Hi Masahiro, Thanks for the reply. I've been away for a bit, but I've poked at a few more things now. On Sun, May 26, 2024 at 01:35:43AM +0900, Masahiro Yamada wrote: > On Fri, May 24, 2024 at 2:54 AM Brian Norris <briannorris@xxxxxxxxxxxx> wrote: > > --- a/tools/lib/subcmd/Makefile > > +++ b/tools/lib/subcmd/Makefile > > @@ -76,7 +76,7 @@ include $(srctree)/tools/build/Makefile.include > > > > all: fixdep $(LIBFILE) > > > > -$(SUBCMD_IN): FORCE > > +$(SUBCMD_IN): fixdep FORCE > > @$(MAKE) $(build)=libsubcmd > > > > $(LIBFILE): $(SUBCMD_IN) > > > > I may not fully understand the design policy of the tools/ build system, > but this fix is presumably correct because the 'fixdep' binary > is needed in each sub-directory for it to work correctly. > > tools/bpf/resolve_btfids/libsubcmd/.exec-cmd.o.cmd must > be generated by tools/bpf/resolve_btfids/libsubcmd/fixdep > instead of by tools/bpf/resolve_btfids/fixdep. > > But, fixing tools/lib/subcmd/Makefile is not enough. > > *.cmd files under tools/bpf/resolve_btfids/libbpf/staticobjs/ > are broken for the same reason. > So, this is fundamentally broken in many places. I think I hacked something that works there too. It gets a bit uglier, but not too bad IMO. > And, as you noted, there is no easy way to fix .fixdep.o.cmd I haven't come up with a *great* solution, but I came up with something that works for the most part, by circumventing the normal Build / Makefile.build split. It's getting pretty ugly too though... > Your description in > https://issuetracker.google.com/issues/313508829#comment32 > is all correct. > > > "can we just use Kbuild?" is a good question. > I do not understand why they use fragile build systems, > where obviously they cannot do it correctly. > > > In fact, I submitted a patch to migrate objtool to Kbuild > because that fixes all the issues cleanly. > > The objtool maintainers rejected it. > https://lore.kernel.org/linux-kbuild/1551764896-8453-3-git-send-email-yamada.masahiro@xxxxxxxxxxxxx/ > > > Not only the build system. > He also refused to participate in the standard Documentation > directory. > tools/objtool/Documentation/objtool.txt still resides in its own directory. While I don't love having to solve the same problems repeatedly (once in Kbuild; potentially-many in tools/), I'm also OK with trying to hack fixes into the current duplicate build system if it's not prohibitively complex to do so. Here's what I have for now -- I might submit some or all of this as a proper patchset if I can fix a few rough edges. diff --git a/tools/build/Makefile b/tools/build/Makefile index 17cdf01e29a0..fad93f64035d 100644 --- a/tools/build/Makefile +++ b/tools/build/Makefile @@ -43,11 +43,8 @@ ifneq ($(wildcard $(TMP_O)),) $(Q)$(MAKE) -C feature OUTPUT=$(TMP_O) clean >/dev/null endif -$(OUTPUT)fixdep-in.o: FORCE - $(Q)$(MAKE) $(build)=fixdep - -$(OUTPUT)fixdep: $(OUTPUT)fixdep-in.o - $(QUIET_LINK)$(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ $< +$(OUTPUT)fixdep: $(srctree)/tools/build/fixdep.c + $(QUIET_CC)$(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ $< FORCE: diff --git a/tools/build/Makefile.include b/tools/build/Makefile.include index 8dadaa0fbb43..27b2090cb293 100644 --- a/tools/build/Makefile.include +++ b/tools/build/Makefile.include @@ -1,8 +1,16 @@ # SPDX-License-Identifier: GPL-2.0-only build := -f $(srctree)/tools/build/Makefile.build dir=. obj +# More than just $(Q), we sometimes want to suppress all command output from a +# recursive make -- even the 'up to date' printout. +ifeq ($(V),1) + SILENT_MAKE = $(Q)$(MAKE) +else + SILENT_MAKE = $(Q)$(MAKE) --silent +endif + fixdep: - $(Q)$(MAKE) -C $(srctree)/tools/build CFLAGS= LDFLAGS= $(OUTPUT)fixdep + $(SILENT_MAKE) -C $(srctree)/tools/build CFLAGS= LDFLAGS= $(OUTPUT)fixdep fixdep-clean: $(Q)$(MAKE) -C $(srctree)/tools/build clean diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile index 2cf892774346..a8f34de1ca25 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -154,6 +154,8 @@ $(BPF_IN_SHARED): force $(BPF_GENERATED) $(Q)$(MAKE) $(build)=libbpf OUTPUT=$(SHARED_OBJDIR) CFLAGS="$(CFLAGS) $(SHLIB_FLAGS)" $(BPF_IN_STATIC): force $(BPF_GENERATED) + $(call rule_mkdir) + $(SILENT_MAKE) -C $(srctree)/tools/build CFLAGS= LDFLAGS= OUTPUT=$(STATIC_OBJDIR) $(STATIC_OBJDIR)fixdep $(Q)$(MAKE) $(build)=libbpf OUTPUT=$(STATIC_OBJDIR) $(BPF_HELPER_DEFS): $(srctree)/tools/include/uapi/linux/bpf.h diff --git a/tools/lib/subcmd/Makefile b/tools/lib/subcmd/Makefile index b87213263a5e..59b09f280e49 100644 --- a/tools/lib/subcmd/Makefile +++ b/tools/lib/subcmd/Makefile @@ -76,7 +76,7 @@ include $(srctree)/tools/build/Makefile.include all: fixdep $(LIBFILE) -$(SUBCMD_IN): FORCE +$(SUBCMD_IN): fixdep FORCE @$(MAKE) $(build)=libsubcmd $(LIBFILE): $(SUBCMD_IN)
