linux-kernel - Re: [Keyrings] [PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

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Date:	Sat, 10 Jan 2015 12:29:21 +0200
From:	Dmitry Kasatkin <dmitry.kasatkin@...il.com>
To:	David Howells <dhowells@...hat.com>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	keyrings <keyrings@...ux-nfs.org>,
	Dmitry Kasatkin <d.kasatkin@...sung.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Keyrings] [PATCH 2/2] MPILIB: Deobfuscate mpi_cmp

Hi,

Thank you. Indeed '-cmp' is much more clear.

Ack.

- Dmitry

On 9 January 2015 at 13:00, David Howells <dhowells@...hat.com> wrote:
> This looks very reasonable.  cc'ing Dmitry for his check.
>
> David
> ---
> Rasmus Villemoes <linux@...musvillemoes.dk> wrote:
>
>> The condition preceding 'return 1;' makes my head hurt. At this point,
>> we know that u and v have the same sign; if they are negative, they
>> compare opposite to how their absolute values compare (which
>> mpihelp_cmp found for us), otherwise cmp itself is the
>> answer. Negating cmp is ok since mpihelp_cmp returns {-1,0,1};
>> -INT_MIN==INT_MIN won't bite us.
>>
>> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
>> ---
>>  lib/mpi/mpi-cmp.c | 8 +++-----
>>  1 file changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/lib/mpi/mpi-cmp.c b/lib/mpi/mpi-cmp.c
>> index 3801694240d8..d25e9e96c310 100644
>> --- a/lib/mpi/mpi-cmp.c
>> +++ b/lib/mpi/mpi-cmp.c
>> @@ -61,10 +61,8 @@ int mpi_cmp(MPI u, MPI v)
>>       if (!usize)
>>               return 0;
>>       cmp = mpihelp_cmp(u->d, v->d, usize);
>> -     if (!cmp)
>> -             return 0;
>> -     if ((cmp < 0 ? 1 : 0) == (u->sign ? 1 : 0))
>> -             return 1;
>> -     return -1;
>> +     if (u->sign)
>> +             return -cmp;
>> +     return cmp;
>>  }
>>  EXPORT_SYMBOL_GPL(mpi_cmp);
>> --
>> 2.1.3
> _______________________________________________
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> Keyrings@...ux-nfs.org
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-- 
Thanks,
Dmitry
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