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Roger Pau Monné
6222e7cbaa
So it can be used by both gcc and clang. Just add the Kconfig option and modify the makefiles so the llvm coverage specific code can be added in a follow up patch. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Acked-by: Wei Liu <wei.liu2@citrix.com> [jb: also change the shim config]
78 lines
2.4 KiB
Markdown
78 lines
2.4 KiB
Markdown
# Coverage support for Xen
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Coverage support allows you to get coverage information from Xen execution.
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You can see how many times a line is executed.
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Some compilers have specific options that enable the collection of this
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information. Every basic block in the code will be instrumented by the compiler
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to compute these statistics. It should not be used in production as it slows
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down your hypervisor.
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## Enable coverage
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Test coverage support can be turned on compiling Xen with the `CONFIG_COVERAGE`
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option set to `y`.
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Change your `.config` or run `make -C xen menuconfig`.
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## Extract coverage data
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To extract data you use a simple utility called `xencov`.
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It allows you to do 2 operations:
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* `xencov read` extract data
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* `xencov reset` reset all coverage counters
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Another utility (`xencov_split`) is used to split extracted data file into
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files needed by userspace tools.
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## Split coverage data
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Once you extracted data from Xen, it is time to create files which the coverage
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tools can understand. To do it you need to run `xencov_split` utility.
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The utility just takes an input file and splits the blob into gcc .gcda files
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in the same directory that you execute the script. As file names are generated
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relative to the current directory, it could be a good idea to run the script
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from `/` on your build machine.
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Code for splitting the blob is put in another utility for some reason:
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* It is simpler to maintain a high level script than a C program;
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* You don't need to execute on the Xen host so you just need to copy the file to
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your development box (you usually need development files anyway).
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## Possible use
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**This section is just an example on how to use these tools!**
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This example assumes you compiled Xen from `~/xen-unstable` and installed into
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the host. **Consider that if you even recompile Xen you are not able to use
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blob extracted from xencov!**
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* Ensure the `lcov` package is installed
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* From the Xen host machine extract the coverage blob
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cd /root
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xencov read coverage.dat
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* Copy the extracted blob to your dev machine
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cd ~
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scp root@myhost:coverage.dat
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* Extract the coverage information
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(cd / && xencov_split ~/coverage.dat)
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* Produce coverage html output
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cd ~/xen-unstable
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rm -rf cov.info cov
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geninfo -o cov.info xen
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mkdir cov
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genhtml -o cov cov.info
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* See output in a browser
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firefox cov/index.html
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