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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:35:18 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:35:18 +0000 |
commit | b750101eb236130cf056c675997decbac904cc49 (patch) | |
tree | a5df1a06754bdd014cb975c051c83b01c9a97532 /src/basic/static-destruct.h | |
parent | Initial commit. (diff) | |
download | systemd-b750101eb236130cf056c675997decbac904cc49.tar.xz systemd-b750101eb236130cf056c675997decbac904cc49.zip |
Adding upstream version 252.22.upstream/252.22
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/basic/static-destruct.h')
-rw-r--r-- | src/basic/static-destruct.h | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/src/basic/static-destruct.h b/src/basic/static-destruct.h new file mode 100644 index 0000000..97baac7 --- /dev/null +++ b/src/basic/static-destruct.h @@ -0,0 +1,63 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#pragma once + +#include "alloc-util.h" +#include "macro.h" + +/* A framework for registering static variables that shall be freed on shutdown of a process. It's a bit like gcc's + * destructor attribute, but allows us to precisely schedule when we want to free the variables. This is supposed to + * feel a bit like the gcc cleanup attribute, but for static variables. Note that this does not work for static + * variables declared in .so's, as the list is private to the same linking unit. But maybe that's a good thing. */ + +typedef struct StaticDestructor { + void *data; + free_func_t destroy; +} StaticDestructor; + +#define STATIC_DESTRUCTOR_REGISTER(variable, func) \ + _STATIC_DESTRUCTOR_REGISTER(UNIQ, variable, func) + +#define _STATIC_DESTRUCTOR_REGISTER(uq, variable, func) \ + /* Type-safe destructor */ \ + static void UNIQ_T(static_destructor_wrapper, uq)(void *p) { \ + typeof(variable) *q = p; \ + func(q); \ + } \ + /* Older compilers don't know "retain" attribute. */ \ + _Pragma("GCC diagnostic ignored \"-Wattributes\"") \ + /* The actual destructor structure we place in a special section to find it. */ \ + _section_("SYSTEMD_STATIC_DESTRUCT") \ + /* Use pointer alignment, since that is apparently what gcc does for static variables. */ \ + _alignptr_ \ + /* Make sure this is not dropped from the image despite not being explicitly referenced. */ \ + _used_ \ + /* Prevent garbage collection by the linker. */ \ + _retain_ \ + /* Make sure that AddressSanitizer doesn't pad this variable: we want everything in this section + * packed next to each other so that we can enumerate it. */ \ + _variable_no_sanitize_address_ \ + static const StaticDestructor UNIQ_T(static_destructor_entry, uq) = { \ + .data = &(variable), \ + .destroy = UNIQ_T(static_destructor_wrapper, uq), \ + } + +/* Beginning and end of our section listing the destructors. We define these as weak as we want this to work + * even if no destructors are defined and the section is missing. */ +extern const struct StaticDestructor _weak_ __start_SYSTEMD_STATIC_DESTRUCT[]; +extern const struct StaticDestructor _weak_ __stop_SYSTEMD_STATIC_DESTRUCT[]; + +/* The function to destroy everything. (Note that this must be static inline, as it's key that it remains in + * the same linking unit as the variables we want to destroy.) */ +static inline void static_destruct(void) { + const StaticDestructor *d; + + if (!__start_SYSTEMD_STATIC_DESTRUCT) + return; + + d = ALIGN_PTR(__start_SYSTEMD_STATIC_DESTRUCT); + while (d < __stop_SYSTEMD_STATIC_DESTRUCT) { + d->destroy(d->data); + d = ALIGN_PTR(d + 1); + } +} |