[v4] Fix to avoid IS_ERR_VALUE and IS_ERR abuses on 64bit systems.

[Arnd Bergmann]

On Monday, August 1, 2016 4:55:43 PM CEST Scott Wood wrote:
> On 08/01/2016 02:02 AM, Arnd Bergmann wrote:

> >> diff --git a/include/linux/err.h b/include/linux/err.h
> >> index 1e35588..c2a2789 100644
> >> --- a/include/linux/err.h
> >> +++ b/include/linux/err.h
> >> @@ -18,7 +18,17 @@
> >>  
> >>  #ifndef __ASSEMBLY__
> >>  
> >> -#define IS_ERR_VALUE(x) unlikely((unsigned long)(void *)(x) >= (unsigned long)-MAX_ERRNO)
> >> +#define IS_ERR_VALUE(x) unlikely(is_error_check(x))
> >> +
> >> +static inline int is_error_check(unsigned long error)
> > 
> > Please leave the existing macro alone. I think you were looking for
> > something specific to the return code of qe_muram_alloc() function,
> > so please add a helper in that subsystem if you need it, not in
> > the generic header files.
> 
> qe_muram_alloc (a.k.a. cpm_muram_alloc) returns unsigned long.  The
> problem is certain callers that store the return value in a u32.  Why
> not just fix those callers to store it in unsigned long (at least until
> error checking is done)?
> 

Yes, that would also address another problem with code like

         kfree((void *)ugeth->tx_bd_ring_offset[i]);

which is not 64-bit safe when tx_bd_ring_offset is a 32-bit value
that also holds the return value of qe_muram_alloc.

	Arnd