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linux-next/arch/um/drivers/chan_user.c
Richard Weinberger 2116bda6ad um: Use tty_port in SIGWINCH handler
The tty below tty_port might get destroyed by the tty layer
while we hold a reference to it.
So we have to carry tty_port around...

Signed-off-by: Richard Weinberger <richard@nod.at>
2013-03-11 10:08:04 +01:00

302 lines
6.9 KiB
C

/*
* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
* Licensed under the GPL
*/
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sched.h>
#include <signal.h>
#include <termios.h>
#include <sys/ioctl.h>
#include "chan_user.h"
#include <os.h>
#include <um_malloc.h>
void generic_close(int fd, void *unused)
{
close(fd);
}
int generic_read(int fd, char *c_out, void *unused)
{
int n;
n = read(fd, c_out, sizeof(*c_out));
if (n > 0)
return n;
else if (errno == EAGAIN)
return 0;
else if (n == 0)
return -EIO;
return -errno;
}
/* XXX Trivial wrapper around write */
int generic_write(int fd, const char *buf, int n, void *unused)
{
int err;
err = write(fd, buf, n);
if (err > 0)
return err;
else if (errno == EAGAIN)
return 0;
else if (err == 0)
return -EIO;
return -errno;
}
int generic_window_size(int fd, void *unused, unsigned short *rows_out,
unsigned short *cols_out)
{
struct winsize size;
int ret;
if (ioctl(fd, TIOCGWINSZ, &size) < 0)
return -errno;
ret = ((*rows_out != size.ws_row) || (*cols_out != size.ws_col));
*rows_out = size.ws_row;
*cols_out = size.ws_col;
return ret;
}
void generic_free(void *data)
{
kfree(data);
}
int generic_console_write(int fd, const char *buf, int n)
{
sigset_t old, no_sigio;
struct termios save, new;
int err;
if (isatty(fd)) {
sigemptyset(&no_sigio);
sigaddset(&no_sigio, SIGIO);
if (sigprocmask(SIG_BLOCK, &no_sigio, &old))
goto error;
CATCH_EINTR(err = tcgetattr(fd, &save));
if (err)
goto error;
new = save;
/*
* The terminal becomes a bit less raw, to handle \n also as
* "Carriage Return", not only as "New Line". Otherwise, the new
* line won't start at the first column.
*/
new.c_oflag |= OPOST;
CATCH_EINTR(err = tcsetattr(fd, TCSAFLUSH, &new));
if (err)
goto error;
}
err = generic_write(fd, buf, n, NULL);
/*
* Restore raw mode, in any case; we *must* ignore any error apart
* EINTR, except for debug.
*/
if (isatty(fd)) {
CATCH_EINTR(tcsetattr(fd, TCSAFLUSH, &save));
sigprocmask(SIG_SETMASK, &old, NULL);
}
return err;
error:
return -errno;
}
/*
* UML SIGWINCH handling
*
* The point of this is to handle SIGWINCH on consoles which have host
* ttys and relay them inside UML to whatever might be running on the
* console and cares about the window size (since SIGWINCH notifies
* about terminal size changes).
*
* So, we have a separate thread for each host tty attached to a UML
* device (side-issue - I'm annoyed that one thread can't have
* multiple controlling ttys for the purpose of handling SIGWINCH, but
* I imagine there are other reasons that doesn't make any sense).
*
* SIGWINCH can't be received synchronously, so you have to set up to
* receive it as a signal. That being the case, if you are going to
* wait for it, it is convenient to sit in sigsuspend() and wait for
* the signal to bounce you out of it (see below for how we make sure
* to exit only on SIGWINCH).
*/
static void winch_handler(int sig)
{
}
struct winch_data {
int pty_fd;
int pipe_fd;
};
static int winch_thread(void *arg)
{
struct winch_data *data = arg;
sigset_t sigs;
int pty_fd, pipe_fd;
int count;
char c = 1;
pty_fd = data->pty_fd;
pipe_fd = data->pipe_fd;
count = write(pipe_fd, &c, sizeof(c));
if (count != sizeof(c))
printk(UM_KERN_ERR "winch_thread : failed to write "
"synchronization byte, err = %d\n", -count);
/*
* We are not using SIG_IGN on purpose, so don't fix it as I thought to
* do! If using SIG_IGN, the sigsuspend() call below would not stop on
* SIGWINCH.
*/
signal(SIGWINCH, winch_handler);
sigfillset(&sigs);
/* Block all signals possible. */
if (sigprocmask(SIG_SETMASK, &sigs, NULL) < 0) {
printk(UM_KERN_ERR "winch_thread : sigprocmask failed, "
"errno = %d\n", errno);
exit(1);
}
/* In sigsuspend(), block anything else than SIGWINCH. */
sigdelset(&sigs, SIGWINCH);
if (setsid() < 0) {
printk(UM_KERN_ERR "winch_thread : setsid failed, errno = %d\n",
errno);
exit(1);
}
if (ioctl(pty_fd, TIOCSCTTY, 0) < 0) {
printk(UM_KERN_ERR "winch_thread : TIOCSCTTY failed on "
"fd %d err = %d\n", pty_fd, errno);
exit(1);
}
if (tcsetpgrp(pty_fd, os_getpid()) < 0) {
printk(UM_KERN_ERR "winch_thread : tcsetpgrp failed on "
"fd %d err = %d\n", pty_fd, errno);
exit(1);
}
/*
* These are synchronization calls between various UML threads on the
* host - since they are not different kernel threads, we cannot use
* kernel semaphores. We don't use SysV semaphores because they are
* persistent.
*/
count = read(pipe_fd, &c, sizeof(c));
if (count != sizeof(c))
printk(UM_KERN_ERR "winch_thread : failed to read "
"synchronization byte, err = %d\n", errno);
while(1) {
/*
* This will be interrupted by SIGWINCH only, since
* other signals are blocked.
*/
sigsuspend(&sigs);
count = write(pipe_fd, &c, sizeof(c));
if (count != sizeof(c))
printk(UM_KERN_ERR "winch_thread : write failed, "
"err = %d\n", errno);
}
}
static int winch_tramp(int fd, struct tty_port *port, int *fd_out,
unsigned long *stack_out)
{
struct winch_data data;
int fds[2], n, err;
char c;
err = os_pipe(fds, 1, 1);
if (err < 0) {
printk(UM_KERN_ERR "winch_tramp : os_pipe failed, err = %d\n",
-err);
goto out;
}
data = ((struct winch_data) { .pty_fd = fd,
.pipe_fd = fds[1] } );
/*
* CLONE_FILES so this thread doesn't hold open files which are open
* now, but later closed in a different thread. This is a
* problem with /dev/net/tun, which if held open by this
* thread, prevents the TUN/TAP device from being reused.
*/
err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
if (err < 0) {
printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
-err);
goto out_close;
}
*fd_out = fds[0];
n = read(fds[0], &c, sizeof(c));
if (n != sizeof(c)) {
printk(UM_KERN_ERR "winch_tramp : failed to read "
"synchronization byte\n");
printk(UM_KERN_ERR "read failed, err = %d\n", errno);
printk(UM_KERN_ERR "fd %d will not support SIGWINCH\n", fd);
err = -EINVAL;
goto out_close;
}
if (os_set_fd_block(*fd_out, 0)) {
printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
"non-blocking.\n");
goto out_close;
}
return err;
out_close:
close(fds[1]);
close(fds[0]);
out:
return err;
}
void register_winch(int fd, struct tty_port *port)
{
unsigned long stack;
int pid, thread, count, thread_fd = -1;
char c = 1;
if (!isatty(fd))
return;
pid = tcgetpgrp(fd);
if (is_skas_winch(pid, fd, port)) {
register_winch_irq(-1, fd, -1, port, 0);
return;
}
if (pid == -1) {
thread = winch_tramp(fd, port, &thread_fd, &stack);
if (thread < 0)
return;
register_winch_irq(thread_fd, fd, thread, port, stack);
count = write(thread_fd, &c, sizeof(c));
if (count != sizeof(c))
printk(UM_KERN_ERR "register_winch : failed to write "
"synchronization byte, err = %d\n", errno);
}
}