On Sun, Apr 16, 2023 at 10:02:12PM +0900, Masahiro Yamada wrote: > On Mon, Apr 3, 2023 at 11:48 PM Nathan Chancellor <nathan@xxxxxxxxxx> wrote: > > > > On Sun, Apr 02, 2023 at 02:01:17AM +0900, Masahiro Yamada wrote: > > > The target triple is overridden by the user-supplied CROSS_COMPILE, > > > but I do not see a good reason to support it. Users can use a new > > > architecture without adding CLANG_TARGET_FLAGS_*, but that would be > > > a rare case. > > > > > > Use the hard-coded and deterministic target triple all the time. > > > > > > Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> > > > > I know of one bug where the value of '--target' matters: > > > > https://github.com/ClangBuiltLinux/linux/issues/1244 > > > I did not look into it closely, but if we say Heh, neither did I when I wrote the initial response to this patch, because that issue turns out to be entirely irrelevant for this patch :) > " > Using either CROSS_COMPILE=powerpc64-linux-gnu- or > CROSS_COMPILE=powerpc-linux-gnu- fixes it. > Using KCFLAGS=-v reveals that powerpc64le-linux-gnu-as is not getting > the endianness information. > ", why didn't we fix it like the following? It is because this already technically happens under the hood with clang. '--target=powerpc64le-linux-gnu -mbig-endian' is functionally equivalent to '--target=powerpc64-linux-gnu'. The issue is that '--target=powerpc64-linux-gnu' and '--target=powerpc-linux-gnu' were not passing along '-mbig-endian' to the assembler, so powerpc64le-linux-gnu-ld was expecting big endian object files due to '-EB' in LDFLAGS but was getting little endian object files, since the assembler's triple was little endian by default. We could work around this in the kernel by explicitly passing '-Wa,-mlittle-endian' for these older versions of clang but I do not think it is worth it, especially since it will just get removed once we no longer support clang-11, which is our next uprev. TL;DR: Patch should be fine, issue is tangential. > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > index 70b354fa1cb4..8dda7dc69c93 100644 > --- a/scripts/Makefile.clang > +++ b/scripts/Makefile.clang > @@ -6,7 +6,7 @@ CLANG_TARGET_FLAGS_arm64 := aarch64-linux-gnu > CLANG_TARGET_FLAGS_hexagon := hexagon-linux-musl > CLANG_TARGET_FLAGS_m68k := m68k-linux-gnu > CLANG_TARGET_FLAGS_mips := mipsel-linux-gnu > -CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu > +CLANG_TARGET_FLAGS_powerpc := powerpc64-linux-gnu > CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu > CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu > CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu > > > > We do not need to test all possible target triples. > > > We can just use the one that is known to work. > Anyway, I will apply this patch. Thanks. > > > > > > This was fixed in LLVM 12.0.0. We are not testing this in our CI though, > > so we would not get bit by this (we could bump the minimum supported > > version of LLVM to 12.0.0 for this, we have talked recently about doing > > it for other reasons). > > > > I guess I cannot really think of a good reason not to do this aside from > > that; the target triple should only affect code generation, rather than > > tool selection (i.e., this does not take away the ability to use a > > custom set of binutils with clang). > > > > However, Nick is currently OOO and I would like his opinion voiced > > before we commit to this. Consider this a tentative: > > > > Acked-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > > > > --- > > > > > > scripts/Makefile.clang | 8 ++------ > > > 1 file changed, 2 insertions(+), 6 deletions(-) > > > > > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > > > index 70b354fa1cb4..9076cc939e87 100644 > > > --- a/scripts/Makefile.clang > > > +++ b/scripts/Makefile.clang > > > @@ -13,15 +13,11 @@ CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu > > > CLANG_TARGET_FLAGS_um := $(CLANG_TARGET_FLAGS_$(SUBARCH)) > > > CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH)) > > > > > > -ifeq ($(CROSS_COMPILE),) > > > ifeq ($(CLANG_TARGET_FLAGS),) > > > -$(error Specify CROSS_COMPILE or add '--target=' option to scripts/Makefile.clang) > > > +$(error add '--target=' option to scripts/Makefile.clang) > > > else > > > CLANG_FLAGS += --target=$(CLANG_TARGET_FLAGS) > > > -endif # CLANG_TARGET_FLAGS > > > -else > > > -CLANG_FLAGS += --target=$(notdir $(CROSS_COMPILE:%-=%)) > > > -endif # CROSS_COMPILE > > > +endif > > > > > > ifeq ($(LLVM_IAS),0) > > > CLANG_FLAGS += -fno-integrated-as > > > -- > > > 2.37.2 > > > > > > > -- > Best Regards > Masahiro Yamada
