Re: [PATCH 00/35] Shadow stacks for userspace

Peter Zijlstra
2022-02-06T13:07:16Z

On Fri, Feb 04, 2022 at 01:08:25AM +0000, Edgecombe, Rick P wrote:

> > So how is that going to work? altstack is not an esoteric corner
> > case.
>
> My understanding is that the main usages for the signal stack were
> handling stack overflows and corruption. Since the shadow stack only
> contains return addresses rather than large stack allocations, and is
> not generally writable or pivotable, I thought there was a good
> possibility an alt shadow stack would not end up being especially
> useful. Does it seem like reasonable guesswork?

altstacks are also used in userspace threading implemenations.