arch/um/drivers/chan_user.c

   1 /*
   2  * Copyright (C) 2000 - 2003 Jeff Dike (jdike@addtoit.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <unistd.h>
   7 #include <stdlib.h>
   8 #include <errno.h>
   9 #include <termios.h>
  10 #include <string.h>
  11 #include <signal.h>
  12 #include <sched.h>
  13 #include <sys/stat.h>
  14 #include <sys/ioctl.h>
  15 #include <sys/socket.h>
  16 #include "kern_util.h"
  17 #include "user_util.h"
  18 #include "chan_user.h"
  19 #include "user.h"
  20 #include "os.h"
  21 #include "choose-mode.h"
  22 #include "mode.h"
  23
  24 int generic_console_write(int fd, const char *buf, int n)
  25 {
  26         struct termios save, new;
  27         int err;
  28
  29         if(isatty(fd)){
  30                 CATCH_EINTR(err = tcgetattr(fd, &save));
  31                 if (err)
  32                         goto error;
  33                 new = save;
  34                 /* The terminal becomes a bit less raw, to handle \n also as
  35                  * "Carriage Return", not only as "New Line". Otherwise, the new
  36                  * line won't start at the first column.*/
  37                 new.c_oflag |= OPOST;
  38                 CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
  39                 if (err)
  40                         goto error;
  41         }
  42         err = generic_write(fd, buf, n, NULL);
  43         /* Restore raw mode, in any case; we *must* ignore any error apart
  44          * EINTR, except for debug.*/
  45         if(isatty(fd))
  46                 CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
  47         return(err);
  48 error:
  49         return(-errno);
  50 }
  51
  52 /*
  53  * UML SIGWINCH handling
  54  *
  55  * The point of this is to handle SIGWINCH on consoles which have host ttys and
  56  * relay them inside UML to whatever might be running on the console and cares
  57  * about the window size (since SIGWINCH notifies about terminal size changes).
  58  *
  59  * So, we have a separate thread for each host tty attached to a UML device
  60  * (side-issue - I'm annoyed that one thread can't have multiple controlling
  61  * ttys for purposed of handling SIGWINCH, but I imagine there are other reasons
  62  * that doesn't make any sense).
  63  *
  64  * SIGWINCH can't be received synchronously, so you have to set up to receive it
  65  * as a signal.  That being the case, if you are going to wait for it, it is
  66  * convenient to sit in sigsuspend() and wait for the signal to bounce you out of
  67  * it (see below for how we make sure to exit only on SIGWINCH).
  68  */
  69
  70 static void winch_handler(int sig)
  71 {
  72 }
  73
  74 struct winch_data {
  75         int pty_fd;
  76         int pipe_fd;
  77 };
  78
  79 static int winch_thread(void *arg)
  80 {
  81         struct winch_data *data = arg;
  82         sigset_t sigs;
  83         int pty_fd, pipe_fd;
  84         int count, err;
  85         char c = 1;
  86
  87         pty_fd = data->pty_fd;
  88         pipe_fd = data->pipe_fd;
  89         count = os_write_file(pipe_fd, &c, sizeof(c));
  90         if(count != sizeof(c))
  91                 printk("winch_thread : failed to write synchronization "
  92                        "byte, err = %d\n", -count);
  93
  94         /* We are not using SIG_IGN on purpose, so don't fix it as I thought to
  95          * do! If using SIG_IGN, the sigsuspend() call below would not stop on
  96          * SIGWINCH. */
  97
  98         signal(SIGWINCH, winch_handler);
  99         sigfillset(&sigs);
 100         /* Block all signals possible. */
 101         if(sigprocmask(SIG_SETMASK, &sigs, NULL) < 0){
 102                 printk("winch_thread : sigprocmask failed, errno = %d\n",
 103                        errno);
 104                 exit(1);
 105         }
 106         /* In sigsuspend(), block anything else than SIGWINCH. */
 107         sigdelset(&sigs, SIGWINCH);
 108
 109         if(setsid() < 0){
 110                 printk("winch_thread : setsid failed, errno = %d\n", errno);
 111                 exit(1);
 112         }
 113
 114         err = os_new_tty_pgrp(pty_fd, os_getpid());
 115         if(err < 0){
 116                 printk("winch_thread : new_tty_pgrp failed, err = %d\n", -err);
 117                 exit(1);
 118         }
 119
 120         /* These are synchronization calls between various UML threads on the
 121          * host - since they are not different kernel threads, we cannot use
 122          * kernel semaphores. We don't use SysV semaphores because they are
 123          * persistent. */
 124         count = os_read_file(pipe_fd, &c, sizeof(c));
 125         if(count != sizeof(c))
 126                 printk("winch_thread : failed to read synchronization byte, "
 127                        "err = %d\n", -count);
 128
 129         while(1){
 130                 /* This will be interrupted by SIGWINCH only, since other signals
 131                  * are blocked.*/
 132                 sigsuspend(&sigs);
 133
 134                 count = os_write_file(pipe_fd, &c, sizeof(c));
 135                 if(count != sizeof(c))
 136                         printk("winch_thread : write failed, err = %d\n",
 137                                -count);
 138         }
 139 }
 140
 141 static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out)
 142 {
 143         struct winch_data data;
 144         unsigned long stack;
 145         int fds[2], n, err;
 146         char c;
 147
 148         err = os_pipe(fds, 1, 1);
 149         if(err < 0){
 150                 printk("winch_tramp : os_pipe failed, err = %d\n", -err);
 151                 goto out;
 152         }
 153
 154         data = ((struct winch_data) { .pty_fd           = fd,
 155                                       .pipe_fd          = fds[1] } );
 156         /* CLONE_FILES so this thread doesn't hold open files which are open
 157          * now, but later closed.  This is a problem with /dev/net/tun.
 158          */
 159         err = run_helper_thread(winch_thread, &data, CLONE_FILES, &stack, 0);
 160         if(err < 0){
 161                 printk("fork of winch_thread failed - errno = %d\n", errno);
 162                 goto out_close;
 163         }
 164
 165         *fd_out = fds[0];
 166         n = os_read_file(fds[0], &c, sizeof(c));
 167         if(n != sizeof(c)){
 168                 printk("winch_tramp : failed to read synchronization byte\n");
 169                 printk("read failed, err = %d\n", -n);
 170                 printk("fd %d will not support SIGWINCH\n", fd);
 171                 err = -EINVAL;
 172                 goto out_close;
 173         }
 174         return err ;
 175
 176  out_close:
 177         os_close_file(fds[1]);
 178         os_close_file(fds[0]);
 179  out:
 180         return err;
 181 }
 182
 183 void register_winch(int fd, struct tty_struct *tty)
 184 {
 185         int pid, thread, thread_fd = -1;
 186         int count;
 187         char c = 1;
 188
 189         if(!isatty(fd))
 190                 return;
 191
 192         pid = tcgetpgrp(fd);
 193         if(!CHOOSE_MODE_PROC(is_tracer_winch, is_skas_winch, pid, fd,
 194                              tty) && (pid == -1)){
 195                 thread = winch_tramp(fd, tty, &thread_fd);
 196                 if(thread > 0){
 197                         register_winch_irq(thread_fd, fd, thread, tty);
 198
 199                         count = os_write_file(thread_fd, &c, sizeof(c));
 200                         if(count != sizeof(c))
 201                                 printk("register_winch : failed to write "
 202                                        "synchronization byte, err = %d\n",
 203                                         -count);
 204                 }
 205         }
 206 }
 207
 208 /*
 209  * Overrides for Emacs so that we follow Linus's tabbing style.
 210  * Emacs will notice this stuff at the end of the file and automatically
 211  * adjust the settings for this buffer only.  This must remain at the end
 212  * of the file.
 213  * ---------------------------------------------------------------------------
 214  * Local variables:
 215  * c-file-style: "linux"
 216  * End:
 217  */