netdev - Re: [PATCH bpf] bpftool: Install libbpf headers for the bootstrap version, too

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Date:   Fri, 5 Nov 2021 07:57:38 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Quentin Monnet <quentin@...valent.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Song Liu <songliubraving@...com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf] bpftool: Install libbpf headers for the bootstrap
 version, too

Em Fri, Nov 05, 2021 at 07:55:20AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Nov 05, 2021 at 01:58:13AM +0000, Quentin Monnet escreveu:
> > We recently changed bpftool's Makefile to make it install libbpf's
> > headers locally instead of pulling them from the source directory of the
> > library. Although bpftool needs two versions of libbpf, a "regular" one
> > and a "bootstrap" version, we would only install headers for the regular
> > libbpf build. Given that this build always occurs before the bootstrap
> > build when building bpftool, this is enough to ensure that the bootstrap
> > bpftool will have access to the headers exported through the regular
> > libbpf build.
 
> > However, this did not account for the case when we only want the
> > bootstrap version of bpftool, through the "bootstrap" target. For
> > example, perf needs the bootstrap version only, to generate BPF
> > skeletons. In that case, when are the headers installed? For some time,
> > the issue has been masked, because we had a step (the installation of
> > headers internal to libbpf) which would depend on the regular build of
> > libbpf and hence trigger the export of the headers, just for the sake of
> > creating a directory. But this changed with commit 8b6c46241c77
> > ("bpftool: Remove Makefile dep. on $(LIBBPF) for
> > $(LIBBPF_INTERNAL_HDRS)"), where we cleaned up that stage and removed
> > the dependency on the regular libbpf build. As a result, when we only
> > want the bootstrap bpftool version, the regular libbpf is no longer
> > built. The bootstrap libbpf version is built, but headers are not
> > exported, and the bootstrap bpftool build fails because of the missing
> > headers.
 
> > To fix this, we also install the library headers for the bootstrap
> > version of libbpf, to use them for the bootstrap bpftool and for
> > generating the skeletons.
> 
> Reported-by: Arnaldo Carvalho de Melo <acme@...hat.com>
 
> Testing now.

Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>

With just this patch (and removing the revert I did), it works, thanks!

- Arnaldo
 
> > Fixes: f012ade10b34 ("bpftool: Install libbpf headers instead of including the dir")
> > Signed-off-by: Quentin Monnet <quentin@...valent.com>
> > ---
> >  tools/bpf/bpftool/Makefile | 32 ++++++++++++++++++++++----------
> >  1 file changed, 22 insertions(+), 10 deletions(-)
> > 
> > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> > index c0c30e56988f..7cfba11c3014 100644
> > --- a/tools/bpf/bpftool/Makefile
> > +++ b/tools/bpf/bpftool/Makefile
> > @@ -22,24 +22,29 @@ else
> >    _OUTPUT := $(CURDIR)
> >  endif
> >  BOOTSTRAP_OUTPUT := $(_OUTPUT)/bootstrap/
> > +
> >  LIBBPF_OUTPUT := $(_OUTPUT)/libbpf/
> >  LIBBPF_DESTDIR := $(LIBBPF_OUTPUT)
> >  LIBBPF_INCLUDE := $(LIBBPF_DESTDIR)/include
> >  LIBBPF_HDRS_DIR := $(LIBBPF_INCLUDE)/bpf
> > +LIBBPF := $(LIBBPF_OUTPUT)libbpf.a
> >  
> > -LIBBPF = $(LIBBPF_OUTPUT)libbpf.a
> > -LIBBPF_BOOTSTRAP_OUTPUT = $(BOOTSTRAP_OUTPUT)libbpf/
> > -LIBBPF_BOOTSTRAP = $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
> > +LIBBPF_BOOTSTRAP_OUTPUT := $(BOOTSTRAP_OUTPUT)libbpf/
> > +LIBBPF_BOOTSTRAP_DESTDIR := $(LIBBPF_BOOTSTRAP_OUTPUT)
> > +LIBBPF_BOOTSTRAP_INCLUDE := $(LIBBPF_BOOTSTRAP_DESTDIR)/include
> > +LIBBPF_BOOTSTRAP_HDRS_DIR := $(LIBBPF_BOOTSTRAP_INCLUDE)/bpf
> > +LIBBPF_BOOTSTRAP := $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
> >  
> >  # We need to copy hashmap.h and nlattr.h which is not otherwise exported by
> >  # libbpf, but still required by bpftool.
> >  LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,hashmap.h nlattr.h)
> > +LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hashmap.h)
> >  
> >  ifeq ($(BPFTOOL_VERSION),)
> >  BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
> >  endif
> >  
> > -$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR):
> > +$(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR) $(LIBBPF_BOOTSTRAP_HDRS_DIR):
> >  	$(QUIET_MKDIR)mkdir -p $@
> >  
> >  $(LIBBPF): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_OUTPUT)
> > @@ -52,7 +57,12 @@ $(LIBBPF_INTERNAL_HDRS): $(LIBBPF_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_HDRS_
> >  
> >  $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
> >  	$(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(LIBBPF_BOOTSTRAP_OUTPUT) \
> > -		ARCH= CC=$(HOSTCC) LD=$(HOSTLD) $@
> > +		DESTDIR=$(LIBBPF_BOOTSTRAP_DESTDIR) prefix= \
> > +		ARCH= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
> > +
> > +$(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR)
> > +	$(call QUIET_INSTALL, $@)
> > +	$(Q)install -m 644 -t $(LIBBPF_BOOTSTRAP_HDRS_DIR) $<
> >  
> >  $(LIBBPF)-clean: FORCE | $(LIBBPF_OUTPUT)
> >  	$(call QUIET_CLEAN, libbpf)
> > @@ -172,11 +182,11 @@ else
> >  	$(Q)cp "$(VMLINUX_H)" $@
> >  endif
> >  
> > -$(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF)
> > +$(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF_BOOTSTRAP)
> >  	$(QUIET_CLANG)$(CLANG) \
> >  		-I$(if $(OUTPUT),$(OUTPUT),.) \
> >  		-I$(srctree)/tools/include/uapi/ \
> > -		-I$(LIBBPF_INCLUDE) \
> > +		-I$(LIBBPF_BOOTSTRAP_INCLUDE) \
> >  		-g -O2 -Wall -target bpf -c $< -o $@ && $(LLVM_STRIP) -g $@
> >  
> >  $(OUTPUT)%.skel.h: $(OUTPUT)%.bpf.o $(BPFTOOL_BOOTSTRAP)
> > @@ -209,8 +219,10 @@ $(BPFTOOL_BOOTSTRAP): $(BOOTSTRAP_OBJS) $(LIBBPF_BOOTSTRAP)
> >  $(OUTPUT)bpftool: $(OBJS) $(LIBBPF)
> >  	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
> >  
> > -$(BOOTSTRAP_OUTPUT)%.o: %.c $(LIBBPF_INTERNAL_HDRS) | $(BOOTSTRAP_OUTPUT)
> > -	$(QUIET_CC)$(HOSTCC) $(CFLAGS) -c -MMD -o $@ $<
> > +$(BOOTSTRAP_OUTPUT)%.o: %.c $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS) | $(BOOTSTRAP_OUTPUT)
> > +	$(QUIET_CC)$(HOSTCC) \
> > +		$(subst -I$(LIBBPF_INCLUDE),-I$(LIBBPF_BOOTSTRAP_INCLUDE),$(CFLAGS)) \
> > +		-c -MMD -o $@ $<
> >  
> >  $(OUTPUT)%.o: %.c
> >  	$(QUIET_CC)$(CC) $(CFLAGS) -c -MMD -o $@ $<
> > @@ -257,6 +269,6 @@ doc-uninstall:
> >  FORCE:
> >  
> >  .SECONDARY:
> > -.PHONY: all FORCE clean install-bin install uninstall
> > +.PHONY: all FORCE bootstrap clean install-bin install uninstall
> >  .PHONY: doc doc-clean doc-install doc-uninstall
> >  .DEFAULT_GOAL := all
> > -- 
> > 2.32.0