linux-kernel - Re: arch/x86/entry/entry: RFC on recent kernels building error with llvm 11.0.2 internal assembler

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Date:   Sat, 7 May 2022 14:19:00 +0200
From:   Mauro Rossi <issor.oruam@...il.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     luto@...nel.org, Chih-Wei Huang <cwhuang@...roid-x86.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <llvm@...ts.linux.dev>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: arch/x86/entry/entry: RFC on recent kernels building error with
 llvm 11.0.2 internal assembler

> > Alternatively, you could apply the hack that Nick inserted into Android
> > for this issue if upgrading your toolchain or turning off the integrated
> > assembler is not possible:
> >
> > https://android.googlesource.com/kernel/common/+/e58f084735b8abf744d61083b92172ee23d45aae
> >
> > I really do not mean to sound dismissive or rude, I apologize if it
> > comes off that way, but we have worked quite hard to avoid inserting
> > unnecessary workarounds, as they are ultimately technical debt that can
> > be hard to manage over the long term.
> >
> > Cheers,
> > Nathan
>
> Thanks a lot Nathan
>
> It is definitely the clang version 11.0.x which is not updated in aosp
> Android 11 production tags
>
> I will use Nick's workaround which works since only lsl %rax, %rax is
> currently happening
>
> Many thanks, problem solved

Hello,
I'm back again because I was assuming that Nick's workaround was working ok,
but I have found that ARCH=x86_64 i.e. 64bit built kernel is causing
an immediate hard reboot at initrd execution,
just after hitting [ENTER] at grub/efi menu.

ARCh=x86 i.e. 32bit kernel binary is not affected, but is Nick's
workaround targeting 32 bit kernel builds?
Should it be modified to work for 64bit kernel binary?

How do aosp android-mailine kernels avoid this instantaneous hard reboot issue?
Mauro