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         struct termios save, new;
  78         int err;
  79
  80         if (isatty(fd)) {
  81                 CATCH_EINTR(err = tcgetattr(fd, &save));
  82                 if (err)
  83                         goto error;
  84                 new = save;
  85                 /*
  86                  * The terminal becomes a bit less raw, to handle \n also as
  87                  * "Carriage Return", not only as "New Line". Otherwise, the new
  88                  * line won't start at the first column.
  89                  */
  90                 new.c_oflag |= OPOST;
  91                 CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
  92                 if (err)
  93                         goto error;
  94         }
  95         err = generic_write(fd, buf, n, NULL);
  96         /*
  97          * Restore raw mode, in any case; we *must* ignore any error apart
  98          * EINTR, except for debug.
  99          */
 100         if (isatty(fd))
 101                 CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
 102         return err;
 103 error:
 104         return -errno;
 105 }
 106
 107 /*
 108  * UML SIGWINCH handling
 109  *
 110  * The point of this is to handle SIGWINCH on consoles which have host
 111  * ttys and relay them inside UML to whatever might be running on the
 112  * console and cares about the window size (since SIGWINCH notifies
 113  * about terminal size changes).
 114  *
 115  * So, we have a separate thread for each host tty attached to a UML
 116  * device (side-issue - I'm annoyed that one thread can't have
 117  * multiple controlling ttys for the purpose of handling SIGWINCH, but
 118  * I imagine there are other reasons that doesn't make any sense).
 119  *
 120  * SIGWINCH can't be received synchronously, so you have to set up to
 121  * receive it as a signal.  That being the case, if you are going to
 122  * wait for it, it is convenient to sit in sigsuspend() and wait for
 123  * the signal to bounce you out of it (see below for how we make sure
 124  * to exit only on SIGWINCH).
 125  */
 126
 127 static void winch_handler(int sig)
 128 {
 129 }
 130
 131 struct winch_data {
 132         int pty_fd;
 133         int pipe_fd;
 134 };
 135
 136 static int winch_thread(void *arg)
 137 {
 138         struct winch_data *data = arg;
 139         sigset_t sigs;
 140         int pty_fd, pipe_fd;
 141         int count;
 142         char c = 1;
 143
 144         pty_fd = data->pty_fd;
 145         pipe_fd = data->pipe_fd;
 146         count = write(pipe_fd, &c, sizeof(c));
 147         if (count != sizeof(c))
 148                 printk(UM_KERN_ERR "winch_thread : failed to write "
 149                        "synchronization byte, err = %d\n", -count);
 150
 151         /*
 152          * We are not using SIG_IGN on purpose, so don't fix it as I thought to
 153          * do! If using SIG_IGN, the sigsuspend() call below would not stop on
 154          * SIGWINCH.
 155          */
 156
 157         signal(SIGWINCH, winch_handler);
 158         sigfillset(&sigs);
 159         /* Block all signals possible. */
 160         if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) {
 161                 printk(UM_KERN_ERR "winch_thread : sigprocmask failed, "
 162                        "errno = %d\n", errno);
 163                 exit(1);
 164         }
 165         /* In sigsuspend(), block anything else than SIGWINCH. */
 166         sigdelset(&sigs, SIGWINCH);
 167
 168         if (setsid() < 0) {
 169                 printk(UM_KERN_ERR "winch_thread : setsid failed, errno = %d\n",
 170                        errno);
 171                 exit(1);
 172         }
 173
 174         if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) {
 175                 printk(UM_KERN_ERR "winch_thread : TIOCSCTTY failed on "
 176                        "fd %d err = %d\n", pty_fd, errno);
 177                 exit(1);
 178         }
 179
 180         if (tcsetpgrp(pty_fd, os_getpid()) < 0) {
 181                 printk(UM_KERN_ERR "winch_thread : tcsetpgrp failed on "
 182                        "fd %d err = %d\n", pty_fd, errno);
 183                 exit(1);
 184         }
 185
 186         /*
 187          * These are synchronization calls between various UML threads on the
 188          * host - since they are not different kernel threads, we cannot use
 189          * kernel semaphores. We don't use SysV semaphores because they are
 190          * persistent.
 191          */
 192         count = read(pipe_fd, &c, sizeof(c));
 193         if (count != sizeof(c))
 194                 printk(UM_KERN_ERR "winch_thread : failed to read "
 195                        "synchronization byte, err = %d\n", errno);
 196
 197         while(1) {
 198                 /*
 199                  * This will be interrupted by SIGWINCH only, since
 200                  * other signals are blocked.
 201                  */
 202                 sigsuspend(&sigs);
 203
 204                 count = write(pipe_fd, &c, sizeof(c));
 205                 if (count != sizeof(c))
 206                         printk(UM_KERN_ERR "winch_thread : write failed, "
 207                                "err = %d\n", errno);
 208         }
 209 }
 210
 211 static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out,
 212                        unsigned long *stack_out)
 213 {
 214         struct winch_data data;
 215         int fds[2], n, err;
 216         char c;
 217
 218         err = os_pipe(fds, 1, 1);
 219         if (err < 0) {
 220                 printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n",
 221                        -err);
 222                 goto out;
 223         }
 224
 225         data = ((struct winch_data) { .pty_fd           = fd,
 226                                       .pipe_fd          = fds[1] } );
 227         /*
 228          * CLONE_FILES so this thread doesn't hold open files which are open
 229          * now, but later closed in a different thread.  This is a
 230          * problem with /dev/net/tun, which if held open by this
 231          * thread, prevents the TUN/TAP device from being reused.
 232          */
 233         err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
 234         if (err < 0) {
 235                 printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
 236                        -err);
 237                 goto out_close;
 238         }
 239
 240         *fd_out = fds[0];
 241         n = read(fds[0], &c, sizeof(c));
 242         if (n != sizeof(c)) {
 243                 printk(UM_KERN_ERR "winch_tramp : failed to read "
 244                        "synchronization byte\n");
 245                 printk(UM_KERN_ERR "read failed, err = %d\n", errno);
 246                 printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd);
 247                 err = -EINVAL;
 248                 goto out_close;
 249         }
 250
 251         if (os_set_fd_block(*fd_out, 0)) {
 252                 printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
 253                        "non-blocking.\n");
 254                 goto out_close;
 255         }
 256
 257         return err;
 258
 259  out_close:
 260         close(fds[1]);
 261         close(fds[0]);
 262  out:
 263         return err;
 264 }
 265
 266 void register_winch(int fd, struct tty_struct *tty)
 267 {
 268         unsigned long stack;
 269         int pid, thread, count, thread_fd = -1;
 270         char c = 1;
 271
 272         if (!isatty(fd))
 273                 return;
 274
 275         pid = tcgetpgrp(fd);
 276         if (!is_skas_winch(pid, fd, tty) && (pid == -1)) {
 277                 thread = winch_tramp(fd, tty, &thread_fd, &stack);
 278                 if (thread < 0)
 279                         return;
 280
 281                 register_winch_irq(thread_fd, fd, thread, tty, stack);
 282
 283                 count = write(thread_fd, &c, sizeof(c));
 284                 if (count != sizeof(c))
 285                         printk(UM_KERN_ERR "register_winch : failed to write "
 286                                "synchronization byte, err = %d\n", errno);
 287         }
 288 }