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2. Syntax used

2.1 Function Syntax

When speaking about a function, we write:

"function_name  [ file location . extension ]"

For example:

"schedule [kernel/sched.c]" 

tells us that we talk about

"schedule"

function retrievable from file

[ kernel/sched.c ]

Note: We also assume /usr/src/linux as the starting directory.

2.2 Indentation

Indentation in source code is 3 blank characters.

2.3 InterCallings Analysis

Overview

We use the"InterCallings Analysis "(ICA) to see (in an indented fashion) how kernel functions call each other.

For example, the sleep_on command is described in ICA below:

|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

The indented ICA is followed by functions' locations:

Note: We don't specify anymore file location, if specified just before.

Details

In an ICA a line like looks like the following

 function1 -> function2

means that < function1 > is a generic pointer to another function. In this case < function1 > points to < function2 >.

When we write:

  function:

it means that < function > is not a real function. It is a label (typically assembler label).

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.

PROs of using ICA

The advantages of using ICA (InterCallings Analysis) are many:

CONTROs of using ICA

As all theoretical models, we simplify reality avoiding many details, such as real source code and special conditions.


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