lcov : http://ltp.sourceforge.net/coverage/lcov.php
LCOV is an extension of GCOV, […] a set of PERL scripts which build on the textual GCOV output :
* HTML based output: coverage rates […] bar graphs and specific colors
* Support for large projects: overview pages allow quick browsing of coverage data by providing three levels of detail: directory view, file view and source code view.

Using Code Coverage Tools in the Linux Kernel
gcov only provides statement and branch coverage. In order to get coverage data, programs must be compiled by gcc with the -fprofile-arcs and -ftest-coverage flags […] When the program terminates the counters are dumped to a file.
Once a program has terminated and the gcov counter data (.da files) exist, gcov is capable of analyzing the files and producing coverage output. To see the coverage data for a user space program, one may simply run gcov program.c where program.c is the source file. The .da file must also exist in the same directory.

lcov provides scripts to clear the gcov kernel counters.
lcov –zerocounters
Capture the gcov data by calling lcov with the capture option (-c), specifying an output file (-o).
lcov -c -o kerneltest.info

gcov: a Test Coverage Program

Exemple de résultat pour Mozilla : http://people.mozilla.com/~mnandigama/codecoverage_html/index.html