Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35;
MIME-Version: 1.0
References: <20231116130331.241395-1-wangrui@loongson.cn> <20231120230817.GA2116806@dev-arch.thelio-3990X>
In-Reply-To: <20231120230817.GA2116806@dev-arch.thelio-3990X>
From:   Huacai Chen <chenhuacai@kernel.org>
Date:   Tue, 21 Nov 2023 09:32:37 +0800
Message-ID: <CAAhV-H7tUKiJVR=9YxwnaSk3Ru1k=4Nd-TUgaMDBCq+xGnLkrA@mail.gmail.com>
Subject: Re: [PATCH] LoongArch: Record pc instead of offset in la-abs relocation
To:     Nathan Chancellor <nathan@kernel.org>
Cc:     WANG Rui <wangrui@loongson.cn>, WANG Xuerui <kernel@xen0n.name>,
        Jinyang He <hejinyang@loongson.cn>,
        Xi Ruoyao <xry111@xry111.site>, linux-kernel@vger.kernel.org,
        loongarch@lists.linux.dev, linux-kbuild@vger.kernel.org,
        llvm@lists.linux.dev, loongson-kernel@lists.loongnix.cn
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Applied to loongarch-fixes, thanks.

Huacai

On Tue, Nov 21, 2023 at 7:08=E2=80=AFAM Nathan Chancellor <nathan@kernel.or=
g> wrote:
>
> Hi Rui,
>
> On Thu, Nov 16, 2023 at 09:03:31PM +0800, WANG Rui wrote:
> > To clarify, the previous version functioned flawlessly. However, it's
> > worth noting that the LLVM's LoongArch backend currently lacks support
> > for cross-section label calculations. With this patch, we enable the us=
e
> > of clang to compile relocatable kernels.
> >
> > Signed-off-by: WANG Rui <wangrui@loongson.cn>
>
> Thanks a lot for the patch! This fixes the CONFIG_RELOCATABLE build for
> me as well.
>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
>
> Something I noticed while testing is that a kernel linked with ld.lld
> does not boot while one linked with ld.bfd did. I think this might be
> the same issue that Xuerui filed on our issue tracker but I figured I
> would mention it in case not:
> https://github.com/ClangBuiltLinux/linux/issues/1883
>
> Cheers,
> Nathan
>
> > ---
> >  arch/loongarch/include/asm/asmmacro.h | 3 +--
> >  arch/loongarch/include/asm/setup.h    | 2 +-
> >  arch/loongarch/kernel/relocate.c      | 2 +-
> >  3 files changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/loongarch/include/asm/asmmacro.h b/arch/loongarch/inc=
lude/asm/asmmacro.h
> > index c9544f358c33..655db7d7a427 100644
> > --- a/arch/loongarch/include/asm/asmmacro.h
> > +++ b/arch/loongarch/include/asm/asmmacro.h
> > @@ -609,8 +609,7 @@
> >       lu32i.d \reg, 0
> >       lu52i.d \reg, \reg, 0
> >       .pushsection ".la_abs", "aw", %progbits
> > -     768:
> > -     .dword  768b-766b
> > +     .dword  766b
> >       .dword  \sym
> >       .popsection
> >  #endif
> > diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/includ=
e/asm/setup.h
> > index a0bc159ce8bd..ee52fb1e9963 100644
> > --- a/arch/loongarch/include/asm/setup.h
> > +++ b/arch/loongarch/include/asm/setup.h
> > @@ -25,7 +25,7 @@ extern void set_merr_handler(unsigned long offset, vo=
id *addr, unsigned long len
> >  #ifdef CONFIG_RELOCATABLE
> >
> >  struct rela_la_abs {
> > -     long offset;
> > +     long pc;
> >       long symvalue;
> >  };
> >
> > diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/r=
elocate.c
> > index 6c3eff9af9fb..288b739ca88d 100644
> > --- a/arch/loongarch/kernel/relocate.c
> > +++ b/arch/loongarch/kernel/relocate.c
> > @@ -52,7 +52,7 @@ static inline void __init relocate_absolute(long rand=
om_offset)
> >       for (p =3D begin; (void *)p < end; p++) {
> >               long v =3D p->symvalue;
> >               uint32_t lu12iw, ori, lu32id, lu52id;
> > -             union loongarch_instruction *insn =3D (void *)p - p->offs=
et;
> > +             union loongarch_instruction *insn =3D (void *)p->pc;
> >
> >               lu12iw =3D (v >> 12) & 0xfffff;
> >               ori    =3D v & 0xfff;
> > --
> > 2.42.1
> >
> >