Re: [XEN PATCH][for-next][for-4.19 v2 1/8] xen/include: add macro LOWEST_BIT

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

On 13/10/2023 01:31, Stefano Stabellini wrote:
> On Thu, 12 Oct 2023, Nicola Vetrini wrote:
>> The purpose of this macro is to encapsulate the well-known expression
>> 'x & -x', that in 2's complement architectures on unsigned integers 
>> will
>> give 2^ffs(x), where ffs(x) is the position of the lowest set bit in 
>> x.
>> 
>> A deviation for ECLAIR is also introduced.
>> 
>> Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
>> ---
>> Changes in v2:
>> - rename to LOWEST_BIT
>> ---
>>  automation/eclair_analysis/ECLAIR/deviations.ecl | 6 ++++++
>>  xen/include/xen/macros.h                         | 6 ++++--
>>  2 files changed, 10 insertions(+), 2 deletions(-)
>> 
>> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
>> b/automation/eclair_analysis/ECLAIR/deviations.ecl
>> index d8170106b449..b8e1155ee49d 100644
>> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
>> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
>> @@ -274,6 +274,12 @@ still non-negative."
>>  -config=MC3R1.R10.1,etypes+={safe, 
>> "stmt(operator(logical)||node(conditional_operator||binary_conditional_operator))", 
>> "dst_type(ebool||boolean)"}
>>  -doc_end
>> 
>> +-doc_begin="The macro LOWEST_BIT encapsulates a well-known pattern to 
>> obtain the value
>> +2^ffs(x) for unsigned integers on two's complement architectures
>> +(all the architectures supported by Xen satisfy this requirement)."
>> +-config=MC3R1.R10.1,reports+={safe, 
>> "any_area(any_loc(any_exp(macro(^LOWEST_BIT$))))"}
>> +-doc_end
> 
> Please also add the same deviation and explanation to
> docs/misra/deviations.rst. Other than that, this looks fine.
> 
> 

Ok.

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