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
  11    In addition to the permissions in the GNU Lesser General Public
  12    License, the Free Software Foundation gives you unlimited
  13    permission to link the compiled version of this file with other
  14    programs, and to distribute those programs without any restriction
  15    coming from the use of this file.  (The GNU Lesser General Public
  16    License restrictions do apply in other respects; for example, they
  17    cover modification of the file, and distribution when not linked
  18    into another program.)
  19
  20    The GNU C Library is distributed in the hope that it will be useful,
  21    but WITHOUT ANY WARRANTY; without even the implied warranty of
  22    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  23    Lesser General Public License for more details.
  24
  25    You should have received a copy of the GNU Lesser General Public
  26    License along with the GNU C Library; if not, write to the Free
  27    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  28    02111-1307 USA.  */
  29
  30 /* This file is compiled into assembly code which is then munged by a sed
  31    script into two files: crti.s and crtn.s.
  32
  33    * crti.s puts a function prologue at the beginning of the
  34    .init and .fini sections and defines global symbols for
  35    those addresses, so they can be called as functions.
  36
  37    * crtn.s puts the corresponding function epilogues
  38    in the .init and .fini sections. */
  39
  40 #include <stdlib.h>
  41
  42 /* We use embedded asm for .section unconditionally, as this makes it
  43    easier to insert the necessary directives into crtn.S. */
  44 #define SECTION(x) asm (".section " x )
  45
  46 /* Embed an #include to pull in the alignment and .end directives. */
  47 asm ("\n#include \"defs.h\"");
  48
  49 /* The initial common code ends here. */
  50 asm ("\n/*@HEADER_ENDS*/");
  51
  52 /* To determine whether we need .end and .align: */
  53 asm ("\n/*@TESTS_BEGIN*/");
  54 extern void dummy (void (*foo) (void));
  55 void
  56 dummy (void (*foo) (void))
  57 {
  58   if (foo)
  59     (*foo) ();
  60 }
  61 asm ("\n/*@TESTS_END*/");
  62
  63 /* The beginning of _init:  */
  64 asm ("\n/*@_init_PROLOG_BEGINS*/");
  65
  66 static void
  67 call_gmon_start(void)
  68 {
  69   extern void __gmon_start__ (void) __attribute__ ((weak)); /*weak_extern (__gmon_start__);*/
  70   void (*gmon_start) (void) = __gmon_start__;
  71
  72   if (gmon_start)
  73     gmon_start ();
  74 }
  75
  76 SECTION (".init");
  77 extern void _init (void);
  78 void
  79 _init (void)
  80 {
  81   /* We cannot use the normal constructor mechanism in gcrt1.o because it
  82      appears before crtbegin.o in the link, so the header elt of .ctors
  83      would come after the elt for __gmon_start__.  One approach is for
  84      gcrt1.o to reference a symbol which would be defined by some library
  85      module which has a constructor; but then user code's constructors
  86      would come first, and not be profiled.  */
  87   call_gmon_start ();
  88
  89   asm ("ALIGN");
  90   asm("END_INIT");
  91   /* Now the epilog. */
  92   asm ("\n/*@_init_PROLOG_ENDS*/");
  93   asm ("\n/*@_init_EPILOG_BEGINS*/");
  94   SECTION(".init");
  95 }
  96 asm ("END_INIT");
  97
  98 /* End of the _init epilog, beginning of the _fini prolog. */
  99 asm ("\n/*@_init_EPILOG_ENDS*/");
 100 asm ("\n/*@_fini_PROLOG_BEGINS*/");
 101
 102 SECTION (".fini");
 103 extern void _fini (void);
 104 void
 105 _fini (void)
 106 {
 107
 108   /* End of the _fini prolog. */
 109   asm ("ALIGN");
 110   asm ("END_FINI");
 111   asm ("\n/*@_fini_PROLOG_ENDS*/");
 112
 113   {
 114     /* Let GCC know that _fini is not a leaf function by having a dummy
 115        function call here.  We arrange for this call to be omitted from
 116        either crt file.  */
 117     extern void i_am_not_a_leaf (void);
 118     i_am_not_a_leaf ();
 119   }
 120
 121   /* Beginning of the _fini epilog. */
 122   asm ("\n/*@_fini_EPILOG_BEGINS*/");
 123   SECTION (".fini");
 124 }
 125 asm ("END_FINI");
 126
 127 /* End of the _fini epilog.  Any further generated assembly (e.g. .ident)
 128    is shared between both crt files. */
 129 asm ("\n/*@_fini_EPILOG_ENDS*/");
 130 asm ("\n/*@TRAILER_BEGINS*/");
 131
 132 /* End of file. */