linux-kernel - Re: [PATCH v2] efistub: Only link libstub to final vmlinux

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Message-ID: <CAAhV-H4AasfFet_Gi_mVyte3RPMH3qBS73dBfF-=Gd7HJ6ZPEw@mail.gmail.com>
Date: Fri, 21 Nov 2025 22:36:39 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Will Deacon <will@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>, Catalin Marinas <catalin.marinas@....com>, 
	Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	"Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>, Tiezhu Yang <yangtiezhu@...ngson.cn>, 
	Ard Biesheuvel <ardb@...nel.org>, loongarch@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-riscv@...ts.infradead.org, 
	linux-efi@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] efistub: Only link libstub to final vmlinux

On Mon, Nov 17, 2025 at 7:33 PM Will Deacon <will@...nel.org> wrote:
>
> On Sat, Nov 15, 2025 at 11:16:42AM +0800, Huacai Chen wrote:
> > On Wed, Nov 12, 2025 at 2:00 AM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> > >
> > > On Mon, Nov 10, 2025 at 03:00:00PM +0800, Huacai Chen wrote:
> > > > On Mon, Nov 10, 2025 at 9:19 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
> > > > > If I understand correctly, I should modify this patch to remove the
> > > > > changes of arm and riscv for now, do the changes only when there is
> > > > > a real problem or requirement some day, right? If no more comments,
> > > > > I will send v3 later.
> > > >
> > > > Now everyone involved agrees that the efistub code is correct, so the
> > > > proper solution is to fix the compiler.
> > >
> > > Hm?  I don't see how it's a compiler bug.  It's really just an objtool
> > > limitation.
> > >
> > > > Changing efistub code and changing objtool (ignore __efistub prefix)
> > > > are both workarounds, but I think changing objtool is a little more
> > > > reasonable. Maybe Josh has different ideas?
> > >
> > > I thought the conversation had converged on what Tiezhu mentioned above,
> > > which is to skip objtool on libstub for loongarch, but leave the other
> > > arches alone.  That way objtool behavior is consistent between loongarch
> > > and x86, and objtool doesn't need to ignore any prefixes.
> > >
> > > So basically, the v2 patch minus the arm64/riscv changes.
> >
> > Hi, ARM64 and RISC-V maintainers,
> >
> > Would you mind that this patch modifies the three architectures
> > together (they are exactly the same style now)?
> >
> > Madhavan is the author of ARM64's objtool, I think your opinion is
> > also very important.
>
> arm64 doesn't (yet) use objtool.
>
> I defer to Ard on anything relating to the arm64 efistub. Reading the
> start of this thread, it doesn't look like he's convinced and I'm not
> surprised if it's purely an issue with objtool.
OK, I know, but I have a concern.

Ard said that he is reluctant to make changes to accommodate a flawed
build time tool and there may be regression risk.

So, I'm also reluctant and don't want LoongArch to meet regression
risk. If one day LoongArch has a regression, we probably need another
workaround to "fix" this workaround. But if these three architectures
change in the same way, we may have a chance to solve some fundamental
problems...

Huacai

>
> Will