Re: [crash] Re: Latest brk patchset

[Jeremy Fitzhardinge]

H. Peter Anvin wrote:
> Jeremy Fitzhardinge wrote:
> > Yinghai Lu wrote:
> > > > -INIT_MAP_SIZE = (PAGE_TABLE_SIZE + ALLOCATOR_SLOP) * PAGE_SIZE_asm
> > > > -RESERVE_BRK(pagetables, INIT_MAP_SIZE)
> > > > +/* Enough space to fit pagetables for the low memory linear map */
> > > > +MAPPING_BEYOND_END = (PAGE_TABLE_SIZE(1 << (32 - PAGE_SHIFT)) * 
> > > > PAGE_SIZE)
> > > >     
> > >
> > > that is for 4g?
> > >   
> >
> > Yes, I suppose it only needs to be 1G.  But it doesn't make much 
> > difference in practice.
>
> A tighter bound would probably be nice, if nothing else because 
> tighter bounds tend to catch more bugs.

Well, its a bit more complex than that; we'd need to make it conditional 
on the user/kernel split, which seems all a bit fiddly.  I guess it 
could be something like:

MAPPING_BEYOND_END = PAGE_TABLE_SIZE((1<<(32-PAGE_SHIFT)) - (PAGE_OFFSET / PAGE_SIZE)) * PAGE_SIZE

   J
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/