2012-05-21 04:12:37 -07:00
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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2007-03-22 10:30:00 -07:00
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/*
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A library that can be LD_PRELOAD-ed to dump a function's address on
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function entry.
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*/
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#include <unistd.h>
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/**
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* When compiled with `-pg' (or even just `-p'), gcc inserts a call to
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* |mcount| in each function prologue. This implementation of |mcount|
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* will grab the return address from the stack, and write it to stdout
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* as a binary stream, creating a gross execution trace the
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* instrumented program.
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*
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* For more info on gcc inline assembly, see:
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*
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* <http://www.ibm.com/developerworks/linux/library/l-ia.html?dwzone=linux>
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*
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*/
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void
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mcount()
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{
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register unsigned int caller;
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unsigned int buf[1];
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// Grab the return address.
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asm("movl 4(%%esp),%0"
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: "=r"(caller));
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buf[0] = caller;
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write(STDOUT_FILENO, buf, sizeof buf[0]);
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}
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