linux-kernel - Re: [PATCH v4 06/10] modpost: Add modinfo flag to livepatch modules

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Date:   Mon, 19 Aug 2019 11:55:19 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Miroslav Benes <mbenes@...e.cz>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        live-patching@...r.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v4 06/10] modpost: Add modinfo flag to livepatch modules

On 8/18/19 11:50 PM, Masahiro Yamada wrote:
> Hi Joe,
> 
> On Sat, Aug 17, 2019 at 4:01 AM Joe Lawrence <joe.lawrence@...hat.com> wrote:
>>
>>
>> I didn't realize that we're supposed to be able to still build external
>> modules after "make clean".  If that's the case, then one might want to
>> build an external klp-module after doing that.
> 
> Yes. 'make clean' must keep all the build artifacts
> needed for building external modules.
> 
> 
>> With that in mind, shouldn't Symbols.list to persist until mrproper?
>> And I think modules-livepatch could go away during clean, what do you think?
>>
>> -- Joe
> 
> 
> Symbols.list should be kept by the time mrproper is run.
> So, please add it to MRROPER_FILES instead of CLEAN_FILES.
> 
> modules.livepatch is a temporary file, so you can add it to
> CLEAN_FILES.
> 

OK, I'll add those to their respective lists.

> How is this feature supposed to work for external modules?
> 
> klp-convert receives:
> "symbols from vmlinux" + "symbols from no-klp in-tree modules"
> + "symbols from no-klp external modules" ??
> 

I don't think that this use-case has been previously thought out 
(Miroslav, correct me if I'm wrong here.)

I did just run an external build of a copy of 
samples/livepatch/livepatch-annotated-sample.c:

  - modules.livepatch is generated in external dir
  - klp-convert is invoked for the livepatch module
  - the external livepatch module successfully loads

But that was only testing external livepatch modules.

I don't know if we need/want to support general external modules 
supplementing Symbols.list, at least for the initial klp-convert commit. 
  I suppose external livepatch modules would then need to specify 
additional Symbols.list(s) files somehow as well.

> 
> BTW, 'Symbols.list' sounds like a file to list out symbols
> for generic purposes, but in fact, the
> file format is very specific for the klp-convert tool.
> Perhaps, is it better to rename it so it infers
> this is for livepatching? What do you think?
> 

I don't know if the "Symbols.list" name and leading uppercase was based 
on any convention, but something like symbols.klp would be fine with me.

Thanks,

-- Joe