From: Arvind Sankar <nivedita@alum.mit.edu>
Date: Mon, 24 Feb 2020 18:21:28 -0500
Subject: x86/*/Makefile: Use -fno-asynchronous-unwind-tables to suppress
.eh_frame sections
Patch-mainline: v5.7-rc1
Git-commit: 003602ad5516e59940de42e44c8d8033387bb363
References: jsc#SLE-16407
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
Acked-by: Lee, Chun-Yi <jlee@suse.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(-)
--- 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
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -39,6 +39,7 @@ KBUILD_CFLAGS += $(call cc-disable-warni
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
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -71,5 +71,6 @@ $(obj)/realmode.relocs: $(obj)/realmode.
KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
-I$(srctree)/arch/x86/boot
KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
GCOV_PROFILE := n
UBSAN_SANITIZE := n
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -12,7 +12,8 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__K
-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