On Tue, 31 Mar 2020, Joe Perches wrote:
> On Tue, 2020-03-31 at 10:50 +0200, Julia Lawall wrote:
> > On Mon, 30 Mar 2020, Joe Perches wrote:
> >
> > > There is a block of if tests against the same variable
> > > in include/linux/mtd/pfow.h that likely is defective
> > >
> > > if (prog_status & 0x3)
> > > ...
> > > else if (prog_status & 0x2)
> > > ...
> > > else (prog_status & 0x1)
> > > ...
> > >
> > > If the first test is true the subsequent 2 tests aren't
> > > possible.
> > >
> > > Likely the first test should be something like
> > >
> > > if ((prog_status & 0x03) == 0x03)
> > >
> > > Is there a way for cocci to find this style of bitwise
> > > logic defect?
> >
> > I guess this occurs rarely enough that just looking for a succession of
> > bit and tests on the same variable would be good enough to narrow it down
> > to something manageable to check by hand.
>
> I suppose, but I think misuse of the and'ed bits
> by #define is the most likely defect as it's
> very difficult to verify visually.
>
> Hard to otherwise quantify.
OK, I see that the pattern of a sequence of bit ands is actually quite
common. It should be possible to make something more automatic.
julia
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