linux-kernel - Re: [PATCH v2 0/4] x86/build: Get rid of vmlinux postlink step

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Message-ID: <CAK7LNATU7fWmpPSm33FSq7B9gnhxRg-QhN_on1Ym9ZxV+PkmnA@mail.gmail.com>
Date: Sat, 15 Mar 2025 16:09:45 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org, x86@...nel.org, 
	Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v2 0/4] x86/build: Get rid of vmlinux postlink step

On Tue, Mar 11, 2025 at 8:06 PM Ard Biesheuvel <ardb+git@...gle.com> wrote:
>
> From: Ard Biesheuvel <ardb@...nel.org>
>
> Kbuild supports an architecture specific Makefile.postlink file that is
> invoked for the vmlinux target after it has been built. This Makefile
> takes 'vmlinux' (which has just been built) as the target, and mangles
> the file and/or constructs other intermediate artifacts from it.
>
> This violates the general philosophy of Make, which is based on rules
> and dependencies, and artifacts that are rebuilt only when any of their
> dependencies have been updated.
>
> Instead, the different incarnations of vmlinux that are consumed by
> different stages of the build should be emitted as distinct files, where
> rules and dependencies are used to define one in terms of the other.
>
> This also works around an error observed here [0], where vmlinux is
> deleted by Make because a subsequent step that consumes it as input
> throws an error.
>
> So refactor the vmlinux shell scripts and build rules so that
> architectures that rely on --emit-relocs to construct vmlinux with
> static relocations preserved will get a separate vmlinux.unstripped file
> carrying those relocations. This removes the need for an imperative
> postlink step, given that any rules that depend on the unstripped
> vmlinux can now simply depend on vmlinux.unstripped, rather than inject
> a build step into Makefile.postlink
>
> S390 should be able to do the same. MIPS and RISC-V perform some
> post-build checks on vmlinux, which is reasonable in principle for a
> postlink step, although deleting vmlinux when the check fails is equally
> unhelpful.
>
> Changes since v1:
> - add vmlinux.unstripped to .gitignore and to the 'clean' target
> - move cmd_strip_relocs into Makefile.vmlinux

Applied to linux-kbuild.
Thanks!


-- 
Best Regards
Masahiro Yamada