Re: [XEN PATCH][for-4.19 v2] xen: Add SAF deviations for MISRA C:2012 Rule 7.1

[Jan Beulich <jbeulich@xxxxxxxx>]

On 19.10.2023 13:04, Nicola Vetrini wrote:
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -85,10 +85,10 @@ conform to the directive."
>  # Series 7.
>  #
> 
> --doc_begin="Usage of the following constants is safe, since they are given 
> as-is
> -in the inflate algorithm specification and there is therefore no risk of them
> -being interpreted as decimal constants."
> --config=MC3R1.R7.1,literals={safe, 
> "^0(007|37|070|213|236|300|321|330|331|332|333|334|335|337|371)$"}
> +-doc_begin="Octal constants used as arguments to macro INSTR_ENC or MASK_EXTR
> +can be used, because they appear as is in specifications, manuals, and
> +algorithm descriptions."
> +-config=MC3R1.R7.1,reports+={safe, 
> "any_area(any_loc(any_exp(macro(^(INSTR_ENC|MASK_EXTR)$))))"}

INSTR_ENC() is a local macro in x86'es AMD SVM code. A macro of the same
name could imo be introduced without issues in, say, Arm code. The above
would then needlessly suppress findings there, aiui.

MASK_EXTR() otoh is a global macro which ise used for various purposes.
Excluding checking there is imo going too far, too.

> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -90,6 +90,12 @@ Deviations related to MISRA C:2012 Rules:
>           - __emulate_2op and __emulate_2op_nobyte
>           - read_debugreg and write_debugreg
> 
> +   * - R7.1
> +     - It is safe to use certain octal constants the way they are defined in
> +       specifications, manuals, and algorithm descriptions as arguments to
> +       macros 'INSTR_ENC' and 'MASK_EXTR'.
> +     - Tagged as `safe` for ECLAIR.

Similarly this wording is imo inappropriate, while ...

> --- a/docs/misra/safe.json
> +++ b/docs/misra/safe.json
> @@ -20,6 +20,14 @@
>          },
>          {
>              "id": "SAF-2-safe",
> +            "analyser": {
> +                "eclair": "MC3R1.R7.1"
> +            },
> +            "name": "Rule 7.1: constants defined in specifications, manuals, 
> and algorithm descriptions",
> +            "text": "It is safe to use certain octal constants the way they 
> are defined in specifications, manuals, and algorithm descriptions."
> +        },

... this reads good to me.

Jan