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

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Message-ID: <202306131314.EFA558B7@keescook>
Date:   Tue, 13 Jun 2023 13:21:05 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Eric DeVolder <eric.devolder@...cle.com>
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Subject: Re: [PATCH v1 00/21] refactor Kconfig to consolidate KEXEC and CRASH
 options

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!

> [...]
> - 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?

-Kees

-- 
Kees Cook