On Mon, Jun 12, 2023 at 06:18:35PM +0200, Peter Oberparleiter wrote:
> I'm unaware of any kbuild support for setting GCOV_PROFILE for a
> specific sub-directory from the command line, only from within the
> associated Makefile. I'm not sure how this could have worked in the past
> with the provide sample command line.
>
> Here's how GCOV_PROFILE evaluation works (from scripts/Makefile.lib):
>
> ifeq ($(CONFIG_GCOV_KERNEL),y)
> _c_flags += $(if $(patsubst n%,, \
> $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)),\
> $(CFLAGS_GCOV))
> endif
>
> This bit of Makefile code determines whether to add the flags needed to
> enabled gcov profiling (CFLAGS_GCOV) to the compiler flags for the
> current compilation unit (_c_flags) by looking at the concatenation of
> the following variables:
>
> - GCOV_PROFILE_<target base name>.o
> - GCOV_PROFILE
> - CONFIG_GCOV_PROFILE_ALL
>
> gcov flags are only added if this concatenation does not start with an
> "n", and at least one of these variables is set to a non-empty value
> other than "n" ("y" typically). The "starts with" part is required to
> enable precedence for the more specific variable, e.g. an "n" in
> GCOV_PROFILE_filename.o overwrites a "y" in GCOV_PROFILE.
>
> As you can see, there is no reference to a GCOV_PROFILE variable that is
> named after the sub-directory for which profiling should be enabled.
I've been digging through the git history, and I would swear I
hallucinated the whole thing except I have the code in ktest for driving
gcov and I swear it used to work :)
Anyways - any thoughts on how we might implement this? I really need a
way to specify directories to enable gcov for _without_ monkey patching;
that's not a viable workflow in an automated setup.
It seems like if we can get a list of directory prefixes for a path
(e.g. given fs/bcachefs/btree_iter.o it would return fs, fs/bcachefs) it
should be possible to extend the code you referenced.
