src/basic/origin-id.h

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2 #pragma once
   3
   4 #include <pthread.h>
   5
   6 #include "random-util.h"
   7
   8 /* This pattern needs to be repeated exactly in multiple modules, so macro it.
   9  * To ensure an object is not passed into a different module (e.g.: when two shared objects statically
  10  * linked to libsystemd get loaded in the same process, and the object created by one is passed to the
  11  * other, see https://github.com/systemd/systemd/issues/27216), create a random static global random
  12  * (mixed with PID, so that we can also check for reuse after fork) that is stored in the object and
  13  * checked by public API on use. */
  14 #define _DEFINE_ORIGIN_ID_HELPERS(type, name, scope)                  \
  15 static uint64_t origin_id;                                            \
  16                                                                       \
  17 static void origin_id_initialize(void) {                              \
  18         origin_id = random_u64();                                     \
  19 }                                                                     \
  20                                                                       \
  21 static uint64_t origin_id_query(void) {                               \
  22         static pthread_once_t once = PTHREAD_ONCE_INIT;               \
  23         assert_se(pthread_once(&once, origin_id_initialize) == 0);    \
  24         return origin_id ^ getpid_cached();                           \
  25 }                                                                     \
  26                                                                       \
  27 scope bool name##_origin_changed(type *p) {                           \
  28         assert(p);                                                    \
  29         return p->origin_id != origin_id_query();                     \
  30 }
  31
  32 #define DEFINE_ORIGIN_ID_HELPERS(type, name)                          \
  33         _DEFINE_ORIGIN_ID_HELPERS(type, name,);
  34
  35 #define DEFINE_PRIVATE_ORIGIN_ID_HELPERS(type, name)                  \
  36         _DEFINE_ORIGIN_ID_HELPERS(type, name, static);