i/o opening error for PCI access

i/o opening error for PCI access

[Sengottuvelan S]

Hi All,

I am trying to access /dev/mem in my user process. I could not access
because not a privileged access. I tried to use iopl(3) call in linux 2.6,
but i am getting unresolved symbol for this.  Is any other way to get access
in user process. I am not sure how to solve this. Can you someone throw some
light on this.

   if(iopl(3)){
        fprintf(stderr, "Cannot get I/O permissions (being root helps)");
        return -1;
    }
  if ((fd = open("/dev/mem", O_RDWR | O_SYNC)) < 0) {
        fprintf(stderr, "Failed to open /dev/mem");
        return -1;
    }

-- 
Regards,
S. Sengottuvelan.

-- 
Regards,
S. Sengottuvelan.
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i/o opening error for PCI access

[Prasad Joshi]

On Sun, Apr 3, 2011 at 6:11 PM, Sengottuvelan S
<sengottuvelan.s@gmail.com> wrote:
> Hi All,
>
> I am trying to access /dev/mem in my user process. I could not access
> because not a privileged access. I tried to use iopl(3) call in linux 2.6,

I am not sure, but after reading the manpage, it looks like iopl will
give access to the IO ports not the files.

> but i am getting unresolved symbol for this.? Is any other way to get access
> in user process. I am not sure how to solve this. Can you someone throw some
> light on this.
>
> ?? if(iopl(3)){
> ??????? fprintf(stderr, "Cannot get I/O permissions (being root helps)");
> ??????? return -1;
> ??? }
> ? if ((fd = open("/dev/mem", O_RDWR | O_SYNC)) < 0) {
> ??????? fprintf(stderr, "Failed to open /dev/mem");
> ??????? return -1;
> ??? }

If you look at the file permission, you will notice only root has
permission to write the /dev/mem

$ ls -l /dev/mem
crw-r----- 1 root kmem 1, 1 2011-04-03 08:42 /dev/mem

Opening it for read/write will surely fail.

Thanks and Regards,
Prasad

>
> --
> Regards,
> S. Sengottuvelan.
>
> --
> Regards,
> S. Sengottuvelan.
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>

i/o opening error for PCI access

[Sengottuvelan S]

Hi Prasad,

question is:  anyother way to access like iopl(3) function?.

FYI, With iopl it is possible. But in my kernel i could not locate iopl
function. Is there any similar function like iopl so that i will set  the
permission as root id.

On Sun, Apr 3, 2011 at 3:47 PM, Prasad Joshi <prasadjoshi124@gmail.com>wrote:

> On Sun, Apr 3, 2011 at 6:11 PM, Sengottuvelan S
> <sengottuvelan.s@gmail.com> wrote:
> > Hi All,
> >
> > I am trying to access /dev/mem in my user process. I could not access
> > because not a privileged access. I tried to use iopl(3) call in linux
> 2.6,
>
> I am not sure, but after reading the manpage, it looks like iopl will
> give access to the IO ports not the files.
>
> > but i am getting unresolved symbol for this.  Is any other way to get
> access
> > in user process. I am not sure how to solve this. Can you someone throw
> some
> > light on this.
> >
> >    if(iopl(3)){
> >         fprintf(stderr, "Cannot get I/O permissions (being root helps)");
> >         return -1;
> >     }
> >   if ((fd = open("/dev/mem", O_RDWR | O_SYNC)) < 0) {
> >         fprintf(stderr, "Failed to open /dev/mem");
> >         return -1;
> >     }
>
> If you look at the file permission, you will notice only root has
> permission to write the /dev/mem
>
> $ ls -l /dev/mem
> crw-r----- 1 root kmem 1, 1 2011-04-03 08:42 /dev/mem
>
> Opening it for read/write will surely fail.
>
> Thanks and Regards,
> Prasad
>
> >
> > --
> > Regards,
> > S. Sengottuvelan.
> >
> > --
> > Regards,
> > S. Sengottuvelan.
> >
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies at kernelnewbies.org
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
> >
>



-- 
Regards,
S. Sengottuvelan.
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i/o opening error for PCI access

[Mulyadi Santosa]

On Mon, Apr 4, 2011 at 07:19, Sengottuvelan S <sengottuvelan.s@gmail.com> wrote:
> Hi Prasad,
>
> question is:? anyother way to access like iopl(3) function?.

libcap?
http://www.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.4/capfaq-0.2.txt

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com