From: Nathan Chancellor <nathan@kernel.org>
To: Kees Cook <kees@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Nicolas Schier <nsc@kernel.org>,
linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH v1 3/3] efi/libstub: Disable kernel stack erasing in the common flags
Date: Wed, 7 Oct 2026 11:21:04 +0200 [thread overview]
Message-ID: <20261007092104.GC1504630@ax162> (raw)
In-Reply-To: <20261006204224.1536491-3-kees@kernel.org>
On Tue, Oct 06, 2026 at 01:42:23PM -0700, Kees Cook wrote:
> Every architecture that builds the stub now adds $(DISABLE_KSTACK_ERASE)
> to its own flags, so add it once to the flags they share instead.
>
> Assisted-by: LLM
> Signed-off-by: Kees Cook <kees@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> ---
> drivers/firmware/efi/libstub/Makefile | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 1f588591f458..d6fe69c3af87 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -19,22 +19,18 @@ cflags-$(CONFIG_X86) := $(filter-out -mcmodel=kernel \
> $(PADDING_CFLAGS), $(cflags-y))
> cflags-$(CONFIG_X86_32) += -march=i386
> cflags-$(CONFIG_X86_64) += -mcmodel=small
> -cflags-$(CONFIG_X86) += -fPIC $(DISABLE_KSTACK_ERASE)
> +cflags-$(CONFIG_X86) += -fPIC
> # Nothing enables IBT while the stub runs, so ENDBR would only take space.
> cflags-$(CONFIG_X86) += $(call cc-option,-fcf-protection=none)
>
> -# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
> -# disable the stackleak plugin
> -cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_KSTACK_ERASE) \
> - -fno-unwind-tables -fno-asynchronous-unwind-tables
> +cflags-$(CONFIG_ARM64) += -fpie -fno-unwind-tables \
> + -fno-asynchronous-unwind-tables
> cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \
> -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \
> -DEFI_HAVE_STRCMP -fno-builtin -fpic \
> - $(call cc-option,-mno-single-pic-base) \
> - $(DISABLE_KSTACK_ERASE)
> -cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax \
> - $(DISABLE_KSTACK_ERASE)
> -cflags-$(CONFIG_LOONGARCH) += -fpie $(DISABLE_KSTACK_ERASE)
> + $(call cc-option,-mno-single-pic-base)
> +cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax
> +cflags-$(CONFIG_LOONGARCH) += -fpie
>
> cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
>
> @@ -44,6 +40,7 @@ KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \
> -D__NO_FORTIFY \
> -ffreestanding \
> -fno-stack-protector \
> + $(DISABLE_KSTACK_ERASE) \
> $(call cc-option,-fno-addrsig) \
> -D__DISABLE_EXPORTS
>
> --
> 2.55.0
>
--
Cheers,
Nathan
prev parent reply other threads:[~2026-10-07 9:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-06 20:42 [PATCH v1 0/3] efi/libstub: Build the x86 stub from KBUILD_CFLAGS Kees Cook
2026-10-06 20:42 ` [PATCH v1 1/3] efi/libstub: Declare the x86 stub's assembly entry points Kees Cook
2026-10-06 20:42 ` [PATCH v1 2/3] efi/libstub: Build the x86 stub from KBUILD_CFLAGS Kees Cook
2026-10-07 9:20 ` Nathan Chancellor
2026-10-06 20:42 ` [PATCH v1 3/3] efi/libstub: Disable kernel stack erasing in the common flags Kees Cook
2026-10-07 9:21 ` Nathan Chancellor [this message]
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