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