arch/um/drivers/chan_user.c

   1 /*
   2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <errno.h>
   9 #include <sched.h>
  10 #include <signal.h>
  11 #include <termios.h>
  12 #include <sys/ioctl.h>
  13 #include "chan_user.h"
  14 #include "os.h"
  15 #include "um_malloc.h"
  16 #include "user.h"
  17
  18 void generic_close(int fd, void *unused)
  19 {
  20         close(fd);
  21 }
  22
  23 int generic_read(int fd, char *c_out, void *unused)
  24 {
  25         int n;
  26
  27         n = read(fd, c_out, sizeof(*c_out));
  28         if (n > 0)
  29                 return n;
  30         else if (errno == EAGAIN)
  31                 return 0;
  32         else if (n == 0)
  33                 return -EIO;
  34         return -errno;
  35 }
  36
  37 /* XXX Trivial wrapper around write */
  38
  39 int generic_write(int fd, const char *buf, int n, void *unused)
  40 {
  41         int err;
  42
  43         err = write(fd, buf, n);
  44         if (err > 0)
  45                 return err;
  46         else if (errno == EAGAIN)
  47                 return 0;
  48         else if (err == 0)
  49                 return -EIO;
  50         return -errno;
  51 }
  52
  53 int generic_window_size(int fd, void *unused, unsigned short *rows_out,
  54                         unsigned short *cols_out)
  55 {
  56         struct winsize size;
  57         int ret;
  58
  59         if (ioctl(fd, TIOCGWINSZ, &size) < 0)
  60                 return -errno;
  61
  62         ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col));
  63
  64         *rows_out = size.ws_row;
  65         *cols_out = size.ws_col;
  66
  67         return ret;
  68 }
  69
  70 void generic_free(void *data)
  71 {
  72         kfree(data);
  73 }
  74
  75 int generic_console_write(int fd, const char *buf, int n)
  76 {
  77         sigset_t old, no_sigio;
  78         struct termios save, new;
  79         int err;
  80
  81         if (isatty(fd)) {
  82                 sigemptyset(&no_sigio);
  83                 sigaddset(&no_sigio, SIGIO);
  84                 if (sigprocmask(SIG_BLOCK, &no_sigio, &old))
  85                         goto error;
  86
  87                 CATCH_EINTR(err = tcgetattr(fd, &save));
  88                 if (err)
  89                         goto error;
  90                 new = save;
  91                 /*
  92                  * The terminal becomes a bit less raw, to handle \n also as
  93                  * "Carriage Return", not only as "New Line". Otherwise, the new
  94                  * line won't start at the first column.
  95                  */
  96                 new.c_oflag |= OPOST;
  97                 CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
  98                 if (err)
  99                         goto error;
 100         }
 101         err = generic_write(fd, buf, n, NULL);
 102         /*
 103          * Restore raw mode, in any case; we *must* ignore any error apart
 104          * EINTR, except for debug.
 105          */
 106         if (isatty(fd)) {
 107                 CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
 108                 sigprocmask(SIG_SETMASK, &old, NULL);
 109         }
 110
 111         return err;
 112 error:
 113         return -errno;
 114 }
 115
 116 /*
 117  * UML SIGWINCH handling
 118  *
 119  * The point of this is to handle SIGWINCH on consoles which have host
 120  * ttys and relay them inside UML to whatever might be running on the
 121  * console and cares about the window size (since SIGWINCH notifies
 122  * about terminal size changes).
 123  *
 124  * So, we have a separate thread for each host tty attached to a UML
 125  * device (side-issue - I'm annoyed that one thread can't have
 126  * multiple controlling ttys for the purpose of handling SIGWINCH, but
 127  * I imagine there are other reasons that doesn't make any sense).
 128  *
 129  * SIGWINCH can't be received synchronously, so you have to set up to
 130  * receive it as a signal.  That being the case, if you are going to
 131  * wait for it, it is convenient to sit in sigsuspend() and wait for
 132  * the signal to bounce you out of it (see below for how we make sure
 133  * to exit only on SIGWINCH).
 134  */
 135
 136 static void winch_handler(int sig)
 137 {
 138 }
 139
 140 struct winch_data {
 141         int pty_fd;
 142         int pipe_fd;
 143 };
 144
 145 static int winch_thread(void *arg)
 146 {
 147         struct winch_data *data = arg;
 148         sigset_t sigs;
 149         int pty_fd, pipe_fd;
 150         int count;
 151         char c = 1;
 152
 153         pty_fd = data->pty_fd;
 154         pipe_fd = data->pipe_fd;
 155         count = write(pipe_fd, &c, sizeof(c));
 156         if (count != sizeof(c))
 157                 printk(UM_KERN_ERR "winch_thread : failed to write "
 158                        "synchronization byte, err = %d\n", -count);
 159
 160         /*
 161          * We are not using SIG_IGN on purpose, so don't fix it as I thought to
 162          * do! If using SIG_IGN, the sigsuspend() call below would not stop on
 163          * SIGWINCH.
 164          */
 165
 166         signal(SIGWINCH, winch_handler);
 167         sigfillset(&sigs);
 168         /* Block all signals possible. */
 169         if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) {
 170                 printk(UM_KERN_ERR "winch_thread : sigprocmask failed, "
 171                        "errno = %d\n", errno);
 172                 exit(1);
 173         }
 174         /* In sigsuspend(), block anything else than SIGWINCH. */
 175         sigdelset(&sigs, SIGWINCH);
 176
 177         if (setsid() < 0) {
 178                 printk(UM_KERN_ERR "winch_thread : setsid failed, errno = %d\n",
 179                        errno);
 180                 exit(1);
 181         }
 182
 183         if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) {
 184                 printk(UM_KERN_ERR "winch_thread : TIOCSCTTY failed on "
 185                        "fd %d err = %d\n", pty_fd, errno);
 186                 exit(1);
 187         }
 188
 189         if (tcsetpgrp(pty_fd, os_getpid()) < 0) {
 190                 printk(UM_KERN_ERR "winch_thread : tcsetpgrp failed on "
 191                        "fd %d err = %d\n", pty_fd, errno);
 192                 exit(1);
 193         }
 194
 195         /*
 196          * These are synchronization calls between various UML threads on the
 197          * host - since they are not different kernel threads, we cannot use
 198          * kernel semaphores. We don't use SysV semaphores because they are
 199          * persistent.
 200          */
 201         count = read(pipe_fd, &c, sizeof(c));
 202         if (count != sizeof(c))
 203                 printk(UM_KERN_ERR "winch_thread : failed to read "
 204                        "synchronization byte, err = %d\n", errno);
 205
 206         while(1) {
 207                 /*
 208                  * This will be interrupted by SIGWINCH only, since
 209                  * other signals are blocked.
 210                  */
 211                 sigsuspend(&sigs);
 212
 213                 count = write(pipe_fd, &c, sizeof(c));
 214                 if (count != sizeof(c))
 215                         printk(UM_KERN_ERR "winch_thread : write failed, "
 216                                "err = %d\n", errno);
 217         }
 218 }
 219
 220 static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out,
 221                        unsigned long *stack_out)
 222 {
 223         struct winch_data data;
 224         int fds[2], n, err;
 225         char c;
 226
 227         err = os_pipe(fds, 1, 1);
 228         if (err < 0) {
 229                 printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n",
 230                        -err);
 231                 goto out;
 232         }
 233
 234         data = ((struct winch_data) { .pty_fd           = fd,
 235                                       .pipe_fd          = fds[1] } );
 236         /*
 237          * CLONE_FILES so this thread doesn't hold open files which are open
 238          * now, but later closed in a different thread.  This is a
 239          * problem with /dev/net/tun, which if held open by this
 240          * thread, prevents the TUN/TAP device from being reused.
 241          */
 242         err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
 243         if (err < 0) {
 244                 printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
 245                        -err);
 246                 goto out_close;
 247         }
 248
 249         *fd_out = fds[0];
 250         n = read(fds[0], &c, sizeof(c));
 251         if (n != sizeof(c)) {
 252                 printk(UM_KERN_ERR "winch_tramp : failed to read "
 253                        "synchronization byte\n");
 254                 printk(UM_KERN_ERR "read failed, err = %d\n", errno);
 255                 printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd);
 256                 err = -EINVAL;
 257                 goto out_close;
 258         }
 259
 260         if (os_set_fd_block(*fd_out, 0)) {
 261                 printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
 262                        "non-blocking.\n");
 263                 goto out_close;
 264         }
 265
 266         return err;
 267
 268  out_close:
 269         close(fds[1]);
 270         close(fds[0]);
 271  out:
 272         return err;
 273 }
 274
 275 void register_winch(int fd, struct tty_struct *tty)
 276 {
 277         unsigned long stack;
 278         int pid, thread, count, thread_fd = -1;
 279         char c = 1;
 280
 281         if (!isatty(fd))
 282                 return;
 283
 284         pid = tcgetpgrp(fd);
 285         if (!is_skas_winch(pid, fd, tty) && (pid == -1)) {
 286                 thread = winch_tramp(fd, tty, &thread_fd, &stack);
 287                 if (thread < 0)
 288                         return;
 289
 290                 register_winch_irq(thread_fd, fd, thread, tty, stack);
 291
 292                 count = write(thread_fd, &c, sizeof(c));
 293                 if (count != sizeof(c))
 294                         printk(UM_KERN_ERR "register_winch : failed to write "
 295                                "synchronization byte, err = %d\n", errno);
 296         }
 297 }