This option enables gcov-based code profiling (e.g. for code coverage
measurements).

If unsure, say N.

Additionally specify CONFIG_GCOV_PROFILE_ALL=y to get profiling data
for the entire kernel. To enable profiling for specific files or
directories, add a line similar to the following to the respective
Makefile:

For a single file (e.g. main.o):
GCOV_PROFILE_main.o := y

For all files in one directory:
GCOV_PROFILE := y

To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
is specified, use:

GCOV_PROFILE_main.o := n
and:
GCOV_PROFILE := n

Note that the debugfs filesystem has to be mounted to access
profiling data.

source code:

kernel/gcov/