Re: [PATCH v2] misra: add deviation for MISRA C Rule R11.8.

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 2024-12-19 09:49, Jan Beulich wrote:
> On 18.12.2024 15:25, Alessandro Zucchelli wrote:
> > Rule 11.8 states as following: "A cast shall not remove any `const' or
> > `volatile' qualification from the type pointed to by a pointer".
> >
> > Function `__hvm_copy' in `xen/arch/x86/hvm/hvm.c' is a double-use
> > function, where the parameter needs to not be const because it can be
> > set for write or not. As it was decided a new const-only function will
> > lead to more developer confusion than it's worth, this violation is
> > addressed by deviating the function.
> > All cases of casting away const-ness are accompanied with a comment
> > explaining why it is safe given the other flags passed in; such 
> > comment is used
> > by the deviation in order to match the appropriate function call.
> >
> > No functional change.
> >
> > Signed-off-by: Alessandro Zucchelli <alessandro.zucchelli@xxxxxxxxxxx>
> > ---
> > --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> > +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> > @@ -393,6 +393,12 @@ Fixing this violation would require to increase 
> > code complexity and lower readab
> >  
> > -config=MC3R1.R11.8,reports+={safe,"any_area(any_loc(any_exp(macro(^container_of$))))"}
> >  -doc_end
> >
> > +-doc_begin="Function __hvm_copy in xen/arch/x86/hvm/hvm.c is a 
> > double-use
> > +function, where the parameter needs to not be const because it can be 
> > set for
> > +write or not"
> > +-config=MC3A2.R11.8,reports+={safe,"any_area(any_loc(text(^.*__hvm_copy.*HVMCOPY_to_guest 
> > doesn't modify.*$)))"}
> This is probably good enough for now, yet still: It constrains 
> re-formatting
> that we may want to do on such function calls. Personally I'd consider 
> it
> entirely unexpected if I ended up (re)introducing a violation just by 
> re-
> formatting one of those function calls to
>
>     return __hvm_copy(
>                (void *)buf /* HVMCOPY_to_guest doesn't modify */,
>                addr, size, current, HVMCOPY_to_guest | HVMCOPY_linear,
>                PFEC_page_present | PFEC_write_access | pfec, pfinfo);
>
> yet aiui the pattern above would have this effect (I don't think .* 
> matches
> newlines; instead I expect such regex-es to be applied to individual 
> lines
> only). Thoughts anyone?
Hi Jan,

we can simply drop the "__hvm_copy" part from the regex. The regex can 
be made multiline, or alternatively we can apply the search to a range 
of lines. By default it searches on the same location mentioned by the 
report, which in this case is the line containing __hvm_copy (range 
defaults to 0..0). However I would leave it either as is or without the 
__hvm_copy prefix.
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)