Re: UBSAN: run-time undefined behavior sanity checker

From	Dave Jones <davej@codemonkey.org.uk>
Newsgroups	linux.kernel
Subject	Re: UBSAN: run-time undefined behavior sanity checker
Date	2016-02-01 23:20 +0100
Message-ID	<qXuZb-112-5@gated-at.bofh.it> (permalink)
References	(2 earlier) <qTN4o-6Dx-39@gated-at.bofh.it> <qTNnJ-73X-27@gated-at.bofh.it> <qUQ0a-54G-19@gated-at.bofh.it> <qXpd9-5p0-23@gated-at.bofh.it> <qXpd8-5p0-21@gated-at.bofh.it>
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On Mon, Feb 01, 2016 at 07:08:46PM +0300, Andrey Ryabinin wrote:

 > >  > > tried it on hangs the same way, really early.  Any thoughts on how to chase this down ?
 > >  > Try to disable instrumentation for early code, like in the patch bellow.
 > > This didn't help.
 > 
 > So after I enabled UBSAN_ALIGNMENT in your config, the kernel didn't boot.
 > That is because unaligned access happens before lockdep_init() so ubsan callback takes the
 > spinlock before locked_init() which is not allowed.
 
 > Could you try it without CONFIG_DEBUG_LOCKDEP?
 > Or alternatively with patch like this:

Tried with the patch, seems to work fine now.

thanks,
	Dave

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Re: UBSAN: run-time undefined behavior sanity checker Andrey Ryabinin <aryabinin@virtuozzo.com> - 2016-02-01 17:10 +0100
  Re: UBSAN: run-time undefined behavior sanity checker Dave Jones <davej@codemonkey.org.uk> - 2016-02-01 23:20 +0100

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