From 48de958400d2acc96dc3268c287782b33d7ae883 Mon Sep 17 00:00:00 2001
From: Markus Boehme <markubo@amazon.com>
Date: Wed, 4 Jan 2023 15:33:10 +0000
Subject: [PATCH 9501/9501] cgroup-util: accept cgroup hierarchy base as option

On an ordinary system, the cgroup hierarchy is expected to be located at
`/sys/fs/cgroup`. Introduce the `--cgroup-base` option to `systemd` to
make it look for the cgroup hierarchy at another location.

The cgroup base may only be moved once and, preferably only during
initialization while parsing the command line arguments to avoid
confusion.

Signed-off-by: Markus Boehme <markubo@amazon.com>
---
 src/core/main.c          | 14 +++++++++++++-
 src/shared/cgroup-util.c | 26 ++++++++++++++++++++++++++
 src/shared/cgroup-util.h |  2 ++
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/src/core/main.c b/src/core/main.c
index 2d70ed0..ce0314a 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -79,6 +79,8 @@
 #include "kmod-setup.h"
 #include "emergency-action.h"
 
+#include "cgroup-util.h"
+
 static enum {
         ACTION_RUN,
         ACTION_HELP,
@@ -680,7 +682,8 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_DESERIALIZE,
                 ARG_SWITCHED_ROOT,
                 ARG_DEFAULT_STD_OUTPUT,
-                ARG_DEFAULT_STD_ERROR
+                ARG_DEFAULT_STD_ERROR,
+                ARG_CGROUP_BASE,
         };
 
         static const struct option options[] = {
@@ -704,6 +707,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "switched-root",            no_argument,       NULL, ARG_SWITCHED_ROOT            },
                 { "default-standard-output",  required_argument, NULL, ARG_DEFAULT_STD_OUTPUT,      },
                 { "default-standard-error",   required_argument, NULL, ARG_DEFAULT_STD_ERROR,       },
+                { "cgroup-base",              required_argument, NULL, ARG_CGROUP_BASE,             },
                 {}
         };
 
@@ -880,6 +884,14 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_switched_root = true;
                         break;
 
+                case ARG_CGROUP_BASE:
+                        r = cg_set_hierarchy_base(optarg);
+                        if (r < 0) {
+                                log_error_errno(r, "Failed to use cgroup hierarchy base to %s: %m", optarg);
+                                return r;
+                        }
+                        break;
+
                 case 'h':
                         arg_action = ACTION_HELP;
                         if (arg_no_pager < 0)
diff --git a/src/shared/cgroup-util.c b/src/shared/cgroup-util.c
index b055dd8..e9f8d24 100644
--- a/src/shared/cgroup-util.c
+++ b/src/shared/cgroup-util.c
@@ -40,6 +40,7 @@
 #include "fileio.h"
 #include "special.h"
 #include "mkdir.h"
+#include "refcnt.h"
 
 static char *cg_hierarchy_base = "/sys/fs/cgroup";
 
@@ -1839,3 +1840,28 @@ int cg_blkio_weight_parse(const char *s, uint64_t *ret) {
         *ret = u;
         return 0;
 }
+
+int cg_set_hierarchy_base(const char *path) {
+        static RefCount base_set = REFCNT_INIT;
+        char *b;
+        int r;
+
+        assert(path);
+
+        r = is_dir(path, true);
+        if (r <= 0)
+                return r ? r : -ENOTDIR;
+
+        b = strdup(path);
+        if (!b)
+                return -ENOMEM;
+
+        if (REFCNT_INC(base_set) > 2) {
+                free(b);
+                return -EINVAL;
+        }
+
+        cg_hierarchy_base = b;
+
+        return 0;
+}
diff --git a/src/shared/cgroup-util.h b/src/shared/cgroup-util.h
index b6f28c5..07e6d7e 100644
--- a/src/shared/cgroup-util.h
+++ b/src/shared/cgroup-util.h
@@ -163,3 +163,5 @@ int cg_kernel_controllers(Set *controllers);
 
 int cg_cpu_shares_parse(const char *s, uint64_t *ret);
 int cg_blkio_weight_parse(const char *s, uint64_t *ret);
+
+int cg_set_hierarchy_base(const char *path);
-- 
2.36.1