv {
struct tpm_chip *chip;
/* Data passed to and from the tpm via the read/write calls */
atomic_t data_pending;
struct mutex buffer_mutex;
struct timer_list user_read_timer; /* user needs to claim result */
struct work_struct work;
u8 data_buffer[TPM_BUFSIZE];
};
static void user_reader_timeout(unsigned long ptr)
{
struct file_priv *priv = (struct file_priv *)ptr;
schedule_work(&priv->work);
}
static void timeout_work(struct work_struct *work)
{
struct file_priv *priv = container_of(work, struct file_priv, work);
mutex_lock(&priv->buffer_mutex);
atomic_set(&priv->data_pending, 0);
memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
mutex_unlock(&priv->buffer_mutex);
}
static int tpm_open(struct inode *inode, struct file *file)
{
struct tpm_chip *chip =
container_of(inode->i_cdev, struct tpm_chip, cdev);
struct file_priv *priv;
/* It's assured that the chip will be opened just once,
* by the check of is_open variable, which is protected
* by driver_lock. */
if (test_and_set_bit(0, &chip->is_open)) {
dev_dbg(chip->pdev, "Another process owns this TPM\n");
return -EBUSY;
}
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (priv == NULL) {
clear_bit(0, &chip->is_open);
return -ENOMEM;
}
priv->chip = chip;
atomic_set(&priv->data_pending, 0);
mutex_init(&priv->buffer_mutex);
setup_timer(&priv->user_read_timer, user_reader_timeout,
(unsigned long)priv);
INIT_WORK(&priv->work, timeout_work);
file->private_data = priv;
get_device(chip->pdev);
return 0;
}
static ssize_t tpm_read(struct file *file, char __user *buf,
size_t size, loff_t *off)
{
struct file_priv *priv = file->private_data;
ssize_t ret_size;
int rc;
del_singleshot_timer_sync(&priv->user_read_timer);
flush_work(&priv->work);
ret_size = atomic_read(&priv->data_pending);
if (ret_size > 0) { /* relay data */
ssize_t orig_ret_size = ret_size;
if (size < ret_size)
ret_size = size;
mutex_lock(&priv->buffer_mutex);
rc = copy_to_user(buf, priv->data_buffer, ret_size);
memset(priv->data_buffer, 0, orig_ret_size);
if (rc)
ret_size = -EFAULT;
mutex_unlock(&priv->buffer_mutex);
}
atomic_set(&priv->data_pending, 0);
return ret_size;
}
static ssize_t tpm_write(struct file *file, const char __user *buf,
size_t size, loff_t *off)
{
struct file_priv *priv = file->private_data;
size_t in_size = size;
ssize_t out_size;
/* cannot perform a write until the read has cleared
either via tpm_read or a user_read_timer timeout.
This also prevents splitted buffered writes from blocking here.
*/
if (atomic_read(&priv->data_pending) != 0)
return -EBUSY;
if (in_size > TPM_BUFSIZE)
return -E2BIG;
mutex_lock(&priv->buffer_mutex);
if (copy_from_user
(priv->data_buffer, (void __user *) buf, in_size)) {
mutex_unlock(&priv->buffer_mutex);
return -EFAULT;
}
/* atomic tpm command send and result receive */
out_size = tpm_transmit(priv->chip, priv->data_buffer,
sizeof(priv->data_buffer), 0);
if (out_size < 0) {
mutex_unlock(&priv->buffer_mutex);
return out_size;
}
atomic_set(&priv->data_pending, out_size);
mutex_unlock(&priv->buffer_mutex);
/* Set a timeout by which the reader must come claim the result */
mod_timer(&priv->user_read_timer, jiffies + (60 * HZ));
return in_size;
}
/*
* Called on file close
*/
static int tpm_release(struct inode *inode, struct file *file)
{
struct file_priv *priv = file->private_data;
del_singleshot_timer_sync(&priv->user_read_timer);
flush_work(&priv->work);
file->private_data = NULL;
atomic_set(&priv->data_pending, 0);
clear_bit(0, &priv->chip->is_open);
put_device(priv->chip->pdev);
kfree(priv);
return 0;
}
const struct file_operations tpm_fops = {
.owner = THIS_MODULE,
.llseek = no_llseek,
.open = tpm_open,
.read = tpm_read,
.write = tpm_write,
.release = tpm_release,
};