On Thu, Aug 31, 2017 at 6:01 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
> Ugh, nommu defeats the MAP_SHARED_VALIDATE proposal from Linus.
>
> if ((flags & MAP_TYPE) != MAP_PRIVATE &&
> (flags & MAP_TYPE) != MAP_SHARED)
> return -EINVAL;
>
> ...parisc strikes again.
Why? That's no different from the case statement for the mmu case,
just written differently.
You *want* existing kernels to fail, since they don't test the bits
you want to test.
So you just want to rewrite these all as
switch (flags & MAP_TYPE) {
case MAP_SHARED_VALIDATE:
.. validate the other bits...
/* fallhtough */
case MAP_SHARED:
.. do the shared case ..
case MAP_PRIVATE:
.. do the private case ..
default:
return -EINVAL;
}
and you're all good.
I'm not seeing the problem.
Of course, I also suspect that for nommu you might as well just always
return -EINVAL anyway. The only people who would ever use
MAP_SHARED_VALIDATE are the kinds of people who do things that just
aren't likely relevant on nommu, but whatever..
Linus
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