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| <title>Debugging with GDB: Library List Format for SVR4 Targets</title> |
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| Next: <a href="Memory-Map-Format.html#Memory-Map-Format" accesskey="n" rel="next">Memory Map Format</a>, Previous: <a href="Library-List-Format.html#Library-List-Format" accesskey="p" rel="prev">Library List Format</a>, Up: <a href="Remote-Protocol.html#Remote-Protocol" accesskey="u" rel="up">Remote Protocol</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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| <a name="Library-List-Format-for-SVR4-Targets-1"></a> |
| <h3 class="section">E.15 Library List Format for SVR4 Targets</h3> |
| <a name="index-library-list-format_002c-remote-protocol-1"></a> |
| |
| <p>On SVR4 platforms <small>GDB</small> can use the symbol table of a dynamic loader |
| (e.g. <samp>ld.so</samp>) and normal memory operations to maintain a list of |
| shared libraries. Still a special library list provided by this packet is |
| more efficient for the <small>GDB</small> remote protocol. |
| </p> |
| <p>The ‘<samp>qXfer:libraries-svr4:read</samp>’ packet returns an XML document which lists |
| loaded libraries and their SVR4 linker parameters. For each library on SVR4 |
| target, the following parameters are reported: |
| </p> |
| <ul class="no-bullet"> |
| <li>- <code>name</code>, the absolute file name from the <code>l_name</code> field of |
| <code>struct link_map</code>. |
| </li><li>- <code>lm</code> with address of <code>struct link_map</code> used for TLS |
| (Thread Local Storage) access. |
| </li><li>- <code>l_addr</code>, the displacement as read from the field <code>l_addr</code> of |
| <code>struct link_map</code>. For prelinked libraries this is not an absolute |
| memory address. It is a displacement of absolute memory address against |
| address the file was prelinked to during the library load. |
| </li><li>- <code>l_ld</code>, which is memory address of the <code>PT_DYNAMIC</code> segment |
| </li></ul> |
| |
| <p>Additionally the single <code>main-lm</code> attribute specifies address of |
| <code>struct link_map</code> used for the main executable. This parameter is used |
| for TLS access and its presence is optional. |
| </p> |
| <p><small>GDB</small> must be linked with the Expat library to support XML |
| SVR4 library lists. See <a href="Requirements.html#Expat">Expat</a>. |
| </p> |
| <p>A simple memory map, with two loaded libraries (which do not use prelink), |
| looks like this: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"><library-list-svr4 version="1.0" main-lm="0xe4f8f8"> |
| <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000" |
| l_ld="0xe4eefc"/> |
| <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000" |
| l_ld="0x152350"/> |
| </library-list-svr> |
| </pre></div> |
| |
| <p>The format of an SVR4 library list is described by this DTD: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"><!-- library-list-svr4: Root element with versioning --> |
| <!ELEMENT library-list-svr4 (library)*> |
| <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0"> |
| <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED> |
| <!ELEMENT library EMPTY> |
| <!ATTLIST library name CDATA #REQUIRED> |
| <!ATTLIST library lm CDATA #REQUIRED> |
| <!ATTLIST library l_addr CDATA #REQUIRED> |
| <!ATTLIST library l_ld CDATA #REQUIRED> |
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