xen/docs/misc/coverage.markdown

Coverage support for Xen

Coverare support allow you to get coverage information from Xen execution. You can see how many times a line is executed.

The compiler have specific options that enable the collection of these information. Every basic block in the code will be instructed by the compiler to compute these statistics. It should not be used in production as it slow down your hypervisor.

Enable coverage

Test coverage support can be turned on compiling Xen with coverage option set to y.

Something like: cd xen make coverage=y

(or change your Config.mk file).

Extract coverage data

The way GCC and other tools deal with coverage information is to use some files created during build phase (.gcno) and some files produced by executing the program (.gcda). The program in this case is Xen but Xen cannot write files so the way you can use coverage from Xen is extract coverage data from Xen and then split these information into files.

To extract data you use a simple utility called xencov. Mainly xencore allow you to do 3 operations:

• xencov read extract data
• xencov reset reset all coverage counters
• xencov read-reset extract data and reset counters at the same time.

Another utility (TODO) is used to split extracted data file into files needed by userspace tools.