/*
 * Copyright (C) 2015, 2016 IBM Corporation
 *
 * Author: Stefan Berger <stefanb@us.ibm.com>
 *
 * Maintained by: <tpmdd-devel@lists.sourceforge.net>
 *
 * Device driver for vTPM (vTPM proxy driver)
 *
 * 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/types.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
#include <linux/miscdevice.h>
#include <linux/vtpm_proxy.h>
#include <linux/file.h>
#include <linux/anon_inodes.h>
#include <linux/poll.h>
#include <linux/compat.h>

#include "tpm.h"

#define VTPM_PROXY_REQ_COMPLETE_FLAG  BIT(0)

struct proxy_dev {
        struct tpm_chip *chip;

        u32 flags;                   /* public API flags */

        wait_queue_head_t wq;

        struct mutex buf_lock;       /* protect buffer and flags */

        long state;                  /* internal state */
#define STATE_OPENED_FLAG        BIT(0)
#define STATE_WAIT_RESPONSE_FLAG BIT(1)  /* waiting for emulator response */

        size_t req_len;              /* length of queued TPM request */
        size_t resp_len;             /* length of queued TPM response */
        u8 buffer[TPM_BUFSIZE];      /* request/response buffer */

        struct work_struct work;     /* task that retrieves TPM timeouts */
};

/* all supported flags */
#define VTPM_PROXY_FLAGS_ALL  (VTPM_PROXY_FLAG_TPM2)

static struct workqueue_struct *workqueue;

static void vtpm_proxy_delete_device(struct proxy_dev *proxy_dev);

/*
 * Functions related to 'server side'
 */

/**
 * vtpm_proxy_fops_read - Read TPM commands on 'server side'
 *
 * Return value:
 *      Number of bytes read or negative error code
 */
static ssize_t vtpm_proxy_fops_read(struct file *filp, char __user *buf,
                                    size_t count, loff_t *off)
{
        struct proxy_dev *proxy_dev = filp->private_data;
        size_t len;
        int sig, rc;

        sig = wait_event_interruptible(proxy_dev->wq,
                proxy_dev->req_len != 0 ||
                !(proxy_dev->state & STATE_OPENED_FLAG));
        if (sig)
                return -EINTR;

        mutex_lock(&proxy_dev->buf_lock);

        if (!(proxy_dev->state & STATE_OPENED_FLAG)) {
                mutex_unlock(&proxy_dev->buf_lock);
                return -EPIPE;
        }

        len = proxy_dev->req_len;

        if (count < len) {
                mutex_unlock(&proxy_dev->buf_lock);
                pr_debug("Invalid size in recv: count=%zd, req_len=%zd\n",
                         count, len);
                return -EIO;
        }

        rc = copy_to_user(buf, proxy_dev->buffer, len);
        memset(proxy_dev->buffer, 0, len);
        proxy_dev->req_len = 0;

        if (!rc)
                proxy_dev->state |= STATE_WAIT_RESPONSE_FLAG;

        mutex_unlock(&proxy_dev->buf_lock);

        if (rc)
                return -EFAULT;

        return len;
}

/**
 * vtpm_proxy_fops_write - Write TPM responses on 'server side'
 *
 * Return value:
 *      Number of bytes read or negative error value
 */
static ssize_t vtpm_proxy_fops_write(struct file *filp, const char __user *buf,
                                     size_t count, loff_t *off)
{
        struct proxy_dev *proxy_dev = filp->private_data;

        mutex_lock(&proxy_dev->buf_lock);

        if (!(proxy_dev->state & STATE_OPENED_FLAG)) {
                mutex_unlock(&proxy_dev->buf_lock);
                return -EPIPE;
        }

        if (count > sizeof(proxy_dev->buffer) ||
            !(proxy_dev->state & STATE_WAIT_RESPONSE_FLAG)) {
                mutex_unlock(&proxy_dev->buf_lock);
                return -EIO;
        }

        proxy_dev->state &= ~STATE_WAIT_RESPONSE_FLAG;

        proxy_dev->req_len = 0;

        if (copy_from_user(proxy_dev->buffer, buf, count)) {
                mutex_unlock(&proxy_dev->buf_lock);
                return -EFAULT;
        }

        proxy_dev->resp_len = count;

        mutex_unlock(&proxy_dev->buf_lock);

        wake_up_interruptible(&proxy_dev->wq);

        return count;
}

/*
 * vtpm_proxy_fops_poll: Poll status on 'server side'
 *
 * Return value:
 *      Poll flags
 */
static unsigned int vtpm_proxy_fops_poll(struct file *filp, poll_table *wait)
{
        struct proxy_dev *proxy_dev = filp->private_data;
        unsigned ret;

        poll_wait(filp, &proxy_dev->wq, wait);

        ret = POLLOUT;

        mutex_lock(&proxy_dev->buf_lock);

        if (proxy_dev->req_len)
                ret |= POLLIN | POLLRDNORM;

        if (!(proxy_dev->state & STATE_OPENED_FLAG))
                ret |= POLLHUP;

        mutex_unlock(&proxy_dev->buf_lock);

        return ret;
}

/*
 * vtpm_proxy_fops_open - Open vTPM device on 'server side'
 *
 * Called when setting up the anonymous file descriptor
 */
static void vtpm_proxy_fops_open(struct file *filp)
{
        struct proxy_dev *proxy_dev = filp->private_data;

        proxy_dev->state |= STATE_OPENED_FLAG;
}

/**
 * vtpm_proxy_fops_undo_open - counter-part to vtpm_fops_open
 *
 * Call to undo vtpm_proxy_fops_open
 */
static void vtpm_proxy_fops_undo_open(struct proxy_dev *proxy_dev)
{
        mutex_lock(&proxy_dev->buf_lock);

        proxy_dev->state &= ~STATE_OPENED_FLAG;

        mutex_unlock(&proxy_dev->buf_lock);

        /* no more TPM responses -- wake up anyone waiting for them */
        wake_up_interruptible(&proxy_dev->wq);
}

/*
 * vtpm_proxy_fops_release: Close 'server side'
 *
 * Return value:
 *      Always returns 0.
 */
static int vtpm_proxy_fops_release(struct inode *inode, struct file *filp)
{
        struct proxy_dev *proxy_dev = filp->private_data;

        filp->private_data = NULL;

        vtpm_proxy_delete_device(proxy_dev);

        return 0;
}

static const struct file_operations vtpm_proxy_fops = {
        .owner = THIS_MODULE,
        .llseek = no_llseek,
        .read = vtpm_proxy_fops_read,
        .write = vtpm_proxy_fops_write,
        .poll = vtpm_proxy_fops_poll,
        .release = vtpm_proxy_fops_release,
};

/*
 * Functions invoked by the core TPM driver to send TPM commands to
 * 'server side' and receive responses from there.
 */

/*
 * Called when core TPM driver reads TPM responses from 'server side'
 *
 * Return value:
 *      Number of TPM response bytes read, negative error value otherwise
 */
static int vtpm_proxy_tpm_op_recv(struct tpm_chip *chip, u8 *buf, size_t count)
{
        struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
        size_t len;

        /* process gone ? */
        mutex_lock(&proxy_dev->buf_lock);

        if (!(proxy_dev->state & STATE_OPENED_FLAG)) {
                mutex_unlock(&proxy_dev->buf_lock);
                return -EPIPE;
        }

        len = proxy_dev->resp_len;
        if (count < len) {
                dev_err(&chip->dev,
                        "Invalid size in recv: count=%zd, resp_len=%zd\n",
                        count, len);
                len = -EIO;
                goto out;
        }

        memcpy(buf, proxy_dev->buffer, len);
        proxy_dev->resp_len = 0;

out:
        mutex_unlock(&proxy_dev->buf_lock);

        return len;
}

/*
 * Called when core TPM driver forwards TPM requests to 'server side'.
 *
 * Return value:
 *      0 in case of success, negative error value otherwise.
 */
static int vtpm_proxy_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t count)
{
        struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
        int rc = 0;

        if (count > sizeof(proxy_dev->buffer)) {
                dev_err(&chip->dev,
                        "Invalid size in send: count=%zd, buffer size=%zd\n",
                        count, sizeof(proxy_dev->buffer));
                return -EIO;
        }

        mutex_lock(&proxy_dev->buf_lock);

        if (!(proxy_dev->state & STATE_OPENED_FLAG)) {
                mutex_unlock(&proxy_dev->buf_lock);
                return -EPIPE;
        }

        proxy_dev->resp_len = 0;

        proxy_dev->req_len = count;
        memcpy(proxy_dev->buffer, buf, count);

        proxy_dev->state &= ~STATE_WAIT_RESPONSE_FLAG;

        mutex_unlock(&proxy_dev->buf_lock);

        wake_up_interruptible(&proxy_dev->wq);

        return rc;
}

static void vtpm_proxy_tpm_op_cancel(struct tpm_chip *chip)
{
        /* not supported */
}

static u8 vtpm_proxy_tpm_op_status(struct tpm_chip *chip)
{
        struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);

        if (proxy_dev->resp_len)
                return VTPM_PROXY_REQ_COMPLETE_FLAG;

        return 0;
}

static bool vtpm_proxy_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
{
        struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
        bool ret;

        mutex_lock(&proxy_dev->buf_lock);

        ret = !(proxy_dev->state & STATE_OPENED_FLAG);

        mutex_unlock(&proxy_dev->buf_lock);

        return ret;
}

static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
        .flags = TPM_OPS_AUTO_STARTUP,
        .recv = vtpm_proxy_tpm_op_recv,
        .send = vtpm_proxy_tpm_op_send,
        .cancel = vtpm_proxy_tpm_op_cancel,
        .status = vtpm_proxy_tpm_op_status,
        .req_complete_mask = VTPM_PROXY_REQ_COMPLETE_FLAG,
        .req_complete_val = VTPM_PROXY_REQ_COMPLETE_FLAG,
        .req_canceled = vtpm_proxy_tpm_req_canceled,
};

/*
 * Code related to the startup of the TPM 2 and startup of TPM 1.2 +
 * retrieval of timeouts and durations.
 */

static void vtpm_proxy_work(struct work_struct *work)
{
        struct proxy_dev *proxy_dev = container_of(work, struct proxy_dev,
                                                   work);
        int rc;

        rc = tpm_chip_register(proxy_dev->chip);
        if (rc)
                goto err;

        return;

err:
        vtpm_proxy_fops_undo_open(proxy_dev);
}

/*
 * vtpm_proxy_work_stop: make sure the work has finished
 *
 * This function is useful when user space closed the fd
 * while the driver still determines timeouts.
 */
static void vtpm_proxy_work_stop(struct proxy_dev *proxy_dev)
{
        vtpm_proxy_fops_undo_open(proxy_dev);
        flush_work(&proxy_dev->work);
}

/*
 * vtpm_proxy_work_start: Schedule the work for TPM 1.2 & 2 initialization
 */
static inline void vtpm_proxy_work_start(struct proxy_dev *proxy_dev)
{
        queue_work(workqueue, &proxy_dev->work);
}

/*
 * Code related to creation and deletion of device pairs
 */
static struct proxy_dev *vtpm_proxy_create_proxy_dev(void)
{
        struct proxy_dev *proxy_dev;
        struct tpm_chip *chip;
        int err;

        proxy_dev = kzalloc(sizeof(*proxy_dev), GFP_KERNEL);
        if (proxy_dev == NULL)
                return ERR_PTR(-ENOMEM);

        init_waitqueue_head(&proxy_dev->wq);
        mutex_init(&proxy_dev->buf_lock);
        INIT_WORK(&proxy_dev->work, vtpm_proxy_work);

        chip = tpm_chip_alloc(NULL, &vtpm_proxy_tpm_ops);
        if (IS_ERR(chip)) {
                err = PTR_ERR(chip);
                goto err_proxy_dev_free;
        }
        dev_set_drvdata(&chip->dev, proxy_dev);

        proxy_dev->chip = chip;

        return proxy_dev;

err_proxy_dev_free:
        kfree(proxy_dev);

        return ERR_PTR(err);
}

/*
 * Undo what has been done in vtpm_create_proxy_dev
 */
static inline void vtpm_proxy_delete_proxy_dev(struct proxy_dev *proxy_dev)
{
        put_device(&proxy_dev->chip->dev); /* frees chip */
        kfree(proxy_dev);
}

/*
 * Create a /dev/tpm%d and 'server side' file descriptor pair
 *
 * Return value:
 *      Returns file pointer on success, an error value otherwise
 */
static struct file *vtpm_proxy_create_device(
                                 struct vtpm_proxy_new_dev *vtpm_new_dev)
{
        struct proxy_dev *proxy_dev;
        int rc, fd;
        struct file *file;

        if (vtpm_new_dev->flags & ~VTPM_PROXY_FLAGS_ALL)
                return ERR_PTR(-EOPNOTSUPP);

        proxy_dev = vtpm_proxy_create_proxy_dev();
        if (IS_ERR(proxy_dev))
                return ERR_CAST(proxy_dev);

        proxy_dev->flags = vtpm_new_dev->flags;

        /* setup an anonymous file for the server-side */
        fd = get_unused_fd_flags(O_RDWR);
        if (fd < 0) {
                rc = fd;
                goto err_delete_proxy_dev;
        }

        file = anon_inode_getfile("[vtpms]", &vtpm_proxy_fops, proxy_dev,
                                  O_RDWR);
        if (IS_ERR(file)) {
                rc = PTR_ERR(file);
                goto err_put_unused_fd;
        }

        /* from now on we can unwind with put_unused_fd() + fput() */
        /* simulate an open() on the server side */
        vtpm_proxy_fops_open(file);

        if (proxy_dev->flags & VTPM_PROXY_FLAG_TPM2)
                proxy_dev->chip->flags |= TPM_CHIP_FLAG_TPM2;

        vtpm_proxy_work_start(proxy_dev);

        vtpm_new_dev->fd = fd;
        vtpm_new_dev->major = MAJOR(proxy_dev->chip->dev.devt);
        vtpm_new_dev->minor = MINOR(proxy_dev->chip->dev.devt);
        vtpm_new_dev->tpm_num = proxy_dev->chip->dev_num;

        return file;

err_put_unused_fd:
        put_unused_fd(fd);

err_delete_proxy_dev:
        vtpm_proxy_delete_proxy_dev(proxy_dev);

        return ERR_PTR(rc);
}

/*
 * Counter part to vtpm_create_device.
 */
static void vtpm_proxy_delete_device(struct proxy_dev *proxy_dev)
{
        vtpm_proxy_work_stop(proxy_dev);

        /*
         * A client may hold the 'ops' lock, so let it know that the server
         * side shuts down before we try to grab the 'ops' lock when
         * unregistering the chip.
         */
        vtpm_proxy_fops_undo_open(proxy_dev);

        tpm_chip_unregister(proxy_dev->chip);

        vtpm_proxy_delete_proxy_dev(proxy_dev);
}

/*
 * Code related to the control device /dev/vtpmx
 */

/*
 * vtpmx_fops_ioctl: ioctl on /dev/vtpmx
 *
 * Return value:
 *      Returns 0 on success, a negative error code otherwise.
 */
static long vtpmx_fops_ioctl(struct file *f, unsigned int ioctl,
                                   unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        struct vtpm_proxy_new_dev __user *vtpm_new_dev_p;
        struct vtpm_proxy_new_dev vtpm_new_dev;
        struct file *file;

        switch (ioctl) {
        case VTPM_PROXY_IOC_NEW_DEV:
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                vtpm_new_dev_p = argp;
                if (copy_from_user(&vtpm_new_dev, vtpm_new_dev_p,
                                   sizeof(vtpm_new_dev)))
                        return -EFAULT;
                file = vtpm_proxy_create_device(&vtpm_new_dev);
                if (IS_ERR(file))
                        return PTR_ERR(file);
                if (copy_to_user(vtpm_new_dev_p, &vtpm_new_dev,
                                 sizeof(vtpm_new_dev))) {
                        put_unused_fd(vtpm_new_dev.fd);
                        fput(file);
                        return -EFAULT;
                }

                fd_install(vtpm_new_dev.fd, file);
                return 0;

        default:
                return -ENOIOCTLCMD;
        }
}

#ifdef CONFIG_COMPAT
static long vtpmx_fops_compat_ioctl(struct file *f, unsigned int ioctl,
                                          unsigned long arg)
{
        return vtpmx_fops_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
}
#endif

static const struct file_operations vtpmx_fops = {
        .owner = THIS_MODULE,
        .unlocked_ioctl = vtpmx_fops_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = vtpmx_fops_compat_ioctl,
#endif
        .llseek = noop_llseek,
};

static struct miscdevice vtpmx_miscdev = {
        .minor = MISC_DYNAMIC_MINOR,
        .name = "vtpmx",
        .fops = &vtpmx_fops,
};

static int vtpmx_init(void)
{
        return misc_register(&vtpmx_miscdev);
}

static void vtpmx_cleanup(void)
{
        misc_deregister(&vtpmx_miscdev);
}

static int __init vtpm_module_init(void)
{
        int rc;

        rc = vtpmx_init();
        if (rc) {
                pr_err("couldn't create vtpmx device\n");
                return rc;
        }

        workqueue = create_workqueue("tpm-vtpm");
        if (!workqueue) {
                pr_err("couldn't create workqueue\n");
                rc = -ENOMEM;
                goto err_vtpmx_cleanup;
        }

        return 0;

err_vtpmx_cleanup:
        vtpmx_cleanup();

        return rc;
}

static void __exit vtpm_module_exit(void)
{
        destroy_workqueue(workqueue);
        vtpmx_cleanup();
}

module_init(vtpm_module_init);
module_exit(vtpm_module_exit);

MODULE_AUTHOR("Stefan Berger (stefanb@us.ibm.com)");
MODULE_DESCRIPTION("vTPM Driver");
MODULE_VERSION("0.1");
MODULE_LICENSE("GPL");