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From: scott@slp53.sl.home (Scott Lurndal)
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Subject: Re: memory protection in linux kernels
Newsgroups: comp.unix.programmer,comp.os.linux.embedded
References: <k5n858$g72$1@speranza.aioe.org> <JRTfs.4$Ci6.1@fe03.iad> <k5p8t1$3fq$1@speranza.aioe.org>
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"Mark" <mark_cruzNOTFORSPAM@hotmail.com> writes:
>
>"Scott Lurndal" <scott@slp53.sl.home> wrote in message 
>news:JRTfs.4$Ci6.1@fe03.iad...
>>>I'm debugging my kernel module, which appears to have a memory corruption,
>>>basically a piece of memory allocated by alloc_netdev() for 'net_device'
>>>instance has benn corrupted. I'm wondering if I could apply some 
>>>"read-only"
>>>attribute on this memory, this way I expect to have Oops generated when
>>>someone tries to modify the memory.
>>>
>>>Does it sound reasonable or my ideas are undoable ?
>>>Thanks.
>>>
>>>Mark
>>>
>>
>> Turn on CONFIG_KDB and use kdb to set a watchpoint on the location being
>> corrupted.   The processor will automatically stop and drop into kdb
>> when the location is modified.
>>
>> See the documentation for the bp command in kdb under the Documentation
>> directory in the kernel source tree.
>
>Thank you. The target is ARM-based and runs the kernel 2.6.31.8, which has 
>only KGDB support, i.e. as I understand it allows to debug via rs232. What 
>is the difference with KDB?

KDB is built in; it doesn't require a client on another machine like KGDB;
but kgdb should work for your case since you've an earlier kernel.

KGDB and KDB both part of the kernel 3.x series, even for ARM as I understand it,
although I've seen recent changes fly by on LKML.

ARM processors also have external debug capabilities in some implementations
(e.g. ETM via jtag).

>
>Also, do I have to enable CONFIG_MAGIC_SYSRQ  except CONFIG_KGDB and 
>CONFIG_DEBUG_INFO (CONFIG_FRAME_POINTER is also recommended) ?

The Kconfig files should handle any required dependencies for you.

scott