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Groups > linux.kernel > #1542837
| From | David Laight <David.Laight@ACULAB.COM> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | RE: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function |
| Date | 2016-12-15 16:50 +0100 |
| Message-ID | <sOGsa-7xD-1@gated-at.bofh.it> (permalink) |
| References | (4 earlier) <sODkB-5Hj-7@gated-at.bofh.it> <sODkB-5Hj-9@gated-at.bofh.it> <sODND-5R6-3@gated-at.bofh.it> <sOEJH-6pt-3@gated-at.bofh.it> <sOFFL-72d-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: Hannes Frederic Sowa
> Sent: 15 December 2016 14:57
> On 15.12.2016 14:56, David Laight wrote:
> > From: Hannes Frederic Sowa
> >> Sent: 15 December 2016 12:50
> >> On 15.12.2016 13:28, David Laight wrote:
> >>> From: Hannes Frederic Sowa
> >>>> Sent: 15 December 2016 12:23
> >>> ...
> >>>> Hmm? Even the Intel ABI expects alignment of unsigned long long to be 8
> >>>> bytes on 32 bit. Do you question that?
> >>>
> >>> Yes.
> >>>
> >>> The linux ABI for x86 (32 bit) only requires 32bit alignment for u64 (etc).
> >>
> >> Hmm, u64 on 32 bit is unsigned long long and not unsigned long. Thus I
> >> am actually not sure if the ABI would say anything about that (sorry
> >> also for my wrong statement above).
> >>
> >> Alignment requirement of unsigned long long on gcc with -m32 actually
> >> seem to be 8.
> >
> > It depends on the architecture.
> > For x86 it is definitely 4.
>
> May I ask for a reference?
Ask anyone who has had to do compatibility layers to support 32bit
binaries on 64bit systems.
> I couldn't see unsigned long long being
> mentioned in the ia32 abi spec that I found. I agree that those accesses
> might be synthetically assembled by gcc and for me the alignment of 4
> would have seemed natural. But my gcc at least in 32 bit mode disagrees
> with that.
Try (retyped):
echo 'struct { long a; long long b; } s; int bar { return sizeof s; }' >foo.c
gcc [-m32] -O2 -S foo.c; cat foo.s
And look at what is generated.
> Right now ipv6 addresses have an alignment of 4. So we couldn't even
> naturally pass them to siphash but would need to copy them around, which
> I feel like a source of bugs.
That is more of a problem on systems that don't support misaligned accesses.
Reading the 64bit values with two explicit 32bit reads would work.
I think you can get gcc to do that by adding an aligned(4) attribute to the
structure member.
David
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[PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 05:10 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-14 12:40 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 14:20 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-14 16:20 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 20:50 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Herbert Xu <herbert@gondor.apana.org.au> - 2016-12-15 09:00 +0100
Re: [kernel-hardening] Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Daniel Micay <danielmicay@gmail.com> - 2016-12-15 09:20 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 13:50 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-14 23:10 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 00:40 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 09:40 +0100
RE: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function David Laight <David.Laight@ACULAB.COM> - 2016-12-15 12:10 +0100
RE: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function David Laight <David.Laight@ACULAB.COM> - 2016-12-15 13:30 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 14:00 +0100
RE: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function David Laight <David.Laight@ACULAB.COM> - 2016-12-15 15:00 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 16:00 +0100
RE: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function David Laight <David.Laight@ACULAB.COM> - 2016-12-15 16:50 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 17:00 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 20:00 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 21:40 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 21:50 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 22:20 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 22:20 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Peter Zijlstra <peterz@infradead.org> - 2016-12-15 23:10 +0100
Re: [kernel-hardening] Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 22:20 +0100
Re: [kernel-hardening] Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-15 22:20 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Peter Zijlstra <peterz@infradead.org> - 2016-12-15 22:20 +0100
Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function Hannes Frederic Sowa <hannes@stressinduktion.org> - 2016-12-15 13:30 +0100
[PATCH v3 2/3] secure_seq: use siphash24 instead of md5_transform "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 19:50 +0100
Re: [PATCH v3 2/3] secure_seq: use siphash24 instead of md5_transform kbuild test robot <lkp@intel.com> - 2016-12-14 22:50 +0100
[PATCH v3 1/3] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 19:50 +0100
[PATCH v3 3/3] random: use siphash24 instead of md5 for get_random_int/long "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 19:50 +0100
Re: [PATCH v3 3/3] random: use siphash24 instead of md5 for get_random_int/long kbuild test robot <lkp@intel.com> - 2016-12-14 23:00 +0100
Re: [PATCH v3 3/3] random: use siphash24 instead of md5 for get_random_int/long kbuild test robot <lkp@intel.com> - 2016-12-14 23:10 +0100
RE: [PATCH v3 3/3] random: use siphash24 instead of md5 for get_random_int/long David Laight <David.Laight@ACULAB.COM> - 2016-12-15 11:20 +0100
Re: [PATCH v3 3/3] random: use siphash24 instead of md5 for get_random_int/long "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 20:00 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Tom Herbert <tom@herbertland.com> - 2016-12-14 20:20 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 20:40 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 22:00 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Tom Herbert <tom@herbertland.com> - 2016-12-14 22:40 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 00:00 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 00:20 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Christian Kujau <lists@nerdbynature.de> - 2016-12-18 01:10 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Tom Herbert <tom@herbertland.com> - 2016-12-15 00:20 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 00:40 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-15 01:30 +0100
RE: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function David Laight <David.Laight@ACULAB.COM> - 2016-12-15 11:30 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function Linus Torvalds <torvalds@linux-foundation.org> - 2016-12-15 00:40 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function kbuild test robot <lkp@intel.com> - 2016-12-14 22:20 +0100
Re: [PATCH v3 1/3] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-14 22:30 +0100
[PATCH v4 3/4] secure_seq: use siphash instead of md5_transform "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 02:50 +0100
[PATCH v4 2/4] siphash: add N[qd]word helpers "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 02:50 +0100
[PATCH v4 4/4] random: use siphash instead of MD5 for get_random_int/long "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 02:50 +0100
[PATCH v4 1/4] siphash: add cryptographically secure hashtable function "Jason A. Donenfeld" <Jason@zx2c4.com> - 2016-12-15 02:50 +0100
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