This is a note to let you know that I've just added the patch titled x86/build: Propagate $(CLANG_FLAGS) to $(REALMODE_FLAGS) to the 5.4-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-build-propagate-clang_flags-to-realmode_flags.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 1fca5d83c5577c9890e8c81f5ee024cf96468674 Author: John Millikin <john@xxxxxxxxxxxxxxxxx> Date: Thu Mar 25 17:04:33 2021 -0700 x86/build: Propagate $(CLANG_FLAGS) to $(REALMODE_FLAGS) [ Upstream commit 8abe7fc26ad8f28bfdf78adbed56acd1fa93f82d ] When cross-compiling with Clang, the `$(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@xxxxxxxxxxxxxxxxx> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx> Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx> Link: https://lkml.kernel.org/r/20210326000435.4785-2-nathan@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> 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