linux-kernel - Re: [PATCH] MIPS: fw: arc: add __weak to prom_meminit and prom_free_prom

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Message-ID: <CAKwvOdmEcC7SszqpEYeT3v_gi89vAyDyofZaKkfF_YhEXu=E5A@mail.gmail.com>
Date:   Mon, 6 Apr 2020 11:16:57 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux-MIPS <linux-mips@...ux-mips.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Paul Burton <paulburton@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org
Subject: Re: [PATCH] MIPS: fw: arc: add __weak to prom_meminit and prom_free_prom_memory

On Sun, Apr 5, 2020 at 9:31 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> As far as I understood, prom_meminit() in arch/mips/fw/arc/memory.c
> is overridden by the one in arch/mips/sgi-ip32/ip32-memory.c if
> CONFIG_SGI_IP32 is enabled.

I'm curious if this issue is affected by other combinations of files
that each define prom_meminit with external linkage and symbol
visibility.  I would expect __weak to be used when there's a base
implementation that we expect to be overridden, but I don't think
that's what's happening in this case.  It's not clear to me which
definition would be the default, let alone the one in
arch/mips/fw/arc/memory.c.

Looks like CONFIG_SGI_IP32 selects CONFIG_FW_ARC, so it's not clear
why arch/mips/sgi-ip32/ip32-memory.c and arch/mips/fw/arc/memory.c
define different implementations of prom_meminit, and which one was
expected to be used.

Hopefully the maintainers can clarify.

>
> The use of EXPORT_SYMBOL in static libraries potentially causes a
> problem for the llvm linker [1]. So, I want to forcibly link lib-y
> objects to vmlinux when CONFIG_MODULES=y.
>
> As a groundwork, we must fix multiple definitions that have previously
> been hidden by lib-y.
>
> The prom_cleanup() in this file is already marked as __weak (because
> it is overridden by the one in arch/mips/sgi-ip22/ip22-mc.c).
> I think it should be OK to do the same for these two.
>
> [1]: https://github.com/ClangBuiltLinux/linux/issues/515
>
> Reported-by: kbuild test robot <lkp@...el.com>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
> If MIPS maintainers ack this patch,
> I want to inser it before the following patch:
>
> https://patchwork.kernel.org/patch/11432969/
>
>  arch/mips/fw/arc/memory.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/fw/arc/memory.c b/arch/mips/fw/arc/memory.c
> index dbbcddc82823..89fa6e62a3b3 100644
> --- a/arch/mips/fw/arc/memory.c
> +++ b/arch/mips/fw/arc/memory.c
> @@ -117,7 +117,7 @@ static int __init prom_memtype_classify(union linux_memtypes type)
>         return memtype_classify_arc(type);
>  }
>
> -void __init prom_meminit(void)
> +void __weak __init prom_meminit(void)
>  {
>         struct linux_mdesc *p;
>
> @@ -162,7 +162,7 @@ void __weak __init prom_cleanup(void)
>  {
>  }
>
> -void __init prom_free_prom_memory(void)
> +void __weak __init prom_free_prom_memory(void)
>  {
>         int i;
>
> --

-- 
Thanks,
~Nick Desaulniers