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:

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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.

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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

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-- Regards, S. Sengottuvelan.

-- Regards, S. Sengottuvelan.

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-- Regards, S. Sengottuvelan.