Re: [PATCH v1 00/10] tools: Introduce a kernel configuration checker

[Julian Braha <julianbraha@gmail.com>]

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Hi Ahmed,

Cool tool :)

On 11/6/26 09:19, Ahmed S. Darwish wrote:
> Hi,
> 
> A month ago in Prague I proposed a kernel configuration checker:
> 
>     PREEMPT_RT configuration: Best practices with kconfig-checker
>     https://youtu.be/hqnOmdpGBdQ
> 
> This series adds kconfig-checker: a Python tool that checks the kernel
> .config against a set of YAML rules and reports all issues by severity.
> 
> The series also adds:
> 
>      - a PREEMPT_RT configuration ruleset
>      - a make checkconfig target
>      - support for ruleset overlays
> 
> Example:
> 
>     $ make defconfig
>     $ ./tools/kconfig-checker/check.py check -c .config -r preempt_rt
> 
>       Configuration Issues with severity = FATAL
>       ==========================================
> 
>       * CONFIG_PREEMPT_RT is not in .config
> 
>         Rationale:
>         https://docs.kernel.org/core-api/real-time/kernel-
> configuration.html#config-preempt-rt
> 
>       Configuration Issues with severity = HIGH
>       =========================================
> 
>       * CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is unset
> 
>         Rationale:
>         https://docs.kernel.org/core-api/real-time/kernel-
> configuration.html#config-cpu-freq-default-gov-performance
> 
>       * Below options are set:
> 
>         CONFIG_SLUB_DEBUG
> 
>         Rationale:
>         https://docs.kernel.org/core-api/real-time/kernel-
> configuration.html#kernel-debug-options
> 
>       Configuration Issues with severity = MEDIUM
>       ===========================================
> 
>       * Below options are set:
> 
>         CONFIG_CPU_FREQ_GOV_USERSPACE
>         CONFIG_CPU_FREQ_GOV_ONDEMAND
> 
>         Rationale:
>         https://docs.kernel.org/core-api/real-time/kernel-
> configuration.html#non-performance-cpu-frequency-governors
> 
>       ### ...
>       ### More output
>       ### ...
> 
> The same check can be run through make:
> 
>     $ make RULES=preempt_rt checkconfig
> 
> If no ruleset is specified, the target prints the available rulesets:
> 
>     $ make checkconfig
>       Usage: make RULES=<profile> [OVERLAY=<overlay>] checkconfig
>       Available RULES: preempt_rt
> 
> The overlay mechanism allows distributions, CI systems, and Board Support

On the topic of distributions, this seems *a lot* like Canonical's
Annotations [1], albeit yours uses YAML and supports matching option
names with regex. As you say about PREEMPT_RT configuration not being
"one-size-fits-all", similarly there are 100+ Ubuntu kernels that need
to adhere to a configuration "policy".

So this seems to be a real problem that others are having.

> Packages to apply additional policy or override existing mainline rules.
> 
> For example:
> 
>     $ ./tools/kconfig-checker/check.py check	\
>           -c path/to/.config			\
>           -r preempt_rt				\
>           -o path/to/overlay.yml
> 
> or:
> 
>     $ make RULES=preempt_rt OVERLAY=path/to/overlay.yml checkconfig
> 
> Patch 09/10 documents the overlay format and gives an example use case.
> 
> My goal is to get this into the kernel and have Debian's PREEMPT_RT kernel
> packaging to use it.  I'd also like systemd to use it: its README lists 60
> kernel CONFIG_* symbols with different requirements severity.
> 
> Thank you!
> Ahmed
> 
> 8<-----
> 
> Ahmed S. Darwish (10):
>   kconfig-checker: Add schema for rule files
>   kconfig-checker: Introduce PREEMPT_RT configuration rules
>   kconfig-checker: Add the configuration checker code
>   kconfig: Introduce checkconfig target
>   Documentation: Describe kconfig-checker usage and design
>   kconfig-checker: Split schema to support component reuse
>   kconfig-checker: Introduce overlays schema
>   kconfig-checker: Add support for rule overlays
>   Documentation: Describe kconfig-checker overlays
>   kconfig: Introduce OVERLAY= for make checkconfig
> 
>  Documentation/admin-guide/README.rst          |  29 +
>  .../real-time/kernel-configuration.rst        |   3 +
>  Documentation/tools/index.rst                 |   1 +
>  Documentation/tools/kconfig_checker.rst       | 101 +++
>  scripts/kconfig/Makefile                      |  25 +
>  tools/kconfig-checker/check.py                | 686 ++++++++++++++++++
>  tools/kconfig-checker/rules/preempt_rt.yml    | 169 +++++
>  tools/kconfig-checker/schemas/base.yml        | 114 +++
>  tools/kconfig-checker/schemas/overlay.yml     |  28 +
>  tools/kconfig-checker/schemas/rules.yml       |  20 +
>  10 files changed, 1176 insertions(+)
>  
>  create mode 100644 Documentation/tools/kconfig_checker.rst
>  create mode 100755 tools/kconfig-checker/check.py
>  create mode 100644 tools/kconfig-checker/rules/preempt_rt.yml
>  create mode 100644 tools/kconfig-checker/schemas/base.yml
>  create mode 100644 tools/kconfig-checker/schemas/overlay.yml
>  create mode 100644 tools/kconfig-checker/schemas/rules.yml
> 
> base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
> -- 2.56.0
> 

I think the name will cause confusion.

We already have some "kconfig checkers" in-tree, like
scripts/kconfig-sym-check.pl

But actually, your tool is quite unrelated, because that one checks
'Kconfig' source files, while yours checks the user's '.config' file.

This has already caused some confusion in the past, for example in this
thread [2], someone misunderstood which one 'kconfig-sym-check'
actually checks.

In addition to .config vs Kconfig, the name is similar to
'kconfig-sym-check', but is not as descriptive about *what kind* of
checks it performs.

[1] https://lists.ubuntu.com/archives/kernel-team/2023-June/140230.html
[2] https://lore.kernel.org/all/ajo4DVWoSaEZtBDa@google.com/

- Julian Braha

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