Re: [PATCH 2/8] bitmap: Introduce bitmap_set, bitmap_clear,

FUJITA Tomonori
2009-10-17T14:51:32Z

On Sat, 17 Oct 2009 23:43:56 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:

> 2009/10/17 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>:
> > On Tue, 13 Oct 2009 18:10:17 +0900
> > Akinobu Mita <akinobu.mita@gmail.com> wrote:
> >
> >> My user space testing exposed off-by-one error find_next_zero_area
> >> in iommu-helper. Some zero area cannot be found by this bug.
> >>
> >> Subject: [PATCH] Fix off-by-one error in find_next_zero_area
> >>
> >> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> >> ---
> >>  lib/iommu-helper.c |    2 +-
> >>  1 files changed, 1 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/lib/iommu-helper.c b/lib/iommu-helper.c
> >> index 75dbda0..afc58bc 100644
> >> --- a/lib/iommu-helper.c
> >> +++ b/lib/iommu-helper.c
> >> @@ -19,7 +19,7 @@ again:
> >>       index = (index + align_mask) & ~align_mask;
> >>
> >>       end = index + nr;
> >> -     if (end >= size)
> >> +     if (end > size)
> >
> > I think that this is intentional; the last byte of the limit doesn't
> > work.
>
> It looks ok to me. Without above change, find_next_zero_area cannot
> find a 64 bits zeroed area in next sample code.

I meant that we don't want to find such area for IOMMUs (IIRC, it code
came from POWER IOMMU).

> unsigned long offset;
>
> DECLARE_BITMAP(map, 64);
>
> bitmap_clear(map, 0, 64);
> offset = find_next_zero_area(map, 64, 0, 64, 0);
> if (offset >= 64)
> printf("not found\n");
> else
> printf("found\n");
> --
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