From: Josef Bacik <jba...@fb.com>
Date: Wed, 28 Sep 2016 10:54:32 -0400
> Suppose you have a map array value that is something like this
>
> struct foo {
> unsigned iter;
> int array[SOME_CONSTANT];
> };
>
> You can easily insert this into an array, but you cannot modify the contents
> of
> foo->array[] after the fact. This is because we have no way to verify we
> won't
> go off the end of the array at verification time. This patch provides a start
> for this work. We accomplish this by keeping track of a minimum and maximum
> value a register could be while we're checking the code. Then at the time we
> try to do an access into a MAP_VALUE we verify that the maximum offset into
> that
> region is a valid access into that memory region. So in practice, code such
> as
> this
>
> unsigned index = 0;
>
> if (foo->iter >= SOME_CONSTANT)
> foo->iter = index;
> else
> index = foo->iter++;
> foo->array[index] = bar;
>
> would be allowed, as we can verify that index will always be between 0 and
> SOME_CONSTANT-1. If you wish to use signed values you'll have to have an
> extra
> check to make sure the index isn't less than 0, or do something like index %=
> SOME_CONSTANT.
>
> Signed-off-by: Josef Bacik <jba...@fb.com>
> Acked-by: Alexei Starovoitov <a...@kernel.org>
Applied, thanks.
