[PATCH v7 4/5] x86/build: Warn on orphan section placement

[Arvind Sankar]

On Tue, Sep 01, 2020 at 07:53:46PM -0700, Kees Cook wrote:
> We don't want to depend on the linker's orphan section placement
> heuristics as these can vary between linkers, and may change between
> versions. All sections need to be explicitly handled in the linker script.
> 
> Now that all sections are explicitly handled, enable orphan section
> warnings.
> 
> Signed-off-by: Kees Cook <keescook at chromium.org>
> ---
>  arch/x86/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 4346ffb2e39f..154259f18b8b 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -209,6 +209,10 @@ ifdef CONFIG_X86_64
>  LDFLAGS_vmlinux += -z max-page-size=0x200000
>  endif
>  
> +# We never want expected sections to be placed heuristically by the
> +# linker. All sections should be explicitly named in the linker script.
> +LDFLAGS_vmlinux += $(call ld-option, --orphan-handling=warn)
> +
>  archscripts: scripts_basic
>  	$(Q)$(MAKE) $(build)=arch/x86/tools relocs
>  
> -- 
> 2.25.1
> 

With LLVM=1 and GCOV_KERNEL/GCOV_PROFILE_ALL enabled, there are
.eh_frame sections created. I see that KASAN and KCSAN currently discard
them. Does GCOV actually need them or should it also discard?

Thanks.