Re: Modules with list

From: Adam J. Richter (adam@yggdrasil.com)
Date: Wed Nov 27 2002 - 20:54:36 EST


On 2002-11-27 22:42:46 GMT, Keith Owens wrote:
>On Wed, 27 Nov 2002 10:19:02 -0800,
>"Adam J. Richter" <adam@yggdrasil.com> wrote:
>> Hmm. We could certainly have a binary editing tool to remove
>>what was the .exit{,func} sections after the link...
>> In this scenario, the .exit{,func} section would be linked
>>in and then discarded by the module loader, by the process of the
>>kernel releasing its .init{,data} areas, or, if you wanted to build
>>a bzImage without CONFIG_HOTPLUG, by using a binary editing tool or
>>perhaps an ld script as I mentioned earlier in this response.
>>
>> The point of the .devexit_p_refs section would just be to
>>set those references to NULL if that was useful. The kernel module
>>load code would do something like:
>
>You have it back to front. The real problem is open code that calls
>functions in sections that have been discarded, that code is an oops
>just waiting to happen. When binutils was changed to detect such
>dangling references, it found a lot of bad code on rarely tested error
>paths. Your method would stop binutils finding the dangling references
>and open the kernel up to bad code again.

        Currently, for __devexit{,func}, this is only detected on
CONFIG_HOTPLUG=n systems. Under my scheme we would always build
.devexit.{text,data} sections, so we could actually test this more
widely, although it would require making a binary tool to delete the
relocations at addresses pointed to by the .devexit_p_ptrs entries.
We could have a regession test that would run that tool on every
module, then run an ld script to delete .devexit.{data,text} and see
if there are any dangling references.

Adam J. Richter __ ______________ 575 Oroville Road
adam@yggdrasil.com \ / Milpitas, California 95035
+1 408 309-6081 | g g d r a s i l United States of America
                         "Free Software For The Rest Of Us."
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