13380515387

Committed 17 Feb 2025 09:20PM UTC coverage: 71.822% (+0.1%) from 71.714%

Build # 13380515387

Build Type

push

github

Committed by

DaanDeMeyer

Commit Message

ukify: print all remaining log-like output to stderr

We want to be able to capture stdout for json and such, so convert
all remaining logging to stderr.

Coverage Stats

293883 of 409184 relevant lines covered (71.82%)

716959.33 hits per line

Source File
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79.57

/src/basic/cgroup-util.c

/* 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 "constants.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_fs.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"

int cg_path_open(const char *controller, const char *path) {
        _cleanup_free_ char *fs = NULL;
        int r;

        r = cg_get_path(controller, path, /* item=*/ NULL, &fs);
        if (r < 0)
                return r;

        return RET_NERRNO(open(fs, O_DIRECTORY|O_CLOEXEC));
}

int cg_cgroupid_open(int cgroupfs_fd, uint64_t id) {
        _cleanup_close_ int fsfd = -EBADF;

        if (cgroupfs_fd < 0) {
                fsfd = open("/sys/fs/cgroup", O_CLOEXEC|O_DIRECTORY);
                if (fsfd < 0)
                        return -errno;

                cgroupfs_fd = fsfd;
        }

        cg_file_handle fh = CG_FILE_HANDLE_INIT;
        CG_FILE_HANDLE_CGROUPID(fh) = id;

        return RET_NERRNO(open_by_handle_at(cgroupfs_fd, &fh.file_handle, O_DIRECTORY|O_CLOEXEC));
}

int cg_path_from_cgroupid(int cgroupfs_fd, uint64_t id, char **ret) {
        _cleanup_close_ int cgfd = -EBADF;
        int r;

        cgfd = cg_cgroupid_open(cgroupfs_fd, id);
        if (cgfd < 0)
                return cgfd;

        _cleanup_free_ char *path = NULL;
        r = fd_get_path(cgfd, &path);
        if (r < 0)
                return r;

        if (!path_startswith(path, "/sys/fs/cgroup/"))
                return -EXDEV; /* recognizable error */

        if (ret)
                *ret = TAKE_PTR(path);
        return 0;
}

int cg_get_cgroupid_at(int dfd, const char *path, uint64_t *ret) {
        cg_file_handle fh = CG_FILE_HANDLE_INIT;
        int mnt_id;

        assert(dfd >= 0 || (dfd == AT_FDCWD && path_is_absolute(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(dfd, strempty(path), &fh.file_handle, &mnt_id, isempty(path) ? AT_EMPTY_PATH : 0) < 0) {
                assert(errno != EOVERFLOW);
                return -errno;
        }

        *ret = CG_FILE_HANDLE_CGROUPID(fh);
        return 0;
}

static int cg_enumerate_items(const char *controller, const char *path, FILE **ret, const char *item) {
        _cleanup_free_ char *fs = NULL;
        FILE *f;
        int r;

        assert(ret);

        r = cg_get_path(controller, path, item, &fs);
        if (r < 0)
                return r;

        f = fopen(fs, "re");
        if (!f)
                return -errno;

        *ret = f;
        return 0;
}

int cg_enumerate_processes(const char *controller, const char *path, FILE **ret) {
        return cg_enumerate_items(controller, path, ret, "cgroup.procs");
}

int cg_read_pid(FILE *f, pid_t *ret, CGroupFlags flags) {
        unsigned long ul;

        /* Note that the cgroup.procs might contain duplicates! See cgroups.txt for details. */

        assert(f);
        assert(ret);

        for (;;) {
                errno = 0;
                if (fscanf(f, "%lu", &ul) != 1) {

                        if (feof(f)) {
                                *ret = 0;
                                return 0;
                        }

                        return errno_or_else(EIO);
                }

                if (ul > PID_T_MAX)
                        return -EIO;

                /* In some circumstances (e.g. WSL), cgroups might contain unmappable PIDs from other
                 * contexts. These show up as zeros, and depending on the caller, can either be plain
                 * skipped over, or returned as-is. */
                if (ul == 0 && !FLAGS_SET(flags, CGROUP_DONT_SKIP_UNMAPPED))
                        continue;

                *ret = (pid_t) ul;
                return 1;
        }
}

int cg_read_pidref(FILE *f, PidRef *ret, CGroupFlags flags) {
        int r;

        assert(f);
        assert(ret);

        for (;;) {
                pid_t pid;

                r = cg_read_pid(f, &pid, flags);
                if (r < 0)
                        return log_debug_errno(r, "Failed to read pid from cgroup item: %m");
                if (r == 0) {
                        *ret = PIDREF_NULL;
                        return 0;
                }

                if (pid == 0)
                        return -EREMOTE;

                if (FLAGS_SET(flags, CGROUP_NO_PIDFD)) {
                        *ret = PIDREF_MAKE_FROM_PID(pid);
                        return 1;
                }

                r = pidref_set_pid(ret, pid);
                if (r >= 0)
                        return 1;
                if (r != -ESRCH)
                        return r;

                /* ESRCH → gone by now? just skip over it, read the next */
        }
}

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;
                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;

                return strdup_to(ret, q);
        }
}

bool cg_ns_supported(void) {
        static thread_local int supported = -1;

        if (supported >= 0)
                return supported;

        if (access("/proc/self/ns/cgroup", F_OK) >= 0)
                return (supported = true);
        if (errno != ENOENT)
                log_debug_errno(errno, "Failed to check whether /proc/self/ns/cgroup is available, assuming not: %m");
        return (supported = false);
}

bool cg_freezer_supported(void) {
        static thread_local int supported = -1;

        if (supported >= 0)
                return supported;

        if (cg_all_unified() <= 0)
                return (supported = false);

        if (access("/sys/fs/cgroup/init.scope/cgroup.freeze", F_OK) >= 0)
                return (supported = true);
        if (errno != ENOENT)
                log_debug_errno(errno, "Failed to check whether cgroup freezer is available, assuming not: %m");
        return (supported = false);
}

bool cg_kill_supported(void) {
        static thread_local int supported = -1;

        if (supported >= 0)
                return supported;

        if (cg_all_unified() <= 0)
                return (supported = false);

        if (access("/sys/fs/cgroup/init.scope/cgroup.kill", F_OK) >= 0)
                return (supported = true);
        if (errno != ENOENT)
                log_debug_errno(errno, "Failed to check whether cgroup.kill is available, assuming not: %m");
        return (supported = false);
}

int cg_enumerate_subgroups(const char *controller, const char *path, DIR **ret) {
        _cleanup_free_ char *fs = NULL;
        DIR *d;
        int r;

        assert(ret);

        /* This is not recursive! */

        r = cg_get_path(controller, path, NULL, &fs);
        if (r < 0)
                return r;

        d = opendir(fs);
        if (!d)
                return -errno;

        *ret = d;
        return 0;
}

int cg_read_subgroup(DIR *d, char **ret) {
        assert(d);
        assert(ret);

        FOREACH_DIRENT_ALL(de, d, return -errno) {
                if (de->d_type != DT_DIR)
                        continue;

                if (dot_or_dot_dot(de->d_name))
                        continue;

                return strdup_to_full(ret, de->d_name);
        }

        *ret = NULL;
        return 0;
}

static int cg_kill_items(
                const char *path,
                const char *item,
                int sig,
                CGroupFlags flags,
                Set *s,
                cg_kill_log_func_t log_kill,
                void *userdata) {

        _cleanup_set_free_ Set *allocated_set = NULL;
        int r, ret = 0;

        assert(path);
        assert(item);
        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.
         *
         * When sending SIGKILL, prefer cg_kill_kernel_sigkill(), which is fully atomic. */

        if (!s) {
                s = allocated_set = set_new(NULL);
                if (!s)
                        return -ENOMEM;
        }

        bool done;
        do {
                _cleanup_fclose_ FILE *f = NULL;
                int ret_log_kill;

                done = true;

                r = cg_enumerate_items(SYSTEMD_CGROUP_CONTROLLER, path, &f, item);
                if (r == -ENOENT)
                        break;
                if (r < 0)
                        return RET_GATHER(ret, log_debug_errno(r, "Failed to enumerate cgroup items: %m"));

                for (;;) {
                        _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;

                        r = cg_read_pidref(f, &pidref, flags);
                        if (r < 0)
                                return RET_GATHER(ret, log_debug_errno(r, "Failed to read pidref from cgroup '%s': %m", path));
                        if (r == 0)
                                break;

                        if ((flags & CGROUP_IGNORE_SELF) && pidref_is_self(&pidref))
                                continue;

                        if (set_contains(s, PID_TO_PTR(pidref.pid)))
                                continue;

                        /* Ignore kernel threads to mimic the behavior of cgroup.kill. */
                        if (pidref_is_kernel_thread(&pidref) > 0) {
                                log_debug("Ignoring kernel thread with pid " PID_FMT " in cgroup '%s'", pidref.pid, path);
                                continue;
                        }

                        if (log_kill)
                                ret_log_kill = log_kill(&pidref, sig, userdata);

                        /* If we haven't killed this process yet, kill it */
                        r = pidref_kill(&pidref, sig);
                        if (r < 0 && r != -ESRCH)
                                RET_GATHER(ret, log_debug_errno(r, "Failed to kill process with pid " PID_FMT " from cgroup '%s': %m", pidref.pid, path));
                        if (r >= 0) {
                                if (flags & CGROUP_SIGCONT)
                                        (void) pidref_kill(&pidref, SIGCONT);

                                if (ret == 0) {
                                        if (log_kill)
                                                ret = ret_log_kill;
                                        else
                                                ret = 1;
                                }
                        }

                        done = false;

                        r = set_put(s, PID_TO_PTR(pidref.pid));
                        if (r < 0)
                                return RET_GATHER(ret, r);
                }

                /* 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 *path,
                int sig,
                CGroupFlags flags,
                Set *s,
                cg_kill_log_func_t log_kill,
                void *userdata) {

        int r, ret;

        assert(path);

        ret = cg_kill_items(path, "cgroup.procs", sig, flags, s, log_kill, userdata);
        if (ret < 0)
                return log_debug_errno(ret, "Failed to kill processes in cgroup '%s' item cgroup.procs: %m", path);
        if (sig != SIGKILL)
                return ret;

        /* 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(SYSTEMD_CGROUP_CONTROLLER);
        if (r < 0)
                return r;
        if (r == 0)
                return ret;

        /* Opening pidfds for non thread group leaders only works from 6.9 onwards with PIDFD_THREAD. On
         * older kernels or without PIDFD_THREAD pidfd_open() fails with EINVAL. Since we might read non
         * thread group leader IDs from cgroup.threads, we set CGROUP_NO_PIDFD to avoid trying open pidfd's
         * for them and instead use the regular pid. */
        r = cg_kill_items(path, "cgroup.threads", sig, flags|CGROUP_NO_PIDFD, s, log_kill, userdata);
        if (r < 0)
                return log_debug_errno(r, "Failed to kill processes in cgroup '%s' item cgroup.threads: %m", path);

        return r > 0 || ret > 0;
}

int cg_kill_recursive(
                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;

        assert(path);
        assert(sig >= 0);

        if (!s) {
                s = allocated_set = set_new(NULL);
                if (!s)
                        return -ENOMEM;
        }

        ret = cg_kill(path, sig, flags, s, log_kill, userdata);

        r = cg_enumerate_subgroups(SYSTEMD_CGROUP_CONTROLLER, path, &d);
        if (r < 0) {
                if (r != -ENOENT)
                        RET_GATHER(ret, log_debug_errno(r, "Failed to enumerate cgroup '%s' subgroups: %m", path));

                return ret;
        }

        for (;;) {
                _cleanup_free_ char *fn = NULL, *p = NULL;

                r = cg_read_subgroup(d, &fn);
                if (r < 0) {
                        RET_GATHER(ret, log_debug_errno(r, "Failed to read subgroup from cgroup '%s': %m", path));
                        break;
                }
                if (r == 0)
                        break;

                p = path_join(empty_to_root(path), fn);
                if (!p)
                        return -ENOMEM;

                r = cg_kill_recursive(p, sig, flags, s, log_kill, userdata);
                if (r < 0)
                        log_debug_errno(r, "Failed to recursively kill processes in cgroup '%s': %m", p);
                if (r != 0 && ret >= 0)
                        ret = r;
        }

        return ret;
}

int cg_kill_kernel_sigkill(const char *path) {
        _cleanup_free_ char *killfile = NULL;
        int r;

        /* 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(). */

        assert(path);

        if (!cg_kill_supported())
                return -EOPNOTSUPP;

        r = cg_get_path(SYSTEMD_CGROUP_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 log_debug_errno(r, "Failed to write to cgroup.kill for cgroup '%s': %m", path);

        return 0;
}

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 access_nofollow(cpath, root ? W_OK : F_OK);
}

int cg_get_path_and_check(const char *controller, const char *path, const char *suffix, char **ret) {
        int r;

        assert(controller);
        assert(ret);

        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, ret);
}

int cg_set_xattr(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(SYSTEMD_CGROUP_CONTROLLER, path, NULL, &fs);
        if (r < 0)
                return r;

        return RET_NERRNO(setxattr(fs, name, value, size, flags));
}

int cg_get_xattr(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(SYSTEMD_CGROUP_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 *path, const char *name, char **ret) {
        _cleanup_free_ char *fs = NULL;
        int r;

        assert(path);
        assert(name);

        r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, path, NULL, &fs);
        if (r < 0)
                return r;

        return lgetxattr_malloc(fs, name, ret);
}

int cg_get_xattr_bool(const char *path, const char *name) {
        _cleanup_free_ char *fs = NULL;
        int r;

        assert(path);
        assert(name);

        r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, path, NULL, &fs);
        if (r < 0)
                return r;

        return getxattr_at_bool(AT_FDCWD, fs, name, /* flags= */ 0);
}

int cg_remove_xattr(const char *path, const char *name) {
        _cleanup_free_ char *fs = NULL;
        int r;

        assert(path);
        assert(name);

        r = cg_get_path(SYSTEMD_CGROUP_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;
                }

                _cleanup_free_ char *path = strdup(e + 1);
                if (!path)
                        return -ENOMEM;

                /* Refuse cgroup paths from outside our cgroup namespace */
                if (startswith(path, "/../"))
                        return -EUNATCH;

                /* Truncate suffix indicating the process is a zombie */
                e = endswith(path, " (deleted)");
                if (e)
                        *e = 0;

                *ret_path = TAKE_PTR(path);
                return 0;
        }
}

int cg_pidref_get_path(const char *controller, const PidRef *pidref, char **ret_path) {
        _cleanup_free_ char *path = NULL;
        int r;

        assert(ret_path);

        if (!pidref_is_set(pidref))
                return -ESRCH;
        if (pidref_is_remote(pidref))
                return -EREMOTE;

        // XXX: Ideally we'd use pidfd_get_cgroupid() + cg_path_from_cgroupid() here, to extract this
        // bit of information from pidfd directly. However, the latter requires privilege and it's
        // not entirely clear how to handle cgroups from outer namespace.

        r = cg_pid_get_path(controller, pidref->pid, &path);
        if (r < 0)
                return r;

        /* Before we return the path, make sure the procfs entry for this pid still matches the pidref */
        r = pidref_verify(pidref);
        if (r < 0)
                return r;

        *ret_path = TAKE_PTR(path);
        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, CGROUP_DONT_SKIP_UNMAPPED);
        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;
        int r;

        assert(spec);

        if (*spec == '/') {
                if (!path_is_normalized(spec))
                        return -EINVAL;

                if (ret_path) {
                        r = path_simplify_alloc(spec, &path);
                        if (r < 0)
                                return r;
                }

        } 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 **ret) {
        _cleanup_free_ char *c = NULL, *p = NULL;
        int r;

        assert(path);
        assert(ret);

        /* First, check if it already is a filesystem path */
        if (path_startswith(path, "/sys/fs/cgroup"))
                return path_simplify_alloc(path, ret);

        /* 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, ret);
}

int cg_get_root_path(char **ret_path) {
        char *p, *e;
        int r;

        assert(ret_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;

        *ret_path = p;
        return 0;
}

int cg_shift_path(const char *cgroup, const char *root, const char **ret_shifted) {
        _cleanup_free_ char *rt = NULL;
        char *p;
        int r;

        assert(cgroup);
        assert(ret_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)
                *ret_shifted = p - 1;
        else
                *ret_shifted = cgroup;

        return 0;
}

int cg_pid_get_path_shifted(pid_t pid, const char *root, char **ret_cgroup) {
        _cleanup_free_ char *raw = NULL;
        const char *c;
        int r;

        assert(pid >= 0);
        assert(ret_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) {
                *ret_cgroup = TAKE_PTR(raw);
                return 0;
        }

        return strdup_to(ret_cgroup, c);
}

int cg_path_decode_unit(const char *cgroup, char **ret_unit) {
        assert(cgroup);
        assert(ret_unit);

        size_t n = strcspn(cgroup, "/");
        if (n < 3)
                return -ENXIO;

        char *c = strndupa_safe(cgroup, n);
        c = cg_unescape(c);

        if (!unit_name_is_valid(c, UNIT_NAME_PLAIN|UNIT_NAME_INSTANCE))
                return -ENXIO;

        return strdup_to(ret_unit, c);
}

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_path_get_unit_path(const char *path, char **ret) {
        _cleanup_free_ char *path_copy = NULL;
        char *unit_name;

        assert(path);
        assert(ret);

        path_copy = strdup(path);
        if (!path_copy)
                return -ENOMEM;

        unit_name = (char *)skip_slices(path_copy);
        unit_name[strcspn(unit_name, "/")] = 0;

        if (!unit_name_is_valid(cg_unescape(unit_name), UNIT_NAME_PLAIN|UNIT_NAME_INSTANCE))
                return -ENXIO;

        *ret = TAKE_PTR(path_copy);

        return 0;
}

int cg_pid_get_unit(pid_t pid, char **ret_unit) {
        _cleanup_free_ char *cgroup = NULL;
        int r;

        assert(ret_unit);

        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
        if (r < 0)
                return r;

        return cg_path_get_unit(cgroup, ret_unit);
}

int cg_pidref_get_unit(const PidRef *pidref, char **ret) {
        _cleanup_free_ char *unit = NULL;
        int r;

        assert(ret);

        if (!pidref_is_set(pidref))
                return -ESRCH;
        if (pidref_is_remote(pidref))
                return -EREMOTE;

        r = cg_pid_get_unit(pidref->pid, &unit);
        if (r < 0)
                return r;

        r = pidref_verify(pidref);
        if (r < 0)
                return r;

        *ret = TAKE_PTR(unit);
        return 0;
}

/**
 * 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 **ret_unit) {
        _cleanup_free_ char *cgroup = NULL;
        int r;

        assert(ret_unit);

        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
        if (r < 0)
                return r;

        return cg_path_get_user_unit(cgroup, ret_unit);
}

int cg_path_get_machine_name(const char *path, char **ret_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, ret_machine);
}

int cg_pid_get_machine_name(pid_t pid, char **ret_machine) {
        _cleanup_free_ char *cgroup = NULL;
        int r;

        assert(ret_machine);

        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
        if (r < 0)
                return r;

        return cg_path_get_machine_name(cgroup, ret_machine);
}

int cg_path_get_session(const char *path, char **ret_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 (!ret_session)
                return 0;

        return strdup_to(ret_session, start);
}

int cg_pid_get_session(pid_t pid, char **ret_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, ret_session);
}

int cg_pidref_get_session(const PidRef *pidref, char **ret) {
        int r;

        if (!pidref_is_set(pidref))
                return -ESRCH;
        if (pidref_is_remote(pidref))
                return -EREMOTE;

        _cleanup_free_ char *session = NULL;
        r = cg_pid_get_session(pidref->pid, &session);
        if (r < 0)
                return r;

        r = pidref_verify(pidref);
        if (r < 0)
                return r;

        if (ret)
                *ret = TAKE_PTR(session);
        return 0;
}

int cg_path_get_owner_uid(const char *path, uid_t *ret_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, ret_uid) < 0)
                return -ENXIO;

        return 0;
}

int cg_pid_get_owner_uid(pid_t pid, uid_t *ret_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, ret_uid);
}

int cg_pidref_get_owner_uid(const PidRef *pidref, uid_t *ret) {
        int r;

        if (!pidref_is_set(pidref))
                return -ESRCH;
        if (pidref_is_remote(pidref))
                return -EREMOTE;

        uid_t uid;
        r = cg_pid_get_owner_uid(pidref->pid, &uid);
        if (r < 0)
                return r;

        r = pidref_verify(pidref);
        if (r < 0)
                return r;

        if (ret)
                *ret = uid;

        return 0;
}

int cg_path_get_slice(const char *p, char **ret_slice) {
        const char *e = NULL;

        assert(p);
        assert(ret_slice);

        /* Finds the right-most slice unit from the beginning, but stops before we come to
         * the first non-slice unit. */

        for (;;) {
                const char *s;
                int n;

                n = path_find_first_component(&p, /* accept_dot_dot = */ false, &s);
                if (n < 0)
                        return n;
                if (!valid_slice_name(s, n))
                        break;

                e = s;
        }

        if (e)
                return cg_path_decode_unit(e, ret_slice);

        return strdup_to(ret_slice, SPECIAL_ROOT_SLICE);
}

int cg_pid_get_slice(pid_t pid, char **ret_slice) {
        _cleanup_free_ char *cgroup = NULL;
        int r;

        assert(ret_slice);

        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
        if (r < 0)
                return r;

        return cg_path_get_slice(cgroup, ret_slice);
}

int cg_path_get_user_slice(const char *p, char **ret_slice) {
        const char *t;
        assert(p);
        assert(ret_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, ret_slice);
}

int cg_pid_get_user_slice(pid_t pid, char **ret_slice) {
        _cleanup_free_ char *cgroup = NULL;
        int r;

        assert(ret_slice);

        r = cg_pid_get_path_shifted(pid, NULL, &cgroup);
        if (r < 0)
                return r;

        return cg_path_get_user_slice(cgroup, ret_slice);
}

bool cg_needs_escape(const char *p) {

        /* Checks if the specified path is a valid cgroup name by our rules, or if it must be escaped. Note
         * that we consider escaped cgroup names invalid here, as they need to be escaped a second time if
         * they shall be used. Also note that various names cannot be made valid by escaping even if we
         * return true here (because too long, or contain the forbidden character "/"). */

        if (!filename_is_valid(p))
                return true;

        if (IN_SET(p[0], '_', '.'))
                return true;

        if (STR_IN_SET(p, "notify_on_release", "release_agent", "tasks"))
                return true;

        if (startswith(p, "cgroup."))
                return true;

        for (CGroupController c = 0; c < _CGROUP_CONTROLLER_MAX; c++) {
                const char *q;

                q = startswith(p, cgroup_controller_to_string(c));
                if (!q)
                        continue;

                if (q[0] == '.')
                        return true;
        }

        return false;
}

int cg_escape(const char *p, char **ret) {
        _cleanup_free_ char *n = NULL;

        /* 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 (cg_needs_escape(p)) {
                n = strjoin("_", p);
                if (!n)
                        return -ENOMEM;

                if (!filename_is_valid(n)) /* became invalid due to the prefixing? Or contained things like a slash that cannot be fixed by prefixing? */
                        return -EINVAL;
        } else {
                n = strdup(p);
                if (!n)
                        return -ENOMEM;
        }

        *ret = TAKE_PTR(n);
        return 0;
}

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))
                return strdup_to(ret, "");

        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;

                r = cg_escape(n, &escaped);
                if (r < 0)
                        return r;

                if (!strextend(&s, escaped, "/"))
                        return -ENOMEM;

                dash = strchr(dash+1, '-');
        }

        r = cg_escape(unit, &e);
        if (r < 0)
                return r;

        if (!strextend(&s, e))
                return -ENOMEM;

        *ret = TAKE_PTR(s);
        return 0;
}

int cg_is_threaded(const char *path) {
        _cleanup_free_ char *fs = NULL, *contents = NULL;
        _cleanup_strv_free_ char **v = NULL;
        int r;

        r = cg_get_path(SYSTEMD_CGROUP_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 *path, uid_t *ret_uid) {
        _cleanup_free_ char *f = NULL;
        struct stat stats;
        int r;

        assert(ret_uid);

        r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, path, NULL, &f);
        if (r < 0)
                return r;

        if (stat(f, &stats) < 0)
                return -errno;

        r = stat_verify_directory(&stats);
        if (r < 0)
                return r;

        *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:
        free_many_charp(v, n);
        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;

                if (fscanf(f, "%ms %*i %*i %i", &controller, &enabled) != 2) {

                        if (ferror(f))
                                return -errno;

                        if (feof(f))
                                break;

                        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;
}

int cg_is_delegated(const char *path) {
        int r;

        assert(path);

        r = cg_get_xattr_bool(path, "trusted.delegate");
        if (!ERRNO_IS_NEG_XATTR_ABSENT(r))
                return r;

        /* If the trusted xattr isn't set (preferred), then check the untrusted one. Under the assumption
         * that whoever is trusted enough to own the cgroup, is also trusted enough to decide if it is
         * delegated or not this should be safe. */
        r = cg_get_xattr_bool(path, "user.delegate");
        return ERRNO_IS_NEG_XATTR_ABSENT(r) ? false : r;
}

int cg_is_delegated_fd(int fd) {
        int r;

        assert(fd >= 0);

        r = getxattr_at_bool(fd, /* path= */ NULL, "trusted.delegate", /* flags= */ 0);
        if (!ERRNO_IS_NEG_XATTR_ABSENT(r))
                return r;

        r = getxattr_at_bool(fd, /* path= */ NULL, "user.delegate", /* flags= */ 0);
        return ERRNO_IS_NEG_XATTR_ABSENT(r) ? false : r;
}

int cg_has_coredump_receive(const char *path) {
        int r;

        assert(path);

        r = cg_get_xattr_bool(path, "user.coredump_receive");
        if (ERRNO_IS_NEG_XATTR_ABSENT(r))
                return false;

        return r;
}

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);

systemd / systemd / 13380515387

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