Patch "kbuild: add $(CLANG_FLAGS) to KBUILD_CPPFLAGS" has been added to the 5.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    kbuild: add $(CLANG_FLAGS) to KBUILD_CPPFLAGS

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:
     kbuild-add-clang_flags-to-kbuild_cppflags.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@vger.kernel.org> know about it.


From stable+bounces-167086-greg=kroah.com@vger.kernel.org Tue Aug 12 01:53:32 2025
From: Nathan Chancellor <nathan@kernel.org>
Date: Mon, 11 Aug 2025 16:51:50 -0700
Subject: kbuild: add $(CLANG_FLAGS) to KBUILD_CPPFLAGS
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Sasha Levin <sashal@kernel.org>
Cc: stable@vger.kernel.org, llvm@lists.linux.dev
Message-ID: <20250811235151.1108688-6-nathan@kernel.org>

From: Masahiro Yamada <masahiroy@kernel.org>

commit feb843a469fb0ab00d2d23cfb9bcc379791011bb upstream.

When preprocessing arch/*/kernel/vmlinux.lds.S, the target triple is
not passed to $(CPP) because we add it only to KBUILD_{C,A}FLAGS.

As a result, the linker script is preprocessed with predefined macros
for the build host instead of the target.

Assuming you use an x86 build machine, compare the following:

 $ clang -dM -E -x c /dev/null
 $ clang -dM -E -x c /dev/null -target aarch64-linux-gnu

There is no actual problem presumably because our linker scripts do not
rely on such predefined macros, but it is better to define correct ones.

Move $(CLANG_FLAGS) to KBUILD_CPPFLAGS, so that all *.c, *.S, *.lds.S
will be processed with the proper target triple.

[Note]
After the patch submission, we got an actual problem that needs this
commit. (CBL issue 1859)

Link: https://github.com/ClangBuiltLinux/linux/issues/1859
Reported-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 Makefile |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/Makefile
+++ b/Makefile
@@ -568,8 +568,7 @@ ifneq ($(LLVM_IAS),1)
 CLANG_FLAGS	+= -no-integrated-as
 endif
 CLANG_FLAGS	+= -Werror=unknown-warning-option
-KBUILD_CFLAGS	+= $(CLANG_FLAGS)
-KBUILD_AFLAGS	+= $(CLANG_FLAGS)
+KBUILD_CPPFLAGS	+= $(CLANG_FLAGS)
 export CLANG_FLAGS
 endif
 


Patches currently in stable-queue which might be from nathan@kernel.org are

queue-5.4/kbuild-add-clang_flags-to-as-instr.patch
queue-5.4/wifi-brcmsmac-remove-const-from-tbl_ptr-parameter-in-wlc_lcnphy_common_read_table.patch
queue-5.4/mips-include-kbuild_cppflags-in-checkflags-invocation.patch
queue-5.4/kbuild-add-clang_flags-to-kbuild_cppflags.patch
queue-5.4/ftrace-also-allocate-and-copy-hash-for-reading-of-filter-files.patch
queue-5.4/memstick-core-zero-initialize-id_reg-in-h_memstick_read_dev_id.patch
queue-5.4/kbuild-update-assembler-calls-to-use-proper-flags-and-language-target.patch
queue-5.4/phonet-pep-move-call-to-pn_skb_get_dst_sockaddr-earlier-in-pep_sock_accept.patch
queue-5.4/arm-9448-1-use-an-absolute-path-to-unified.h-in-kbuild_aflags.patch
queue-5.4/kbuild-add-kbuild_cppflags-to-as-option-invocation.patch
queue-5.4/usb-atm-cxacru-merge-cxacru_upload_firmware-into-cxacru_heavy_init.patch