On Thu, Oct 6, 2011 at 9:42 PM, rohan puri [off-list ref] wrote:

On Fri, Oct 7, 2011 at 4:13 AM, Vaibhav Jain [off-list ref] wrote:

quoted

On Thu, Oct 6, 2011 at 11:28 AM, Mulyadi Santosa <
mulyadi.santosa at gmail.com> wrote:

quoted

Hi...

On Thu, Oct 6, 2011 at 02:34, Vaibhav Jain [off-list ref] wrote:

quoted

Hi,

I am trying to run a program that scans memory from a given physical

address

quoted

using /dev/mem.
It uses mmap to map physical address from /dev/mem. So to start with I

used

quoted

/proc/iomem to look up the
physical memory mapping and found the address 00010000 to be the

starting

quoted

address for System ram. But whenever I
provide this address to the program it throws an error of "Operation

not

quoted

permitted".

Probably this could also due to mmap NULL dereferencing protection (at
least that's how I name it :) )

By default, the lowest 65536 byte (10000 in hex) is protected from
mapping etc. It practically render such null dererefencing useless.


--
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

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

Hi,

I tried the same with other addresses (greater than 0x10000 ) also but it
is throwing the same error.
Is there a way to get over this ?

Thanks
Vaibhav Jain



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Hi Vaibhav,

This is how it can be done. Refer link
http://www.theknotter.net/system-memory-dumps-on-linux/

I have attached the modified code which disables the socket creation part
and dumps the output in a file.

Regards,
Rohan Puri

Thanks Rohan for the code but I already have a code that reads memory using
/dev/mem and mmap.
Only difference is I have to manually change the starting address in
program. The problem is whenver I give
any System RAM address the mmap call fails with 'Operation not permitted'. I
googled a little and found that normally
this operation is not allowed and the kernel has to be compiled with
CONFIG_STRICT_DEVMEM disabled to read any memory
location in this way. I also found out about the boot option 'strict-devmem
=0'. I tried both these options but none of them seems to working.
So I am trying to figure out if there is some other setting that I need to
change.
I am doing this on Fedora 15 - 2.6.38 kernel.

Thanks
Vaibhav Jain
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