visus
/
toolchain-gcc-arm-embedded

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2020 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." -->
<!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Core File Generation (Debugging with GDB)</title>

<meta name="description" content="Core File Generation (Debugging with GDB)">
<meta name="keywords" content="Core File Generation (Debugging with GDB)">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<link href="index.html#Top" rel="start" title="Top">
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Data.html#Data" rel="up" title="Data">
<link href="Character-Sets.html#Character-Sets" rel="next" title="Character Sets">
<link href="Dump_002fRestore-Files.html#Dump_002fRestore-Files" rel="prev" title="Dump/Restore Files">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smalllisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en">
<a name="Core-File-Generation"></a>
<div class="header">
<p>
Next: <a href="Character-Sets.html#Character-Sets" accesskey="n" rel="next">Character Sets</a>, Previous: <a href="Dump_002fRestore-Files.html#Dump_002fRestore-Files" accesskey="p" rel="prev">Dump/Restore Files</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="How-to-Produce-a-Core-File-from-Your-Program"></a>
<h3 class="section">10.19 How to Produce a Core File from Your Program</h3>
<a name="index-dump-core-from-inferior"></a>

<p>A <em>core file</em> or <em>core dump</em> is a file that records the memory
image of a running process and its process status (register values
etc.).  Its primary use is post-mortem debugging of a program that
crashed while it ran outside a debugger.  A program that crashes
automatically produces a core file, unless this feature is disabled by
the user.  See <a href="Files.html#Files">Files</a>, for information on invoking <small>GDB</small> in
the post-mortem debugging mode.
</p>
<p>Occasionally, you may wish to produce a core file of the program you
are debugging in order to preserve a snapshot of its state.
<small>GDB</small> has a special command for that.
</p>
<dl compact="compact">
<dd><a name="index-gcore"></a>
<a name="index-generate_002dcore_002dfile"></a>
</dd>
<dt><code>generate-core-file [<var>file</var>]</code></dt>
<dt><code>gcore [<var>file</var>]</code></dt>
<dd><p>Produce a core dump of the inferior process.  The optional argument
<var>file</var> specifies the file name where to put the core dump.  If not
specified, the file name defaults to <samp>core.<var>pid</var></samp>, where
<var>pid</var> is the inferior process ID.
</p>
<p>Note that this command is implemented only for some systems (as of
this writing, <small>GNU</small>/Linux, FreeBSD, Solaris, and S390).
</p>
<p>On <small>GNU</small>/Linux, this command can take into account the value of the
file <samp>/proc/<var>pid</var>/coredump_filter</samp> when generating the core
dump (see <a href="#set-use_002dcoredump_002dfilter">set use-coredump-filter</a>), and by default honors the
<code>VM_DONTDUMP</code> flag for mappings where it is present in the file
<samp>/proc/<var>pid</var>/smaps</samp> (see <a href="#set-dump_002dexcluded_002dmappings">set dump-excluded-mappings</a>).
</p>
<a name="index-set-use_002dcoredump_002dfilter"></a>
<a name="set-use_002dcoredump_002dfilter"></a></dd>
<dt><code>set use-coredump-filter on</code></dt>
<dt><code>set use-coredump-filter off</code></dt>
<dd><p>Enable or disable the use of the file
<samp>/proc/<var>pid</var>/coredump_filter</samp> when generating core dump
files.  This file is used by the Linux kernel to decide what types of
memory mappings will be dumped or ignored when generating a core dump
file.  <var>pid</var> is the process ID of a currently running process.
</p>
<p>To make use of this feature, you have to write in the
<samp>/proc/<var>pid</var>/coredump_filter</samp> file a value, in hexadecimal,
which is a bit mask representing the memory mapping types.  If a bit
is set in the bit mask, then the memory mappings of the corresponding
types will be dumped; otherwise, they will be ignored.  This
configuration is inherited by child processes.  For more information
about the bits that can be set in the
<samp>/proc/<var>pid</var>/coredump_filter</samp> file, please refer to the
manpage of <code>core(5)</code>.
</p>
<p>By default, this option is <code>on</code>.  If this option is turned
<code>off</code>, <small>GDB</small> does not read the <samp>coredump_filter</samp> file
and instead uses the same default value as the Linux kernel in order
to decide which pages will be dumped in the core dump file.  This
value is currently <code>0x33</code>, which means that bits <code>0</code>
(anonymous private mappings), <code>1</code> (anonymous shared mappings),
<code>4</code> (ELF headers) and <code>5</code> (private huge pages) are active.
This will cause these memory mappings to be dumped automatically.
</p>
<a name="index-set-dump_002dexcluded_002dmappings"></a>
<a name="set-dump_002dexcluded_002dmappings"></a></dd>
<dt><code>set dump-excluded-mappings on</code></dt>
<dt><code>set dump-excluded-mappings off</code></dt>
<dd><p>If <code>on</code> is specified, <small>GDB</small> will dump memory mappings
marked with the <code>VM_DONTDUMP</code> flag.  This flag is represented in
the file <samp>/proc/<var>pid</var>/smaps</samp> with the acronym <code>dd</code>.
</p>
<p>The default value is <code>off</code>.
</p></dd>
</dl>

<hr>
<div class="header">
<p>
Next: <a href="Character-Sets.html#Character-Sets" accesskey="n" rel="next">Character Sets</a>, Previous: <a href="Dump_002fRestore-Files.html#Dump_002fRestore-Files" accesskey="p" rel="prev">Dump/Restore Files</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>


</body>
</html>