[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <87jzs26zl1.fsf@oracle.com>
Date: Wed, 04 Oct 2023 10:56:42 -0700
From: Stephen Brennan <stephen.s.brennan@...cle.com>
To: Randy Dunlap <rdunlap@...radead.org>, 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
Randy Dunlap <rdunlap@...radead.org> writes:
> 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.
Yeah, and info like BTF is much larger, yet this is the config setting
that gets trimmed out by distros :(
(This is not a criticism of BTF, just an observation)
Unfortunately I don't control it and am just trying to work around it :)
> Reviewed-by: Randy Dunlap <rdunlap@...radead.org>
Thanks!
Stephen
>> 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
Powered by blists - more mailing lists