gecko/tools/reorder/mcount.c

71 lines
2.5 KiB
C

/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is ``mcount''
*
* The Initial Developer of the Original Code is Netscape
* Communications Corp. Portions created by the Initial Developer are
* Copyright (C) 2001 the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Chris Waterson <waterson@netscape.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/*
A library that can be LD_PRELOAD-ed to dump a function's address on
function entry.
*/
#include <unistd.h>
/**
* When compiled with `-pg' (or even just `-p'), gcc inserts a call to
* |mcount| in each function prologue. This implementation of |mcount|
* will grab the return address from the stack, and write it to stdout
* as a binary stream, creating a gross execution trace the
* instrumented program.
*
* For more info on gcc inline assembly, see:
*
* <http://www.ibm.com/developerworks/linux/library/l-ia.html?dwzone=linux>
*
*/
void
mcount()
{
register unsigned int caller;
unsigned int buf[1];
// Grab the return address.
asm("movl 4(%%esp),%0"
: "=r"(caller));
buf[0] = caller;
write(STDOUT_FILENO, buf, sizeof buf[0]);
}