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Date: Mon, 5 Feb 2024 12:34:20 +0100
From: Paul =?utf-8?Q?Heidekr=C3=BCger?= <paul.heidekrueger@tum.de>
To: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>, 
	Steven Rostedt <rostedt@goodmis.org>, Peter Collingbourne <pcc@google.com>, andrey.konovalov@linux.dev, 
	Andrew Morton <akpm@linux-foundation.org>, Alexander Potapenko <glider@google.com>, 
	Dmitry Vyukov <dvyukov@google.com>, Andrey Ryabinin <ryabinin.a.a@gmail.com>, 
	kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, 
	Andrey Konovalov <andreyknvl@google.com>, Masami Hiramatsu <mhiramat@kernel.org>, 
	linux-trace-kernel@vger.kernel.org, Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH v3 1/3] kasan: switch kunit tests to console tracepoints
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On 7 Jan 2024, at 19:22, Paul Heidekrüger wrote:

> On 12.12.2023 10:32, Marco Elver wrote:
>> On Tue, 12 Dec 2023 at 10:19, Paul Heidekrüger <paul.heidekrueger@tum.de> wrote:
>>>
>>> On 12.12.2023 00:37, Andrey Konovalov wrote:
>>>> On Tue, Dec 12, 2023 at 12:35 AM Paul Heidekrüger
>>>> <paul.heidekrueger@tum.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.
>
> See below.
>
>>> 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?
>
> When I add CONFIG_FTRACE and enter-key my way through the FTRACE prompts - I
> believe because CONFIG_FTRACE is a menuconfig? - at the beginning of a build,
> CONFIG_TRACEPOINTS does get set on arm64, yes.
>
> On X86, the defconfig already includes CONIFG_TRACEPOINTS.
>
> I also had a closer look at how kunit.py builds its configs.
> I believe it does something along the following lines:
>
>     cp <path_to_kunitconfig> .kunit/.config
>     make ARCH=arm64 O=.kunit olddefconfig
>
> On arm64, that isn't enough to set CONFIG_TRACEPOINTS; same behaviour when run
> outside of kunit.py.
>
> For CONFIG_TRACEPOINTS, `make ARCH=arm64 menuconfig` shows:
>
>     Symbol: TRACEPOINTS [=n]
>     Type  : bool
>     Defined at init/Kconfig:1920
>     Selected by [n]:
>     	- TRACING [=n]
>     	- BLK_DEV_IO_TRACE [=n] && FTRACE [=y] && SYSFS [=y] && BLOCK [=y]
>
> So, CONFIG_TRACING or CONFIG_BLK_DEV_IO_TRACE are the two options that prevent
> CONFIG_TRACEPOINTS from being set on arm64.
>
> For CONFIG_TRACING we have:
>
>     Symbol: TRACING [=n]
>     Type  : bool
>     Defined at kernel/trace/Kconfig:157
>     Selects: RING_BUFFER [=n] && STACKTRACE [=y] && TRACEPOINTS [=n] && NOP_TRACER [=n] && BINARY_PRINTF [=n] && EVENT_TRACING [=n] && TRACE_CLOCK [=y] && TASKS_RCU [=n]
>     Selected by [n]:
>     	- DRM_I915_TRACE_GEM [=n] && HAS_IOMEM [=y] && DRM_I915 [=n] && EXPERT [=n] && DRM_I915_DEBUG_GEM [=n]
>     	- DRM_I915_TRACE_GTT [=n] && HAS_IOMEM [=y] && DRM_I915 [=n] && EXPERT [=n] && DRM_I915_DEBUG_GEM [=n]
>     	- PREEMPTIRQ_TRACEPOINTS [=n] && (TRACE_PREEMPT_TOGGLE [=n] || TRACE_IRQFLAGS [=n])
>     	- GENERIC_TRACER [=n]
>     	- ENABLE_DEFAULT_TRACERS [=n] && FTRACE [=y] && !GENERIC_TRACER [=n]
>     	- FPROBE_EVENTS [=n] && FTRACE [=y] && FPROBE [=n] && HAVE_REGS_AND_STACK_ACCESS_API [=y]
>     	- KPROBE_EVENTS [=n] && FTRACE [=y] && KPROBES [=n] && HAVE_REGS_AND_STACK_ACCESS_API [=y]
>     	- UPROBE_EVENTS [=n] && FTRACE [=y] && ARCH_SUPPORTS_UPROBES [=y] && MMU [=y] && PERF_EVENTS [=n]
>     	- SYNTH_EVENTS [=n] && FTRACE [=y]
>     	- USER_EVENTS [=n] && FTRACE [=y]
>     	- HIST_TRIGGERS [=n] && FTRACE [=y] && ARCH_HAVE_NMI_SAFE_CMPXCHG [=y]
>
>>> 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.
>
> If we want a minimal config, setting CONFIG_BLK_DEV_IO_TRACE,
> CONFIG_SYNTH_EVENTS or CONFIG_USER_EVENTS seem like viable options, for
> instance. But AFAICT, setting them in the context of KASan doesn't really make
> sense, and I might be missing an obvious choice here too.
>
> What do you think?
>
>> Also maybe one of the tracing maintainers can help untangle what's
>> going on here.
>>
>> Thanks,
>> -- Marco
>
> Many thanks,
> Paul

Hi all,

Just giving this thread a polite bump, hoping that someone has some pointers.

The TL;DR is the following: I’m trying to run KASan KUnit tests with the 
following local .kunitconfig:

	CONFIG_KUNIT=y
	CONFIG_KUNIT_ALL_TESTS=n
	CONFIG_FTRACE=y
	CONFIG_KASAN=y
	CONFIG_KASAN_GENERIC=y
	CONFIG_KASAN_KUNIT_TEST=y

The problem is that on arm64, this does not appear to be enough to set all of 
CONFIG_KASAN_KUNIT_TEST’s dependencies, namely CONFIG_TRACEPOINTS.

An additional option is needed to enable CONFIG_TRACEPOINTS. As per `make 
menuconfig`, this is either CONFIG_BLK_DEV_IO_TRACE or any (combination of) 
option(s) that enable(s) CONFIG_TRACING. See the `make menuconfig` output in my 
previous email for details.

Which option do you think is appropriate here? Or am I missing something?

For anyone wanting to reproduce, use:
/tools/testing/kunit/kunit.py run —kunitconfig=<path_to_above_kunitconfig> --arch=arm64

Many thanks,
Paul