linux-kernel - Re: [PATCH v3] kbuild: add debug level and macro defs options

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Date:   Tue, 23 Aug 2022 01:42:41 +0300
From:   Dmitrii Bundin <dmitrii.bundin.a@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Isabella Basso <isabbasso@...eup.net>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Fangrui Song <maskray@...gle.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nathan Chancellor <nathan@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v3] kbuild: add debug level and macro defs options

On Tue, Aug 23, 2022 at 12:36 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> or perhaps that simply needs to be `-g -gsplit-dwarf`?  In which case,
> that if/else could just be re-arranged.

How about simply assigning DEBUG_CFLAGS   := -g at the very beginning
without any conditions? This would provide the default with the
possibility of overriding later and -gsplit-dwarf does not necessarily
come with -g implicitly.

> Honestly, I really don't think we need to be wrapping every compiler
> command line flag under the sun in a kconfig option.

This indeed sounds reasonable to me. So the key point here is to not
bloat the kconfig with options related to every compiler flag. But I
think it still might be useful to provide some option that would
include sort of full debug information compilers may produce. With
this approach there would be, in fact 3 different levels of debug
information supported by Kconfig: reduced, default and full. The full
level would increase everything like -g3, and -fdebug-macro for Clang,
and probably others.

> Or add -g1 to CONFIG_DEBUG_INFO_REDUCED.

I ran some tests and there was indeed some decrease in size. That
combination probably might be useful.

Any thoughts?

Regards
Dmitrii