1/* Code to enable profiling at program startup.
2 Copyright (C) 1995-2023 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
42/* Use __executable_start as the lowest address to keep profiling records
43 if it provided by the linker. */
44extern const char __executable_start[] __attribute__ ((visibility ("hidden")));
45
46extern char etext[];
47
48#if !ELF_INITFINI
49/* Instead of defining __gmon_start__ globally in gcrt1.o, we make it
50 static and just put a pointer to it into the .preinit_array
51 section. */
52# define GMON_START_ARRAY_SECTION ".preinit_array"
53#endif
54
55#ifdef GMON_START_ARRAY_SECTION
56static void __gmon_start__ (void);
57static void (*const gmon_start_initializer) (void)
58 __attribute__ ((used, section (GMON_START_ARRAY_SECTION))) = &__gmon_start__;
59static
60#else
61/* We cannot use the normal constructor mechanism to call
62 __gmon_start__ because gcrt1.o appears before crtbegin.o in the link.
63 Instead crti.o calls it specially. */
64extern void __gmon_start__ (void);
65#endif
66
67void
68__gmon_start__ (void)
69{
70 /* Protect from being called more than once. Since crti.o is linked
71 into every shared library, each of their init functions will call us. */
72 static int called;
73
74 if (called)
75 return;
76
77 called = 1;
78
79 /* Start keeping profiling records. */
80 __monstartup ((u_long) &__executable_start, (u_long) &etext);
81
82 /* Call _mcleanup before exiting; it will write out gmon.out from the
83 collected data. */
84 atexit (&_mcleanup);
85}
86