port_kern.c

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/*
 * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
 * Licensed under the GPL
 */

#include <linux/completion.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <asm/atomic.h>
#include <init.h>
#include <irq_kern.h>
#include <os.h>
#include "port.h"

struct port_list {
    struct list_head list;
    atomic_t wait_count;
    int has_connection;
    struct completion done;
    int port;
    int fd;
    spinlock_t lock;
    struct list_head pending;
    struct list_head connections;
};

struct port_dev {
    struct port_list *port;
    int helper_pid;
    int telnetd_pid;
};

struct connection {
    struct list_head list;
    int fd;
    int helper_pid;
    int socket[2];
    int telnetd_pid;
    struct port_list *port;
};

static irqreturn_t pipe_interrupt(int irq, void *data)
{
    struct connection *conn = data;
    int fd;

    fd = os_rcv_fd(conn->socket[0], &conn->helper_pid);
    if (fd < 0) {
        if (fd == -EAGAIN)
            return IRQ_NONE;

        printk(KERN_ERR "pipe_interrupt : os_rcv_fd returned %d\n",
               -fd);
        os_close_file(conn->fd);
    }

    list_del(&conn->list);

    conn->fd = fd;
    list_add(&conn->list, &conn->port->connections);

    complete(&conn->port->done);
    return IRQ_HANDLED;
}

#define NO_WAITER_MSG \
    "****\n" \
    "There are currently no UML consoles waiting for port connections.\n" \
    "Either disconnect from one to make it available or activate some more\n" \
    "by enabling more consoles in the UML /etc/inittab.\n" \
    "****\n"

static int port_accept(struct port_list *port)
{
    struct connection *conn;
    int fd, socket[2], pid;

    fd = port_connection(port->fd, socket, &pid);
    if (fd < 0) {
        if (fd != -EAGAIN)
            printk(KERN_ERR "port_accept : port_connection "
                   "returned %d\n", -fd);
        goto out;
    }

    conn = kmalloc(sizeof(*conn), GFP_ATOMIC);
    if (conn == NULL) {
        printk(KERN_ERR "port_accept : failed to allocate "
               "connection\n");
        goto out_close;
    }
    *conn = ((struct connection)
        { .list     = LIST_HEAD_INIT(conn->list),
          .fd       = fd,
          .socket   = { socket[0], socket[1] },
          .telnetd_pid  = pid,
          .port     = port });

    if (um_request_irq(TELNETD_IRQ, socket[0], IRQ_READ, pipe_interrupt,
              IRQF_SHARED, "telnetd", conn)) {
        printk(KERN_ERR "port_accept : failed to get IRQ for "
               "telnetd\n");
        goto out_free;
    }

    if (atomic_read(&port->wait_count) == 0) {
        os_write_file(fd, NO_WAITER_MSG, sizeof(NO_WAITER_MSG));
        printk(KERN_ERR "No one waiting for port\n");
    }
    list_add(&conn->list, &port->pending);
    return 1;

 out_free:
    kfree(conn);
 out_close:
    os_close_file(fd);
    os_kill_process(pid, 1);
 out:
    return 0;
}

static DEFINE_MUTEX(ports_mutex);
static LIST_HEAD(ports);

static void port_work_proc(struct work_struct *unused)
{
    struct port_list *port;
    struct list_head *ele;
    unsigned long flags;

    local_irq_save(flags);
    list_for_each(ele, &ports) {
        port = list_entry(ele, struct port_list, list);
        if (!port->has_connection)
            continue;

        reactivate_fd(port->fd, ACCEPT_IRQ);
        while (port_accept(port))
            ;
        port->has_connection = 0;
    }
    local_irq_restore(flags);
}

DECLARE_WORK(port_work, port_work_proc);

static irqreturn_t port_interrupt(int irq, void *data)
{
    struct port_list *port = data;

    port->has_connection = 1;
    schedule_work(&port_work);
    return IRQ_HANDLED;
}

void *port_data(int port_num)
{
    struct list_head *ele;
    struct port_list *port;
    struct port_dev *dev = NULL;
    int fd;

    mutex_lock(&ports_mutex);
    list_for_each(ele, &ports) {
        port = list_entry(ele, struct port_list, list);
        if (port->port == port_num)
            goto found;
    }
    port = kmalloc(sizeof(struct port_list), GFP_KERNEL);
    if (port == NULL) {
        printk(KERN_ERR "Allocation of port list failed\n");
        goto out;
    }

    fd = port_listen_fd(port_num);
    if (fd < 0) {
        printk(KERN_ERR "binding to port %d failed, errno = %d\n",
               port_num, -fd);
        goto out_free;
    }

    if (um_request_irq(ACCEPT_IRQ, fd, IRQ_READ, port_interrupt,
              IRQF_SHARED, "port", port)) {
        printk(KERN_ERR "Failed to get IRQ for port %d\n", port_num);
        goto out_close;
    }

    *port = ((struct port_list)
        { .list         = LIST_HEAD_INIT(port->list),
          .wait_count       = ATOMIC_INIT(0),
          .has_connection   = 0,
          .port         = port_num,
          .fd           = fd,
          .pending      = LIST_HEAD_INIT(port->pending),
          .connections      = LIST_HEAD_INIT(port->connections) });
    spin_lock_init(&port->lock);
    init_completion(&port->done);
    list_add(&port->list, &ports);

 found:
    dev = kmalloc(sizeof(struct port_dev), GFP_KERNEL);
    if (dev == NULL) {
        printk(KERN_ERR "Allocation of port device entry failed\n");
        goto out;
    }

    *dev = ((struct port_dev) { .port       = port,
                    .helper_pid     = -1,
                    .telnetd_pid    = -1 });
    goto out;

 out_close:
    os_close_file(fd);
 out_free:
    kfree(port);
 out:
    mutex_unlock(&ports_mutex);
    return dev;
}

int port_wait(void *data)
{
    struct port_dev *dev = data;
    struct connection *conn;
    struct port_list *port = dev->port;
    int fd;

    atomic_inc(&port->wait_count);
    while (1) {
        fd = -ERESTARTSYS;
        if (wait_for_completion_interruptible(&port->done))
            goto out;

        spin_lock(&port->lock);

        conn = list_entry(port->connections.next, struct connection,
                  list);
        list_del(&conn->list);
        spin_unlock(&port->lock);

        os_shutdown_socket(conn->socket[0], 1, 1);
        os_close_file(conn->socket[0]);
        os_shutdown_socket(conn->socket[1], 1, 1);
        os_close_file(conn->socket[1]);

        /* This is done here because freeing an IRQ can't be done
         * within the IRQ handler.  So, pipe_interrupt always ups
         * the semaphore regardless of whether it got a successful
         * connection.  Then we loop here throwing out failed
         * connections until a good one is found.
         */
        um_free_irq(TELNETD_IRQ, conn);

        if (conn->fd >= 0)
            break;
        os_close_file(conn->fd);
        kfree(conn);
    }

    fd = conn->fd;
    dev->helper_pid = conn->helper_pid;
    dev->telnetd_pid = conn->telnetd_pid;
    kfree(conn);
 out:
    atomic_dec(&port->wait_count);
    return fd;
}

void port_remove_dev(void *d)
{
    struct port_dev *dev = d;

    if (dev->helper_pid != -1)
        os_kill_process(dev->helper_pid, 0);
    if (dev->telnetd_pid != -1)
        os_kill_process(dev->telnetd_pid, 1);
    dev->helper_pid = -1;
    dev->telnetd_pid = -1;
}

void port_kern_free(void *d)
{
    struct port_dev *dev = d;

    port_remove_dev(dev);
    kfree(dev);
}

static void free_port(void)
{
    struct list_head *ele;
    struct port_list *port;

    list_for_each(ele, &ports) {
        port = list_entry(ele, struct port_list, list);
        free_irq_by_fd(port->fd);
        os_close_file(port->fd);
    }
}

__uml_exitcall(free_port);