Re: [XEN PATCH 2/4] automation/eclair: add deviations and call properties.

[Simone Ballarin <simone.ballarin@xxxxxxxxxxx>]

On 19/10/23 02:57, Stefano Stabellini wrote:
> On Wed, 18 Oct 2023, Simone Ballarin wrote:
> > Deviate violations of MISRA C:2012 Rule 13.1 caused by
> > functions vcpu_runnable and __bad_atomic_size. These functions
> > contain side-effects such as debugging logs, assertions and
> > failures that cannot cause unexpected behaviors.
> >
> > Add "noeffect" call property to functions read_u.*_atomic and
> > get_cycles.
> >
> > Signed-off-by: Simone Ballarin <simone.ballarin@xxxxxxxxxxx>
> Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
> However one comment below
>
>
> > ---
> >   .../eclair_analysis/ECLAIR/call_properties.ecl      | 10 ++++++++++
> >   automation/eclair_analysis/ECLAIR/deviations.ecl    | 13 +++++++++++++
> >   docs/misra/deviations.rst                           | 11 +++++++++++
> >   3 files changed, 34 insertions(+)
> >
> > diff --git a/automation/eclair_analysis/ECLAIR/call_properties.ecl 
> > b/automation/eclair_analysis/ECLAIR/call_properties.ecl
> > index 3f7794bf8b..f410a6aa58 100644
> > --- a/automation/eclair_analysis/ECLAIR/call_properties.ecl
> > +++ b/automation/eclair_analysis/ECLAIR/call_properties.ecl
> > @@ -104,3 +104,13 @@ Furthermore, their uses do initialize the involved 
> > variables as needed by futher
> >   -call_properties+={"macro(^(__)?(raw_)?copy_from_(paddr|guest|compat)(_offset)?$)", 
> > {"pointee_write(1=always)", "pointee_read(1=never)", "taken()"}}
> >   -call_properties+={"macro(^(__)?copy_to_(guest|compat)(_offset)?$)", {"pointee_write(2=always)", 
> > "pointee_read(2=never)", "taken()"}}
> >   -doc_end
> > +
> > +-doc_begin="Functions generated by build_atomic_read cannot be considered pure
> > +since the input pointer is volatile."
> > +-call_properties+={"^read_u(8|16|32|64|int)_atomic.*$", {"noeffect"}}
> > +-doc_end
> > +
> > +-doc_begin="get_cycles does not perform visible side-effects "
> > +-call_property+={"name(get_cycles)", {"noeffect"}}
> > +-doc_end
> > +
> > diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> > b/automation/eclair_analysis/ECLAIR/deviations.ecl
> > index fa56e5c00a..b80ccea7bc 100644
> > --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> > +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> > @@ -233,6 +233,19 @@ this."
> >   -config=MC3R1.R10.1,etypes+={safe,
> >     "stmt(operator(and||or||xor||not||and_assign||or_assign||xor_assign))",
> >     "any()"}
> > +#
> > +# Series 13.
> > +#
> > +
> > +-doc_begin="Function __bad_atomic_size is intended to generate a linkage error
> > +if invoked. Calling it in intentionally unreachable switch cases is safe even
> > +in a initializer list."
> > +-config=MC3R1.R13.1,reports+={safe, "first_area(^.*__bad_atomic_size.*$)"}
> > +-doc_end
> > +
> > +-doc_begin="Function vcpu_runnable contains pragmas and other side-effects for
> > +debugging purposes, their invocation is safe even in a initializer list."
> > +-config=MC3R1.R13.1,reports+={safe, "first_area(^.*vcpu_runnable.*$)"}
> >   -doc_end
> >   
> >   -doc_begin="See Section \"4.5 Integers\" of \"GCC_MANUAL\", where it says that
> > diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
> > index 8511a18925..2fcdb8da58 100644
> > --- a/docs/misra/deviations.rst
> > +++ b/docs/misra/deviations.rst
> > @@ -192,6 +192,17 @@ Deviations related to MISRA C:2012 Rules:
> >          See automation/eclair_analysis/deviations.ecl for the full explanation.
> >        - Tagged as `safe` for ECLAIR.
> >   
> > +   * - R13.1
> > +     - Function __bad_atomic_size is intended to generate a linkage error if
> > +       invoked. Calling it in intentionally unreachable switch cases is
> > +       safe even in a initializer list.
> > +     - Tagged as `safe` for ECLAIR.
> > +
> > +   * - R13.1
> > +     - Function vcpu_runnable contains pragmas and other side-effects for
> > +       debugging purposes, their invocation is safe even in a initializer list.
> > +     - Tagged as `safe` for ECLAIR.
>
> Would it be possible to use SAF instead? If not, this is fine.
Yes, but I do not suggest using SAF comments in these cases.
The SAF should be placed before every non-compliant invocation and not 
only in the declaration, this could cause a lot of SAF comments instead
of a simple deviation.

--
Simone Ballarin, M.Sc.

Field Application Engineer, BUGSENG (https://bugseng.com)