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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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