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macro: add helper for module origin id

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These need to be redefined in every module that we need to guard, so add
a macro
This commit is contained in:
Luca Boccassi 2023-04-25 00:37:51 +01:00
parent 7d9f6034a9
commit bf2d930fa1
1 changed files with 36 additions and 0 deletions
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src/basic/origin-id.h Normal file
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include <pthread.h>
#include "random-util.h"
/* This pattern needs to be repeated exactly in multiple modules, so macro it.
* To ensure an object is not passed into a different module (e.g.: when two shared objects statically
* linked to libsystemd get loaded in the same process, and the object created by one is passed to the
* other, see https://github.com/systemd/systemd/issues/27216), create a random static global random
* (mixed with PID, so that we can also check for reuse after fork) that is stored in the object and
* checked by public API on use. */
#define _DEFINE_ORIGIN_ID_HELPERS(type, name, scope) \
static uint64_t origin_id; \
\
static void origin_id_initialize(void) { \
origin_id = random_u64(); \
} \
\
static uint64_t origin_id_query(void) { \
static pthread_once_t once = PTHREAD_ONCE_INIT; \
assert_se(pthread_once(&once, origin_id_initialize) == 0); \
return origin_id ^ getpid_cached(); \
} \
\
scope bool name##_origin_changed(type *p) { \
assert(p); \
return p->origin_id != origin_id_query(); \
}
#define DEFINE_ORIGIN_ID_HELPERS(type, name) \
_DEFINE_ORIGIN_ID_HELPERS(type, name,);
#define DEFINE_PRIVATE_ORIGIN_ID_HELPERS(type, name) \
_DEFINE_ORIGIN_ID_HELPERS(type, name, static);