From: John Millikin john@john-millikin.com
[ Upstream commit 8abe7fc26ad8f28bfdf78adbed56acd1fa93f82d ]
When cross-compiling with Clang, the `$(CLANG_FLAGS)' variable contains additional flags needed to build C and assembly sources for the target platform. Normally this variable is automatically included in `$(KBUILD_CFLAGS)' via the top-level Makefile.
The x86 real-mode makefile builds `$(REALMODE_CFLAGS)' from a plain assignment and therefore drops the Clang flags. This causes Clang to not recognize x86-specific assembler directives:
arch/x86/realmode/rm/header.S:36:1: error: unknown directive .type real_mode_header STT_OBJECT ; .size real_mode_header, .-real_mode_header ^
Explicit propagation of `$(CLANG_FLAGS)' to `$(REALMODE_CFLAGS)', which is inherited by real-mode make rules, fixes cross-compilation with Clang for x86 targets.
Relevant flags:
* `--target' sets the target architecture when cross-compiling. This flag must be set for both compilation and assembly (`KBUILD_AFLAGS') to support architecture-specific assembler directives.
* `-no-integrated-as' tells clang to assemble with GNU Assembler instead of its built-in LLVM assembler. This flag is set by default unless `LLVM_IAS=1' is set, because the LLVM assembler can't yet parse certain GNU extensions.
Signed-off-by: John Millikin john@john-millikin.com Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Borislav Petkov bp@suse.de Acked-by: Ard Biesheuvel ardb@kernel.org Tested-by: Sedat Dilek sedat.dilek@gmail.com Link: https://lkml.kernel.org/r/20210326000435.4785-2-nathan@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/Makefile | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 59942e349e5f..69f0cb01c666 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -40,6 +40,7 @@ REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -ffreestanding REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -fno-stack-protector) REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -Wno-address-of-packed-member) REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align4)) +REALMODE_CFLAGS += $(CLANG_FLAGS) export REALMODE_CFLAGS
# BITS is used as extension for files which are available in a 32 bit