The Tor Browser / file comparison
comparison: tools/reorder/mcount.c
tools/reorder/mcount.c
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:5e90d2a41647 |
|---|---|
| 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/. */ | |
| 4 | |
| 5 /* | |
| 6 | |
| 7 A library that can be LD_PRELOAD-ed to dump a function's address on | |
| 8 function entry. | |
| 9 | |
| 10 */ | |
| 11 | |
| 12 #include <unistd.h> | |
| 13 | |
| 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]; | |
| 31 | |
| 32 // Grab the return address. | |
| 33 asm("movl 4(%%esp),%0" | |
| 34 : "=r"(caller)); | |
| 35 | |
| 36 buf[0] = caller; | |
| 37 write(STDOUT_FILENO, buf, sizeof buf[0]); | |
| 38 } |
