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 15:24, Jan Beulich wrote:
> On 20.10.2023 12:33, Nicola Vetrini wrote:
> > 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.
> New MASK_EXTR() uses can appear at any time, without necessarily
> matching the justification.
>
> Jan
Sorry, but I don't understand what's your concern exactly. With the 
improvements I proposed
(hence a new patch revision) I see the following possible future 
scenarios:
1. an use of MASK_EXTR() in a file other than x86/hvm/svm/emulate.c 
appears, with no
   use of octal constants in the expansion. This won't be deviated;
2. an use of MASK_EXTR() in x86/hvm/svm/emulate.c appears, with no use 
of octal
   constants in the expansion. This won't be deviated;
3. an use of MASK_EXTR() in x86/hvm/svm/emulate.c appears, with octal
   constants in the expansion. This will be deviated;
4. an use of any other macro with an octal constant in its expansion 
won't be deviated,
   unless the configuration is suitably edited.

Does this address your concern?
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)