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136 lines
6.3 KiB
HTML
136 lines
6.3 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2019 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Free Software" and "Free Software Needs
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Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
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and with the Back-Cover Texts as in (a) below.
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(a) The FSF's Back-Cover Text is: "You are free to copy and modify
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this GNU Manual. Buying copies from GNU Press supports the FSF in
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developing GNU and promoting software freedom." -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>MiniDebugInfo (Debugging with GDB)</title>
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<meta name="description" content="MiniDebugInfo (Debugging with GDB)">
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<meta name="keywords" content="MiniDebugInfo (Debugging with GDB)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="GDB-Files.html#GDB-Files" rel="up" title="GDB Files">
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<link href="Index-Files.html#Index-Files" rel="next" title="Index Files">
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<link href="Separate-Debug-Files.html#Separate-Debug-Files" rel="prev" title="Separate Debug Files">
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<style type="text/css">
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<!--
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a.summary-letter {text-decoration: none}
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blockquote.indentedblock {margin-right: 0em}
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blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
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blockquote.smallquotation {font-size: smaller}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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div.smalldisplay {margin-left: 3.2em}
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div.smallexample {margin-left: 3.2em}
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div.smalllisp {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallexample {font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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span.sansserif {font-family: sans-serif; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="MiniDebugInfo"></a>
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<div class="header">
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<p>
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Next: <a href="Index-Files.html#Index-Files" accesskey="n" rel="next">Index Files</a>, Previous: <a href="Separate-Debug-Files.html#Separate-Debug-Files" accesskey="p" rel="prev">Separate Debug Files</a>, Up: <a href="GDB-Files.html#GDB-Files" accesskey="u" rel="up">GDB Files</a> [<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>
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</div>
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<hr>
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<a name="Debugging-information-in-a-special-section"></a>
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<h3 class="section">18.4 Debugging information in a special section</h3>
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<a name="index-separate-debug-sections"></a>
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<a name="index-_002egnu_005fdebugdata-section"></a>
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<p>Some systems ship pre-built executables and libraries that have a
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special ‘<samp>.gnu_debugdata</samp>’ section. This feature is called
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<em>MiniDebugInfo</em>. This section holds an LZMA-compressed object and
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is used to supply extra symbols for backtraces.
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</p>
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<p>The intent of this section is to provide extra minimal debugging
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information for use in simple backtraces. It is not intended to be a
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replacement for full separate debugging information (see <a href="Separate-Debug-Files.html#Separate-Debug-Files">Separate Debug Files</a>). The example below shows the intended use; however,
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<small>GDB</small> does not currently put restrictions on what sort of
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debugging information might be included in the section.
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</p>
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<p><small>GDB</small> has support for this extension. If the section exists,
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then it is used provided that no other source of debugging information
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can be found, and that <small>GDB</small> was configured with LZMA support.
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</p>
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<p>This section can be easily created using <code>objcopy</code> and other
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standard utilities:
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</p>
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<div class="smallexample">
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<pre class="smallexample"># Extract the dynamic symbols from the main binary, there is no need
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# to also have these in the normal symbol table.
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nm -D <var>binary</var> --format=posix --defined-only \
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| awk '{ print $1 }' | sort > dynsyms
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# Extract all the text (i.e. function) symbols from the debuginfo.
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# (Note that we actually also accept "D" symbols, for the benefit
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# of platforms like PowerPC64 that use function descriptors.)
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nm <var>binary</var> --format=posix --defined-only \
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| awk '{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 }' \
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| sort > funcsyms
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# Keep all the function symbols not already in the dynamic symbol
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# table.
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comm -13 dynsyms funcsyms > keep_symbols
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# Separate full debug info into debug binary.
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objcopy --only-keep-debug <var>binary</var> debug
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# Copy the full debuginfo, keeping only a minimal set of symbols and
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# removing some unnecessary sections.
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objcopy -S --remove-section .gdb_index --remove-section .comment \
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--keep-symbols=keep_symbols debug mini_debuginfo
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# Drop the full debug info from the original binary.
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strip --strip-all -R .comment <var>binary</var>
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# Inject the compressed data into the .gnu_debugdata section of the
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# original binary.
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xz mini_debuginfo
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objcopy --add-section .gnu_debugdata=mini_debuginfo.xz <var>binary</var>
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</pre></div>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Index-Files.html#Index-Files" accesskey="n" rel="next">Index Files</a>, Previous: <a href="Separate-Debug-Files.html#Separate-Debug-Files" accesskey="p" rel="prev">Separate Debug Files</a>, Up: <a href="GDB-Files.html#GDB-Files" accesskey="u" rel="up">GDB Files</a> [<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>
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</div>
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</body>
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</html>
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