// 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 char *buf, int 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->driver->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->driver->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);
}

int line_write(struct tty_struct *tty, const unsigned char *buf, int 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->driver->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->driver->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->driver->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(driver->read_irq, fd, IRQ_READ,
                                     line_interrupt, IRQF_SHARED,
                                     driver->read_irq_name, data);
                if (err < 0)
                        return err;
        }

        if (output) {
                err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
                                     line_write_interrupt, IRQF_SHARED,
                                     driver->write_irq_name, data);
                if (err < 0)
                        return 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;
                }
        } 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) {
                        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 = alloc_tty_driver(nlines);
        int err;
        int i;

        if (!driver)
                return -ENOMEM;

        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->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
        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);
                put_tty_driver(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);
                if (err < 0) {
                        if (err != -EAGAIN) {
                                winch->fd = -1;
                                list_del(&winch->list);
                                os_close_file(fd);
                                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) { .list        = LIST_HEAD_INIT(winch->list),
                                   .fd          = fd,
                                   .tty_fd      = tty_fd,
                                   .pid         = pid,
                                   .port        = port,
                                   .stack       = stack });

        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");
                goto out_free;
        }

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

        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;
}