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

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 20/10/2023 08:38, Jan Beulich wrote:
> On 19.10.2023 18:34, Nicola Vetrini wrote:
> > On 19/10/2023 17:57, Jan Beulich wrote:
> > > 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.
> > I should have thought about it; I can simply enforce the deviation to
> > additionally match
> > only a specific file for each of the macros.
> That'll work for INSTR_ENC(), but not for MASK_EXTR().
Why? What I'm deviating is reports due to octal constants used in 
expressions
that contain MASK_EXTR in their expansion if and only if these are 
located in the
file svm.h.
No extra octal constant will match all these constraints.

> > > > --- 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 ...
> > I tried to be a bit more specific about what is actually being 
> > deviated,
> > on the assumption
> > that the maintainers and contributors would find it more useful than
> > parsing ecl files, but
> > if you prefer it to be more general, no problem.
> Just dropping everything after the last comma would deal with my 
> concern.
> Jan
Ok

--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)