linux/arch/um/drivers/chan_user.c
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   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
  17void generic_close(int fd, void *unused)
  18{
  19        close(fd);
  20}
  21
  22int generic_read(int fd, char *c_out, void *unused)
  23{
  24        int n;
  25
  26        n = read(fd, c_out, sizeof(*c_out));
  27        if (n > 0)
  28                return n;
  29        else if (errno == EAGAIN)
  30                return 0;
  31        else if (n == 0)
  32                return -EIO;
  33        return -errno;
  34}
  35
  36/* XXX Trivial wrapper around write */
  37
  38int generic_write(int fd, const char *buf, int n, void *unused)
  39{
  40        int err;
  41
  42        err = write(fd, buf, n);
  43        if (err > 0)
  44                return err;
  45        else if (errno == EAGAIN)
  46                return 0;
  47        else if (err == 0)
  48                return -EIO;
  49        return -errno;
  50}
  51
  52int generic_window_size(int fd, void *unused, unsigned short *rows_out,
  53                        unsigned short *cols_out)
  54{
  55        struct winsize size;
  56        int ret;
  57
  58        if (ioctl(fd, TIOCGWINSZ, &size) < 0)
  59                return -errno;
  60
  61        ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col));
  62
  63        *rows_out = size.ws_row;
  64        *cols_out = size.ws_col;
  65
  66        return ret;
  67}
  68
  69void generic_free(void *data)
  70{
  71        kfree(data);
  72}
  73
  74int generic_console_write(int fd, const char *buf, int n)
  75{
  76        sigset_t old, no_sigio;
  77        struct termios save, new;
  78        int err;
  79
  80        if (isatty(fd)) {
  81                sigemptyset(&no_sigio);
  82                sigaddset(&no_sigio, SIGIO);
  83                if (sigprocmask(SIG_BLOCK, &no_sigio, &old))
  84                        goto error;
  85
  86                CATCH_EINTR(err = tcgetattr(fd, &save));
  87                if (err)
  88                        goto error;
  89                new = save;
  90                /*
  91                 * The terminal becomes a bit less raw, to handle \n also as
  92                 * "Carriage Return", not only as "New Line". Otherwise, the new
  93                 * line won't start at the first column.
  94                 */
  95                new.c_oflag |= OPOST;
  96                CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
  97                if (err)
  98                        goto error;
  99        }
 100        err = generic_write(fd, buf, n, NULL);
 101        /*
 102         * Restore raw mode, in any case; we *must* ignore any error apart
 103         * EINTR, except for debug.
 104         */
 105        if (isatty(fd)) {
 106                CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
 107                sigprocmask(SIG_SETMASK, &old, NULL);
 108        }
 109
 110        return err;
 111error:
 112        return -errno;
 113}
 114
 115/*
 116 * UML SIGWINCH handling
 117 *
 118 * The point of this is to handle SIGWINCH on consoles which have host
 119 * ttys and relay them inside UML to whatever might be running on the
 120 * console and cares about the window size (since SIGWINCH notifies
 121 * about terminal size changes).
 122 *
 123 * So, we have a separate thread for each host tty attached to a UML
 124 * device (side-issue - I'm annoyed that one thread can't have
 125 * multiple controlling ttys for the purpose of handling SIGWINCH, but
 126 * I imagine there are other reasons that doesn't make any sense).
 127 *
 128 * SIGWINCH can't be received synchronously, so you have to set up to
 129 * receive it as a signal.  That being the case, if you are going to
 130 * wait for it, it is convenient to sit in sigsuspend() and wait for
 131 * the signal to bounce you out of it (see below for how we make sure
 132 * to exit only on SIGWINCH).
 133 */
 134
 135static void winch_handler(int sig)
 136{
 137}
 138
 139struct winch_data {
 140        int pty_fd;
 141        int pipe_fd;
 142};
 143
 144static int winch_thread(void *arg)
 145{
 146        struct winch_data *data = arg;
 147        sigset_t sigs;
 148        int pty_fd, pipe_fd;
 149        int count;
 150        char c = 1;
 151
 152        pty_fd = data->pty_fd;
 153        pipe_fd = data->pipe_fd;
 154        count = write(pipe_fd, &c, sizeof(c));
 155        if (count != sizeof(c))
 156                printk(UM_KERN_ERR "winch_thread : failed to write "
 157                       "synchronization byte, err = %d\n", -count);
 158
 159        /*
 160         * We are not using SIG_IGN on purpose, so don't fix it as I thought to
 161         * do! If using SIG_IGN, the sigsuspend() call below would not stop on
 162         * SIGWINCH.
 163         */
 164
 165        signal(SIGWINCH, winch_handler);
 166        sigfillset(&sigs);
 167        /* Block all signals possible. */
 168        if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) {
 169                printk(UM_KERN_ERR "winch_thread : sigprocmask failed, "
 170                       "errno = %d\n", errno);
 171                exit(1);
 172        }
 173        /* In sigsuspend(), block anything else than SIGWINCH. */
 174        sigdelset(&sigs, SIGWINCH);
 175
 176        if (setsid() < 0) {
 177                printk(UM_KERN_ERR "winch_thread : setsid failed, errno = %d\n",
 178                       errno);
 179                exit(1);
 180        }
 181
 182        if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) {
 183                printk(UM_KERN_ERR "winch_thread : TIOCSCTTY failed on "
 184                       "fd %d err = %d\n", pty_fd, errno);
 185                exit(1);
 186        }
 187
 188        if (tcsetpgrp(pty_fd, os_getpid()) < 0) {
 189                printk(UM_KERN_ERR "winch_thread : tcsetpgrp failed on "
 190                       "fd %d err = %d\n", pty_fd, errno);
 191                exit(1);
 192        }
 193
 194        /*
 195         * These are synchronization calls between various UML threads on the
 196         * host - since they are not different kernel threads, we cannot use
 197         * kernel semaphores. We don't use SysV semaphores because they are
 198         * persistent.
 199         */
 200        count = read(pipe_fd, &c, sizeof(c));
 201        if (count != sizeof(c))
 202                printk(UM_KERN_ERR "winch_thread : failed to read "
 203                       "synchronization byte, err = %d\n", errno);
 204
 205        while(1) {
 206                /*
 207                 * This will be interrupted by SIGWINCH only, since
 208                 * other signals are blocked.
 209                 */
 210                sigsuspend(&sigs);
 211
 212                count = write(pipe_fd, &c, sizeof(c));
 213                if (count != sizeof(c))
 214                        printk(UM_KERN_ERR "winch_thread : write failed, "
 215                               "err = %d\n", errno);
 216        }
 217}
 218
 219static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out,
 220                       unsigned long *stack_out)
 221{
 222        struct winch_data data;
 223        int fds[2], n, err;
 224        char c;
 225
 226        err = os_pipe(fds, 1, 1);
 227        if (err < 0) {
 228                printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n",
 229                       -err);
 230                goto out;
 231        }
 232
 233        data = ((struct winch_data) { .pty_fd           = fd,
 234                                      .pipe_fd          = fds[1] } );
 235        /*
 236         * CLONE_FILES so this thread doesn't hold open files which are open
 237         * now, but later closed in a different thread.  This is a
 238         * problem with /dev/net/tun, which if held open by this
 239         * thread, prevents the TUN/TAP device from being reused.
 240         */
 241        err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
 242        if (err < 0) {
 243                printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
 244                       -err);
 245                goto out_close;
 246        }
 247
 248        *fd_out = fds[0];
 249        n = read(fds[0], &c, sizeof(c));
 250        if (n != sizeof(c)) {
 251                printk(UM_KERN_ERR "winch_tramp : failed to read "
 252                       "synchronization byte\n");
 253                printk(UM_KERN_ERR "read failed, err = %d\n", errno);
 254                printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd);
 255                err = -EINVAL;
 256                goto out_close;
 257        }
 258
 259        if (os_set_fd_block(*fd_out, 0)) {
 260                printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
 261                       "non-blocking.\n");
 262                goto out_close;
 263        }
 264
 265        return err;
 266
 267 out_close:
 268        close(fds[1]);
 269        close(fds[0]);
 270 out:
 271        return err;
 272}
 273
 274void register_winch(int fd, struct tty_struct *tty)
 275{
 276        unsigned long stack;
 277        int pid, thread, count, thread_fd = -1;
 278        char c = 1;
 279
 280        if (!isatty(fd))
 281                return;
 282
 283        pid = tcgetpgrp(fd);
 284        if (is_skas_winch(pid, fd, tty)) {
 285                register_winch_irq(-1, fd, -1, tty, 0);
 286                return;
 287        }
 288
 289        if (pid == -1) {
 290                thread = winch_tramp(fd, tty, &thread_fd, &stack);
 291                if (thread < 0)
 292                        return;
 293
 294                register_winch_irq(thread_fd, fd, thread, tty, stack);
 295
 296                count = write(thread_fd, &c, sizeof(c));
 297                if (count != sizeof(c))
 298                        printk(UM_KERN_ERR "register_winch : failed to write "
 299                               "synchronization byte, err = %d\n", errno);
 300        }
 301}
 302
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