csu/gmon-start.c

   1 /* Code to enable profiling at program startup.
   2    Copyright (C) 1995-2021 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    <https://www.gnu.org/licenses/>.  */
  35
  36 #include <sys/types.h>
  37 #include <sys/gmon.h>
  38 #include <stdlib.h>
  39 #include <unistd.h>
  40 #include <elf-initfini.h>
  41 #define __ASSEMBLY__
  42 #include <entry.h>
  43
  44 /* Beginning and end of our code segment. We cannot declare them
  45    as the external functions since we want the addresses of those
  46    labels. Taking the address of a function may have different
  47    meanings on different platforms. */
  48 #ifdef ENTRY_POINT_DECL
  49 ENTRY_POINT_DECL(extern)
  50 #else
  51 extern char ENTRY_POINT[];
  52 #endif
  53 extern char etext[];
  54
  55 #ifndef TEXT_START
  56 # ifdef ENTRY_POINT_DECL
  57 #  define TEXT_START ENTRY_POINT
  58 # else
  59 #  define TEXT_START &ENTRY_POINT
  60 # endif
  61 #endif
  62
  63 #if !ELF_INITFINI
  64 /* Instead of defining __gmon_start__ globally in gcrt1.o, we make it
  65    static and just put a pointer to it into the .preinit_array
  66    section.  */
  67 # define GMON_START_ARRAY_SECTION ".preinit_array"
  68 #endif
  69
  70 #ifdef GMON_START_ARRAY_SECTION
  71 static void __gmon_start__ (void);
  72 static void (*const gmon_start_initializer) (void)
  73   __attribute__ ((used, section (GMON_START_ARRAY_SECTION))) = &__gmon_start__;
  74 static
  75 #else
  76 /* We cannot use the normal constructor mechanism to call
  77    __gmon_start__ because gcrt1.o appears before crtbegin.o in the link.
  78    Instead crti.o calls it specially.  */
  79 extern void __gmon_start__ (void);
  80 #endif
  81
  82 void
  83 __gmon_start__ (void)
  84 {
  85   /* Protect from being called more than once.  Since crti.o is linked
  86      into every shared library, each of their init functions will call us.  */
  87   static int called;
  88
  89   if (called)
  90     return;
  91
  92   called = 1;
  93
  94   /* Start keeping profiling records.  */
  95   __monstartup ((u_long) TEXT_START, (u_long) &etext);
  96
  97   /* Call _mcleanup before exiting; it will write out gmon.out from the
  98      collected data.  */
  99   atexit (&_mcleanup);
 100 }