From: Kees Cook <kees@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Kees Cook <kees@kernel.org>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Nathan Chancellor <nathan@kernel.org>,
Nicolas Schier <nsc@kernel.org>,
linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: [PATCH v1 3/3] efi/libstub: Disable kernel stack erasing in the common flags
Date: Tue, 6 Oct 2026 13:42:23 -0700 [thread overview]
Message-ID: <20261006204224.1536491-3-kees@kernel.org> (raw)
In-Reply-To: <20261006204210.i.137-kees@kernel.org>
Every architecture that builds the stub now adds $(DISABLE_KSTACK_ERASE)
to its own flags, so add it once to the flags they share instead.
Assisted-by: LLM
Signed-off-by: Kees Cook <kees@kernel.org>
---
drivers/firmware/efi/libstub/Makefile | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 1f588591f458..d6fe69c3af87 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -19,22 +19,18 @@ cflags-$(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
next prev parent reply other threads:[~2026-10-06 20:42 UTC|newest]
Thread overview: 7+ 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 ` Kees Cook [this message]
2026-10-07 9:21 ` [PATCH v1 3/3] efi/libstub: Disable kernel stack erasing in the common flags Nathan Chancellor
2026-10-08 14:43 ` [PATCH v1 0/3] efi/libstub: Build the x86 stub from KBUILD_CFLAGS Ard Biesheuvel
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