csu/initfini.c

   1 /* Special .init and .fini section support.
   2 Copyright (C) 1995, 1996 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 Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 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 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 /* This file is compiled into assembly code which is then surrounded by the
  21    lines `cat > crtcommon.tmp <<\EOF_common' and `EOF_common' and thus
  22    becomes a shell script which creates three files of assembly code.
  23
  24    * The first file is crti.s-new; this puts a function prologue at the
  25    beginning of the .init and .fini sections and defines global symbols for
  26    those addresses, so they can be called as functions.
  27
  28    * The second file is crtn.s-new; this puts the corresponding function
  29    epilogues in the .init and .fini sections.
  30
  31    * The third file is crtcommon.tmp, which is whatever miscellaneous cruft
  32    the compiler generated at the end; it should be appended to both crti.s-new
  33    and crtn.s-new.  */
  34
  35 #include <stdlib.h>
  36
  37
  38 #ifdef HAVE_ELF
  39 /* These declarations make the functions go in the right sections when
  40    we define them below.  GCC syntax does not allow the attribute
  41    specifications to be in the function definitions themselves.  */
  42 void _init (void) __attribute__ ((section (".init")));
  43 void _fini (void) __attribute__ ((section (".fini")));
  44
  45 #define SECTION(x)              /* Put nothing extra before the defn.  */
  46
  47 #else
  48 /* Some non-ELF systems support .init and .fini sections,
  49    but the __attribute__ syntax only works for ELF.  */
  50 #define SECTION(x) asm (".section " x);
  51 #endif
  52
  53 /* End the here document containing the initial common code.
  54    Then move the output file crtcommon.tmp to crti.s-new and crtn.s-new.  */
  55 asm ("\nEOF_common\n\
  56 rm -f crti.s-new crtn.s-new\n\
  57 mv crtcommon.tmp crti.s-new\n\
  58 cp crti.s-new crtn.s-new");
  59
  60 /* Append the .init prologue to crti.s-new.  */
  61 asm ("cat >> crti.s-new <<\\EOF.crti.init");
  62
  63 SECTION (".init")
  64 void
  65 _init (void)
  66 {
  67   /* We cannot use the normal constructor mechanism in gcrt1.o because it
  68      appears before crtbegin.o in the link, so the header elt of .ctors
  69      would come after the elt for __gmon_start__.  One approach is for
  70      gcrt1.o to reference a symbol which would be defined by some library
  71      module which has a constructor; but then user code's constructors
  72      would come first, and not be profiled.  */
  73   extern void __gmon_start__ (void) __attribute__ ((weak));
  74   weak_symbol (__gmon_start__)
  75   if (__gmon_start__)
  76     __gmon_start__ ();
  77
  78   /* End the here document containing the .init prologue code.
  79      Then fetch the .section directive just written and append that
  80      to crtn.s-new, followed by the function epilogue.  */
  81   asm ("\nEOF.crti.init
  82 \n\
  83         fgrep .init crti.s-new >>crtn.s-new\n\
  84         cat >> crtn.s-new <<\\EOF.crtn.init");
  85 }
  86
  87 /* End the here document containing the .init epilogue code.
  88    Then append the .fini prologue to crti.s-new.  */
  89 asm ("\nEOF.crtn.init\
  90 \n\
  91 cat >> crti.s-new <<\\EOF.crti.fini");
  92
  93 SECTION (".fini")
  94 void
  95 _fini (void)
  96 {
  97   /* End the here document containing the .fini prologue code.
  98      Then fetch the .section directive just written and append that
  99      to crtn.s-new, followed by the function epilogue.  */
 100   asm ("\nEOF.crti.fini\
 101 \n\
 102 cat > /dev/null <<\\EOF.fini.skip");
 103
 104   {
 105     /* Let GCC know that _fini is not a leaf function by having a dummy
 106        function call here.  We arrange for this call to be omitted from
 107        either crt file.  */
 108     extern void i_am_not_a_leaf (void);
 109     i_am_not_a_leaf ();
 110   }
 111
 112   asm ("\nEOF.fini.skip\
 113 \n\
 114         fgrep .fini crti.s-new >>crtn.s-new\n\
 115         cat >> crtn.s-new <<\\EOF.crtn.fini");
 116 }
 117
 118 /* End the here document containing the .fini epilogue code.
 119    Finally, put the remainder of the generated assembly into crtcommon.tmp.  */
 120 asm ("\nEOF.crtn.fini\
 121 \n\
 122 cat > crtcommon.tmp <<\\EOF_common");