On Fri, 2025-02-28 at 15:34 -0800, Andrii Nakryiko wrote:
[...]
> > There were two alternatives on the table last time:
> > - add support for tags on global functions;
>
> I was supportive of this, I believe
>
> > - verify global subprogram call tree in post-order,
> > in order to have the flags ready when needed.
>
> Remind me of the details here? we'd start validating the main prog,
> suspend that process when encountering global func, go validate global
> func, once done, come back to main prog, right?
Yes.
The tree can't be built statically if we account for dead code
elimination, as post-order might change.
> Alternatively, we could mark expected properties (restrictions) of
> global subprogs as we encounter them, right? E.g, if we come to global
> func call inside rcu_read_{lock,unlock}() region, we'd mark it
> internally as "needs to be non-sleepable".
For situation like below, suppose verification order is main, foo,
bar, buz:
- main() sleepable
- foo()
- bar()
- foo():
- buz()
- bar():
- foo() while holding lock
- buz():
- calls something sleepable
I think, to handle this the call-tree needs to be built on the main
verification pass, and then checked for sleepable.
But that won't work for changes_pkt_data, as verdict has to be known
right-away to decide whether to invalidate packet pointers.
[...]
