// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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
 */
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/workqueue.h>
#include "tpm.h"
#include "tpm-dev.h"

static struct workqueue_struct *tpm_dev_wq;
static DEFINE_MUTEX(tpm_dev_wq_lock);

static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
                                u8 *buf, size_t bufsiz)
{
        struct tpm_header *header = (void *)buf;
        ssize_t ret, len;

        ret = tpm2_prepare_space(chip, space, buf, bufsiz);
        /* If the command is not implemented by the TPM, synthesize a
         * response with a TPM2_RC_COMMAND_CODE return for user-space.
         */
        if (ret == -EOPNOTSUPP) {
                header->length = cpu_to_be32(sizeof(*header));
                header->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
                header->return_code = cpu_to_be32(TPM2_RC_COMMAND_CODE |
                                                  TSS2_RESMGR_TPM_RC_LAYER);
                ret = sizeof(*header);
        }
        if (ret)
                goto out_rc;

        len = tpm_transmit(chip, buf, bufsiz);
        if (len < 0)
                ret = len;

        if (!ret)
                ret = tpm2_commit_space(chip, space, buf, &len);

out_rc:
        return ret ? ret : len;
}

static void tpm_dev_async_work(struct work_struct *work)
{
        struct file_priv *priv =
                        container_of(work, struct file_priv, async_work);
        ssize_t ret;

        mutex_lock(&priv->buffer_mutex);
        priv->command_enqueued = false;
        ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
                               sizeof(priv->data_buffer));
        tpm_put_ops(priv->chip);
        if (ret > 0) {
                priv->response_length = ret;
                mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
        }
        mutex_unlock(&priv->buffer_mutex);
        wake_up_interruptible(&priv->async_wait);
}

static void user_reader_timeout(struct timer_list *t)
{
        struct file_priv *priv = from_timer(priv, t, user_read_timer);

        pr_warn("TPM user space timeout is deprecated (pid=%d)\n",
                task_tgid_nr(current));

        schedule_work(&priv->timeout_work);
}

static void tpm_timeout_work(struct work_struct *work)
{
        struct file_priv *priv = container_of(work, struct file_priv,
                                              timeout_work);

        mutex_lock(&priv->buffer_mutex);
        priv->response_read = true;
        priv->response_length = 0;
        memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
        mutex_unlock(&priv->buffer_mutex);
        wake_up_interruptible(&priv->async_wait);
}

void tpm_common_open(struct file *file, struct tpm_chip *chip,
                     struct file_priv *priv, struct tpm_space *space)
{
        priv->chip = chip;
        priv->space = space;
        priv->response_read = true;

        mutex_init(&priv->buffer_mutex);
        timer_setup(&priv->user_read_timer, user_reader_timeout, 0);
        INIT_WORK(&priv->timeout_work, tpm_timeout_work);
        INIT_WORK(&priv->async_work, tpm_dev_async_work);
        init_waitqueue_head(&priv->async_wait);
        file->private_data = priv;
}

ssize_t tpm_common_read(struct file *file, char __user *buf,
                        size_t size, loff_t *off)
{
        struct file_priv *priv = file->private_data;
        ssize_t ret_size = 0;
        int rc;

        mutex_lock(&priv->buffer_mutex);

        if (priv->response_length) {
                priv->response_read = true;

                ret_size = min_t(ssize_t, size, priv->response_length);
                if (!ret_size) {
                        priv->response_length = 0;
                        goto out;
                }

                rc = copy_to_user(buf, priv->data_buffer + *off, ret_size);
                if (rc) {
                        memset(priv->data_buffer, 0, TPM_BUFSIZE);
                        priv->response_length = 0;
                        ret_size = -EFAULT;
                } else {
                        memset(priv->data_buffer + *off, 0, ret_size);
                        priv->response_length -= ret_size;
                        *off += ret_size;
                }
        }

out:
        if (!priv->response_length) {
                *off = 0;
                del_singleshot_timer_sync(&priv->user_read_timer);
                flush_work(&priv->timeout_work);
        }
        mutex_unlock(&priv->buffer_mutex);
        return ret_size;
}

ssize_t tpm_common_write(struct file *file, const char __user *buf,
                         size_t size, loff_t *off)
{
        struct file_priv *priv = file->private_data;
        int ret = 0;

        if (size > TPM_BUFSIZE)
                return -E2BIG;

        mutex_lock(&priv->buffer_mutex);

        /* Cannot perform a write until the read has cleared either via
         * tpm_read or a user_read_timer timeout. This also prevents split
         * buffered writes from blocking here.
         */
        if ((!priv->response_read && priv->response_length) ||
            priv->command_enqueued) {
                ret = -EBUSY;
                goto out;
        }

        if (copy_from_user(priv->data_buffer, buf, size)) {
                ret = -EFAULT;
                goto out;
        }

        if (size < 6 ||
            size < be32_to_cpu(*((__be32 *)(priv->data_buffer + 2)))) {
                ret = -EINVAL;
                goto out;
        }

        /* atomic tpm command send and result receive. We only hold the ops
         * lock during this period so that the tpm can be unregistered even if
         * the char dev is held open.
         */
        if (tpm_try_get_ops(priv->chip)) {
                ret = -EPIPE;
                goto out;
        }

        priv->response_length = 0;
        priv->response_read = false;
        *off = 0;

        /*
         * If in nonblocking mode schedule an async job to send
         * the command return the size.
         * In case of error the err code will be returned in
         * the subsequent read call.
         */
        if (file->f_flags & O_NONBLOCK) {
                priv->command_enqueued = true;
                queue_work(tpm_dev_wq, &priv->async_work);
                mutex_unlock(&priv->buffer_mutex);
                return size;
        }

        ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
                               sizeof(priv->data_buffer));
        tpm_put_ops(priv->chip);

        if (ret > 0) {
                priv->response_length = ret;
                mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
                ret = size;
        }
out:
        mutex_unlock(&priv->buffer_mutex);
        return ret;
}

__poll_t tpm_common_poll(struct file *file, poll_table *wait)
{
        struct file_priv *priv = file->private_data;
        __poll_t mask = 0;

        poll_wait(file, &priv->async_wait, wait);
        mutex_lock(&priv->buffer_mutex);

        /*
         * The response_length indicates if there is still response
         * (or part of it) to be consumed. Partial reads decrease it
         * by the number of bytes read, and write resets it the zero.
         */
        if (priv->response_length)
                mask = EPOLLIN | EPOLLRDNORM;
        else
                mask = EPOLLOUT | EPOLLWRNORM;

        mutex_unlock(&priv->buffer_mutex);
        return mask;
}

/*
 * Called on file close
 */
void tpm_common_release(struct file *file, struct file_priv *priv)
{
        flush_work(&priv->async_work);
        del_singleshot_timer_sync(&priv->user_read_timer);
        flush_work(&priv->timeout_work);
        file->private_data = NULL;
        priv->response_length = 0;
}

int __init tpm_dev_common_init(void)
{
        tpm_dev_wq = alloc_workqueue("tpm_dev_wq", WQ_MEM_RECLAIM, 0);

        return !tpm_dev_wq ? -ENOMEM : 0;
}

void __exit tpm_dev_common_exit(void)
{
        if (tpm_dev_wq) {
                destroy_workqueue(tpm_dev_wq);
                tpm_dev_wq = NULL;
        }
}