linux-kernel - Re: [PATCH v6] kernel: add kcov code coverage

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Message-ID: <CACT4Y+YygZitF6508qNX9885+nWu7iY9YVqdtE0bCA2+soTp_Q@mail.gmail.com>
Date:	Thu, 4 Feb 2016 16:07:16 +0100
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	syzkaller <syzkaller@...glegroups.com>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Tavis Ormandy <taviso@...gle.com>,
	Will Deacon <will.deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Kees Cook <keescook@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Drysdale <drysdale@...gle.com>,
	linux-arm-kernel@...ts.infradead.org,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH v6] kernel: add kcov code coverage

On Tue, Feb 2, 2016 at 5:02 PM, Andrey Ryabinin <ryabinin.a.a@...il.com> wrote:
> 2016-01-25 16:00 GMT+03:00 Dmitry Vyukov <dvyukov@...gle.com>:
>
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index ecb9e75..cde6bd1 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -678,6 +678,26 @@ config DEBUG_STACKOVERFLOW
>>
>>           If in doubt, say "N".
>>
>> +config ARCH_HAS_KCOV
>> +       bool
>> +       help
>> +         KCOV does not have any arch-specific code, but currently it is enabled
>> +         only for x86_64. KCOV requires testing on other archs, and most likely
>> +         disabling of instrumentation for some early boot code.
>> +
>> +config KCOV
>> +       bool "Code coverage for fuzzing"
>> +       depends on ARCH_HAS_KCOV
>
> I think we should select DEBUG_FS here, since this useless without it.

Done in v7

> Also you placed this into 'Memory Debugging' submenu which seems wrong.

Any better suggestions?

>> +       help
>> +         KCOV exposes kernel code coverage information in a form suitable
>> +         for coverage-guided fuzzing (randomized testing).
>> +
>> +         If RANDOMIZE_BASE is enabled, PC values will not be stable across
>> +         different machines and across reboots. If you need stable PC values,
>> +         disable RANDOMIZE_BASE.
>> +
>> +         For more details, see Documentation/kcov.txt.
>> +
>>  source "lib/Kconfig.kmemcheck"
>>