[tip: x86/build] efi/libstub: Add $(CLANG_FLAGS) to x86 flags

[tip-bot2 for Nathan Chancellor]

The following commit has been merged into the x86/build branch of tip:

Commit-ID:     58d746c119dfa28e72fc35aacaf3d2a3ac625cd0
Gitweb:        https://git.kernel.org/tip/58d746c119dfa28e72fc35aacaf3d2a3ac625cd0
Author:        Nathan Chancellor <nathan@xxxxxxxxxx>
AuthorDate:    Thu, 25 Mar 2021 17:04:35 -07:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Fri, 26 Mar 2021 11:34:58 +01:00

efi/libstub: Add $(CLANG_FLAGS) to x86 flags

When cross compiling x86 on an ARM machine with clang, there are several
errors along the lines of:

  arch/x86/include/asm/page_64.h:52:7: error: invalid output constraint '=D' in asm

This happens because the x86 flags in the EFI stub are not derived from
KBUILD_CFLAGS like the other architectures are and the clang flags that
set the target architecture ('--target=') and the path to the GNU cross
tools ('--prefix=') are not present, meaning that the host architecture
is targeted.

These flags are available as $(CLANG_FLAGS) from the main Makefile so
add them to the cflags for x86 so that cross compiling works as expected.

Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210326000435.4785-4-nathan@xxxxxxxxxx
---
 drivers/firmware/efi/libstub/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index c23466e..d053757 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -13,7 +13,8 @@ cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ \
 				   -Wno-pointer-sign \
 				   $(call cc-disable-warning, address-of-packed-member) \
 				   $(call cc-disable-warning, gnu) \
-				   -fno-asynchronous-unwind-tables
+				   -fno-asynchronous-unwind-tables \
+				   $(CLANG_FLAGS)
 
 # arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
 # disable the stackleak plugin