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From: Eric Biggers <>
To: Ard Biesheuvel <>
Subject: Re: [PATCH v2] crypto: algapi - make crypto_xor() and crypto_inc() alignment agnostic
Date: Sat, 4 Feb 2017 13:27:12 -0800	[thread overview]
Message-ID: <20170204212712.GB5621@zzz> (raw)
In-Reply-To: <20170204212038.GA5621@zzz>

On Sat, Feb 04, 2017 at 01:20:38PM -0800, Eric Biggers wrote:
> Unfortunately this is still broken, for two different reasons.  First, if the
> pointers have the same relative misalignment, then 'delta' and 'misalign' will
> be set to 0 and long accesses will be used, even though the pointers may
> actually be misaligned, e.g. 0x80000001 and 0x90000001.  Second, if the pointers
> have a relative misalignent that is not a power-of-2, then 'misalign' will be
> set to the wrong value.  For example, with delta=3, it's actually only safe to
> do byte accesses, but the code will set misalign=2 and do u16 accesses.

Correction: for the second issue I think I mixed up ffs and fls, so that part of
the code was right.  But it may still be a good idea to separate out the
different cases.


  reply	other threads:[~2017-02-04 21:27 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-02 15:56 Ard Biesheuvel
2017-02-04 21:20 ` Eric Biggers
2017-02-04 21:27   ` Eric Biggers [this message]
2017-02-04 21:49   ` Ard Biesheuvel

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