Re: [XEN PATCH] xen: rework deviation to address varargs MISRA violations

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 31/12/2025 11:22 am, Nicola Vetrini wrote:
> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> b/automation/eclair_analysis/ECLAIR/deviations.ecl
> index 219ba6993b90..7dee4a488d45 100644
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -570,13 +570,11 @@ safe."
>  # Series 17.
>  #
>  
> --doc_begin="printf()-like functions are allowed to use the variadic features 
> provided by stdarg.h."
> --config=MC3A2.R17.1,reports+={deliberate,"any_area(^.*va_list.*$&&context(ancestor_or_self(^.*printk\\(.*\\)$)))"}
> --config=MC3A2.R17.1,reports+={deliberate,"any_area(^.*va_list.*$&&context(ancestor_or_self(^.*printf\\(.*\\)$)))"}
> --config=MC3A2.R17.1,reports+={deliberate,"any_area(^.*va_list.*$&&context(ancestor_or_self(name(panic)&&kind(function))))"}
> --config=MC3A2.R17.1,reports+={deliberate,"any_area(^.*va_list.*$&&context(ancestor_or_self(name(elf_call_log_callback)&&kind(function))))"}
> --config=MC3A2.R17.1,reports+={deliberate,"any_area(^.*va_list.*$&&context(ancestor_or_self(name(vprintk_common)&&kind(function))))"}
> --config=MC3A2.R17.1,macros+={hide , "^va_(arg|start|copy|end)$"}
> +-doc_begin="printf()-like or scanf()-like functions are allowed to use the 
> variadic features provided by stdarg.h,
> +provided that they are declared using the `format' attribute."
> +-decl_selector+={format_attr, "property(format)"}
> +-config=MC3A2.R17.1,reports+={deliberate, 
> "any_area(^.*va_list.*$&&context(ancestor_or_self(format_attr)))"}
> +-config=MC3A2.R17.1,macros+={deliberate , "^va_(arg|start|copy|end)$"}
>  -doc_end
>  
>  -doc_begin="Not using the return value of a function does not endanger 
> safety if it coincides with an actual argument."
> diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
> index b3431ef24e26..584907b048ec 100644
> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -570,8 +570,8 @@ Deviations related to MISRA C:2012 Rules:
>       - Tagged as `deliberate` for ECLAIR.
>  
>     * - R17.1
> -     - printf()-like functions  are allowed to use the variadic features 
> provided
> -       by `stdarg.h`.
> +     - printf()-like or scanf()-like functions are allowed to use the 
> variadic
> +       features provided by `stdarg.h`.
>       - Tagged as `deliberate` for ECLAIR.

Much nicer.  But don't we want to repeat the part about
__attribute__((format(...))) here?  After all, that is the justification
of why it's safer than nothing.

~Andrew