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Linux/arch/um/drivers/port_kern.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
  4  */
  5 
  6 #include <linux/completion.h>
  7 #include <linux/interrupt.h>
  8 #include <linux/list.h>
  9 #include <linux/mutex.h>
 10 #include <linux/slab.h>
 11 #include <linux/workqueue.h>
 12 #include <asm/atomic.h>
 13 #include <init.h>
 14 #include <irq_kern.h>
 15 #include <os.h>
 16 #include "port.h"
 17 
 18 struct port_list {
 19         struct list_head list;
 20         atomic_t wait_count;
 21         int has_connection;
 22         struct completion done;
 23         int port;
 24         int fd;
 25         spinlock_t lock;
 26         struct list_head pending;
 27         struct list_head connections;
 28 };
 29 
 30 struct port_dev {
 31         struct port_list *port;
 32         int helper_pid;
 33         int telnetd_pid;
 34 };
 35 
 36 struct connection {
 37         struct list_head list;
 38         int fd;
 39         int helper_pid;
 40         int socket[2];
 41         int telnetd_pid;
 42         struct port_list *port;
 43 };
 44 
 45 static irqreturn_t pipe_interrupt(int irq, void *data)
 46 {
 47         struct connection *conn = data;
 48         int fd;
 49 
 50         fd = os_rcv_fd(conn->socket[0], &conn->helper_pid);
 51         if (fd < 0) {
 52                 if (fd == -EAGAIN)
 53                         return IRQ_NONE;
 54 
 55                 printk(KERN_ERR "pipe_interrupt : os_rcv_fd returned %d\n",
 56                        -fd);
 57                 os_close_file(conn->fd);
 58         }
 59 
 60         list_del(&conn->list);
 61 
 62         conn->fd = fd;
 63         list_add(&conn->list, &conn->port->connections);
 64 
 65         complete(&conn->port->done);
 66         return IRQ_HANDLED;
 67 }
 68 
 69 #define NO_WAITER_MSG \
 70     "****\n" \
 71     "There are currently no UML consoles waiting for port connections.\n" \
 72     "Either disconnect from one to make it available or activate some more\n" \
 73     "by enabling more consoles in the UML /etc/inittab.\n" \
 74     "****\n"
 75 
 76 static int port_accept(struct port_list *port)
 77 {
 78         struct connection *conn;
 79         int fd, socket[2], pid;
 80 
 81         fd = port_connection(port->fd, socket, &pid);
 82         if (fd < 0) {
 83                 if (fd != -EAGAIN)
 84                         printk(KERN_ERR "port_accept : port_connection "
 85                                "returned %d\n", -fd);
 86                 goto out;
 87         }
 88 
 89         conn = kmalloc(sizeof(*conn), GFP_ATOMIC);
 90         if (conn == NULL) {
 91                 printk(KERN_ERR "port_accept : failed to allocate "
 92                        "connection\n");
 93                 goto out_close;
 94         }
 95         *conn = ((struct connection)
 96                 { .list         = LIST_HEAD_INIT(conn->list),
 97                   .fd           = fd,
 98                   .socket       = { socket[0], socket[1] },
 99                   .telnetd_pid  = pid,
100                   .port         = port });
101 
102         if (um_request_irq(TELNETD_IRQ, socket[0], IRQ_READ, pipe_interrupt,
103                           IRQF_SHARED, "telnetd", conn)) {
104                 printk(KERN_ERR "port_accept : failed to get IRQ for "
105                        "telnetd\n");
106                 goto out_free;
107         }
108 
109         if (atomic_read(&port->wait_count) == 0) {
110                 os_write_file(fd, NO_WAITER_MSG, sizeof(NO_WAITER_MSG));
111                 printk(KERN_ERR "No one waiting for port\n");
112         }
113         list_add(&conn->list, &port->pending);
114         return 1;
115 
116  out_free:
117         kfree(conn);
118  out_close:
119         os_close_file(fd);
120         os_kill_process(pid, 1);
121  out:
122         return 0;
123 }
124 
125 static DEFINE_MUTEX(ports_mutex);
126 static LIST_HEAD(ports);
127 
128 static void port_work_proc(struct work_struct *unused)
129 {
130         struct port_list *port;
131         struct list_head *ele;
132         unsigned long flags;
133 
134         local_irq_save(flags);
135         list_for_each(ele, &ports) {
136                 port = list_entry(ele, struct port_list, list);
137                 if (!port->has_connection)
138                         continue;
139 
140                 while (port_accept(port))
141                         ;
142                 port->has_connection = 0;
143         }
144         local_irq_restore(flags);
145 }
146 
147 DECLARE_WORK(port_work, port_work_proc);
148 
149 static irqreturn_t port_interrupt(int irq, void *data)
150 {
151         struct port_list *port = data;
152 
153         port->has_connection = 1;
154         schedule_work(&port_work);
155         return IRQ_HANDLED;
156 }
157 
158 void *port_data(int port_num)
159 {
160         struct list_head *ele;
161         struct port_list *port;
162         struct port_dev *dev = NULL;
163         int fd;
164 
165         mutex_lock(&ports_mutex);
166         list_for_each(ele, &ports) {
167                 port = list_entry(ele, struct port_list, list);
168                 if (port->port == port_num)
169                         goto found;
170         }
171         port = kmalloc(sizeof(struct port_list), GFP_KERNEL);
172         if (port == NULL) {
173                 printk(KERN_ERR "Allocation of port list failed\n");
174                 goto out;
175         }
176 
177         fd = port_listen_fd(port_num);
178         if (fd < 0) {
179                 printk(KERN_ERR "binding to port %d failed, errno = %d\n",
180                        port_num, -fd);
181                 goto out_free;
182         }
183 
184         if (um_request_irq(ACCEPT_IRQ, fd, IRQ_READ, port_interrupt,
185                           IRQF_SHARED, "port", port)) {
186                 printk(KERN_ERR "Failed to get IRQ for port %d\n", port_num);
187                 goto out_close;
188         }
189 
190         *port = ((struct port_list)
191                 { .list                 = LIST_HEAD_INIT(port->list),
192                   .wait_count           = ATOMIC_INIT(0),
193                   .has_connection       = 0,
194                   .port                 = port_num,
195                   .fd                   = fd,
196                   .pending              = LIST_HEAD_INIT(port->pending),
197                   .connections          = LIST_HEAD_INIT(port->connections) });
198         spin_lock_init(&port->lock);
199         init_completion(&port->done);
200         list_add(&port->list, &ports);
201 
202  found:
203         dev = kmalloc(sizeof(struct port_dev), GFP_KERNEL);
204         if (dev == NULL) {
205                 printk(KERN_ERR "Allocation of port device entry failed\n");
206                 goto out;
207         }
208 
209         *dev = ((struct port_dev) { .port               = port,
210                                     .helper_pid         = -1,
211                                     .telnetd_pid        = -1 });
212         goto out;
213 
214  out_close:
215         os_close_file(fd);
216  out_free:
217         kfree(port);
218  out:
219         mutex_unlock(&ports_mutex);
220         return dev;
221 }
222 
223 int port_wait(void *data)
224 {
225         struct port_dev *dev = data;
226         struct connection *conn;
227         struct port_list *port = dev->port;
228         int fd;
229 
230         atomic_inc(&port->wait_count);
231         while (1) {
232                 fd = -ERESTARTSYS;
233                 if (wait_for_completion_interruptible(&port->done))
234                         goto out;
235 
236                 spin_lock(&port->lock);
237 
238                 conn = list_entry(port->connections.next, struct connection,
239                                   list);
240                 list_del(&conn->list);
241                 spin_unlock(&port->lock);
242 
243                 os_shutdown_socket(conn->socket[0], 1, 1);
244                 os_close_file(conn->socket[0]);
245                 os_shutdown_socket(conn->socket[1], 1, 1);
246                 os_close_file(conn->socket[1]);
247 
248                 /* This is done here because freeing an IRQ can't be done
249                  * within the IRQ handler.  So, pipe_interrupt always ups
250                  * the semaphore regardless of whether it got a successful
251                  * connection.  Then we loop here throwing out failed
252                  * connections until a good one is found.
253                  */
254                 um_free_irq(TELNETD_IRQ, conn);
255 
256                 if (conn->fd >= 0)
257                         break;
258                 os_close_file(conn->fd);
259                 kfree(conn);
260         }
261 
262         fd = conn->fd;
263         dev->helper_pid = conn->helper_pid;
264         dev->telnetd_pid = conn->telnetd_pid;
265         kfree(conn);
266  out:
267         atomic_dec(&port->wait_count);
268         return fd;
269 }
270 
271 void port_remove_dev(void *d)
272 {
273         struct port_dev *dev = d;
274 
275         if (dev->helper_pid != -1)
276                 os_kill_process(dev->helper_pid, 0);
277         if (dev->telnetd_pid != -1)
278                 os_kill_process(dev->telnetd_pid, 1);
279         dev->helper_pid = -1;
280         dev->telnetd_pid = -1;
281 }
282 
283 void port_kern_free(void *d)
284 {
285         struct port_dev *dev = d;
286 
287         port_remove_dev(dev);
288         kfree(dev);
289 }
290 
291 static void free_port(void)
292 {
293         struct list_head *ele;
294         struct port_list *port;
295 
296         list_for_each(ele, &ports) {
297                 port = list_entry(ele, struct port_list, list);
298                 free_irq_by_fd(port->fd);
299                 os_close_file(port->fd);
300         }
301 }
302 
303 __uml_exitcall(free_port);
304 

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