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<?xml version='1.0'?>
<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
]>
<section id="paracallgraph">
<title>Call Graph Tracing</title>
<indexterm>
<primary>script examples</primary>
<secondary>call graph tracing</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>call graph tracing</secondary>
</indexterm>
<indexterm>
<primary>call graph tracing</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>incoming/outgoing function calls, tracing</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>function calls (incoming/outgoing), tracing</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>tracing incoming/outgoing function calls</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>tracing call graph</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<remark>
WAR STORY: Call graph tracing http://sourceware.org/systemtap/wiki/WSCallGraph?highlight=((WarStories))
</remark>
<remark>
script: http://sourceware.org/systemtap/examples/general/para-callgraph.stp
</remark>
<para>This section describes how to trace incoming and outgoing function calls. </para>
<formalpara id="scriptcallgraph">
<title>para-callgraph.stp</title>
<para>
<programlisting><xi:include parse="text" href="../testsuite/systemtap.examples/general/para-callgraph.stp" xmlns:xi="http://www.w3.org/2001/XInclude" /></programlisting>
</para>
</formalpara>
<indexterm>
<primary>script examples</primary>
<secondary>multiple command-line arguments, example of</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>multiple command-line arguments, example of</secondary>
</indexterm>
<indexterm>
<primary>multiple command-line arguments, example of</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<indexterm>
<primary>example of multiple command-line arguments</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<para><xref linkend="scriptcallgraph"/> takes two command-line arguments:</para>
<indexterm>
<primary>script examples</primary>
<secondary>trigger function</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>trigger function</secondary>
</indexterm>
<indexterm>
<primary>trigger function</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<itemizedlist>
<listitem><para>
The function/s whose entry/exit call you'd like to trace
(<command>$1</command>).
</para></listitem>
<listitem><para>
A second optional <firstterm>trigger function</firstterm> (<command>$2</command>), which
enables or disables tracing on a per-thread basis. Tracing in each thread
will continue as long as the trigger function has not exited yet.
</para></listitem>
</itemizedlist>
<remark> please verify previous if correct; i'm particularly interested in finding out how to better describe "trigger function"</remark>
<indexterm>
<primary>script examples</primary>
<secondary>thread_indent(), sample usage</secondary>
</indexterm>
<indexterm>
<primary>examples of SystemTap scripts</primary>
<secondary>thread_indent(), sample usage</secondary>
</indexterm>
<indexterm>
<primary>thread_indent(), sample usage</primary>
<secondary>examples of SystemTap scripts</secondary>
</indexterm>
<para><xref linkend="scriptcallgraph"/> uses <command>thread_indent()</command>; as such, its output contains the timestamp, process name, and thread ID of <command>$1</command> (that is, the probe function you are tracing). For more information about <command>thread_indent()</command>, refer to its entry in <xref linkend="systemtapscript-functions"/>.</para>
<para>The following example contains an excerpt from the output
for <command>stap para-callgraph.stp 'kernel.function("*@fs/*.c")' 'kernel.function("sys_read")'</command>:</para>
<example id="paracallgraphoutput">
<title><xref linkend="scriptcallgraph"/> Sample Output</title>
<screen>[...]
267 gnome-terminal(2921): <-do_sync_read return=0xfffffffffffffff5
269 gnome-terminal(2921):<-vfs_read return=0xfffffffffffffff5
0 gnome-terminal(2921):->fput file=0xffff880111eebbc0
2 gnome-terminal(2921):<-fput
0 gnome-terminal(2921):->fget_light fd=0x3 fput_needed=0xffff88010544df54
3 gnome-terminal(2921):<-fget_light return=0xffff8801116ce980
0 gnome-terminal(2921):->vfs_read file=0xffff8801116ce980 buf=0xc86504 count=0x1000 pos=0xffff88010544df48
4 gnome-terminal(2921): ->rw_verify_area read_write=0x0 file=0xffff8801116ce980 ppos=0xffff88010544df48 count=0x1000
7 gnome-terminal(2921): <-rw_verify_area return=0x1000
12 gnome-terminal(2921): ->do_sync_read filp=0xffff8801116ce980 buf=0xc86504 len=0x1000 ppos=0xffff88010544df48
15 gnome-terminal(2921): <-do_sync_read return=0xfffffffffffffff5
18 gnome-terminal(2921):<-vfs_read return=0xfffffffffffffff5
0 gnome-terminal(2921):->fput file=0xffff8801116ce980</screen>
</example>
</section>
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