hurd/set-hooks.h

   1 /* Macros for using symbol sets for running lists of functions.
   2    Copyright (C) 1994-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _SET_HOOKS_H
  20 #define _SET_HOOKS_H 1
  21
  22 #define __need_size_t
  23 #include <stddef.h>
  24 #include <sys/cdefs.h>
  25 #include <libc-symbols.h>
  26
  27 #include "set-hooks-arch.h"
  28
  29 #ifdef symbol_set_define
  30 /* Define a hook variable called NAME.  Functions put on this hook take
  31    arguments described by PROTO.  Use `text_set_element (NAME, FUNCTION)'
  32    from include/libc-symbols.h to add a function to the hook.  */
  33
  34 # define DEFINE_HOOK(NAME, PROTO)               \
  35   typedef void __##NAME##_hook_function_t PROTO; \
  36   symbol_set_define (NAME)
  37
  38 # define DECLARE_HOOK(NAME, PROTO)              \
  39   typedef void __##NAME##_hook_function_t PROTO;\
  40   symbol_set_declare (NAME)
  41
  42 /* Run all the functions hooked on the set called NAME.
  43    Each function is called like this: `function ARGS'.  */
  44
  45 # define RUN_HOOK(NAME, ARGS)                                                 \
  46 do {                                                                          \
  47   void *const *ptr;                                                   \
  48   for (ptr = (void *const *) symbol_set_first_element (NAME);                 \
  49        ! symbol_set_end_p (NAME, ptr); ++ptr)                                 \
  50     (*(__##NAME##_hook_function_t *) *ptr) ARGS;                              \
  51 } while (0)
  52
  53 /* Define a hook variable with NAME and PROTO, and a function called RUNNER
  54    which calls each function on the hook in turn, with ARGS.  */
  55
  56 # define DEFINE_HOOK_RUNNER(name, runner, proto, args) \
  57 DEFINE_HOOK (name, proto); \
  58 extern void runner proto; void runner proto { RUN_HOOK (name, args); }
  59
  60 # ifdef SET_RELHOOK
  61 /* This is similar to RUN_RELHOOK, but the hooks were registered with
  62  * SET_RELHOOK so that a relative offset was computed by the linker
  63  * rather than an absolute address by the dynamic linker. */
  64 #  define RUN_RELHOOK(NAME, ARGS)                                     \
  65 do {                                                                  \
  66   void *const *ptr;                                                   \
  67   for (ptr = (void *const *) symbol_set_first_element (NAME);         \
  68        ! symbol_set_end_p (NAME, ptr); ++ptr) {                       \
  69     __##NAME##_hook_function_t *f =                                   \
  70         (void*) ((uintptr_t) ptr + (ptrdiff_t) *ptr);                 \
  71     (*f) ARGS;                                                        \
  72   } \
  73 } while (0)
  74 # else
  75 #  define SET_RELHOOK(NAME, HOOK) text_set_element (NAME, HOOK)
  76 #  define RUN_RELHOOK(NAME, ARGS) RUN_HOOK(NAME, ARGS)
  77 # endif
  78
  79 #else
  80
  81 /* The system does not provide necessary support for this.  */
  82 # define DEFINE_HOOK(NAME, PROTO)
  83
  84 # define DECLARE_HOOK(NAME, PROTO)
  85
  86 # define RUN_HOOK(NAME, ARGS)
  87
  88 # define DEFINE_HOOK_RUNNER(name, runner, proto, args)
  89
  90 # define SET_RELHOOK(NAME, HOOK)
  91
  92 # define RUN_RELHOOK(NAME, ARGS)
  93
  94 #endif
  95
  96 #endif /* set-hooks.h */