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: <target>: <sources> 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 <briannorris@xxxxxxxxxxxx> --- 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/Makefile | 14 ++++++++++++-- 2 files changed, 23 insertions(+), 3 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 := -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) + Q ?= + SILENT_MAKE = +$(Q)$(MAKE) +else + Q ?= @ + 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..630369c0091e 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -108,6 +108,8 @@ MAKEOVERRIDES= all: +OUTPUT ?= ./ +OUTPUT := $(abspath $(OUTPUT))/ export srctree OUTPUT CC LD CFLAGS V include $(srctree)/tools/build/Makefile.include @@ -141,7 +143,13 @@ all: fixdep all_cmd: $(CMD_TARGETS) check -$(BPF_IN_SHARED): force $(BPF_GENERATED) +$(SHARED_OBJDIR): + $(Q)mkdir -p $@ + +$(STATIC_OBJDIR): + $(Q)mkdir -p $@ + +$(BPF_IN_SHARED): force $(BPF_GENERATED) | $(SHARED_OBJDIR) @(test -f ../../include/uapi/linux/bpf.h -a -f ../../../include/uapi/linux/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' differs from latest version at 'include/uapi/linux/bpf.h'" >&2 )) || true @@ -151,9 +159,11 @@ $(BPF_IN_SHARED): force $(BPF_GENERATED) @(test -f ../../include/uapi/linux/if_xdp.h -a -f ../../../include/uapi/linux/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' differs from latest version at 'include/uapi/linux/if_xdp.h'" >&2 )) || true + $(SILENT_MAKE) -C $(srctree)/tools/build CFLAGS= LDFLAGS= OUTPUT=$(SHARED_OBJDIR) $(SHARED_OBJDIR)fixdep $(Q)$(MAKE) $(build)=libbpf OUTPUT=$(SHARED_OBJDIR) CFLAGS="$(CFLAGS) $(SHLIB_FLAGS)" -$(BPF_IN_STATIC): force $(BPF_GENERATED) +$(BPF_IN_STATIC): force $(BPF_GENERATED) | $(STATIC_OBJDIR) + $(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 -- 2.45.2.803.g4e1b14247a-goog
