Re: [PATCH RESEND 6/8] parisc: Use mmap_base, not mmap_legacy_base, as low_limit for bottom-up mmap

[Alex Ghiti]

On 6/25/19 10:09 AM, Helge Deller wrote:
> On 20.06.19 07:03, Alexandre Ghiti wrote:
> > Bottom-up mmap scheme is used twice:
> >
> > - for legacy mode, in which mmap_legacy_base and mmap_base are equal.
> >
> > - in case of mmap failure in top-down mode, where there is no need to go
> > through the whole address space again for the bottom-up fallback: the goal
> > of this fallback is to find, as a last resort, space between the top-down
> > mmap base and the stack, which is the only place not covered by the
> > top-down mmap.
> >
> > Then this commit removes the usage of mmap_legacy_base field from parisc
> > code.
> >
> > Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
> Boot-tested on parisc and seems to work nicely, thus:
>
> Acked-by: Helge Deller <deller@xxxxxx>

Thanks Helge,

Alex

> Helge
>
>
>
> > ---
> >   arch/parisc/kernel/sys_parisc.c | 8 +++-----
> >   1 file changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
> > index 5d458a44b09c..e987f3a8eb0b 100644
> > --- a/arch/parisc/kernel/sys_parisc.c
> > +++ b/arch/parisc/kernel/sys_parisc.c
> > @@ -119,7 +119,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
> >
> >   	info.flags = 0;
> >   	info.length = len;
> > -	info.low_limit = mm->mmap_legacy_base;
> > +	info.low_limit = mm->mmap_base;
> >   	info.high_limit = mmap_upper_limit(NULL);
> >   	info.align_mask = last_mmap ? (PAGE_MASK & (SHM_COLOUR - 1)) : 0;
> >   	info.align_offset = shared_align_offset(last_mmap, pgoff);
> > @@ -240,13 +240,11 @@ static unsigned long mmap_legacy_base(void)
> >    */
> >   void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
> >   {
> > -	mm->mmap_legacy_base = mmap_legacy_base();
> > -	mm->mmap_base = mmap_upper_limit(rlim_stack);
> > -
> >   	if (mmap_is_legacy()) {
> > -		mm->mmap_base = mm->mmap_legacy_base;
> > +		mm->mmap_base = mmap_legacy_base();
> >   		mm->get_unmapped_area = arch_get_unmapped_area;
> >   	} else {
> > +		mm->mmap_base = mmap_upper_limit(rlim_stack);
> >   		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
> >   	}
> >   }