[Buildroot] [PATCH] package/bpftool: add a patch to fix cross compilation

[Arnout Vandecappelle]

On 10/06/2022 15:33, Shahab Vahedi via buildroot wrote:
> If on the host machine the "co-re" is supported, bpftool will
> build a bootstrap version of itself as well. In that case, the
> cross compilation can fail. This commit adds a patch to remedy
> that. The fix that you see here is already upsteamed [1].
> 
> [1]
> https://lore.kernel.org/bpf/165477661272.11342.13015777410417612477.git-patchwork-notify@kernel.org/T/#t
> 
> Signed-off-by: Shahab Vahedi <shahab at synopsys.com>
> ---
>   package/bpftool/0001-fix-bootsrap.patch | 32 +++++++++++++++++++++++++
>   1 file changed, 32 insertions(+)
>   create mode 100644 package/bpftool/0001-fix-bootsrap.patch
> 
> diff --git a/package/bpftool/0001-fix-bootsrap.patch b/package/bpftool/0001-fix-bootsrap.patch
> new file mode 100644
> index 0000000000..03f4231cca
> --- /dev/null
> +++ b/package/bpftool/0001-fix-bootsrap.patch
> @@ -0,0 +1,32 @@
> +This is an adapted version of an upstreamed patch [1], else it won't be
> +possible to cross compile bpftool if "clang-bpf-co-re" feature is enabled.
> +
> +[1] bpftool: Fix bootstrapping during a cross compilation
> +https://lore.kernel.org/bpf/8d297f0c-cfd0-ef6f-3970-6dddb3d9a87a@synopsys.com/t/#u

  The patch file should be git-formatted and have your Signed-off-by. I simply 
took the patch from [1] (which has your signoff) and added the additional 
Makefile.include changes (of which I don't really understand BTW why they're 
relevant for Buildroot).


  Regards,
  Arnout

[1] 
https://github.com/libbpf/bpftool/commit/189f777ea4829bede0bf92f572c22fe1f2c37522


> +--- bpftool-v6.8.0/src/Makefile
> ++++ bpftool-v6.8.0/src/Makefile
> +@@ -51,7 +51,7 @@
> + $(LIBBPF_BOOTSTRAP): $(wildcard $(BPF_DIR)/*.[ch] $(BPF_DIR)/Makefile) | $(LIBBPF_BOOTSTRAP_OUTPUT)
> + 	$(Q)$(MAKE) -C $(BPF_DIR) OBJDIR=$(patsubst %/,%,$(LIBBPF_BOOTSTRAP_OUTPUT)) \
> + 		PREFIX=$(LIBBPF_BOOTSTRAP_DESTDIR:/=) \
> +-		ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) $@ install_headers
> ++		ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD) AR=$(HOSTAR) $@ install_headers
> +
> + $(LIBBPF_BOOTSTRAP_INTERNAL_HDRS): $(LIBBPF_BOOTSTRAP_HDRS_DIR)/%.h: $(BPF_DIR)/%.h | $(LIBBPF_BOOTSTRAP_HDRS_DIR)
> + 	$(call QUIET_INSTALL, $@)
> +--- bpftool-v6.8.0/src/Makefile.include
> ++++ bpftool-v6.8.0/src/Makefile.include
> +@@ -12,11 +12,13 @@
> + ifneq ($(LLVM),)
> +   $(if $(findstring default,$(origin CC)),$(eval CC := clang$(LLVM_VERSION)))
> +   $(if $(findstring default,$(origin LD)),$(eval LD := ld.lld$(LLVM_VERSION)))
> ++  HOSTAR ?= llvm-ar
> +   HOSTCC ?= clang
> +   HOSTLD ?= ld.lld
> + else
> +   $(if $(findstring default,$(origin CC)),$(eval CC = $(CROSS_COMPILE)$(CC)))
> +   $(if $(findstring default,$(origin LD)),$(eval LD = $(CROSS_COMPILE)$(LD)))
> ++  HOSTAR ?= ar
> +   HOSTCC ?= gcc
> +   HOSTLD ?= ld
> + endif
> 
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