linux-kernel - Re: [PATCH v1 03/12] crypto: qat - address recursive dependency when fw signing is enabled

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Date:	Thu, 07 May 2015 20:06:35 +0200
From:	Paul Bolle <pebolle@...cali.nl>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	rusty@...tcorp.com.au, dhowells@...hat.com, ming.lei@...onical.com,
	seth.forshee@...onical.com, kyle@...nel.org,
	akpm@...ux-foundation.org, gregkh@...uxfoundation.org,
	keescook@...omium.org, casey@...aufler-ca.com, tiwai@...e.de,
	mjg59@...f.ucam.org, wireless-regdb@...ts.infradead.org,
	linux-wireless@...r.kernel.org, jlee@...e.com,
	linux-kernel@...r.kernel.org,
	"Luis R. Rodriguez" <mcgrof@...e.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Tadeusz Struk <tadeusz.struk@...el.com>,
	John Griffin <john.griffin@...el.com>
Subject: Re: [PATCH v1 03/12] crypto: qat - address recursive dependency
 when fw signing is enabled

On Thu, 2015-05-07 at 10:42 +0200, Paul Bolle wrote:
> On Wed, 2015-05-06 at 11:33 +0800, Herbert Xu wrote:
> > On Tue, May 05, 2015 at 05:44:21PM -0700, Luis R. Rodriguez wrote:
> > > From: "Luis R. Rodriguez" <mcgrof@...e.com>
> > > 
> > > We're going to add firmware module signing support, but when we do
> > > this we end up with the following recursive dependency. Fix this by
> > > just depending on FW_LOADER, which is typically always enabled
> > > anyway.
> > > 
> > > mcgrof@...on ~/linux-next (git::master)$ make allnoconfig
> > > scripts/kconfig/conf  --allnoconfig Kconfig
> > > crypto/Kconfig:15:error: recursive dependency detected!
> > > crypto/Kconfig:15:      symbol CRYPTO is selected by SYSDATA_SIG
> > > init/Kconfig:1880:      symbol SYSDATA_SIG is selected by FIRMWARE_SIG
> > > drivers/base/Kconfig:88:        symbol FIRMWARE_SIG depends on FW_LOADER
> > > drivers/base/Kconfig:80:        symbol FW_LOADER is selected by CRYPTO_DEV_QAT
> > > drivers/crypto/qat/Kconfig:1:   symbol CRYPTO_DEV_QAT is selected by CRYPTO_DEV_QAT_DH895xCC
> > > drivers/crypto/qat/Kconfig:13:  symbol CRYPTO_DEV_QAT_DH895xCC depends on CRYPTO
> > 
> > This doesn't look like a real cycle to me so perhaps we can fix
> > kbuild to understand this?
> 
> (Dependency circles involving selects still hurt my brain.)
> 
> Perhaps Luis should have another look at 02/12. See that patch adds this
> Kconfig entry to init/Kconfig:
>     config SYSDATA_SIG
> 	def_bool y
> 	select SYSTEM_TRUSTED_KEYRING
> 	select KEYS
> 	select CRYPTO
> 	select ASYMMETRIC_KEY_TYPE
> 	select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
> 	select PUBLIC_KEY_ALGO_RSA
> 	select ASN1
> 	select OID_REGISTRY
> 	select X509_CERTIFICATE_PARSER
> 
> As far as I can see this is not enclosed in anything that adds any
> dependencies. So that basically means that SYSDATA_SIG will always be
> set, for all architectures (because I think all arches source
> init/Kconfig). That should make it a pretty pointless symbol (except for
> the fact that it does trigger all those selects).
> 
> The same patch also adds
> 	select SYSDATA_SIG
> 
> to the entry for MODULE_SIG. But to me that looks like a nop, because
> SYSDATA_SIG will be set anyhow. So, but this is just I guess, the
> problem might go away if
> 	def_bool y
> 
> is changed to just
> 	bool

No, it doesn't. But the change I propose still makes sense, anyway.

> (Note that I haven't actually tested anything here, and it wouldn't be
> the first time my reasoning about Kconfig patches is completely off.)

Hear, hear!

> And, whatever the value of my analysis, adding a Kconfig problem in
> 02/12 just to fix it in 03/12 is a bit silly. I think the patches should
> be squashed if the problem can't be solved any other way.

It seems the circular dependency warning is triggered by 5/12.

And, having now fiddled a bit with this series, I think the approach
taken in this patch might actually be preferable treewide.

See, FW_LOADER is 'y' unless EXPERT is set and one goes to the trouble
of setting FW_LOADER to 'n'. So in the 100+ places where FW_LOADER is
selected, that is done for, almost always, no immediate benefit.
Changing those places to use
    depends on FW_LOADER

should have no effect, I think. Except for the EXPERT people not wanting
FW_LOADER. But that would be putting the burden where it belongs, I'd
say.

Am I missing something here?


Paul Bolle

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