linux-kernel - Re: [PATCH v2 1/2] crypto, sha1: export sha1

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Date:	Thu, 28 Jul 2011 17:29:35 +0200
From:	Mathias Krause <minipli@...glemail.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	"David S. Miller" <davem@...emloft.net>,
	linux-crypto@...r.kernel.org,
	Maxim Locktyukhin <maxim.locktyukhin@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] crypto, sha1: export sha1_update for reuse

On Thu, Jul 28, 2011 at 4:58 PM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> On Sun, Jul 24, 2011 at 07:53:13PM +0200, Mathias Krause wrote:
>>
>> diff --git a/include/crypto/sha.h b/include/crypto/sha.h
>> index 069e85b..7c46d0c 100644
>> --- a/include/crypto/sha.h
>> +++ b/include/crypto/sha.h
>> @@ -82,4 +82,9 @@ struct sha512_state {
>>       u8 buf[SHA512_BLOCK_SIZE];
>>  };
>>
>> +#if defined(CONFIG_CRYPTO_SHA1) || defined (CONFIG_CRYPTO_SHA1_MODULE)
>> +extern int crypto_sha1_update(struct shash_desc *desc, const u8 *data,
>> +                           unsigned int len);
>> +#endif
>
> Please remove the unnecessary #if.

The function will only be available when crypto/sha1_generic.o will
either be build into the kernel or build as a module. Without the #if
a potential wrong user of this function might not be detected as early
as at compilation time but as late as at link time, or even worse, as
late as on module load time -- which is pretty bad. IMHO it's better
to detect errors early, as in reading "error: implicit declaration of
function ‘crypto_sha1_update’" when trying to compile the code in
question instead of "Unknown symbol crypto_sha1_update" in dmesg when
trying to load the module. That for I would like to keep the #if.

Thanks for the review!

Mathias
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