maximum size of entry in /proc

linuxdoniv · 03-24-2008, 11:19 AM

Hi,

I have a module where I write some information to /proc. With proc file size argument as 4000, I am able to write the info to /proc. But if I increase the size to 40000, trying to write more information, I get segmentation fault.

Is there any restriction on the maximum size of the file that can be written dynamically by a module onto /proc. Do I have to set some arguments
in the kernel to be able to insert a larger file in /proc.

Thanks.....

osor · 03-24-2008, 12:26 PM

I am not aware of any such limitation. On some machines 4096 is the page size, so you might have a subtle problem in your code with allows writing to no more than one page. Perhaps if you showed us the code, it would help us debug.

osor · 03-24-2008, 06:46 PM

I took a look at the code you sent via personal message. You have a statement such as the following:

Code:

return sprintf(buffer, to_be_written);

In general, you can’t do this. You have to look at how many bytes the userspace application requested (in buffer_length in your code) and to be completely correct, you also need to look at the offset.

linuxdoniv · 04-01-2008, 03:41 PM

Thanks for that reply.
I have another problem. It is working fine if I access the data fields in task_struct. But if I access the data fields through the pointer of task_struct structure, and log the data in /proc/process_info, then I get segmentation fault if I vim the process_info file. I tried accessing only the data fields of task_struct , it works. I don't access the data fields of task_struct but the data fields of task->mm->ANY FIELD, it does not work. I am confused about this.

Thanks for any help...