// 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!\n",
				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\n",
				__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\n",
			__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.\n",
			__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\n",
			__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.\n", __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\n",
		       __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\n", status);
		goto out1;
	}
	
	status = register_filesystem(&coda_fs_type);
	if (status) {
		pr_warn("failed to register filesystem!\n");
		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\n");
	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);