linux-kernel - Re: [PATCH v3 1/1] kernel/config: Introduce CONFIG_DEBUG_INFO

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Message-ID: <ZUKjNJBoglBdRJbg@bombadil.infradead.org>
Date:   Wed, 1 Nov 2023 12:12:52 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Stephen Brennan <stephen.s.brennan@...cle.com>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-debuggers@...r.kernel.org,
        Mike Christie <michael.christie@...cle.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "Christian Brauner (Microsoft)" <brauner@...nel.org>,
        Petr Mladek <pmladek@...e.com>, Marco Elver <elver@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Douglas Anderson <dianders@...omium.org>,
        Maninder Singh <maninder1.s@...sung.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Kees Cook <keescook@...omium.org>,
        Zhaoyang Huang <zhaoyang.huang@...soc.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: Re: [PATCH v3 1/1] kernel/config: Introduce
 CONFIG_DEBUG_INFO_IKCONFIG

On Fri, Oct 27, 2023 at 10:17:56AM -0700, Stephen Brennan wrote:
> The option CONFIG_IKCONFIG allows the gzip compressed kernel
> configuration to be included into vmlinux or a module. In these cases,
> debuggers can access the config data and use it to adjust their behavior
> according to the configuration. However, distributions rarely enable
> this, likely because it uses a fair bit of kernel memory which cannot be
> swapped out.
> 
> This means that in practice, the kernel configuration is rarely
> available to debuggers.
> 
> So, introduce an alternative, CONFIG_DEBUG_INFO_IKCONFIG. This strategy,
> which is only available if IKCONFIG is not already built-in, adds a
> section ".debug_linux_ikconfig", to the vmlinux ELF. It will be stripped
> out of the final images, but will remain in the debuginfo files. So
> debuggers which rely on vmlinux debuginfo can have access to the kernel
> configuration, without incurring a cost to the kernel at runtime.
> 
> The configuration is enabled whenever DEBUG_INFO=y and IKCONFIG!=y. The
> added section is not large compared to debug info sizes. It won't affect
> the runtime kernel at all, and this default will ensure that
> distributions intending to create useful debuginfo will get this new
> addition for kernel debuggers.
> 
> Signed-off-by: Stephen Brennan <stephen.s.brennan@...cle.com>

Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>

Although this begs to support something other than old gz in the future.

  Luis