// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *      	An implementation of a loadable kernel mode driver providing
   *		multiple kernel/user space bidirectional communications links.
   *

   * 		Author: 	Alan Cox <alan@lxorguk.ukuu.org.uk>

   * 
   *              Adapted to become the Linux 2.0 Coda pseudo device
   *              Peter  Braam  <braam@maths.ox.ac.uk> 
   *              Michael Callahan <mjc@emmy.smith.edu>           
   *
   *              Changes for Linux 2.1
   *              Copyright (c) 1997 Carnegie-Mellon University
   */
  
  #include <linux/module.h>
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/major.h>
  #include <linux/time.h>

  #include <linux/sched/signal.h>

  #include <linux/slab.h>
  #include <linux/ioport.h>
  #include <linux/fcntl.h>
  #include <linux/delay.h>
  #include <linux/skbuff.h>
  #include <linux/proc_fs.h>

  #include <linux/vmalloc.h>
  #include <linux/fs.h>
  #include <linux/file.h>
  #include <linux/poll.h>
  #include <linux/init.h>
  #include <linux/list.h>

  #include <linux/mutex.h>

  #include <linux/device.h>

  #include <linux/pid_namespace.h>

  #include <asm/io.h>

  #include <linux/uaccess.h>

  
  #include <linux/coda.h>

  #include "coda_psdev.h"

  #include "coda_linux.h"

  #include "coda_int.h"

  /* statistics */
  int           coda_hard;         /* allows signals during upcalls */
  unsigned long coda_timeout = 30; /* .. secs, then signals will dequeue */
  
  
  struct venus_comm coda_comms[MAX_CODADEVS];

  static struct class *coda_psdev_class;

  
  /*
   * Device operations
   */

  static __poll_t coda_psdev_poll(struct file *file, poll_table * wait)

  {
          struct venus_comm *vcp = (struct venus_comm *) file->private_data;

  	__poll_t mask = EPOLLOUT | EPOLLWRNORM;

  
  	poll_wait(file, &vcp->vc_waitq, wait);

  	mutex_lock(&vcp->vc_mutex);

  	if (!list_empty(&vcp->vc_pending))

                  mask |= EPOLLIN | EPOLLRDNORM;

  	mutex_unlock(&vcp->vc_mutex);

  
  	return mask;
  }

  static long coda_psdev_ioctl(struct file * filp, unsigned int cmd, unsigned long arg)

  {
  	unsigned int data;
  
  	switch(cmd) {
  	case CIOC_KERNEL_VERSION:
  		data = CODA_KERNEL_VERSION;
  		return put_user(data, (int __user *) arg);
  	default:
  		return -ENOTTY;
  	}
  
  	return 0;
  }
  
  /*
   *	Receive a message written by Venus to the psdev
   */
   
  static ssize_t coda_psdev_write(struct file *file, const char __user *buf, 
  				size_t nbytes, loff_t *off)
  {
          struct venus_comm *vcp = (struct venus_comm *) file->private_data;
          struct upc_req *req = NULL;
          struct upc_req *tmp;
  	struct list_head *lh;
  	struct coda_in_hdr hdr;
  	ssize_t retval = 0, count = 0;
  	int error;

  	/* make sure there is enough to copy out the (opcode, unique) values */
  	if (nbytes < (2 * sizeof(u_int32_t)))
  		return -EINVAL;

          /* Peek at the opcode, uniquefier */

  	if (copy_from_user(&hdr, buf, 2 * sizeof(u_int32_t)))

  	        return -EFAULT;
  
          if (DOWNCALL(hdr.opcode)) {

  		union outputArgs *dcbuf;

  		int size = sizeof(*dcbuf);

  		if  ( nbytes < sizeof(struct coda_out_hdr) ) {

  			pr_warn("coda_downcall opc %d uniq %d, not enough!
  ",
  				hdr.opcode, hdr.unique);

  			count = nbytes;
  			goto out;
  		}
  		if ( nbytes > size ) {

  			pr_warn("downcall opc %d, uniq %d, too much!",

  				hdr.opcode, hdr.unique);

  		        nbytes = size;
  		}

  		dcbuf = kvmalloc(nbytes, GFP_KERNEL);
  		if (!dcbuf) {
  			retval = -ENOMEM;
  			goto out;
  		}

  		if (copy_from_user(dcbuf, buf, nbytes)) {

  			kvfree(dcbuf);

  			retval = -EFAULT;
  			goto out;
  		}
  
  		/* what downcall errors does Venus handle ? */

  		error = coda_downcall(vcp, hdr.opcode, dcbuf, nbytes);

  		kvfree(dcbuf);

  		if (error) {

  			pr_warn("%s: coda_downcall error: %d
  ",
  				__func__, error);

  			retval = error;
  			goto out;
  		}
  		count = nbytes;
  		goto out;
  	}
          
  	/* Look for the message on the processing queue. */

  	mutex_lock(&vcp->vc_mutex);

  	list_for_each(lh, &vcp->vc_processing) {
  		tmp = list_entry(lh, struct upc_req , uc_chain);
  		if (tmp->uc_unique == hdr.unique) {
  			req = tmp;
  			list_del(&req->uc_chain);
  			break;
  		}
  	}

  	mutex_unlock(&vcp->vc_mutex);

  
  	if (!req) {

  		pr_warn("%s: msg (%d, %d) not found
  ",
  			__func__, hdr.opcode, hdr.unique);

  		retval = -ESRCH;
  		goto out;
  	}
  
          /* move data into response buffer. */
  	if (req->uc_outSize < nbytes) {

  		pr_warn("%s: too much cnt: %d, cnt: %ld, opc: %d, uniq: %d.
  ",
  			__func__, req->uc_outSize, (long)nbytes,
  			hdr.opcode, hdr.unique);

  		nbytes = req->uc_outSize; /* don't have more space! */
  	}
          if (copy_from_user(req->uc_data, buf, nbytes)) {

  		req->uc_flags |= CODA_REQ_ABORT;

  		wake_up(&req->uc_sleep);
  		retval = -EFAULT;
  		goto out;
  	}
  
  	/* adjust outsize. is this useful ?? */

  	req->uc_outSize = nbytes;
  	req->uc_flags |= CODA_REQ_WRITE;

  	count = nbytes;
  
  	/* Convert filedescriptor into a file handle */
  	if (req->uc_opcode == CODA_OPEN_BY_FD) {
  		struct coda_open_by_fd_out *outp =
  			(struct coda_open_by_fd_out *)req->uc_data;

  		if (!outp->oh.result) {

  			outp->fh = fget(outp->fd);

  			if (!outp->fh)
  				return -EBADF;
  		}

  	}
  
          wake_up(&req->uc_sleep);
  out:
          return(count ? count : retval);  
  }
  
  /*
   *	Read a message from the kernel to Venus
   */
  
  static ssize_t coda_psdev_read(struct file * file, char __user * buf, 
  			       size_t nbytes, loff_t *off)
  {
  	DECLARE_WAITQUEUE(wait, current);
          struct venus_comm *vcp = (struct venus_comm *) file->private_data;
          struct upc_req *req;
  	ssize_t retval = 0, count = 0;
  
  	if (nbytes == 0)
  		return 0;

  	mutex_lock(&vcp->vc_mutex);

  
  	add_wait_queue(&vcp->vc_waitq, &wait);
  	set_current_state(TASK_INTERRUPTIBLE);
  
  	while (list_empty(&vcp->vc_pending)) {
  		if (file->f_flags & O_NONBLOCK) {
  			retval = -EAGAIN;
  			break;
  		}
  		if (signal_pending(current)) {
  			retval = -ERESTARTSYS;
  			break;
  		}

  		mutex_unlock(&vcp->vc_mutex);

  		schedule();

  		mutex_lock(&vcp->vc_mutex);

  	}
  
  	set_current_state(TASK_RUNNING);
  	remove_wait_queue(&vcp->vc_waitq, &wait);
  
  	if (retval)
  		goto out;
  
  	req = list_entry(vcp->vc_pending.next, struct upc_req,uc_chain);
  	list_del(&req->uc_chain);
  
  	/* Move the input args into userspace */
  	count = req->uc_inSize;
  	if (nbytes < req->uc_inSize) {

  		pr_warn("%s: Venus read %ld bytes of %d in message
  ",
  			__func__, (long)nbytes, req->uc_inSize);

  		count = nbytes;
          }
  
  	if (copy_to_user(buf, req->uc_data, count))
  	        retval = -EFAULT;
          
  	/* If request was not a signal, enqueue and don't free */

  	if (!(req->uc_flags & CODA_REQ_ASYNC)) {
  		req->uc_flags |= CODA_REQ_READ;

  		list_add_tail(&(req->uc_chain), &vcp->vc_processing);

  		goto out;
  	}

  	kvfree(req->uc_data);

  	kfree(req);

  out:

  	mutex_unlock(&vcp->vc_mutex);

  	return (count ? count : retval);
  }
  
  static int coda_psdev_open(struct inode * inode, struct file * file)
  {

  	struct venus_comm *vcp;
  	int idx, err;

  	if (task_active_pid_ns(current) != &init_pid_ns)
  		return -EINVAL;

  	if (current_user_ns() != &init_user_ns)
  		return -EINVAL;

  	idx = iminor(inode);

  	if (idx < 0 || idx >= MAX_CODADEVS)

  		return -ENODEV;

  	err = -EBUSY;

  	vcp = &coda_comms[idx];

  	mutex_lock(&vcp->vc_mutex);

  	if (!vcp->vc_inuse) {
  		vcp->vc_inuse++;

  		INIT_LIST_HEAD(&vcp->vc_pending);
  		INIT_LIST_HEAD(&vcp->vc_processing);
  		init_waitqueue_head(&vcp->vc_waitq);
  		vcp->vc_sb = NULL;
  		vcp->vc_seq = 0;

  
  		file->private_data = vcp;
  		err = 0;

  	}

  	mutex_unlock(&vcp->vc_mutex);

  	return err;

  }
  
  
  static int coda_psdev_release(struct inode * inode, struct file * file)
  {

  	struct venus_comm *vcp = (struct venus_comm *) file->private_data;
  	struct upc_req *req, *tmp;

  	if (!vcp || !vcp->vc_inuse ) {

  		pr_warn("%s: Not open.
  ", __func__);

  		return -1;
  	}

  	mutex_lock(&vcp->vc_mutex);

  
  	/* Wakeup clients so they can return. */

  	list_for_each_entry_safe(req, tmp, &vcp->vc_pending, uc_chain) {

  		list_del(&req->uc_chain);

  		/* Async requests need to be freed here */

  		if (req->uc_flags & CODA_REQ_ASYNC) {

  			kvfree(req->uc_data);

  			kfree(req);

  			continue;
  		}

  		req->uc_flags |= CODA_REQ_ABORT;

  		wake_up(&req->uc_sleep);

  	}
  
  	list_for_each_entry_safe(req, tmp, &vcp->vc_processing, uc_chain) {
  		list_del(&req->uc_chain);

  		req->uc_flags |= CODA_REQ_ABORT;

  		wake_up(&req->uc_sleep);
  	}

  	file->private_data = NULL;
  	vcp->vc_inuse--;

  	mutex_unlock(&vcp->vc_mutex);

  	return 0;
  }

  static const struct file_operations coda_psdev_fops = {

  	.owner		= THIS_MODULE,
  	.read		= coda_psdev_read,
  	.write		= coda_psdev_write,
  	.poll		= coda_psdev_poll,

  	.unlocked_ioctl	= coda_psdev_ioctl,

  	.open		= coda_psdev_open,
  	.release	= coda_psdev_release,

  	.llseek		= noop_llseek,

  };

  static int __init init_coda_psdev(void)

  {
  	int i, err = 0;
  	if (register_chrdev(CODA_PSDEV_MAJOR, "coda", &coda_psdev_fops)) {

  		pr_err("%s: unable to get major %d
  ",
  		       __func__, CODA_PSDEV_MAJOR);

  		return -EIO;

  	}

  	coda_psdev_class = class_create(THIS_MODULE, "coda");

  	if (IS_ERR(coda_psdev_class)) {
  		err = PTR_ERR(coda_psdev_class);
  		goto out_chrdev;
  	}		

  	for (i = 0; i < MAX_CODADEVS; i++) {
  		mutex_init(&(&coda_comms[i])->vc_mutex);

  		device_create(coda_psdev_class, NULL,
  			      MKDEV(CODA_PSDEV_MAJOR, i), NULL, "cfs%d", i);

  	}

  	coda_sysctl_init();
  	goto out;

  out_chrdev:
  	unregister_chrdev(CODA_PSDEV_MAJOR, "coda");
  out:
  	return err;
  }

  MODULE_AUTHOR("Jan Harkes, Peter J. Braam");
  MODULE_DESCRIPTION("Coda Distributed File System VFS interface");
  MODULE_ALIAS_CHARDEV_MAJOR(CODA_PSDEV_MAJOR);

  MODULE_LICENSE("GPL");

  MODULE_VERSION("7.0");

  static int __init init_coda(void)
  {
  	int status;
  	int i;

  
  	status = coda_init_inodecache();
  	if (status)
  		goto out2;
  	status = init_coda_psdev();
  	if ( status ) {

  		pr_warn("Problem (%d) in init_coda_psdev
  ", status);

  		goto out1;
  	}
  	
  	status = register_filesystem(&coda_fs_type);
  	if (status) {

  		pr_warn("failed to register filesystem!
  ");

  		goto out;
  	}
  	return 0;
  out:

  	for (i = 0; i < MAX_CODADEVS; i++)

  		device_destroy(coda_psdev_class, MKDEV(CODA_PSDEV_MAJOR, i));

  	class_destroy(coda_psdev_class);

  	unregister_chrdev(CODA_PSDEV_MAJOR, "coda");
  	coda_sysctl_clean();
  out1:
  	coda_destroy_inodecache();
  out2:
  	return status;
  }
  
  static void __exit exit_coda(void)
  {
          int err, i;
  
  	err = unregister_filesystem(&coda_fs_type);

  	if (err != 0)

  		pr_warn("failed to unregister filesystem
  ");

  	for (i = 0; i < MAX_CODADEVS; i++)

  		device_destroy(coda_psdev_class, MKDEV(CODA_PSDEV_MAJOR, i));

  	class_destroy(coda_psdev_class);

  	unregister_chrdev(CODA_PSDEV_MAJOR, "coda");
  	coda_sysctl_clean();
  	coda_destroy_inodecache();
  }
  
  module_init(init_coda);
  module_exit(exit_coda);