linux-kernel - Re: [PATCH v2 2/2] tools/resolve_btfids: Alter how HOSTCC is forced

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Date:   Tue, 17 Jan 2023 15:20:38 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>,
        Connor OBrien <connoro@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] tools/resolve_btfids: Alter how HOSTCC is forced

On Tue, Jan 17, 2023 at 2:07 PM Jiri Olsa <olsajiri@...il.com> wrote:
>
> On Mon, Jan 16, 2023 at 01:57:51PM -0800, Ian Rogers wrote:
> > HOSTCC is always wanted when building. Setting CC to HOSTCC happens
> > after tools/scripts/Makefile.include is included, meaning flags are
> > set assuming say CC is gcc, but then it can be later set to HOSTCC
> > which may be clang. tools/scripts/Makefile.include is needed for host
> > set up and common macros in objtool's Makefile. Rather than override
> > CC to HOSTCC, just pass CC as HOSTCC to Makefile.build, the libsubcmd
> > builds and the linkage step. This means the Makefiles don't see things
> > like CC changing and tool flag determination, and similar, work
> > properly.
> >
> > Also, clear the passed subdir as otherwise an outer build may break by
> > inadvertently passing an inappropriate value.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
>
> lgtm did you try cross build and build with clang?

Hmm.. I don't have a cross build but I checked clang. Any chance you
could check the cross build?

Thanks,
Ian

> jirka
>
> > ---
> >  tools/bpf/resolve_btfids/Makefile | 17 +++++++----------
> >  1 file changed, 7 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
> > index 76b737b2560d..515d87b32fb8 100644
> > --- a/tools/bpf/resolve_btfids/Makefile
> > +++ b/tools/bpf/resolve_btfids/Makefile
> > @@ -18,14 +18,11 @@ else
> >  endif
> >
> >  # always use the host compiler
> > -AR       = $(HOSTAR)
> > -CC       = $(HOSTCC)
> > -LD       = $(HOSTLD)
> > -ARCH     = $(HOSTARCH)
> > +HOST_OVERRIDES := AR=$(HOSTAR) CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)" \
> > +               ARCH=$(HOSTARCH) EXTRA_CFLAGS="$(HOSTCFLAGS) $(KBUILD_HOSTCFLAGS)"
> > +
> >  RM      ?= rm
> >  CROSS_COMPILE =
> > -CFLAGS  := $(KBUILD_HOSTCFLAGS)
> > -LDFLAGS := $(KBUILD_HOSTLDFLAGS)
> >
> >  OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/
> >
> > @@ -56,12 +53,12 @@ $(OUTPUT) $(OUTPUT)/libsubcmd $(LIBBPF_OUT):
> >
> >  $(SUBCMDOBJ): fixdep FORCE | $(OUTPUT)/libsubcmd
> >       $(Q)$(MAKE) -C $(SUBCMD_SRC) OUTPUT=$(SUBCMD_OUT) \
> > -                 DESTDIR=$(SUBCMD_DESTDIR) prefix= \
> > +                 DESTDIR=$(SUBCMD_DESTDIR) $(HOST_OVERRIDES) prefix= subdir= \
> >                   $(abspath $@) install_headers
> >
> >  $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUT)
> >       $(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) OUTPUT=$(LIBBPF_OUT)    \
> > -                 DESTDIR=$(LIBBPF_DESTDIR) prefix= EXTRA_CFLAGS="$(CFLAGS)" \
> > +                 DESTDIR=$(LIBBPF_DESTDIR) $(HOST_OVERRIDES) prefix= subdir= \
> >                   $(abspath $@) install_headers
> >
> >  CFLAGS += -g \
> > @@ -76,11 +73,11 @@ export srctree OUTPUT CFLAGS Q
> >  include $(srctree)/tools/build/Makefile.include
> >
> >  $(BINARY_IN): fixdep FORCE prepare | $(OUTPUT)
> > -     $(Q)$(MAKE) $(build)=resolve_btfids
> > +     $(Q)$(MAKE) $(build)=resolve_btfids $(HOST_OVERRIDES)
> >
> >  $(BINARY): $(BPFOBJ) $(SUBCMDOBJ) $(BINARY_IN)
> >       $(call msg,LINK,$@)
> > -     $(Q)$(CC) $(BINARY_IN) $(LDFLAGS) -o $@ $(BPFOBJ) $(SUBCMDOBJ) $(LIBS)
> > +     $(Q)$(HOSTCC) $(BINARY_IN) $(KBUILD_HOSTLDFLAGS) -o $@ $(BPFOBJ) $(SUBCMDOBJ) $(LIBS)
> >
> >  clean_objects := $(wildcard $(OUTPUT)/*.o                \
> >                              $(OUTPUT)/.*.o.cmd           \
> > --
> > 2.39.0.314.g84b9a713c41-goog
> >