[PATCH 4.9 35/49] x86/build: Disable CET instrumentation in the kernel for 32-bit too

Greg Kroah-Hartman
2021-02-22T13:51:11Z

From: Borislav Petkov <bp@suse.de>

commit 256b92af784d5043eeb7d559b6d5963dcc2ecb10 upstream.

Commit

20bf2b378729 ("x86/build: Disable CET instrumentation in the kernel")

disabled CET instrumentation which gets added by default by the Ubuntu
gcc9 and 10 by default, but did that only for 64-bit builds. It would
still fail when building a 32-bit target. So disable CET for all x86
builds.

Fixes: 20bf2b378729 ("x86/build: Disable CET instrumentation in the kernel")
Reported-by: AC <achirvasub@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: AC <achirvasub@gmail.com>
Link: https://lkml.kernel.org/r/YCCIgMHkzh/xT4ex@arch-chirva.localdomain
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/Makefile | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -61,6 +61,9 @@ endif
KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
KBUILD_CFLAGS += $(call cc-option,-mno-avx,)

+# Intel CET isn't enabled in the kernel
+KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
+
ifeq ($(CONFIG_X86_32),y)
BITS := 32
UTS_MACHINE := i386
@@ -137,9 +140,6 @@ else
KBUILD_CFLAGS += -mno-red-zone
KBUILD_CFLAGS += -mcmodel=kernel

- # Intel CET isn't enabled in the kernel
- KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
-
# -funit-at-a-time shrinks the kernel .text considerably
# unfortunately it makes reading oopses harder.
KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)