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  1. <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

  2. <html>

  3. <!-- Copyright (C) 1988-2020 Free Software Foundation, Inc.

  4. 

  5. Permission is granted to copy, distribute and/or modify this document

  6. under the terms of the GNU Free Documentation License, Version 1.3 or

  7. any later version published by the Free Software Foundation; with the

  8. Invariant Sections being "Free Software" and "Free Software Needs

  9. Free Documentation", with the Front-Cover Texts being "A GNU Manual,"

  10. and with the Back-Cover Texts as in (a) below.

  11. 

  12. (a) The FSF's Back-Cover Text is: "You are free to copy and modify

  13. this GNU Manual.  Buying copies from GNU Press supports the FSF in

  14. developing GNU and promoting software freedom." -->

  15. <!-- Created by GNU Texinfo 6.5, http://www.gnu.org/software/texinfo/ -->

  16. <head>

  17. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">

  18. <title>MiniDebugInfo (Debugging with GDB)</title>

  19. 

  20. <meta name="description" content="MiniDebugInfo (Debugging with GDB)">

  21. <meta name="keywords" content="MiniDebugInfo (Debugging with GDB)">

  22. <meta name="resource-type" content="document">

  23. <meta name="distribution" content="global">

  24. <meta name="Generator" content="makeinfo">

  25. <link href="index.html#Top" rel="start" title="Top">

  26. <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">

  27. <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">

  28. <link href="GDB-Files.html#GDB-Files" rel="up" title="GDB Files">

  29. <link href="Index-Files.html#Index-Files" rel="next" title="Index Files">

  30. <link href="Separate-Debug-Files.html#Separate-Debug-Files" rel="prev" title="Separate Debug Files">

  31. <style type="text/css">

  32. <!--

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  37. div.display {margin-left: 3.2em}

  38. div.example {margin-left: 3.2em}

  39. div.lisp {margin-left: 3.2em}

  40. div.smalldisplay {margin-left: 3.2em}

  41. div.smallexample {margin-left: 3.2em}

  42. div.smalllisp {margin-left: 3.2em}

  43. kbd {font-style: oblique}

  44. pre.display {font-family: inherit}

  45. pre.format {font-family: inherit}

  46. pre.menu-comment {font-family: serif}

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  55. ul.no-bullet {list-style: none}

  56. -->

  57. </style>

  58. 

  59. 

  60. </head>

  61. 

  62. <body lang="en">

  63. <a name="MiniDebugInfo"></a>

  64. <div class="header">

  65. <p>

  66. 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> &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>

  67. </div>

  68. <hr>

  69. <a name="Debugging-information-in-a-special-section"></a>

  70. <h3 class="section">18.4 Debugging information in a special section</h3>

  71. <a name="index-separate-debug-sections"></a>

  72. <a name="index-_002egnu_005fdebugdata-section"></a>

  73. 

  74. <p>Some systems ship pre-built executables and libraries that have a

  75. special &lsquo;<samp>.gnu_debugdata</samp>&rsquo; section.  This feature is called

  76. <em>MiniDebugInfo</em>.  This section holds an LZMA-compressed object and

  77. is used to supply extra symbols for backtraces.

  78. </p>

  79. <p>The intent of this section is to provide extra minimal debugging

  80. information for use in simple backtraces.  It is not intended to be a

  81. 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,

  82. <small>GDB</small> does not currently put restrictions on what sort of

  83. debugging information might be included in the section.

  84. </p>

  85. <p><small>GDB</small> has support for this extension.  If the section exists,

  86. then it is used provided that no other source of debugging information

  87. can be found, and that <small>GDB</small> was configured with LZMA support.

  88. </p>

  89. <p>This section can be easily created using <code>objcopy</code> and other

  90. standard utilities:

  91. </p>

  92. <div class="smallexample">

  93. <pre class="smallexample"># Extract the dynamic symbols from the main binary, there is no need

  94. # to also have these in the normal symbol table.

  95. nm -D <var>binary</var> --format=posix --defined-only \

  96.   | awk '{ print $1 }' | sort &gt; dynsyms

  97. 

  98. # Extract all the text (i.e. function) symbols from the debuginfo.

  99. # (Note that we actually also accept &quot;D&quot; symbols, for the benefit

  100. # of platforms like PowerPC64 that use function descriptors.)

  101. nm <var>binary</var> --format=posix --defined-only \

  102.   | awk '{ if ($2 == &quot;T&quot; || $2 == &quot;t&quot; || $2 == &quot;D&quot;) print $1 }' \

  103.   | sort &gt; funcsyms

  104. 

  105. # Keep all the function symbols not already in the dynamic symbol

  106. # table.

  107. comm -13 dynsyms funcsyms &gt; keep_symbols

  108. 

  109. # Separate full debug info into debug binary.

  110. objcopy --only-keep-debug <var>binary</var> debug

  111. 

  112. # Copy the full debuginfo, keeping only a minimal set of symbols and

  113. # removing some unnecessary sections.

  114. objcopy -S --remove-section .gdb_index --remove-section .comment \

  115.   --keep-symbols=keep_symbols debug mini_debuginfo

  116. 

  117. # Drop the full debug info from the original binary.

  118. strip --strip-all -R .comment <var>binary</var>

  119. 

  120. # Inject the compressed data into the .gnu_debugdata section of the

  121. # original binary.

  122. xz mini_debuginfo

  123. objcopy --add-section .gnu_debugdata=mini_debuginfo.xz <var>binary</var>

  124. </pre></div>

  125. 

  126. <hr>

  127. <div class="header">

  128. <p>

  129. 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> &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>

  130. </div>

  131. 

  132. 

  133. 

  134. </body>

  135. </html>