linux-kernel - Re: [PATCH v1 00/21] refactor Kconfig to consolidate KEXEC and CRASH options

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Date:   Thu, 15 Jun 2023 11:18:12 -0500
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Kees Cook <keescook@...omium.org>
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Subject: Re: [PATCH v1 00/21] refactor Kconfig to consolidate KEXEC and CRASH
 options



On 6/14/23 22:26, Michael Ellerman wrote:
> Eric DeVolder <eric.devolder@...cle.com> writes:
>> On 6/13/23 15:21, Kees Cook wrote:
>>> On Mon, Jun 12, 2023 at 01:27:52PM -0400, Eric DeVolder wrote:
>>>> The Kconfig is refactored to consolidate KEXEC and CRASH options from
>>>> various arch/<arch>/Kconfig files into new file kernel/Kconfig.kexec.
>>>
>>> This looks very nice!
>>>
>> Thank you Kees!
>>
>>>> [...]
>>>> - The boolean ARCH_HAS_<option> in effect allows the arch to determine
>>>>     when the feature is allowed.  Archs which don't have the feature
>>>>     simply do not provide the corresponding ARCH_HAS_<option>.
>>>>     For each arch, where there previously were KEXEC and/or CRASH
>>>>     options, these have been replaced with the corresponding boolean
>>>>     ARCH_HAS_<option>, and an appropriate def_bool statement.
>>>>
>>>>     For example, if the arch supports KEXEC_FILE, then the
>>>>     ARCH_HAS_KEXEC_FILE simply has a 'def_bool y'. This permits the
>>>>     KEXEC_FILE option to be available.
>>>>
>>>>     If the arch has a 'depends on' statement in its original coding
>>>>     of the option, then that expression becomes part of the def_bool
>>>>     expression. For example, arm64 had:
>>>>
>>>>     config KEXEC
>>>>       depends on PM_SLEEP_SMP
>>>>
>>>>     and in this solution, this converts to:
>>>>
>>>>     config ARCH_HAS_KEXEC
>>>>       def_bool PM_SLEEP_SMP
>>>>
>>>>
>>>> - In order to account for the differences in the config coding for
>>>>     the three common options, the ARCH_SUPPORTS_<option> is used.
>>>>     This options has a 'depends on <option>' statement to couple it
>>>>     to the main option, and from there can insert the differences
>>>>     from the common option and the arch original coding of that option.
>>>>
>>>>     For example, a few archs enable CRYPTO and CRYTPO_SHA256 for
>>>>     KEXEC_FILE. These require a ARCH_SUPPORTS_KEXEC_FILE and
>>>>     'select CRYPTO' and 'select CRYPTO_SHA256' statements.
>>>
>>> Naming nit: "HAS" and "SUPPORTS" feel very similar, and looking at
>>> existing configs, "ARCH_SUPPORTS_..." is already used for doing this
>>> kind of bare "bool" management. e.g. see ARCH_SUPPORTS_INT128
>>>
>>> It looks like you need to split "depends" and "select" so the options
>>> can be chosen separately from the "selectable" configs.
>>>
>>> How about naming this ARCH_SELECTS_<option>, since that's what it's
>>> there for?
>>>
>> I'm OK with this. Let's see if others agree?
> 
> Yeah please rename one or both of them. At a glance the difference
> between HAS and SUPPORTS is very non-obvious.
> 
> I like Kees' suggestion to use ARCH_SUPPORTS and ARCH_SELECTS.
> 
> cheers
Michael, ok thanks!
eric