README.txt


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README.txt for version 8.2 of Vim: Vi IMproved.


WHAT IS VIM?

Vim is a greatly improved version of the good old UNIX editor Vi.  Many new
features have been added: multi-level undo, syntax highlighting, command line
history, on-line help, spell checking, filename completion, block operations,
script language, etc.  There is also a Graphical User Interface (GUI)
available.  Still, Vi compatibility is maintained, those who have Vi "in the
fingers" will feel at home.  See "runtime/doc/vi_diff.txt" for differences with
Vi.

This editor is very useful for editing programs and other plain text files.
All commands are given with normal keyboard characters, so those who can type
with ten fingers can work very fast.  Additionally, function keys can be
mapped to commands by the user, and the mouse can be used.

Vim runs under MS-Windows (XP, Vista, 7, 8, 10), macOS, VMS and almost all
flavours of UNIX.  Porting to other systems should not be very difficult.
Older versions of Vim run on MS-DOS, MS-Windows 95/98/Me/NT/2000, Amiga DOS,
Atari MiNT, BeOS, RISC OS and OS/2.  These are no longer maintained.


DISTRIBUTION

You can often use your favorite package manager to install Vim.  On Mac and
Linux a small version of Vim is pre-installed, you still need to install Vim
if you want more features.

There are separate distributions for Unix, PC, Amiga and some other systems.
This README.txt file comes with the runtime archive.  It includes the
documentation, syntax files and other files that are used at runtime.  To run
Vim you must get either one of the binary archives or a source archive.
Which one you need depends on the system you want to run it on and whether you
want or must compile it yourself.  Check "https://www.vim.org/download.php" for
an overview of currently available distributions.

Some popular places to get the latest Vim:
* Check out the git repository from github: https://github.com/vim/vim.
* Get the source code as an archive: https://github.com/vim/vim/releases.
* Get a Windows executable from the vim-win32-installer repository:
  https://github.com/vim/vim-win32-installer/releases.


COMPILING

If you obtained a binary distribution you don't need to compile Vim.  If you
obtained a source distribution, all the stuff for compiling Vim is in the
"src" directory.  See src/INSTALL for instructions.


INSTALLATION

See one of these files for system-specific instructions.  Either in the
READMEdir directory (in the repository) or the top directory (if you unpack an
archive):

README_ami.txt		Amiga
README_unix.txt		Unix
README_dos.txt		MS-DOS and MS-Windows
README_mac.txt		Macintosh
README_vms.txt		VMS

There are more README_*.txt files, depending on the distribution you used.


DOCUMENTATION

The Vim tutor is a one hour training course for beginners.  Often it can be
started as "vimtutor".  See ":help tutor" for more information.

The best is to use ":help" in Vim.  If you don't have an executable yet, read
"runtime/doc/help.txt".  It contains pointers to the other documentation
files.  The User Manual reads like a book and is recommended to learn to use
Vim.  See ":help user-manual".


COPYING

Vim is Charityware.  You can use and copy it as much as you like, but you are
encouraged to make a donation to help orphans in Uganda.  Please read the file
"runtime/doc/uganda.txt" for details (do ":help uganda" inside Vim).

Summary of the license: There are no restrictions on using or distributing an
unmodified copy of Vim.  Parts of Vim may also be distributed, but the license
text must always be included.  For modified versions a few restrictions apply.
The license is GPL compatible, you may compile Vim with GPL libraries and
distribute it.


SPONSORING

Fixing bugs and adding new features takes a lot of time and effort.  To show
your appreciation for the work and motivate Bram and others to continue
working on Vim please send a donation.

Since Bram is back to a paid job the money will now be used to help children
in Uganda.  See runtime/doc/uganda.txt.  But at the same time donations
increase Bram's motivation to keep working on Vim!

For the most recent information about sponsoring look on the Vim web site:

	https://www.vim.org/sponsor/


CONTRIBUTING

If you would like to help making Vim better, see the CONTRIBUTING.md file.


INFORMATION

The latest news about Vim can be found on the Vim home page:
	https://www.vim.org/

If you have problems, have a look at the Vim documentation or tips:
	https://www.vim.org/docs.php
	https://vim.fandom.com/wiki/Vim_Tips_Wiki

If you still have problems or any other questions, use one of the mailing
lists to discuss them with Vim users and developers:
	https://www.vim.org/maillist.php

If nothing else works, report bugs directly:
	Bram Moolenaar <Bram@vim.org>


MAIN AUTHOR

Send any other comments, patches, flowers and suggestions to:

	Bram Moolenaar		E-mail:	Bram@vim.org
/******************************************************************************
 * evtchn.c
 *
 * Driver for receiving and demuxing event-channel signals.
 *
 * Copyright (c) 2004-2005, K A Fraser
 * Multi-process extensions Copyright (c) 2004, Steven Smith
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/major.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/cpu.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>

#include <xen/xen.h>
#include <xen/events.h>
#include <xen/evtchn.h>
#include <asm/xen/hypervisor.h>

struct per_user_data {
	struct mutex bind_mutex; /* serialize bind/unbind operations */
	struct rb_root evtchns;
	unsigned int nr_evtchns;

	/* Notification ring, accessed via /dev/xen/evtchn. */
	unsigned int ring_size;
	evtchn_port_t *ring;
	unsigned int ring_cons, ring_prod, ring_overflow;
	struct mutex ring_cons_mutex; /* protect against concurrent readers */
	spinlock_t ring_prod_lock; /* product against concurrent interrupts */

	/* Processes wait on this queue when ring is empty. */
	wait_queue_head_t evtchn_wait;
	struct fasync_struct *evtchn_async_queue;
	const char *name;
};

struct user_evtchn {
	struct rb_node node;
	struct per_user_data *user;
	unsigned port;
	bool enabled;
};

static evtchn_port_t *evtchn_alloc_ring(unsigned int size)
{
	evtchn_port_t *ring;
	size_t s = size * sizeof(*ring);

	ring = kmalloc(s, GFP_KERNEL);
	if (!ring)
		ring = vmalloc(s);

	return ring;
}

static void evtchn_free_ring(evtchn_port_t *ring)
{
	kvfree(ring);
}

static unsigned int evtchn_ring_offset(struct per_user_data *u,
				       unsigned int idx)
{
	return idx & (u->ring_size - 1);
}

static evtchn_port_t *evtchn_ring_entry(struct per_user_data *u,
					unsigned int idx)
{
	return u->ring + evtchn_ring_offset(u, idx);
}

static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
{
	struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;

	u->nr_evtchns++;

	while (*new) {
		struct user_evtchn *this;

		this = container_of(*new, struct user_evtchn, node);

		parent = *new;
		if (this->port < evtchn->port)
			new = &((*new)->rb_left);
		else if (this->port > evtchn->port)
			new = &((*new)->rb_right);
		else
			return -EEXIST;
	}

	/* Add new node and rebalance tree. */
	rb_link_node(&evtchn->node, parent, new);
	rb_insert_color(&evtchn->node, &u->evtchns);

	return 0;
}

static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
{
	u->nr_evtchns--;
	rb_erase(&evtchn->node, &u->evtchns);
	kfree(evtchn);
}

static struct user_evtchn *find_evtchn(struct per_user_data *u, unsigned port)
{
	struct rb_node *node = u->evtchns.rb_node;

	while (node) {
		struct user_evtchn *evtchn;

		evtchn = container_of(node, struct user_evtchn, node);

		if (evtchn->port < port)
			node = node->rb_left;
		else if (evtchn->port > port)
			node = node->rb_right;
		else
			return evtchn;
	}
	return NULL;
}

static irqreturn_t evtchn_interrupt(int irq, void *data)
{
	struct user_evtchn *evtchn = data;
	struct per_user_data *u = evtchn->user;

	WARN(!evtchn->enabled,
	     "Interrupt for port %d, but apparently not enabled; per-user %p\n",
	     evtchn->port, u);

	disable_irq_nosync(irq);
	evtchn->enabled = false;

	spin_lock(&u->ring_prod_lock);

	if ((u->ring_prod - u->ring_cons) < u->ring_size) {
		*evtchn_ring_entry(u, u->ring_prod) = evtchn->port;
		wmb(); /* Ensure ring contents visible */
		if (u->ring_cons == u->ring_prod++) {
			wake_up_interruptible(&u->evtchn_wait);
			kill_fasync(&u->evtchn_async_queue,
				    SIGIO, POLL_IN);
		}
	} else
		u->ring_overflow = 1;

	spin_unlock(&u->ring_prod_lock);

	return IRQ_HANDLED;
}

static ssize_t evtchn_read(struct file *file, char __user *buf,
			   size_t count, loff_t *ppos)
{
	int rc;
	unsigned int c, p, bytes1 = 0, bytes2 = 0;
	struct per_user_data *u = file->private_data;

	/* Whole number of ports. */
	count &= ~(sizeof(evtchn_port_t)-1);

	if (count == 0)
		return 0;

	if (count > PAGE_SIZE)
		count = PAGE_SIZE;

	for (;;) {
		mutex_lock(&u->ring_cons_mutex);

		rc = -EFBIG;
		if (u->ring_overflow)
			goto unlock_out;

		c = u->ring_cons;
		p = u->ring_prod;
		if (c != p)
			break;

		mutex_unlock(&u->ring_cons_mutex);

		if (file->f_flags & O_NONBLOCK)
			return -EAGAIN;

		rc = wait_event_interruptible(u->evtchn_wait,