Re: [XEN PATCH v2 2/3] x86/uaccess: replace __{get,put}_user_bad() with STATIC_ASSERT_UNREACHABLE()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.02.2024 02:08, Stefano Stabellini wrote:
> On Tue, 6 Feb 2024, Jan Beulich wrote:
>> On 26.01.2024 11:05, Federico Serafini wrote:
>>> @@ -208,7 +205,7 @@ do {                                                    
>>>                    \
>>>      case 8:                                                                
>>> \
>>>          put_unsafe_asm(x, ptr, grd, retval, "q",  "", "ir", errret);       
>>> \
>>>          break;                                                             
>>> \
>>> -    default: __put_user_bad();                                             
>>> \
>>> +    default: STATIC_ASSERT_UNREACHABLE();                                  
>>> \
>>>      }                                                                      
>>> \
>>>      clac();                                                                
>>> \
>>>  } while ( false )
>>> @@ -227,7 +224,7 @@ do {                                                    
>>>                    \
>>>      case 2: get_unsafe_asm(x, ptr, grd, retval, "w", "=r", errret); break; 
>>> \
>>>      case 4: get_unsafe_asm(x, ptr, grd, retval, "k", "=r", errret); break; 
>>> \
>>>      case 8: get_unsafe_asm(x, ptr, grd, retval,  "", "=r", errret); break; 
>>> \
>>> -    default: __get_user_bad();                                             
>>> \
>>> +    default: STATIC_ASSERT_UNREACHABLE();                                  
>>> \
>>>      }                                                                      
>>> \
>>>      clac();                                                                
>>> \
>>>  } while ( false )
>>
>> Related to my remark on patch 1 - how is one to know the macro this was
>> invoked from, when seeing the resulting diagnostic?
> 
> I am not sure what do you mean here... we do get an error like the
> following (I added a STATIC_ASSERT_UNREACHABLE for case 4):
> 
> ./arch/x86/include/asm/uaccess.h:262: Error: static assertion failed: 
> unreachable

Right - and how do I know what _user_ of the macro actually triggered
it? ISTR suggesting to use one or more of __FILE__ / __LINE__ /
__FUNCTION__ here, for that specific purpose ...

Jan