On Wed, Sep 18, 2019 at 3:35 AM Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> wrote: > > On Tue, Sep 17, 2019 at 04:42:07PM -0700, Andrii Nakryiko wrote: > >On Mon, Sep 16, 2019 at 3:59 AM Ivan Khoronzhuk > ><ivan.khoronzhuk@xxxxxxxxxx> wrote: > >> > >> While compile natively, the hosts cflags and ldflags are equal to ones > >> used from HOSTCFLAGS and HOSTLDFLAGS. When cross compiling it should > >> have own, used for target arch. While verification, for arm, arm64 and > >> x86_64 the following flags were used alsways: > >> > >> -Wall > >> -O2 > >> -fomit-frame-pointer > >> -Wmissing-prototypes > >> -Wstrict-prototypes > >> > >> So, add them as they were verified and used before adding > >> Makefile.target, but anyway limit it only for cross compile options as > >> for host can be some configurations when another options can be used, > >> So, for host arch samples left all as is, it allows to avoid potential > >> option mistmatches for existent environments. > >> > >> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> > >> --- > >> samples/bpf/Makefile | 9 +++++++++ > >> 1 file changed, 9 insertions(+) > >> > >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile > >> index 1579cc16a1c2..b5c87a8b8b51 100644 > >> --- a/samples/bpf/Makefile > >> +++ b/samples/bpf/Makefile > >> @@ -178,8 +178,17 @@ CLANG_EXTRA_CFLAGS := $(ARM_ARCH_SELECTOR) > >> TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR) > >> endif > >> > >> +ifdef CROSS_COMPILE > >> +TPROGS_CFLAGS += -Wall > >> +TPROGS_CFLAGS += -O2 > > > >Specifying one arg per line seems like overkill, put them in one line? > Will combine. > > > > >> +TPROGS_CFLAGS += -fomit-frame-pointer > > > >Why this one? > I've explained in commit msg. The logic is to have as much as close options > to have smiliar binaries. As those options are used before for hosts and kinda > cross builds - better follow same way. I'm just asking why omit frame pointers and make it harder to do stuff like profiling? What performance benefits are we seeking for in BPF samples? > > > > >> +TPROGS_CFLAGS += -Wmissing-prototypes > >> +TPROGS_CFLAGS += -Wstrict-prototypes > > > >Are these in some way special that we want them in cross-compile mode only? > > > >All of those flags seem useful regardless of cross-compilation or not, > >shouldn't they be common? I'm a bit lost about the intent here... > They are common but split is needed to expose it at least. Also host for > different arches can have some own opts already used that shouldn't be present > for cross, better not mix it for safety. We want -Wmissing-prototypes and -Wstrict-prototypes for cross-compile and non-cross-compile cases, right? So let's specify them as common set of options, instead of relying on KBUILD_HOSTCFLAGS or HOST_EXTRACFLAGS to have them. Otherwise we'll be getting extra warnings for just cross-compile case, which is not good. If you are worrying about having duplicate -W flags, seems like it's handled by GCC already, so shouldn't be a problem. > > > > >> +else > >> TPROGS_LDLIBS := $(KBUILD_HOSTLDLIBS) > >> TPROGS_CFLAGS += $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS) > >> +endif > >> + > >> TPROGS_CFLAGS += -I$(objtree)/usr/include > >> TPROGS_CFLAGS += -I$(srctree)/tools/lib/bpf/ > >> TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/ > >> -- > >> 2.17.1 > >> > > -- > Regards, > Ivan Khoronzhuk
