linux-kernel - Re: [RFC PATCH 5/6] x86/boot: Move early kernel mapping code into startup/

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Message-ID: <Z_LNJO3q5QN82LN0@gmail.com>
Date: Sun, 6 Apr 2025 20:51:16 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	Ard Biesheuvel <ardb@...nel.org>,
	Tom Lendacky <thomas.lendacky@....com>,
	Dionna Amalie Glaze <dionnaglaze@...gle.com>,
	Kevin Loughlin <kevinloughlin@...gle.com>
Subject: Re: [RFC PATCH 5/6] x86/boot: Move early kernel mapping code into
 startup/


* Ard Biesheuvel <ardb+git@...gle.com> wrote:

> From: Ard Biesheuvel <ardb@...nel.org>
> 
> The startup code that constructs the kernel virtual mapping runs from
> the 1:1 mapping of memory itself, and therefore, cannot use absolute
> symbol references. Move this code into a separate source file under
> arch/x86/boot/startup/ where all such code will be kept from now on.
> 
> Since all code here is constructed in a manner that ensures that it
> tolerates running from the 1:1 mapping of memory, any uses of the
> RIP_REL_REF() macro can be dropped, along with __head annotations for
> placing this code in a dedicated startup section.
> 
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> ---
>  arch/x86/boot/startup/Makefile     |   2 +-
>  arch/x86/boot/startup/map_kernel.c | 232 ++++++++++++++++++++
>  arch/x86/kernel/head64.c           | 228 +------------------
>  3 files changed, 234 insertions(+), 228 deletions(-)

So this patch breaks the x86-64 allmodconfig build:

 ERROR: modpost: "page_offset_base" [arch/x86/crypto/aegis128-aesni.ko] undefined!
 ERROR: modpost: "vmemmap_base" [arch/x86/crypto/aegis128-aesni.ko] undefined!
 ERROR: modpost: "page_offset_base" [arch/x86/crypto/aesni-intel.ko] undefined!
 ERROR: modpost: "vmemmap_base" [arch/x86/crypto/aesni-intel.ko] undefined!

I suppose EXPORT_SYMBOL() in the new startup code isn't properly 
extracted?

Thanks,

	Ingo