Re: [PATCH v3 bpf-next 08/14] samples: bpf: makefile: base target programs rules on Makefile.target

[Ivan Khoronzhuk]

On Tue, Sep 17, 2019 at 04:28:01PM -0700, Andrii Nakryiko wrote:
> On Mon, Sep 16, 2019 at 3:58 AM Ivan Khoronzhuk
> <ivan.khoronzhuk@xxxxxxxxxx> wrote:
> >
>
> Please don't prepend "samples: bpf: makefile:" to patches,
> "samples/bpf: " is a typical we've used for BPF samples changes.
Ok.

> > The main reason for that - HOSTCC and CC have different aims.
> > HOSTCC is used to build programs running on host, that can
> > cross-comple target programs with CC. It was tested for arm and arm64
> > cross compilation, based on linaro toolchain, but should work for
> > others.
> >
> > So, in order to split cross compilation (CC) with host build (HOSTCC),
> > lets base samples on Makefile.target. It allows to cross-compile
> > samples/bpf programs with CC while auxialry tools running on host
> > built with HOSTCC.
> >
> > Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>
> > ---
> >  samples/bpf/Makefile | 135 ++++++++++++++++++++++---------------------
> >  1 file changed, 69 insertions(+), 66 deletions(-)
> >
> > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> > index 9d923546e087..1579cc16a1c2 100644
> > --- a/samples/bpf/Makefile
> > +++ b/samples/bpf/Makefile
> > @@ -4,55 +4,53 @@ BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
> >  TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools
> >
> >  # List of programs to build
> > -hostprogs-y := test_lru_dist
[...]
> > -KBUILD_HOSTCFLAGS := $(ARM_ARCH_SELECTOR)
> > +TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
> >  endif
> >
> > +TPROGS_LDLIBS := $(KBUILD_HOSTLDLIBS)
>
> Please group TPROGS_LDLIBS definition together with the one below,
> there doesn't seem to be a reason to split them this way.
No. It's used in Makefile.target and should be here, following hostprog logic.

> But also, it's kind of weird to use host libraries as cross-compiled
> libraries as well. Is that intentional?
No cross-compile split yet. This patch replace only KBUILD on TPROGS.
It's done in following patches.

> > +TPROGS_CFLAGS += $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS)
>
> Same here, is it right to use HOSTCFLAGS and HOST_EXTRACFLAGS as a
> base for cross-compiled cflags?
same

[...]

--
Regards,
Ivan Khoronzhuk