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

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Date:   Thu, 19 Oct 2017 09:32:26 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] objtool: Fix memory leak in decode_instructions()

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.
> 
> 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.

-- 
Josh