104 lines
5.1 KiB
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104 lines
5.1 KiB
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<title>Library List Format for SVR4 Targets - Debugging with GDB</title>
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<meta name="description" content="Debugging with GDB">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Remote-Protocol.html#Remote-Protocol" title="Remote Protocol">
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<link rel="prev" href="Library-List-Format.html#Library-List-Format" title="Library List Format">
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<link rel="next" href="Memory-Map-Format.html#Memory-Map-Format" title="Memory Map Format">
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under the terms of the GNU Free Documentation License, Version 1.3 or
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<div class="node">
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<a name="Library-List-Format-for-SVR4-Targets"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Memory-Map-Format.html#Memory-Map-Format">Memory Map Format</a>,
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Previous: <a rel="previous" accesskey="p" href="Library-List-Format.html#Library-List-Format">Library List Format</a>,
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Up: <a rel="up" accesskey="u" href="Remote-Protocol.html#Remote-Protocol">Remote Protocol</a>
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<hr>
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</div>
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<h3 class="section">E.15 Library List Format for SVR4 Targets</h3>
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<p><a name="index-library-list-format_002c-remote-protocol-3632"></a>
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On SVR4 platforms <span class="sc">gdb</span> can use the symbol table of a dynamic loader
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(e.g. <samp><span class="file">ld.so</span></samp>) and normal memory operations to maintain a list of
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shared libraries. Still a special library list provided by this packet is
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more efficient for the <span class="sc">gdb</span> remote protocol.
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<p>The ‘<samp><span class="samp">qXfer:libraries-svr4:read</span></samp>’ packet returns an XML document which lists
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loaded libraries and their SVR4 linker parameters. For each library on SVR4
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target, the following parameters are reported:
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<ul>
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<li><code>name</code>, the absolute file name from the <code>l_name</code> field of
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<code>struct link_map</code>.
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<li><code>lm</code> with address of <code>struct link_map</code> used for TLS
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(Thread Local Storage) access.
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<li><code>l_addr</code>, the displacement as read from the field <code>l_addr</code> of
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<code>struct link_map</code>. For prelinked libraries this is not an absolute
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memory address. It is a displacement of absolute memory address against
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address the file was prelinked to during the library load.
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<li><code>l_ld</code>, which is memory address of the <code>PT_DYNAMIC</code> segment
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</ul>
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<p>Additionally the single <code>main-lm</code> attribute specifies address of
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<code>struct link_map</code> used for the main executable. This parameter is used
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for TLS access and its presence is optional.
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<p><span class="sc">gdb</span> must be linked with the Expat library to support XML
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SVR4 library lists. See <a href="Expat.html#Expat">Expat</a>.
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<p>A simple memory map, with two loaded libraries (which do not use prelink),
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looks like this:
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<pre class="smallexample"> <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
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<library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
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l_ld="0xe4eefc"/>
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<library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
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l_ld="0x152350"/>
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</library-list-svr>
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</pre>
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<p>The format of an SVR4 library list is described by this DTD:
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<pre class="smallexample"> <!-- library-list-svr4: Root element with versioning -->
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<!ELEMENT library-list-svr4 (library)*>
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<!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
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<!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
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<!ELEMENT library EMPTY>
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<!ATTLIST library name CDATA #REQUIRED>
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<!ATTLIST library lm CDATA #REQUIRED>
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<!ATTLIST library l_addr CDATA #REQUIRED>
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<!ATTLIST library l_ld CDATA #REQUIRED>
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</pre>
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</body></html>
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