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port_kern.c

/*
 * 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 "asm/atomic.h"
#include "init.h"
#include "irq_kern.h"
#include "os.h"
#include "port.h"

00016 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_DISABLED | IRQF_SHARED | IRQF_SAMPLE_RANDOM,
                    "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_DISABLED | IRQF_SHARED | IRQF_SAMPLE_RANDOM,
                    "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.
             */
            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);

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