This is a note to let you know that I've just added the patch titled x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-boot-add-clang_flags-to-compressed-kbuild_cflags.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a25428e5208a3e67d934b259abd1ff80bce50569 Author: Nathan Chancellor <nathan@xxxxxxxxxx> Date: Thu Mar 25 17:04:34 2021 -0700 x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS [ Upstream commit d5cbd80e302dfea59726c44c56ab7957f822409f ] When cross compiling x86 on an ARM machine with clang, there are several errors along the lines of: arch/x86/include/asm/string_64.h:27:10: error: invalid output constraint '=&c' in asm This happens because the compressed boot Makefile reassigns KBUILD_CFLAGS and drops the clang flags that set the target architecture ('--target=') and the path to the GNU cross tools ('--prefix='), meaning that the host architecture is targeted. These flags are available as $(CLANG_FLAGS) from the main Makefile so add them to the compressed boot folder's KBUILD_CFLAGS 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/20210326000435.4785-3-nathan@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 40b8fd375d52..6004047d25fd 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -46,6 +46,7 @@ KBUILD_CFLAGS += -D__DISABLE_EXPORTS # Disable relocation relaxation in case the link is not PIE. KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no) KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h +KBUILD_CFLAGS += $(CLANG_FLAGS) # sev-es.c indirectly inludes inat-table.h which is generated during # compilation and stored in $(objtree). Add the directory to the includes so