sysdeps/generic/initfini.c

   1 /* Special .init and .fini section support.
   2    Copyright (C) 1995, 1996, 1997, 2000 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    In addition to the permissions in the GNU Lesser General Public
  11    License, the Free Software Foundation gives you unlimited
  12    permission to link the compiled version of this file with other
  13    programs, and to distribute those programs without any restriction
  14    coming from the use of this file. (The GNU Lesser General Public
  15    License restrictions do apply in other respects; for example, they
  16    cover modification of the file, and distribution when not linked
  17    into another program.)
  18
  19    Note that people who make modified versions of this file are not
  20    obligated to grant this special exception for their modified
  21    versions; it is their choice whether to do so. The GNU Lesser
  22    General Public License gives permission to release a modified
  23    version without this exception; this exception also makes it
  24    possible to release a modified version which carries forward this
  25    exception.
  26
  27    The GNU C Library is distributed in the hope that it will be useful,
  28    but WITHOUT ANY WARRANTY; without even the implied warranty of
  29    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  30    Lesser General Public License for more details.
  31
  32    You should have received a copy of the GNU Lesser General Public
  33    License along with the GNU C Library; if not, see
  34    <http://www.gnu.org/licenses/>.  */
  35
  36 /* This file is compiled into assembly code which is then munged by a sed
  37    script into two files: crti.s and crtn.s.
  38
  39    * crti.s puts a function prologue at the beginning of the
  40    .init and .fini sections and defines global symbols for
  41    those addresses, so they can be called as functions.
  42
  43    * crtn.s puts the corresponding function epilogues
  44    in the .init and .fini sections. */
  45
  46 #include <stdlib.h>
  47
  48 /* We use embedded asm for .section unconditionally, as this makes it
  49    easier to insert the necessary directives into crtn.S. */
  50 #define SECTION(x) asm (".section " x )
  51
  52 /* Embed an #include to pull in the alignment and .end directives. */
  53 asm ("\n#include \"defs.h\"");
  54
  55 /* The initial common code ends here. */
  56 asm ("\n/*@HEADER_ENDS*/");
  57
  58 /* To determine whether we need .end and .align: */
  59 asm ("\n/*@TESTS_BEGIN*/");
  60 extern void dummy (void (*foo) (void));
  61 void
  62 dummy (void (*foo) (void))
  63 {
  64   if (foo)
  65     (*foo) ();
  66 }
  67 asm ("\n/*@TESTS_END*/");
  68
  69 /* The beginning of _init:  */
  70 asm ("\n/*@_init_PROLOG_BEGINS*/");
  71
  72 static void
  73 call_gmon_start(void)
  74 {
  75   extern void __gmon_start__ (void) __attribute__ ((weak)); /*weak_extern (__gmon_start__);*/
  76   void (*gmon_start) (void) = __gmon_start__;
  77
  78   if (gmon_start)
  79     gmon_start ();
  80 }
  81
  82 SECTION (".init");
  83 extern void __attribute__ ((section (".init"))) _init (void);
  84 void
  85 _init (void)
  86 {
  87   /* We cannot use the normal constructor mechanism in gcrt1.o because it
  88      appears before crtbegin.o in the link, so the header elt of .ctors
  89      would come after the elt for __gmon_start__.  One approach is for
  90      gcrt1.o to reference a symbol which would be defined by some library
  91      module which has a constructor; but then user code's constructors
  92      would come first, and not be profiled.  */
  93   call_gmon_start ();
  94
  95   asm ("ALIGN");
  96   asm("END_INIT");
  97   /* Now the epilog. */
  98   asm ("\n/*@_init_PROLOG_ENDS*/");
  99   asm ("\n/*@_init_EPILOG_BEGINS*/");
 100   SECTION(".init");
 101 }
 102 asm ("END_INIT");
 103
 104 /* End of the _init epilog, beginning of the _fini prolog. */
 105 asm ("\n/*@_init_EPILOG_ENDS*/");
 106 asm ("\n/*@_fini_PROLOG_BEGINS*/");
 107
 108 SECTION (".fini");
 109 extern void __attribute__ ((section (".fini"))) _fini (void);
 110 void
 111 _fini (void)
 112 {
 113
 114   /* End of the _fini prolog. */
 115   asm ("ALIGN");
 116   asm ("END_FINI");
 117   asm ("\n/*@_fini_PROLOG_ENDS*/");
 118
 119   {
 120     /* Let GCC know that _fini is not a leaf function by having a dummy
 121        function call here.  We arrange for this call to be omitted from
 122        either crt file.  */
 123     extern void i_am_not_a_leaf (void);
 124     i_am_not_a_leaf ();
 125   }
 126
 127   /* Beginning of the _fini epilog. */
 128   asm ("\n/*@_fini_EPILOG_BEGINS*/");
 129   SECTION (".fini");
 130 }
 131 asm ("END_FINI");
 132
 133 /* End of the _fini epilog.  Any further generated assembly (e.g. .ident)
 134    is shared between both crt files. */
 135 asm ("\n/*@_fini_EPILOG_ENDS*/");
 136 asm ("\n/*@TRAILER_BEGINS*/");
 137
 138 /* End of file. */