linux-kernel - Re: [PATCH] ppc: add "-z notext" flag to disable diagnostic

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Message-ID: <CAKwvOdm8R1zh-NPCRZX=_BZhUEey5v=0jjz=ca82tzMn2kFqYg@mail.gmail.com>
Date:   Thu, 12 Aug 2021 13:53:32 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Bill Wendling <morbo@...gle.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Nathan Chancellor <nathan@...nel.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com, itaru.kitayama@...en.jp
Subject: Re: [PATCH] ppc: add "-z notext" flag to disable diagnostic

On Thu, Aug 12, 2021 at 1:49 PM Bill Wendling <morbo@...gle.com> wrote:
>
> The "-z notext" flag disables reporting an error if DT_TEXTREL is set on
> PPC with CONFIG=kdump:
>
>   ld.lld: error: can't create dynamic relocation R_PPC64_ADDR64 against
>     local symbol in readonly segment; recompile object files with -fPIC
>     or pass '-Wl,-z,notext' to allow text relocations in the output
>   >>> defined in built-in.a(arch/powerpc/kernel/misc.o)
>   >>> referenced by arch/powerpc/kernel/misc.o:(.text+0x20) in archive
>       built-in.a
>
> The BFD linker disables this by default (though it's configurable in
> current versions). LLD enables this by default. So we add the flag to
> keep LLD from emitting the error.
>
> Signed-off-by: Bill Wendling <morbo@...gle.com>

Link: https://github.com/ClangBuiltLinux/linux/issues/811
Reported-by: Itaru Kitayama <itaru.kitayama@...en.jp>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> ---
> The output of the "get_maintainer.pl" run just in case no one believes me. :-)

LOL!

>
> $ ./scripts/get_maintainer.pl arch/powerpc/Makefile
> Michael Ellerman <mpe@...erman.id.au> (supporter:LINUX FOR POWERPC (32-BIT AND 64-BIT))
> Benjamin Herrenschmidt <benh@...nel.crashing.org> (reviewer:LINUX FOR POWERPC (32-BIT AND 64-BIT))
> Paul Mackerras <paulus@...ba.org> (reviewer:LINUX FOR POWERPC (32-BIT AND 64-BIT))
> Nathan Chancellor <nathan@...nel.org> (supporter:CLANG/LLVM BUILD SUPPORT)
> Nick Desaulniers <ndesaulniers@...gle.com> (supporter:CLANG/LLVM BUILD SUPPORT)
> linuxppc-dev@...ts.ozlabs.org (open list:LINUX FOR POWERPC (32-BIT AND 64-BIT))
> linux-kernel@...r.kernel.org (open list)
> clang-built-linux@...glegroups.com (open list:CLANG/LLVM BUILD SUPPORT)
> ---
>  arch/powerpc/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index 6505d66f1193..17a9fbf9b789 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -122,6 +122,7 @@ endif
>
>  LDFLAGS_vmlinux-y := -Bstatic
>  LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
> +LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) += -z notext
>  LDFLAGS_vmlinux        := $(LDFLAGS_vmlinux-y)
>
>  ifdef CONFIG_PPC64
> --
> 2.33.0.rc1.237.g0d66db33f3-goog
>


-- 
Thanks,
~Nick Desaulniers