linux-kernel - Re: [PATCH v2] kernel: add kcov code coverage

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Message-ID: <20160114092320.GB27083@node.shutemov.name>
Date:	Thu, 14 Jan 2016 11:23:20 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Drysdale <drysdale@...gle.com>,
	Kees Cook <keescook@...gle.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Tavis Ormandy <taviso@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>
Subject: Re: [PATCH v2] kernel: add kcov code coverage

On Thu, Jan 14, 2016 at 10:10:39AM +0100, Dmitry Vyukov wrote:
> On Thu, Jan 14, 2016 at 10:03 AM, Kirill A. Shutemov
> <kirill@...temov.name> wrote:
> > Hi,
> >
> > I've tried to build current -next with the patch. It has few reject, but
> > nothing major.
> >
> > Booting the kernel in qemu with CONFIG_KCOV=y has failed. It hangs on
> > "smpboot: Total of 3 processors activated (9178.27 BogoMIPS)"
> >
> > The interesting part is that I have only 2 cpu in this setup!
> >
> > Huh?
> >
> > CONFIG_KCOV=n works fine.
> 
> 
> Hi Kirill,
> 
> Thanks for testing.
> 
> I will try to reproduce this if you provide:
>  - location of the -next tree

The usual one:

git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20160114

>  - gcc revision

Current gcc-snapshot from Debian:

gcc version 6.0.0 20160105 (experimental) [trunk revision 232093] (Debian 20160105-1) 

>  - .config

Attached.

>  - qemu command line

Nothing fancy:

qemu-system-x86_64 -smp 2 -m 2048 -nographic -kernel bzImage -append "console=ttyS0 earlyprintk=serial"
 
> Alternatively, you can try to bulk disable instrumentation of
> everything related to boot process (by adding KCOV_INSTRUMENT := n to
> the Makefile). Most likely it is due to instrumentation. If it helps,
> try to bisect the the guilty files.

Okay, I'll try.

-- 
 Kirill A. Shutemov

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