Re: [PATCH v3 1/6] arm/mpu: Find MPU region by range

[Hari Limaye <Hari.Limaye@xxxxxxx>]

Hi Michal,

>> +int mpumap_contains_region(pr_t *table, uint8_t nr_regions, paddr_t base,
>> +                           paddr_t limit, uint8_t *index)
>> +{
>> +    ASSERT(index);
>> +    *index = INVALID_REGION_IDX;
>> +
>> +    /*
>> +     * The caller supplies a half-open interval [base, limit), i.e. limit 
>> is the
>> +     * first byte *after* the region. Require limit strictly greater than 
>> base,
>> +     * which is necessarily a non-empty region.
>> +     */
>> +    ASSERT(base < limit);
> Well, that does not guarantee a non-empty region.
> Consider passing [x, x+1). The assert will pass, even though the region is 
> empty.
> 
> ~Michal
> 

Apologies, I may well be missing something here! Please could you suggest a 
code snippet to understand your expectation here / what you would prefer the 
assert to be?

As I understand it, with a half-open interval [base, limit) as is passed to 
this function, the size is  `limit - base` and so the region [x, x+1) will have 
size 1. The empty region starting at the same address would be [x, x). But 
perhaps I am making the off-by-one error here.

Many thanks,
Hari