Subject: Re: [PATCH v10 12/12] efi/libstub: disable SCS

From: Kees Cook <[email-masked]>
Date: Mon, 6 Apr 2020 11:25:37 -0700

On Mon, Apr 06, 2020 at 09:41:21AM -0700, Sami Tolvanen wrote:
> Shadow stacks are not available in the EFI stub, filter out SCS flags.
> 
> Suggested-by: James Morse <[email-masked]>
> Signed-off-by: Sami Tolvanen <[email-masked]>

Reviewed-by: Kees Cook <[email-masked]>

> ---
>  drivers/firmware/efi/libstub/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 094eabdecfe6..fa0bb64f93d6 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -32,6 +32,9 @@ KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
>  				   $(call cc-option,-fno-stack-protector) \
>  				   -D__DISABLE_EXPORTS
>  
> +#  remove SCS flags from all objects in this directory

nit: double space

-Kees

> +KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
> +
>  GCOV_PROFILE			:= n
>  KASAN_SANITIZE			:= n
>  UBSAN_SANITIZE			:= n
> -- 
> 2.26.0.292.g33ef6b2f38-goog
> 

-- 
Kees Cook

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