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

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 23/10/2023 10:44, Nicola Vetrini wrote:
> > > > > 3. an use of MASK_EXTR() in x86/hvm/svm/emulate.c appears, with 
> > > > > octal
> > > > >     constants in the expansion. This will be deviated;
> > > > This is what I'm concerned of: How do you know up front whether such
> > > > new
> > > > uses want deviating?
> > > I understand you concern now. I can argue that all the macros in that
> > > table have indeed
> > > an octal constant in their definition (0 is explicitly allowed by
> > > MISRA).
> > > This is also specified in the comment above the INSTR_ENC macro
> > > definition, therefore any
> > > new addition should have an octal the second argument to INSTR_ENC.
> > Right, and I previously indicated I agree as far as INSTR_ENC() goes.
> > What we appear to continue to disagree about is MASK_EXTR().
> Yeah, sorry. What about
>
> if ( modrm_mod       == MASK_EXTR(instr_modrm, 0300) && /* octal-ok */
>      (modrm_reg & 7) == MASK_EXTR(instr_modrm, 0070) && /* octal-ok */
>      (modrm_rm  & 7) == MASK_EXTR(instr_modrm, 0007) )  /* octal-ok */
>             return emul_len;
>
> It does not really fit in the SAF framework, because the deviation is
> still done with a
> configuration, but at least it gives some clear indication on how to
> introduce an octal
> constant in this file.
What I mean is that matching /* octal-ok */ is an additional constraint 
for the
deviation to be applied in that file.

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