Re: [PATCH 06/19] Add ioctl() argument and attribute handling utils

[Miloslav Trmac]

----- "Stefan Richter" <stef...@s5r6.in-berlin.de> wrote:
> Miloslav Trmač wrote:
> > --- /dev/null
> > +++ b/crypto/userspace/utils.c
> [...]
> > +#ifdef CONFIG_COMPAT
> > +/* max() is too clever for compile-time constants */
> > +#define CONST_MAX(A, B) ((A) > (B) ? (A) : (B))
> > +
> > +#define MAX_SESSION_INPUT_DATA_SIZE                                        
> > \
> > +   (CONST_MAX(sizeof(struct ncr_session_input_data),               \
> > +              sizeof(struct compat_ncr_session_input_data)))
> > +#define MAX_SESSION_OUTPUT_BUFFER_SIZE                                     
> > \
> > +   (CONST_MAX(sizeof(struct ncr_session_output_buffer),            \
> > +              sizeof(struct compat_ncr_session_output_buffer)))
> > +
> > +#else /* !CONFIG_COMPAT */
> > +
> > +#define MAX_SESSION_INPUT_DATA_SIZE (sizeof(struct ncr_session_input_data))
> > +#define MAX_SESSION_OUTPUT_BUFFER_SIZE                     \
> > +   (sizeof(struct ncr_session_output_buffer))
> > +
> > +#endif /* !CONFIG_COMPAT */
> 
> struct compat_xyz cannot be bigger than struct xyz, can it?
Perhaps not, but the code has been written and it's easier to keep it than to 
speculate :)  It also helps document the fact that the data format depends on 
properties of the userspace.
    Mirek
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