Messages in this thread | | | Subject | Re: [PATCH bpf-next] samples: bpf: Fix cross-compiling error about bpftool | From | Pu Lehui <> | Date | Fri, 8 Jul 2022 10:46:21 +0800 |
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On 2022/7/8 3:12, Song Liu wrote: > > >> On Jul 7, 2022, at 7:08 AM, Pu Lehui <pulehui@huawei.com> wrote: >> >> Currently, when cross compiling bpf samples, the host side >> cannot use arch-specific bpftool to generate vmlinux.h or >> skeleton. We need to compile the bpftool with the host >> compiler. >> >> Signed-off-by: Pu Lehui <pulehui@huawei.com> >> --- >> samples/bpf/Makefile | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile >> index 5002a5b9a7da..fe54a8c8f312 100644 >> --- a/samples/bpf/Makefile >> +++ b/samples/bpf/Makefile >> @@ -1,4 +1,5 @@ >> # SPDX-License-Identifier: GPL-2.0 >> +-include tools/scripts/Makefile.include > > Why do we need the -include here? >
HOSTLD is defined in tools/scripts/Makefile.include, we need to add it.
And for -include, mainly to resolve some conflicts: 1. If workdir is kernel_src, then 'include tools/scripts/Makefile.include' is fine when 'make M=samples/bpf'. 2. Since the trick in samples/bpf/Makefile:
# Trick to allow make to be run from this directory all: $(MAKE) -C ../../ M=$(CURDIR) BPF_SAMPLES_PATH=$(CURDIR)
If workdir is samples/bpf, the compile process will first load the Makefile in samples/bpf, then change workdir to kernel_src and load the kernel_src's Makefile. So if we just add 'include tools/scripts/Makefile.include', then the first load will occur error for not found the file, so we add -include to skip the first load.
> Thanks, > Song > >> >> BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src)) >> TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools >> @@ -283,11 +284,10 @@ $(LIBBPF): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU >> BPFTOOLDIR := $(TOOLS_PATH)/bpf/bpftool >> BPFTOOL_OUTPUT := $(abspath $(BPF_SAMPLES_PATH))/bpftool >> BPFTOOL := $(BPFTOOL_OUTPUT)/bpftool >> -$(BPFTOOL): $(LIBBPF) $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT) >> +$(BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) | $(BPFTOOL_OUTPUT) >> $(MAKE) -C $(BPFTOOLDIR) srctree=$(BPF_SAMPLES_PATH)/../../ \ >> - OUTPUT=$(BPFTOOL_OUTPUT)/ \ >> - LIBBPF_OUTPUT=$(LIBBPF_OUTPUT)/ \ >> - LIBBPF_DESTDIR=$(LIBBPF_DESTDIR)/ >> + ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) \ >> + OUTPUT=$(BPFTOOL_OUTPUT)/ >> >> $(LIBBPF_OUTPUT) $(BPFTOOL_OUTPUT): >> $(call msg,MKDIR,$@) >> -- >> 2.25.1 >> > > . >
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