Messages in this thread | | | From | Nick Desaulniers <> | Date | Mon, 24 Feb 2020 15:30:27 -0800 | Subject | Re: [PATCH v2 1/2] arch/x86: Use -fno-asynchronous-unwind-tables to suppress .eh_frame sections |
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On Mon, Feb 24, 2020 at 3:21 PM Arvind Sankar <nivedita@alum.mit.edu> wrote: > > 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 it. > > Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> > Suggested-By: Fangrui Song <maskray@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> [1] https://lore.kernel.org/lkml/20200222185806.ywnqhfqmy67akfsa@google.com/ > --- > arch/x86/boot/Makefile | 1 + > arch/x86/boot/compressed/Makefile | 1 + > arch/x86/realmode/rm/Makefile | 1 + > drivers/firmware/efi/libstub/Makefile | 3 ++- > 4 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile > index 012b82fc8617..24f011e0adf1 100644 > --- a/arch/x86/boot/Makefile > +++ b/arch/x86/boot/Makefile > @@ -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 > > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile > index 26050ae0b27e..c33111341325 100644 > --- a/arch/x86/boot/compressed/Makefile > +++ b/arch/x86/boot/compressed/Makefile > @@ -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 > diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile > index 99b6332ba540..b11ec5d8f8ac 100644 > --- a/arch/x86/realmode/rm/Makefile > +++ b/arch/x86/realmode/rm/Makefile > @@ -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 := $(KBUILD_CFLAGS) -D__ASSEMBLY__ > +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > GCOV_PROFILE := n > UBSAN_SANITIZE := n > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile > index 98a81576213d..a1140c4ee478 100644 > --- a/drivers/firmware/efi/libstub/Makefile > +++ b/drivers/firmware/efi/libstub/Makefile > @@ -12,7 +12,8 @@ cflags-$(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 > -- > 2.24.1 >
-- Thanks, ~Nick Desaulniers
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