Re: [PATCH] samples/bpf: Add BTF build flags to Makefile

[Taeung Song]

On 07/26/2018 10:16 AM, Jakub Kicinski wrote:
> On Thu, 26 Jul 2018 01:30:39 +0900, Taeung Song wrote:
> > To smoothly test BTF supported binary on samples/bpf,
> > let samples/bpf/Makefile probe llc, pahole and
> > llvm-objcopy for BPF support and use them
> > like tools/testing/selftests/bpf/Makefile
> > changed from the commit c0fa1b6c3efc ("bpf: btf:
> >   Add BTF tests")
> >
> > Cc: Martin KaFai Lau <kafai@xxxxxx>
> > Signed-off-by: Taeung Song <treeze.taeung@xxxxxxxxx>
> > ---
> >   samples/bpf/Makefile | 21 ++++++++++++++++++++-
> >   1 file changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> > index 1303af10e54d..e079266360a3 100644
> > --- a/samples/bpf/Makefile
> > +++ b/samples/bpf/Makefile
> > @@ -191,6 +191,8 @@ HOSTLOADLIBES_xdpsock		+= -pthread
> >   #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
> >   LLC ?= llc
> >   CLANG ?= clang
> > +LLVM_OBJCOPY ?= llvm-objcopy
> > +BTF_PAHOLE ?= pahole
> >   
> >   # Detect that we're cross compiling and use the cross compiler
> >   ifdef CROSS_COMPILE
> > @@ -198,6 +200,20 @@ HOSTCC = $(CROSS_COMPILE)gcc
> >   CLANG_ARCH_ARGS = -target $(ARCH)
> >   endif
> >   
> > +BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
> > +BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
> > +BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
> > +
> > +ifneq ($(BTF_LLC_PROBE),)
> > +ifneq ($(BTF_PAHOLE_PROBE),)
> > +ifneq ($(BTF_OBJCOPY_PROBE),)
>
> Nice patch!  FWIW you could consider using $(and ...) here:
>
> ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
>
> https://www.gnu.org/software/make/manual/html_node/Conditional-Functions.html#Conditional-Functions
>
> Not sure it's worth a respin..

Hi Jakub,

Thanks for reviewing this.
I also think the conditional functions looks more tidy, will change it!

Thanks,
Taeung

> > +	EXTRA_CFLAGS += -g
> > +	LLC_FLAGS += -mattr=dwarfris
> > +	DWARF2BTF = y
> > +endif
> > +endif
> > +endif
> > +
> >   # Trick to allow make to be run from this directory
> >   all:
> >   	$(MAKE) -C ../../ $(CURDIR)/ BPF_SAMPLES_PATH=$(CURDIR)
> > @@ -256,4 +272,7 @@ $(obj)/%.o: $(src)/%.c
> >   		-Wno-gnu-variable-sized-type-not-at-end \
> >   		-Wno-address-of-packed-member -Wno-tautological-compare \
> >   		-Wno-unknown-warning-option $(CLANG_ARCH_ARGS) \
> > -		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf -filetype=obj -o $@
> > +		-O2 -emit-llvm -c $< -o -| $(LLC) -march=bpf $(LLC_FLAGS) -filetype=obj -o $@
> > +ifeq ($(DWARF2BTF),y)
> > +	$(BTF_PAHOLE) -J $@
> > +endif