bph / bpha not working.

[Avi Nehori]

I'm using 2.4.21 kernel (and also tried 2.6.18 with the same behavior).
the memory address is being written through a kernel module .
please see below :

[0]kdb> md 0xa0f7bc94
0xa0f7bc94 00000000 00000001 00000003 00000000   ................
[0]kdb> bpha 0xa0f7bc94 dataw 4
[0]kdb> go


the breakpoint is not called even though the memory address being changed:
[0]kdb> md 0xa0f7bc94
0xa0f7bc94 00000064 00000001 00000003 00000000   d...............


jidong xiao wrote:
> On Wed, May 7, 2008 at 2:41 PM, Avi Nehori <anehori at checkpoint.com> wrote:
>   
>> Thanks for your reply Jay,
>> I'm running i386 and the thing is that when i set the breakpoint on a
>> memory address(trying to catch a memory
>> corruption bug) the watch point is not getting hit when the memory is
>> written.
>> I'm following the kdb documentation which says :
>>
>> "The |bph| and |bpha| commands can be used (provided the architecture
>> supports use of hardware registers) to apply read and write breakpoints.
>> This means we can get control whenever data is read from or written into
>> a particular address. This can be extremely handy when debugging
>> data/memory corruption problems, where you can use it to identify the
>> corrupting code/process."
>>
>> *Examples*
>>
>>    *To enter the kernel debugger whenever four bytes are written into
>>    address 0xc0204060:*
>>    | [0]kdb> bph 0xc0204060 dataw 4
>>
>>
>>    so i followed the documentation and set a breakpoint using bph (and
>>    also bpha) on a memory address
>>    exactly as the above example ,but when i modify the memory address
>>    ,the breakpoint does not hit....
>>    any idea what is wrong here ?
>>    any help will be very appreciated .
>>    Thanks!
>>
>>     
>
> What the kernel version are you using? and how do you modify the memory address?
>
> Regards
> Jason Xiao
>
>   
>>    ||
>>
>>
>>    ||
>>    |
>>
>>
>>
>>
>> Jay Lan wrote:
>>     
>>> Avi Nehori wrote:
>>>
>>>       
>>>> Hi,
>>>> I'm trying to set a watch point with bpha as follows :
>>>> bpha address dataw 4
>>>> but the watchpoint is never called when the memory address is changed.
>>>> is it a know bug ?
>>>> is there a patch ?
>>>>
>>>>         
>>> I heard bph/bpha worked on x86_64. However, hardware breakpoint
>>> was not implemented on IA64. Were you on IA64?
>>>
>>> Greg Banks of SGI (gnb at sgi.com) provided patches for IA64. Many
>>> thanks to Greg!
>>> 1) gnb-kdb-implement-bpha-v3
>>>    This patch implemented bph/bpha on IA64.
>>> 2) gnb-test-kdb-bph
>>>    This patch provided a test infrastructure to test all the ia64
>>>    data* breakpoint features.
>>>
>>> I have uploaded the patches to the download area.
>>> ftp://oss.sgi.com/projects/kdb/download/v4.4
>>>
>>>
>>> Cheers,
>>>  - jay
>>>
>>>
>>>       
>>>> Thanks.
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>>>>         
>>>
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