[tip: x86/boot] x86/*/Makefile: Use -fno-asynchronous-unwind-tables to suppress .eh_frame sections
From: tip-bot2 for Arvind Sankar
Date: Tue Feb 25 2020 - 11:53:30 EST
The following commit has been merged into the x86/boot branch of tip:
Commit-ID: 003602ad5516e59940de42e44c8d8033387bb363
Gitweb: https://git.kernel.org/tip/003602ad5516e59940de42e44c8d8033387bb363
Author: Arvind Sankar <nivedita@xxxxxxxxxxxx>
AuthorDate: Mon, 24 Feb 2020 18:21:28 -05:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Tue, 25 Feb 2020 13:18:29 +01:00
x86/*/Makefile: Use -fno-asynchronous-unwind-tables to suppress .eh_frame sections
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@xxxxxxxxxx/
Suggested-by: Fangrui Song <maskray@xxxxxxxxxx>
Signed-off-by: Arvind Sankar <nivedita@xxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Tested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20200224232129.597160-2-nivedita@xxxxxxxxxxxx
---
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 012b82f..24f011e 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 26050ae..c331113 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 99b6332..b11ec5d 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 := $(KBUILD_CFLAGS) -D__ASSEMBLY__
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
GCOV_PROFILE := n
UBSAN_SANITIZE := n
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 98a8157..a1140c4 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -12,7 +12,8 @@ cflags-$(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