problem mapping physical address from /dev/mem

[rohan puri]

On Fri, Oct 7, 2011 at 3:51 PM, rohan puri <rohan.puri15 at gmail.com> wrote:

>
>
> On Fri, Oct 7, 2011 at 3:29 PM, rohan puri <rohan.puri15 at gmail.com> wrote:
>
>>
>>
>> On Fri, Oct 7, 2011 at 12:41 PM, Vaibhav Jain <vjoss197 at gmail.com> wrote:
>>
>>> On Thu, Oct 6, 2011 at 9:42 PM, rohan puri <rohan.puri15 at gmail.com>wrote:
>>>
>>>>
>>>>
>>>> On Fri, Oct 7, 2011 at 4:13 AM, Vaibhav Jain <vjoss197 at gmail.com>wrote:
>>>>
>>>>>
>>>>>
>>>>> On Thu, Oct 6, 2011 at 11:28 AM, Mulyadi Santosa <
>>>>> mulyadi.santosa at gmail.com> wrote:
>>>>>
>>>>>> Hi...
>>>>>>
>>>>>> On Thu, Oct 6, 2011 at 02:34, Vaibhav Jain <vjoss197 at gmail.com>
>>>>>> wrote:
>>>>>> > Hi,
>>>>>> >
>>>>>> > I am trying to run a program that scans memory from a given physical
>>>>>> address
>>>>>> > using /dev/mem.
>>>>>> > It uses mmap to map physical address from /dev/mem. So to start with
>>>>>> I used
>>>>>> > /proc/iomem to look up the
>>>>>> > physical memory mapping and found the address 00010000 to be the
>>>>>> starting
>>>>>> > address for System ram. But whenever I
>>>>>> > provide this address to the program it throws an error of "Operation
>>>>>> not
>>>>>> > 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
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Kernelnewbies mailing list
>>>>> Kernelnewbies at kernelnewbies.org
>>>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>>>
>>>>> 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
>>>
>>>
>> Hi Vaibhav,
>>
>> My iomem file : -
>>
>> 00000000-0000ffff : reserved
>> *00010000-0009f3ff : System RAM*
>> 0009f400-0009ffff : reserved
>> 000c0000-000c7fff : Video ROM
>> 000cc000-000ccfff : Adapter ROM
>> 000cd000-000cffff : pnp 00:0c
>> 000e0000-000effff : pnp 00:0c
>> 000f0000-000fffff : reserved
>>   000f0000-000fffff : System ROM
>> *00100000-cf6dffff : System RAM*
>>   01000000-015dadf2 : Kernel code
>>   015dadf3-01ab907f : Kernel data
>>   01bb1000-01d04fff : Kernel bss
>>
>> Now the program which i sent you, with that I am able to read the 1st part
>> of System RAM successfully. I am getting the operation not permitted error
>> from mmap  for second part of System RAM. Can you verify the same on your
>> system. I mean are you able to read the 1st part (if your System RAM is
>> divided) or not ?
>>
>> Regards,
>> Rohan Puri
>>
>
> Another way to get the memory map is install crash module on your system
> and access the memory by accessing the new device /dev/crash instead of
> /dev/mem
>
> Regards,
> Rohan Puri
>

Even I tried after disabling the option CONFIG_STRICT_DEVMEM, but still
cannot access the 2nd part of System RAM. Also my linux is for x86_64 arch,
hence maybe I am able to access the 1st part of System RAM though that is
above 1 MB.

Regards,
Rohan Puri
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