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/**[txh]********************************************************************
Copyright (c) 2004 by Salvador E. Tropea.
Covered by the GPL license.
Module: Linux VT.
Comments:
Helper to find a free VT. That's 100% Linux specific.@p
The code comes from "lconsole.c" from Allegro project and was originally
created by Marek Habersack and then modified by George Foot. I addapted it
to my needs and changed license from giftware to GPL.@p
***************************************************************************/
#define _GNU_SOURCE
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#ifdef __APPLE__
#include <util.h>
#endif /* __APPLE__ */
#include "mi_gdb.h"
#if !defined(__linux__)
int mi_look_for_free_vt()
{
return -1;
}
mi_aux_term *gmi_look_for_free_vt()
{
return NULL;
}
#else
#include <linux/vt.h>
/**[txh]********************************************************************
Description:
Look for a free and usable Linux VT. Low level, use
@x{gmi_look_for_free_vt}.
Return: The VT number or <0 on error.
***************************************************************************/
int mi_look_for_free_vt()
{/* Code from Allegro. */
int tty, console_fd, fd;
unsigned short mask;
char tty_name[16];
struct vt_stat vts;
/* Now we need to find a VT we can use. It must be readable and
* writable by us, if we're not setuid root. VT_OPENQRY itself
* isn't too useful because it'll only ever come up with one
* suggestion, with no guarrantee that we actually have access
* to it.
*
* At some stage I think this is a candidate for config
* file overriding, but for now we'll stat the first N consoles
* to see which ones we can write to (hopefully at least one!),
* so that we can use that one to do ioctls. We used to use
* /dev/console for that purpose but it looks like it's not
* always writable by enough people.
*
* Having found and opened a writable device, we query the state
* of the first sixteen (fifteen really) consoles, and try
* opening each unused one in turn.
*/
console_fd=open("/dev/console",O_WRONLY);
if (console_fd<0)
{
int n;
/* Try some ttys instead... */
for (n=1; n<=24; n++)
{
snprintf(tty_name,sizeof(tty_name),"/dev/tty%d",n);
console_fd=open(tty_name,O_WRONLY);
if (console_fd>=0)
break;
}
if (n>24)
return -1;
}
/* Get the state of the console -- in particular, the free VT field */
if (ioctl(console_fd,VT_GETSTATE,&vts))
return -2;
close(console_fd);
/* We attempt to set our euid to 0; if we were run with euid 0 to
* start with, we'll be able to do this now. Otherwise, we'll just
* ignore the error returned since it might not be a problem if the
* ttys we look at are owned by the user running the program. */
seteuid(0);
/* tty0 is not really a console, so start counting at 2. */
fd=-1;
for (tty=1, mask=2; mask; tty++, mask<<=1)
if (!(vts.v_state & mask))
{
snprintf(tty_name,sizeof(tty_name),"/dev/tty%d",tty);
fd=open(tty_name,O_RDWR);
if (fd!=-1)
{
close(fd);
break;
}
}
seteuid(getuid());
if (!mask)
return -3;
return tty;
}
/**[txh]********************************************************************
Description:
Look for a free and usable Linux VT to be used by the child.
Return: A new mi_aux_term structure, you can use @x{gmi_end_aux_term} to
release it.
***************************************************************************/
mi_aux_term *gmi_look_for_free_vt()
{
int vt=mi_look_for_free_vt();
mi_aux_term *res;
if (vt<0)
return NULL;
res=(mi_aux_term *)malloc(sizeof(mi_aux_term));
if (!res)
return NULL;
res->pid=-1;
asprintf(&res->tty,"/dev/tty%d",vt);
return res;
}
#endif
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