Re: [PATCH v7 19/22] selftests/liveupdate: add test infrastructure and scripts

[Mike Rapoport <rppt@kernel.org>]

On Sat, Nov 22, 2025 at 05:23:46PM -0500, Pasha Tatashin wrote:
> Subject: [PATCH v7 19/22] selftests/liveupdate: add test infrastructure and scripts

Maybe                                                ^ end to end

> Add the testing infrastructure required to verify the liveupdate
> feature. This includes a custom init process, a test orchestration
> script, and a batch runner.

And say here that it's end to end test.
 
> The framework consists of:
> 
> init.c:
> A lightweight init process that manages the kexec lifecycle.
> It mounts necessary filesystems, determines the current execution
> stage (1 or 2) via the kernel command line, and handles the
> kexec_file_load() sequence to transition between kernels.
> 
> luo_test.sh:
> The primary KTAP-compliant test driver. It handles:
> - Kernel configuration merging and building.
> - Cross-compilation detection for x86_64 and arm64.
> - Generation of the initrd containing the test binary and init.
> - QEMU execution with automatic accelerator detection (KVM, HVF,
>  or TCG).
> 
> run.sh:
> A wrapper script to discover and execute all `luo_*.c`
> tests across supported architectures, providing a summary of
> pass/fail/skip results.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> ---
>  tools/testing/selftests/liveupdate/init.c     | 174 ++++++++++
>  .../testing/selftests/liveupdate/luo_test.sh  | 296 ++++++++++++++++++
>  tools/testing/selftests/liveupdate/run.sh     |  68 ++++
>  3 files changed, 538 insertions(+)
>  create mode 100644 tools/testing/selftests/liveupdate/init.c
>  create mode 100755 tools/testing/selftests/liveupdate/luo_test.sh
>  create mode 100755 tools/testing/selftests/liveupdate/run.sh
> 

...

> +static int is_stage_2(void)
> +{
> +	char cmdline[COMMAND_LINE_SIZE];
> +	ssize_t len;
> +	int fd;
> +
> +	fd = open("/proc/cmdline", O_RDONLY);
> +	if (fd < 0)
> +		return 0;
> +
> +	len = read(fd, cmdline, sizeof(cmdline) - 1);
> +	close(fd);
> +
> +	if (len < 0)
> +		return 0;

Shouldn't we bail out of the test if read of command line failed?

> +
> +	cmdline[len] = 0;
> +
> +	return !!strstr(cmdline, "luo_stage=2");
> +}
> +

...

> +function cleanup() {
> +	local exit_code=$?
> +
> +	if [ -z "$workspace_dir" ]; then
> +		ktap_finished
> +		return
> +	fi
> +
> +	if [ $exit_code -ne 0 ]; then
> +		echo "# Test failed (exit code $exit_code)."
> +		echo "# Workspace preserved at: $workspace_dir"
> +	elif [ "$KEEP_WORKSPACE" -eq 1 ]; then
> +		echo "# Workspace preserved (user request) at: $workspace_dir"
> +	else
> +		rm -fr "$workspace_dir"
> +	fi
> +	ktap_finished

	exit $exit_code

> +}

...

> +function build_kernel() {
> +	local build_dir=$1
> +	local make_cmd=$2
> +	local kimage=$3
> +	local target_arch=$4
> +
> +	local kconfig="$build_dir/.config"
> +	local common_conf="$test_dir/config"
> +	local arch_conf="$test_dir/config.$target_arch"
> +
> +	echo "# Building kernel in: $build_dir"
> +	$make_cmd defconfig
> +
> +	local fragments=""
> +	if [[ -f "$common_conf" ]]; then
> +		fragments="$fragments $common_conf"
> +	fi

Without this CONFIG_LIVEUPDATE won't be set
> +
> +	if [[ -f "$arch_conf" ]]; then
> +		fragments="$fragments $arch_conf"
> +	fi
> +
> +	if [[ -n "$fragments" ]]; then
> +		"$kernel_dir/scripts/kconfig/merge_config.sh" \
> +			-Q -m -O "$build_dir" "$kconfig" $fragments >> /dev/null
> +	fi

I believe you can just

	cat $common_conf $fragments >  $build_dir/.config
	make olddefconfig

without running defconfig at the beginning
It will build faster, just make sure to add CONFIG_SERIAL_ to $arch_conf

> +	$make_cmd olddefconfig
> +	$make_cmd "$kimage"
> +	$make_cmd headers_install INSTALL_HDR_PATH="$headers_dir"
> +}
> +
> +function mkinitrd() {
> +	local build_dir=$1
> +	local kernel_path=$2
> +	local test_name=$3
> +
> +	# 1. Compile the test binary and the init process

Didn't find 2. ;-)
Don't think we want the numbering here, plain comments are fine

> +	"$CROSS_COMPILE"gcc -static -O2 \
> +		-I "$headers_dir/include" \
> +		-I "$test_dir" \
> +		-o "$workspace_dir/test_binary" \
> +		"$test_dir/$test_name.c" "$test_dir/luo_test_utils.c"

This will have hard time cross-compiling with -nolibc toolchains

> +
> +	"$CROSS_COMPILE"gcc -s -static -Os -nostdinc -nostdlib		\
> +			-fno-asynchronous-unwind-tables -fno-ident	\
> +			-fno-stack-protector				\
> +			-I "$headers_dir/include"			\
> +			-I "$kernel_dir/tools/include/nolibc"		\
> +			-o "$workspace_dir/init" "$test_dir/init.c"

This failed for me with gcc 14.2.0 (Debian 14.2.0-19):

/home/mike/git/linux/tools/testing/selftests/liveupdate/init.c: In function ‘run_test’:
/home/mike/git/linux/tools/testing/selftests/liveupdate/init.c:111:65: error: initializer element is not constant
  111 |             static const char *const argv[] = {TEST_BINARY, stage_arg, NULL};
      |                                                             ^~~~~~~~~

/home/mike/git/linux/tools/testing/selftests/liveupdate/init.c:111:65: note: (near initialization for ‘argv[1]’)
/home/mike/git/linux/tools/testing/selftests/liveupdate/init.c:113:37: error: passing argument 2 of ‘execve’ from incompatible pointer type [-Wincompatible-pointer-types]
  113 |                 execve(TEST_BINARY, argv, NULL);
      |                                     ^~~~
      |                                     |
      |                                     const char * const*
In file included from /home/mike/git/linux/tools/testing/selftests/liveupdate/init.c:16:
/usr/include/unistd.h:572:52: note: expected ‘char * const*’ but argument is of type ‘const char * const*’
  572 | extern int execve (const char *__path, char *const __argv[],
      |                                        ~~~~~~~~~~~~^~~~~~~~

> +
> +	cat > "$workspace_dir/cpio_list_inner" <<EOF
> +dir /dev 0755 0 0
> +dir /proc 0755 0 0
> +dir /debugfs 0755 0 0
> +nod /dev/console 0600 0 0 c 5 1

Don't you need /dev/liveupdate node?

> +file /init $workspace_dir/init 0755 0 0
> +file /test_binary $workspace_dir/test_binary 0755 0 0
> +EOF
> +
> +	# Generate inner_initrd.cpio
> +	"$build_dir/usr/gen_init_cpio" "$workspace_dir/cpio_list_inner" > "$workspace_dir/inner_initrd.cpio"
> +
> +	cat > "$workspace_dir/cpio_list" <<EOF
> +dir /dev 0755 0 0
> +dir /proc 0755 0 0
> +dir /debugfs 0755 0 0
> +nod /dev/console 0600 0 0 c 5 1

And here as well.

> +file /init $workspace_dir/init 0755 0 0
> +file /kernel $kernel_path 0644 0 0
> +file /test_binary $workspace_dir/test_binary 0755 0 0
> +file /initrd.img $workspace_dir/inner_initrd.cpio 0644 0 0
> +EOF
> +
> +	# Generate the final initrd
> +	"$build_dir/usr/gen_init_cpio" "$workspace_dir/cpio_list" > "$initrd"
> +	local size=$(du -h "$initrd" | cut -f1)
> +}
> +
> +function run_qemu() {
> +	local qemu_cmd=$1
> +	local cmdline=$2
> +	local kernel_path=$3
> +	local serial="$workspace_dir/qemu.serial"
> +
> +	local accel="-accel tcg"
> +	local host_machine=$(uname -m)
> +
> +	[[ "$host_machine" == "arm64" ]] && host_machine="aarch64"
> +	[[ "$host_machine" == "x86_64" ]] && host_machine="x86_64"
> +
> +	if [[ "$qemu_cmd" == *"$host_machine"* ]]; then
> +		if [ -w /dev/kvm ]; then
> +			accel="-accel kvm"

Just pass both kvm and tcg and let qemu complain.

> +		fi
> +	fi
> +
> +	cmdline="$cmdline liveupdate=on panic=-1"
> +
> +	echo "# Serial Log: $serial"
> +	timeout 30s $qemu_cmd -m 1G -smp 2 -no-reboot -nographic -nodefaults	\
> +		  $accel							\
> +		  -serial file:"$serial"					\
> +		  -append "$cmdline"						\
> +		  -kernel "$kernel_path"					\
> +		  -initrd "$initrd"
> +
> +	local ret=$?
> +
> +	if [ $ret -eq 124 ]; then
> +		fail "QEMU timed out"
> +	fi
> +
> +	grep "TEST PASSED" "$serial" &> /dev/null || fail "Liveupdate failed. Check $serial for details."
> +}

-- 
Sincerely yours,
Mike.