linux-kernel - Re: [PATCH] objtool: Fix memory leak in decode

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Date:   Sun, 22 Oct 2017 14:55:56 +0530
From:   Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] objtool: Fix memory leak in decode_instructions()

On Thursday 19 October 2017 08:02 PM, Josh Poimboeuf wrote:
> On Thu, Oct 19, 2017 at 09:31:37AM -0500, Josh Poimboeuf wrote:
>> On Fri, Oct 13, 2017 at 11:20:58AM +0530, Kamalesh Babulal wrote:
>>> On Friday 13 October 2017 10:36 AM, Josh Poimboeuf wrote:
>>>> On Fri, Oct 13, 2017 at 10:14:36AM +0530, Kamalesh Babulal wrote:
>>>>> On Thursday 12 October 2017 09:40 PM, Josh Poimboeuf wrote:
>>>>>> On Thu, Oct 12, 2017 at 02:32:14PM +0530, Kamalesh Babulal wrote:
>>>>>>> free the allocated insn before returning, when an error occurs
>>>>>>> before adding insn to file->insn_list.
>>>>>>>
>>>>>>> Signed-off-by: Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
>>>>>>
>>>>>> Any chance you're working on porting objtool to ppc64le? :-)
>>>>>>
>>>>>> Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
>>>>>>
>>>>>
>>>>> Thanks for the review. I have started working on it :)
>>>>
>>>> Good!  Let me know if you have any questions.
>>>
>>> Thank you, I am sure I will have lots of them.
>>>
>>>>
>>>> I originally wrote objtool with arch-independence in mind, though with
>>>> the new "objtool 2.0" rewrite, it unfortunately became more
>>>> x86-specific.
>>>>
>>>> I was hoping to work on making it more arch-independent, and then start
>>>> porting it to other arches, but it may be a few months before I have the
>>>> time to do so.  So any work you want to there would be great.
>>>>
>>>
>>> Sure, will keep that in mind to abstract arch-independent code in to common
>>> files and push arch-dependent code into arch/ directory for both
>>> ppc64le/x86.
>>
>> Kamalesh, since you might be working on this soon, here's a bit of a
>> brain dump in case it helps.
>>
>> I have a vague idea for eventually improving objtool, which might make
>> arch-independence easier.  I wonder if we could use a GCC plugin to add
>> annotations in special sections, which are then read by objtool to help
>> it understand what's going on in the code.
>>
>> I suspect the plugins would need to be arch-specific.  But then maybe
>> that would allow objtool itself to be completely arch-independent.
>> Eventually, if we had similar clang plugins, objtool could become
>> compiler-independent as well.
>>
>> Unfortunately I haven't had a chance to think about it any more deeply
>> than that.  Just something to think about.
>>
>> Or maybe it makes sense to port objtool to ppc first, before trying to
>> abstract the arch-specific parts into plugins.  I dunno.
>>

Thanks for sharing the thoughts on making objtool arch-independent.
I have not followed the discussions closely on GCC plugin to add
annotations/DWARF data. I will read through the ideas, before
commenting on them.


>> Also, another idea that has been suggested, is to use DWARF data as
>> input to objtool.  I have my doubts about that idea, but if it worked,
>> that might be another way to help objtool achieve arch-independence.
>>
>> For a previous discussion of these ideas, see:
>>
>>   https://lkml.kernel.org/r/20170831044209.4hodx2dasad66yab@treble
>
> Also, any chance you'll be in Prague for the conferences next week?  If
> so, we could discuss it more in person.
>

I will not be attending the conference.

-- 
cheers,
Kamalesh.