bpf: Helper script for running BPF presubmit tests

The script runs the BPF selftests locally on the same kernel image
as they would run post submit in the BPF continuous integration
framework.

The goal of the script is to allow contributors to run selftests locally
in the same environment to check if their changes would end up breaking
the BPF CI and reduce the back-and-forth between the maintainers and the
developers.
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/bpf/20210204194544.3383814-2-kpsingh@kernel.org

tools/testing/selftests/bpf/vmtest.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+set -u
+set -e
+
+# This script currently only works for x86_64, as
+# it is based on the VM image used by the BPF CI which is
+# x86_64.
+QEMU_BINARY="${QEMU_BINARY:="qemu-system-x86_64"}"
+X86_BZIMAGE="arch/x86/boot/bzImage"
+DEFAULT_COMMAND="./test_progs"
+MOUNT_DIR="mnt"
+ROOTFS_IMAGE="root.img"
+OUTPUT_DIR="$HOME/.bpf_selftests"
+KCONFIG_URL="https://raw.githubusercontent.com/libbpf/libbpf/master/travis-ci/vmtest/configs/latest.config"
+KCONFIG_API_URL="https://api.github.com/repos/libbpf/libbpf/contents/travis-ci/vmtest/configs/latest.config"
+INDEX_URL="https://raw.githubusercontent.com/libbpf/libbpf/master/travis-ci/vmtest/configs/INDEX"
+NUM_COMPILE_JOBS="$(nproc)"
+
+usage()
+{
+	cat <<EOF
+Usage: $0 [-i] [-d <output_dir>] -- [<command>]
+
+<command> is the command you would normally run when you are in
+tools/testing/selftests/bpf. e.g:
+
+	$0 -- ./test_progs -t test_lsm
+
+If no command is specified, "${DEFAULT_COMMAND}" will be run by
+default.
+
+If you build your kernel using KBUILD_OUTPUT= or O= options, these
+can be passed as environment variables to the script:
+
+  O=<kernel_build_path> $0 -- ./test_progs -t test_lsm
+
+or
+
+  KBUILD_OUTPUT=<kernel_build_path> $0 -- ./test_progs -t test_lsm
+
+Options:
+
+	-i)		Update the rootfs image with a newer version.
+	-d)		Update the output directory (default: ${OUTPUT_DIR})
+	-j)		Number of jobs for compilation, similar to -j in make
+			(default: ${NUM_COMPILE_JOBS})
+EOF
+}
+
+unset URLS
+populate_url_map()
+{
+	if ! declare -p URLS &> /dev/null; then
+		# URLS contain the mapping from file names to URLs where
+		# those files can be downloaded from.
+		declare -gA URLS
+		while IFS=$'\t' read -r name url; do
+			URLS["$name"]="$url"
+		done < <(curl -Lsf ${INDEX_URL})
+	fi
+}
+
+download()
+{
+	local file="$1"
+
+	if [[ ! -v URLS[$file] ]]; then
+		echo "$file not found" >&2
+		return 1
+	fi
+
+	echo "Downloading $file..." >&2
+	curl -Lsf "${URLS[$file]}" "${@:2}"
+}
+
+newest_rootfs_version()
+{
+	{
+	for file in "${!URLS[@]}"; do
+		if [[ $file =~ ^libbpf-vmtest-rootfs-(.*)\.tar\.zst$ ]]; then
+			echo "${BASH_REMATCH[1]}"
+		fi
+	done
+	} | sort -rV | head -1
+}
+
+download_rootfs()
+{
+	local rootfsversion="$1"
+	local dir="$2"
+
+	if ! which zstd &> /dev/null; then
+		echo 'Could not find "zstd" on the system, please install zstd'
+		exit 1
+	fi
+
+	download "libbpf-vmtest-rootfs-$rootfsversion.tar.zst" |
+		zstd -d | sudo tar -C "$dir" -x
+}
+
+recompile_kernel()
+{
+	local kernel_checkout="$1"
+	local make_command="$2"
+
+	cd "${kernel_checkout}"
+
+	${make_command} olddefconfig
+	${make_command}
+}
+
+mount_image()
+{
+	local rootfs_img="${OUTPUT_DIR}/${ROOTFS_IMAGE}"
+	local mount_dir="${OUTPUT_DIR}/${MOUNT_DIR}"
+
+	sudo mount -o loop "${rootfs_img}" "${mount_dir}"
+}
+
+unmount_image()
+{
+	local mount_dir="${OUTPUT_DIR}/${MOUNT_DIR}"
+
+	sudo umount "${mount_dir}" &> /dev/null
+}
+
+update_selftests()
+{
+	local kernel_checkout="$1"
+	local selftests_dir="${kernel_checkout}/tools/testing/selftests/bpf"
+
+	cd "${selftests_dir}"
+	${make_command}
+
+	# Mount the image and copy the selftests to the image.
+	mount_image
+	sudo rm -rf "${mount_dir}/root/bpf"
+	sudo cp -r "${selftests_dir}" "${mount_dir}/root"
+	unmount_image
+}
+
+update_init_script()
+{
+	local init_script_dir="${OUTPUT_DIR}/${MOUNT_DIR}/etc/rcS.d"
+	local init_script="${init_script_dir}/S50-startup"
+	local command="$1"
+	local log_file="$2"
+
+	mount_image
+
+	if [[ ! -d "${init_script_dir}" ]]; then
+		cat <<EOF
+Could not find ${init_script_dir} in the mounted image.
+This likely indicates a bad rootfs image, Please download
+a new image by passing "-i" to the script
+EOF
+		exit 1
+
+	fi
+
+	sudo bash -c "cat >${init_script}" <<EOF
+#!/bin/bash
+
+{
+	cd /root/bpf
+	echo ${command}
+	stdbuf -oL -eL ${command}
+} 2>&1 | tee /root/${log_file}
+poweroff -f
+EOF
+
+	sudo chmod a+x "${init_script}"
+	unmount_image
+}
+
+create_vm_image()
+{
+	local rootfs_img="${OUTPUT_DIR}/${ROOTFS_IMAGE}"
+	local mount_dir="${OUTPUT_DIR}/${MOUNT_DIR}"
+
+	rm -rf "${rootfs_img}"
+	touch "${rootfs_img}"
+	chattr +C "${rootfs_img}" >/dev/null 2>&1 || true
+
+	truncate -s 2G "${rootfs_img}"
+	mkfs.ext4 -q "${rootfs_img}"
+
+	mount_image
+	download_rootfs "$(newest_rootfs_version)" "${mount_dir}"
+	unmount_image
+}
+
+run_vm()
+{
+	local kernel_bzimage="$1"
+	local rootfs_img="${OUTPUT_DIR}/${ROOTFS_IMAGE}"
+
+	if ! which "${QEMU_BINARY}" &> /dev/null; then
+		cat <<EOF
+Could not find ${QEMU_BINARY}
+Please install qemu or set the QEMU_BINARY environment variable.
+EOF
+		exit 1
+	fi
+
+	${QEMU_BINARY} \
+		-nodefaults \
+		-display none \
+		-serial mon:stdio \
+		-cpu kvm64 \
+		-enable-kvm \
+		-smp 4 \
+		-m 2G \
+		-drive file="${rootfs_img}",format=raw,index=1,media=disk,if=virtio,cache=none \
+		-kernel "${kernel_bzimage}" \
+		-append "root=/dev/vda rw console=ttyS0,115200"
+}
+
+copy_logs()
+{
+	local mount_dir="${OUTPUT_DIR}/${MOUNT_DIR}"
+	local log_file="${mount_dir}/root/$1"
+
+	mount_image
+	sudo cp ${log_file} "${OUTPUT_DIR}"
+	sudo rm -f ${log_file}
+	unmount_image
+}
+
+is_rel_path()
+{
+	local path="$1"
+
+	[[ ${path:0:1} != "/" ]]
+}
+
+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 "${kconfig_file}")"
+
+		if [[ "${remote_modified_timestamp}" -gt "${local_creation_timestamp}" ]]; then
+			${update_command}
+		fi
+	else
+		${update_command}
+	fi
+}
+
+main()
+{
+	local script_dir="$(cd -P -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd -P)"
+	local kernel_checkout=$(realpath "${script_dir}"/../../../../)
+	local log_file="$(date +"bpf_selftests.%Y-%m-%d_%H-%M-%S.log")"
+	# By default the script searches for the kernel in the checkout directory but
+	# it also obeys environment variables O= and KBUILD_OUTPUT=
+	local kernel_bzimage="${kernel_checkout}/${X86_BZIMAGE}"
+	local command="${DEFAULT_COMMAND}"
+	local update_image="no"
+
+	while getopts 'hkid:j:' opt; do
+		case ${opt} in
+		i)
+			update_image="yes"
+			;;
+		d)
+			OUTPUT_DIR="$OPTARG"
+			;;
+		j)
+			NUM_COMPILE_JOBS="$OPTARG"
+			;;
+		h)
+			usage
+			exit 0
+			;;
+		\? )
+			echo "Invalid Option: -$OPTARG"
+			usage
+			exit 1
+			;;
+		: )
+			echo "Invalid Option: -$OPTARG requires an argument"
+			usage
+			exit 1
+			;;
+		esac
+	done
+	shift $((OPTIND -1))
+
+	if [[ $# -eq 0 ]]; then
+		echo "No command specified, will run ${DEFAULT_COMMAND} in the vm"
+	else
+		command="$@"
+	fi
+
+	local kconfig_file="${OUTPUT_DIR}/latest.config"
+	local make_command="make -j ${NUM_COMPILE_JOBS} KCONFIG_CONFIG=${kconfig_file}"
+
+	# Figure out where the kernel is being built.
+	# O takes precedence over KBUILD_OUTPUT.
+	if [[ "${O:=""}" != "" ]]; then
+		if is_rel_path "${O}"; then
+			O="$(realpath "${PWD}/${O}")"
+		fi
+		kernel_bzimage="${O}/${X86_BZIMAGE}"
+		make_command="${make_command} O=${O}"
+	elif [[ "${KBUILD_OUTPUT:=""}" != "" ]]; then
+		if is_rel_path "${KBUILD_OUTPUT}"; then
+			KBUILD_OUTPUT="$(realpath "${PWD}/${KBUILD_OUTPUT}")"
+		fi
+		kernel_bzimage="${KBUILD_OUTPUT}/${X86_BZIMAGE}"
+		make_command="${make_command} KBUILD_OUTPUT=${KBUILD_OUTPUT}"
+	fi
+
+	populate_url_map
+
+	local rootfs_img="${OUTPUT_DIR}/${ROOTFS_IMAGE}"
+	local mount_dir="${OUTPUT_DIR}/${MOUNT_DIR}"
+
+	echo "Output directory: ${OUTPUT_DIR}"
+
+	mkdir -p "${OUTPUT_DIR}"
+	mkdir -p "${mount_dir}"
+	update_kconfig "${kconfig_file}"
+
+	recompile_kernel "${kernel_checkout}" "${make_command}"
+
+	if [[ "${update_image}" == "no" && ! -f "${rootfs_img}" ]]; then
+		echo "rootfs image not found in ${rootfs_img}"
+		update_image="yes"
+	fi
+
+	if [[ "${update_image}" == "yes" ]]; then
+		create_vm_image
+	fi
+
+	update_selftests "${kernel_checkout}" "${make_command}"
+	update_init_script "${command}" "${log_file}"
+	run_vm "${kernel_bzimage}"
+	copy_logs "${log_file}"
+	echo "Logs saved in ${OUTPUT_DIR}/${log_file}"
+}
+
+catch()
+{
+	local exit_code=$1
+	# This is just a cleanup and the directory may
+	# have already been unmounted. So, don't let this
+	# clobber the error code we intend to return.
+	unmount_image || true
+	exit ${exit_code}
+}
+
+trap 'catch "$?"' EXIT
+
+main "$@"