linux-kernel - Re: [PATCH] LoongArch: Record pc instead of offset in la-abs relocation

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Message-ID: <CAAhV-H7tUKiJVR=9YxwnaSk3Ru1k=4Nd-TUgaMDBCq+xGnLkrA@mail.gmail.com>
Date:   Tue, 21 Nov 2023 09:32:37 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     WANG Rui <wangrui@...ngson.cn>, WANG Xuerui <kernel@...0n.name>,
        Jinyang He <hejinyang@...ngson.cn>,
        Xi Ruoyao <xry111@...111.site>, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-kbuild@...r.kernel.org,
        llvm@...ts.linux.dev, loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH] LoongArch: Record pc instead of offset in la-abs relocation

Applied to loongarch-fixes, thanks.

Huacai

On Tue, Nov 21, 2023 at 7:08 AM Nathan Chancellor <nathan@...nel.org> 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 use
> > of clang to compile relocatable kernels.
> >
> > Signed-off-by: WANG Rui <wangrui@...ngson.cn>
>
> Thanks a lot for the patch! This fixes the CONFIG_RELOCATABLE build for
> me as well.
>
> Tested-by: Nathan Chancellor <nathan@...nel.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/include/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/include/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, void *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/relocate.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 random_offset)
> >       for (p = begin; (void *)p < end; p++) {
> >               long v = p->symvalue;
> >               uint32_t lu12iw, ori, lu32id, lu52id;
> > -             union loongarch_instruction *insn = (void *)p - p->offset;
> > +             union loongarch_instruction *insn = (void *)p->pc;
> >
> >               lu12iw = (v >> 12) & 0xfffff;
> >               ori    = v & 0xfff;
> > --
> > 2.42.1
> >
> >