On Mon, Jan 09, 2023 at 02:08:41PM -0800, Nick Desaulniers wrote: > On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <nathan@xxxxxxxxxx> wrote: > > > > When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, there > > are several warnings in the PowerPC vDSO: > > > > clang-16: error: -Wl,-soname=linux-vdso32.so.1: 'linker' input unused [-Werror,-Wunused-command-line-argument] > > clang-16: error: -Wl,--hash-style=both: 'linker' input unused [-Werror,-Wunused-command-line-argument] > > clang-16: error: argument unused during compilation: '-shared' [-Werror,-Wunused-command-line-argument] > > > > clang-16: error: argument unused during compilation: '-nostdinc' [-Werror,-Wunused-command-line-argument] > > clang-16: error: argument unused during compilation: '-Wa,-maltivec' [-Werror,-Wunused-command-line-argument] > > > > The first group of warnings point out that linker flags were being added > > to all invocations of $(CC), even though they will only be used during > > the final vDSO link. Move those flags to ldflags-y. > > > > The second group of warnings are compiler or assembler flags that will > > be unused during linking. Filter them out from KBUILD_CFLAGS so that > > they are not used during linking. > > > > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > --- > > Cc: mpe@xxxxxxxxxxxxxx > > Cc: npiggin@xxxxxxxxx > > Cc: christophe.leroy@xxxxxxxxxx > > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx > > --- > > arch/powerpc/kernel/vdso/Makefile | 18 +++++++++++------- > > 1 file changed, 11 insertions(+), 7 deletions(-) > > > > diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile > > index 45c0cc5d34b6..769b62832b38 100644 > > --- a/arch/powerpc/kernel/vdso/Makefile > > +++ b/arch/powerpc/kernel/vdso/Makefile > > @@ -47,13 +47,17 @@ KCOV_INSTRUMENT := n > > UBSAN_SANITIZE := n > > KASAN_SANITIZE := n > > > > -ccflags-y := -shared -fno-common -fno-builtin -nostdlib -Wl,--hash-style=both > > -ccflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld) > > - > > -CC32FLAGS := -Wl,-soname=linux-vdso32.so.1 -m32 > > +ccflags-y := -fno-common -fno-builtin > > +ldflags-y := -Wl,--hash-style=both -nostdlib -shared > > +ldflags-$(CONFIG_LD_IS_LLD) += $(call cc-option,--ld-path=$(LD),-fuse-ld=lld) > > +# Filter flags that clang will warn are unused for linking > > +ldflags-y += $(filter-out $(CC_FLAGS_FTRACE) -Wa$(comma)%, $(KBUILD_CFLAGS)) > > + > > +CC32FLAGS := -m32 > > +LD32FLAGS := -Wl,-soname=linux-vdso32.so.1 > > AS32FLAGS := -D__VDSO32__ > > > > -CC64FLAGS := -Wl,-soname=linux-vdso64.so.1 > > +LD64FLAGS := -Wl,-soname=linux-vdso64.so.1 > > AS64FLAGS := -D__VDSO64__ > > > > targets += vdso32.lds > > @@ -92,14 +96,14 @@ include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE > > > > # actual build commands > > quiet_cmd_vdso32ld_and_check = VDSO32L $@ > > - cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check) > > + cmd_vdso32ld_and_check = $(VDSOCC) $(ldflags-y) $(CC32FLAGS) $(LD32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check) > > quiet_cmd_vdso32as = VDSO32A $@ > > cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) $(AS32FLAGS) -c -o $@ $< > > quiet_cmd_vdso32cc = VDSO32C $@ > > cmd_vdso32cc = $(VDSOCC) $(c_flags) $(CC32FLAGS) -c -o $@ $< > > > > quiet_cmd_vdso64ld_and_check = VDSO64L $@ > > - cmd_vdso64ld_and_check = $(VDSOCC) $(c_flags) $(CC64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check) > > + cmd_vdso64ld_and_check = $(VDSOCC) $(ldflags-y) $(CC64FLAGS) $(LD64FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) -z noexecstack ; $(cmd_vdso_check) > > Let's move `-z noexecstack` up into ldflags-y? (you may add my RB with > that modification) Ack, done locally, will be included in v2. > > quiet_cmd_vdso64as = VDSO64A $@ > > cmd_vdso64as = $(VDSOCC) $(a_flags) $(CC64FLAGS) $(AS64FLAGS) -c -o $@ $< > > > > > > -- > > 2.39.0 > > > > -- > Thanks, > ~Nick Desaulniers
