<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
<TITLE>KernelAnalysis-HOWTO: Syntax used</TITLE>
<LINK HREF="KernelAnalysis-HOWTO-3.html" REL=next>
<LINK HREF="KernelAnalysis-HOWTO-1.html" REL=previous>
<LINK HREF="KernelAnalysis-HOWTO.html#toc2" REL=contents>
</HEAD>
<BODY>
<A HREF="KernelAnalysis-HOWTO-3.html">Next</A>
<A HREF="KernelAnalysis-HOWTO-1.html">Previous</A>
<A HREF="KernelAnalysis-HOWTO.html#toc2">Contents</A>
<HR>
<H2><A NAME="s2">2. Syntax used</A></H2>
<H2><A NAME="ss2.1">2.1 Function Syntax</A>
</H2>
<P>When speaking about a function, we write:
<P>
<P>
<PRE>
"function_name [ file location . extension ]"
</PRE>
<P>For example:
<P>
<P>
<PRE>
"schedule [kernel/sched.c]"
</PRE>
<P>tells us that we talk about
<P>
<P>"schedule"
<P>
<P>function retrievable from file
<P>
<P>[ kernel/sched.c ]
<P>
<P>Note: We also assume /usr/src/linux as the starting directory.
<P>
<H2><A NAME="ss2.2">2.2 Indentation</A>
</H2>
<P>Indentation in source code is 3 blank characters.
<P>
<H2><A NAME="ss2.3">2.3 InterCallings Analysis</A>
</H2>
<H3>Overview</H3>
<P>We use the"InterCallings Analysis "(ICA) to see (in an indented
fashion) how kernel functions call each other.
<P>
<P>For example, the sleep_on command is described in ICA below:
<P>
<P>
<PRE>
|sleep_on
|init_waitqueue_entry --
|__add_wait_queue | enqueuing request
|list_add |
|__list_add --
|schedule --- waiting for request to be executed
|__remove_wait_queue --
|list_del | dequeuing request
|__list_del --
sleep_on ICA
</PRE>
<P>The indented ICA is followed by functions' locations:
<P>
<P>
<UL>
<LI>sleep_on [kernel/sched.c]</LI>
<LI>init_waitqueue_entry [include/linux/wait.h]</LI>
<LI>__add_wait_queue</LI>
<LI>list_add [include/linux/list.h]</LI>
<LI>__list_add</LI>
<LI>schedule [kernel/sched.c]</LI>
<LI>__remove_wait_queue [include/linux/wait.h]</LI>
<LI>list_del [include/linux/list.h]</LI>
<LI>__list_del
</LI>
</UL>
<P>Note: We don't specify anymore file location, if specified just
before.
<P>
<H3>Details</H3>
<P>In an ICA a line like looks like the following
<P>
<P>
<PRE>
function1 -> function2
</PRE>
<P>means that < function1 > is a generic pointer to another
function. In this case < function1 > points to < function2
>.
<P>
<P>When we write:
<P>
<P>
<PRE>
function:
</PRE>
<P>it means that < function > is not a real function. It is
a label (typically assembler label).
<P>
<P>In many sections we may report a ''C'' code or a ''pseudo-code''.
In real source files, you could use ''assembler'' or ''not structured''
code. This difference is for learning purposes.
<P>
<H3>PROs of using ICA</H3>
<P>The advantages of using ICA (InterCallings Analysis) are many:
<P>
<P>
<UL>
<LI>You get an overview of what happens when you call a kernel function
</LI>
<LI>Function locations are indicated after the function, so ICA could
also be considered as a little ''function reference''</LI>
<LI>InterCallings Analysis (ICA) is useful in sleep/awake mechanisms,
where we can view what we do before sleeping, the proper sleeping
action, and what we'll do after waking up (after schedule).
</LI>
</UL>
<H3>CONTROs of using ICA</H3>
<P>
<UL>
<LI>Some of the disadvantages of using ICA are listed below:
</LI>
</UL>
<P>As all theoretical models, we simplify reality avoiding many
details, such as real source code and special conditions.
<P>
<P>
<UL>
<LI>Additional diagrams should be added to better represent stack
conditions, data values, and so on.
</LI>
</UL>
<HR>
<A HREF="KernelAnalysis-HOWTO-3.html">Next</A>
<A HREF="KernelAnalysis-HOWTO-1.html">Previous</A>
<A HREF="KernelAnalysis-HOWTO.html#toc2">Contents</A>
</BODY>
</HTML>
