[PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[Daniel Latypov]

Recent changes have made it so the current set is not sufficient.
Namely, CONFIG_DEBUG_INFO is not being set even when explicitly asked.

Specifying a version of the debug info fixes this.
Pick CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as an option that's
hopefully less fragile (esp. given we're tied to GCC 6 and lower).

Signed-off-by: Daniel Latypov <dlatypov@google.com>
---
 Documentation/dev-tools/kunit/running_tips.rst | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/dev-tools/kunit/running_tips.rst b/Documentation/dev-tools/kunit/running_tips.rst
index 7b6d26a25959..c36f6760087d 100644
--- a/Documentation/dev-tools/kunit/running_tips.rst
+++ b/Documentation/dev-tools/kunit/running_tips.rst
@@ -114,6 +114,7 @@ Instead of enabling ``CONFIG_GCOV_KERNEL=y``, we can set these options:
 
 	CONFIG_DEBUG_KERNEL=y
 	CONFIG_DEBUG_INFO=y
+	CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
 	CONFIG_GCOV=y
 
 
@@ -122,7 +123,7 @@ Putting it together into a copy-pastable sequence of commands:
 .. code-block:: bash
 
 	# Append coverage options to the current config
-	$ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
+	$ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
 	$ ./tools/testing/kunit/kunit.py run
 	# Extract the coverage information from the build dir (.kunit/)
 	$ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/

base-commit: b14ffae378aa1db993e62b01392e70d1e585fb23
-- 
2.35.1.1021.g381101b075-goog

Re: [PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[David Gow]

On Sat, Mar 26, 2022 at 8:34 AM Daniel Latypov <dlatypov@google.com> wrote:
>
> Recent changes have made it so the current set is not sufficient.
> Namely, CONFIG_DEBUG_INFO is not being set even when explicitly asked.
>
> Specifying a version of the debug info fixes this.
> Pick CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as an option that's
> hopefully less fragile (esp. given we're tied to GCC 6 and lower).
>
> Signed-off-by: Daniel Latypov <dlatypov@google.com>
> ---

Looks good to me. One idea below, but it's a bit subjective and I'm
fine with this going in as-is if you prefer.

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

Cheers,
-- Daivd

>  Documentation/dev-tools/kunit/running_tips.rst | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/dev-tools/kunit/running_tips.rst b/Documentation/dev-tools/kunit/running_tips.rst
> index 7b6d26a25959..c36f6760087d 100644
> --- a/Documentation/dev-tools/kunit/running_tips.rst
> +++ b/Documentation/dev-tools/kunit/running_tips.rst
> @@ -114,6 +114,7 @@ Instead of enabling ``CONFIG_GCOV_KERNEL=y``, we can set these options:
>
>         CONFIG_DEBUG_KERNEL=y
>         CONFIG_DEBUG_INFO=y
> +       CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
>         CONFIG_GCOV=y
>
>
> @@ -122,7 +123,7 @@ Putting it together into a copy-pastable sequence of commands:
>  .. code-block:: bash
>
>         # Append coverage options to the current config
> -       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> +       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
>         $ ./tools/testing/kunit/kunit.py run

Would we want to instead use a chain of --kconfig_add arguments? (I
think there are advantages either way...)


>         # Extract the coverage information from the build dir (.kunit/)
>         $ lcov -t "my_kunit_tests" -o coverage.info -c -d .kunit/
>
> base-commit: b14ffae378aa1db993e62b01392e70d1e585fb23
> --
> 2.35.1.1021.g381101b075-goog
>

Re: [PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[Daniel Latypov]

On Fri, Mar 25, 2022 at 9:56 PM David Gow <davidgow@google.com> wrote:
>

<snip>

> >         # Append coverage options to the current config
> > -       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> > +       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> >         $ ./tools/testing/kunit/kunit.py run
>
> Would we want to instead use a chain of --kconfig_add arguments? (I
> think there are advantages either way...)

I've been considering this ever since the --kconfig_add patch was accepted.
It's more compatible w/ commands using --kunitconfig, but it also
looks very verbose.
E.g. it looks like

$ tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6
--kconfig_add=CONFIG_DEBUG_INFO=y
--kconfig_add=CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
--kconfig_add=CONFIG_GCOV=y

Neither looks very appealing to me, so I've just kept it as-is for now.

Maybe there's something we can do to make this easier (e.g. allowing
--kunitconfig to be repeated and mergable)?

Re: [PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[Brendan Higgins]

On Mon, Mar 28, 2022 at 12:35 PM Daniel Latypov <dlatypov@google.com> wrote:
>
> On Fri, Mar 25, 2022 at 9:56 PM David Gow <davidgow@google.com> wrote:
> >
>
> <snip>
>
> > >         # Append coverage options to the current config
> > > -       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> > > +       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> > >         $ ./tools/testing/kunit/kunit.py run
> >
> > Would we want to instead use a chain of --kconfig_add arguments? (I
> > think there are advantages either way...)
>
> I've been considering this ever since the --kconfig_add patch was accepted.
> It's more compatible w/ commands using --kunitconfig, but it also
> looks very verbose.
> E.g. it looks like
>
> $ tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6
> --kconfig_add=CONFIG_DEBUG_INFO=y
> --kconfig_add=CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
> --kconfig_add=CONFIG_GCOV=y

I don't think it's *that* much more verbose, but I see your point. I
personally prefer this, but not enough to argue about it.

> Neither looks very appealing to me, so I've just kept it as-is for now.
>
> Maybe there's something we can do to make this easier (e.g. allowing
> --kunitconfig to be repeated and mergable)?

I would like --kunitconfig to be repeadable and mergable.

Re: [PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[Daniel Latypov]

On Mon, Mar 28, 2022 at 11:54 AM 'Brendan Higgins' via KUnit
Development <kunit-dev@googlegroups.com> wrote:
>
> On Mon, Mar 28, 2022 at 12:35 PM Daniel Latypov <dlatypov@google.com> wrote:
> >
> > On Fri, Mar 25, 2022 at 9:56 PM David Gow <davidgow@google.com> wrote:
> > >
> >
> > <snip>
> >
> > > >         # Append coverage options to the current config
> > > > -       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> > > > +       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> > > >         $ ./tools/testing/kunit/kunit.py run
> > >
> > > Would we want to instead use a chain of --kconfig_add arguments? (I
> > > think there are advantages either way...)
> >
> > I've been considering this ever since the --kconfig_add patch was accepted.
> > It's more compatible w/ commands using --kunitconfig, but it also
> > looks very verbose.
> > E.g. it looks like
> >
> > $ tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6
> > --kconfig_add=CONFIG_DEBUG_INFO=y
> > --kconfig_add=CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
> > --kconfig_add=CONFIG_GCOV=y
>
> I don't think it's *that* much more verbose, but I see your point. I
> personally prefer this, but not enough to argue about it.

I personally prefer it too, but I'm biased as the person who added
--kconfig_add.
They're both ugly enough I'd figured I'd save the bikeshedding for
another patch.

>
> > Neither looks very appealing to me, so I've just kept it as-is for now.
> >
> > Maybe there's something we can do to make this easier (e.g. allowing
> > --kunitconfig to be repeated and mergable)?
>
> I would like --kunitconfig to be repeadable and mergable.

Ack.
There's some things to consider first.

1. This will conflict w/
https://patchwork.kernel.org/project/linux-kselftest/patch/20220226212325.2984807-1-dlatypov@google.com/,
so I'm going to wait until that gets merged first.

2. some kconfigs can be incompatible (e.g. these options only work on
UML, can't combine w/ a non-UML compatible file)
How do we make this less of a footgun?
We'd talked about how it'd be nice if kconfig/"make olddefconfig"
could print out *why* options get dropped (either they're not visible,
have unmet deps, etc.). If we had that, I'd feel more comfortable w/
repeatable kunitconfig.

3. People have the ability to do this already if they're really sure it's safe
$ cat <files...> | ./tools/testing/kunit/kunit.py run --kunitconfig=/dev/stdin

4. are we committed to supporting a "uml_coverage.kunitconfig" file?
As shown by the existence of this patch, we've let it get broken for a
bit, at least against linux-next (afaik, it was working on
torvalds/master up until the 5.18 window opened and we had some
patches reworking CONFIG_DEBUG_INFO).

These instructions exist so others don't have to try and re-figure out
the steps/workarounds.
But they're not more formally "part of KUnit" since no one has had the
expertise to maintain it (and fix issues like the reliance on gcc-6),
etc.

Creating a kunitconfig file for this will further imply ownership.

Re: [PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[Brendan Higgins]

On Mon, Mar 28, 2022 at 2:58 PM 'Daniel Latypov' via KUnit Development
<kunit-dev@googlegroups.com> wrote:
>
> On Mon, Mar 28, 2022 at 11:54 AM 'Brendan Higgins' via KUnit
> Development <kunit-dev@googlegroups.com> wrote:
> >
> > On Mon, Mar 28, 2022 at 12:35 PM Daniel Latypov <dlatypov@google.com> wrote:
> > >
> > > On Fri, Mar 25, 2022 at 9:56 PM David Gow <davidgow@google.com> wrote:
> > > >
> > >
> > > <snip>
> > >
> > > > >         # Append coverage options to the current config
> > > > > -       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> > > > > +       $ echo -e "CONFIG_DEBUG_KERNEL=y\nCONFIG_DEBUG_INFO=y\nCONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y\nCONFIG_GCOV=y" >> .kunit/.kunitconfig
> > > > >         $ ./tools/testing/kunit/kunit.py run
> > > >
> > > > Would we want to instead use a chain of --kconfig_add arguments? (I
> > > > think there are advantages either way...)
> > >
> > > I've been considering this ever since the --kconfig_add patch was accepted.
> > > It's more compatible w/ commands using --kunitconfig, but it also
> > > looks very verbose.
> > > E.g. it looks like
> > >
> > > $ tools/testing/kunit/kunit.py run --make_options=CC=/usr/bin/gcc-6
> > > --kconfig_add=CONFIG_DEBUG_INFO=y
> > > --kconfig_add=CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y
> > > --kconfig_add=CONFIG_GCOV=y
> >
> > I don't think it's *that* much more verbose, but I see your point. I
> > personally prefer this, but not enough to argue about it.
>
> I personally prefer it too, but I'm biased as the person who added
> --kconfig_add.
> They're both ugly enough I'd figured I'd save the bikeshedding for
> another patch.
>
> >
> > > Neither looks very appealing to me, so I've just kept it as-is for now.
> > >
> > > Maybe there's something we can do to make this easier (e.g. allowing
> > > --kunitconfig to be repeated and mergable)?
> >
> > I would like --kunitconfig to be repeadable and mergable.
>
> Ack.
> There's some things to consider first.

I wasn't saying I want you to do it now. I just like the idea.

> 1. This will conflict w/
> https://patchwork.kernel.org/project/linux-kselftest/patch/20220226212325.2984807-1-dlatypov@google.com/,
> so I'm going to wait until that gets merged first.

Agreed.

> 2. some kconfigs can be incompatible (e.g. these options only work on
> UML, can't combine w/ a non-UML compatible file)
> How do we make this less of a footgun?
> We'd talked about how it'd be nice if kconfig/"make olddefconfig"
> could print out *why* options get dropped (either they're not visible,
> have unmet deps, etc.). If we had that, I'd feel more comfortable w/
> repeatable kunitconfig.

Good point. Something to think about.

> 3. People have the ability to do this already if they're really sure it's safe
> $ cat <files...> | ./tools/testing/kunit/kunit.py run --kunitconfig=/dev/stdin

Sure, but I still think multiple --kunitconfig s would be a good
feature to add. I think it makes it a bit easier to think about mixing
and matching kunitconfigs.

> 4. are we committed to supporting a "uml_coverage.kunitconfig" file?
> As shown by the existence of this patch, we've let it get broken for a
> bit, at least against linux-next (afaik, it was working on
> torvalds/master up until the 5.18 window opened and we had some
> patches reworking CONFIG_DEBUG_INFO).

Good point. I don't think we want to get in that business. UML
Coverage needs a lot of work, and I don't think we have the time or
resources to own that work by ourselves.

If someone else wants to add - and then own - such a kunitconfig, I
would fully support them and maybe even help them a bit, but I don't
want to own such a file until UML coverage gets a bit more stable.

> These instructions exist so others don't have to try and re-figure out
> the steps/workarounds.
> But they're not more formally "part of KUnit" since no one has had the
> expertise to maintain it (and fix issues like the reliance on gcc-6),
> etc.
>
> Creating a kunitconfig file for this will further imply ownership.

Agreed.

Re: [PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[Maxime Ripard]

[-- Attachment #1: Type: text/plain, Size: 532 bytes --]

On Fri, Mar 25, 2022 at 05:33:56PM -0700, Daniel Latypov wrote:
> Recent changes have made it so the current set is not sufficient.
> Namely, CONFIG_DEBUG_INFO is not being set even when explicitly asked.
> 
> Specifying a version of the debug info fixes this.
> Pick CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as an option that's
> hopefully less fragile (esp. given we're tied to GCC 6 and lower).
> 
> Signed-off-by: Daniel Latypov <dlatypov@google.com>

Tested-by: Maxime Ripard <maxime@cerno.tech>

Thanks!
Maxime

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Re: [PATCH] Documentation: kunit: update kconfig options needed for UML coverage

[Brendan Higgins]

On Fri, Mar 25, 2022 at 8:34 PM Daniel Latypov <dlatypov@google.com> wrote:
>
> Recent changes have made it so the current set is not sufficient.
> Namely, CONFIG_DEBUG_INFO is not being set even when explicitly asked.
>
> Specifying a version of the debug info fixes this.
> Pick CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as an option that's
> hopefully less fragile (esp. given we're tied to GCC 6 and lower).
>
> Signed-off-by: Daniel Latypov <dlatypov@google.com>

I agree with David's comment. Otherwise,

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>