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We're missing one such dependency before the libsubcmd target. This resolves .cmd file generation issues such that the following sequence produces many fewer results: $ git clean -xfd tools/ $ make tools/objtool $ grep "cannot find fixdep" $(find tools/objtool -name '*.cmd') In particular, only a buggy tools/objtool/libsubcmd/.fixdep.o.cmd remains, due to circular dependencies of fixdep on itself. Such incomplete .cmd files don't usually cause a direct problem, since they're designed to fail "open", but they can cause some subtle problems that would otherwise be handled by proper fixdep'd dependency files. [2] [1] This problem is better described in commit abb26210a395 ("perf tools: Force fixdep compilation at the start of the build"). I don't apply its solution here, because additional recursive make can be a bit of overkill. [2] Example failure case: cp -arl linux-src linux-src2 cd linux-src2 make O=3D/path/to/out cd ../linux-src rm -rf ../linux-src2 make O=3D/path/to/out Previously, we'd see errors like: make[6]: *** No rule to make target '/path/to/linux-src2/tools/include/linux/compiler.h', needed by '/path/to/out/tools/bpf/resolve_btfids/libsubcmd/exec-cmd.o'. Stop. Now, the properly-fixdep'd .cmd files will ignore a missing /path/to/linux-src2/... Link: https://lore.kernel.org/all/ZGVi9HbI43R5trN8@bhelgaas/ Link: https://lore.kernel.org/all/Zk-C5Eg84yt6_nml@google.com/ Signed-off-by: Brian Norris Acked-by: Jiri Olsa --- (no changes since v3) Changes in v3: - update notes about failure cases - add Jiri's Acked-by tools/lib/subcmd/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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 =20 all: fixdep $(LIBFILE) =20 -$(SUBCMD_IN): FORCE +$(SUBCMD_IN): fixdep FORCE @$(MAKE) $(build)=3Dlibsubcmd =20 $(LIBFILE): $(SUBCMD_IN) --=20 2.45.2.993.g49e7a77208-goog From nobody Wed Dec 17 13:55:40 2025 Received: from mail-pf1-f180.google.com (mail-pf1-f180.google.com [209.85.210.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4EE8013C807 for ; 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charset="utf-8" The 'fixdep' tool is used to post-process dependency files for various reasons, and it runs after every object file generation command. This even includes 'fixdep' itself. In Kbuild, this isn't actually a problem, because it uses a single command to generate fixdep (a compile-and-link command on fixdep.c), and afterward runs the fixdep command on the accompanying .fixdep.cmd file. In tools/ builds (which notably is maintained separately from Kbuild), fixdep is generated in several phases: 1. fixdep.c -> fixdep-in.o 2. fixdep-in.o -> fixdep Thus, fixdep is not available in the post-processing for step 1, and instead, we generate .cmd files that look like: ## from tools/objtool/libsubcmd/.fixdep.o.cmd # cannot find fixdep (/path/to/linux/tools/objtool/libsubcmd//fixdep) [...] These invalid .cmd files are benign in some respects, but cause problems in others (such as the linked reports). Because the tools/ build system is rather complicated in its own right (and pointedly different than Kbuild), I choose to simply open-code the rule for building fixdep, and avoid the recursive-make indirection that produces the problem in the first place. Link: https://lore.kernel.org/all/Zk-C5Eg84yt6_nml@google.com/ Signed-off-by: Brian Norris Acked-by: Jiri Olsa Tested-by: Thorsten Leemhuis --- (no changes since v3) Changes in v3: - Drop unnecessary tools/build/Build tools/build/Build | 3 --- tools/build/Makefile | 11 ++--------- 2 files changed, 2 insertions(+), 12 deletions(-) delete mode 100644 tools/build/Build diff --git a/tools/build/Build b/tools/build/Build deleted file mode 100644 index 76d1a4960973..000000000000 --- a/tools/build/Build +++ /dev/null @@ -1,3 +0,0 @@ -hostprogs :=3D fixdep - -fixdep-y :=3D fixdep.o diff --git a/tools/build/Makefile b/tools/build/Makefile index 17cdf01e29a0..fea3cf647f5b 100644 --- a/tools/build/Makefile +++ b/tools/build/Makefile @@ -43,12 +43,5 @@ ifneq ($(wildcard $(TMP_O)),) $(Q)$(MAKE) -C feature OUTPUT=3D$(TMP_O) clean >/dev/null endif =20 -$(OUTPUT)fixdep-in.o: FORCE - $(Q)$(MAKE) $(build)=3Dfixdep - -$(OUTPUT)fixdep: $(OUTPUT)fixdep-in.o - $(QUIET_LINK)$(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ $< - -FORCE: - -.PHONY: FORCE +$(OUTPUT)fixdep: $(srctree)/tools/build/fixdep.c + $(QUIET_CC)$(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ $< --=20 2.45.2.993.g49e7a77208-goog From nobody Wed Dec 17 13:55:40 2025 Received: from mail-pl1-f175.google.com (mail-pl1-f175.google.com [209.85.214.175]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EF44B13CF8E for ; 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Mon, 15 Jul 2024 13:33:51 -0700 (PDT) Received: from localhost ([2620:15c:9d:2:9b77:1ea5:9de2:19a3]) by smtp.gmail.com with UTF8SMTPSA id d9443c01a7336-1fc0bc2712csm45258775ad.176.2024.07.15.13.33.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Jul 2024 13:33:51 -0700 (PDT) From: Brian Norris To: Arnaldo Carvalho de Melo , Namhyung Kim , Ian Rogers , Thomas Richter , Josh Poimboeuf , Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Masahiro Yamada , bpf@vger.kernel.org, linux-kbuild@vger.kernel.org, Brian Norris , Jiri Olsa Subject: [PATCH v4 3/3] tools build: Correct bpf fixdep dependencies Date: Mon, 15 Jul 2024 13:32:44 -0700 Message-ID: <20240715203325.3832977-4-briannorris@chromium.org> X-Mailer: git-send-email 2.45.2.993.g49e7a77208-goog In-Reply-To: <20240715203325.3832977-1-briannorris@chromium.org> References: <20240715203325.3832977-1-briannorris@chromium.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The dependencies in tools/lib/bpf/Makefile are incorrect. Before we recurse to build $(BPF_IN_STATIC), we need to build its 'fixdep' executable. I can't use the usual shortcut from Makefile.include: : fixdep because its 'fixdep' target relies on $(OUTPUT), and $(OUTPUT) differs in the parent 'make' versus the child 'make' -- so I imitate it via open-coding. I tweak a few $(MAKE) invocations while I'm at it, because 1. I'm adding a new recursive make; and 2. these recursive 'make's print spurious lines about files that are "up to date" (which isn't normally a feature in Kbuild subtargets) or "jobserver not available" (see [1]) I also need to tweak the assignment of the OUTPUT variable, so that relative path builds work. For example, for 'make tools/lib/bpf', OUTPUT is unset, and is usually treated as "cwd" -- but recursive make will change cwd and so OUTPUT has a new meaning. For consistency, I ensure OUTPUT is always an absolute path. And $(Q) gets a backup definition in tools/build/Makefile.include, because Makefile.include is sometimes included without tools/build/Makefile, so the "quiet command" stuff doesn't actually work consistently without it. After this change, top-level builds result in an empty grep result from: $ grep 'cannot find fixdep' $(find tools/ -name '*.cmd') [1] https://www.gnu.org/software/make/manual/html_node/MAKE-Variable.html If we're not using $(MAKE) directly, then we need to use more '+'. Signed-off-by: Brian Norris Acked-by: Jiri Olsa Acked-by: Andrii Nakryiko --- Changes in v4: - update tools/lib/bpf/.gitignore to exclude 'fixdep' - update tools/lib/bpf `make clean` target for fixdep - combine $(SHARED_OBJDIR) and $(STATIC_OBJDIR) rules Changes in v3: - add Jiri's Acked-by Changes in v2: - also fix libbpf shared library rules - ensure OUTPUT is always set, and always an absolute path - add backup $(Q) definition in tools/build/Makefile.include tools/build/Makefile.include | 12 +++++++++++- tools/lib/bpf/.gitignore | 1 + tools/lib/bpf/Makefile | 13 ++++++++++--- 3 files changed, 22 insertions(+), 4 deletions(-) diff --git a/tools/build/Makefile.include b/tools/build/Makefile.include index 8dadaa0fbb43..0e4de83400ac 100644 --- a/tools/build/Makefile.include +++ b/tools/build/Makefile.include @@ -1,8 +1,18 @@ # SPDX-License-Identifier: GPL-2.0-only build :=3D -f $(srctree)/tools/build/Makefile.build dir=3D. obj =20 +# More than just $(Q), we sometimes want to suppress all command output fr= om a +# recursive make -- even the 'up to date' printout. +ifeq ($(V),1) + Q ?=3D + SILENT_MAKE =3D +$(Q)$(MAKE) +else + Q ?=3D @ + SILENT_MAKE =3D +$(Q)$(MAKE) --silent +endif + fixdep: - $(Q)$(MAKE) -C $(srctree)/tools/build CFLAGS=3D LDFLAGS=3D $(OUTPUT)fixdep + $(SILENT_MAKE) -C $(srctree)/tools/build CFLAGS=3D LDFLAGS=3D $(OUTPUT)fi= xdep =20 fixdep-clean: $(Q)$(MAKE) -C $(srctree)/tools/build clean diff --git a/tools/lib/bpf/.gitignore b/tools/lib/bpf/.gitignore index 0da84cb9e66d..f02725b123b3 100644 --- a/tools/lib/bpf/.gitignore +++ b/tools/lib/bpf/.gitignore @@ -5,3 +5,4 @@ TAGS tags cscope.* /bpf_helper_defs.h +fixdep diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile index 2cf892774346..1b22f0f37288 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -108,6 +108,8 @@ MAKEOVERRIDES=3D =20 all: =20 +OUTPUT ?=3D ./ +OUTPUT :=3D $(abspath $(OUTPUT))/ export srctree OUTPUT CC LD CFLAGS V include $(srctree)/tools/build/Makefile.include =20 @@ -141,7 +143,10 @@ all: fixdep =20 all_cmd: $(CMD_TARGETS) check =20 -$(BPF_IN_SHARED): force $(BPF_GENERATED) +$(SHARED_OBJDIR) $(STATIC_OBJDIR): + $(Q)mkdir -p $@ + +$(BPF_IN_SHARED): force $(BPF_GENERATED) | $(SHARED_OBJDIR) @(test -f ../../include/uapi/linux/bpf.h -a -f ../../../include/uapi/linu= x/bpf.h && ( \ (diff -B ../../include/uapi/linux/bpf.h ../../../include/uapi/linux/bpf.h= >/dev/null) || \ echo "Warning: Kernel ABI header at 'tools/include/uapi/linux/bpf.h' diff= ers from latest version at 'include/uapi/linux/bpf.h'" >&2 )) || true @@ -151,9 +156,11 @@ $(BPF_IN_SHARED): force $(BPF_GENERATED) @(test -f ../../include/uapi/linux/if_xdp.h -a -f ../../../include/uapi/l= inux/if_xdp.h && ( \ (diff -B ../../include/uapi/linux/if_xdp.h ../../../include/uapi/linux/if= _xdp.h >/dev/null) || \ echo "Warning: Kernel ABI header at 'tools/include/uapi/linux/if_xdp.h' d= iffers from latest version at 'include/uapi/linux/if_xdp.h'" >&2 )) || true + $(SILENT_MAKE) -C $(srctree)/tools/build CFLAGS=3D LDFLAGS=3D OUTPUT=3D$(= SHARED_OBJDIR) $(SHARED_OBJDIR)fixdep $(Q)$(MAKE) $(build)=3Dlibbpf OUTPUT=3D$(SHARED_OBJDIR) CFLAGS=3D"$(CFLAG= S) $(SHLIB_FLAGS)" =20 -$(BPF_IN_STATIC): force $(BPF_GENERATED) +$(BPF_IN_STATIC): force $(BPF_GENERATED) | $(STATIC_OBJDIR) + $(SILENT_MAKE) -C $(srctree)/tools/build CFLAGS=3D LDFLAGS=3D OUTPUT=3D$(= STATIC_OBJDIR) $(STATIC_OBJDIR)fixdep $(Q)$(MAKE) $(build)=3Dlibbpf OUTPUT=3D$(STATIC_OBJDIR) =20 $(BPF_HELPER_DEFS): $(srctree)/tools/include/uapi/linux/bpf.h @@ -263,7 +270,7 @@ install_pkgconfig: $(PC_FILE) =20 install: install_lib install_pkgconfig install_headers =20 -clean: +clean: fixdep-clean $(call QUIET_CLEAN, libbpf) $(RM) -rf $(CMD_TARGETS) \ *~ .*.d .*.cmd LIBBPF-CFLAGS $(BPF_GENERATED) \ $(SHARED_OBJDIR) $(STATIC_OBJDIR) \ --=20 2.45.2.993.g49e7a77208-goog