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    SubjectRe: [PATCH 1/2] kbuild: remove cc-option test of -fno-stack-protector
    On Fri, Jun 26, 2020 at 01:13:20PM -0700, Nick Desaulniers wrote:
    > On Fri, Jun 26, 2020 at 12:00 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
    > >
    > > +++ b/Makefile
    > > @@ -762,7 +762,7 @@ ifneq ($(CONFIG_FRAME_WARN),0)
    > > KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
    > > endif
    > >
    > > -stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
    > > +stackp-flags-y := -fno-stack-protector
    > > stackp-flags-$(CONFIG_STACKPROTECTOR) := -fstack-protector
    > > stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong
    >
    > So it looks like the previous behavior always added
    > `-fno-stack-protector` (since CONFIG_CC_HAS_STACKPROTECTOR_NONE was
    > always true), but then we append either `-fstack-protector` or
    > `-fstack-protector-strong` based on configs. While that's ok, and you
    > patch doesn't change that behavior, and it's good to be explicit to
    > set the stack protector or not...it seems weird to have
    > `-fno-stack-protector -fstack-protector` in the command line flags. I
    > would prefer if we checked for not having CONFIG_STACKPROTECTOR or
    > CONFIG_STACKPROTECTOR_STRONG before adding `-fno-stack-protector`.
    > That doesn't have to be done in this patch, per se.

    No, it would add only what was latest and most selected. (They're all
    ":=" assignments.) If CONFIG_STACKPROTECTOR_STRONG, only
    -fstack-protector-strong is set. If only CONFIG_STACKPROTECTOR, only
    -fstack-protector is set. Otherwise -fno-stack-protector.

    --
    Kees Cook

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