Re: [PATCH 21/30] stack-protector: test compiler capability in Kconfig and drop AUTO mode

[Kees Cook]

On Thu, Apr 12, 2018 at 10:06 PM, Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> wrote:
> +stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
> +stackp-flags-$(CONFIG_CC_STACKPROTECTOR)          := -fstack-protector
> +stackp-flags-$(CONFIG_CC_STACKPROTECTOR_STRONG)   := -fstack-protector-strong
> +
> +KBUILD_CFLAGS += $(stackp-flags-y)

So, technically, this works just fine. I wonder if it has an overly
confusing result, in that the compiler under normal situations will
see:

gcc ... -fno-stack-protector -fstack-protector -fstack-protector-strong ...

How about something like this instead:

ifdef CONFIG_CC_STACKPROTECTOR_STRONG
KBUILD_CFLAGS += -fstack-protector-strong
else
ifdef CONFIG_CC_STACKPROTECTOR
KBUILD_CFLAGS += -fstack-protector
else
KBUILD_CFLAGS += -fno-stack-protector
endif
endif

-Kees

-- 
Kees Cook
Pixel Security