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Message-ID: <44914e8a-c8c4-046e-155d-8d893660b417@isovalent.com>
Date: Mon, 13 Feb 2023 20:53:31 +0000
From: Quentin Monnet <quentin@...valent.com>
To: Björn Töpel <bjorn@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
netdev@...r.kernel.org,
Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc: Björn Töpel <bjorn@...osinc.com>,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next] selftests/bpf: Cross-compile bpftool
2023-02-10 09:43 UTC+0100 ~ Björn Töpel <bjorn@...nel.org>
> From: Björn Töpel <bjorn@...osinc.com>
>
> When the BPF selftests are cross-compiled, only the a host version of
> bpftool is built. This version of bpftool is used to generate various
> intermediates, e.g., skeletons.
>
> The test runners are also using bpftool. The Makefile will symlink
> bpftool from the selftest/bpf root, where the test runners will look
> for the tool:
>
> | ...
> | $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \
> | $(OUTPUT)/$(if $2,$2/)bpftool
>
> There are two issues for cross-compilation builds:
>
> 1. There is no native (cross-compilation target) build of bpftool
> 2. The bootstrap variant of bpftool is never cross-compiled (by
> design)
>
> Make sure that a native/cross-compiled version of bpftool is built,
> and if CROSS_COMPILE is set, symlink to the native/non-bootstrap
> version.
>
> Signed-off-by: Björn Töpel <bjorn@...osinc.com>
> ---
> tools/testing/selftests/bpf/Makefile | 28 +++++++++++++++++++++++++---
> 1 file changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index b2eb3201b85a..b706750f71e2 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -157,8 +157,9 @@ $(notdir $(TEST_GEN_PROGS) \
> $(TEST_CUSTOM_PROGS)): %: $(OUTPUT)/% ;
>
> # sort removes libbpf duplicates when not cross-building
> -MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf \
> - $(HOST_BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/resolve_btfids \
> +MAKE_DIRS := $(sort $(BUILD_DIR)/libbpf $(HOST_BUILD_DIR)/libbpf \
> + $(BUILD_DIR)/bpftool $(HOST_BUILD_DIR)/bpftool \
> + $(HOST_BUILD_DIR)/resolve_btfids \
> $(RUNQSLOWER_OUTPUT) $(INCLUDE_DIR))
> $(MAKE_DIRS):
> $(call msg,MKDIR,,$@)
> @@ -208,6 +209,14 @@ $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_tes
> $(Q)cp bpf_testmod/bpf_testmod.ko $@
>
> DEFAULT_BPFTOOL := $(HOST_SCRATCH_DIR)/sbin/bpftool
> +ifneq ($(CROSS_COMPILE),)
> +CROSS_BPFTOOL := $(SCRATCH_DIR)/sbin/bpftool
> +TRUNNER_BPFTOOL := $(CROSS_BPFTOOL)
> +USE_BOOTSTRAP := ""
> +else
> +TRUNNER_BPFTOOL := $(DEFAULT_BPFTOOL)
> +USE_BOOTSTRAP := "bootstrap"
> +endif
>
> $(OUTPUT)/runqslower: $(BPFOBJ) | $(DEFAULT_BPFTOOL) $(RUNQSLOWER_OUTPUT)
> $(Q)$(MAKE) $(submake_extras) -C $(TOOLSDIR)/bpf/runqslower \
> @@ -255,6 +264,18 @@ $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) \
> LIBBPF_DESTDIR=$(HOST_SCRATCH_DIR)/ \
> prefix= DESTDIR=$(HOST_SCRATCH_DIR)/ install-bin
>
> +ifneq ($(CROSS_COMPILE),)
> +$(CROSS_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile) \
> + $(BPFOBJ) | $(BUILD_DIR)/bpftool
> + $(Q)$(MAKE) $(submake_extras) -C $(BPFTOOLDIR) \
> + ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) \
> + EXTRA_CFLAGS='-g -O0' \
> + OUTPUT=$(BUILD_DIR)/bpftool/ \
> + LIBBPF_OUTPUT=$(BUILD_DIR)/libbpf/ \
> + LIBBPF_DESTDIR=$(SCRATCH_DIR)/ \
> + prefix= DESTDIR=$(SCRATCH_DIR)/ install-bin
> +endif
> +
> all: docs
>
> docs:
> @@ -518,11 +539,12 @@ endif
> $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS) \
> $(TRUNNER_EXTRA_OBJS) $$(BPFOBJ) \
> $(RESOLVE_BTFIDS) \
> + $(TRUNNER_BPFTOOL) \
> | $(TRUNNER_BINARY)-extras
> $$(call msg,BINARY,,$$@)
> $(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@
> $(Q)$(RESOLVE_BTFIDS) --btf $(TRUNNER_OUTPUT)/btf_data.bpf.o $$@
> - $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \
> + $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/$(USE_BOOTSTRAP)/bpftool \
Nit: You'll have a double slash in this path when USE_BOOSTRAP is empty
(.../tools/build/bpftool//bpftool), but it probably doesn't matter much.
> $(OUTPUT)/$(if $2,$2/)bpftool
>
> endef
>
> base-commit: 06744f24696e1e7598412c3df61a538b57ebec22
The changes look good to me, thanks!
Acked-by: Quentin Monnet <quentin@...valent.com>
Jean-Philippe, I know you do some cross-compiling with bpftool, how does
this look from your side?
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