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84a7eb1f87
Glibc assumes that ENTRY_POINT is the lowest address for which we need
to keep profiling records and BFD linker uses a linker script to place
the input sections.
Starting from GCC 4.6, the main function is placed in .text.startup
section and starting from binutils 2.22, BFD linker with
commit add44f8d5c5c05e08b11e033127a744d61c26aee
Author: Alan Modra <amodra@gmail.com>
Date: Thu Nov 25 03:03:02 2010 +0000
* scripttempl/elf.sc: Group .text.exit, text.startup and .text.hot
sections.
places .text.startup section before .text section, which leave the main
function out of profiling records.
Starting from binutils 2.15, linker provides __executable_start to mark
the lowest address of the executable. Use __executable_start as the
lowest address to keep the main function in profiling records. This fixes
[BZ #28153].
Tested on Linux/x86-64, Linux/x32 and Linux/i686 as well as with
build-many-glibcs.py.
109 lines
3.7 KiB
C
109 lines
3.7 KiB
C
/* Code to enable profiling at program startup.
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Copyright (C) 1995-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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In addition to the permissions in the GNU Lesser General Public
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License, the Free Software Foundation gives you unlimited
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permission to link the compiled version of this file with other
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programs, and to distribute those programs without any restriction
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coming from the use of this file. (The GNU Lesser General Public
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License restrictions do apply in other respects; for example, they
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cover modification of the file, and distribution when not linked
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into another program.)
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Note that people who make modified versions of this file are not
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obligated to grant this special exception for their modified
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versions; it is their choice whether to do so. The GNU Lesser
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General Public License gives permission to release a modified
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version without this exception; this exception also makes it
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possible to release a modified version which carries forward this
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exception.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <sys/types.h>
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#include <sys/gmon.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <elf-initfini.h>
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#define __ASSEMBLY__
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#include <entry.h>
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/* Beginning and end of our code segment. We cannot declare them
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as the external functions since we want the addresses of those
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labels. Taking the address of a function may have different
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meanings on different platforms. */
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#ifdef ENTRY_POINT_DECL
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ENTRY_POINT_DECL(extern)
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#else
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extern char ENTRY_POINT[];
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#endif
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extern char etext[];
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/* Use __executable_start as the lowest address to keep profiling records
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if it provided by the linker. */
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extern const char executable_start[] asm ("__executable_start")
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__attribute__ ((weak, visibility ("hidden")));
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#ifndef TEXT_START
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# ifdef ENTRY_POINT_DECL
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# define TEXT_START ENTRY_POINT
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# else
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# define TEXT_START &ENTRY_POINT
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# endif
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#endif
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#if !ELF_INITFINI
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/* Instead of defining __gmon_start__ globally in gcrt1.o, we make it
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static and just put a pointer to it into the .preinit_array
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section. */
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# define GMON_START_ARRAY_SECTION ".preinit_array"
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#endif
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#ifdef GMON_START_ARRAY_SECTION
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static void __gmon_start__ (void);
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static void (*const gmon_start_initializer) (void)
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__attribute__ ((used, section (GMON_START_ARRAY_SECTION))) = &__gmon_start__;
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static
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#else
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/* We cannot use the normal constructor mechanism to call
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__gmon_start__ because gcrt1.o appears before crtbegin.o in the link.
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Instead crti.o calls it specially. */
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extern void __gmon_start__ (void);
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#endif
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void
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__gmon_start__ (void)
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{
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/* Protect from being called more than once. Since crti.o is linked
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into every shared library, each of their init functions will call us. */
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static int called;
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if (called)
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return;
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called = 1;
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/* Start keeping profiling records. */
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if (&executable_start != NULL)
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__monstartup ((u_long) &executable_start, (u_long) &etext);
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else
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__monstartup ((u_long) TEXT_START, (u_long) &etext);
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/* Call _mcleanup before exiting; it will write out gmon.out from the
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collected data. */
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atexit (&_mcleanup);
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}
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