linux-kernel - Re: [PATCH 1/9] scripts/link-vmlinux.sh: Delay orphan handling warnings until final link

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Date:   Fri, 20 Mar 2020 12:47:54 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Borislav Petkov <bp@...e.de>, Kees Cook <keescook@...omium.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        clang-built-linux@...glegroups.com,
        "H.J. Lu" <hjl.tools@...il.com>, James Morse <james.morse@....com>,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Russell King <linux@...linux.org.uk>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Will Deacon <will@...nel.org>, x86@...nel.org
Subject: Re: [PATCH 1/9] scripts/link-vmlinux.sh: Delay orphan handling
 warnings until final link

Kees Cook's on February 28, 2020 10:22 am:
> Right now, powerpc adds "--orphan-handling=warn" to LD_FLAGS_vmlinux
> to detect when there are unexpected sections getting added to the kernel
> image. There is no need to report these warnings more than once, so it
> can be removed until the final link stage.
> 
> This helps pave the way for other architectures to enable this, with the
> end goal of enabling this warning by default for vmlinux for all
> architectures.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  scripts/link-vmlinux.sh | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index 1919c311c149..416968fea685 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -255,6 +255,11 @@ info GEN modules.builtin
>  tr '\0' '\n' < modules.builtin.modinfo | sed -n 's/^[[:alnum:]:_]*\.file=//p' |
>  	tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$/.ko/' > modules.builtin
>  
> +
> +# Do not warn about orphan sections until the final link stage.
> +saved_LDFLAGS_vmlinux="${LDFLAGS_vmlinux}"
> +LDFLAGS_vmlinux="$(echo "${LDFLAGS_vmlinux}" | sed -E 's/ --orphan-handling=warn( |$)/ /g')"
> +
>  btf_vmlinux_bin_o=""
>  if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
>  	if gen_btf .tmp_vmlinux.btf .btf.vmlinux.bin.o ; then
> @@ -306,6 +311,7 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then
>  	fi
>  fi
>  
> +LDFLAGS_vmlinux="${saved_LDFLAGS_vmlinux}"
>  vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
>  
>  if [ -n "${CONFIG_BUILDTIME_TABLE_SORT}" ]; then

That's ugly. Why not just enable it for all archs?

Thanks,
Nick