Adding upstream version 252.22.upstream/252.22

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

1 files changed, 2309 insertions, 0 deletions

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
new file mode 100644
index 0000000..0b4731f
--- /dev/null
+++ b/src/basic/cgroup-util.c
@@ -0,0 +1,2309 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <limits.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdlib.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_magic.h"
+#include "missing_threads.h"
+#include "mkdir.h"
+#include "parse-util.h"
+#include "path-util.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"
+#include "xattr-util.h"
+
+static int cg_enumerate_items(const char *controller, const char *path, FILE **_f, const char *item) {
+        _cleanup_free_ char *fs = NULL;
+        FILE *f;
+        int r;
+
+        assert(_f);
+
+        r = cg_get_path(controller, path, item, &fs);
+        if (r < 0)
+                return r;
+
+        f = fopen(fs, "re");
+        if (!f)
+                return -errno;
+
+        *_f = f;
+        return 0;
+}
+
+int cg_enumerate_processes(const char *controller, const char *path, FILE **_f) {
+        return cg_enumerate_items(controller, path, _f, "cgroup.procs");
+}
+
+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_or_else(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 **ret) {
+
+        _cleanup_free_ char *events = NULL, *content = NULL;
+        int r;
+
+        r = cg_get_path(controller, path, "cgroup.events", &events);
+        if (r < 0)
+                return r;
+
+        r = read_full_virtual_file(events, &content, NULL);
+        if (r < 0)
+                return r;
+
+        for (const char *p = content;;) {
+                _cleanup_free_ char *line = NULL, *key = NULL, *val = NULL;
+                const char *q;
+
+                r = extract_first_word(&p, &line, "\n", 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENOENT;
+
+                q = line;
+                r = extract_first_word(&q, &key, " ", 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -EINVAL;
+
+                if (!streq(key, event))
+                        continue;
+
+                val = strdup(q);
+                if (!val)
+                        return -ENOMEM;
+
+                *ret = TAKE_PTR(val);
+                return 0;
+        }
+}
+
+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;
+}
+
+bool cg_freezer_supported(void) {
+        static thread_local int supported = -1;
+
+        if (supported >= 0)
+                return supported;
+
+        supported = cg_all_unified() > 0 && access("/sys/fs/cgroup/init.scope/cgroup.freeze", F_OK) == 0;
+
+        return supported;
+}
+
+bool cg_kill_supported(void) {
+        static thread_local int supported = -1;
+
+        if (supported >= 0)
+                return supported;
+
+        if (cg_all_unified() <= 0)
+                supported = false;
+        else if (access("/sys/fs/cgroup/init.scope/cgroup.kill", F_OK) < 0) {
+                if (errno != ENOENT)
+                        log_debug_errno(errno, "Failed to check if cgroup.kill is available, assuming not: %m");
+                supported = false;
+        } else
+                supported = true;
+
+        return supported;
+}
+
+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) {
+        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;
+}
+
+static int cg_kill_items(
+                const char *controller,
+                const char *path,
+                int sig,
+                CGroupFlags flags,
+                Set *s,
+                cg_kill_log_func_t log_kill,
+                void *userdata,
+                const char *item) {
+
+        _cleanup_set_free_ Set *allocated_set = NULL;
+        bool done = false;
+        int r, ret = 0, ret_log_kill = 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_items(controller, path, &f, item);
+                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)
+                                ret_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) {
+                                        if (log_kill)
+                                                ret = ret_log_kill;
+                                        else
+                                                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(
+                const char *controller,
+                const char *path,
+                int sig,
+                CGroupFlags flags,
+                Set *s,
+                cg_kill_log_func_t log_kill,
+                void *userdata) {
+
+        int r, ret;
+
+        r = cg_kill_items(controller, path, sig, flags, s, log_kill, userdata, "cgroup.procs");
+        if (r < 0 || sig != SIGKILL)
+                return r;
+
+        ret = r;
+
+        /* Only in case of killing with SIGKILL and when using cgroupsv2, kill remaining threads manually as
+           a workaround for kernel bug. It was fixed in 5.2-rc5 (c03cd7738a83), backported to 4.19.66
+           (4340d175b898) and 4.14.138 (feb6b123b7dd). */
+        r = cg_unified_controller(controller);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return ret;
+
+        r = cg_kill_items(controller, path, sig, flags, s, log_kill, userdata, "cgroup.threads");
+        if (r < 0)
+                return r;
+
+        return r > 0 || ret > 0;
+}
+
+int cg_kill_kernel_sigkill(const char *controller, const char *path) {
+        /* Kills the cgroup at `path` directly by writing to its cgroup.kill file.
+         * This sends SIGKILL to all processes in the cgroup and has the advantage of
+         * being completely atomic, unlike cg_kill_items. */
+        int r;
+        _cleanup_free_ char *killfile = NULL;
+
+        assert(path);
+
+        if (!cg_kill_supported())
+                return -EOPNOTSUPP;
+
+        r = cg_get_path(controller, path, "cgroup.kill", &killfile);
+        if (r < 0)
+                return r;
+
+        r = write_string_file(killfile, "1", WRITE_STRING_FILE_DISABLE_BUFFER);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+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 (sig == SIGKILL && cg_kill_supported() &&
+            !FLAGS_SET(flags, CGROUP_IGNORE_SELF) && !s && !log_kill) {
+                /* ignore CGROUP_SIGCONT, since this is a no-op alongside SIGKILL */
+                ret = cg_kill_kernel_sigkill(controller, path);
+                if (ret < 0)
+                        return ret;
+        } else {
+                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 = path_join(empty_to_root(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_SET(flags, CGROUP_REMOVE)) {
+                r = cg_rmdir(controller, path);
+                if (r < 0 && ret >= 0 && !IN_SET(r, -ENOENT, -EBUSY))
+                        return r;
+        }
+
+        return ret;
+}
+
+static const char *controller_to_dirname(const char *controller) {
+        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;
+        }
+
+        return startswith(controller, "name=") ?: controller;
+}
+
+static int join_path_legacy(const char *controller, const char *path, const char *suffix, char **ret) {
+        const char *dn;
+        char *t = NULL;
+
+        assert(ret);
+        assert(controller);
+
+        dn = controller_to_dirname(controller);
+
+        if (isempty(path) && isempty(suffix))
+                t = path_join("/sys/fs/cgroup", dn);
+        else if (isempty(path))
+                t = path_join("/sys/fs/cgroup", dn, suffix);
+        else if (isempty(suffix))
+                t = path_join("/sys/fs/cgroup", dn, path);
+        else
+                t = path_join("/sys/fs/cgroup", dn, path, suffix);
+        if (!t)
+                return -ENOMEM;
+
+        *ret = t;
+        return 0;
+}
+
+static int join_path_unified(const char *path, const char *suffix, char **ret) {
+        char *t;
+
+        assert(ret);
+
+        if (isempty(path) && isempty(suffix))
+                t = strdup("/sys/fs/cgroup");
+        else if (isempty(path))
+                t = path_join("/sys/fs/cgroup", suffix);
+        else if (isempty(suffix))
+                t = path_join("/sys/fs/cgroup", path);
+        else
+                t = path_join("/sys/fs/cgroup", path, suffix);
+        if (!t)
+                return -ENOMEM;
+
+        *ret = t;
+        return 0;
+}
+
+int cg_get_path(const char *controller, const char *path, const char *suffix, char **ret) {
+        int r;
+
+        assert(ret);
+
+        if (!controller) {
+                char *t;
+
+                /* If no controller is specified, we return the path *below* the controllers, without any
+                 * prefix. */
+
+                if (isempty(path) && isempty(suffix))
+                        return -EINVAL;
+
+                if (isempty(suffix))
+                        t = strdup(path);
+                else if (isempty(path))
+                        t = strdup(suffix);
+                else
+                        t = path_join(path, suffix);
+                if (!t)
+                        return -ENOMEM;
+
+                *ret = path_simplify(t);
+                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, ret);
+        else
+                r = join_path_legacy(controller, path, suffix, ret);
+        if (r < 0)
+                return r;
+
+        path_simplify(*ret);
+        return 0;
+}
+
+static int controller_is_v1_accessible(const char *root, const char *controller) {
+        const char *cpath, *dn;
+
+        assert(controller);
+
+        dn = controller_to_dirname(controller);
+
+        /* If root if specified, we check that:
+         * - possible subcgroup is created at root,
+         * - we can modify the hierarchy. */
+
+        cpath = strjoina("/sys/fs/cgroup/", dn, root, root ? "/cgroup.procs" : NULL);
+        return laccess(cpath, root ? W_OK : F_OK);
+}
+
+int cg_get_path_and_check(const char *controller, const char *path, const char *suffix, char **fs) {
+        int r;
+
+        assert(controller);
+        assert(fs);
+
+        if (!cg_controller_is_valid(controller))
+                return -EINVAL;
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                /* In the unified hierarchy all controllers are considered accessible,
+                 * except for the named hierarchies */
+                if (startswith(controller, "name="))
+                        return -EOPNOTSUPP;
+        } else {
+                /* Check if the specified controller is actually accessible */
+                r = controller_is_v1_accessible(NULL, controller);
+                if (r < 0)
+                        return r;
+        }
+
+        return cg_get_path(controller, path, suffix, fs);
+}
+
+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;
+
+        return RET_NERRNO(setxattr(fs, name, value, size, flags));
+}
+
+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_get_xattr_malloc(const char *controller, const char *path, const char *name, char **ret) {
+        _cleanup_free_ char *fs = NULL;
+        int r;
+
+        assert(path);
+        assert(name);
+
+        r = cg_get_path(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        r = lgetxattr_malloc(fs, name, ret);
+        if (r < 0)
+                return r;
+
+        return r;
+}
+
+int cg_get_xattr_bool(const char *controller, const char *path, const char *name) {
+        _cleanup_free_ char *val = NULL;
+        int r;
+
+        assert(path);
+        assert(name);
+
+        r = cg_get_xattr_malloc(controller, path, name, &val);
+        if (r < 0)
+                return r;
+
+        return parse_boolean(val);
+}
+
+int cg_remove_xattr(const char *controller, const char *path, const char *name) {
+        _cleanup_free_ char *fs = NULL;
+        int r;
+
+        assert(path);
+        assert(name);
+
+        r = cg_get_path(controller, path, NULL, &fs);
+        if (r < 0)
+                return r;
+
+        return RET_NERRNO(removexattr(fs, name));
+}
+
+int cg_pid_get_path(const char *controller, pid_t pid, char **ret_path) {
+        _cleanup_fclose_ FILE *f = NULL;
+        const char *fs, *controller_str = NULL;  /* avoid false maybe-uninitialized warning */
+        int unified, r;
+
+        assert(pid >= 0);
+        assert(ret_path);
+
+        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;
+        }
+
+        fs = procfs_file_alloca(pid, "cgroup");
+        r = fopen_unlocked(fs, "re", &f);
+        if (r == -ENOENT)
+                return -ESRCH;
+        if (r < 0)
+                return r;
+
+        for (;;) {
+                _cleanup_free_ char *line = NULL;
+                char *e;
+
+                r = read_line(f, LONG_LINE_MAX, &line);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENODATA;
+
+                if (unified) {
+                        e = startswith(line, "0:");
+                        if (!e)
+                                continue;
+
+                        e = strchr(e, ':');
+                        if (!e)
+                                continue;
+                } else {
+                        char *l;
+
+                        l = strchr(line, ':');
+                        if (!l)
+                                continue;
+
+                        l++;
+                        e = strchr(l, ':');
+                        if (!e)
+                                continue;
+                        *e = 0;
+
+                        assert(controller_str);
+                        r = string_contains_word(l, ",", controller_str);
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                continue;
+                }
+
+                char *path = strdup(e + 1);
+                if (!path)
+                        return -ENOMEM;
+
+                /* Truncate suffix indicating the process is a zombie */
+                e = endswith(path, " (deleted)");
+                if (e)
+                        *e = 0;
+
+                *ret_path = path;
+                return 0;
+        }
+}
+
+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 = path_join(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 **ret_controller, char **ret_path) {
+        _cleanup_free_ char *controller = NULL, *path = NULL;
+
+        assert(spec);
+
+        if (*spec == '/') {
+                if (!path_is_normalized(spec))
+                        return -EINVAL;
+
+                if (ret_path) {
+                        path = strdup(spec);
+                        if (!path)
+                                return -ENOMEM;
+
+                        path_simplify(path);
+                }
+
+        } else {
+                const char *e;
+
+                e = strchr(spec, ':');
+                if (e) {
+                        controller = strndup(spec, e-spec);
+                        if (!controller)
+                                return -ENOMEM;
+                        if (!cg_controller_is_valid(controller))
+                                return -EINVAL;
+
+                        if (!isempty(e + 1)) {
+                                path = strdup(e+1);
+                                if (!path)
+                                        return -ENOMEM;
+
+                                if (!path_is_normalized(path) ||
+                                    !path_is_absolute(path))
+                                        return -EINVAL;
+
+                                path_simplify(path);
+                        }
+
+                } else {
+                        if (!cg_controller_is_valid(spec))
+                                return -EINVAL;
+
+                        if (ret_controller) {
+                                controller = strdup(spec);
+                                if (!controller)
+                                        return -ENOMEM;
+                        }
+                }
+        }
+
+        if (ret_controller)
+                *ret_controller = TAKE_PTR(controller);
+        if (ret_path)
+                *ret_path = TAKE_PTR(path);
+        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);
+                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_safe(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) {
+        _cleanup_free_ char *unit = NULL;
+        const char *e;
+        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"))
+                return -ENXIO;
+
+        *ret = TAKE_PTR(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 NULL;
+
+                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. */
+        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_cgroupid(const char *path, uint64_t *ret) {
+        cg_file_handle fh = CG_FILE_HANDLE_INIT;
+        int mnt_id = -1;
+
+        assert(path);
+        assert(ret);
+
+        /* This is cgroupfs so we know the size of the handle, thus no need to loop around like
+         * name_to_handle_at_loop() does in mountpoint-util.c */
+        if (name_to_handle_at(AT_FDCWD, path, &fh.file_handle, &mnt_id, 0) < 0)
+                return -errno;
+
+        *ret = CG_FILE_HANDLE_CGROUPID(fh);
+        return 0;
+}
+
+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 strjoin("_", 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 > NAME_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 uninitialized:
+                 * 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, "/"))
+                        return -ENOMEM;
+
+                dash = strchr(dash+1, '-');
+        }
+
+        e = cg_escape(unit);
+        if (!e)
+                return -ENOMEM;
+
+        if (!strextend(&s, e))
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(s);
+
+        return 0;
+}
+
+int cg_is_threaded(const char *controller, const char *path) {
+        _cleanup_free_ char *fs = NULL, *contents = NULL;
+        _cleanup_strv_free_ char **v = NULL;
+        int r;
+
+        r = cg_get_path(controller, path, "cgroup.type", &fs);
+        if (r < 0)
+                return r;
+
+        r = read_full_virtual_file(fs, &contents, NULL);
+        if (r == -ENOENT)
+                return false; /* Assume no. */
+        if (r < 0)
+                return r;
+
+        v = strv_split(contents, NULL);
+        if (!v)
+                return -ENOMEM;
+
+        /* If the cgroup is in the threaded mode, it contains "threaded".
+         * If one of the parents or siblings is in the threaded mode, it may contain "invalid". */
+        return strv_contains(v, "threaded") || strv_contains(v, "invalid");
+}
+
+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_attribute_as_uint64(const char *controller, const char *path, const char *attribute, uint64_t *ret) {
+        _cleanup_free_ char *value = NULL;
+        uint64_t v;
+        int r;
+
+        assert(ret);
+
+        r = cg_get_attribute(controller, path, attribute, &value);
+        if (r == -ENOENT)
+                return -ENODATA;
+        if (r < 0)
+                return r;
+
+        if (streq(value, "max")) {
+                *ret = CGROUP_LIMIT_MAX;
+                return 0;
+        }
+
+        r = safe_atou64(value, &v);
+        if (r < 0)
+                return r;
+
+        *ret = v;
+        return 0;
+}
+
+int cg_get_attribute_as_bool(const char *controller, const char *path, const char *attribute, bool *ret) {
+        _cleanup_free_ char *value = NULL;
+        int r;
+
+        assert(ret);
+
+        r = cg_get_attribute(controller, path, attribute, &value);
+        if (r == -ENOENT)
+                return -ENODATA;
+        if (r < 0)
+                return r;
+
+        r = parse_boolean(value);
+        if (r < 0)
+                return r;
+
+        *ret = r;
+        return 0;
+}
+
+int cg_get_owner(const char *controller, const char *path, uid_t *ret_uid) {
+        _cleanup_free_ char *f = NULL;
+        struct stat stats;
+        int r;
+
+        assert(ret_uid);
+
+        r = cg_get_path(controller, path, NULL, &f);
+        if (r < 0)
+                return r;
+
+        r = stat(f, &stats);
+        if (r < 0)
+                return -errno;
+
+        *ret_uid = stats.st_uid;
+        return 0;
+}
+
+int cg_get_keyed_attribute_full(
+                const char *controller,
+                const char *path,
+                const char *attribute,
+                char **keys,
+                char **ret_values,
+                CGroupKeyMode mode) {
+
+        _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. If mode
+         * is set to GG_KEY_MODE_GRACEFUL we ignore missing keys and return those that were parsed successfully. */
+
+        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);
+        }
+
+        if (mode & CG_KEY_MODE_GRACEFUL)
+                goto done;
+
+        r = -ENXIO;
+
+fail:
+        for (i = 0; i < n; i++)
+                free(v[i]);
+
+        return r;
+
+done:
+        memcpy(ret_values, v, sizeof(char*) * n);
+        if (mode & CG_KEY_MODE_GRACEFUL)
+                return n_done;
+
+        return 0;
+}
+
+int cg_mask_to_string(CGroupMask mask, char **ret) {
+        _cleanup_free_ char *s = NULL;
+        bool space = false;
+        CGroupController c;
+        size_t n = 0;
+
+        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, 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_subtree(const char *root, 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 *controllers = NULL, *path = NULL;
+
+                /* In the unified hierarchy we can read the supported and accessible controllers from
+                 * the top-level cgroup attribute */
+
+                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;
+
+                /* Mask controllers that are not supported in unified hierarchy. */
+                mask &= CGROUP_MASK_V2;
+
+        } else {
+                CGroupController c;
+
+                /* In the legacy hierarchy, we check which hierarchies are accessible. */
+
+                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_v1_accessible(root, n) >= 0)
+                                mask |= bit;
+                }
+        }
+
+        *ret = mask;
+        return 0;
+}
+
+int cg_mask_supported(CGroupMask *ret) {
+        _cleanup_free_ char *root = NULL;
+        int r;
+
+        r = cg_get_root_path(&root);
+        if (r < 0)
+                return r;
+
+        return cg_mask_supported_subtree(root, ret);
+}
+
+int cg_kernel_controllers(Set **ret) {
+        _cleanup_set_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. */
+
+        r = fopen_unlocked("/proc/cgroups", "re", &f);
+        if (r == -ENOENT) {
+                *ret = NULL;
+                return 0;
+        }
+        if (r < 0)
+                return r;
+
+        /* Ignore the header line */
+        (void) read_line(f, SIZE_MAX, NULL);
+
+        for (;;) {
+                _cleanup_free_ char *controller = NULL;
+                int enabled = 0;
+
+                errno = 0;
+                if (fscanf(f, "%ms %*i %*i %i", &controller, &enabled) != 2) {
+
+                        if (feof(f))
+                                break;
+
+                        if (ferror(f))
+                                return errno_or_else(EIO);
+
+                        return -EBADMSG;
+                }
+
+                if (!enabled)
+                        continue;
+
+                if (!cg_controller_is_valid(controller))
+                        return -EBADMSG;
+
+                r = set_ensure_consume(&controllers, &string_hash_ops_free, TAKE_PTR(controller));
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(controllers);
+
+        return 0;
+}
+
+/* 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 mounts 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;
+
+int cg_unified_cached(bool flush) {
+        static thread_local CGroupUnified unified_cache = CGROUP_UNIFIED_UNKNOWN;
+
+        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 (flush)
+                unified_cache = CGROUP_UNIFIED_UNKNOWN;
+        else if (unified_cache >= CGROUP_UNIFIED_NONE)
+                return unified_cache;
+
+        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) {
+                                if (errno == ENOENT) {
+                                        /* Some other software may have set up /sys/fs/cgroup in a configuration we do not recognize. */
+                                        log_debug_errno(errno, "Unsupported cgroupsv1 setup detected: name=systemd hierarchy not found.");
+                                        return -ENOMEDIUM;
+                                }
+                                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 if (F_TYPE_EQUAL(fs.f_type, SYSFS_MAGIC)) {
+                return log_debug_errno(SYNTHETIC_ERRNO(ENOMEDIUM),
+                                       "No filesystem is currently mounted on /sys/fs/cgroup.");
+        } else
+                return log_debug_errno(SYNTHETIC_ERRNO(ENOMEDIUM),
+                                       "Unknown filesystem type %llx mounted on /sys/fs/cgroup.",
+                                       (unsigned long long)fs.f_type);
+
+        return unified_cache;
+}
+
+int cg_unified_controller(const char *controller) {
+        int r;
+
+        r = cg_unified_cached(false);
+        if (r < 0)
+                return r;
+
+        if (r == CGROUP_UNIFIED_NONE)
+                return false;
+
+        if (r >= CGROUP_UNIFIED_ALL)
+                return true;
+
+        return streq_ptr(controller, SYSTEMD_CGROUP_CONTROLLER);
+}
+
+int cg_all_unified(void) {
+        int r;
+
+        r = cg_unified_cached(false);
+        if (r < 0)
+                return r;
+
+        return r >= CGROUP_UNIFIED_ALL;
+}
+
+int cg_hybrid_unified(void) {
+        int r;
+
+        r = cg_unified_cached(false);
+        if (r < 0)
+                return r;
+
+        return r == CGROUP_UNIFIED_SYSTEMD && !unified_systemd_v232;
+}
+
+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);
+
+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 *const cgroup_controller_table[_CGROUP_CONTROLLER_MAX] = {
+        [CGROUP_CONTROLLER_CPU] = "cpu",
+        [CGROUP_CONTROLLER_CPUACCT] = "cpuacct",
+        [CGROUP_CONTROLLER_CPUSET] = "cpuset",
+        [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",
+        [CGROUP_CONTROLLER_BPF_FOREIGN] = "bpf-foreign",
+        [CGROUP_CONTROLLER_BPF_SOCKET_BIND] = "bpf-socket-bind",
+        [CGROUP_CONTROLLER_BPF_RESTRICT_NETWORK_INTERFACES] = "bpf-restrict-network-interfaces",
+};
+
+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 (strverscmp_improved(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;
+}
+
+static const char* const managed_oom_mode_table[_MANAGED_OOM_MODE_MAX] = {
+        [MANAGED_OOM_AUTO] = "auto",
+        [MANAGED_OOM_KILL] = "kill",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(managed_oom_mode, ManagedOOMMode);
+
+static const char* const managed_oom_preference_table[_MANAGED_OOM_PREFERENCE_MAX] = {
+        [MANAGED_OOM_PREFERENCE_NONE] = "none",
+        [MANAGED_OOM_PREFERENCE_AVOID] = "avoid",
+        [MANAGED_OOM_PREFERENCE_OMIT] = "omit",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(managed_oom_preference, ManagedOOMPreference);