line.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 */

#include <linux/irqreturn.h>
#include <linux/kd.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>

#include "chan.h"
#include <irq_kern.h>
#include <irq_user.h>
#include <kern_util.h>
#include <os.h>

#define LINE_BUFSIZE 4096

static irqreturn_t line_interrupt(int irq, void *data)
{
	struct chan *chan = data;
	struct line *line = chan->line;

	if (line)
		chan_interrupt(line, irq);

	return IRQ_HANDLED;
}

/*
 * Returns the free space inside the ring buffer of this line.
 *
 * Should be called while holding line->lock (this does not modify data).
 */
static unsigned int write_room(struct line *line)
{
	int n;

	if (line->buffer == NULL)
		return LINE_BUFSIZE - 1;

	/* This is for the case where the buffer is wrapped! */
	n = line->head - line->tail;

	if (n <= 0)
		n += LINE_BUFSIZE; /* The other case */
	return n - 1;
}

unsigned int line_write_room(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;
	unsigned long flags;
	unsigned int room;

	spin_lock_irqsave(&line->lock, flags);
	room = write_room(line);
	spin_unlock_irqrestore(&line->lock, flags);

	return room;
}

unsigned int line_chars_in_buffer(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;
	unsigned long flags;
	unsigned int ret;

	spin_lock_irqsave(&line->lock, flags);
	/* write_room subtracts 1 for the needed NULL, so we readd it.*/
	ret = LINE_BUFSIZE - (write_room(line) + 1);
	spin_unlock_irqrestore(&line->lock, flags);

	return ret;
}

/*
 * This copies the content of buf into the circular buffer associated with
 * this line.
 * The return value is the number of characters actually copied, i.e. the ones
 * for which there was space: this function is not supposed to ever flush out
 * the circular buffer.
 *
 * Must be called while holding line->lock!
 */
static int buffer_data(struct line *line, const u8 *buf, size_t len)
{
	int end, room;

	if (line->buffer == NULL) {
		line->buffer = kmalloc(LINE_BUFSIZE, GFP_ATOMIC);
		if (line->buffer == NULL) {
			printk(KERN_ERR "buffer_data - atomic allocation "
			       "failed\n");
			return 0;
		}
		line->head = line->buffer;
		line->tail = line->buffer;
	}

	room = write_room(line);
	len = (len > room) ? room : len;

	end = line->buffer + LINE_BUFSIZE - line->tail;

	if (len < end) {
		memcpy(line->tail, buf, len);
		line->tail += len;
	}
	else {
		/* The circular buffer is wrapping */
		memcpy(line->tail, buf, end);
		buf += end;
		memcpy(line->buffer, buf, len - end);
		line->tail = line->buffer + len - end;
	}

	return len;
}

/*
 * Flushes the ring buffer to the output channels. That is, write_chan is
 * called, passing it line->head as buffer, and an appropriate count.
 *
 * On exit, returns 1 when the buffer is empty,
 * 0 when the buffer is not empty on exit,
 * and -errno when an error occurred.
 *
 * Must be called while holding line->lock!*/
static int flush_buffer(struct line *line)
{
	int n, count;

	if ((line->buffer == NULL) || (line->head == line->tail))
		return 1;

	if (line->tail < line->head) {
		/* line->buffer + LINE_BUFSIZE is the end of the buffer! */
		count = line->buffer + LINE_BUFSIZE - line->head;

		n = write_chan(line->chan_out, line->head, count,
			       line->write_irq);
		if (n < 0)
			return n;
		if (n == count) {
			/*
			 * We have flushed from ->head to buffer end, now we
			 * must flush only from the beginning to ->tail.
			 */
			line->head = line->buffer;
		} else {
			line->head += n;
			return 0;
		}
	}

	count = line->tail - line->head;
	n = write_chan(line->chan_out, line->head, count,
		       line->write_irq);

	if (n < 0)
		return n;

	line->head += n;
	return line->head == line->tail;
}

void line_flush_buffer(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;
	unsigned long flags;

	spin_lock_irqsave(&line->lock, flags);
	flush_buffer(line);
	spin_unlock_irqrestore(&line->lock, flags);
}

/*
 * We map both ->flush_chars and ->put_char (which go in pair) onto
 * ->flush_buffer and ->write. Hope it's not that bad.
 */
void line_flush_chars(struct tty_struct *tty)
{
	line_flush_buffer(tty);
}

ssize_t line_write(struct tty_struct *tty, const u8 *buf, size_t len)
{
	struct line *line = tty->driver_data;
	unsigned long flags;
	int n, ret = 0;

	spin_lock_irqsave(&line->lock, flags);
	if (line->head != line->tail)
		ret = buffer_data(line, buf, len);
	else {
		n = write_chan(line->chan_out, buf, len,
			       line->write_irq);
		if (n < 0) {
			ret = n;
			goto out_up;
		}

		len -= n;
		ret += n;
		if (len > 0)
			ret += buffer_data(line, buf + n, len);
	}
out_up:
	spin_unlock_irqrestore(&line->lock, flags);
	return ret;
}

void line_throttle(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;

	deactivate_chan(line->chan_in, line->read_irq);
	line->throttled = 1;
}

void line_unthrottle(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;

	line->throttled = 0;
	chan_interrupt(line, line->read_irq);
}

static irqreturn_t line_write_interrupt(int irq, void *data)
{
	struct chan *chan = data;
	struct line *line = chan->line;
	int err;

	/*
	 * Interrupts are disabled here because genirq keep irqs disabled when
	 * calling the action handler.
	 */

	spin_lock(&line->lock);
	err = flush_buffer(line);
	if (err == 0) {
		spin_unlock(&line->lock);
		return IRQ_NONE;
	} else if ((err < 0) && (err != -EAGAIN)) {
		line->head = line->buffer;
		line->tail = line->buffer;
	}
	spin_unlock(&line->lock);

	tty_port_tty_wakeup(&line->port);

	return IRQ_HANDLED;
}

int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
{
	const struct line_driver *driver = line->driver;
	int err;

	if (input) {
		err = um_request_irq(UM_IRQ_ALLOC, fd, IRQ_READ,
				     line_interrupt, 0,
				     driver->read_irq_name, data);
		if (err < 0)
			return err;

		line->read_irq = err;
	}

	if (output) {
		err = um_request_irq(UM_IRQ_ALLOC, fd, IRQ_WRITE,
				     line_write_interrupt, 0,
				     driver->write_irq_name, data);
		if (err < 0)
			return err;

		line->write_irq = err;
	}

	return 0;
}

static int line_activate(struct tty_port *port, struct tty_struct *tty)
{
	int ret;
	struct line *line = tty->driver_data;

	ret = enable_chan(line);
	if (ret)
		return ret;

	if (!line->sigio) {
		chan_enable_winch(line->chan_out, port);
		line->sigio = 1;
	}

	chan_window_size(line, &tty->winsize.ws_row,
		&tty->winsize.ws_col);

	return 0;
}

static void unregister_winch(struct tty_struct *tty);

static void line_destruct(struct tty_port *port)
{
	struct tty_struct *tty = tty_port_tty_get(port);
	struct line *line = tty->driver_data;

	if (line->sigio) {
		unregister_winch(tty);
		line->sigio = 0;
	}
}

static const struct tty_port_operations line_port_ops = {
	.activate = line_activate,
	.destruct = line_destruct,
};

int line_open(struct tty_struct *tty, struct file *filp)
{
	struct line *line = tty->driver_data;

	return tty_port_open(&line->port, tty, filp);
}

int line_install(struct tty_driver *driver, struct tty_struct *tty,
		 struct line *line)
{
	int ret;

	ret = tty_standard_install(driver, tty);
	if (ret)
		return ret;

	tty->driver_data = line;

	return 0;
}

void line_close(struct tty_struct *tty, struct file * filp)
{
	struct line *line = tty->driver_data;

	tty_port_close(&line->port, tty, filp);
}

void line_hangup(struct tty_struct *tty)
{
	struct line *line = tty->driver_data;

	tty_port_hangup(&line->port);
}

void close_lines(struct line *lines, int nlines)
{
	int i;

	for(i = 0; i < nlines; i++)
		close_chan(&lines[i]);
}

int setup_one_line(struct line *lines, int n, char *init,
		   const struct chan_opts *opts, char **error_out)
{
	struct line *line = &lines[n];
	struct tty_driver *driver = line->driver->driver;
	int err = -EINVAL;

	if (line->port.count) {
		*error_out = "Device is already open";
		goto out;
	}

	if (!strcmp(init, "none")) {
		if (line->valid) {
			line->valid = 0;
			kfree(line->init_str);
			tty_unregister_device(driver, n);
			parse_chan_pair(NULL, line, n, opts, error_out);
			err = 0;
		}
		*error_out = "configured as 'none'";
	} else {
		char *new = kstrdup(init, GFP_KERNEL);
		if (!new) {
			*error_out = "Failed to allocate memory";
			return -ENOMEM;
		}
		if (line->valid) {
			tty_unregister_device(driver, n);
			kfree(line->init_str);
		}
		line->init_str = new;
		line->valid = 1;
		err = parse_chan_pair(new, line, n, opts, error_out);
		if (!err) {
			struct device *d = tty_port_register_device(&line->port,
					driver, n, NULL);
			if (IS_ERR(d)) {
				*error_out = "Failed to register device";
				err = PTR_ERR(d);
				parse_chan_pair(NULL, line, n, opts, error_out);
			}
		}
		if (err) {
			*error_out = "failed to parse channel pair";
			line->init_str = NULL;
			line->valid = 0;
			kfree(new);
		}
	}
out:
	return err;
}

/*
 * Common setup code for both startup command line and mconsole initialization.
 * @lines contains the array (of size @num) to modify;
 * @init is the setup string;
 * @error_out is an error string in the case of failure;
 */

int line_setup(char **conf, unsigned int num, char **def,
	       char *init, char *name)
{
	char *error;

	if (*init == '=') {
		/*
		 * We said con=/ssl= instead of con#=, so we are configuring all
		 * consoles at once.
		 */
		*def = init + 1;
	} else {
		char *end;
		unsigned n = simple_strtoul(init, &end, 0);

		if (*end != '=') {
			error = "Couldn't parse device number";
			goto out;
		}
		if (n >= num) {
			error = "Device number out of range";
			goto out;
		}
		conf[n] = end + 1;
	}
	return 0;

out:
	printk(KERN_ERR "Failed to set up %s with "
	       "configuration string \"%s\" : %s\n", name, init, error);
	return -EINVAL;
}

int line_config(struct line *lines, unsigned int num, char *str,
		const struct chan_opts *opts, char **error_out)
{
	char *end;
	int n;

	if (*str == '=') {
		*error_out = "Can't configure all devices from mconsole";
		return -EINVAL;
	}

	n = simple_strtoul(str, &end, 0);
	if (*end++ != '=') {
		*error_out = "Couldn't parse device number";
		return -EINVAL;
	}
	if (n >= num) {
		*error_out = "Device number out of range";
		return -EINVAL;
	}

	return setup_one_line(lines, n, end, opts, error_out);
}

int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
		    int size, char **error_out)
{
	struct line *line;
	char *end;
	int dev, n = 0;

	dev = simple_strtoul(name, &end, 0);
	if ((*end != '\0') || (end == name)) {
		*error_out = "line_get_config failed to parse device number";
		return 0;
	}

	if ((dev < 0) || (dev >= num)) {
		*error_out = "device number out of range";
		return 0;
	}

	line = &lines[dev];

	if (!line->valid)
		CONFIG_CHUNK(str, size, n, "none", 1);
	else {
		struct tty_struct *tty = tty_port_tty_get(&line->port);
		if (tty == NULL) {
			CONFIG_CHUNK(str, size, n, line->init_str, 1);
		} else {
			n = chan_config_string(line, str, size, error_out);
			tty_kref_put(tty);
		}
	}

	return n;
}

int line_id(char **str, int *start_out, int *end_out)
{
	char *end;
	int n;

	n = simple_strtoul(*str, &end, 0);
	if ((*end != '\0') || (end == *str))
		return -1;

	*str = end;
	*start_out = n;
	*end_out = n;
	return n;
}

int line_remove(struct line *lines, unsigned int num, int n, char **error_out)
{
	if (n >= num) {
		*error_out = "Device number out of range";
		return -EINVAL;
	}
	return setup_one_line(lines, n, "none", NULL, error_out);
}

int register_lines(struct line_driver *line_driver,
		   const struct tty_operations *ops,
		   struct line *lines, int nlines)
{
	struct tty_driver *driver;
	int err;
	int i;

	driver = tty_alloc_driver(nlines, TTY_DRIVER_REAL_RAW |
			TTY_DRIVER_DYNAMIC_DEV);
	if (IS_ERR(driver))
		return PTR_ERR(driver);

	driver->driver_name = line_driver->name;
	driver->name = line_driver->device_name;
	driver->major = line_driver->major;
	driver->minor_start = line_driver->minor_start;
	driver->type = line_driver->type;
	driver->subtype = line_driver->subtype;
	driver->init_termios = tty_std_termios;

	for (i = 0; i < nlines; i++) {
		tty_port_init(&lines[i].port);
		lines[i].port.ops = &line_port_ops;
		spin_lock_init(&lines[i].lock);
		lines[i].driver = line_driver;
		INIT_LIST_HEAD(&lines[i].chan_list);
	}
	tty_set_operations(driver, ops);

	err = tty_register_driver(driver);
	if (err) {
		printk(KERN_ERR "register_lines : can't register %s driver\n",
		       line_driver->name);
		tty_driver_kref_put(driver);
		for (i = 0; i < nlines; i++)
			tty_port_destroy(&lines[i].port);
		return err;
	}

	line_driver->driver = driver;
	mconsole_register_dev(&line_driver->mc);
	return 0;
}

static DEFINE_SPINLOCK(winch_handler_lock);
static LIST_HEAD(winch_handlers);

struct winch {
	struct list_head list;
	int fd;
	int tty_fd;
	int pid;
	struct tty_port *port;
	unsigned long stack;
	struct work_struct work;
};

static void __free_winch(struct work_struct *work)
{
	struct winch *winch = container_of(work, struct winch, work);
	um_free_irq(WINCH_IRQ, winch);

	if (winch->pid != -1)
		os_kill_process(winch->pid, 1);
	if (winch->stack != 0)
		free_stack(winch->stack, 0);
	kfree(winch);
}

static void free_winch(struct winch *winch)
{
	int fd = winch->fd;
	winch->fd = -1;
	if (fd != -1)
		os_close_file(fd);
	__free_winch(&winch->work);
}

static irqreturn_t winch_interrupt(int irq, void *data)
{
	struct winch *winch = data;
	struct tty_struct *tty;
	struct line *line;
	int fd = winch->fd;
	int err;
	char c;
	struct pid *pgrp;

	if (fd != -1) {
		err = generic_read(fd, &c, NULL);
		/* A read of 2 means the winch thread failed and has warned */
		if (err < 0 || (err == 1 && c == 2)) {
			if (err != -EAGAIN) {
				winch->fd = -1;
				list_del(&winch->list);
				os_close_file(fd);
				if (err < 0) {
					printk(KERN_ERR "winch_interrupt : read failed, errno = %d\n",
					       -err);
					printk(KERN_ERR "fd %d is losing SIGWINCH support\n",
					       winch->tty_fd);
				}
				INIT_WORK(&winch->work, __free_winch);
				schedule_work(&winch->work);
				return IRQ_HANDLED;
			}
			goto out;
		}
	}
	tty = tty_port_tty_get(winch->port);
	if (tty != NULL) {
		line = tty->driver_data;
		if (line != NULL) {
			chan_window_size(line, &tty->winsize.ws_row,
					 &tty->winsize.ws_col);
			pgrp = tty_get_pgrp(tty);
			if (pgrp)
				kill_pgrp(pgrp, SIGWINCH, 1);
			put_pid(pgrp);
		}
		tty_kref_put(tty);
	}
 out:
	return IRQ_HANDLED;
}

void register_winch_irq(int fd, int tty_fd, int pid, struct tty_port *port,
			unsigned long stack)
{
	struct winch *winch;

	winch = kmalloc(sizeof(*winch), GFP_KERNEL);
	if (winch == NULL) {
		printk(KERN_ERR "register_winch_irq - kmalloc failed\n");
		goto cleanup;
	}

	*winch = ((struct winch) { .fd  	= fd,
				   .tty_fd 	= tty_fd,
				   .pid  	= pid,
				   .port 	= port,
				   .stack	= stack });

	spin_lock(&winch_handler_lock);
	list_add(&winch->list, &winch_handlers);
	spin_unlock(&winch_handler_lock);

	if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
			   IRQF_SHARED, "winch", winch) < 0) {
		printk(KERN_ERR "register_winch_irq - failed to register "
		       "IRQ\n");
		spin_lock(&winch_handler_lock);
		list_del(&winch->list);
		spin_unlock(&winch_handler_lock);
		goto out_free;
	}

	return;

 out_free:
	kfree(winch);
 cleanup:
	os_kill_process(pid, 1);
	os_close_file(fd);
	if (stack != 0)
		free_stack(stack, 0);
}

static void unregister_winch(struct tty_struct *tty)
{
	struct list_head *ele, *next;
	struct winch *winch;
	struct tty_struct *wtty;

	spin_lock(&winch_handler_lock);

	list_for_each_safe(ele, next, &winch_handlers) {
		winch = list_entry(ele, struct winch, list);
		wtty = tty_port_tty_get(winch->port);
		if (wtty == tty) {
			list_del(&winch->list);
			spin_unlock(&winch_handler_lock);
			free_winch(winch);
			break;
		}
		tty_kref_put(wtty);
	}
	spin_unlock(&winch_handler_lock);
}

static void winch_cleanup(void)
{
	struct winch *winch;

	spin_lock(&winch_handler_lock);
	while ((winch = list_first_entry_or_null(&winch_handlers,
						 struct winch, list))) {
		list_del(&winch->list);
		spin_unlock(&winch_handler_lock);

		free_winch(winch);

		spin_lock(&winch_handler_lock);
	}

	spin_unlock(&winch_handler_lock);
}
__uml_exitcall(winch_cleanup);

char *add_xterm_umid(char *base)
{
	char *umid, *title;
	int len;

	umid = get_umid();
	if (*umid == '\0')
		return base;

	len = strlen(base) + strlen(" ()") + strlen(umid) + 1;
	title = kmalloc(len, GFP_KERNEL);
	if (title == NULL) {
		printk(KERN_ERR "Failed to allocate buffer for xterm title\n");
		return base;
	}

	snprintf(title, len, "%s (%s)", base, umid);
	return title;
}