selftests/bpf: Adjust vmtest.sh to use local kernel configuration

So far the vmtest.sh script, which can be used as a convenient way to
run bpf selftests, has obtained the kernel config safe to use for
testing from the libbpf/libbpf GitHub repository [0].

Given that we now have included this configuration into this very
repository, we can just consume it from here as well, eliminating the
necessity of remote accesses.

With this change we adjust the logic in the script to use the
configuration from below tools/testing/selftests/bpf/configs/ instead
of pulling it over the network.

[0] https://github.com/libbpf/libbpf

Signed-off-by: Daniel Müller <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Martin KaFai Lau <[e-mail]>
Acked-by: Mykola Lysenko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/testing/selftests/bpf/vmtest.sh

···
 MOUNT_DIR="mnt"
 ROOTFS_IMAGE="root.img"
 OUTPUT_DIR="$HOME/.bpf_selftests"
-KCONFIG_URL="https://raw.githubusercontent.com/libbpf/libbpf/master/travis-ci/vmtest/configs/config-latest.${ARCH}"
-KCONFIG_API_URL="https://api.github.com/repos/libbpf/libbpf/contents/travis-ci/vmtest/configs/config-latest.${ARCH}"
+KCONFIG_REL_PATHS=("tools/testing/selftests/bpf/config" "tools/testing/selftests/bpf/config.${ARCH}")
 INDEX_URL="https://raw.githubusercontent.com/libbpf/ci/master/INDEX"
 NUM_COMPILE_JOBS="$(nproc)"
 LOG_FILE_BASE="$(date +"bpf_selftests.%Y-%m-%d_%H-%M-%S")"
···
 	[[ ${path:0:1} != "/" ]]
 }
 
+do_update_kconfig()
+{
+	local kernel_checkout="$1"
+	local kconfig_file="$2"
+
+	rm -f "$kconfig_file" 2> /dev/null
+
+	for config in "${KCONFIG_REL_PATHS[@]}"; do
+		local kconfig_src="${kernel_checkout}/${config}"
+		cat "$kconfig_src" >> "$kconfig_file"
+	done
+}
+
 update_kconfig()
 {
-	local kconfig_file="$1"
-	local update_command="curl -sLf ${KCONFIG_URL} -o ${kconfig_file}"
-	# Github does not return the "last-modified" header when retrieving the
-	# raw contents of the file. Use the API call to get the last-modified
-	# time of the kernel config and only update the config if it has been
-	# updated after the previously cached config was created. This avoids
-	# unnecessarily compiling the kernel and selftests.
-	if [[ -f "${kconfig_file}" ]]; then
-		local last_modified_date="$(curl -sL -D - "${KCONFIG_API_URL}" -o /dev/null | \
-			grep "last-modified" | awk -F ': ' '{print $2}')"
-		local remote_modified_timestamp="$(date -d "${last_modified_date}" +"%s")"
-		local local_creation_timestamp="$(stat -c %Y "${kconfig_file}")"
+	local kernel_checkout="$1"
+	local kconfig_file="$2"
 
-		if [[ "${remote_modified_timestamp}" -gt "${local_creation_timestamp}" ]]; then
-			${update_command}
-		fi
+	if [[ -f "${kconfig_file}" ]]; then
+		local local_modified="$(stat -c %Y "${kconfig_file}")"
+
+		for config in "${KCONFIG_REL_PATHS[@]}"; do
+			local kconfig_src="${kernel_checkout}/${config}"
+			local src_modified="$(stat -c %Y "${kconfig_src}")"
+			# Only update the config if it has been updated after the
+			# previously cached config was created. This avoids
+			# unnecessarily compiling the kernel and selftests.
+			if [[ "${src_modified}" -gt "${local_modified}" ]]; then
+				do_update_kconfig "$kernel_checkout" "$kconfig_file"
+				# Once we have found one outdated configuration
+				# there is no need to check other ones.
+				break
+			fi
+		done
 	else
-		${update_command}
+		do_update_kconfig "$kernel_checkout" "$kconfig_file"
 	fi
 }
 
···
 
 	mkdir -p "${OUTPUT_DIR}"
 	mkdir -p "${mount_dir}"
-	update_kconfig "${kconfig_file}"
+	update_kconfig "${kernel_checkout}" "${kconfig_file}"
 
 	recompile_kernel "${kernel_checkout}" "${make_command}"