| <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
| <html> |
| <!-- Copyright (C) 1988-2015 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being "Free Software" and "Free Software Needs |
| Free Documentation", with the Front-Cover Texts being "A GNU Manual," |
| and with the Back-Cover Texts as in (a) below. |
| |
| (a) The FSF's Back-Cover Text is: "You are free to copy and modify |
| this GNU Manual. Buying copies from GNU Press supports the FSF in |
| developing GNU and promoting software freedom." --> |
| <!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ --> |
| <head> |
| <title>Debugging with GDB: Static Probe Points</title> |
| |
| <meta name="description" content="Debugging with GDB: Static Probe Points"> |
| <meta name="keywords" content="Debugging with GDB: Static Probe Points"> |
| <meta name="resource-type" content="document"> |
| <meta name="distribution" content="global"> |
| <meta name="Generator" content="makeinfo"> |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> |
| <link href="index.html#Top" rel="start" title="Top"> |
| <link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> |
| <link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> |
| <link href="Breakpoints.html#Breakpoints" rel="up" title="Breakpoints"> |
| <link href="Error-in-Breakpoints.html#Error-in-Breakpoints" rel="next" title="Error in Breakpoints"> |
| <link href="Save-Breakpoints.html#Save-Breakpoints" rel="prev" title="Save Breakpoints"> |
| <style type="text/css"> |
| <!-- |
| a.summary-letter {text-decoration: none} |
| blockquote.smallquotation {font-size: smaller} |
| div.display {margin-left: 3.2em} |
| div.example {margin-left: 3.2em} |
| div.indentedblock {margin-left: 3.2em} |
| div.lisp {margin-left: 3.2em} |
| div.smalldisplay {margin-left: 3.2em} |
| div.smallexample {margin-left: 3.2em} |
| div.smallindentedblock {margin-left: 3.2em; font-size: smaller} |
| div.smalllisp {margin-left: 3.2em} |
| kbd {font-style:oblique} |
| pre.display {font-family: inherit} |
| pre.format {font-family: inherit} |
| pre.menu-comment {font-family: serif} |
| pre.menu-preformatted {font-family: serif} |
| pre.smalldisplay {font-family: inherit; font-size: smaller} |
| pre.smallexample {font-size: smaller} |
| pre.smallformat {font-family: inherit; font-size: smaller} |
| pre.smalllisp {font-size: smaller} |
| span.nocodebreak {white-space:nowrap} |
| span.nolinebreak {white-space:nowrap} |
| span.roman {font-family:serif; font-weight:normal} |
| span.sansserif {font-family:sans-serif; font-weight:normal} |
| ul.no-bullet {list-style: none} |
| --> |
| </style> |
| |
| |
| </head> |
| |
| <body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> |
| <a name="Static-Probe-Points"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="Error-in-Breakpoints.html#Error-in-Breakpoints" accesskey="n" rel="next">Error in Breakpoints</a>, Previous: <a href="Save-Breakpoints.html#Save-Breakpoints" accesskey="p" rel="prev">Save Breakpoints</a>, Up: <a href="Breakpoints.html#Breakpoints" accesskey="u" rel="up">Breakpoints</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> |
| </div> |
| <hr> |
| <a name="Static-Probe-Points-1"></a> |
| <h4 class="subsection">5.1.10 Static Probe Points</h4> |
| |
| <a name="index-static-probe-point_002c-SystemTap"></a> |
| <a name="index-static-probe-point_002c-DTrace"></a> |
| <p><small>GDB</small> supports <em>SDT</em> probes in the code. <acronym>SDT</acronym> stands |
| for Statically Defined Tracing, and the probes are designed to have a tiny |
| runtime code and data footprint, and no dynamic relocations. |
| </p> |
| <p>Currently, the following types of probes are supported on |
| ELF-compatible systems: |
| </p> |
| <ul> |
| <li> <code>SystemTap</code> (<a href="http://sourceware.org/systemtap/">http://sourceware.org/systemtap/</a>) |
| <acronym>SDT</acronym> probes<a name="DOCF4" href="#FOOT4"><sup>4</sup></a>. <code>SystemTap</code> probes are usable |
| from assembly, C and C<tt>++</tt> languages<a name="DOCF5" href="#FOOT5"><sup>5</sup></a>. |
| |
| </li><li> <code>DTrace</code> (<a href="http://oss.oracle.com/projects/DTrace">http://oss.oracle.com/projects/DTrace</a>) |
| <acronym>USDT</acronym> probes. <code>DTrace</code> probes are usable from C and |
| C<tt>++</tt> languages. |
| </li></ul> |
| |
| <a name="index-semaphores-on-static-probe-points"></a> |
| <p>Some <code>SystemTap</code> probes have an associated semaphore variable; |
| for instance, this happens automatically if you defined your probe |
| using a DTrace-style <samp>.d</samp> file. If your probe has a semaphore, |
| <small>GDB</small> will automatically enable it when you specify a |
| breakpoint using the ‘<samp>-probe-stap</samp>’ notation. But, if you put a |
| breakpoint at a probe’s location by some other method (e.g., |
| <code>break file:line</code>), then <small>GDB</small> will not automatically set |
| the semaphore. <code>DTrace</code> probes do not support semaphores. |
| </p> |
| <p>You can examine the available static static probes using <code>info |
| probes</code>, with optional arguments: |
| </p> |
| <dl compact="compact"> |
| <dd><a name="index-info-probes"></a> |
| </dd> |
| <dt><code>info probes <span class="roman">[</span><var>type</var><span class="roman">]</span> <span class="roman">[</span><var>provider</var> <span class="roman">[</span><var>name</var> <span class="roman">[</span><var>objfile</var><span class="roman">]</span><span class="roman">]</span><span class="roman">]</span></code></dt> |
| <dd><p>If given, <var>type</var> is either <code>stap</code> for listing |
| <code>SystemTap</code> probes or <code>dtrace</code> for listing <code>DTrace</code> |
| probes. If omitted all probes are listed regardless of their types. |
| </p> |
| <p>If given, <var>provider</var> is a regular expression used to match against provider |
| names when selecting which probes to list. If omitted, probes by all |
| probes from all providers are listed. |
| </p> |
| <p>If given, <var>name</var> is a regular expression to match against probe names |
| when selecting which probes to list. If omitted, probe names are not |
| considered when deciding whether to display them. |
| </p> |
| <p>If given, <var>objfile</var> is a regular expression used to select which |
| object files (executable or shared libraries) to examine. If not |
| given, all object files are considered. |
| </p> |
| </dd> |
| <dt><code>info probes all</code></dt> |
| <dd><p>List the available static probes, from all types. |
| </p></dd> |
| </dl> |
| |
| <a name="index-enabling-and-disabling-probes"></a> |
| <p>Some probe points can be enabled and/or disabled. The effect of |
| enabling or disabling a probe depends on the type of probe being |
| handled. Some <code>DTrace</code> probes can be enabled or |
| disabled, but <code>SystemTap</code> probes cannot be disabled. |
| </p> |
| <p>You can enable (or disable) one or more probes using the following |
| commands, with optional arguments: |
| </p> |
| <dl compact="compact"> |
| <dd><a name="index-enable-probes"></a> |
| </dd> |
| <dt><code>enable probes <span class="roman">[</span><var>provider</var> <span class="roman">[</span><var>name</var> <span class="roman">[</span><var>objfile</var><span class="roman">]</span><span class="roman">]</span><span class="roman">]</span></code></dt> |
| <dd><p>If given, <var>provider</var> is a regular expression used to match against |
| provider names when selecting which probes to enable. If omitted, |
| all probes from all providers are enabled. |
| </p> |
| <p>If given, <var>name</var> is a regular expression to match against probe |
| names when selecting which probes to enable. If omitted, probe names |
| are not considered when deciding whether to enable them. |
| </p> |
| <p>If given, <var>objfile</var> is a regular expression used to select which |
| object files (executable or shared libraries) to examine. If not |
| given, all object files are considered. |
| </p> |
| <a name="index-disable-probes"></a> |
| </dd> |
| <dt><code>disable probes <span class="roman">[</span><var>provider</var> <span class="roman">[</span><var>name</var> <span class="roman">[</span><var>objfile</var><span class="roman">]</span><span class="roman">]</span><span class="roman">]</span></code></dt> |
| <dd><p>See the <code>enable probes</code> command above for a description of the |
| optional arguments accepted by this command. |
| </p></dd> |
| </dl> |
| |
| <a name="index-_0024_005fprobe_005farg_002c-convenience-variable"></a> |
| <p>A probe may specify up to twelve arguments. These are available at the |
| point at which the probe is defined—that is, when the current PC is |
| at the probe’s location. The arguments are available using the |
| convenience variables (see <a href="Convenience-Vars.html#Convenience-Vars">Convenience Vars</a>) |
| <code>$_probe_arg0</code>…<code>$_probe_arg11</code>. In <code>SystemTap</code> |
| probes each probe argument is an integer of the appropriate size; |
| types are not preserved. In <code>DTrace</code> probes types are preserved |
| provided that they are recognized as such by <small>GDB</small>; otherwise |
| the value of the probe argument will be a long integer. The |
| convenience variable <code>$_probe_argc</code> holds the number of arguments |
| at the current probe point. |
| </p> |
| <p>These variables are always available, but attempts to access them at |
| any location other than a probe point will cause <small>GDB</small> to give |
| an error message. |
| </p> |
| |
| <div class="footnote"> |
| <hr> |
| <h4 class="footnotes-heading">Footnotes</h4> |
| |
| <h3><a name="FOOT4" href="#DOCF4">(4)</a></h3> |
| <p>See |
| <a href="http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps">http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps</a> |
| for more information on how to add <code>SystemTap</code> <acronym>SDT</acronym> |
| probes in your applications.</p> |
| <h3><a name="FOOT5" href="#DOCF5">(5)</a></h3> |
| <p>See |
| <a href="http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation">http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation</a> |
| for a good reference on how the <acronym>SDT</acronym> probes are implemented.</p> |
| </div> |
| <hr> |
| <div class="header"> |
| <p> |
| Next: <a href="Error-in-Breakpoints.html#Error-in-Breakpoints" accesskey="n" rel="next">Error in Breakpoints</a>, Previous: <a href="Save-Breakpoints.html#Save-Breakpoints" accesskey="p" rel="prev">Save Breakpoints</a>, Up: <a href="Breakpoints.html#Breakpoints" accesskey="u" rel="up">Breakpoints</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> |
| </div> |
| |
| |
| |
| </body> |
| </html> |