problem mapping physical address from /dev/mem

[Vaibhav Jain]

On Fri, Oct 7, 2011 at 3:45 AM, rohan puri <rohan.puri15 at gmail.com> wrote:

>
>
> 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
>

On my system 'cat /proc/iomem' gives the following

00000000-0000ffff : reserved
*00010000-0008efff : System RAM*
0008f000-0009ffff : reserved
000a0000-000bffff : PCI Bus 0000:00
  000a0000-000bffff : Video RAM area
000c0000-000c7fff : Video ROM
000cd000-000d2dff : Adapter ROM
000d3000-000d53ff : Adapter ROM
000d5800-000d67ff : Adapter ROM
000d6800-000d77ff : Adapter ROM
000e0000-000fffff : reserved
  000f0000-000fffff : System ROM
*00100000-1f3fffff : System RAM*
  00400000-007f0a8f : Kernel code
  007f0a90-00a83d3f : Kernel data
  00b18000-00bfbfff : Kernel bss
1f400000-1fffffff : RAM buffer
7970b000-797a4fff : ACPI Non-volatile

I am unable to access either of System RAM addresses. Both of them give
Operation not permitted.

Thanks
Vaibhav Jain
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20111007/58ae459c/attachment.html