initial buildroot for linux 5.15

package/libbpf/Config.in

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+config BR2_PACKAGE_LIBBPF_ARCH_SUPPORTS
+	bool
+	# see src/bpf.c
+	default y if BR2_arc
+	default y if BR2_aarch64 || BR2_aarch64_be
+	default y if BR2_i386 || BR2_x86_64
+	default y if BR2_sparc || BR2_sparc64
+	default y if BR2_s390x
+
+config BR2_PACKAGE_LIBBPF
+	bool "libbpf"
+	depends on BR2_PACKAGE_LIBBPF_ARCH_SUPPORTS
+	depends on BR2_USE_WCHAR # elfutils
+	depends on !BR2_STATIC_LIBS # elfutils
+	depends on BR2_TOOLCHAIN_HAS_THREADS # elfutils
+	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_13
+	depends on BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC # elfutils
+	select BR2_PACKAGE_ELFUTILS
+	select BR2_PACKAGE_ZLIB
+	help
+	  libbpf library.
+	  A mirror of bpf-next linux tree bpf-next/tools/lib/bpf
+	  directory plus its supporting header files. The version
+	  of the package reflects the version of ABI.
+
+	  https://github.com/libbpf/libbpf
+
+comment "libbpf needs a uClibc or glibc toolchain w/ wchar, dynamic library, threads, headers >= 4.13"
+	depends on BR2_PACKAGE_LIBBPF_ARCH_SUPPORTS
+	depends on !BR2_USE_WCHAR || BR2_STATIC_LIBS \
+		|| !BR2_TOOLCHAIN_HAS_THREADS \
+		|| !BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_13 \
+		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC)

package/libbpf/libbpf.hash

@@ -0,0 +1,5 @@
+# Locally calculated
+sha256  21cbee4df093e7fd29e76ed429650d3f3abe3a893f35e346ab9bc3484f6e68c0  libbpf-0.4.0.tar.gz
+sha256  847f4addbd56e2d5be20c4ea0845e972672fc07b755fadaae5f7abd35d71e349  LICENSE
+sha256  6313108c23efffa36948f8b2cff1560a5935373b527b0e1a837cc77e6ed1bacd  LICENSE.BSD-2-Clause
+sha256  0b9a4febcdee6de55872501d5c1a8f5d8b0d1650cd4d5351995ceb22e889f8ca  LICENSE.LGPL-2.1

package/libbpf/libbpf.mk

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+################################################################################
+#
+# libbpf
+#
+################################################################################
+
+LIBBPF_VERSION = 0.4.0
+LIBBPF_SITE = $(call github,libbpf,libbpf,v$(LIBBPF_VERSION))
+LIBBPF_LICENSE = GPL-2.0, LGPL-2.1, BSD-2-Clause
+LIBBPF_LICENSE_FILES = LICENSE LICENSE.BSD-2-Clause LICENSE.LGPL-2.1
+LIBBPF_DEPENDENCIES = host-bison host-flex host-pkgconf elfutils zlib
+LIBBPF_INSTALL_STAGING = YES
+
+define LIBBPF_BUILD_CMDS
+	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) \
+		-C $(@D)/src
+endef
+
+# bpf/bpf.h installed by libbpf uses bpf_iter_link_info that was added since
+# kernel 5.9, so we need to update some uapi headers in STAGING_DIR if the
+# toolchain is build with linux-headers < 5.9.
+# Otherwise bpf/bpf.h is broken due to out of date linux/bpf.h installed by the
+# toolchain.
+# https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a5cbe05a6673b85bed2a63ffcfea6a96c6410cff
+ifeq ($(BR2_TOOLCHAIN_HEADERS_AT_LEAST_5_9),)
+LIBBPF_UPDATE_UAPI_HEADERS = install_uapi_headers
+endif
+
+define LIBBPF_INSTALL_STAGING_CMDS
+	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) \
+		-C $(@D)/src install $(LIBBPF_UPDATE_UAPI_HEADERS) \
+		DESTDIR=$(STAGING_DIR)
+endef
+
+define LIBBPF_INSTALL_TARGET_CMDS
+	$(TARGET_MAKE_ENV) $(TARGET_CONFIGURE_OPTS) $(MAKE) \
+		-C $(@D)/src install DESTDIR=$(TARGET_DIR)
+endef
+
+$(eval $(generic-package))