[PATCH v2] rust: add flags for shadow call stack sanitizer

[Will Deacon]

On Tue, Apr 30, 2024 at 11:09:25AM +0000, Alice Ryhl wrote:
> Will Deacon <will at kernel.org> wrote:
> > On Tue, Mar 05, 2024 at 01:14:19PM +0100, Miguel Ojeda wrote:
> >> Otherwise partially reverting to the `target.json` approach sounds good too.
> >> 
> >> I added the `-Zuse-sync-unwind=n` to the list at
> >> https://github.com/Rust-for-Linux/linux/issues/2. Given the default is
> >> what we want, I have put it in the "Good to have" section.
> > 
> > I think we have time to do this properly, like we did for the clang
> > enablement a few years ago. In hindsight, avoiding hacks for the early
> > toolchains back then was a really good idea because it meant we could
> > rely on a solid baseline set of compiler features from the start.
> > 
> > So, please can we fix this in rustc and just have SCS dependent on that?
> 
> Just to keep you in the loop, I've posted a PR to make rustc recognize
> the reserve-x18 target feature, so that the -Ctarget-feature=+reserve-x18
> flag stops emitting a warning.
> 
> This should be sufficient for adding support for CONFIG_DYNAMIC_SCS.
> 
> You can find it here:
> https://github.com/rust-lang/rust/pull/124323
> 
> As for non-dynamic SCS, I plan to tackle that after the PR is merged.
> See the "Future possibilities" section in the linked PR for more info on
> that.

Thanks for persevering with this, Alice. I read the pull request above,
but it looks like you went with:

https://github.com/rust-lang/rust/pull/124655

instead, which was merged (hurrah!). Do we need anything else?

Will