Re: [XEN PATCH 2/4] x86/emulate: move a variable declaration to address MISRA C:2012 Rule 5.3

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

On 27/07/23 17:06, Jan Beulich wrote:
> On 27.07.2023 12:48, Nicola Vetrini wrote:
>> --- a/xen/arch/x86/hvm/emulate.c
>> +++ b/xen/arch/x86/hvm/emulate.c
>> @@ -2024,15 +2024,15 @@ static int cf_check hvmemul_rep_stos(
>>   
>>       switch ( p2mt )
>>       {
>> -        unsigned long bytes;
>>           char *buf;
>>   
>>       default:
>>           /* Allocate temporary buffer. */
>>           for ( ; ; )
>>           {
>> -            bytes = *reps * bytes_per_rep;
>> -            buf = xmalloc_bytes(bytes);
>> +            unsigned long bytes_tmp;
>> +            bytes_tmp = *reps * bytes_per_rep;
>> +            buf = xmalloc_bytes(bytes_tmp);
>>               if ( buf || *reps <= 1 )
>>                   break;
>>               *reps >>= 1;
> 
> This wants dealing with differently - the outer scope variable is unused
> (only written to) afaics. Eliminating it will, aiui, address another
> violation at the same time. And then the same in hvmemul_rep_movs(), just
> that there the variable itself needs to survive. I guess I'll make a
> patch ...
> 
> Jan

Wouldn't this code at line ~2068 be possibly affected by writing to 
bytes, if the outer variable is used?

/* Adjust address for reverse store. */
if ( df )
   gpa -= bytes - bytes_per_rep;

rc = hvm_copy_to_guest_phys(gpa, buf, bytes, curr);

You're right about the other violation (R2.1)

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