| <html lang="en"> |
| <head> |
| <title>Patching - Debugging with GDB</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Debugging with GDB"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Altering.html#Altering" title="Altering"> |
| <link rel="prev" href="Calling.html#Calling" title="Calling"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, |
| 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
| Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Free Software'' and ``Free Software Needs |
| Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,'' |
| and with the Back-Cover Texts as in (a) below. |
| |
| (a) The FSF's Back-Cover Text is: ``You are free to copy and modify |
| this GNU Manual. Buying copies from GNU Press supports the FSF in |
| developing GNU and promoting software freedom.''--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Patching"></a> |
| <p> |
| Previous: <a rel="previous" accesskey="p" href="Calling.html#Calling">Calling</a>, |
| Up: <a rel="up" accesskey="u" href="Altering.html#Altering">Altering</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">17.6 Patching Programs</h3> |
| |
| <p><a name="index-patching-binaries-945"></a><a name="index-writing-into-executables-946"></a><a name="index-writing-into-corefiles-947"></a> |
| By default, <span class="sc">gdb</span> opens the file containing your program's |
| executable code (or the corefile) read-only. This prevents accidental |
| alterations to machine code; but it also prevents you from intentionally |
| patching your program's binary. |
| |
| <p>If you'd like to be able to patch the binary, you can specify that |
| explicitly with the <code>set write</code> command. For example, you might |
| want to turn on internal debugging flags, or even to make emergency |
| repairs. |
| |
| |
| <a name="index-set-write-948"></a> |
| <dl><dt><code>set write on</code><dt><code>set write off</code><dd>If you specify ‘<samp><span class="samp">set write on</span></samp>’, <span class="sc">gdb</span> opens executable and |
| core files for both reading and writing; if you specify <kbd>set write |
| off</kbd> (the default), <span class="sc">gdb</span> opens them read-only. |
| |
| <p>If you have already loaded a file, you must load it again (using the |
| <code>exec-file</code> or <code>core-file</code> command) after changing <code>set |
| write</code>, for your new setting to take effect. |
| |
| <br><dt><code>show write</code><dd><a name="index-show-write-949"></a>Display whether executable files and core files are opened for writing |
| as well as reading. |
| </dl> |
| |
| </body></html> |
| |
