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 11:12:33 +0800 |
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On 2022/7/8 10:46, Pu Lehui wrote: > > > 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.
sorry, correct the reply, so we add -include to skip the 'tools/scripts/Makefile.include' file on the fisrt 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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