x86/*/Makefile: Use -fno-asynchronous-unwind-tables to suppress .eh_frame sections (003602ad) · Commits · 戴 / test

While discussing a patch to discard .eh_frame from the compressed vmlinux using the linker script, Fangrui Song pointed out [1] that these sections shouldn't exist in the first place because arch/x86/Makefile uses -fno-asynchronous-unwind-tables. It turns out this is because the Makefiles used to build the compressed kernel redefine KBUILD_CFLAGS, dropping this flag. Add the flag to the Makefile for the compressed kernel, as well as the EFI stub Makefile to fix this. Also add the flag to boot/Makefile and realmode/rm/Makefile so that the kernel's boot code (boot/setup.elf) and realmode trampoline (realmode/rm/realmode.elf) won't be compiled with .eh_frame sections, since their linker scripts also just discard them. [1] https://lore.kernel.org/lkml/20200222185806.ywnqhfqmy67akfsa@google.com/ Suggested-by:

Fangrui Song <maskray@google.com> Signed-off-by:

Arvind Sankar <nivedita@alum.mit.edu> Signed-off-by:

Borislav Petkov <bp@suse.de> Reviewed-by:

Nathan Chancellor <natechancellor@gmail.com> Reviewed-by:

Nick Desaulniers <ndesaulniers@google.com> Reviewed-by:

Kees Cook <keescook@chromium.org> Tested-by:

Nathan Chancellor <natechancellor@gmail.com> Link: https://lkml.kernel.org/r/20200224232129.597160-2-nivedita@alum.mit.edu

arch/x86/boot/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -68,6 +68,7 @@ clean-files += cpustr.h
		KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP
		KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
		KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
		KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
		GCOV_PROFILE := n
		UBSAN_SANITIZE := n

arch/x86/boot/compressed/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -39,6 +39,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
		KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
		KBUILD_CFLAGS += -Wno-pointer-sign
		KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)
		KBUILD_CFLAGS += -fno-asynchronous-unwind-tables

		KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
		GCOV_PROFILE := n

arch/x86/realmode/rm/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -71,5 +71,6 @@ $(obj)/realmode.relocs: $(obj)/realmode.elf FORCE
		KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
		-I$(srctree)/arch/x86/boot
		KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
		KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
		GCOV_PROFILE := n
		UBSAN_SANITIZE := n

drivers/firmware/efi/libstub/Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -12,7 +12,8 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ -O2 \
		-mno-mmx -mno-sse -fshort-wchar \
		-Wno-pointer-sign \
		$(call cc-disable-warning, address-of-packed-member) \
		$(call cc-disable-warning, gnu)
		$(call cc-disable-warning, gnu) \
		-fno-asynchronous-unwind-tables

		# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
		# disable the stackleak plugin

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