[tip: x86/build] x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS

[tip-bot2 for Nathan Chancellor]

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

Commit-ID:     d5cbd80e302dfea59726c44c56ab7957f822409f
Gitweb:        https://git.kernel.org/tip/d5cbd80e302dfea59726c44c56ab7957f822409f
Author:        Nathan Chancellor <nathan@xxxxxxxxxx>
AuthorDate:    Thu, 25 Mar 2021 17:04:34 -07:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Fri, 26 Mar 2021 11:32:55 +01:00

x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS

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
---
 arch/x86/boot/compressed/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index e0bc398..6e5522a 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