The following commit has been merged into the core/build branch of tip: Commit-ID: e2179a09ab089d3423751bd2b0c884ddb3eabe84 Gitweb: https://git.kernel.org/tip/e2179a09ab089d3423751bd2b0c884ddb3eabe84 Author: Kees Cook <keesc...@chromium.org> AuthorDate: Fri, 21 Aug 2020 12:42:48 -07:00 Committer: Ingo Molnar <mi...@kernel.org> CommitterDate: Tue, 01 Sep 2020 09:50:36 +02:00
efi/libstub: Disable -mbranch-protection In preparation for adding --orphan-handling=warn to more architectures, disable -mbranch-protection, as EFI does not yet support it[1]. This was noticed due to it producing unwanted .note.gnu.property sections (prefixed with .init due to the objcopy build step). However, we must also work around a bug in Clang where the section is still emitted for code-less object files[2], so also remove the section during the objcopy. [1] https://lore.kernel.org/lkml/CAMj1kXHck12juGi=E=p4hwp_8vqhq+-x3vbmc3tgerwdq-x...@mail.gmail.com [2] https://bugs.llvm.org/show_bug.cgi?id=46480 Signed-off-by: Kees Cook <keesc...@chromium.org> Signed-off-by: Ingo Molnar <mi...@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulni...@google.com> Acked-by: Ard Biesheuvel <a...@kernel.org> Link: https://lore.kernel.org/r/20200821194310.3089815-8-keesc...@chromium.org --- drivers/firmware/efi/libstub/Makefile | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 5eefd60..0c911e3 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -18,7 +18,8 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \ # arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly # disable the stackleak plugin cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ - -fpie $(DISABLE_STACKLEAK_PLUGIN) + -fpie $(DISABLE_STACKLEAK_PLUGIN) \ + $(call cc-option,-mbranch-protection=none) cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ -fno-builtin -fpic \ $(call cc-option,-mno-single-pic-base) @@ -66,6 +67,12 @@ lib-$(CONFIG_X86) += x86-stub.o CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) +# Even when -mbranch-protection=none is set, Clang will generate a +# .note.gnu.property for code-less object files (like lib/ctype.c), +# so work around this by explicitly removing the unwanted section. +# https://bugs.llvm.org/show_bug.cgi?id=46480 +STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property + # # For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the # .bss section, so the .bss section of the EFI stub needs to be included in the
