140 lines
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140 lines
6.7 KiB
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<title>dotdebug_gdb_scripts section - Debugging with GDB</title>
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<div class="node">
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<a name="dotdebug_gdb_scripts-section"></a>
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<a name="dotdebug_005fgdb_005fscripts-section"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Which-flavor-to-choose_003f.html#Which-flavor-to-choose_003f">Which flavor to choose?</a>,
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Previous: <a rel="previous" accesskey="p" href="objfile_002dgdbdotext-file.html#objfile_002dgdbdotext-file">objfile-gdbdotext file</a>,
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Up: <a rel="up" accesskey="u" href="Auto_002dloading-extensions.html#Auto_002dloading-extensions">Auto-loading extensions</a>
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<hr>
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</div>
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<h4 class="subsection">23.4.2 The <code>.debug_gdb_scripts</code> section</h4>
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<p><a name="index-g_t_0040code_007b_002edebug_005fgdb_005fscripts_007d-section-2889"></a>
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For systems using file formats like ELF and COFF,
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when <span class="sc">gdb</span> loads a new object file
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it will look for a special section named <code>.debug_gdb_scripts</code>.
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If this section exists, its contents is a list of null-terminated entries
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specifying scripts to load. Each entry begins with a non-null prefix byte that
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specifies the kind of entry, typically the extension language and whether the
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script is in a file or inlined in <code>.debug_gdb_scripts</code>.
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<p>The following entries are supported:
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<dl>
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<dt><code>SECTION_SCRIPT_ID_PYTHON_FILE = 1</code><br><dt><code>SECTION_SCRIPT_ID_SCHEME_FILE = 3</code><br><dt><code>SECTION_SCRIPT_ID_PYTHON_TEXT = 4</code><br><dt><code>SECTION_SCRIPT_ID_SCHEME_TEXT = 6</code><dd></dl>
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<h5 class="subsubsection">23.4.2.1 Script File Entries</h5>
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<p>If the entry specifies a file, <span class="sc">gdb</span> will look for the file first
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in the current directory and then along the source search path
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(see <a href="Source-Path.html#Source-Path">Specifying Source Directories</a>),
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except that <samp><span class="file">$cdir</span></samp> is not searched, since the compilation
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directory is not relevant to scripts.
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<p>File entries can be placed in section <code>.debug_gdb_scripts</code> with,
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for example, this GCC macro for Python scripts.
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<pre class="example"> /* Note: The "MS" section flags are to remove duplicates. */
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#define DEFINE_GDB_PY_SCRIPT(script_name) \
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asm("\
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.pushsection \".debug_gdb_scripts\", \"MS\",@progbits,1\n\
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.byte 1 /* Python */\n\
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.asciz \"" script_name "\"\n\
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.popsection \n\
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");
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</pre>
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<p class="noindent">For Guile scripts, replace <code>.byte 1</code> with <code>.byte 3</code>.
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Then one can reference the macro in a header or source file like this:
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<pre class="example"> DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
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</pre>
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<p>The script name may include directories if desired.
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<p>Note that loading of this script file also requires accordingly configured
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<code>auto-load safe-path</code> (see <a href="Auto_002dloading-safe-path.html#Auto_002dloading-safe-path">Auto-loading safe path</a>).
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<p>If the macro invocation is put in a header, any application or library
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using this header will get a reference to the specified script,
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and with the use of <code>"MS"</code> attributes on the section, the linker
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will remove duplicates.
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<h5 class="subsubsection">23.4.2.2 Script Text Entries</h5>
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<p>Script text entries allow to put the executable script in the entry
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itself instead of loading it from a file.
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The first line of the entry, everything after the prefix byte and up to
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the first newline (<code>0xa</code>) character, is the script name, and must not
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contain any kind of space character, e.g., spaces or tabs.
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The rest of the entry, up to the trailing null byte, is the script to
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execute in the specified language. The name needs to be unique among
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all script names, as <span class="sc">gdb</span> executes each script only once based
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on its name.
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<p>Here is an example from file <samp><span class="file">py-section-script.c</span></samp> in the <span class="sc">gdb</span>
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testsuite.
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<pre class="example"> #include "symcat.h"
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#include "gdb/section-scripts.h"
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asm(
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".pushsection \".debug_gdb_scripts\", \"MS\",@progbits,1\n"
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".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
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".ascii \"gdb.inlined-script\\n\"\n"
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".ascii \"class test_cmd (gdb.Command):\\n\"\n"
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".ascii \" def __init__ (self):\\n\"\n"
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".ascii \" super (test_cmd, self).__init__ ("
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"\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
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".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
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".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
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".ascii \"test_cmd ()\\n\"\n"
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".byte 0\n"
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".popsection\n"
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);
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</pre>
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<p>Loading of inlined scripts requires a properly configured
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<code>auto-load safe-path</code> (see <a href="Auto_002dloading-safe-path.html#Auto_002dloading-safe-path">Auto-loading safe path</a>).
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The path to specify in <code>auto-load safe-path</code> is the path of the file
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containing the <code>.debug_gdb_scripts</code> section.
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</body></html>
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