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From: Stephan Mueller <smueller@chronox.de>
To: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
        kbuild test robot <fengguang.wu@intel.com>, kbuild@01.org,
        Dan Carpenter <dan.carpenter@oracle.com>, linux-crypto@vger.kernel.org,
        Randy Dunlap <rdunlap@infradead.org>, linux-next@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] DRBG: cleanup of preprocessor macros
Date: Sun, 29 Jun 2014 07:07:19 +0200
Message-ID: <3104100.drOBnqUFp8@myon.chronox.de>
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Am Sonntag, 29. Juni 2014, 12:20:15 schrieb Stephen Rothwell:

Hi Stephen,

> Hi Stephan,
> 
> On Sat, 28 Jun 2014 22:00:07 +0200 Stephan Mueller <smueller@chronox.de> 
wrote:
> > diff --git a/crypto/drbg.c b/crypto/drbg.c
> > index 6679a26..03a230e 100644
> > --- a/crypto/drbg.c
> > +++ b/crypto/drbg.c
> > @@ -102,8 +102,13 @@
> > 
> >  #if !defined(CONFIG_CRYPTO_DRBG_HASH) && \
> >  
> >  	!defined(CONFIG_CRYPTO_DRBG_HMAC) && \
> >  	!defined(CONFIG_CRYPTO_DRBG_CTR)
> > 
> > -#warning "The DRBG code is useless without compiling at least one DRBG
> > type" -#endif
> > +#define CRYPTO_DRBG_NONE_STRING "none "
> > +static int __init drbg_init(void)
> > +{
> > +	pr_warn("DRBG: no DRBG core was compiled!\n");
> > +	return -EFAULT;
> > +}
> > +#else
> 
> Wouldn't this be better handled by Kconfig so that we don't even try to
> build this unless one of the required core modules is chosen?

I tried that, but it seems that my Kconfig Foo is not too well: adding the 
DRBG cores to the depends line of CRYPTO_DRBG as indicated in the following, I 
have a circular dependency. With that circular dependency, the DRBG entries do 
not show up in make menuconfig.

menuconfig CRYTPO_DRBG
        tristate "NIST SP800-90A DRBG"
        depends on CRYPTO && (CRYPTO_DRBG_HMAC || CRYPTO_DRBG_CTR || 
CRYPTO_DRBG_HASH)
...

if CRYTPO_DRBG

config CRYPTO_DRBG_HMAC
        bool "Enable HMAC DRBG"
        default y
        depends on CRYTPO_DRBG

Do you have a working solution in mind? The goal is that once CRYPTO_DRBG is 
selected, at least one of the DRBG cores must be selected.

Thanks
Stephan
-- 
| Cui bono? |