Codeviz installation

When trying to understand what code does, it is often useful to create a graphical representation that shows how functions call each other. This kind of representation is often called a call graph.

Codeviz is a tool that helps create call graphs.

I downloaded codeviz from this website: http://www.csn.ul.ie/~mel/projects/codeviz/

Here is an example of a call graph for a function in gPXE:

The function name is in the rectangular box on the left, and all the functions that are called flow to the right. I have limited the display to 3 levels of depth for presentation purposes.

# Make sure we have graphviz and ncftp
$ rpm -q graphviz ncftp
# Fetch if needed
$ sudo yum install graphviz ncftp
$ wget http://www.csn.ul.ie/~mel/projects/codeviz/codeviz-1.0.11.tar.gz
$ tar -xf codeviz-1.0.11.tar.gz 
$ cd codeviz-1.0.11
$ ./configure
$ make
$ sudo make install

The make command above downloads and builds gcc-3.4.6 from ftp.gnu.org.

It also installs genfull and gengraph in /usr/local/bin.

To configure for gPXE you need to edit this line in src/Makefile.housekeeping:

PRECIOUS : $(BIN)/%.tmp

to be:

PRECIOUS : $(BIN)/%.tmp $(BIN)/%.cdepn

This causes .cdepn (C dependency) files to be kept.

First we get gccgraph to compile all the C files in gPXE. This is not too hard:

$ cd gpxe.git/src
$ make veryclean
$ make CC=/usr/local/gccgraph/bin/gcc blib

This will generate a .cdepn file for each .c file compiled. To see where they are do:

$ find . -name "*.cdepn"

Next we build the dependency database:

$ genfull

This creates the file full.graph in the current directory.

To make a nice call graph of rtl8169_poll for instance, we can do:

$ gengraph -f rtl8169_poll -d 3 output-font=Arial --output-layout LR --plain

This does a call graph of the function rtl8169_poll, depth 3, left-to-right orientation, and requests that output be saved for input to the dot program.

dot is the program that renders the outupt from gengraph:

$ dot -GPAPERSIZE=letter -Gsize=8,10.5 -Gcenter=1 -Gmargin=.25 -Tps -o rtl8169_poll.ps < rtl8169_poll.plain 

dot draws the call graph according to the instructions in the .plain file, and outputs a file in whatever -T says (postscript in this case. png is also popular).

We can also request a .pdf be created from the .ps file using ps2pdf:

$ ps2pdf rtl8169_poll.ps

The three commands can be wrapped in a shell script command called mkcg such as:

#!/bin/sh
gengraph -f ${1} -d 3 output-font=Arial --output-layout LR --plain
dot -GPAPERSIZE=letter -Gsize=8,10.5 -Gcenter=1 -Gmargin=.25 -Tps -o ${1}.ps < ${1}.plain
ps2pdf ${1}.ps
rm ${1}.{ps,plain}

This makes the process of creating the .pdf a single command:

$ mkcg rtl8169_poll

Ghostscript can combine separate PDF pages into a single file:

$ gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=gpxe-call-graphs.pdf gpxe-api-call-graphs/*.pdf