Re: [PATCH] misra: add deviation for MISRA C Rule 18.3

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

On 2025-08-20 14:44, Dmytro Prokopchuk1 wrote:
> MISRA C Rule 18.3 states:"The relational operators >, >=, < and <= 
> shall
> not be applied to objects of pointer type except where they point into
> the same object."
> 
> Comparisons in the 'find_text_region()' function are safe because 
> linker
> symbols '_stext' and '_etext' represent fixed virtual addresses within
> the same '.text' region, and the function 'addr' argument is explicitly
> compared to known valid memory bounds ('text_start' and 'text_end')
> derived from these linker symbols:
>     if ( (void *)addr >= iter->text_start &&
>          (void *)addr <  iter->text_end )
> 
> Configure Eclair to suppress violation reports occured in the function
> 'find_text_region()'. Update 'deviations.rst' file accordingly.
> No functional changes.
> 
> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@epam.com>

Reviewed-by: Nicola Vetrini <nicola.vetrini@bugseng.com>

with two NITs below:

> ---
> Test CI pipeline:
> https://gitlab.com/xen-project/people/dimaprkp4k/xen/-/pipelines/1993673043
> ---
>  automation/eclair_analysis/ECLAIR/deviations.ecl | 6 ++++++
>  docs/misra/deviations.rst                        | 8 ++++++++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> b/automation/eclair_analysis/ECLAIR/deviations.ecl
> index 7f3fd35a33..32b596c9da 100644
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -590,6 +590,12 @@ C99 Undefined Behaviour 45: Pointers that do not 
> point into, or just beyond, the
>  -config=MC3A2.R18.2,reports+={safe, 
> "any_area(any_loc(any_exp(macro(^page_to_mfn$))))"}
>  -doc_end
> 
> +-doc_begin="Comparisons in the 'find_text_region()' function are safe 
> because linker symbols '_stext' and '_etext' represent fixed
> +virtual addresses within the same '.text' region, and the function 
> 'addr' argument is explicitly compared to known valid memory
> +bounds ('text_start' and 'text_end') derived from these linker 
> symbols."

Maybe ['text_start', 'text_end') here and below to emphasize that this 
is a range?

> +-config=MC3A2.R18.3,reports+={safe, 
> "any_area(any_loc(file(^xen/common/virtual_region\\.c$))&&context(name(find_text_region)))"}
> +-doc_end
> +
>  -doc_begin="Flexible array members are deliberately used and XEN 
> developers are aware of the dangers related to them:
>  unexpected result when the structure is given as argument to a 
> sizeof() operator and the truncation in assignment between structures."
>  -config=MC3A2.R18.7,reports+={deliberate, "any()"}
> diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
> index 2119066531..a726fb22a8 100644
> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -586,6 +586,14 @@ Deviations related to MISRA C:2012 Rules:
>         are safe.
>       - Tagged as `safe` for ECLAIR.
> 
> +   * - R18.3
> +     - Comparisons in the 'find_text_region()' function are safe 
> because
> +       linker symbols '_stext' and '_etext' represent fixed virtual
> +       addresses within the same '.text' region, and the function 
> 'addr'

s/function 'addr' argument/function parameter 'addr'/

> +       argument is explicitly compared to known valid memory bounds
> +       ('text_start' and 'text_end') derived from these linker 
> symbols.
> +     - Tagged as `safe` for ECLAIR.
> +
>     * - R20.4
>       - The override of the keyword \"inline\" in xen/compiler.h is 
> present so
>         that section contents checks pass when the compiler chooses not 
> to

-- 
Nicola Vetrini, B.Sc.
Software Engineer
BUGSENG (https://bugseng.com)
LinkedIn: https://www.linkedin.com/in/nicola-vetrini-a42471253