Adding upstream version 241.upstream/241upstream

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

1 files changed, 2933 insertions, 0 deletions

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
new file mode 100644
index 0000000..8ce7ccb
--- /dev/null
+++ b/src/basic/cgroup-util.c
@@ -0,0 +1,2933 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <dirent.h>
+#include <errno.h>
+#include <ftw.h>
+#include <limits.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdio_ext.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/statfs.h>
+#include <sys/types.h>
+#include <sys/utsname.h>
+#include <sys/xattr.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "cgroup-util.h"
+#include "def.h"
+#include "dirent-util.h"
+#include "extract-word.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "format-util.h"
+#include "fs-util.h"
+#include "log.h"
+#include "login-util.h"
+#include "macro.h"
+#include "missing.h"
+#include "mkdir.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "proc-cmdline.h"
+#include "process-util.h"
+#include "set.h"
+#include "special.h"
+#include "stat-util.h"
+#include "stdio-util.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "strv.h"
+#include "unit-name.h"
+#include "user-util.h"
+
+int cg_enumerate_processes(const char *controller, const char *path, FILE **_f) {
+        _cleanup_free_ char *fs = NULL;
+        FILE *f;
+        int r;
+
+        assert(_f);
+
+        r = cg_get_path(controller, path, "cgroup.procs", &fs);
+        if (r < 0)
+                return r;
+
+        f = fopen(fs, "re");
+        if (!f)
+                return -errno;
+
+        *_f = f;
+        return 0;
+}
+
+int cg_read_pid(FILE *f, pid_t *_pid) {
+        unsigned long ul;
+
+        /* Note that the cgroup.procs might contain duplicates! See
+         * cgroups.txt for details. */
+
+        assert(f);
+        assert(_pid);
+
+        errno = 0;
+        if (fscanf(f, "%lu", &ul) != 1) {
+
+                if (feof(f))
+                        return 0;
+
+                return errno > 0 ? -errno : -EIO;
+        }
+
+        if (ul <= 0)
+                return -EIO;
+
+        *_pid = (pid_t) ul;
+        return 1;
+}
+
+int cg_read_event(
+                const char *controller,
+                const char *path,
+                const char *event,
+                char **val) {
+
+        _cleanup_free_ char *events = NULL, *content = NULL;
+        char *p, *line;
+        int r;
+
+        r = cg_get_path(controller, path, "cgroup.events", &events);
+        if (r < 0)
+                return r;
+
+        r = read_full_file(events, &content, NULL);
+        if (r < 0)
+                return r;
+
+        p = content;
+        while ((line = strsep(&p, "\n"))) {
+                char *key;
+
+                key = strsep(&line, " ");
+                if (!key || !line)
+                        return -EINVAL;
+
+                if (strcmp(key, event))
+                        continue;
+
+                *val = strdup(line);
+                return 0;
+        }
+
+        return -ENOENT;
+}
+
+bool cg_ns_supported(void) {
+        static thread_local int enabled = -1;
+
+        if (enabled >= 0)
+                return enabled;
+
+        if (access("/proc/self/ns/cgroup", F_OK) < 0) {
+                if (errno != ENOENT)
+                        log_debug_errno(errno, "Failed to check whether /proc/self/ns/cgroup is available, assuming not: %m");
+                enabled = false;
+        } else
+                enabled = true;
+
+        return enabled;
+}
+
+int cg_enumerate_subgroups(const char *controller, const char *path, DIR **_d) {
+        _cleanup_free_ char *fs = NULL;
+        int r;
+        DIR *d;
+
+        assert(_d);
+
+        /* This is not recursive! */
+
+        r = cg_get_path(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        d = opendir(fs);
+        if (!d)
+                return -errno;
+
+        *_d = d;
+        return 0;
+}
+
+int cg_read_subgroup(DIR *d, char **fn) {
+        struct dirent *de;
+
+        assert(d);
+        assert(fn);
+
+        FOREACH_DIRENT_ALL(de, d, return -errno) {
+                char *b;
+
+                if (de->d_type != DT_DIR)
+                        continue;
+
+                if (dot_or_dot_dot(de->d_name))
+                        continue;
+
+                b = strdup(de->d_name);
+                if (!b)
+                        return -ENOMEM;
+
+                *fn = b;
+                return 1;
+        }
+
+        return 0;
+}
+
+int cg_rmdir(const char *controller, const char *path) {
+        _cleanup_free_ char *p = NULL;
+        int r;
+
+        r = cg_get_path(controller, path, NULL, &p);
+        if (r < 0)
+                return r;
+
+        r = rmdir(p);
+        if (r < 0 && errno != ENOENT)
+                return -errno;
+
+        r = cg_hybrid_unified();
+        if (r <= 0)
+                return r;
+
+        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+                r = cg_rmdir(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to remove compat systemd cgroup %s: %m", path);
+        }
+
+        return 0;
+}
+
+int cg_kill(
+                const char *controller,
+                const char *path,
+                int sig,
+                CGroupFlags flags,
+                Set *s,
+                cg_kill_log_func_t log_kill,
+                void *userdata) {
+
+        _cleanup_set_free_ Set *allocated_set = NULL;
+        bool done = false;
+        int r, ret = 0;
+        pid_t my_pid;
+
+        assert(sig >= 0);
+
+         /* Don't send SIGCONT twice. Also, SIGKILL always works even when process is suspended, hence don't send
+          * SIGCONT on SIGKILL. */
+        if (IN_SET(sig, SIGCONT, SIGKILL))
+                flags &= ~CGROUP_SIGCONT;
+
+        /* This goes through the tasks list and kills them all. This
+         * is repeated until no further processes are added to the
+         * tasks list, to properly handle forking processes */
+
+        if (!s) {
+                s = allocated_set = set_new(NULL);
+                if (!s)
+                        return -ENOMEM;
+        }
+
+        my_pid = getpid_cached();
+
+        do {
+                _cleanup_fclose_ FILE *f = NULL;
+                pid_t pid = 0;
+                done = true;
+
+                r = cg_enumerate_processes(controller, path, &f);
+                if (r < 0) {
+                        if (ret >= 0 && r != -ENOENT)
+                                return r;
+
+                        return ret;
+                }
+
+                while ((r = cg_read_pid(f, &pid)) > 0) {
+
+                        if ((flags & CGROUP_IGNORE_SELF) && pid == my_pid)
+                                continue;
+
+                        if (set_get(s, PID_TO_PTR(pid)) == PID_TO_PTR(pid))
+                                continue;
+
+                        if (log_kill)
+                                log_kill(pid, sig, userdata);
+
+                        /* If we haven't killed this process yet, kill
+                         * it */
+                        if (kill(pid, sig) < 0) {
+                                if (ret >= 0 && errno != ESRCH)
+                                        ret = -errno;
+                        } else {
+                                if (flags & CGROUP_SIGCONT)
+                                        (void) kill(pid, SIGCONT);
+
+                                if (ret == 0)
+                                        ret = 1;
+                        }
+
+                        done = false;
+
+                        r = set_put(s, PID_TO_PTR(pid));
+                        if (r < 0) {
+                                if (ret >= 0)
+                                        return r;
+
+                                return ret;
+                        }
+                }
+
+                if (r < 0) {
+                        if (ret >= 0)
+                                return r;
+
+                        return ret;
+                }
+
+                /* To avoid racing against processes which fork
+                 * quicker than we can kill them we repeat this until
+                 * no new pids need to be killed. */
+
+        } while (!done);
+
+        return ret;
+}
+
+int cg_kill_recursive(
+                const char *controller,
+                const char *path,
+                int sig,
+                CGroupFlags flags,
+                Set *s,
+                cg_kill_log_func_t log_kill,
+                void *userdata) {
+
+        _cleanup_set_free_ Set *allocated_set = NULL;
+        _cleanup_closedir_ DIR *d = NULL;
+        int r, ret;
+        char *fn;
+
+        assert(path);
+        assert(sig >= 0);
+
+        if (!s) {
+                s = allocated_set = set_new(NULL);
+                if (!s)
+                        return -ENOMEM;
+        }
+
+        ret = cg_kill(controller, path, sig, flags, s, log_kill, userdata);
+
+        r = cg_enumerate_subgroups(controller, path, &d);
+        if (r < 0) {
+                if (ret >= 0 && r != -ENOENT)
+                        return r;
+
+                return ret;
+        }
+
+        while ((r = cg_read_subgroup(d, &fn)) > 0) {
+                _cleanup_free_ char *p = NULL;
+
+                p = strjoin(path, "/", fn);
+                free(fn);
+                if (!p)
+                        return -ENOMEM;
+
+                r = cg_kill_recursive(controller, p, sig, flags, s, log_kill, userdata);
+                if (r != 0 && ret >= 0)
+                        ret = r;
+        }
+        if (ret >= 0 && r < 0)
+                ret = r;
+
+        if (flags & CGROUP_REMOVE) {
+                r = cg_rmdir(controller, path);
+                if (r < 0 && ret >= 0 && !IN_SET(r, -ENOENT, -EBUSY))
+                        return r;
+        }
+
+        return ret;
+}
+
+int cg_migrate(
+                const char *cfrom,
+                const char *pfrom,
+                const char *cto,
+                const char *pto,
+                CGroupFlags flags) {
+
+        bool done = false;
+        _cleanup_set_free_ Set *s = NULL;
+        int r, ret = 0;
+        pid_t my_pid;
+
+        assert(cfrom);
+        assert(pfrom);
+        assert(cto);
+        assert(pto);
+
+        s = set_new(NULL);
+        if (!s)
+                return -ENOMEM;
+
+        my_pid = getpid_cached();
+
+        do {
+                _cleanup_fclose_ FILE *f = NULL;
+                pid_t pid = 0;
+                done = true;
+
+                r = cg_enumerate_processes(cfrom, pfrom, &f);
+                if (r < 0) {
+                        if (ret >= 0 && r != -ENOENT)
+                                return r;
+
+                        return ret;
+                }
+
+                while ((r = cg_read_pid(f, &pid)) > 0) {
+
+                        /* This might do weird stuff if we aren't a
+                         * single-threaded program. However, we
+                         * luckily know we are not */
+                        if ((flags & CGROUP_IGNORE_SELF) && pid == my_pid)
+                                continue;
+
+                        if (set_get(s, PID_TO_PTR(pid)) == PID_TO_PTR(pid))
+                                continue;
+
+                        /* Ignore kernel threads. Since they can only
+                         * exist in the root cgroup, we only check for
+                         * them there. */
+                        if (cfrom &&
+                            empty_or_root(pfrom) &&
+                            is_kernel_thread(pid) > 0)
+                                continue;
+
+                        r = cg_attach(cto, pto, pid);
+                        if (r < 0) {
+                                if (ret >= 0 && r != -ESRCH)
+                                        ret = r;
+                        } else if (ret == 0)
+                                ret = 1;
+
+                        done = false;
+
+                        r = set_put(s, PID_TO_PTR(pid));
+                        if (r < 0) {
+                                if (ret >= 0)
+                                        return r;
+
+                                return ret;
+                        }
+                }
+
+                if (r < 0) {
+                        if (ret >= 0)
+                                return r;
+
+                        return ret;
+                }
+        } while (!done);
+
+        return ret;
+}
+
+int cg_migrate_recursive(
+                const char *cfrom,
+                const char *pfrom,
+                const char *cto,
+                const char *pto,
+                CGroupFlags flags) {
+
+        _cleanup_closedir_ DIR *d = NULL;
+        int r, ret = 0;
+        char *fn;
+
+        assert(cfrom);
+        assert(pfrom);
+        assert(cto);
+        assert(pto);
+
+        ret = cg_migrate(cfrom, pfrom, cto, pto, flags);
+
+        r = cg_enumerate_subgroups(cfrom, pfrom, &d);
+        if (r < 0) {
+                if (ret >= 0 && r != -ENOENT)
+                        return r;
+
+                return ret;
+        }
+
+        while ((r = cg_read_subgroup(d, &fn)) > 0) {
+                _cleanup_free_ char *p = NULL;
+
+                p = strjoin(pfrom, "/", fn);
+                free(fn);
+                if (!p)
+                        return -ENOMEM;
+
+                r = cg_migrate_recursive(cfrom, p, cto, pto, flags);
+                if (r != 0 && ret >= 0)
+                        ret = r;
+        }
+
+        if (r < 0 && ret >= 0)
+                ret = r;
+
+        if (flags & CGROUP_REMOVE) {
+                r = cg_rmdir(cfrom, pfrom);
+                if (r < 0 && ret >= 0 && !IN_SET(r, -ENOENT, -EBUSY))
+                        return r;
+        }
+
+        return ret;
+}
+
+int cg_migrate_recursive_fallback(
+                const char *cfrom,
+                const char *pfrom,
+                const char *cto,
+                const char *pto,
+                CGroupFlags flags) {
+
+        int r;
+
+        assert(cfrom);
+        assert(pfrom);
+        assert(cto);
+        assert(pto);
+
+        r = cg_migrate_recursive(cfrom, pfrom, cto, pto, flags);
+        if (r < 0) {
+                char prefix[strlen(pto) + 1];
+
+                /* This didn't work? Then let's try all prefixes of the destination */
+
+                PATH_FOREACH_PREFIX(prefix, pto) {
+                        int q;
+
+                        q = cg_migrate_recursive(cfrom, pfrom, cto, prefix, flags);
+                        if (q >= 0)
+                                return q;
+                }
+        }
+
+        return r;
+}
+
+static const char *controller_to_dirname(const char *controller) {
+        const char *e;
+
+        assert(controller);
+
+        /* Converts a controller name to the directory name below
+         * /sys/fs/cgroup/ we want to mount it to. Effectively, this
+         * just cuts off the name= prefixed used for named
+         * hierarchies, if it is specified. */
+
+        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+                if (cg_hybrid_unified() > 0)
+                        controller = SYSTEMD_CGROUP_CONTROLLER_HYBRID;
+                else
+                        controller = SYSTEMD_CGROUP_CONTROLLER_LEGACY;
+        }
+
+        e = startswith(controller, "name=");
+        if (e)
+                return e;
+
+        return controller;
+}
+
+static int join_path_legacy(const char *controller, const char *path, const char *suffix, char **fs) {
+        const char *dn;
+        char *t = NULL;
+
+        assert(fs);
+        assert(controller);
+
+        dn = controller_to_dirname(controller);
+
+        if (isempty(path) && isempty(suffix))
+                t = strappend("/sys/fs/cgroup/", dn);
+        else if (isempty(path))
+                t = strjoin("/sys/fs/cgroup/", dn, "/", suffix);
+        else if (isempty(suffix))
+                t = strjoin("/sys/fs/cgroup/", dn, "/", path);
+        else
+                t = strjoin("/sys/fs/cgroup/", dn, "/", path, "/", suffix);
+        if (!t)
+                return -ENOMEM;
+
+        *fs = t;
+        return 0;
+}
+
+static int join_path_unified(const char *path, const char *suffix, char **fs) {
+        char *t;
+
+        assert(fs);
+
+        if (isempty(path) && isempty(suffix))
+                t = strdup("/sys/fs/cgroup");
+        else if (isempty(path))
+                t = strappend("/sys/fs/cgroup/", suffix);
+        else if (isempty(suffix))
+                t = strappend("/sys/fs/cgroup/", path);
+        else
+                t = strjoin("/sys/fs/cgroup/", path, "/", suffix);
+        if (!t)
+                return -ENOMEM;
+
+        *fs = t;
+        return 0;
+}
+
+int cg_get_path(const char *controller, const char *path, const char *suffix, char **fs) {
+        int r;
+
+        assert(fs);
+
+        if (!controller) {
+                char *t;
+
+                /* If no controller is specified, we return the path
+                 * *below* the controllers, without any prefix. */
+
+                if (!path && !suffix)
+                        return -EINVAL;
+
+                if (!suffix)
+                        t = strdup(path);
+                else if (!path)
+                        t = strdup(suffix);
+                else
+                        t = strjoin(path, "/", suffix);
+                if (!t)
+                        return -ENOMEM;
+
+                *fs = path_simplify(t, false);
+                return 0;
+        }
+
+        if (!cg_controller_is_valid(controller))
+                return -EINVAL;
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
+                r = join_path_unified(path, suffix, fs);
+        else
+                r = join_path_legacy(controller, path, suffix, fs);
+        if (r < 0)
+                return r;
+
+        path_simplify(*fs, false);
+        return 0;
+}
+
+static int controller_is_accessible(const char *controller) {
+        int r;
+
+        assert(controller);
+
+        /* Checks whether a specific controller is accessible,
+         * i.e. its hierarchy mounted. In the unified hierarchy all
+         * controllers are considered accessible, except for the named
+         * hierarchies */
+
+        if (!cg_controller_is_valid(controller))
+                return -EINVAL;
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                /* We don't support named hierarchies if we are using
+                 * the unified hierarchy. */
+
+                if (streq(controller, SYSTEMD_CGROUP_CONTROLLER))
+                        return 0;
+
+                if (startswith(controller, "name="))
+                        return -EOPNOTSUPP;
+
+        } else {
+                const char *cc, *dn;
+
+                dn = controller_to_dirname(controller);
+                cc = strjoina("/sys/fs/cgroup/", dn);
+
+                if (laccess(cc, F_OK) < 0)
+                        return -errno;
+        }
+
+        return 0;
+}
+
+int cg_get_path_and_check(const char *controller, const char *path, const char *suffix, char **fs) {
+        int r;
+
+        assert(controller);
+        assert(fs);
+
+        /* Check if the specified controller is actually accessible */
+        r = controller_is_accessible(controller);
+        if (r < 0)
+                return r;
+
+        return cg_get_path(controller, path, suffix, fs);
+}
+
+static int trim_cb(const char *path, const struct stat *sb, int typeflag, struct FTW *ftwbuf) {
+        assert(path);
+        assert(sb);
+        assert(ftwbuf);
+
+        if (typeflag != FTW_DP)
+                return 0;
+
+        if (ftwbuf->level < 1)
+                return 0;
+
+        (void) rmdir(path);
+        return 0;
+}
+
+int cg_trim(const char *controller, const char *path, bool delete_root) {
+        _cleanup_free_ char *fs = NULL;
+        int r = 0, q;
+
+        assert(path);
+
+        r = cg_get_path(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        errno = 0;
+        if (nftw(fs, trim_cb, 64, FTW_DEPTH|FTW_MOUNT|FTW_PHYS) != 0) {
+                if (errno == ENOENT)
+                        r = 0;
+                else if (errno > 0)
+                        r = -errno;
+                else
+                        r = -EIO;
+        }
+
+        if (delete_root) {
+                if (rmdir(fs) < 0 && errno != ENOENT)
+                        return -errno;
+        }
+
+        q = cg_hybrid_unified();
+        if (q < 0)
+                return q;
+        if (q > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+                q = cg_trim(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, delete_root);
+                if (q < 0)
+                        log_warning_errno(q, "Failed to trim compat systemd cgroup %s: %m", path);
+        }
+
+        return r;
+}
+
+/* Create a cgroup in the hierarchy of controller.
+ * Returns 0 if the group already existed, 1 on success, negative otherwise.
+ */
+int cg_create(const char *controller, const char *path) {
+        _cleanup_free_ char *fs = NULL;
+        int r;
+
+        r = cg_get_path_and_check(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        r = mkdir_parents(fs, 0755);
+        if (r < 0)
+                return r;
+
+        r = mkdir_errno_wrapper(fs, 0755);
+        if (r == -EEXIST)
+                return 0;
+        if (r < 0)
+                return r;
+
+        r = cg_hybrid_unified();
+        if (r < 0)
+                return r;
+
+        if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+                r = cg_create(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to create compat systemd cgroup %s: %m", path);
+        }
+
+        return 1;
+}
+
+int cg_create_and_attach(const char *controller, const char *path, pid_t pid) {
+        int r, q;
+
+        assert(pid >= 0);
+
+        r = cg_create(controller, path);
+        if (r < 0)
+                return r;
+
+        q = cg_attach(controller, path, pid);
+        if (q < 0)
+                return q;
+
+        /* This does not remove the cgroup on failure */
+        return r;
+}
+
+int cg_attach(const char *controller, const char *path, pid_t pid) {
+        _cleanup_free_ char *fs = NULL;
+        char c[DECIMAL_STR_MAX(pid_t) + 2];
+        int r;
+
+        assert(path);
+        assert(pid >= 0);
+
+        r = cg_get_path_and_check(controller, path, "cgroup.procs", &fs);
+        if (r < 0)
+                return r;
+
+        if (pid == 0)
+                pid = getpid_cached();
+
+        xsprintf(c, PID_FMT "\n", pid);
+
+        r = write_string_file(fs, c, WRITE_STRING_FILE_DISABLE_BUFFER);
+        if (r < 0)
+                return r;
+
+        r = cg_hybrid_unified();
+        if (r < 0)
+                return r;
+
+        if (r > 0 && streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+                r = cg_attach(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, pid);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to attach "PID_FMT" to compat systemd cgroup %s: %m", pid, path);
+        }
+
+        return 0;
+}
+
+int cg_attach_fallback(const char *controller, const char *path, pid_t pid) {
+        int r;
+
+        assert(controller);
+        assert(path);
+        assert(pid >= 0);
+
+        r = cg_attach(controller, path, pid);
+        if (r < 0) {
+                char prefix[strlen(path) + 1];
+
+                /* This didn't work? Then let's try all prefixes of
+                 * the destination */
+
+                PATH_FOREACH_PREFIX(prefix, path) {
+                        int q;
+
+                        q = cg_attach(controller, prefix, pid);
+                        if (q >= 0)
+                                return q;
+                }
+        }
+
+        return r;
+}
+
+int cg_set_access(
+                const char *controller,
+                const char *path,
+                uid_t uid,
+                gid_t gid) {
+
+        struct Attribute {
+                const char *name;
+                bool fatal;
+        };
+
+        /* cgroup v1, aka legacy/non-unified */
+        static const struct Attribute legacy_attributes[] = {
+                { "cgroup.procs",           true  },
+                { "tasks",                  false },
+                { "cgroup.clone_children",  false },
+                {},
+        };
+
+        /* cgroup v2, aka unified */
+        static const struct Attribute unified_attributes[] = {
+                { "cgroup.procs",           true  },
+                { "cgroup.subtree_control", true  },
+                { "cgroup.threads",         false },
+                {},
+        };
+
+        static const struct Attribute* const attributes[] = {
+                [false] = legacy_attributes,
+                [true]  = unified_attributes,
+        };
+
+        _cleanup_free_ char *fs = NULL;
+        const struct Attribute *i;
+        int r, unified;
+
+        assert(path);
+
+        if (uid == UID_INVALID && gid == GID_INVALID)
+                return 0;
+
+        unified = cg_unified_controller(controller);
+        if (unified < 0)
+                return unified;
+
+        /* Configure access to the cgroup itself */
+        r = cg_get_path(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        r = chmod_and_chown(fs, 0755, uid, gid);
+        if (r < 0)
+                return r;
+
+        /* Configure access to the cgroup's attributes */
+        for (i = attributes[unified]; i->name; i++) {
+                fs = mfree(fs);
+
+                r = cg_get_path(controller, path, i->name, &fs);
+                if (r < 0)
+                        return r;
+
+                r = chmod_and_chown(fs, 0644, uid, gid);
+                if (r < 0) {
+                        if (i->fatal)
+                                return r;
+
+                        log_debug_errno(r, "Failed to set access on cgroup %s, ignoring: %m", fs);
+                }
+        }
+
+        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
+                r = cg_hybrid_unified();
+                if (r < 0)
+                        return r;
+                if (r > 0) {
+                        /* Always propagate access mode from unified to legacy controller */
+                        r = cg_set_access(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, uid, gid);
+                        if (r < 0)
+                                log_debug_errno(r, "Failed to set access on compatibility systemd cgroup %s, ignoring: %m", path);
+                }
+        }
+
+        return 0;
+}
+
+int cg_set_xattr(const char *controller, const char *path, const char *name, const void *value, size_t size, int flags) {
+        _cleanup_free_ char *fs = NULL;
+        int r;
+
+        assert(path);
+        assert(name);
+        assert(value || size <= 0);
+
+        r = cg_get_path(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        if (setxattr(fs, name, value, size, flags) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int cg_get_xattr(const char *controller, const char *path, const char *name, void *value, size_t size) {
+        _cleanup_free_ char *fs = NULL;
+        ssize_t n;
+        int r;
+
+        assert(path);
+        assert(name);
+
+        r = cg_get_path(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        n = getxattr(fs, name, value, size);
+        if (n < 0)
+                return -errno;
+
+        return (int) n;
+}
+
+int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
+        _cleanup_fclose_ FILE *f = NULL;
+        const char *fs, *controller_str;
+        int unified, r;
+        size_t cs = 0;
+
+        assert(path);
+        assert(pid >= 0);
+
+        if (controller) {
+                if (!cg_controller_is_valid(controller))
+                        return -EINVAL;
+        } else
+                controller = SYSTEMD_CGROUP_CONTROLLER;
+
+        unified = cg_unified_controller(controller);
+        if (unified < 0)
+                return unified;
+        if (unified == 0) {
+                if (streq(controller, SYSTEMD_CGROUP_CONTROLLER))
+                        controller_str = SYSTEMD_CGROUP_CONTROLLER_LEGACY;
+                else
+                        controller_str = controller;
+
+                cs = strlen(controller_str);
+        }
+
+        fs = procfs_file_alloca(pid, "cgroup");
+        f = fopen(fs, "re");
+        if (!f)
+                return errno == ENOENT ? -ESRCH : -errno;
+
+        (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
+
+        for (;;) {
+                _cleanup_free_ char *line = NULL;
+                char *e, *p;
+
+                r = read_line(f, LONG_LINE_MAX, &line);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                if (unified) {
+                        e = startswith(line, "0:");
+                        if (!e)
+                                continue;
+
+                        e = strchr(e, ':');
+                        if (!e)
+                                continue;
+                } else {
+                        char *l;
+                        size_t k;
+                        const char *word, *state;
+                        bool found = false;
+
+                        l = strchr(line, ':');
+                        if (!l)
+                                continue;
+
+                        l++;
+                        e = strchr(l, ':');
+                        if (!e)
+                                continue;
+
+                        *e = 0;
+                        FOREACH_WORD_SEPARATOR(word, k, l, ",", state)
+                                if (k == cs && memcmp(word, controller_str, cs) == 0) {
+                                        found = true;
+                                        break;
+                                }
+                        if (!found)
+                                continue;
+                }
+
+                p = strdup(e + 1);
+                if (!p)
+                        return -ENOMEM;
+
+                /* Truncate suffix indicating the process is a zombie */
+                e = endswith(p, " (deleted)");
+                if (e)
+                        *e = 0;
+
+                *path = p;
+                return 0;
+        }
+
+        return -ENODATA;
+}
+
+int cg_install_release_agent(const char *controller, const char *agent) {
+        _cleanup_free_ char *fs = NULL, *contents = NULL;
+        const char *sc;
+        int r;
+
+        assert(agent);
+
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r > 0) /* doesn't apply to unified hierarchy */
+                return -EOPNOTSUPP;
+
+        r = cg_get_path(controller, NULL, "release_agent", &fs);
+        if (r < 0)
+                return r;
+
+        r = read_one_line_file(fs, &contents);
+        if (r < 0)
+                return r;
+
+        sc = strstrip(contents);
+        if (isempty(sc)) {
+                r = write_string_file(fs, agent, WRITE_STRING_FILE_DISABLE_BUFFER);
+                if (r < 0)
+                        return r;
+        } else if (!path_equal(sc, agent))
+                return -EEXIST;
+
+        fs = mfree(fs);
+        r = cg_get_path(controller, NULL, "notify_on_release", &fs);
+        if (r < 0)
+                return r;
+
+        contents = mfree(contents);
+        r = read_one_line_file(fs, &contents);
+        if (r < 0)
+                return r;
+
+        sc = strstrip(contents);
+        if (streq(sc, "0")) {
+                r = write_string_file(fs, "1", WRITE_STRING_FILE_DISABLE_BUFFER);
+                if (r < 0)
+                        return r;
+
+                return 1;
+        }
+
+        if (!streq(sc, "1"))
+                return -EIO;
+
+        return 0;
+}
+
+int cg_uninstall_release_agent(const char *controller) {
+        _cleanup_free_ char *fs = NULL;
+        int r;
+
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r > 0) /* Doesn't apply to unified hierarchy */
+                return -EOPNOTSUPP;
+
+        r = cg_get_path(controller, NULL, "notify_on_release", &fs);
+        if (r < 0)
+                return r;
+
+        r = write_string_file(fs, "0", WRITE_STRING_FILE_DISABLE_BUFFER);
+        if (r < 0)
+                return r;
+
+        fs = mfree(fs);
+
+        r = cg_get_path(controller, NULL, "release_agent", &fs);
+        if (r < 0)
+                return r;
+
+        r = write_string_file(fs, "", WRITE_STRING_FILE_DISABLE_BUFFER);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+int cg_is_empty(const char *controller, const char *path) {
+        _cleanup_fclose_ FILE *f = NULL;
+        pid_t pid;
+        int r;
+
+        assert(path);
+
+        r = cg_enumerate_processes(controller, path, &f);
+        if (r == -ENOENT)
+                return true;
+        if (r < 0)
+                return r;
+
+        r = cg_read_pid(f, &pid);
+        if (r < 0)
+                return r;
+
+        return r == 0;
+}
+
+int cg_is_empty_recursive(const char *controller, const char *path) {
+        int r;
+
+        assert(path);
+
+        /* The root cgroup is always populated */
+        if (controller && empty_or_root(path))
+                return false;
+
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                _cleanup_free_ char *t = NULL;
+
+                /* On the unified hierarchy we can check empty state
+                 * via the "populated" attribute of "cgroup.events". */
+
+                r = cg_read_event(controller, path, "populated", &t);
+                if (r == -ENOENT)
+                        return true;
+                if (r < 0)
+                        return r;
+
+                return streq(t, "0");
+        } else {
+                _cleanup_closedir_ DIR *d = NULL;
+                char *fn;
+
+                r = cg_is_empty(controller, path);
+                if (r <= 0)
+                        return r;
+
+                r = cg_enumerate_subgroups(controller, path, &d);
+                if (r == -ENOENT)
+                        return true;
+                if (r < 0)
+                        return r;
+
+                while ((r = cg_read_subgroup(d, &fn)) > 0) {
+                        _cleanup_free_ char *p = NULL;
+
+                        p = strjoin(path, "/", fn);
+                        free(fn);
+                        if (!p)
+                                return -ENOMEM;
+
+                        r = cg_is_empty_recursive(controller, p);
+                        if (r <= 0)
+                                return r;
+                }
+                if (r < 0)
+                        return r;
+
+                return true;
+        }
+}
+
+int cg_split_spec(const char *spec, char **controller, char **path) {
+        char *t = NULL, *u = NULL;
+        const char *e;
+
+        assert(spec);
+
+        if (*spec == '/') {
+                if (!path_is_normalized(spec))
+                        return -EINVAL;
+
+                if (path) {
+                        t = strdup(spec);
+                        if (!t)
+                                return -ENOMEM;
+
+                        *path = path_simplify(t, false);
+                }
+
+                if (controller)
+                        *controller = NULL;
+
+                return 0;
+        }
+
+        e = strchr(spec, ':');
+        if (!e) {
+                if (!cg_controller_is_valid(spec))
+                        return -EINVAL;
+
+                if (controller) {
+                        t = strdup(spec);
+                        if (!t)
+                                return -ENOMEM;
+
+                        *controller = t;
+                }
+
+                if (path)
+                        *path = NULL;
+
+                return 0;
+        }
+
+        t = strndup(spec, e-spec);
+        if (!t)
+                return -ENOMEM;
+        if (!cg_controller_is_valid(t)) {
+                free(t);
+                return -EINVAL;
+        }
+
+        if (isempty(e+1))
+                u = NULL;
+        else {
+                u = strdup(e+1);
+                if (!u) {
+                        free(t);
+                        return -ENOMEM;
+                }
+
+                if (!path_is_normalized(u) ||
+                    !path_is_absolute(u)) {
+                        free(t);
+                        free(u);
+                        return -EINVAL;
+                }
+
+                path_simplify(u, false);
+        }
+
+        if (controller)
+                *controller = t;
+        else
+                free(t);
+
+        if (path)
+                *path = u;
+        else
+                free(u);
+
+        return 0;
+}
+
+int cg_mangle_path(const char *path, char **result) {
+        _cleanup_free_ char *c = NULL, *p = NULL;
+        char *t;
+        int r;
+
+        assert(path);
+        assert(result);
+
+        /* First, check if it already is a filesystem path */
+        if (path_startswith(path, "/sys/fs/cgroup")) {
+
+                t = strdup(path);
+                if (!t)
+                        return -ENOMEM;
+
+                *result = path_simplify(t, false);
+                return 0;
+        }
+
+        /* Otherwise, treat it as cg spec */
+        r = cg_split_spec(path, &c, &p);
+        if (r < 0)
+                return r;
+
+        return cg_get_path(c ?: SYSTEMD_CGROUP_CONTROLLER, p ?: "/", NULL, result);
+}
+
+int cg_get_root_path(char **path) {
+        char *p, *e;
+        int r;
+
+        assert(path);
+
+        r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, 1, &p);
+        if (r < 0)
+                return r;
+
+        e = endswith(p, "/" SPECIAL_INIT_SCOPE);
+        if (!e)
+                e = endswith(p, "/" SPECIAL_SYSTEM_SLICE); /* legacy */
+        if (!e)
+                e = endswith(p, "/system"); /* even more legacy */
+        if (e)
+                *e = 0;
+
+        *path = p;
+        return 0;
+}
+
+int cg_shift_path(const char *cgroup, const char *root, const char **shifted) {
+        _cleanup_free_ char *rt = NULL;
+        char *p;
+        int r;
+
+        assert(cgroup);
+        assert(shifted);
+
+        if (!root) {
+                /* If the root was specified let's use that, otherwise
+                 * let's determine it from PID 1 */
+
+                r = cg_get_root_path(&rt);
+                if (r < 0)
+                        return r;
+
+                root = rt;
+        }
+
+        p = path_startswith(cgroup, root);
+        if (p && p > cgroup)
+                *shifted = p - 1;
+        else
+                *shifted = cgroup;
+
+        return 0;
+}
+
+int cg_pid_get_path_shifted(pid_t pid, const char *root, char **cgroup) {
+        _cleanup_free_ char *raw = NULL;
+        const char *c;
+        int r;
+
+        assert(pid >= 0);
+        assert(cgroup);
+
+        r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &raw);
+        if (r < 0)
+                return r;
+
+        r = cg_shift_path(raw, root, &c);
+        if (r < 0)
+                return r;
+
+        if (c == raw)
+                *cgroup = TAKE_PTR(raw);
+        else {
+                char *n;
+
+                n = strdup(c);
+                if (!n)
+                        return -ENOMEM;
+
+                *cgroup = n;
+        }
+
+        return 0;
+}
+
+int cg_path_decode_unit(const char *cgroup, char **unit) {
+        char *c, *s;
+        size_t n;
+
+        assert(cgroup);
+        assert(unit);
+
+        n = strcspn(cgroup, "/");
+        if (n < 3)
+                return -ENXIO;
+
+        c = strndupa(cgroup, n);
+        c = cg_unescape(c);
+
+        if (!unit_name_is_valid(c, UNIT_NAME_PLAIN|UNIT_NAME_INSTANCE))
+                return -ENXIO;
+
+        s = strdup(c);
+        if (!s)
+                return -ENOMEM;
+
+        *unit = s;
+        return 0;
+}
+
+static bool valid_slice_name(const char *p, size_t n) {
+
+        if (!p)
+                return false;
+
+        if (n < STRLEN("x.slice"))
+                return false;
+
+        if (memcmp(p + n - 6, ".slice", 6) == 0) {
+                char buf[n+1], *c;
+
+                memcpy(buf, p, n);
+                buf[n] = 0;
+
+                c = cg_unescape(buf);
+
+                return unit_name_is_valid(c, UNIT_NAME_PLAIN);
+        }
+
+        return false;
+}
+
+static const char *skip_slices(const char *p) {
+        assert(p);
+
+        /* Skips over all slice assignments */
+
+        for (;;) {
+                size_t n;
+
+                p += strspn(p, "/");
+
+                n = strcspn(p, "/");
+                if (!valid_slice_name(p, n))
+                        return p;
+
+                p += n;
+        }
+}
+
+int cg_path_get_unit(const char *path, char **ret) {
+        const char *e;
+        char *unit;
+        int r;
+
+        assert(path);
+        assert(ret);
+
+        e = skip_slices(path);
+
+        r = cg_path_decode_unit(e, &unit);
+        if (r < 0)
+                return r;
+
+        /* We skipped over the slices, don't accept any now */
+        if (endswith(unit, ".slice")) {
+                free(unit);
+                return -ENXIO;
+        }
+
+        *ret = unit;
+        return 0;
+}
+
+int cg_pid_get_unit(pid_t pid, char **unit) {
+        _cleanup_free_ char *cgroup = NULL;
+        int r;
+
+        assert(unit);
+
+        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
+        if (r < 0)
+                return r;
+
+        return cg_path_get_unit(cgroup, unit);
+}
+
+/**
+ * Skip session-*.scope, but require it to be there.
+ */
+static const char *skip_session(const char *p) {
+        size_t n;
+
+        if (isempty(p))
+                return NULL;
+
+        p += strspn(p, "/");
+
+        n = strcspn(p, "/");
+        if (n < STRLEN("session-x.scope"))
+                return NULL;
+
+        if (memcmp(p, "session-", 8) == 0 && memcmp(p + n - 6, ".scope", 6) == 0) {
+                char buf[n - 8 - 6 + 1];
+
+                memcpy(buf, p + 8, n - 8 - 6);
+                buf[n - 8 - 6] = 0;
+
+                /* Note that session scopes never need unescaping,
+                 * since they cannot conflict with the kernel's own
+                 * names, hence we don't need to call cg_unescape()
+                 * here. */
+
+                if (!session_id_valid(buf))
+                        return false;
+
+                p += n;
+                p += strspn(p, "/");
+                return p;
+        }
+
+        return NULL;
+}
+
+/**
+ * Skip user@*.service, but require it to be there.
+ */
+static const char *skip_user_manager(const char *p) {
+        size_t n;
+
+        if (isempty(p))
+                return NULL;
+
+        p += strspn(p, "/");
+
+        n = strcspn(p, "/");
+        if (n < STRLEN("user@x.service"))
+                return NULL;
+
+        if (memcmp(p, "user@", 5) == 0 && memcmp(p + n - 8, ".service", 8) == 0) {
+                char buf[n - 5 - 8 + 1];
+
+                memcpy(buf, p + 5, n - 5 - 8);
+                buf[n - 5 - 8] = 0;
+
+                /* Note that user manager services never need unescaping,
+                 * since they cannot conflict with the kernel's own
+                 * names, hence we don't need to call cg_unescape()
+                 * here. */
+
+                if (parse_uid(buf, NULL) < 0)
+                        return NULL;
+
+                p += n;
+                p += strspn(p, "/");
+
+                return p;
+        }
+
+        return NULL;
+}
+
+static const char *skip_user_prefix(const char *path) {
+        const char *e, *t;
+
+        assert(path);
+
+        /* Skip slices, if there are any */
+        e = skip_slices(path);
+
+        /* Skip the user manager, if it's in the path now... */
+        t = skip_user_manager(e);
+        if (t)
+                return t;
+
+        /* Alternatively skip the user session if it is in the path... */
+        return skip_session(e);
+}
+
+int cg_path_get_user_unit(const char *path, char **ret) {
+        const char *t;
+
+        assert(path);
+        assert(ret);
+
+        t = skip_user_prefix(path);
+        if (!t)
+                return -ENXIO;
+
+        /* And from here on it looks pretty much the same as for a
+         * system unit, hence let's use the same parser from here
+         * on. */
+        return cg_path_get_unit(t, ret);
+}
+
+int cg_pid_get_user_unit(pid_t pid, char **unit) {
+        _cleanup_free_ char *cgroup = NULL;
+        int r;
+
+        assert(unit);
+
+        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
+        if (r < 0)
+                return r;
+
+        return cg_path_get_user_unit(cgroup, unit);
+}
+
+int cg_path_get_machine_name(const char *path, char **machine) {
+        _cleanup_free_ char *u = NULL;
+        const char *sl;
+        int r;
+
+        r = cg_path_get_unit(path, &u);
+        if (r < 0)
+                return r;
+
+        sl = strjoina("/run/systemd/machines/unit:", u);
+        return readlink_malloc(sl, machine);
+}
+
+int cg_pid_get_machine_name(pid_t pid, char **machine) {
+        _cleanup_free_ char *cgroup = NULL;
+        int r;
+
+        assert(machine);
+
+        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
+        if (r < 0)
+                return r;
+
+        return cg_path_get_machine_name(cgroup, machine);
+}
+
+int cg_path_get_session(const char *path, char **session) {
+        _cleanup_free_ char *unit = NULL;
+        char *start, *end;
+        int r;
+
+        assert(path);
+
+        r = cg_path_get_unit(path, &unit);
+        if (r < 0)
+                return r;
+
+        start = startswith(unit, "session-");
+        if (!start)
+                return -ENXIO;
+        end = endswith(start, ".scope");
+        if (!end)
+                return -ENXIO;
+
+        *end = 0;
+        if (!session_id_valid(start))
+                return -ENXIO;
+
+        if (session) {
+                char *rr;
+
+                rr = strdup(start);
+                if (!rr)
+                        return -ENOMEM;
+
+                *session = rr;
+        }
+
+        return 0;
+}
+
+int cg_pid_get_session(pid_t pid, char **session) {
+        _cleanup_free_ char *cgroup = NULL;
+        int r;
+
+        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
+        if (r < 0)
+                return r;
+
+        return cg_path_get_session(cgroup, session);
+}
+
+int cg_path_get_owner_uid(const char *path, uid_t *uid) {
+        _cleanup_free_ char *slice = NULL;
+        char *start, *end;
+        int r;
+
+        assert(path);
+
+        r = cg_path_get_slice(path, &slice);
+        if (r < 0)
+                return r;
+
+        start = startswith(slice, "user-");
+        if (!start)
+                return -ENXIO;
+        end = endswith(start, ".slice");
+        if (!end)
+                return -ENXIO;
+
+        *end = 0;
+        if (parse_uid(start, uid) < 0)
+                return -ENXIO;
+
+        return 0;
+}
+
+int cg_pid_get_owner_uid(pid_t pid, uid_t *uid) {
+        _cleanup_free_ char *cgroup = NULL;
+        int r;
+
+        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
+        if (r < 0)
+                return r;
+
+        return cg_path_get_owner_uid(cgroup, uid);
+}
+
+int cg_path_get_slice(const char *p, char **slice) {
+        const char *e = NULL;
+
+        assert(p);
+        assert(slice);
+
+        /* Finds the right-most slice unit from the beginning, but
+         * stops before we come to the first non-slice unit. */
+
+        for (;;) {
+                size_t n;
+
+                p += strspn(p, "/");
+
+                n = strcspn(p, "/");
+                if (!valid_slice_name(p, n)) {
+
+                        if (!e) {
+                                char *s;
+
+                                s = strdup(SPECIAL_ROOT_SLICE);
+                                if (!s)
+                                        return -ENOMEM;
+
+                                *slice = s;
+                                return 0;
+                        }
+
+                        return cg_path_decode_unit(e, slice);
+                }
+
+                e = p;
+                p += n;
+        }
+}
+
+int cg_pid_get_slice(pid_t pid, char **slice) {
+        _cleanup_free_ char *cgroup = NULL;
+        int r;
+
+        assert(slice);
+
+        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
+        if (r < 0)
+                return r;
+
+        return cg_path_get_slice(cgroup, slice);
+}
+
+int cg_path_get_user_slice(const char *p, char **slice) {
+        const char *t;
+        assert(p);
+        assert(slice);
+
+        t = skip_user_prefix(p);
+        if (!t)
+                return -ENXIO;
+
+        /* And now it looks pretty much the same as for a system
+         * slice, so let's just use the same parser from here on. */
+        return cg_path_get_slice(t, slice);
+}
+
+int cg_pid_get_user_slice(pid_t pid, char **slice) {
+        _cleanup_free_ char *cgroup = NULL;
+        int r;
+
+        assert(slice);
+
+        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
+        if (r < 0)
+                return r;
+
+        return cg_path_get_user_slice(cgroup, slice);
+}
+
+char *cg_escape(const char *p) {
+        bool need_prefix = false;
+
+        /* This implements very minimal escaping for names to be used
+         * as file names in the cgroup tree: any name which might
+         * conflict with a kernel name or is prefixed with '_' is
+         * prefixed with a '_'. That way, when reading cgroup names it
+         * is sufficient to remove a single prefixing underscore if
+         * there is one. */
+
+        /* The return value of this function (unlike cg_unescape())
+         * needs free()! */
+
+        if (IN_SET(p[0], 0, '_', '.') ||
+            STR_IN_SET(p, "notify_on_release", "release_agent", "tasks") ||
+            startswith(p, "cgroup."))
+                need_prefix = true;
+        else {
+                const char *dot;
+
+                dot = strrchr(p, '.');
+                if (dot) {
+                        CGroupController c;
+                        size_t l = dot - p;
+
+                        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                                const char *n;
+
+                                n = cgroup_controller_to_string(c);
+
+                                if (l != strlen(n))
+                                        continue;
+
+                                if (memcmp(p, n, l) != 0)
+                                        continue;
+
+                                need_prefix = true;
+                                break;
+                        }
+                }
+        }
+
+        if (need_prefix)
+                return strappend("_", p);
+
+        return strdup(p);
+}
+
+char *cg_unescape(const char *p) {
+        assert(p);
+
+        /* The return value of this function (unlike cg_escape())
+         * doesn't need free()! */
+
+        if (p[0] == '_')
+                return (char*) p+1;
+
+        return (char*) p;
+}
+
+#define CONTROLLER_VALID                        \
+        DIGITS LETTERS                          \
+        "_"
+
+bool cg_controller_is_valid(const char *p) {
+        const char *t, *s;
+
+        if (!p)
+                return false;
+
+        if (streq(p, SYSTEMD_CGROUP_CONTROLLER))
+                return true;
+
+        s = startswith(p, "name=");
+        if (s)
+                p = s;
+
+        if (IN_SET(*p, 0, '_'))
+                return false;
+
+        for (t = p; *t; t++)
+                if (!strchr(CONTROLLER_VALID, *t))
+                        return false;
+
+        if (t - p > FILENAME_MAX)
+                return false;
+
+        return true;
+}
+
+int cg_slice_to_path(const char *unit, char **ret) {
+        _cleanup_free_ char *p = NULL, *s = NULL, *e = NULL;
+        const char *dash;
+        int r;
+
+        assert(unit);
+        assert(ret);
+
+        if (streq(unit, SPECIAL_ROOT_SLICE)) {
+                char *x;
+
+                x = strdup("");
+                if (!x)
+                        return -ENOMEM;
+                *ret = x;
+                return 0;
+        }
+
+        if (!unit_name_is_valid(unit, UNIT_NAME_PLAIN))
+                return -EINVAL;
+
+        if (!endswith(unit, ".slice"))
+                return -EINVAL;
+
+        r = unit_name_to_prefix(unit, &p);
+        if (r < 0)
+                return r;
+
+        dash = strchr(p, '-');
+
+        /* Don't allow initial dashes */
+        if (dash == p)
+                return -EINVAL;
+
+        while (dash) {
+                _cleanup_free_ char *escaped = NULL;
+                char n[dash - p + sizeof(".slice")];
+
+#if HAS_FEATURE_MEMORY_SANITIZER
+                /* msan doesn't instrument stpncpy, so it thinks
+                 * n is later used unitialized:
+                 * https://github.com/google/sanitizers/issues/926
+                 */
+                zero(n);
+#endif
+
+                /* Don't allow trailing or double dashes */
+                if (IN_SET(dash[1], 0, '-'))
+                        return -EINVAL;
+
+                strcpy(stpncpy(n, p, dash - p), ".slice");
+                if (!unit_name_is_valid(n, UNIT_NAME_PLAIN))
+                        return -EINVAL;
+
+                escaped = cg_escape(n);
+                if (!escaped)
+                        return -ENOMEM;
+
+                if (!strextend(&s, escaped, "/", NULL))
+                        return -ENOMEM;
+
+                dash = strchr(dash+1, '-');
+        }
+
+        e = cg_escape(unit);
+        if (!e)
+                return -ENOMEM;
+
+        if (!strextend(&s, e, NULL))
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(s);
+
+        return 0;
+}
+
+int cg_set_attribute(const char *controller, const char *path, const char *attribute, const char *value) {
+        _cleanup_free_ char *p = NULL;
+        int r;
+
+        r = cg_get_path(controller, path, attribute, &p);
+        if (r < 0)
+                return r;
+
+        return write_string_file(p, value, WRITE_STRING_FILE_DISABLE_BUFFER);
+}
+
+int cg_get_attribute(const char *controller, const char *path, const char *attribute, char **ret) {
+        _cleanup_free_ char *p = NULL;
+        int r;
+
+        r = cg_get_path(controller, path, attribute, &p);
+        if (r < 0)
+                return r;
+
+        return read_one_line_file(p, ret);
+}
+
+int cg_get_keyed_attribute(
+                const char *controller,
+                const char *path,
+                const char *attribute,
+                char **keys,
+                char **ret_values) {
+
+        _cleanup_free_ char *filename = NULL, *contents = NULL;
+        const char *p;
+        size_t n, i, n_done = 0;
+        char **v;
+        int r;
+
+        /* Reads one or more fields of a cgroup v2 keyed attribute file. The 'keys' parameter should be an strv with
+         * all keys to retrieve. The 'ret_values' parameter should be passed as string size with the same number of
+         * entries as 'keys'. On success each entry will be set to the value of the matching key.
+         *
+         * If the attribute file doesn't exist at all returns ENOENT, if any key is not found returns ENXIO. */
+
+        r = cg_get_path(controller, path, attribute, &filename);
+        if (r < 0)
+                return r;
+
+        r = read_full_file(filename, &contents, NULL);
+        if (r < 0)
+                return r;
+
+        n = strv_length(keys);
+        if (n == 0) /* No keys to retrieve? That's easy, we are done then */
+                return 0;
+
+        /* Let's build this up in a temporary array for now in order not to clobber the return parameter on failure */
+        v = newa0(char*, n);
+
+        for (p = contents; *p;) {
+                const char *w = NULL;
+
+                for (i = 0; i < n; i++)
+                        if (!v[i]) {
+                                w = first_word(p, keys[i]);
+                                if (w)
+                                        break;
+                        }
+
+                if (w) {
+                        size_t l;
+
+                        l = strcspn(w, NEWLINE);
+                        v[i] = strndup(w, l);
+                        if (!v[i]) {
+                                r = -ENOMEM;
+                                goto fail;
+                        }
+
+                        n_done++;
+                        if (n_done >= n)
+                                goto done;
+
+                        p = w + l;
+                } else
+                        p += strcspn(p, NEWLINE);
+
+                p += strspn(p, NEWLINE);
+        }
+
+        r = -ENXIO;
+
+fail:
+        for (i = 0; i < n; i++)
+                free(v[i]);
+
+        return r;
+
+done:
+        memcpy(ret_values, v, sizeof(char*) * n);
+        return 0;
+
+}
+
+int cg_create_everywhere(CGroupMask supported, CGroupMask mask, const char *path) {
+        CGroupController c;
+        CGroupMask done;
+        bool created;
+        int r;
+
+        /* This one will create a cgroup in our private tree, but also
+         * duplicate it in the trees specified in mask, and remove it
+         * in all others.
+         *
+         * Returns 0 if the group already existed in the systemd hierarchy,
+         * 1 on success, negative otherwise.
+         */
+
+        /* First create the cgroup in our own hierarchy. */
+        r = cg_create(SYSTEMD_CGROUP_CONTROLLER, path);
+        if (r < 0)
+                return r;
+        created = r;
+
+        /* If we are in the unified hierarchy, we are done now */
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return created;
+
+        supported &= CGROUP_MASK_V1;
+        mask = CGROUP_MASK_EXTEND_JOINED(mask);
+        done = 0;
+
+        /* Otherwise, do the same in the other hierarchies */
+        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+                const char *n;
+
+                if (!FLAGS_SET(supported, bit))
+                        continue;
+
+                if (FLAGS_SET(done, bit))
+                        continue;
+
+                n = cgroup_controller_to_string(c);
+                if (FLAGS_SET(mask, bit))
+                        (void) cg_create(n, path);
+                else
+                        (void) cg_trim(n, path, true);
+
+                done |= CGROUP_MASK_EXTEND_JOINED(bit);
+        }
+
+        return created;
+}
+
+int cg_attach_everywhere(CGroupMask supported, const char *path, pid_t pid, cg_migrate_callback_t path_callback, void *userdata) {
+        CGroupController c;
+        CGroupMask done;
+        int r;
+
+        r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, path, pid);
+        if (r < 0)
+                return r;
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return 0;
+
+        supported &= CGROUP_MASK_V1;
+        done = 0;
+
+        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+                const char *p = NULL;
+
+                if (!FLAGS_SET(supported, bit))
+                        continue;
+
+                if (FLAGS_SET(done, bit))
+                        continue;
+
+                if (path_callback)
+                        p = path_callback(bit, userdata);
+                if (!p)
+                        p = path;
+
+                (void) cg_attach_fallback(cgroup_controller_to_string(c), p, pid);
+                done |= CGROUP_MASK_EXTEND_JOINED(bit);
+        }
+
+        return 0;
+}
+
+int cg_attach_many_everywhere(CGroupMask supported, const char *path, Set* pids, cg_migrate_callback_t path_callback, void *userdata) {
+        Iterator i;
+        void *pidp;
+        int r = 0;
+
+        SET_FOREACH(pidp, pids, i) {
+                pid_t pid = PTR_TO_PID(pidp);
+                int q;
+
+                q = cg_attach_everywhere(supported, path, pid, path_callback, userdata);
+                if (q < 0 && r >= 0)
+                        r = q;
+        }
+
+        return r;
+}
+
+int cg_migrate_everywhere(CGroupMask supported, const char *from, const char *to, cg_migrate_callback_t to_callback, void *userdata) {
+        CGroupController c;
+        CGroupMask done;
+        int r = 0, q;
+
+        if (!path_equal(from, to))  {
+                r = cg_migrate_recursive(SYSTEMD_CGROUP_CONTROLLER, from, SYSTEMD_CGROUP_CONTROLLER, to, CGROUP_REMOVE);
+                if (r < 0)
+                        return r;
+        }
+
+        q = cg_all_unified();
+        if (q < 0)
+                return q;
+        if (q > 0)
+                return r;
+
+        supported &= CGROUP_MASK_V1;
+        done = 0;
+
+        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+                const char *p = NULL;
+
+                if (!FLAGS_SET(supported, bit))
+                        continue;
+
+                if (FLAGS_SET(done, bit))
+                        continue;
+
+                if (to_callback)
+                        p = to_callback(bit, userdata);
+                if (!p)
+                        p = to;
+
+                (void) cg_migrate_recursive_fallback(SYSTEMD_CGROUP_CONTROLLER, to, cgroup_controller_to_string(c), p, 0);
+                done |= CGROUP_MASK_EXTEND_JOINED(bit);
+        }
+
+        return r;
+}
+
+int cg_trim_everywhere(CGroupMask supported, const char *path, bool delete_root) {
+        CGroupController c;
+        CGroupMask done;
+        int r, q;
+
+        r = cg_trim(SYSTEMD_CGROUP_CONTROLLER, path, delete_root);
+        if (r < 0)
+                return r;
+
+        q = cg_all_unified();
+        if (q < 0)
+                return q;
+        if (q > 0)
+                return r;
+
+        supported &= CGROUP_MASK_V1;
+        done = 0;
+
+        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+
+                if (!FLAGS_SET(supported, bit))
+                        continue;
+
+                if (FLAGS_SET(done, bit))
+                        continue;
+
+                (void) cg_trim(cgroup_controller_to_string(c), path, delete_root);
+                done |= CGROUP_MASK_EXTEND_JOINED(bit);
+        }
+
+        return r;
+}
+
+int cg_mask_to_string(CGroupMask mask, char **ret) {
+        _cleanup_free_ char *s = NULL;
+        size_t n = 0, allocated = 0;
+        bool space = false;
+        CGroupController c;
+
+        assert(ret);
+
+        if (mask == 0) {
+                *ret = NULL;
+                return 0;
+        }
+
+        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                const char *k;
+                size_t l;
+
+                if (!FLAGS_SET(mask, CGROUP_CONTROLLER_TO_MASK(c)))
+                        continue;
+
+                k = cgroup_controller_to_string(c);
+                l = strlen(k);
+
+                if (!GREEDY_REALLOC(s, allocated, n + space + l + 1))
+                        return -ENOMEM;
+
+                if (space)
+                        s[n] = ' ';
+                memcpy(s + n + space, k, l);
+                n += space + l;
+
+                space = true;
+        }
+
+        assert(s);
+
+        s[n] = 0;
+        *ret = TAKE_PTR(s);
+
+        return 0;
+}
+
+int cg_mask_from_string(const char *value, CGroupMask *ret) {
+        CGroupMask m = 0;
+
+        assert(ret);
+        assert(value);
+
+        for (;;) {
+                _cleanup_free_ char *n = NULL;
+                CGroupController v;
+                int r;
+
+                r = extract_first_word(&value, &n, NULL, 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                v = cgroup_controller_from_string(n);
+                if (v < 0)
+                        continue;
+
+                m |= CGROUP_CONTROLLER_TO_MASK(v);
+        }
+
+        *ret = m;
+        return 0;
+}
+
+int cg_mask_supported(CGroupMask *ret) {
+        CGroupMask mask;
+        int r;
+
+        /* Determines the mask of supported cgroup controllers. Only includes controllers we can make sense of and that
+         * are actually accessible. Only covers real controllers, i.e. not the CGROUP_CONTROLLER_BPF_xyz
+         * pseudo-controllers. */
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                _cleanup_free_ char *root = NULL, *controllers = NULL, *path = NULL;
+
+                /* In the unified hierarchy we can read the supported
+                 * and accessible controllers from a the top-level
+                 * cgroup attribute */
+
+                r = cg_get_root_path(&root);
+                if (r < 0)
+                        return r;
+
+                r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, root, "cgroup.controllers", &path);
+                if (r < 0)
+                        return r;
+
+                r = read_one_line_file(path, &controllers);
+                if (r < 0)
+                        return r;
+
+                r = cg_mask_from_string(controllers, &mask);
+                if (r < 0)
+                        return r;
+
+                /* Currently, we support the cpu, memory, io and pids controller in the unified hierarchy, mask
+                 * everything else off. */
+                mask &= CGROUP_MASK_V2;
+
+        } else {
+                CGroupController c;
+
+                /* In the legacy hierarchy, we check which hierarchies are mounted. */
+
+                mask = 0;
+                for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                        CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+                        const char *n;
+
+                        if (!FLAGS_SET(CGROUP_MASK_V1, bit))
+                                continue;
+
+                        n = cgroup_controller_to_string(c);
+                        if (controller_is_accessible(n) >= 0)
+                                mask |= bit;
+                }
+        }
+
+        *ret = mask;
+        return 0;
+}
+
+int cg_kernel_controllers(Set **ret) {
+        _cleanup_set_free_free_ Set *controllers = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
+        int r;
+
+        assert(ret);
+
+        /* Determines the full list of kernel-known controllers. Might include controllers we don't actually support
+         * and controllers that aren't currently accessible (because not mounted). This does not include "name="
+         * pseudo-controllers. */
+
+        controllers = set_new(&string_hash_ops);
+        if (!controllers)
+                return -ENOMEM;
+
+        f = fopen("/proc/cgroups", "re");
+        if (!f) {
+                if (errno == ENOENT) {
+                        *ret = NULL;
+                        return 0;
+                }
+
+                return -errno;
+        }
+
+        (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
+
+        /* Ignore the header line */
+        (void) read_line(f, (size_t) -1, NULL);
+
+        for (;;) {
+                char *controller;
+                int enabled = 0;
+
+                errno = 0;
+                if (fscanf(f, "%ms %*i %*i %i", &controller, &enabled) != 2) {
+
+                        if (feof(f))
+                                break;
+
+                        if (ferror(f) && errno > 0)
+                                return -errno;
+
+                        return -EBADMSG;
+                }
+
+                if (!enabled) {
+                        free(controller);
+                        continue;
+                }
+
+                if (!cg_controller_is_valid(controller)) {
+                        free(controller);
+                        return -EBADMSG;
+                }
+
+                r = set_consume(controllers, controller);
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(controllers);
+
+        return 0;
+}
+
+static thread_local CGroupUnified unified_cache = CGROUP_UNIFIED_UNKNOWN;
+
+/* The hybrid mode was initially implemented in v232 and simply mounted cgroup2 on /sys/fs/cgroup/systemd.  This
+ * unfortunately broke other tools (such as docker) which expected the v1 "name=systemd" hierarchy on
+ * /sys/fs/cgroup/systemd.  From v233 and on, the hybrid mode mountnbs v2 on /sys/fs/cgroup/unified and maintains
+ * "name=systemd" hierarchy on /sys/fs/cgroup/systemd for compatibility with other tools.
+ *
+ * To keep live upgrade working, we detect and support v232 layout.  When v232 layout is detected, to keep cgroup v2
+ * process management but disable the compat dual layout, we return %true on
+ * cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) and %false on cg_hybrid_unified().
+ */
+static thread_local bool unified_systemd_v232;
+
+static int cg_unified_update(void) {
+
+        struct statfs fs;
+
+        /* Checks if we support the unified hierarchy. Returns an
+         * error when the cgroup hierarchies aren't mounted yet or we
+         * have any other trouble determining if the unified hierarchy
+         * is supported. */
+
+        if (unified_cache >= CGROUP_UNIFIED_NONE)
+                return 0;
+
+        if (statfs("/sys/fs/cgroup/", &fs) < 0)
+                return log_debug_errno(errno, "statfs(\"/sys/fs/cgroup/\") failed: %m");
+
+        if (F_TYPE_EQUAL(fs.f_type, CGROUP2_SUPER_MAGIC)) {
+                log_debug("Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy");
+                unified_cache = CGROUP_UNIFIED_ALL;
+        } else if (F_TYPE_EQUAL(fs.f_type, TMPFS_MAGIC)) {
+                if (statfs("/sys/fs/cgroup/unified/", &fs) == 0 &&
+                    F_TYPE_EQUAL(fs.f_type, CGROUP2_SUPER_MAGIC)) {
+                        log_debug("Found cgroup2 on /sys/fs/cgroup/unified, unified hierarchy for systemd controller");
+                        unified_cache = CGROUP_UNIFIED_SYSTEMD;
+                        unified_systemd_v232 = false;
+                } else {
+                        if (statfs("/sys/fs/cgroup/systemd/", &fs) < 0)
+                                return log_debug_errno(errno, "statfs(\"/sys/fs/cgroup/systemd\" failed: %m");
+
+                        if (F_TYPE_EQUAL(fs.f_type, CGROUP2_SUPER_MAGIC)) {
+                                log_debug("Found cgroup2 on /sys/fs/cgroup/systemd, unified hierarchy for systemd controller (v232 variant)");
+                                unified_cache = CGROUP_UNIFIED_SYSTEMD;
+                                unified_systemd_v232 = true;
+                        } else if (F_TYPE_EQUAL(fs.f_type, CGROUP_SUPER_MAGIC)) {
+                                log_debug("Found cgroup on /sys/fs/cgroup/systemd, legacy hierarchy");
+                                unified_cache = CGROUP_UNIFIED_NONE;
+                        } else {
+                                log_debug("Unexpected filesystem type %llx mounted on /sys/fs/cgroup/systemd, assuming legacy hierarchy",
+                                          (unsigned long long) fs.f_type);
+                                unified_cache = CGROUP_UNIFIED_NONE;
+                        }
+                }
+        } else
+                return log_debug_errno(SYNTHETIC_ERRNO(ENOMEDIUM),
+                                       "Unknown filesystem type %llx mounted on /sys/fs/cgroup.",
+                                       (unsigned long long)fs.f_type);
+
+        return 0;
+}
+
+int cg_unified_controller(const char *controller) {
+        int r;
+
+        r = cg_unified_update();
+        if (r < 0)
+                return r;
+
+        if (unified_cache == CGROUP_UNIFIED_NONE)
+                return false;
+
+        if (unified_cache >= CGROUP_UNIFIED_ALL)
+                return true;
+
+        return streq_ptr(controller, SYSTEMD_CGROUP_CONTROLLER);
+}
+
+int cg_all_unified(void) {
+        int r;
+
+        r = cg_unified_update();
+        if (r < 0)
+                return r;
+
+        return unified_cache >= CGROUP_UNIFIED_ALL;
+}
+
+int cg_hybrid_unified(void) {
+        int r;
+
+        r = cg_unified_update();
+        if (r < 0)
+                return r;
+
+        return unified_cache == CGROUP_UNIFIED_SYSTEMD && !unified_systemd_v232;
+}
+
+int cg_unified_flush(void) {
+        unified_cache = CGROUP_UNIFIED_UNKNOWN;
+
+        return cg_unified_update();
+}
+
+int cg_enable_everywhere(
+                CGroupMask supported,
+                CGroupMask mask,
+                const char *p,
+                CGroupMask *ret_result_mask) {
+
+        _cleanup_fclose_ FILE *f = NULL;
+        _cleanup_free_ char *fs = NULL;
+        CGroupController c;
+        CGroupMask ret = 0;
+        int r;
+
+        assert(p);
+
+        if (supported == 0) {
+                if (ret_result_mask)
+                        *ret_result_mask = 0;
+                return 0;
+        }
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                /* On the legacy hiearchy there's no concept of "enabling" controllers in cgroups defined. Let's claim
+                 * complete success right away. (If you wonder why we return the full mask here, rather than zero: the
+                 * caller tends to use the returned mask later on to compare if all controllers where properly joined,
+                 * and if not requeues realization. This use is the primary purpose of the return value, hence let's
+                 * minimize surprises here and reduce triggers for re-realization by always saying we fully
+                 * succeeded.) */
+                if (ret_result_mask)
+                        *ret_result_mask = mask & supported & CGROUP_MASK_V2; /* If you wonder why we mask this with
+                                                                               * CGROUP_MASK_V2: The 'supported' mask
+                                                                               * might contain pure-V1 or BPF
+                                                                               * controllers, and we never want to
+                                                                               * claim that we could enable those with
+                                                                               * cgroup.subtree_control */
+                return 0;
+        }
+
+        r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, p, "cgroup.subtree_control", &fs);
+        if (r < 0)
+                return r;
+
+        for (c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
+                CGroupMask bit = CGROUP_CONTROLLER_TO_MASK(c);
+                const char *n;
+
+                if (!FLAGS_SET(CGROUP_MASK_V2, bit))
+                        continue;
+
+                if (!FLAGS_SET(supported, bit))
+                        continue;
+
+                n = cgroup_controller_to_string(c);
+                {
+                        char s[1 + strlen(n) + 1];
+
+                        s[0] = FLAGS_SET(mask, bit) ? '+' : '-';
+                        strcpy(s + 1, n);
+
+                        if (!f) {
+                                f = fopen(fs, "we");
+                                if (!f)
+                                        return log_debug_errno(errno, "Failed to open cgroup.subtree_control file of %s: %m", p);
+                        }
+
+                        r = write_string_stream(f, s, WRITE_STRING_FILE_DISABLE_BUFFER);
+                        if (r < 0) {
+                                log_debug_errno(r, "Failed to %s controller %s for %s (%s): %m",
+                                                FLAGS_SET(mask, bit) ? "enable" : "disable", n, p, fs);
+                                clearerr(f);
+
+                                /* If we can't turn off a controller, leave it on in the reported resulting mask. This
+                                 * happens for example when we attempt to turn off a controller up in the tree that is
+                                 * used down in the tree. */
+                                if (!FLAGS_SET(mask, bit) && r == -EBUSY) /* You might wonder why we check for EBUSY
+                                                                           * only here, and not follow the same logic
+                                                                           * for other errors such as EINVAL or
+                                                                           * EOPNOTSUPP or anything else. That's
+                                                                           * because EBUSY indicates that the
+                                                                           * controllers is currently enabled and
+                                                                           * cannot be disabled because something down
+                                                                           * the hierarchy is still using it. Any other
+                                                                           * error most likely means something like "I
+                                                                           * never heard of this controller" or
+                                                                           * similar. In the former case it's hence
+                                                                           * safe to assume the controller is still on
+                                                                           * after the failed operation, while in the
+                                                                           * latter case it's safer to assume the
+                                                                           * controller is unknown and hence certainly
+                                                                           * not enabled. */
+                                        ret |= bit;
+                        } else {
+                                /* Otherwise, if we managed to turn on a controller, set the bit reflecting that. */
+                                if (FLAGS_SET(mask, bit))
+                                        ret |= bit;
+                        }
+                }
+        }
+
+        /* Let's return the precise set of controllers now enabled for the cgroup. */
+        if (ret_result_mask)
+                *ret_result_mask = ret;
+
+        return 0;
+}
+
+bool cg_is_unified_wanted(void) {
+        static thread_local int wanted = -1;
+        int r;
+        bool b;
+        const bool is_default = DEFAULT_HIERARCHY == CGROUP_UNIFIED_ALL;
+        _cleanup_free_ char *c = NULL;
+
+        /* If we have a cached value, return that. */
+        if (wanted >= 0)
+                return wanted;
+
+        /* If the hierarchy is already mounted, then follow whatever
+         * was chosen for it. */
+        if (cg_unified_flush() >= 0)
+                return (wanted = unified_cache >= CGROUP_UNIFIED_ALL);
+
+        /* If we were explicitly passed systemd.unified_cgroup_hierarchy,
+         * respect that. */
+        r = proc_cmdline_get_bool("systemd.unified_cgroup_hierarchy", &b);
+        if (r > 0)
+                return (wanted = b);
+
+        /* If we passed cgroup_no_v1=all with no other instructions, it seems
+         * highly unlikely that we want to use hybrid or legacy hierarchy. */
+        r = proc_cmdline_get_key("cgroup_no_v1", 0, &c);
+        if (r > 0 && streq_ptr(c, "all"))
+                return (wanted = true);
+
+        return (wanted = is_default);
+}
+
+bool cg_is_legacy_wanted(void) {
+        static thread_local int wanted = -1;
+
+        /* If we have a cached value, return that. */
+        if (wanted >= 0)
+                return wanted;
+
+        /* Check if we have cgroup v2 already mounted. */
+        if (cg_unified_flush() >= 0 &&
+            unified_cache == CGROUP_UNIFIED_ALL)
+                return (wanted = false);
+
+        /* Otherwise, assume that at least partial legacy is wanted,
+         * since cgroup v2 should already be mounted at this point. */
+        return (wanted = true);
+}
+
+bool cg_is_hybrid_wanted(void) {
+        static thread_local int wanted = -1;
+        int r;
+        bool b;
+        const bool is_default = DEFAULT_HIERARCHY >= CGROUP_UNIFIED_SYSTEMD;
+        /* We default to true if the default is "hybrid", obviously,
+         * but also when the default is "unified", because if we get
+         * called, it means that unified hierarchy was not mounted. */
+
+        /* If we have a cached value, return that. */
+        if (wanted >= 0)
+                return wanted;
+
+        /* If the hierarchy is already mounted, then follow whatever
+         * was chosen for it. */
+        if (cg_unified_flush() >= 0 &&
+            unified_cache == CGROUP_UNIFIED_ALL)
+                return (wanted = false);
+
+        /* Otherwise, let's see what the kernel command line has to say.
+         * Since checking is expensive, cache a non-error result. */
+        r = proc_cmdline_get_bool("systemd.legacy_systemd_cgroup_controller", &b);
+
+        /* The meaning of the kernel option is reversed wrt. to the return value
+         * of this function, hence the negation. */
+        return (wanted = r > 0 ? !b : is_default);
+}
+
+int cg_weight_parse(const char *s, uint64_t *ret) {
+        uint64_t u;
+        int r;
+
+        if (isempty(s)) {
+                *ret = CGROUP_WEIGHT_INVALID;
+                return 0;
+        }
+
+        r = safe_atou64(s, &u);
+        if (r < 0)
+                return r;
+
+        if (u < CGROUP_WEIGHT_MIN || u > CGROUP_WEIGHT_MAX)
+                return -ERANGE;
+
+        *ret = u;
+        return 0;
+}
+
+const uint64_t cgroup_io_limit_defaults[_CGROUP_IO_LIMIT_TYPE_MAX] = {
+        [CGROUP_IO_RBPS_MAX]    = CGROUP_LIMIT_MAX,
+        [CGROUP_IO_WBPS_MAX]    = CGROUP_LIMIT_MAX,
+        [CGROUP_IO_RIOPS_MAX]   = CGROUP_LIMIT_MAX,
+        [CGROUP_IO_WIOPS_MAX]   = CGROUP_LIMIT_MAX,
+};
+
+static const char* const cgroup_io_limit_type_table[_CGROUP_IO_LIMIT_TYPE_MAX] = {
+        [CGROUP_IO_RBPS_MAX]    = "IOReadBandwidthMax",
+        [CGROUP_IO_WBPS_MAX]    = "IOWriteBandwidthMax",
+        [CGROUP_IO_RIOPS_MAX]   = "IOReadIOPSMax",
+        [CGROUP_IO_WIOPS_MAX]   = "IOWriteIOPSMax",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(cgroup_io_limit_type, CGroupIOLimitType);
+
+int cg_cpu_shares_parse(const char *s, uint64_t *ret) {
+        uint64_t u;
+        int r;
+
+        if (isempty(s)) {
+                *ret = CGROUP_CPU_SHARES_INVALID;
+                return 0;
+        }
+
+        r = safe_atou64(s, &u);
+        if (r < 0)
+                return r;
+
+        if (u < CGROUP_CPU_SHARES_MIN || u > CGROUP_CPU_SHARES_MAX)
+                return -ERANGE;
+
+        *ret = u;
+        return 0;
+}
+
+int cg_blkio_weight_parse(const char *s, uint64_t *ret) {
+        uint64_t u;
+        int r;
+
+        if (isempty(s)) {
+                *ret = CGROUP_BLKIO_WEIGHT_INVALID;
+                return 0;
+        }
+
+        r = safe_atou64(s, &u);
+        if (r < 0)
+                return r;
+
+        if (u < CGROUP_BLKIO_WEIGHT_MIN || u > CGROUP_BLKIO_WEIGHT_MAX)
+                return -ERANGE;
+
+        *ret = u;
+        return 0;
+}
+
+bool is_cgroup_fs(const struct statfs *s) {
+        return is_fs_type(s, CGROUP_SUPER_MAGIC) ||
+               is_fs_type(s, CGROUP2_SUPER_MAGIC);
+}
+
+bool fd_is_cgroup_fs(int fd) {
+        struct statfs s;
+
+        if (fstatfs(fd, &s) < 0)
+                return -errno;
+
+        return is_cgroup_fs(&s);
+}
+
+static const char *cgroup_controller_table[_CGROUP_CONTROLLER_MAX] = {
+        [CGROUP_CONTROLLER_CPU] = "cpu",
+        [CGROUP_CONTROLLER_CPUACCT] = "cpuacct",
+        [CGROUP_CONTROLLER_IO] = "io",
+        [CGROUP_CONTROLLER_BLKIO] = "blkio",
+        [CGROUP_CONTROLLER_MEMORY] = "memory",
+        [CGROUP_CONTROLLER_DEVICES] = "devices",
+        [CGROUP_CONTROLLER_PIDS] = "pids",
+        [CGROUP_CONTROLLER_BPF_FIREWALL] = "bpf-firewall",
+        [CGROUP_CONTROLLER_BPF_DEVICES] = "bpf-devices",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(cgroup_controller, CGroupController);
+
+CGroupMask get_cpu_accounting_mask(void) {
+        static CGroupMask needed_mask = (CGroupMask) -1;
+
+        /* On kernel ≥4.15 with unified hierarchy, cpu.stat's usage_usec is
+         * provided externally from the CPU controller, which means we don't
+         * need to enable the CPU controller just to get metrics. This is good,
+         * because enabling the CPU controller comes at a minor performance
+         * hit, especially when it's propagated deep into large hierarchies.
+         * There's also no separate CPU accounting controller available within
+         * a unified hierarchy.
+         *
+         * This combination of factors results in the desired cgroup mask to
+         * enable for CPU accounting varying as follows:
+         *
+         *                   ╔═════════════════════╤═════════════════════╗
+         *                   ║     Linux ≥4.15     │     Linux <4.15     ║
+         *   ╔═══════════════╬═════════════════════╪═════════════════════╣
+         *   ║ Unified       ║ nothing             │ CGROUP_MASK_CPU     ║
+         *   ╟───────────────╫─────────────────────┼─────────────────────╢
+         *   ║ Hybrid/Legacy ║ CGROUP_MASK_CPUACCT │ CGROUP_MASK_CPUACCT ║
+         *   ╚═══════════════╩═════════════════════╧═════════════════════╝
+         *
+         * We check kernel version here instead of manually checking whether
+         * cpu.stat is present for every cgroup, as that check in itself would
+         * already be fairly expensive.
+         *
+         * Kernels where this patch has been backported will therefore have the
+         * CPU controller enabled unnecessarily. This is more expensive than
+         * necessary, but harmless. ☺️
+         */
+
+        if (needed_mask == (CGroupMask) -1) {
+                if (cg_all_unified()) {
+                        struct utsname u;
+                        assert_se(uname(&u) >= 0);
+
+                        if (str_verscmp(u.release, "4.15") < 0)
+                                needed_mask = CGROUP_MASK_CPU;
+                        else
+                                needed_mask = 0;
+                } else
+                        needed_mask = CGROUP_MASK_CPUACCT;
+        }
+
+        return needed_mask;
+}
+
+bool cpu_accounting_is_cheap(void) {
+        return get_cpu_accounting_mask() == 0;
+}