On Tue, Feb 21, 2017 at 12:46:55PM -0800, Dave Hansen wrote:
> Let me make sure I'm grokking what you're trying to do here.
>
> On 02/20/2017 05:15 AM, Kirill A. Shutemov wrote:
> > +/* MPX cannot handle addresses above 47-bits yet. */
> > +unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len,
> > + unsigned long flags)
> > +{
> > + if (!kernel_managing_mpx_tables(current->mm))
> > + return addr;
> > + if (addr + len <= DEFAULT_MAP_WINDOW)
> > + return addr;
>
> At this point, we know MPX management is on and the hint is for memory
> above DEFAULT_MAP_WINDOW?
Right.
> > + if (flags & MAP_FIXED)
> > + return -ENOMEM;
>
> ... and if it's a MAP_FIXED request, fail it.
Yep.
> > + if (len > DEFAULT_MAP_WINDOW)
> > + return -ENOMEM;
>
> What is this case for? If addr+len wraps?
If len is too big to fit into DEFAULT_MAP_WINDOW there's no point in
resetting hint address as we know we can't satisfy it -- fail early.
>
> > + /* Look for unmap area within DEFAULT_MAP_WINDOW */
> > + return 0;
> > +}
>
> Otherwise, blow away the hint, which we know is high and needs to
> be discarded?
Right.
--
Kirill A. Shutemov
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