mbox series

[0/2] um: kunit: Add Clang support for CONFIG_GCOV

Message ID 20231020092159.2486063-1-michal.winiarski@intel.com
Headers show
Series um: kunit: Add Clang support for CONFIG_GCOV | expand

Message

Michał Winiarski Oct. 20, 2023, 9:21 a.m. UTC 
Clang uses a different set of CLI args for coverage, and the output
needs to be processed by a different set of tools.
Update the Makefile and add an example of usage in kunit docs.

Michał Winiarski (2):
  arch: um: Add Clang coverage support
  Documentation: kunit: Add clang UML coverage example

 Documentation/dev-tools/kunit/running_tips.rst | 11 +++++++++++
 arch/um/Makefile-skas                          |  5 +++++
 2 files changed, 16 insertions(+)

Comments

Arthur Grillo Oct. 23, 2023, 2:58 p.m. UTC | #1 
On 20/10/23 06:21, Michał Winiarski wrote:
> Clang uses a different set of CLI args for coverage, and the output
> needs to be processed by a different set of tools.
> Update the Makefile and add an example of usage in kunit docs.

Great change! It's great not to rely on older versions of GCC for
that.

I was able to generate coverage reports, but I have a few of things to
note:

When I ran the kunit.py it generated this warning several times:

WARNING: modpost: vmlinux (__llvm_covfun): unexpected non-allocatable section.
Did you forget to use "ax"/"aw" in a .S file?
Note that for example <linux/init.h> contains
section definitions for use in .S files.

Maybe it would be great to know why this is happening.

Also, the linker consumed a lot of RAM to build the kernel with those
additional flags, but maybe this is expected :P.

Best Regards,
~Arthur Grillo

> 
> Michał Winiarski (2):
>   arch: um: Add Clang coverage support
>   Documentation: kunit: Add clang UML coverage example
> 
>  Documentation/dev-tools/kunit/running_tips.rst | 11 +++++++++++
>  arch/um/Makefile-skas                          |  5 +++++
>  2 files changed, 16 insertions(+)
>
David Gow Oct. 25, 2023, 8:25 a.m. UTC | #2 
On Fri, 20 Oct 2023 at 17:22, Michał Winiarski
<michal.winiarski@intel.com> wrote:
>
> Clang uses a different set of command line arguments for enabling
> coverage.
>
> Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
> ---

This works brilliantly here -- I'm very glad to finally be able to use
something newer than gcc 6!

I assume this will go in via the UML tree, but if you want, we can
take it via KUnit.

Tested-by: David Gow <davidgow@google.com>

Cheers,
-- David


>  arch/um/Makefile-skas | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/um/Makefile-skas b/arch/um/Makefile-skas
> index ac35de5316a6..67323b028999 100644
> --- a/arch/um/Makefile-skas
> +++ b/arch/um/Makefile-skas
> @@ -4,7 +4,12 @@
>  #
>
>  GPROF_OPT += -pg
> +
> +ifdef CONFIG_CC_IS_CLANG
> +GCOV_OPT += -fprofile-instr-generate -fcoverage-mapping
> +else
>  GCOV_OPT += -fprofile-arcs -ftest-coverage
> +endif
>
>  CFLAGS-$(CONFIG_GCOV) += $(GCOV_OPT)
>  CFLAGS-$(CONFIG_GPROF) += $(GPROF_OPT)
> --
> 2.42.0
>