linux-kernel - Re: [PATCH v3 1/3] kasan: switch kunit tests to console tracepoints

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Date:   Tue, 12 Dec 2023 10:32:45 +0100
From:   Marco Elver <elver@...gle.com>
To:     Paul Heidekrüger <paul.heidekrueger@....de>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Collingbourne <pcc@...gle.com>,
        andrey.konovalov@...ux.dev,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-trace-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v3 1/3] kasan: switch kunit tests to console tracepoints

On Tue, 12 Dec 2023 at 10:19, Paul Heidekrüger <paul.heidekrueger@....de> wrote:
>
> On 12.12.2023 00:37, Andrey Konovalov wrote:
> > On Tue, Dec 12, 2023 at 12:35 AM Paul Heidekrüger
> > <paul.heidekrueger@....de> wrote:
> > >
> > > Using CONFIG_FTRACE=y instead of CONFIG_TRACEPOINTS=y produces the same error
> > > for me.
> > >
> > > So
> > >
> > >         CONFIG_KUNIT=y
> > >         CONFIG_KUNIT_ALL_TESTS=n
> > >         CONFIG_FTRACE=y
> > >         CONFIG_KASAN=y
> > >         CONFIG_KASAN_GENERIC=y
> > >         CONFIG_KASAN_KUNIT_TEST=y
> > >
> > > produces
> > >
> > >         ➜   ./tools/testing/kunit/kunit.py run --kunitconfig=mm/kasan/.kunitconfig --arch=arm64
> > >         Configuring KUnit Kernel ...
> > >         Regenerating .config ...
> > >         Populating config with:
> > >         $ make ARCH=arm64 O=.kunit olddefconfig CC=clang
> > >         ERROR:root:Not all Kconfig options selected in kunitconfig were in the generated .config.
> > >         This is probably due to unsatisfied dependencies.
> > >         Missing: CONFIG_KASAN_KUNIT_TEST=y
> > >
> > > By that error message, CONFIG_FTRACE appears to be present in the generated
> > > config, but CONFIG_KASAN_KUNIT_TEST still isn't. Presumably,
> > > CONFIG_KASAN_KUNIT_TEST is missing because of an unsatisfied dependency, which
> > > must be CONFIG_TRACEPOINTS, unless I'm missing something ...
> > >
> > > If I just generate an arm64 defconfig and select CONFIG_FTRACE=y,
> > > CONFIG_TRACEPOINTS=y shows up in my .config. So, maybe this is kunit.py-related
> > > then?
> > >
> > > Andrey, you said that the tests have been working for you; are you running them
> > > with kunit.py?
> >
> > No, I just run the kernel built with a config file that I put together
> > based on defconfig.
>
> Ah. I believe I've figured it out.
>
> When I add CONFIG_STACK_TRACER=y in addition to CONFIG_FTRACE=y, it works.

CONFIG_FTRACE should be enough - maybe also check x86 vs. arm64 to debug more.

> CONFIG_STACK_TRACER selects CONFIG_FUNCTION_TRACER, CONFIG_FUNCTION_TRACER
> selects CONFIG_GENERIC_TRACER, CONFIG_GENERIC_TRACER selects CONFIG_TRACING, and
> CONFIG_TRACING selects CONFIG_TRACEPOINTS.
>
> CONFIG_BLK_DEV_IO_TRACE=y also works instead of CONFIG_STACK_TRACER=y, as it
> directly selects CONFIG_TRACEPOINTS.
>
> CONFIG_FTRACE=y on its own does not appear suffice for kunit.py on arm64.

When you build manually with just CONFIG_FTRACE, is CONFIG_TRACEPOINTS enabled?

> I believe the reason my .kunitconfig as well as the existing
> mm/kfence/.kunitconfig work on X86 is because CONFIG_TRACEPOINTS=y is present in
> an X86 defconfig.
>
> Does this make sense?
>
> Would you welcome a patch addressing this for the existing
> mm/kfence/.kunitconfig?
>
> I would also like to submit a patch for an mm/kasan/.kunitconfig. Do you think
> that would be helpful too?
>
> FWICT, kernel/kcsan/.kunitconfig might also be affected since
> CONFIG_KCSAN_KUNIT_TEST also depends on CONFIG_TRACEPOITNS, but I would have to
> test that. That could be a third patch.

I'd support figuring out the minimal config (CONFIG_FTRACE or
something else?) that satisfies the TRACEPOINTS dependency. I always
thought CONFIG_FTRACE ought to be the one config option, but maybe
something changed.

Also maybe one of the tracing maintainers can help untangle what's
going on here.

Thanks,
-- Marco