Re: [XEN PATCH][for-4.19 v3] xen: Add deviations for MISRA C:2012 Rule 7.1

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 25 Oct 2023, Jan Beulich wrote:
> On 24.10.2023 22:30, Stefano Stabellini wrote:
> > On Tue, 24 Oct 2023, Nicola Vetrini wrote:
> >> As specified in rules.rst, these constants can be used
> >> in the code.
> >>
> >> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> >> ---
> >> Changes in v2:
> >> - replace some SAF deviations with configurations
> >> Changes in v3:
> >> - refine configurations and justifications
> >> ---
> >>  automation/eclair_analysis/ECLAIR/deviations.ecl | 10 ++++++----
> >>  docs/misra/deviations.rst                        |  5 +++++
> >>  docs/misra/safe.json                             |  8 ++++++++
> >>  xen/arch/x86/hvm/svm/emulate.c                   |  6 +++---
> >>  xen/common/inflate.c                             |  4 ++--
> >>  5 files changed, 24 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> >> b/automation/eclair_analysis/ECLAIR/deviations.ecl
> >> index fa56e5c00a27..ea5e0eb1813f 100644
> >> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> >> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> >> @@ -85,10 +85,12 @@ 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)$"}
> >> +-doc_begin="It is safe to use certain octal constants the way they are 
> >> defined in
> >> +specifications, manuals, and algorithm descriptions."
> >> +-file_tag+={x86_svm_h, "^xen/arch/x86/hvm/svm/svm\\.h$"}
> >> +-file_tag+={x86_emulate_c, "^xen/arch/x86/hvm/svm/emulate\\.c$"}
> >> +-config=MC3R1.R7.1,reports+={safe, 
> >> "any_area(any_loc(any_exp(file(x86_svm_h)&&macro(^INSTR_ENC$))))"}
> >> +-config=MC3R1.R7.1,reports+={safe, 
> >> "any_area(text(^.*octal-ok.*$)&&any_loc(any_exp(file(x86_emulate_c)&&macro(^MASK_EXTR$))))"}
> >>  -doc_end
> >>  
> >>  -doc_begin="Violations in files that maintainers have asked to not modify 
> >> in the
> >> diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
> >> index 8511a189253b..26c6dbbc9ffe 100644
> >> --- a/docs/misra/deviations.rst
> >> +++ b/docs/misra/deviations.rst
> >> @@ -90,6 +90,11 @@ 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.
> > 
> > I think we should add that these cases have "octal-ok" as a in-code
> > comment. Everything else looks OK so this small change could be done on
> > commit.
> 
> But that needs wording carefully, as it doesn't hold across the board:
> Right now relevant MASK_EXTR() uses gain such comments, but INSTR_ENC()
> ones (deliberately) don't.

What about:

* - R7.1
  - It is safe to use certain octal constants the way they are defined
    in specifications, manuals, and algorithm descriptions. Such places
    are marked safe with a /* octal-ok */ in-code comment, or with a SAF
    comment (see safe.json).