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, write to the Free
  34    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  35    02111-1307 USA.  */
  36
  37 /* This file is compiled into assembly code which is then munged by a sed
  38    script into two files: crti.s and crtn.s.
  39
  40    * crti.s puts a function prologue at the beginning of the
  41    .init and .fini sections and defines global symbols for
  42    those addresses, so they can be called as functions.
  43
  44    * crtn.s puts the corresponding function epilogues
  45    in the .init and .fini sections. */
  46
  47 #include <stdlib.h>
  48
  49 /* We use embedded asm for .section unconditionally, as this makes it
  50    easier to insert the necessary directives into crtn.S. */
  51 #define SECTION(x) asm (".section " x )
  52
  53 /* Embed an #include to pull in the alignment and .end directives. */
  54 asm ("\n#include \"defs.h\"");
  55
  56 /* The initial common code ends here. */
  57 asm ("\n/*@HEADER_ENDS*/");
  58
  59 /* To determine whether we need .end and .align: */
  60 asm ("\n/*@TESTS_BEGIN*/");
  61 extern void dummy (void (*foo) (void));
  62 void
  63 dummy (void (*foo) (void))
  64 {
  65   if (foo)
  66     (*foo) ();
  67 }
  68 asm ("\n/*@TESTS_END*/");
  69
  70 /* The beginning of _init:  */
  71 asm ("\n/*@_init_PROLOG_BEGINS*/");
  72
  73 static void
  74 call_gmon_start(void)
  75 {
  76   extern void __gmon_start__ (void) __attribute__ ((weak)); /*weak_extern (__gmon_start__);*/
  77   void (*gmon_start) (void) = __gmon_start__;
  78
  79   if (gmon_start)
  80     gmon_start ();
  81 }
  82
  83 SECTION (".init");
  84 extern void _init (void);
  85 void
  86 _init (void)
  87 {
  88   /* We cannot use the normal constructor mechanism in gcrt1.o because it
  89      appears before crtbegin.o in the link, so the header elt of .ctors
  90      would come after the elt for __gmon_start__.  One approach is for
  91      gcrt1.o to reference a symbol which would be defined by some library
  92      module which has a constructor; but then user code's constructors
  93      would come first, and not be profiled.  */
  94   call_gmon_start ();
  95
  96   asm ("ALIGN");
  97   asm("END_INIT");
  98   /* Now the epilog. */
  99   asm ("\n/*@_init_PROLOG_ENDS*/");
 100   asm ("\n/*@_init_EPILOG_BEGINS*/");
 101   SECTION(".init");
 102 }
 103 asm ("END_INIT");
 104
 105 /* End of the _init epilog, beginning of the _fini prolog. */
 106 asm ("\n/*@_init_EPILOG_ENDS*/");
 107 asm ("\n/*@_fini_PROLOG_BEGINS*/");
 108
 109 SECTION (".fini");
 110 extern void _fini (void);
 111 void
 112 _fini (void)
 113 {
 114
 115   /* End of the _fini prolog. */
 116   asm ("ALIGN");
 117   asm ("END_FINI");
 118   asm ("\n/*@_fini_PROLOG_ENDS*/");
 119
 120   {
 121     /* Let GCC know that _fini is not a leaf function by having a dummy
 122        function call here.  We arrange for this call to be omitted from
 123        either crt file.  */
 124     extern void i_am_not_a_leaf (void);
 125     i_am_not_a_leaf ();
 126   }
 127
 128   /* Beginning of the _fini epilog. */
 129   asm ("\n/*@_fini_EPILOG_BEGINS*/");
 130   SECTION (".fini");
 131 }
 132 asm ("END_FINI");
 133
 134 /* End of the _fini epilog.  Any further generated assembly (e.g. .ident)
 135    is shared between both crt files. */
 136 asm ("\n/*@_fini_EPILOG_ENDS*/");
 137 asm ("\n/*@TRAILER_BEGINS*/");
 138
 139 /* End of file. */