Debug Kernel Modules With KGDB

Debug Kernel Modules With KGDB

[Raghavendra]

On Monday 01 December 2014 03:26 PM, Freeman Zhang wrote:
> Hi list,
>
> I've been trying to setup a debug environment for linux
> kernel(v3.4,Android,ARM) with kgdb. It worked fine untill I tried to use
> it to debug a module. Under the instruction from LDD, I add module debug
> info in gdb with command:
>
> 	add-symbol-file test-module.ko  address
>
> LDD uses `cat /sys/module/test-module/sections/.text` to get the address
> where the module has been loaded. However, I got:
> 	
> 	0x00000000
Try reading the file as a root.
$ sudo cat /sys/module/test-module/sections/.text
>
> When I use `lsmod`, I got:
>
> 	test-module 15278 0 - Live 0x00000000 (O)
>
> Why nothing but 0x00000000 ??
>
> So I have to do some research in kernel/module.c, and find out that
> struct module -> module_core = 0xbf000000. But when I try these in gdb:
>
> 	add-symbol-file test-module.ko  0xbf000000
> 	break one_of_my_function
>
> I got:
>
> 	Cannot access memory at address 0xbf002350
>
> :(
> Could somebody help?
>
>
> All the best!
> Freeman Zhang
>
> 	
> 	
>
>
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies


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Debug Kernel Modules With KGDB

[Freeman Zhang]

Hi list,

I've been trying to setup a debug environment for linux
kernel(v3.4,Android,ARM) with kgdb. It worked fine untill I tried to use
it to debug a module. Under the instruction from LDD, I add module debug
info in gdb with command:

	add-symbol-file test-module.ko  address

LDD uses `cat /sys/module/test-module/sections/.text` to get the address
where the module has been loaded. However, I got:
	
	0x00000000

When I use `lsmod`, I got:

	test-module 15278 0 - Live 0x00000000 (O)

Why nothing but 0x00000000 ??

So I have to do some research in kernel/module.c, and find out that
struct module -> module_core = 0xbf000000. But when I try these in gdb:

	add-symbol-file test-module.ko  0xbf000000
	break one_of_my_function

I got:

	Cannot access memory at address 0xbf002350

:(
Could somebody help?


All the best!
Freeman Zhang

	
	


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Debug Kernel Modules With KGDB

[Freeman Zhang]

Hi Raghavendra,

Thanks for your reply, but `sudo` doesn't solve the problem :(


All the best!

Freeman Zhang

-------- Original Message --------
> On Monday 01 December 2014 03:26 PM, Freeman Zhang wrote:
>> Hi list,
>>
>> I've been trying to setup a debug environment for linux
>> kernel(v3.4,Android,ARM) with kgdb. It worked fine untill I tried to use
>> it to debug a module. Under the instruction from LDD, I add module debug
>> info in gdb with command:
>>
>>     add-symbol-file test-module.ko  address
>>
>> LDD uses `cat /sys/module/test-module/sections/.text` to get the address
>> where the module has been loaded. However, I got:
>>     
>>     0x00000000
> Try reading the file as a root.
> $ sudo cat /sys/module/test-module/sections/.text
>>
>> When I use `lsmod`, I got:
>>
>>     test-module 15278 0 - Live 0x00000000 (O)
>>
>> Why nothing but 0x00000000 ??
>>
>> So I have to do some research in kernel/module.c, and find out that
>> struct module -> module_core = 0xbf000000. But when I try these in gdb:
>>
>>     add-symbol-file test-module.ko  0xbf000000
>>     break one_of_my_function
>>
>> I got:
>>
>>     Cannot access memory at address 0xbf002350
>>
>> :(
>> Could somebody help?
>>
>>
>> All the best!
>> Freeman Zhang
>>
>>     
>>     
>>
>>
>>
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies at kernelnewbies.org
>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> 
> 
> -------------------------------------------------------------------------------------------------------------------------------
> 
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> 
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> disclosure, dissemination, forwarding, printing or copying of this email
> is strictly prohibited and appropriate legal action will be taken.
> -------------------------------------------------------------------------------------------------------------------------------
> 
> 
> 
> 
> 
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> 

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Debug Kernel Modules With KGDB

[Raghavendra]

Hi Zhang,

On Monday 01 December 2014 04:32 PM, Freeman Zhang wrote:
> Hi Raghavendra,
>
> Thanks for your reply, but `sudo` doesn't solve the problem :(
Well then I guess 'sudo' isn't implemented in android. Any way, 
ultimately you may wan't to login as root and then try reading the file 
in order to get the address.
Regards,
Raghavendra
>
> All the best!
>
> Freeman Zhang
>
> -------- Original Message --------
>> On Monday 01 December 2014 03:26 PM, Freeman Zhang wrote:
>>> Hi list,
>>>
>>> I've been trying to setup a debug environment for linux
>>> kernel(v3.4,Android,ARM) with kgdb. It worked fine untill I tried to use
>>> it to debug a module. Under the instruction from LDD, I add module debug
>>> info in gdb with command:
>>>
>>>      add-symbol-file test-module.ko  address
>>>
>>> LDD uses `cat /sys/module/test-module/sections/.text` to get the address
>>> where the module has been loaded. However, I got:
>>>      
>>>      0x00000000
>> Try reading the file as a root.
>> $ sudo cat /sys/module/test-module/sections/.text
>>> When I use `lsmod`, I got:
>>>
>>>      test-module 15278 0 - Live 0x00000000 (O)
>>>
>>> Why nothing but 0x00000000 ??
>>>
>>> So I have to do some research in kernel/module.c, and find out that
>>> struct module -> module_core = 0xbf000000. But when I try these in gdb:
>>>
>>>      add-symbol-file test-module.ko  0xbf000000
>>>      break one_of_my_function
>>>
>>> I got:
>>>
>>>      Cannot access memory at address 0xbf002350
>>>
>>> :(
>>> Could somebody help?
>>>
>>>
>>> All the best!
>>> Freeman Zhang
>>>
>>>      
>>>      
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Kernelnewbies mailing list
>>> Kernelnewbies at kernelnewbies.org
>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>
>> -------------------------------------------------------------------------------------------------------------------------------
>>
>> [ C-DAC is on Social-Media too. Kindly follow us at:
>> Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ]
>>
>> This e-mail is for the sole use of the intended recipient(s) and may
>> contain confidential and privileged information. If you are not the
>> intended recipient, please contact the sender by reply e-mail and destroy
>> all copies and the original message. Any unauthorized review, use,
>> disclosure, dissemination, forwarding, printing or copying of this email
>> is strictly prohibited and appropriate legal action will be taken.
>> -------------------------------------------------------------------------------------------------------------------------------
>>
>>
>>
>>
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies at kernelnewbies.org
>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>


-------------------------------------------------------------------------------------------------------------------------------
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Debug Kernel Modules With KGDB

[Freeman Zhang]

Hi Raghavendra,

Yes, you are right, 'sudo' isn't implemented in android. However, `su`
enable me to read the .text as root. It's the same, 0x00000000.

So I guess something else should be wrong.


Thanks anyway!

Freeman Zhang

-------- Original Message --------
> Hi Zhang,
> 
> On Monday 01 December 2014 04:32 PM, Freeman Zhang wrote:
>> Hi Raghavendra,
>>
>> Thanks for your reply, but `sudo` doesn't solve the problem :(
> Well then I guess 'sudo' isn't implemented in android. Any way,
> ultimately you may wan't to login as root and then try reading the file
> in order to get the address.
> Regards,
> Raghavendra
>>
>> All the best!
>>
>> Freeman Zhang
>>
>> -------- Original Message --------
>>> On Monday 01 December 2014 03:26 PM, Freeman Zhang wrote:
>>>> Hi list,
>>>>
>>>> I've been trying to setup a debug environment for linux
>>>> kernel(v3.4,Android,ARM) with kgdb. It worked fine untill I tried to
>>>> use
>>>> it to debug a module. Under the instruction from LDD, I add module
>>>> debug
>>>> info in gdb with command:
>>>>
>>>>      add-symbol-file test-module.ko  address
>>>>
>>>> LDD uses `cat /sys/module/test-module/sections/.text` to get the
>>>> address
>>>> where the module has been loaded. However, I got:
>>>>           0x00000000
>>> Try reading the file as a root.
>>> $ sudo cat /sys/module/test-module/sections/.text
>>>> When I use `lsmod`, I got:
>>>>
>>>>      test-module 15278 0 - Live 0x00000000 (O)
>>>>
>>>> Why nothing but 0x00000000 ??
>>>>
>>>> So I have to do some research in kernel/module.c, and find out that
>>>> struct module -> module_core = 0xbf000000. But when I try these in gdb:
>>>>
>>>>      add-symbol-file test-module.ko  0xbf000000
>>>>      break one_of_my_function
>>>>
>>>> I got:
>>>>
>>>>      Cannot access memory at address 0xbf002350
>>>>
>>>> :(
>>>> Could somebody help?
>>>>
>>>>
>>>> All the best!
>>>> Freeman Zhang
>>>>
>>>>          
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Kernelnewbies mailing list
>>>> Kernelnewbies at kernelnewbies.org
>>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>
>>> -------------------------------------------------------------------------------------------------------------------------------
>>>
>>>
>>> [ C-DAC is on Social-Media too. Kindly follow us at:
>>> Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ]
>>>
>>> This e-mail is for the sole use of the intended recipient(s) and may
>>> contain confidential and privileged information. If you are not the
>>> intended recipient, please contact the sender by reply e-mail and
>>> destroy
>>> all copies and the original message. Any unauthorized review, use,
>>> disclosure, dissemination, forwarding, printing or copying of this email
>>> is strictly prohibited and appropriate legal action will be taken.
>>> -------------------------------------------------------------------------------------------------------------------------------
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Kernelnewbies mailing list
>>> Kernelnewbies at kernelnewbies.org
>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>
> 
> 
> -------------------------------------------------------------------------------------------------------------------------------
> 
> [ C-DAC is on Social-Media too. Kindly follow us at:
> Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ]
> 
> This e-mail is for the sole use of the intended recipient(s) and may
> contain confidential and privileged information. If you are not the
> intended recipient, please contact the sender by reply e-mail and destroy
> all copies and the original message. Any unauthorized review, use,
> disclosure, dissemination, forwarding, printing or copying of this email
> is strictly prohibited and appropriate legal action will be taken.
> -------------------------------------------------------------------------------------------------------------------------------
> 
> 

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