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SubjectRe: [PATCH -mmotm] ecryptfs: depends on CRYPTO
On 09/28/2009 07:20 PM, Randy Dunlap wrote:
> On Mon, 28 Sep 2009 19:10:00 -0500 Tyler Hicks wrote:
>
>> On 09/28/2009 03:34 PM, Randy Dunlap wrote:
>>> From: Randy Dunlap <randy.dunlap@oracle.com>
>>>
>>> ecryptfs uses crypto APIs so it should depend on CRYPTO.
>>> Otherwise many build errors occur. [63 lines not pasted]
>>>
>>> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
>>> ---
>>> fs/ecryptfs/Kconfig | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> --- mmotm-2009-0925-1435.orig/fs/ecryptfs/Kconfig
>>> +++ mmotm-2009-0925-1435/fs/ecryptfs/Kconfig
>>> @@ -1,6 +1,6 @@
>>> config ECRYPT_FS
>>> tristate "eCrypt filesystem layer support (EXPERIMENTAL)"
>>> - depends on EXPERIMENTAL && KEYS && NET
>>> + depends on EXPERIMENTAL && KEYS && NET && CRYPTO
>>> select CRYPTO_ECB
>>> select CRYPTO_CBC
>>> help
>>
>> Hi Randy - Thanks for the patch! Unfortunately, I think it defeats what
>> Dave Hansen was wanting to do with commit
>> 382684984e93039a3bbd83b04d341b0ceb831519.
>>
>> When I pulled that patch in, I was under the assumption that the select
>> would also select all necessary dependencies. According to
>> Documentation/kbuild/kconfig-language.txt, that's not the case:
>>
>> select should be used with care. select will force
>> a symbol to a value without visiting the dependencies.
>> By abusing select you are able to select a symbol FOO even
>> if FOO depends on BAR that is not set.
>>
>> Maybe we should do it how other folks are tackling this problem and
>> select CRYPTO, along with CRYPTO_ECB and CRYPTO_CBC. While we're at it,
>> we should probably throw in CRYPTO_AES (aes-128 is the default cipher,
>> but the cipher is configurable at mount so it might be too obtrusive for
>> us to select it) and CRYPTO_MD5 (our default hash alg, not currently
>> configurable). Also, we don't depend on NET anymore because our netlink
>> interface is no longer around. It may not hurt to select KEYS, rather
>> than depend on it. Does all of this sound sane to you?
>
> It selects too much stuff. "select" should not be used to enable
> a full subsystem (that's my general rule, not in kconfig-language.txt).
> What kconfig-language.txt says that applies here is just after your
> quoted text:
>
> In general use select only for non-visible symbols
> (no prompts anywhere) and for symbols with no dependencies.
> That will limit the usefulness but on the other hand avoid
> the illegal configurations all over.
>
> CRYPTO does not fit that.
>
> One of the big problems with selecting kconfig symbols (like subsystem
> ones) is that it makes it difficult to disable that symbol, which some
> of us often want to do.
>
>
> ---
> ~Randy

eCryptfs wouldn't be the first to select CRYPTO:

$ grep -r "select CRYPTO$" --include=Kconfig . | wc -l
26
But after trying to deselect CRYPTO with one of my custom configs, I
realized that you are right. :) Depending on CRYPTO and then selecting
the proper CRYPTO_* symbols is the way to go.

Applied to
git://git.kernel.org/pub/scm/linux/kernel/git/ecryptfs/ecryptfs-2.6.git#next

Thanks again!

Tyler


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