116 lines
5.6 KiB
HTML
116 lines
5.6 KiB
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<title>Library List Format - Debugging with GDB</title>
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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="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension" title="File-I/O Remote Protocol Extension">
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<link rel="next" href="Library-List-Format-for-SVR4-Targets.html#Library-List-Format-for-SVR4-Targets" title="Library List Format for SVR4 Targets">
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<body>
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<div class="node">
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<a name="Library-List-Format"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Library-List-Format-for-SVR4-Targets.html#Library-List-Format-for-SVR4-Targets">Library List Format for SVR4 Targets</a>,
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Previous: <a rel="previous" accesskey="p" href="File_002dI_002fO-Remote-Protocol-Extension.html#File_002dI_002fO-Remote-Protocol-Extension">File-I/O Remote Protocol Extension</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.14 Library List Format</h3>
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<p><a name="index-library-list-format_002c-remote-protocol-3631"></a>
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On some platforms, a dynamic loader (e.g. <samp><span class="file">ld.so</span></samp>) runs in the
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same process as your application to manage libraries. In this case,
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<span class="sc">gdb</span> can use the loader's symbol table and normal memory
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operations to maintain a list of shared libraries. On other
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platforms, the operating system manages loaded libraries.
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<span class="sc">gdb</span> can not retrieve the list of currently loaded libraries
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through memory operations, so it uses the ‘<samp><span class="samp">qXfer:libraries:read</span></samp>’
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packet (see <a href="qXfer-library-list-read.html#qXfer-library-list-read">qXfer library list read</a>) instead. The remote stub
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queries the target's operating system and reports which libraries
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are loaded.
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<p>The ‘<samp><span class="samp">qXfer:libraries:read</span></samp>’ packet returns an XML document which
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lists loaded libraries and their offsets. Each library has an
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associated name and one or more segment or section base addresses,
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which report where the library was loaded in memory.
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<p>For the common case of libraries that are fully linked binaries, the
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library should have a list of segments. If the target supports
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dynamic linking of a relocatable object file, its library XML element
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should instead include a list of allocated sections. The segment or
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section bases are start addresses, not relocation offsets; they do not
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depend on the library's link-time base addresses.
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<p><span class="sc">gdb</span> must be linked with the Expat library to support XML
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library lists. See <a href="Expat.html#Expat">Expat</a>.
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<p>A simple memory map, with one loaded library relocated by a single
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offset, looks like this:
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<pre class="smallexample"> <library-list>
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<library name="/lib/libc.so.6">
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<segment address="0x10000000"/>
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</library>
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</library-list>
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</pre>
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<p>Another simple memory map, with one loaded library with three
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allocated sections (.text, .data, .bss), looks like this:
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<pre class="smallexample"> <library-list>
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<library name="sharedlib.o">
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<section address="0x10000000"/>
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<section address="0x20000000"/>
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<section address="0x30000000"/>
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</library>
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</library-list>
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</pre>
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<p>The format of a library list is described by this DTD:
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<pre class="smallexample"> <!-- library-list: Root element with versioning -->
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<!ELEMENT library-list (library)*>
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<!ATTLIST library-list version CDATA #FIXED "1.0">
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<!ELEMENT library (segment*, section*)>
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<!ATTLIST library name CDATA #REQUIRED>
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<!ELEMENT segment EMPTY>
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<!ATTLIST segment address CDATA #REQUIRED>
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<!ELEMENT section EMPTY>
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<!ATTLIST section address CDATA #REQUIRED>
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</pre>
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<p>In addition, segments and section descriptors cannot be mixed within a
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single library element, and you must supply at least one segment or
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section for each library.
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</body></html>
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