1 files changed, 303 insertions, 0 deletions
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
new file mode 100644
index 0000000000..25727ed648
--- /dev/null
+++ b/arch/um/drivers/chan_user.c
@@ -0,0 +1,303 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+#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 (n == 0)
+		return -EIO;
+	else if (errno == EAGAIN)
+		return 0;
+	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, pid;
+	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.
+	 */
+	pid = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
+	if (pid < 0) {
+		err = pid;
+		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;
+	}
+
+	err = os_set_fd_block(*fd_out, 0);
+	if (err) {
+		printk(UM_KERN_ERR "winch_tramp: failed to set thread_fd "
+		       "non-blocking.\n");
+		goto out_close;
+	}
+
+	return pid;
+
+ 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);
+	}
+}