Re: [XEN PATCH v2] automation/eclair_analysis: deviate linker symbols for Rule 18.2

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

On 2024-09-10 08:26, Jan Beulich wrote:
> On 10.09.2024 06:46, Stefano Stabellini wrote:
>> On Mon, 9 Sep 2024, Jan Beulich wrote:
>>> On 07.09.2024 15:03, Nicola Vetrini wrote:
>>>> +   * - R18.2
>>>> +     - Subtraction between pointers encapsulated by macro 
>>>> page_to_mfn
>>>> +       are safe.
>>>> +     - Tagged as `safe` for ECLAIR.
>>> 
>>> This one is a result of using frame_table[], aiui. Alternative 
>>> approaches
>>> were discussed before. Did that not lead anywhere, requiring a purely
>>> textual / configurational deviation?
>> 
>> During the last MISRA discussion we agree that this was an acceptable
>> approach. What else did you have in mind?
> 
> One was to have the linker scripts provide the symbol. I think there 
> were
> one or two more, yet I - perhaps wrongly - haven't been taking notes 
> ...
> 

One thing I'm fairly sure has been suggested for symbols that were not 
linker-defined is the following mitigation:

gcc -fsanitize=address,pointer-subtract
ASAN_OPTIONS=detect_invalid_pointer_pairs=2 ./a.out

See GCC manual Section "3.12 Program Instrumentation Options"
https://gcc.gnu.org/onlinedocs/gcc-12.1.0/gcc.pdf


>> In any case, keep in mind that
>> exploring options is a task in itself and we could use our efforts on
>> reducing the numbers of violations instead which I think is more 
>> useful.
> 
> Sure. Otoh quickest is not always best.
> 


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