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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/01/2026 11:53 am, Nicola Vetrini wrote:
> On 2026-01-02 10:42, Andrew Cooper wrote:
>> 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.
>>
>
> Ok, that would be more accurate for sure. I didn't do that to preserve
> the original intention of the deviation, but they are practically
> equivalent with the current codebase, so changing the text makes
> little difference. I'll tweak that.

I can adjust on commit, if you're happy?  Everything else is fine AFAICT.

In fact, this fixes the x86_64-allcode complaint for
vmcoreinfo_append_str() which is already annotated, and
debugtrace_printk() too (not yet enabled in *-allcode).

~Andrew