linux-kernel - Re: [PATCH V3] LoongArch: Add efistub booting support

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Date:   Sun, 4 Sep 2022 21:24:39 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Xi Ruoyao <xry111@...111.site>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Arnd Bergmann <arnd@...db.de>, loongarch@...ts.linux.dev,
        linux-arch <linux-arch@...r.kernel.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>, Xuerui Wang <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3] LoongArch: Add efistub booting support

Hi, Ard,

On Thu, Sep 1, 2022 at 6:40 PM Huacai Chen <chenhuacai@...nel.org> wrote:
>
> Hi, Ard,
>
> On Sat, Aug 27, 2022 at 3:14 PM Ard Biesheuvel <ardb@...nel.org> wrote:
> >
> > On Sat, 27 Aug 2022 at 06:41, Xi Ruoyao <xry111@...111.site> wrote:
> > >
> > > Tested V3 with the magic number check manually removed in my GRUB build.
> > > The system boots successfully.  I've not tested Arnd's zBoot patch yet.
> >
> > I am Ard not Arnd :-)
> >
> > Please use this branch when testing the EFI decompressor:
> > https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=efi-decompressor-v4
> The root cause of LoongArch zboot boot failure has been found, it is a
> binutils bug, latest toolchain with the below patch can solve the
> problem.
>
> diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
> index 5b44901b9e0..fafdc7c7458 100644
> --- a/bfd/elfnn-loongarch.c
> +++ b/bfd/elfnn-loongarch.c
> @@ -2341,9 +2341,10 @@ loongarch_elf_relocate_section (bfd
> *output_bfd, struct bfd_link_info *info,
>      case R_LARCH_SOP_PUSH_PLT_PCREL:
>        unresolved_reloc = false;
>
> -      if (resolved_to_const)
> +      if (!is_undefweak && resolved_to_const)
>          {
>            relocation += rel->r_addend;
> +          relocation -= pc;
>            break;
>          }
>        else if (is_undefweak)
>
>
> Huacai
Now the patch is submitted here:
https://sourceware.org/pipermail/binutils/2022-September/122713.html

And I have some other questions about kexec: kexec should jump to the
elf entry or the pe entry? I think is the elf entry, because if we
jump to the pe entry, then SVAM will be executed twice (but it should
be executed only once). However, how can we jump to the elf entry if
we use zboot? Maybe it is kexec-tool's responsibility to decompress
the zboot kernel image?

Huacai