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Sat, 03 Jun 2023 09:32:58 -0700 (PDT) X-Gm-Message-State: AC+VfDw/WvwZWN9jEyIoBS4JrlcFb50Ldv9hHxC8P749ZzsaElubg5RF b79nbWFEiVcTm0lvc6gVgIfY4JKyFmrKNYxX+q0= X-Received: by 2002:a4a:374c:0:b0:547:5593:d6 with SMTP id r73-20020a4a374c000000b00547559300d6mr7501367oor.5.1685809977529; Sat, 03 Jun 2023 09:32:57 -0700 (PDT) MIME-Version: 1.0 References: <20230409145358.2538266-1-masahiroy@kernel.org> <20230531213319.GA2201875@dev-arch.thelio-3990X> <20230602152519.GA3007575@dev-arch.thelio-3990X> In-Reply-To: <20230602152519.GA3007575@dev-arch.thelio-3990X> From: Masahiro Yamada Date: Sun, 4 Jun 2023 01:32:21 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] kbuild: add $(CLANG_CFLAGS) to KBUILD_CPPFLAGS To: Nathan Chancellor Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Tom Rini , Nick Desaulniers , Nicolas Schier , Tom Rix , llvm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-7.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jun 3, 2023 at 12:25=E2=80=AFAM Nathan Chancellor wrote: > > On Wed, May 31, 2023 at 02:33:23PM -0700, Nathan Chancellor wrote: > > Hi Masahiro, > > > > On Sun, Apr 09, 2023 at 11:53:57PM +0900, Masahiro Yamada wrote: > > > 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 n= ot > > > rely on such predefined macros, but it is better to define correct on= es. > > > > > > Move $(CFLAGS_CFLAGS) to KBUILD_CPPFLAGS, so that all *.c, *.S, *.lds= .S > > > will be processed with the proper target triple. > > > > > > Reported-by: Tom Rini > > > Signed-off-by: Masahiro Yamada > > > --- > > > > > > scripts/Makefile.clang | 3 +-- > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > > > index 70b354fa1cb4..93ca059cc3b8 100644 > > > --- a/scripts/Makefile.clang > > > +++ b/scripts/Makefile.clang > > > @@ -38,6 +38,5 @@ CLANG_FLAGS +=3D -Werror=3Dunknown-warning-op= tion > > > CLANG_FLAGS +=3D -Werror=3Dignored-optimization-argument > > > CLANG_FLAGS +=3D -Werror=3Doption-ignored > > > CLANG_FLAGS +=3D -Werror=3Dunused-command-line-argument > > > -KBUILD_CFLAGS +=3D $(CLANG_FLAGS) > > > -KBUILD_AFLAGS +=3D $(CLANG_FLAGS) > > > +KBUILD_CPPFLAGS +=3D $(CLANG_FLAGS) > > > export CLANG_FLAGS > > > -- > > > 2.37.2 > > > > > > > I am doubling back to this change, as the lack of '--target' in > > KBUILD_CPPFLAGS is now an active bug with clang-17 due to a new change > > that rejects '-mbig-endian' and '-mlittle-endian' when not supported by > > the target, which breaks the arm64 vDSO build when preprocessing its > > linker script: > > > > # Turn on CONFIG_CPU_BIG_ENDIAN in menuconfig > > $ make -skj"$(nproc)" ARCH=3Darm64 LLVM=3D1 O=3Dbuild mrproper virtco= nfig menuconfig arch/arm64/kernel/vdso/ > > ... > > clang: error: unsupported option '-mbig-endian' for target 'x86_64-pc= -linux-gnu' > > make[3]: *** [.../scripts/Makefile.build:387: arch/arm64/kernel/vdso/= vdso.lds] Error 1 > > ... > > > > https://github.com/llvm/llvm-project/commit/d81ce04587c006b6731198956= c522c93d0df1050 > > https://github.com/ClangBuiltLinux/linux/issues/1859 > > > > This change resolves that issue. I was able to figure out why those new > > warnings appeared for ARCH=3Dmips, it is the shell invocation for > > CHECKFLAGS. The following diff resolves it for me: > > > > diff --git a/arch/mips/Makefile b/arch/mips/Makefile > > index a7a4ee66a9d3..ef7b05ae92ce 100644 > > --- a/arch/mips/Makefile > > +++ b/arch/mips/Makefile > > @@ -346,7 +346,7 @@ KBUILD_CFLAGS +=3D -fno-asynchronous-unwind-tables > > KBUILD_LDFLAGS +=3D -m $(ld-emul) > > > > ifdef CONFIG_MIPS > > -CHECKFLAGS +=3D $(shell $(CC) $(KBUILD_CFLAGS) -dM -E -x c /dev/null |= \ > > +CHECKFLAGS +=3D $(shell $(CC) $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) -dM = -E -x c /dev/null | \ > > grep -E -vw '__GNUC_(MINOR_|PATCHLEVEL_)?_' | \ > > sed -e "s/^\#define /-D'/" -e "s/ /'=3D'/" -e "s/$$/'/" -e 's/\$$= /&&/g') > > endif > > > > I will run this change plus that diff through my build matrix to see if > > any other issues pop up. If not, I will respond with some tags and > > perhaps this could be taken as a fix for 6.4 so that it could > > potentially be backported? > > I found two more issues lurking in PowerPC. I have attached suggested > patches for all the issues I have uncovered to this email, please feel > free to use them or do something different if you feel there is a better > fix. With those issues resolved in one way or another, consider the > original change: > > Reviewed-by: Nathan Chancellor > Tested-by: Nathan Chancellor > > If it would work better for you, I am more than happy to take over this > series as well. > > Cheers, > Nathan Thanks. All the three patches look good to me. I will apply them, then mine on top. A nit: The first patch for mips will introduce the warning as $(KBUILD_CPPFLAGS) does not contain $(CLANG_FLAGS) at this point. Then, it will be fixed again when my patch is applied. The two must be squashed together to avoid the regression, but I think it is OK as-is. The second patch for powerpc reminded me of converting $(CC) to $(LD) for linking vDSO. I do not remember why powerpc vDSO still uses $(CC). -- Best Regards Masahiro Yamada