cgroup: add support for unified cgroup v2

src/libcrun/cgroup.c

@@ -226,7 +226,7 @@ write_controller_file (const char *path, int controllers_to_enable, libcrun_erro
           libcrun_error_t tmp_err = NULL;
           int exists;
 
-          exists = crun_path_exists (subtree_control, err);
+          exists = crun_path_exists (subtree_control, &tmp_err);
           if (UNLIKELY (exists < 0))
             {
               crun_error_release (&tmp_err);
@@ -2752,9 +2752,85 @@ update_cgroup_v1_resources (runtime_spec_schema_config_linux_resources *resource
         return ret;
     }
 
+  if (resources->unified && resources->unified->len > 0)
+        return crun_make_error (err, 0, "invalid configuration: cannot use unified on cgroup v1");
+
+  return 0;
+}
+
+static int
+write_unified_resources (int cgroup_dirfd, runtime_spec_schema_config_linux_resources *resources, libcrun_error_t *err)
+{
+  size_t i;
+  int ret;
+
+  for (i = 0; i < resources->unified->len; i++)
+    {
+      size_t len;
+
+      if (strchr (resources->unified->keys[i], '/'))
+        return crun_make_error (err, 0, "key `%s` must be a file name without any slash", resources->unified->keys[i]);
+
+      len = strlen (resources->unified->values[i]);
+      ret = write_file_at (cgroup_dirfd, resources->unified->keys[i], resources->unified->values[i], len, err);
+      if (UNLIKELY (ret < 0))
+        {
+          errno = crun_error_get_errno (err);
+
+          /* If the file is not found, try to give a more meaningful error message.  */
+          if (errno == ENOENT || errno == EPERM || errno == EACCES)
+            {
+              cleanup_free char *controllers = NULL;
+              libcrun_error_t tmp_err = NULL;
+              cleanup_free char *key = NULL;
+              char *saveptr = NULL;
+              bool found = false;
+              const char *token;
+              char *it;
+
+              /* Check if the specified controller is enabled.  */
+              key = xstrdup (resources->unified->keys[i]);
+
+              it = strchr (key, '.');
+              if (it == NULL)
+                {
+                  crun_error_release (err);
+                  return crun_make_error (err, 0, "the specified key has not the form CONTROLLER.VALUE `%s`", resources->unified->keys[i]);
+                }
+              *it = '\0';
+
+              /* cgroup. files are not part of a controller.  Return the original error.  */
+              if (strcmp (key, "cgroup") == 0)
+                return ret;
+
+              /* If the cgroup.controllers file cannot be read, return the original error.  */
+              if (read_all_file_at (cgroup_dirfd, "cgroup.controllers", &controllers, NULL, &tmp_err) < 0)
+                {
+                  crun_error_release (&tmp_err);
+                  return ret;
+                }
+              for (token = strtok_r (controllers, " \n", &saveptr); token; token = strtok_r (NULL, " \n", &saveptr))
+                {
+                  if (strcmp (token, key) == 0)
+                    {
+                      found = true;
+                      break;
+                    }
+                }
+              if (! found)
+                {
+                  crun_error_release (err);
+                  return crun_make_error (err, 0, "the requested controller `%s` is not available", key);
+                }
+            }
+          return ret;
+        }
+    }
+
   return 0;
 }
 
+
 static int
 update_cgroup_v2_resources (runtime_spec_schema_config_linux_resources *resources, char *path, libcrun_error_t *err)
 {
@@ -2828,6 +2904,14 @@ update_cgroup_v2_resources (runtime_spec_schema_config_linux_resources *resource
         return ret;
     }
 
+  /* Write unified resources if any.  They have higher precedence and override any previous setting.  */
+  if (resources->unified)
+    {
+      ret = write_unified_resources (cgroup_dirfd, resources, err);
+      if (UNLIKELY (ret < 0))
+        return ret;
+    }
+
   return 0;
 }
 

src/libcrun/utils.c

@@ -746,20 +746,28 @@ read_all_fd (int fd, const char *description, char **out, size_t *len, libcrun_e
 }
 
 int
-read_all_file (const char *path, char **out, size_t *len, libcrun_error_t *err)
+read_all_file_at (int dirfd, const char *path, char **out, size_t *len, libcrun_error_t *err)
 {
   cleanup_close int fd;
 
-  if (strcmp (path, "-") == 0)
-    path = "/dev/stdin";
-
-  fd = TEMP_FAILURE_RETRY (open (path, O_RDONLY));
+  fd = TEMP_FAILURE_RETRY (openat (dirfd, path, O_RDONLY));
   if (UNLIKELY (fd < 0))
     return crun_make_error (err, errno, "error opening file `%s`", path);
 
   return read_all_fd (fd, path, out, len, err);
 }
 
+int
+read_all_file (const char *path, char **out, size_t *len, libcrun_error_t *err)
+{
+  cleanup_close int fd = -1;
+
+  if (strcmp (path, "-") == 0)
+    path = "/dev/stdin";
+
+  return read_all_file_at (AT_FDCWD, path, out, len, err);
+}
+
 int
 open_unix_domain_client_socket (const char *path, int dgram, libcrun_error_t *err)
 {

src/libcrun/utils.h

@@ -183,6 +183,8 @@ int read_all_fd (int fd, const char *description, char **out, size_t *len, libcr
 
 int read_all_file (const char *path, char **out, size_t *len, libcrun_error_t *err);
 
+int read_all_file_at (int dirfd, const char *path, char **out, size_t *len, libcrun_error_t *err);
+
 int open_unix_domain_client_socket (const char *path, int dgram, libcrun_error_t *err);
 
 int open_unix_domain_socket (const char *path, int dgram, libcrun_error_t *err);

tests/init.c

@@ -136,7 +136,7 @@ int main (int argc, char **argv)
   if (strcmp (argv[1], "echo") == 0)
     {
       if (argc < 3)
-        error (EXIT_FAILURE, 0, "'cat' requires an argument");
+        error (EXIT_FAILURE, 0, "'echo' requires an argument");
       fputs (argv[2], stdout);
       exit (0);
     }

tests/test_resources.py

@@ -23,6 +23,10 @@
 import sys
 from tests_utils import *
 
+
+def is_cgroup_v2_unified():
+    return subprocess.check_output("stat -c%T -f /sys/fs/cgroup".split()).decode("utf-8").strip() == "cgroup2fs"
+
 def test_resources_pid_limit():
     if os.getuid() != 0:
         return 77
@@ -42,8 +46,88 @@ def test_resources_pid_limit():
         return -1
     return 0
 
+def test_resources_unified_invalid_controller():
+    if not is_cgroup_v2_unified() or os.geteuid() != 0:
+        return 77
+
+    conf = base_config()
+    add_all_namespaces(conf, cgroupns=True)
+    conf['process']['args'] = ['/init', 'pause']
+
+    conf['linux']['resources'] = {}
+    conf['linux']['resources']['unified'] = {
+            "foo.bar": "doesntmatter"
+    }
+    cid = None
+    try:
+        out, cid = run_and_get_output(conf, command='run', detach=True)
+        # must raise an exception, fail if it doesn't.
+        return -1
+    except Exception as e:
+        if 'the requested controller `foo` is not available' in e.stdout.decode("utf-8").strip():
+            return 0
+        return -1
+    finally:
+        if cid is not None:
+            run_crun_command(["delete", "-f", cid])
+    return 0
+
+def test_resources_unified_invalid_key():
+    if not is_cgroup_v2_unified() or os.geteuid() != 0:
+        return 77
+
+    conf = base_config()
+    add_all_namespaces(conf, cgroupns=True)
+    conf['process']['args'] = ['/init', 'pause']
+
+    conf['linux']['resources'] = {}
+    conf['linux']['resources']['unified'] = {
+            "NOT-A-VALID-KEY": "doesntmatter"
+    }
+    cid = None
+    try:
+        out, cid = run_and_get_output(conf, command='run', detach=True)
+        # must raise an exception, fail if it doesn't.
+        return -1
+    except Exception as e:
+        if 'the specified key has not the form CONTROLLER.VALUE `NOT-A-VALID-KEY`' in e.stdout.decode("utf-8").strip():
+            return 0
+        return -1
+    finally:
+        if cid is not None:
+            run_crun_command(["delete", "-f", cid])
+    return 0
+
+def test_resources_unified():
+    if not is_cgroup_v2_unified() or os.geteuid() != 0:
+        return 77
+
+    conf = base_config()
+    add_all_namespaces(conf, cgroupns=True)
+    conf['process']['args'] = ['/init', 'pause']
+
+    conf['linux']['resources'] = {}
+    conf['linux']['resources']['unified'] = {
+            "memory.high": "1073741824"
+    }
+    cid = None
+    try:
+        _, cid = run_and_get_output(conf, command='run', detach=True)
+        out = run_crun_command(["exec", cid, "/init", "cat", "/sys/fs/cgroup/memory.high"])
+        if "1073741824" not in out:
+            return -1
+    finally:
+        if cid is not None:
+            run_crun_command(["delete", "-f", cid])
+    return 0
+
+
+
 all_tests = {
     "resources-pid-limit" : test_resources_pid_limit,
+    "resources-unified" : test_resources_unified,
+    "resources-unified-invalid-controller" : test_resources_unified_invalid_controller,
+    "resources-unified-invalid-key" : test_resources_unified_invalid_key,
 }
 
 if __name__ == "__main__":

tests/tests_utils.py

@@ -144,11 +144,14 @@ def parse_proc_status(content):
         r[k] = v.strip()
     return r
 
-def add_all_namespaces(conf):
+def add_all_namespaces(conf, cgroupns=False):
     has = {}
     for i in conf['linux']['namespaces']:
         has[i['type']] = i['type']
-    for i in ['pid', 'user', 'ipc', 'uts', 'network']:
+    namespaces = ['pid', 'user', 'ipc', 'uts', 'network']
+    if cgroupns:
+        namespaces = namespaces + ["cgroup"]
+    for i in namespaces:
         if i not in has:
             conf['linux']['namespaces'].append({"type" : i})