Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1568 insertions, 0 deletions

diff --git a/src/sysext/sysext.c b/src/sysext/sysext.c
new file mode 100644
index 0000000..8dc515e
--- /dev/null
+++ b/src/sysext/sysext.c
@@ -0,0 +1,1568 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+#include <getopt.h>
+#include <linux/loop.h>
+#include <sys/file.h>
+#include <sys/mount.h>
+#include <unistd.h>
+
+#include "sd-bus.h"
+
+#include "build.h"
+#include "bus-locator.h"
+#include "bus-error.h"
+#include "bus-unit-util.h"
+#include "bus-util.h"
+#include "capability-util.h"
+#include "chase.h"
+#include "constants.h"
+#include "devnum-util.h"
+#include "discover-image.h"
+#include "dissect-image.h"
+#include "env-util.h"
+#include "escape.h"
+#include "extension-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "format-table.h"
+#include "fs-util.h"
+#include "hashmap.h"
+#include "initrd-util.h"
+#include "log.h"
+#include "main-func.h"
+#include "missing_magic.h"
+#include "mkdir.h"
+#include "mount-util.h"
+#include "mountpoint-util.h"
+#include "os-util.h"
+#include "pager.h"
+#include "parse-argument.h"
+#include "parse-util.h"
+#include "pretty-print.h"
+#include "process-util.h"
+#include "sort-util.h"
+#include "terminal-util.h"
+#include "user-util.h"
+#include "varlink.h"
+#include "varlink-io.systemd.sysext.h"
+#include "verbs.h"
+
+static char **arg_hierarchies = NULL; /* "/usr" + "/opt" by default for sysext and /etc by default for confext */
+static char *arg_root = NULL;
+static JsonFormatFlags arg_json_format_flags = JSON_FORMAT_OFF;
+static PagerFlags arg_pager_flags = 0;
+static bool arg_legend = true;
+static bool arg_force = false;
+static bool arg_no_reload = false;
+static int arg_noexec = -1;
+static ImagePolicy *arg_image_policy = NULL;
+static bool arg_varlink = false;
+
+/* Is set to IMAGE_CONFEXT when systemd is called with the confext functionality instead of the default */
+static ImageClass arg_image_class = IMAGE_SYSEXT;
+
+STATIC_DESTRUCTOR_REGISTER(arg_hierarchies, strv_freep);
+STATIC_DESTRUCTOR_REGISTER(arg_root, freep);
+STATIC_DESTRUCTOR_REGISTER(arg_image_policy, image_policy_freep);
+
+/* Helper struct for naming simplicity and reusability */
+static const struct {
+        const char *dot_directory_name;
+        const char *directory_name;
+        const char *short_identifier;
+        const char *short_identifier_plural;
+        const char *level_env;
+        const char *scope_env;
+        const char *name_env;
+        const ImagePolicy *default_image_policy;
+        unsigned long default_mount_flags;
+} image_class_info[_IMAGE_CLASS_MAX] = {
+        [IMAGE_SYSEXT] = {
+                .dot_directory_name = ".systemd-sysext",
+                .directory_name = "systemd-sysext",
+                .short_identifier = "sysext",
+                .short_identifier_plural = "extensions",
+                .level_env = "SYSEXT_LEVEL",
+                .scope_env = "SYSEXT_SCOPE",
+                .name_env = "SYSTEMD_SYSEXT_HIERARCHIES",
+                .default_image_policy = &image_policy_sysext,
+                .default_mount_flags = MS_RDONLY|MS_NODEV,
+        },
+        [IMAGE_CONFEXT] = {
+                .dot_directory_name = ".systemd-confext",
+                .directory_name = "systemd-confext",
+                .short_identifier = "confext",
+                .short_identifier_plural = "confexts",
+                .level_env = "CONFEXT_LEVEL",
+                .scope_env = "CONFEXT_SCOPE",
+                .name_env = "SYSTEMD_CONFEXT_HIERARCHIES",
+                .default_image_policy = &image_policy_confext,
+                .default_mount_flags = MS_RDONLY|MS_NODEV|MS_NOSUID|MS_NOEXEC,
+        }
+};
+
+static int is_our_mount_point(
+                ImageClass image_class,
+                const char *p) {
+
+        _cleanup_free_ char *buf = NULL, *f = NULL;
+        struct stat st;
+        dev_t dev;
+        int r;
+
+        assert(p);
+
+        r = path_is_mount_point(p, NULL, 0);
+        if (r == -ENOENT) {
+                log_debug_errno(r, "Hierarchy '%s' doesn't exist.", p);
+                return false;
+        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine whether '%s' is a mount point: %m", p);
+        if (r == 0) {
+                log_debug("Hierarchy '%s' is not a mount point, skipping.", p);
+                return false;
+        }
+
+        /* So we know now that it's a mount point. Now let's check if it's one of ours, so that we don't
+         * accidentally unmount the user's own /usr/ but just the mounts we established ourselves. We do this
+         * check by looking into the metadata directory we place in merged mounts: if the file
+         * ../dev contains the major/minor device pair of the mount we have a good reason to
+         * believe this is one of our mounts. This thorough check has the benefit that we aren't easily
+         * confused if people tar up one of our merged trees and untar them elsewhere where we might mistake
+         * them for a live sysext tree. */
+
+        f = path_join(p, image_class_info[image_class].dot_directory_name, "dev");
+        if (!f)
+                return log_oom();
+
+        r = read_one_line_file(f, &buf);
+        if (r == -ENOENT) {
+                log_debug("Hierarchy '%s' does not carry a %s/dev file, not a merged tree.", p, image_class_info[image_class].dot_directory_name);
+                return false;
+        }
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine whether hierarchy '%s' contains '%s/dev': %m", p, image_class_info[image_class].dot_directory_name);
+
+        r = parse_devnum(buf, &dev);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse device major/minor stored in '%s/dev' file on '%s': %m", image_class_info[image_class].dot_directory_name, p);
+
+        if (lstat(p, &st) < 0)
+                return log_error_errno(r, "Failed to stat %s: %m", p);
+
+        if (st.st_dev != dev) {
+                log_debug("Hierarchy '%s' reports a different device major/minor than what we are seeing, assuming offline copy.", p);
+                return false;
+        }
+
+        return true;
+}
+
+static int need_reload(
+                ImageClass image_class,
+                char **hierarchies,
+                bool no_reload) {
+
+        /* Parse the mounted images to find out if we need to reload the daemon. */
+        int r;
+
+        if (no_reload)
+                return false;
+
+        STRV_FOREACH(p, hierarchies) {
+                _cleanup_free_ char *f = NULL, *buf = NULL, *resolved = NULL;
+                _cleanup_strv_free_ char **mounted_extensions = NULL;
+
+                r = chase(*p, arg_root, CHASE_PREFIX_ROOT, &resolved, NULL);
+                if (r == -ENOENT) {
+                        log_debug_errno(r, "Hierarchy '%s%s' does not exist, ignoring.", strempty(arg_root), *p);
+                        continue;
+                }
+                if (r < 0) {
+                        log_warning_errno(r, "Failed to resolve path to hierarchy '%s%s': %m, ignoring.", strempty(arg_root), *p);
+                        continue;
+                }
+
+                r = is_our_mount_point(image_class, resolved);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        continue;
+
+                f = path_join(resolved, image_class_info[image_class].dot_directory_name, image_class_info[image_class].short_identifier_plural);
+                if (!f)
+                        return log_oom();
+
+                r = read_full_file(f, &buf, NULL);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to open '%s': %m", f);
+
+                mounted_extensions = strv_split_newlines(buf);
+                if (!mounted_extensions)
+                        return log_oom();
+
+                STRV_FOREACH(extension, mounted_extensions) {
+                        _cleanup_strv_free_ char **extension_release = NULL;
+                        const char *extension_reload_manager = NULL;
+                        int b;
+
+                        r = load_extension_release_pairs(arg_root, image_class, *extension, /* relax_extension_release_check */ true, &extension_release);
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to parse extension-release metadata of %s, ignoring: %m", *extension);
+                                continue;
+                        }
+
+                        extension_reload_manager = strv_env_pairs_get(extension_release, "EXTENSION_RELOAD_MANAGER");
+                        if (isempty(extension_reload_manager))
+                                continue;
+
+                        b = parse_boolean(extension_reload_manager);
+                        if (b < 0) {
+                                log_warning_errno(b, "Failed to parse the extension metadata to know if the manager needs to be reloaded, ignoring: %m");
+                                continue;
+                        }
+
+                        if (b)
+                                /* If at least one extension wants a reload, we reload. */
+                                return true;
+                }
+        }
+
+        return false;
+}
+
+static int daemon_reload(void) {
+         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+        int r;
+
+        r = bus_connect_system_systemd(&bus);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get D-Bus connection: %m");
+
+        return bus_service_manager_reload(bus);
+}
+
+static int unmerge_hierarchy(
+                ImageClass image_class,
+                const char *p) {
+
+        int r;
+
+        assert(p);
+
+        for (;;) {
+                /* We only unmount /usr/ if it is a mount point and really one of ours, in order not to break
+                 * systems where /usr/ is a mount point of its own already. */
+
+                r = is_our_mount_point(image_class, p);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                r = umount_verbose(LOG_ERR, p, MNT_DETACH|UMOUNT_NOFOLLOW);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to unmount file system '%s': %m", p);
+
+                log_info("Unmerged '%s'.", p);
+        }
+
+        return 0;
+}
+
+static int unmerge(
+                ImageClass image_class,
+                char **hierarchies,
+                bool no_reload) {
+
+        int r, ret = 0;
+        bool need_to_reload;
+
+        r = need_reload(image_class, hierarchies, no_reload);
+        if (r < 0)
+                return r;
+        need_to_reload = r > 0;
+
+        STRV_FOREACH(p, hierarchies) {
+                _cleanup_free_ char *resolved = NULL;
+
+                r = chase(*p, arg_root, CHASE_PREFIX_ROOT, &resolved, NULL);
+                if (r == -ENOENT) {
+                        log_debug_errno(r, "Hierarchy '%s%s' does not exist, ignoring.", strempty(arg_root), *p);
+                        continue;
+                }
+                if (r < 0) {
+                        log_error_errno(r, "Failed to resolve path to hierarchy '%s%s': %m", strempty(arg_root), *p);
+                        if (ret == 0)
+                                ret = r;
+
+                        continue;
+                }
+
+                r = unmerge_hierarchy(image_class, resolved);
+                if (r < 0 && ret == 0)
+                        ret = r;
+        }
+
+        if (need_to_reload) {
+                r = daemon_reload();
+                if (r < 0)
+                        return r;
+        }
+
+        return ret;
+}
+
+static int verb_unmerge(int argc, char **argv, void *userdata) {
+        int r;
+
+        r = have_effective_cap(CAP_SYS_ADMIN);
+        if (r < 0)
+                return log_error_errno(r, "Failed to check if we have enough privileges: %m");
+        if (r == 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be privileged.");
+
+        return unmerge(arg_image_class,
+                       arg_hierarchies,
+                       arg_no_reload);
+}
+
+static int parse_image_class_parameter(Varlink *link, const char *value, ImageClass *image_class, char ***hierarchies) {
+        _cleanup_strv_free_ char **h = NULL;
+        ImageClass c;
+        int r;
+
+        assert(link);
+        assert(image_class);
+
+        if (!value)
+                return 0;
+
+        c = image_class_from_string(value);
+        if (!IN_SET(c, IMAGE_SYSEXT, IMAGE_CONFEXT))
+                return varlink_errorb(link, VARLINK_ERROR_INVALID_PARAMETER, JSON_BUILD_OBJECT(JSON_BUILD_PAIR_STRING("parameter", "class")));
+
+        if (hierarchies) {
+                r = parse_env_extension_hierarchies(&h, image_class_info[c].name_env);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to parse environment variable: %m");
+
+                strv_free_and_replace(*hierarchies, h);
+        }
+
+        *image_class = c;
+        return 0;
+}
+
+typedef struct MethodUnmergeParameters {
+        const char *class;
+        int no_reload;
+} MethodUnmergeParameters;
+
+static int vl_method_unmerge(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {
+
+        static const JsonDispatch dispatch_table[] = {
+                { "class",    JSON_VARIANT_STRING,  json_dispatch_const_string, offsetof(MethodUnmergeParameters, class),     0 },
+                { "noReload", JSON_VARIANT_BOOLEAN, json_dispatch_boolean,      offsetof(MethodUnmergeParameters, no_reload), 0 },
+                {}
+        };
+        MethodUnmergeParameters p = {
+                .no_reload = -1,
+        };
+        _cleanup_strv_free_ char **hierarchies = NULL;
+        ImageClass image_class = arg_image_class;
+        int r;
+
+        assert(link);
+
+        r = varlink_dispatch(link, parameters, dispatch_table, &p);
+        if (r != 0)
+                return r;
+
+        r = parse_image_class_parameter(link, p.class, &image_class, &hierarchies);
+        if (r < 0)
+                return r;
+
+        r = unmerge(image_class,
+                    hierarchies ?: arg_hierarchies,
+                    p.no_reload >= 0 ? p.no_reload : arg_no_reload);
+        if (r < 0)
+                return r;
+
+        return varlink_reply(link, NULL);
+}
+
+static int verb_status(int argc, char **argv, void *userdata) {
+        _cleanup_(table_unrefp) Table *t = NULL;
+        int r, ret = 0;
+
+        t = table_new("hierarchy", "extensions", "since");
+        if (!t)
+                return log_oom();
+
+        table_set_ersatz_string(t, TABLE_ERSATZ_DASH);
+
+        STRV_FOREACH(p, arg_hierarchies) {
+                _cleanup_free_ char *resolved = NULL, *f = NULL, *buf = NULL;
+                _cleanup_strv_free_ char **l = NULL;
+                struct stat st;
+
+                r = chase(*p, arg_root, CHASE_PREFIX_ROOT, &resolved, NULL);
+                if (r == -ENOENT) {
+                        log_debug_errno(r, "Hierarchy '%s%s' does not exist, ignoring.", strempty(arg_root), *p);
+                        continue;
+                }
+                if (r < 0) {
+                        log_error_errno(r, "Failed to resolve path to hierarchy '%s%s': %m", strempty(arg_root), *p);
+                        goto inner_fail;
+                }
+
+                r = is_our_mount_point(arg_image_class, resolved);
+                if (r < 0)
+                        goto inner_fail;
+                if (r == 0) {
+                        r = table_add_many(
+                                        t,
+                                        TABLE_PATH, *p,
+                                        TABLE_STRING, "none",
+                                        TABLE_SET_COLOR, ansi_grey(),
+                                        TABLE_EMPTY);
+                        if (r < 0)
+                                return table_log_add_error(r);
+
+                        continue;
+                }
+
+                f = path_join(resolved, image_class_info[arg_image_class].dot_directory_name, image_class_info[arg_image_class].short_identifier_plural);
+                if (!f)
+                        return log_oom();
+
+                r = read_full_file(f, &buf, NULL);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to open '%s': %m", f);
+
+                l = strv_split_newlines(buf);
+                if (!l)
+                        return log_oom();
+
+                if (stat(*p, &st) < 0)
+                        return log_error_errno(r, "Failed to stat() '%s': %m", *p);
+
+                r = table_add_many(
+                                t,
+                                TABLE_PATH, *p,
+                                TABLE_STRV, l,
+                                TABLE_TIMESTAMP, timespec_load(&st.st_mtim));
+                if (r < 0)
+                        return table_log_add_error(r);
+
+                continue;
+
+        inner_fail:
+                if (ret == 0)
+                        ret = r;
+        }
+
+        (void) table_set_sort(t, (size_t) 0);
+
+        r = table_print_with_pager(t, arg_json_format_flags, arg_pager_flags, arg_legend);
+        if (r < 0)
+                return r;
+
+        return ret;
+}
+
+static int mount_overlayfs(
+                ImageClass image_class,
+                int noexec,
+                const char *where,
+                char **layers) {
+
+        _cleanup_free_ char *options = NULL;
+        bool separator = false;
+        unsigned long flags;
+        int r;
+
+        assert(where);
+
+        options = strdup("lowerdir=");
+        if (!options)
+                return log_oom();
+
+        STRV_FOREACH(l, layers) {
+                _cleanup_free_ char *escaped = NULL;
+
+                escaped = shell_escape(*l, ",:");
+                if (!escaped)
+                        return log_oom();
+
+                if (!strextend(&options, separator ? ":" : "", escaped))
+                        return log_oom();
+
+                separator = true;
+        }
+
+        flags = image_class_info[image_class].default_mount_flags;
+        if (noexec >= 0)
+                SET_FLAG(flags, MS_NOEXEC, noexec);
+
+        /* Now mount the actual overlayfs */
+        r = mount_nofollow_verbose(LOG_ERR, image_class_info[image_class].short_identifier, where, "overlay", flags, options);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int merge_hierarchy(
+                ImageClass image_class,
+                const char *hierarchy,
+                int noexec,
+                char **extensions,
+                char **paths,
+                const char *meta_path,
+                const char *overlay_path) {
+
+        _cleanup_free_ char *resolved_hierarchy = NULL, *f = NULL, *buf = NULL;
+        _cleanup_strv_free_ char **layers = NULL;
+        struct stat st;
+        int r;
+
+        assert(hierarchy);
+        assert(meta_path);
+        assert(overlay_path);
+
+        /* Resolve the path of the host's version of the hierarchy, i.e. what we want to use as lowest layer
+         * in the overlayfs stack. */
+        r = chase(hierarchy, arg_root, CHASE_PREFIX_ROOT, &resolved_hierarchy, NULL);
+        if (r == -ENOENT)
+                log_debug_errno(r, "Hierarchy '%s' on host doesn't exist, not merging.", hierarchy);
+        else if (r < 0)
+                return log_error_errno(r, "Failed to resolve host hierarchy '%s': %m", hierarchy);
+        else {
+                r = dir_is_empty(resolved_hierarchy, /* ignore_hidden_or_backup= */ false);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to check if host hierarchy '%s' is empty: %m", resolved_hierarchy);
+                if (r > 0) {
+                        log_debug("Host hierarchy '%s' is empty, not merging.", resolved_hierarchy);
+                        resolved_hierarchy = mfree(resolved_hierarchy);
+                }
+        }
+
+        /* Let's generate a metadata file that lists all extensions we took into account for this
+         * hierarchy. We include this in the final fs, to make things nicely discoverable and
+         * recognizable. */
+        f = path_join(meta_path, image_class_info[image_class].dot_directory_name, image_class_info[image_class].short_identifier_plural);
+        if (!f)
+                return log_oom();
+
+        buf = strv_join(extensions, "\n");
+        if (!buf)
+                return log_oom();
+
+        r = write_string_file(f, buf, WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_MKDIR_0755);
+        if (r < 0)
+                return log_error_errno(r, "Failed to write extension meta file '%s': %m", f);
+
+        /* Put the meta path (i.e. our synthesized stuff) at the top of the layer stack */
+        layers = strv_new(meta_path);
+        if (!layers)
+                return log_oom();
+
+        /* Put the extensions in the middle */
+        STRV_FOREACH(p, paths) {
+                _cleanup_free_ char *resolved = NULL;
+
+                r = chase(hierarchy, *p, CHASE_PREFIX_ROOT, &resolved, NULL);
+                if (r == -ENOENT) {
+                        log_debug_errno(r, "Hierarchy '%s' in extension '%s' doesn't exist, not merging.", hierarchy, *p);
+                        continue;
+                }
+                if (r < 0)
+                        return log_error_errno(r, "Failed to resolve hierarchy '%s' in extension '%s': %m", hierarchy, *p);
+
+                r = dir_is_empty(resolved, /* ignore_hidden_or_backup= */ false);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to check if hierarchy '%s' in extension '%s' is empty: %m", resolved, *p);
+                if (r > 0) {
+                        log_debug("Hierarchy '%s' in extension '%s' is empty, not merging.", hierarchy, *p);
+                        continue;
+                }
+
+                r = strv_consume(&layers, TAKE_PTR(resolved));
+                if (r < 0)
+                        return log_oom();
+        }
+
+        if (!layers[1]) /* No extension with files in this hierarchy? Then don't do anything. */
+                return 0;
+
+        if (resolved_hierarchy) {
+                /* Add the host hierarchy as last (lowest) layer in the stack */
+                r = strv_consume(&layers, TAKE_PTR(resolved_hierarchy));
+                if (r < 0)
+                        return log_oom();
+        }
+
+        r = mkdir_p(overlay_path, 0700);
+        if (r < 0)
+                return log_error_errno(r, "Failed to make directory '%s': %m", overlay_path);
+
+        r = mount_overlayfs(image_class, noexec, overlay_path, layers);
+        if (r < 0)
+                return r;
+
+        /* The overlayfs superblock is read-only. Let's also mark the bind mount read-only. Extra turbo safety 😎 */
+        r = bind_remount_recursive(overlay_path, MS_RDONLY, MS_RDONLY, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to make bind mount '%s' read-only: %m", overlay_path);
+
+        /* Now we have mounted the new file system. Let's now figure out its .st_dev field, and make that
+         * available in the metadata directory. This is useful to detect whether the metadata dir actually
+         * belongs to the fs it is found on: if .st_dev of the top-level mount matches it, it's pretty likely
+         * we are looking at a live tree, and not an unpacked tar or so of one. */
+        if (stat(overlay_path, &st) < 0)
+                return log_error_errno(r, "Failed to stat mount '%s': %m", overlay_path);
+
+        free(f);
+        f = path_join(meta_path, image_class_info[image_class].dot_directory_name, "dev");
+        if (!f)
+                return log_oom();
+
+        r = write_string_file(f, FORMAT_DEVNUM(st.st_dev), WRITE_STRING_FILE_CREATE);
+        if (r < 0)
+                return log_error_errno(r, "Failed to write '%s': %m", f);
+
+        /* Make sure the top-level dir has an mtime marking the point we established the merge */
+        if (utimensat(AT_FDCWD, meta_path, NULL, AT_SYMLINK_NOFOLLOW) < 0)
+                return log_error_errno(r, "Failed fix mtime of '%s': %m", meta_path);
+
+        return 1;
+}
+
+static int strverscmp_improvedp(char *const* a, char *const* b) {
+        /* usable in qsort() for sorting a string array with strverscmp_improved() */
+        return strverscmp_improved(*a, *b);
+}
+
+static const ImagePolicy *pick_image_policy(const Image *img) {
+        assert(img);
+        assert(img->path);
+
+        /* Explicitly specified policy always wins */
+        if (arg_image_policy)
+                return arg_image_policy;
+
+        /* If located in /.extra/sysext/ in the initrd, then it was placed there by systemd-stub, and was
+         * picked up from an untrusted ESP. Thus, require a stricter policy by default for them. (For the
+         * other directories we assume the appropriate level of trust was already established already.  */
+
+        if (in_initrd() && path_startswith(img->path, "/.extra/sysext/"))
+                return &image_policy_sysext_strict;
+
+        return image_class_info[img->class].default_image_policy;
+}
+
+static int merge_subprocess(
+                ImageClass image_class,
+                char **hierarchies,
+                bool force,
+                int noexec,
+                Hashmap *images,
+                const char *workspace) {
+
+        _cleanup_free_ char *host_os_release_id = NULL, *host_os_release_version_id = NULL, *host_os_release_api_level = NULL, *buf = NULL;
+        _cleanup_strv_free_ char **extensions = NULL, **paths = NULL;
+        size_t n_extensions = 0;
+        unsigned n_ignored = 0;
+        Image *img;
+        int r;
+
+        /* Mark the whole of /run as MS_SLAVE, so that we can mount stuff below it that doesn't show up on
+         * the host otherwise. */
+        r = mount_nofollow_verbose(LOG_ERR, NULL, "/run", NULL, MS_SLAVE|MS_REC, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to remount /run/ MS_SLAVE: %m");
+
+        /* Let's create the workspace if it's missing */
+        r = mkdir_p(workspace, 0700);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create '%s': %m", workspace);
+
+        /* Let's mount a tmpfs to our workspace. This way we don't need to clean up the inodes we mount over,
+         * but let the kernel do that entirely automatically, once our namespace dies. Note that this file
+         * system won't be visible to anyone but us, since we opened our own namespace and then made the
+         * /run/ hierarchy (which our workspace is contained in) MS_SLAVE, see above. */
+        r = mount_nofollow_verbose(LOG_ERR, image_class_info[image_class].short_identifier, workspace, "tmpfs", 0, "mode=0700");
+        if (r < 0)
+                return r;
+
+        /* Acquire host OS release info, so that we can compare it with the extension's data */
+        r = parse_os_release(
+                        arg_root,
+                        "ID", &host_os_release_id,
+                        "VERSION_ID", &host_os_release_version_id,
+                        image_class_info[image_class].level_env, &host_os_release_api_level);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire 'os-release' data of OS tree '%s': %m", empty_to_root(arg_root));
+        if (isempty(host_os_release_id))
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "'ID' field not found or empty in 'os-release' data of OS tree '%s': %m",
+                                       empty_to_root(arg_root));
+
+        /* Let's now mount all images */
+        HASHMAP_FOREACH(img, images) {
+                _cleanup_free_ char *p = NULL;
+
+                p = path_join(workspace, image_class_info[image_class].short_identifier_plural, img->name);
+                if (!p)
+                        return log_oom();
+
+                r = mkdir_p(p, 0700);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to create %s: %m", p);
+
+                switch (img->type) {
+                case IMAGE_DIRECTORY:
+                case IMAGE_SUBVOLUME:
+
+                        if (!force) {
+                                r = extension_has_forbidden_content(p);
+                                if (r < 0)
+                                        return r;
+                                if (r > 0) {
+                                        n_ignored++;
+                                        continue;
+                                }
+                        }
+
+                        r = mount_nofollow_verbose(LOG_ERR, img->path, p, NULL, MS_BIND, NULL);
+                        if (r < 0)
+                                return r;
+
+                        /* Make this a read-only bind mount */
+                        r = bind_remount_recursive(p, MS_RDONLY, MS_RDONLY, NULL);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to make bind mount '%s' read-only: %m", p);
+
+                        break;
+
+                case IMAGE_RAW:
+                case IMAGE_BLOCK: {
+                        _cleanup_(dissected_image_unrefp) DissectedImage *m = NULL;
+                        _cleanup_(loop_device_unrefp) LoopDevice *d = NULL;
+                        _cleanup_(verity_settings_done) VeritySettings verity_settings = VERITY_SETTINGS_DEFAULT;
+                        DissectImageFlags flags =
+                                DISSECT_IMAGE_READ_ONLY |
+                                DISSECT_IMAGE_GENERIC_ROOT |
+                                DISSECT_IMAGE_REQUIRE_ROOT |
+                                DISSECT_IMAGE_MOUNT_ROOT_ONLY |
+                                DISSECT_IMAGE_USR_NO_ROOT |
+                                DISSECT_IMAGE_ADD_PARTITION_DEVICES |
+                                DISSECT_IMAGE_PIN_PARTITION_DEVICES;
+
+                        r = verity_settings_load(&verity_settings, img->path, NULL, NULL);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to read verity artifacts for %s: %m", img->path);
+
+                        if (verity_settings.data_path)
+                                flags |= DISSECT_IMAGE_NO_PARTITION_TABLE;
+
+                        if (!force)
+                                flags |= DISSECT_IMAGE_VALIDATE_OS_EXT;
+
+                        r = loop_device_make_by_path(
+                                        img->path,
+                                        O_RDONLY,
+                                        /* sector_size= */ UINT32_MAX,
+                                        FLAGS_SET(flags, DISSECT_IMAGE_NO_PARTITION_TABLE) ? 0 : LO_FLAGS_PARTSCAN,
+                                        LOCK_SH,
+                                        &d);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to set up loopback device for %s: %m", img->path);
+
+                        r = dissect_loop_device_and_warn(
+                                        d,
+                                        &verity_settings,
+                                        /* mount_options= */ NULL,
+                                        pick_image_policy(img),
+                                        flags,
+                                        &m);
+                        if (r < 0)
+                                return r;
+
+                        r = dissected_image_load_verity_sig_partition(
+                                        m,
+                                        d->fd,
+                                        &verity_settings);
+                        if (r < 0)
+                                return r;
+
+                        r = dissected_image_decrypt_interactively(
+                                        m, NULL,
+                                        &verity_settings,
+                                        flags);
+                        if (r < 0)
+                                return r;
+
+                        r = dissected_image_mount_and_warn(
+                                        m,
+                                        p,
+                                        /* uid_shift= */ UID_INVALID,
+                                        /* uid_range= */ UID_INVALID,
+                                        /* userns_fd= */ -EBADF,
+                                        flags);
+                        if (r < 0 && r != -ENOMEDIUM)
+                                return r;
+                        if (r == -ENOMEDIUM && !force) {
+                                n_ignored++;
+                                continue;
+                        }
+
+                        r = dissected_image_relinquish(m);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to relinquish DM and loopback block devices: %m");
+                        break;
+                }
+                default:
+                        assert_not_reached();
+                }
+
+                if (force)
+                        log_debug("Force mode enabled, skipping version validation.");
+                else {
+                        r = extension_release_validate(
+                                        img->name,
+                                        host_os_release_id,
+                                        host_os_release_version_id,
+                                        host_os_release_api_level,
+                                        in_initrd() ? "initrd" : "system",
+                                        image_extension_release(img, image_class),
+                                        image_class);
+                        if (r < 0)
+                                return r;
+                        if (r == 0) {
+                                n_ignored++;
+                                continue;
+                        }
+                }
+
+                /* Nice! This one is an extension we want. */
+                r = strv_extend(&extensions, img->name);
+                if (r < 0)
+                        return log_oom();
+
+                n_extensions ++;
+        }
+
+        /* Nothing left? Then shortcut things */
+        if (n_extensions == 0) {
+                if (n_ignored > 0)
+                        log_info("No suitable extensions found (%u ignored due to incompatible image(s)).", n_ignored);
+                else
+                        log_info("No extensions found.");
+                return 0;
+        }
+
+        /* Order by version sort with strverscmp_improved() */
+        typesafe_qsort(extensions, n_extensions, strverscmp_improvedp);
+
+        buf = strv_join(extensions, "', '");
+        if (!buf)
+                return log_oom();
+
+        log_info("Using extensions '%s'.", buf);
+
+        /* Build table of extension paths (in reverse order) */
+        paths = new0(char*, n_extensions + 1);
+        if (!paths)
+                return log_oom();
+
+        for (size_t k = 0; k < n_extensions; k++) {
+                _cleanup_free_ char *p = NULL;
+
+                assert_se(img = hashmap_get(images, extensions[n_extensions - 1 - k]));
+
+                p = path_join(workspace, image_class_info[image_class].short_identifier_plural, img->name);
+                if (!p)
+                        return log_oom();
+
+                paths[k] = TAKE_PTR(p);
+        }
+
+        /* Let's now unmerge the status quo ante, since to build the new overlayfs we need a reference to the
+         * underlying fs. */
+        STRV_FOREACH(h, hierarchies) {
+                _cleanup_free_ char *resolved = NULL;
+
+                r = chase(*h, arg_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &resolved, NULL);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to resolve hierarchy '%s%s': %m", strempty(arg_root), *h);
+
+                r = unmerge_hierarchy(image_class, resolved);
+                if (r < 0)
+                        return r;
+        }
+
+        /* Create overlayfs mounts for all hierarchies */
+        STRV_FOREACH(h, hierarchies) {
+                _cleanup_free_ char *meta_path = NULL, *overlay_path = NULL;
+
+                meta_path = path_join(workspace, "meta", *h); /* The place where to store metadata about this instance */
+                if (!meta_path)
+                        return log_oom();
+
+                overlay_path = path_join(workspace, "overlay", *h); /* The resulting overlayfs instance */
+                if (!overlay_path)
+                        return log_oom();
+
+                r = merge_hierarchy(
+                                image_class,
+                                *h,
+                                noexec,
+                                extensions,
+                                paths,
+                                meta_path,
+                                overlay_path);
+                if (r < 0)
+                        return r;
+        }
+
+        /* And move them all into place. This is where things appear in the host namespace */
+        STRV_FOREACH(h, hierarchies) {
+                _cleanup_free_ char *p = NULL, *resolved = NULL;
+
+                p = path_join(workspace, "overlay", *h);
+                if (!p)
+                        return log_oom();
+
+                if (laccess(p, F_OK) < 0) {
+                        if (errno != ENOENT)
+                                return log_error_errno(errno, "Failed to check if '%s' exists: %m", p);
+
+                        /* Hierarchy apparently was empty in all extensions, and wasn't mounted, ignoring. */
+                        continue;
+                }
+
+                r = chase(*h, arg_root, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &resolved, NULL);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to resolve hierarchy '%s%s': %m", strempty(arg_root), *h);
+
+                r = mkdir_p(resolved, 0755);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to create hierarchy mount point '%s': %m", resolved);
+
+                r = mount_nofollow_verbose(LOG_ERR, p, resolved, NULL, MS_BIND, NULL);
+                if (r < 0)
+                        return r;
+
+                log_info("Merged extensions into '%s'.", resolved);
+        }
+
+        return 1;
+}
+
+static int merge(ImageClass image_class,
+                 char **hierarchies,
+                 bool force,
+                 bool no_reload,
+                 int noexec,
+                 Hashmap *images) {
+        pid_t pid;
+        int r;
+
+        r = safe_fork("(sd-merge)", FORK_DEATHSIG_SIGTERM|FORK_LOG|FORK_NEW_MOUNTNS, &pid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to fork off child: %m");
+        if (r == 0) {
+                /* Child with its own mount namespace */
+
+                r = merge_subprocess(image_class, hierarchies, force, noexec, images, "/run/systemd/sysext");
+                if (r < 0)
+                        _exit(EXIT_FAILURE);
+
+                /* Our namespace ceases to exist here, also implicitly detaching all temporary mounts we
+                 * created below /run. Nice! */
+
+                _exit(r > 0 ? EXIT_SUCCESS : 123); /* 123 means: didn't find any extensions */
+        }
+
+        r = wait_for_terminate_and_check("(sd-merge)", pid, WAIT_LOG_ABNORMAL);
+        if (r < 0)
+                return r;
+
+        if (r == 123) /* exit code 123 means: didn't do anything */
+                return 0;
+
+        r = need_reload(image_class, hierarchies, no_reload);
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                r = daemon_reload();
+                if (r < 0)
+                        return r;
+        }
+
+        return 1;
+}
+
+static int image_discover_and_read_metadata(
+                ImageClass image_class,
+                Hashmap **ret_images) {
+        _cleanup_hashmap_free_ Hashmap *images = NULL;
+        Image *img;
+        int r;
+
+        assert(ret_images);
+
+        images = hashmap_new(&image_hash_ops);
+        if (!images)
+                return log_oom();
+
+        r = image_discover(image_class, arg_root, images);
+        if (r < 0)
+                return log_error_errno(r, "Failed to discover images: %m");
+
+        HASHMAP_FOREACH(img, images) {
+                r = image_read_metadata(img, image_class_info[image_class].default_image_policy);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to read metadata for image %s: %m", img->name);
+        }
+
+        *ret_images = TAKE_PTR(images);
+
+        return 0;
+}
+
+static int look_for_merged_hierarchies(
+                ImageClass image_class,
+                char **hierarchies,
+                const char **ret_which) {
+        int r;
+
+        assert(ret_which);
+
+        /* In merge mode fail if things are already merged. (In --refresh mode below we'll unmerge if we find
+         * things are already merged...) */
+        STRV_FOREACH(p, hierarchies) {
+                _cleanup_free_ char *resolved = NULL;
+
+                r = chase(*p, arg_root, CHASE_PREFIX_ROOT, &resolved, NULL);
+                if (r == -ENOENT) {
+                        log_debug_errno(r, "Hierarchy '%s%s' does not exist, ignoring.", strempty(arg_root), *p);
+                        continue;
+                }
+                if (r < 0)
+                        return log_error_errno(r, "Failed to resolve path to hierarchy '%s%s': %m", strempty(arg_root), *p);
+
+                r = is_our_mount_point(image_class, resolved);
+                if (r < 0)
+                        return r;
+                if (r > 0) {
+                        *ret_which = *p;
+                        return 1;
+                }
+        }
+
+        *ret_which = NULL;
+        return 0;
+}
+
+static int verb_merge(int argc, char **argv, void *userdata) {
+        _cleanup_hashmap_free_ Hashmap *images = NULL;
+        const char *which;
+        int r;
+
+        r = have_effective_cap(CAP_SYS_ADMIN);
+        if (r < 0)
+                return log_error_errno(r, "Failed to check if we have enough privileges: %m");
+        if (r == 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be privileged.");
+
+        r = image_discover_and_read_metadata(arg_image_class, &images);
+        if (r < 0)
+                return r;
+
+        r = look_for_merged_hierarchies(arg_image_class, arg_hierarchies, &which);
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EBUSY), "Hierarchy '%s' is already merged.", which);
+
+        return merge(arg_image_class,
+                     arg_hierarchies,
+                     arg_force,
+                     arg_no_reload,
+                     arg_noexec,
+                     images);
+}
+
+typedef struct MethodMergeParameters {
+        const char *class;
+        int force;
+        int no_reload;
+        int noexec;
+} MethodMergeParameters;
+
+static int parse_merge_parameters(Varlink *link, JsonVariant *parameters, MethodMergeParameters *p) {
+
+        static const JsonDispatch dispatch_table[] = {
+                { "class",    JSON_VARIANT_STRING,  json_dispatch_const_string, offsetof(MethodMergeParameters, class),     0 },
+                { "force",    JSON_VARIANT_BOOLEAN, json_dispatch_boolean,      offsetof(MethodMergeParameters, force),     0 },
+                { "noReload", JSON_VARIANT_BOOLEAN, json_dispatch_boolean,      offsetof(MethodMergeParameters, no_reload), 0 },
+                { "noexec",   JSON_VARIANT_BOOLEAN, json_dispatch_boolean,      offsetof(MethodMergeParameters, noexec),    0 },
+                {}
+        };
+
+        assert(link);
+        assert(parameters);
+        assert(p);
+
+        return varlink_dispatch(link, parameters, dispatch_table, p);
+}
+
+static int vl_method_merge(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {
+        _cleanup_hashmap_free_ Hashmap *images = NULL;
+        MethodMergeParameters p = {
+                .force = -1,
+                .no_reload = -1,
+                .noexec = -1,
+        };
+        _cleanup_strv_free_ char **hierarchies = NULL;
+        ImageClass image_class = arg_image_class;
+        int r;
+
+        assert(link);
+
+        r = parse_merge_parameters(link, parameters, &p);
+        if (r != 0)
+                return r;
+
+        r = parse_image_class_parameter(link, p.class, &image_class, &hierarchies);
+        if (r < 0)
+                return r;
+
+        r = image_discover_and_read_metadata(image_class, &images);
+        if (r < 0)
+                return r;
+
+        const char *which;
+        r = look_for_merged_hierarchies(
+                        image_class,
+                        hierarchies ?: arg_hierarchies,
+                        &which);
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return varlink_errorb(link, "io.systemd.sysext.AlreadyMerged", JSON_BUILD_OBJECT(JSON_BUILD_PAIR_STRING("hierarchy", which)));
+
+        r = merge(image_class,
+                  hierarchies ?: arg_hierarchies,
+                  p.force >= 0 ? p.force : arg_force,
+                  p.no_reload >= 0 ? p.no_reload : arg_no_reload,
+                  p.noexec >= 0 ? p.noexec : arg_noexec,
+                  images);
+        if (r < 0)
+                return r;
+
+        return varlink_reply(link, NULL);
+}
+
+static int refresh(
+                ImageClass image_class,
+                char **hierarchies,
+                bool force,
+                bool no_reload,
+                int noexec) {
+
+        _cleanup_hashmap_free_ Hashmap *images = NULL;
+        int r;
+
+        r = image_discover_and_read_metadata(image_class, &images);
+        if (r < 0)
+                return r;
+
+        /* Returns > 0 if it did something, i.e. a new overlayfs is mounted now. When it does so it
+         * implicitly unmounts any overlayfs placed there before. Returns == 0 if it did nothing, i.e. no
+         * extension images found. In this case the old overlayfs remains in place if there was one. */
+        r = merge(image_class, hierarchies, force, no_reload, noexec, images);
+        if (r < 0)
+                return r;
+        if (r == 0) /* No images found? Then unmerge. The goal of --refresh is after all that after having
+                     * called there's a guarantee that the merge status matches the installed extensions. */
+                r = unmerge(image_class, hierarchies, no_reload);
+
+        /* Net result here is that:
+         *
+         * 1. If an overlayfs was mounted before and no extensions exist anymore, we'll have unmerged things.
+         *
+         * 2. If an overlayfs was mounted before, and there are still extensions installed' we'll have
+         *    unmerged and then merged things again.
+         *
+         * 3. If an overlayfs so far wasn't mounted, and there are extensions installed, we'll have it
+         *    mounted now.
+         *
+         * 4. If there was no overlayfs mount so far, and no extensions installed, we implement a NOP.
+         */
+
+        return 0;
+}
+
+static int verb_refresh(int argc, char **argv, void *userdata) {
+        int r;
+
+        r = have_effective_cap(CAP_SYS_ADMIN);
+        if (r < 0)
+                return log_error_errno(r, "Failed to check if we have enough privileges: %m");
+        if (r == 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be privileged.");
+
+        return refresh(arg_image_class,
+                       arg_hierarchies,
+                       arg_force,
+                       arg_no_reload,
+                       arg_noexec);
+}
+
+static int vl_method_refresh(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {
+
+        MethodMergeParameters p = {
+                .force = -1,
+                .no_reload = -1,
+                .noexec = -1,
+        };
+        _cleanup_strv_free_ char **hierarchies = NULL;
+        ImageClass image_class = arg_image_class;
+        int r;
+
+        assert(link);
+
+        r = parse_merge_parameters(link, parameters, &p);
+        if (r != 0)
+                return r;
+
+        r = parse_image_class_parameter(link, p.class, &image_class, &hierarchies);
+        if (r < 0)
+                return r;
+
+        r = refresh(image_class,
+                    hierarchies ?: arg_hierarchies,
+                    p.force >= 0 ? p.force : arg_force,
+                    p.no_reload >= 0 ? p.no_reload : arg_no_reload,
+                    p.noexec >= 0 ? p.noexec : arg_noexec);
+        if (r < 0)
+                return r;
+
+        return varlink_reply(link, NULL);
+}
+
+static int verb_list(int argc, char **argv, void *userdata) {
+        _cleanup_hashmap_free_ Hashmap *images = NULL;
+        _cleanup_(table_unrefp) Table *t = NULL;
+        Image *img;
+        int r;
+
+        images = hashmap_new(&image_hash_ops);
+        if (!images)
+                return log_oom();
+
+        r = image_discover(arg_image_class, arg_root, images);
+        if (r < 0)
+                return log_error_errno(r, "Failed to discover images: %m");
+
+        if ((arg_json_format_flags & JSON_FORMAT_OFF) && hashmap_isempty(images)) {
+                log_info("No OS extensions found.");
+                return 0;
+        }
+
+        t = table_new("name", "type", "path", "time");
+        if (!t)
+                return log_oom();
+
+        HASHMAP_FOREACH(img, images) {
+                r = table_add_many(
+                                t,
+                                TABLE_STRING, img->name,
+                                TABLE_STRING, image_type_to_string(img->type),
+                                TABLE_PATH, img->path,
+                                TABLE_TIMESTAMP, img->mtime != 0 ? img->mtime : img->crtime);
+                if (r < 0)
+                        return table_log_add_error(r);
+        }
+
+        (void) table_set_sort(t, (size_t) 0);
+
+        return table_print_with_pager(t, arg_json_format_flags, arg_pager_flags, arg_legend);
+}
+
+typedef struct MethodListParameters {
+        const char *class;
+} MethodListParameters;
+
+static int vl_method_list(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {
+
+        static const JsonDispatch dispatch_table[] = {
+                { "class",    JSON_VARIANT_STRING,  json_dispatch_const_string, offsetof(MethodListParameters, class),     0 },
+                {}
+        };
+        MethodListParameters p = {
+        };
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        _cleanup_hashmap_free_ Hashmap *images = NULL;
+        ImageClass image_class = arg_image_class;
+        Image *img;
+        int r;
+
+        assert(link);
+
+        r = varlink_dispatch(link, parameters, dispatch_table, &p);
+        if (r != 0)
+                return r;
+
+        r = parse_image_class_parameter(link, p.class, &image_class, NULL);
+        if (r < 0)
+                return r;
+
+        images = hashmap_new(&image_hash_ops);
+        if (!images)
+                return -ENOMEM;
+
+        r = image_discover(image_class, arg_root, images);
+        if (r < 0)
+                return r;
+
+        HASHMAP_FOREACH(img, images) {
+                if (v) {
+                        /* Send previous item with more=true */
+                        r = varlink_notify(link, v);
+                        if (r < 0)
+                                return r;
+                }
+
+                v = json_variant_unref(v);
+
+                r = image_to_json(img, &v);
+                if (r < 0)
+                        return r;
+        }
+
+        if (v)  /* Send final item with more=false */
+                return varlink_reply(link, v);
+
+        return varlink_error(link, "io.systemd.sysext.NoImagesFound", NULL);
+}
+
+static int verb_help(int argc, char **argv, void *userdata) {
+        _cleanup_free_ char *link = NULL;
+        int r;
+
+        r = terminal_urlify_man("systemd-sysext", "8", &link);
+        if (r < 0)
+                return log_oom();
+
+        printf("%1$s [OPTIONS...] COMMAND\n"
+                "\n%5$sMerge extension images into /usr/ and /opt/ hierarchies for\n"
+               " sysext and into the /etc/ hierarchy for confext.%6$s\n"
+               "  status                  Show current merge status (default)\n"
+               "  merge                   Merge extensions into relevant hierarchies\n"
+               "  unmerge                 Unmerge extensions from relevant hierarchies\n"
+               "  refresh                 Unmerge/merge extensions again\n"
+               "  list                    List installed extensions\n"
+               "  -h --help               Show this help\n"
+               "     --version            Show package version\n"
+               "\n%3$sOptions:%4$s\n"
+               "     --no-pager           Do not pipe output into a pager\n"
+               "     --no-legend          Do not show the headers and footers\n"
+               "     --root=PATH          Operate relative to root path\n"
+               "     --json=pretty|short|off\n"
+               "                          Generate JSON output\n"
+               "     --force              Ignore version incompatibilities\n"
+               "     --no-reload          Do not reload the service manager\n"
+               "     --image-policy=POLICY\n"
+               "                          Specify disk image dissection policy\n"
+               "     --noexec=BOOL        Whether to mount extension overlay with noexec\n"
+               "\nSee the %2$s for details.\n",
+               program_invocation_short_name,
+               link,
+               ansi_underline(),
+               ansi_normal(),
+               ansi_highlight(),
+               ansi_normal());
+
+        return 0;
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+        enum {
+                ARG_VERSION = 0x100,
+                ARG_NO_PAGER,
+                ARG_NO_LEGEND,
+                ARG_ROOT,
+                ARG_JSON,
+                ARG_FORCE,
+                ARG_IMAGE_POLICY,
+                ARG_NOEXEC,
+                ARG_NO_RELOAD,
+        };
+
+        static const struct option options[] = {
+                { "help",         no_argument,       NULL, 'h'              },
+                { "version",      no_argument,       NULL, ARG_VERSION      },
+                { "no-pager",     no_argument,       NULL, ARG_NO_PAGER     },
+                { "no-legend",    no_argument,       NULL, ARG_NO_LEGEND    },
+                { "root",         required_argument, NULL, ARG_ROOT         },
+                { "json",         required_argument, NULL, ARG_JSON         },
+                { "force",        no_argument,       NULL, ARG_FORCE        },
+                { "image-policy", required_argument, NULL, ARG_IMAGE_POLICY },
+                { "noexec",       required_argument, NULL, ARG_NOEXEC       },
+                { "no-reload",    no_argument,       NULL, ARG_NO_RELOAD    },
+                {}
+        };
+
+        int c, r;
+
+        assert(argc >= 0);
+        assert(argv);
+
+        while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0)
+
+                switch (c) {
+
+                case 'h':
+                        return verb_help(argc, argv, NULL);
+
+                case ARG_VERSION:
+                        return version();
+
+                case ARG_NO_PAGER:
+                        arg_pager_flags |= PAGER_DISABLE;
+                        break;
+
+                case ARG_NO_LEGEND:
+                        arg_legend = false;
+                        break;
+
+                case ARG_ROOT:
+                        r = parse_path_argument(optarg, false, &arg_root);
+                        if (r < 0)
+                                return r;
+                        /* If --root= is provided, do not reload the service manager */
+                        arg_no_reload = true;
+                        break;
+
+                case ARG_JSON:
+                        r = parse_json_argument(optarg, &arg_json_format_flags);
+                        if (r <= 0)
+                                return r;
+
+                        break;
+
+                case ARG_FORCE:
+                        arg_force = true;
+                        break;
+
+                case ARG_IMAGE_POLICY:
+                        r = parse_image_policy_argument(optarg, &arg_image_policy);
+                        if (r < 0)
+                                return r;
+                        break;
+
+                case ARG_NOEXEC:
+                        r = parse_boolean_argument("--noexec", optarg, NULL);
+                        if (r < 0)
+                                return r;
+
+                        arg_noexec = r;
+                        break;
+
+                case ARG_NO_RELOAD:
+                        arg_no_reload = true;
+                        break;
+
+                case '?':
+                        return -EINVAL;
+
+                default:
+                        assert_not_reached();
+                }
+
+        r = varlink_invocation(VARLINK_ALLOW_ACCEPT);
+        if (r < 0)
+                return log_error_errno(r, "Failed to check if invoked in Varlink mode: %m");
+        if (r > 0)
+                arg_varlink = true;
+
+        return 1;
+}
+
+static int sysext_main(int argc, char *argv[]) {
+
+        static const Verb verbs[] = {
+                { "status",   VERB_ANY, 1, VERB_DEFAULT, verb_status  },
+                { "merge",    VERB_ANY, 1, 0,            verb_merge   },
+                { "unmerge",  VERB_ANY, 1, 0,            verb_unmerge },
+                { "refresh",  VERB_ANY, 1, 0,            verb_refresh },
+                { "list",     VERB_ANY, 1, 0,            verb_list    },
+                { "help",     VERB_ANY, 1, 0,            verb_help    },
+                {}
+        };
+
+        return dispatch_verb(argc, argv, verbs, NULL);
+}
+
+static int run(int argc, char *argv[]) {
+        int r;
+
+        log_setup();
+
+        arg_image_class = invoked_as(argv, "systemd-confext") ? IMAGE_CONFEXT : IMAGE_SYSEXT;
+
+        r = parse_argv(argc, argv);
+        if (r <= 0)
+                return r;
+
+        /* For debugging purposes it might make sense to do this for other hierarchies than /usr/ and
+         * /opt/, but let's make that a hacker/debugging feature, i.e. env var instead of cmdline
+         * switch. */
+        r = parse_env_extension_hierarchies(&arg_hierarchies, image_class_info[arg_image_class].name_env);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse environment variable: %m");
+
+        if (arg_varlink) {
+                _cleanup_(varlink_server_unrefp) VarlinkServer *varlink_server = NULL;
+
+                /* Invocation as Varlink service */
+
+                r = varlink_server_new(&varlink_server, VARLINK_SERVER_ROOT_ONLY);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to allocate Varlink server: %m");
+
+                r = varlink_server_add_interface(varlink_server, &vl_interface_io_systemd_sysext);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to add Varlink interface: %m");
+
+                r = varlink_server_bind_method_many(
+                                varlink_server,
+                                "io.systemd.sysext.Merge", vl_method_merge,
+                                "io.systemd.sysext.Unmerge", vl_method_unmerge,
+                                "io.systemd.sysext.Refresh", vl_method_refresh,
+                                "io.systemd.sysext.List", vl_method_list);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to bind Varlink methods: %m");
+
+                r = varlink_server_loop_auto(varlink_server);
+                if (r == -EPERM)
+                        return log_error_errno(r, "Invoked by unprivileged Varlink peer, refusing.");
+                if (r < 0)
+                        return log_error_errno(r, "Failed to run Varlink event loop: %m");
+
+                return EXIT_SUCCESS;
+        }
+
+        return sysext_main(argc, argv);
+}
+
+DEFINE_MAIN_FUNCTION(run);