The Tor Browser: tools/reorder/mcount.c@6474c204b198

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     1 /* This Source Code Form is subject to the terms of the Mozilla Public

     2  * License, v. 2.0. If a copy of the MPL was not distributed with this

     3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     5 /*

     7   A library that can be LD_PRELOAD-ed to dump a function's address on

     8   function entry.

    10  */

    12 #include <unistd.h>

    14 /**

    15  * When compiled with `-pg' (or even just `-p'), gcc inserts a call to

    16  * |mcount| in each function prologue. This implementation of |mcount|

    17  * will grab the return address from the stack, and write it to stdout

    18  * as a binary stream, creating a gross execution trace the

    19  * instrumented program.

    20  *

    21  * For more info on gcc inline assembly, see:

    22  *

    23  *   <http://www.ibm.com/developerworks/linux/library/l-ia.html?dwzone=linux>

    24  *

    25  */

    26 void

    27 mcount()

    28 {

    29     register unsigned int caller;

    30     unsigned int buf[1];

    32     // Grab the return address.

    33     asm("movl 4(%%esp),%0"

    34         : "=r"(caller));

    36     buf[0] = caller;

    37     write(STDOUT_FILENO, buf, sizeof buf[0]);

    38 }

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