From: LaMont Jones <lamont@mmjgroup.com>
Date: Tue, 17 Jul 2007 23:26:02 +0000 (-0600)
Subject: agetty historical (and broken) code
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=68f2810e53cab1468d4c6fb114cb76ac0e7bcd5a;p=util-linux

agetty historical (and broken) code
---

diff --git a/login-utils/agetty.c b/login-utils/agetty.c
index b7ae536f..7d5d81b3 100644
--- a/login-utils/agetty.c
+++ b/login-utils/agetty.c
@@ -664,6 +664,93 @@ open_tty(tty, tp, local)
 	if ((st.st_mode & S_IFMT) != S_IFCHR)
 	    error(_("/dev/%s: not a character device"), tty);
 
+	/*
+	 * Try to avoid opening a vt that is already open, as this will
+	 * mean that the keyboard will be unusable.
+	 *
+	 * Unfortunately, all the kernel gives us to find out is an ioctl
+	 * for the next available vt.  As the kernel doesn't open the vt for
+	 * you with the ioctl, there is still a chance of both processes
+	 * opening the same vt, but this check is far better than nothing at
+	 * all.
+	 *
+	 * The kernel API sucks, and is unusable for this situation.  What
+	 * we really need is an ioctl that says 'does anyone _ELSE_ have
+	 * this tty open', and that doesn't exist.  Or better yet, the
+	 * kernel really shouldn't allow two processes to have read access
+	 * on the same tty at the same time (other than with dup...)  Opens
+	 * of the same tty device shouldn't be able to steal reads from
+	 * each other.
+	 *
+	 * Similar to the check added to gdm.
+	 *
+	 * For now, just turn off this check, restoring the bug that ?dm
+	 * (and the system) occasionally get their keyboard locked out by
+	 * getty showing up after they've taken a vt that inittab says
+	 * goes to a getty.
+	 * Bummer.
+	 *
+	 */
+#if 0
+	if (strncmp(tty,"tty",3) == 0)
+	{
+#include <sys/vt.h>
+#include <linux/tty.h>
+	    char *end;
+	    int vtno;
+
+	    vtno = strtol(tty+3,&end,10);
+	    if (end != tty+3 && *end == '\0' && vtno > 1)
+	    {
+		int fd;
+		int newvtno;
+		int fds[MAX_NR_CONSOLES];
+		int vt_cnt = 0;
+		int i;
+
+		for ( i = 0 ; i < MAX_NR_CONSOLES ; i++ )
+		    fds[i] = -1;
+
+		if ((fd = open("/dev/tty0", O_WRONLY, 0) ) < 0
+		    && errno != ENOENT)
+		    error(_("/dev/tty0: cannot open: %m"));
+
+		if (fd >= 0) do
+		{
+		    if ((ioctl(fd, VT_OPENQRY, &newvtno ) < 0))
+			error(_("failed to query next available vt"));
+
+		    if (newvtno == -1)
+			error(_("all vts are in use"));
+
+		    if (newvtno > vtno)
+			error(_("/dev/%s: already in use"), tty);
+
+		    if (newvtno < vtno)
+		    {
+			char vtname[TTY_NAME_MAX+3];
+
+			sprintf( vtname, "tty%d", newvtno );
+
+			if ((fds[vt_cnt++] =
+			    open(vtname, O_RDWR|O_NONBLOCK, 0)) < 0)
+			{
+			    error(_("/dev/%s: cannot open: %m"), tty);
+			}
+		    }
+		} while (newvtno != vtno);
+
+		close(fd);
+		for ( i = 0 ; i < MAX_NR_CONSOLES ; i++ )
+		{
+		    if (fds[i] == -1)
+			break;
+		    close(fds[i]);
+		}
+	    }
+	}
+#endif
+
 	/* Open the tty as standard input. */
 
 	(void) close(0);