On Thu, Mar 19, 2020 at 03:16:03PM +0100, Christophe Leroy wrote:
>
>
> Le 19/03/2020 à 14:35, Andy Shevchenko a écrit :
> > On Thu, Mar 19, 2020 at 1:54 PM Michal Suchanek <msucha...@suse.de> wrote:
> > >
> > > Merge the 32bit and 64bit version.
> > >
> > > Halve the check constants on 32bit.
> > >
> > > Use STACK_TOP since it is defined.
> > >
> > > Passing is_64 is now redundant since is_32bit_task() is used to
> > > determine which callchain variant should be used. Use STACK_TOP and
> > > is_32bit_task() directly.
> > >
> > > This removes a page from the valid 32bit area on 64bit:
> > > #define TASK_SIZE_USER32 (0x0000000100000000UL - (1 * PAGE_SIZE))
> > > #define STACK_TOP_USER32 TASK_SIZE_USER32
> >
> > ...
> >
> > > +static inline int valid_user_sp(unsigned long sp)
> > > +{
> > > + bool is_64 = !is_32bit_task();
> > > +
> > > + if (!sp || (sp & (is_64 ? 7 : 3)) || sp > STACK_TOP - (is_64 ? 32
> > > : 16))
> > > + return 0;
> > > + return 1;
> > > +}
> >
> > Other possibility:
>
> I prefer this one.
>
> >
> > unsigned long align = is_32bit_task() ? 3 : 7;
>
> I would call it mask instead of align
>
> > unsigned long top = STACK_TOP - (is_32bit_task() ? 16 : 32);
> >
> > return !(!sp || (sp & align) || sp > top);
And we can avoid the inversion here as well as in !valid_user_sp(sp) by
changing to invalid_user_sp.
Thanks
Michal
