Line data    Source code

       1             : #pragma once
       2             : 
       3             : #include "alloc-util.h"
       4             : #include "macro.h"
       5             : 
       6             : /* A framework for registering static variables that shall be freed on shutdown of a process. It's a bit like gcc's
       7             :  * destructor attribute, but allows us to precisely schedule when we want to free the variables. This is supposed to
       8             :  * feel a bit like the gcc cleanup attribute, but for static variables. Note that this does not work for static
       9             :  * variables declared in .so's, as the list is private to the same linking unit. But maybe that's a good thing. */
      10             : 
      11             : typedef struct StaticDestructor {
      12             :         void *data;
      13             :         free_func_t destroy;
      14             : } StaticDestructor;
      15             : 
      16             : #define STATIC_DESTRUCTOR_REGISTER(variable, func) \
      17             :         _STATIC_DESTRUCTOR_REGISTER(UNIQ, variable, func)
      18             : 
      19             : #define _STATIC_DESTRUCTOR_REGISTER(uq, variable, func)                 \
      20             :         /* Type-safe destructor */                                      \
      21             :         static void UNIQ_T(static_destructor_wrapper, uq)(void *p) {    \
      22             :                 typeof(variable) *q = p;                                \
      23             :                 func(q);                                                \
      24             :         }                                                               \
      25             :         /* The actual destructor structure we place in a special section to find it */ \
      26             :         _section_("SYSTEMD_STATIC_DESTRUCT")                            \
      27             :         /* We pick pointer alignment, since that is apparently what gcc does for static variables */ \
      28             :         _alignptr_                                                      \
      29             :         /* Make sure this is not dropped from the image because not explicitly referenced */ \
      30             :         _used_                                                          \
      31             :         /* 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. */ \
      32             :         _variable_no_sanitize_address_                                  \
      33             :         static const StaticDestructor UNIQ_T(static_destructor_entry, uq) = { \
      34             :                 .data = &(variable),                                    \
      35             :                 .destroy = UNIQ_T(static_destructor_wrapper, uq),       \
      36             :         }
      37             : 
      38             : /* Beginning and end of our section listing the destructors. We define these as weak as we want this to work even if
      39             :  * there's not a single destructor is defined in which case the section will be missing. */
      40             : extern const struct StaticDestructor _weak_ __start_SYSTEMD_STATIC_DESTRUCT[];
      41             : extern const struct StaticDestructor _weak_ __stop_SYSTEMD_STATIC_DESTRUCT[];
      42             : 
      43             : /* The function to destroy everything. (Note that this must be static inline, as it's key that it remains in the same
      44             :  * linking unit as the variables we want to destroy. */
      45         282 : static inline void static_destruct(void) {
      46             :         const StaticDestructor *d;
      47             : 
      48         282 :         if (!__start_SYSTEMD_STATIC_DESTRUCT)
      49         127 :                 return;
      50             : 
      51         155 :         d = ALIGN_TO_PTR(__start_SYSTEMD_STATIC_DESTRUCT, sizeof(void*));
      52        1026 :         while (d < __stop_SYSTEMD_STATIC_DESTRUCT) {
      53         871 :                 d->destroy(d->data);
      54         871 :                 d = ALIGN_TO_PTR(d + 1, sizeof(void*));
      55             :         }
      56             : }