linux-kernel - Re: [RFC PATCH 0/3] kallsyms: add option to include relative filepaths into kallsyms

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Message-Id: <20220818133918.1112657-1-alexandr.lobakin@intel.com>
Date:   Thu, 18 Aug 2022 15:39:18 +0200
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        linux-kbuild@...r.kernel.org, live-patching@...r.kernel.org,
        lkp@...el.com, stable@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] kallsyms: add option to include relative filepaths into kallsyms

From: Greg KH <gregkh@...uxfoundation.org>
Date: Thu, 18 Aug 2022 14:20:06 +0200

> On Thu, Aug 18, 2022 at 01:53:03PM +0200, Alexander Lobakin wrote:
> > This is an early RFC to not rewrite stuff one more time later on if
> > the implementation is not acceptable or any major design changes are
> > required. For the TODO list, please scroll to the end.
> > 
> > Make kallsyms independent of symbols positions in vmlinux (or module)
> > by including relative filepath in each symbol's kallsyms value. I.e.
> > 
> > dev_gro_receive -> net/core/gro.c:dev_gro_receive
> > 
> > For the implementation details, please look at the patch 3/3.
> > Patch 2/3 is just a stub, I plan to reuse kallsyms enhancement from
> > the Rust series for it.
> > Patch 1/3 is a fix of one modpost macro straight from 2.6.12-rc2.
> > 
> > A nice side effect is that it's now easier to debug the kernel, as
> > stacktraces will now tell every call's place in the file tree:
> 
> That's a side effect, but that does not explain _why_ you want this
> change.
> 
> What is this good for?  Who can use it?  Why is it worth added build
> times?

I think I wrote that we need to get rid of this positioned-based
search for kallsyms, at least for livepatching and probes, didn't
I?
OTOH I didn't write that originally that was a prereq for FG-KASLR,
but then I decided it deserves a separate series =\ Thanks for
mentioning this, so I wrote it here now and will not forget this
time to mention it in the cover letter for v2.

> 
> You don't tell us anything except what this does :(
> 
> thanks,
> 
> greg k-h

Thanks,
Olek