kernel profiling with kernbb and gcov

[Mark W. Krentel]

I'm trying to do kernel profiling with kernbb(8) and gcov(1), but
I can't get the kernel compile to accept the -ftest-coverage and
-fprofile-arcs options.

(1) Is it --test-coverage or -ftest-coverage, or does it matter?
kernbb(8) says the former, gcov(1) says the latter.

(2) How do I add these options to the kernel compile?  I tried adding
them to COPTFLAGS in make.conf, and all the individual files compile
ok, but when it tries to link them, it dies with a bazillion undefined
references.

    ffsl.o(.text+0x7e): In function `global constructors keyed to ffsl_GCOV':
    : undefined reference to `__gcov_init'
    ffsl.o(.data+0x44): undefined reference to `__gcov_merge_add'
    flsl.o(.text+0x7e): In function `global constructors keyed to flsl_GCOV':
    : undefined reference to `__gcov_init'
    flsl.o(.data+0x44): undefined reference to `__gcov_merge_add'

I can run "gcc -ftest-coverage -fprofile-arcs hello.c" for the "Hello,
world" program, and it works and gcov(1) is happy, but I can't get
these options into the kernel.

(3) How do I selectively add these options to just some of the source
files?  Do I run config (or "config -p") and hand edit the Makefile,
before "make depend && make"?

This is in 6.0-CURRENT as of a few days ago.

Thanks,

--Mark