Re: [PATCH bpf-next v2] tools/runqslower: Fix LDFLAGS and add LDLIBS support

[Tony Ambardar <tony.ambardar@gmail.com>]

On Tue, Jul 23, 2024 at 09:56:56AM +0200, Ilya Leoshkevich wrote:
> On Mon, 2024-07-22 at 17:30 -0700, Tony Ambardar wrote:
> > Actually use previously defined LDFLAGS during build and add support
> > for
> > LDLIBS to link extra standalone libraries e.g. 'argp' which is not
> > provided
> > by musl libc.
> > 
> > Fixes: 585bf4640ebe ("tools: runqslower: Add EXTRA_CFLAGS and
> > EXTRA_LDFLAGS support")
> > Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>
> > ---
> > v1-v2:
> >  - add missing CC for Ilya
> > 
> > ---
> >  tools/bpf/runqslower/Makefile | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/bpf/runqslower/Makefile
> > b/tools/bpf/runqslower/Makefile
> > index d8288936c912..c4f1f1735af6 100644
> > --- a/tools/bpf/runqslower/Makefile
> > +++ b/tools/bpf/runqslower/Makefile
> > @@ -15,6 +15,7 @@ INCLUDES := -I$(OUTPUT) -I$(BPF_INCLUDE) -
> > I$(abspath ../../include/uapi)
> >  CFLAGS := -g -Wall $(CLANG_CROSS_FLAGS)
> >  CFLAGS += $(EXTRA_CFLAGS)
> >  LDFLAGS += $(EXTRA_LDFLAGS)
> > +LDLIBS += -lelf -lz
> >  
> >  # Try to detect best kernel BTF source
> >  KERNEL_REL := $(shell uname -r)
> > @@ -51,7 +52,7 @@ clean:
> >  libbpf_hdrs: $(BPFOBJ)
> >  
> >  $(OUTPUT)/runqslower: $(OUTPUT)/runqslower.o $(BPFOBJ)
> > -	$(QUIET_LINK)$(CC) $(CFLAGS) $^ -lelf -lz -o $@
> > +	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $^ $(LDLIBS) -o $@
> >  
> >  $(OUTPUT)/runqslower.o: runqslower.h
> > $(OUTPUT)/runqslower.skel.h	      \
> >  			$(OUTPUT)/runqslower.bpf.o | libbpf_hdrs
> 
> Looks reasonable to me, but I don't quite get what exactly did
> 585bf4640ebe break? In any case:
> 
> Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>

I believe 585bf4640ebe added the LDFLAGS definition above but then didn't
include it in the runqslower target's compile command. I only happened to
notice while adding LDLIBS.

Thanks for looking at this.