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

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Message-ID: <2d690a95-67c6-45cb-91a1-4fbac09e1224@infradead.org>
Date:   Wed, 4 Oct 2023 10:52:23 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Stephen Brennan <stephen.s.brennan@...cle.com>,
        Arnd Bergmann <arnd@...db.de>
Cc:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-debuggers@...r.kernel.org
Subject: Re: [PATCH 1/1] kernel/config: Introduce CONFIG_DEBUG_INFO_IKCONFIG

Hi,

On 10/4/23 09:58, 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.

x86_64 allmodconfig is 91 KB gzipped... oh well.

Reviewed-by: Randy Dunlap <rdunlap@...radead.org>

> 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.
> 
> Signed-off-by: Stephen Brennan <stephen.s.brennan@...cle.com>
> ---
>  include/asm-generic/vmlinux.lds.h |  3 ++-
>  kernel/Makefile                   |  1 +
>  kernel/configs-debug.S            | 18 ++++++++++++++++++
>  lib/Kconfig.debug                 | 14 ++++++++++++++
>  4 files changed, 35 insertions(+), 1 deletion(-)
>  create mode 100644 kernel/configs-debug.S


-- 
~Randy