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References: <20201005025720.2599682-1-keescook@chromium.org>
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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 5 Oct 2020 10:36:11 -0700
Message-ID: <CAKwvOdnVJW0wDuMvgfKUE248gbDTT1CYmDY=hczaFNQ_39OfjA@mail.gmail.com>
Subject: Re: [PATCH v2] vmlinux.lds.h: Keep .ctors.* with .ctors
To:     Kees Cook <keescook@chromium.org>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Arnd Bergmann <arnd@arndb.de>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-toolchains@vger.kernel.org,
        Segher Boessenkool <segher@kernel.crashing.org>
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Precedence: bulk

On Sun, Oct 4, 2020 at 7:57 PM Kees Cook <keescook@chromium.org> wrote:
>
> Under some circumstances, the compiler generates .ctors.* sections. This
> is seen doing a cross compile of x86_64 from a powerpc64el host:
>
> x86_64-linux-gnu-ld: warning: orphan section `.ctors.65435' from `kernel/trace/trace_clock.o' being
> placed in section `.ctors.65435'
> x86_64-linux-gnu-ld: warning: orphan section `.ctors.65435' from `kernel/trace/ftrace.o' being
> placed in section `.ctors.65435'
> x86_64-linux-gnu-ld: warning: orphan section `.ctors.65435' from `kernel/trace/ring_buffer.o' being
> placed in section `.ctors.65435'
>
> Include these orphans along with the regular .ctors section.

It's very curious to see different behavior based on whether one is
targeting x86_64 via native compilation vs cross compilation.

Acked-by: Nick Desaulniers <ndesaulniers@google.com>

>
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Fixes: 83109d5d5fba ("x86/build: Warn on orphan section placement")
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v2: brown paper bag version: fix whitespace for proper backslash alignment
> ---
>  include/asm-generic/vmlinux.lds.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 5430febd34be..b83c00c63997 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -684,6 +684,7 @@
>  #ifdef CONFIG_CONSTRUCTORS
>  #define KERNEL_CTORS() . = ALIGN(8);                      \
>                         __ctors_start = .;                 \
> +                       KEEP(*(SORT(.ctors.*)))            \
>                         KEEP(*(.ctors))                    \
>                         KEEP(*(SORT(.init_array.*)))       \
>                         KEEP(*(.init_array))               \
> --
> 2.25.1
>


-- 
Thanks,
~Nick Desaulniers