tools/reorder/mcount.c@6474c204b198 (annotated)
tools/reorder/mcount.c
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
| michael@0 | 1 | /* This Source Code Form is subject to the terms of the Mozilla Public |
| michael@0 | 2 | * License, v. 2.0. If a copy of the MPL was not distributed with this |
| michael@0 | 3 | * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| michael@0 | 4 | |
| michael@0 | 5 | /* |
| michael@0 | 6 | |
| michael@0 | 7 | A library that can be LD_PRELOAD-ed to dump a function's address on |
| michael@0 | 8 | function entry. |
| michael@0 | 9 | |
| michael@0 | 10 | */ |
| michael@0 | 11 | |
| michael@0 | 12 | #include <unistd.h> |
| michael@0 | 13 | |
| michael@0 | 14 | /** |
| michael@0 | 15 | * When compiled with `-pg' (or even just `-p'), gcc inserts a call to |
| michael@0 | 16 | * |mcount| in each function prologue. This implementation of |mcount| |
| michael@0 | 17 | * will grab the return address from the stack, and write it to stdout |
| michael@0 | 18 | * as a binary stream, creating a gross execution trace the |
| michael@0 | 19 | * instrumented program. |
| michael@0 | 20 | * |
| michael@0 | 21 | * For more info on gcc inline assembly, see: |
| michael@0 | 22 | * |
| michael@0 | 23 | * <http://www.ibm.com/developerworks/linux/library/l-ia.html?dwzone=linux> |
| michael@0 | 24 | * |
| michael@0 | 25 | */ |
| michael@0 | 26 | void |
| michael@0 | 27 | mcount() |
| michael@0 | 28 | { |
| michael@0 | 29 | register unsigned int caller; |
| michael@0 | 30 | unsigned int buf[1]; |
| michael@0 | 31 | |
| michael@0 | 32 | // Grab the return address. |
| michael@0 | 33 | asm("movl 4(%%esp),%0" |
| michael@0 | 34 | : "=r"(caller)); |
| michael@0 | 35 | |
| michael@0 | 36 | buf[0] = caller; |
| michael@0 | 37 | write(STDOUT_FILENO, buf, sizeof buf[0]); |
| michael@0 | 38 | } |
