Experimental Physics and
Industrial Control System

Till,

Your program works on my system accessing the EPP port (0x378).

So it must not be a security problem, it must be a problem with my code.

Thanks very much for sending the code.

Mark


-----Original Message-----
From: Till Straumann [mailto:[email protected]] 
Sent: Thursday, July 09, 2009 2:06 PM
To: Mark Rivers
Cc: tech-talk; [email protected]
Subject: Re: Access to IO registers from user-space in recent Linux
versions

The iopl(3) followed by 'in' works fine for me (both, when compiled -m32

or without)

till@tillbook:~/tmp$ uname -a
Linux tillbook 2.6.28-13-generic #45-Ubuntu SMP Tue Jun 30 22:12:12 UTC 
2009 x86_64 GNU/Linux


#include <stdio.h>
#include <sys/io.h>

int main(int argc, char **argv)
{
unsigned char  v;
unsigned short p;

    if ( argc < 2 || 1 != sscanf(argv[1],"%hi",&p) ) {
        fprintf(stderr,"Usage: %s <port>\n",argv[0]);
        return 1;
    }

    if ( iopl(3) ) {
        perror("iopl");
        return 1;
    }

    asm volatile ( "inb %1,%0" : "=a" (v) : "d"(p));

    printf("0x%02x\n",v);
    return 0;
}

-- Till


Mark Rivers wrote:
>
> Folks,
>
>  
>
> I have an EPICS application that directly accesses the parallel port 
> (EPP) registers from user space on Linux.  This is to communicate with

> an XIA Saturn spectroscopy module.
>
>  
>
> In order versions of Linux this worked fine if I ran the application 
> as root, or by calling iopl(3) as root before exec-ing the EPICS 
> application.
>
>  
>
> I am now trying to run this under a recent Linux (Redhat Fedora)
version
>
>  
>
> baja:~>more /proc/version
>
> Linux version 2.6.26.8-57.fc8 ([email protected])
>
> (gcc version 4.1.2 20070925 (Red Hat 4.1.2-33))
>
> #1 SMP Thu Dec 18 18:59:49 EST 2008
>
>  
>
> The EPICS IOC now crashes with a segmentation fault when trying to 
> access the EPP port, even when running as root, and the following 
> entry appears in /var/log/messages
>
>  
>
> Jul  9 11:43:44 baja kernel: dxpApp[27837] general protection 
> ip:80a90a6 sp:ff8ea8ac error:0 in dxpApp[8048000+1f7000]
>
>  
>
> Does anyone know what one needs to do in recent Linux versions to get 
> access to the IO registers from user-space?
>
>  
>
> Thanks,
>
> Mark
>
>  
>
>  
>

Replies:

RE: [APS Beamline_controls] Access to IO registers from user-spacein recent Linux versions Mark Rivers

References:

Access to IO registers from user-space in recent Linux versions Mark Rivers

Re: Access to IO registers from user-space in recent Linux versions Till Straumann

Navigate by Date:

Prev: Re: Access to IO registers from user-space in recent Linux versions John Sinclair

Next: Re: Access to IO registers from user-space in recent Linux versions J. Lewis Muir

Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  <2009>  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024 

Navigate by Thread:

Prev: Re: Access to IO registers from user-space in recent Linux versions David Kline

Next: RE: [APS Beamline_controls] Access to IO registers from user-spacein recent Linux versions Mark Rivers

Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  <2009>  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024