Re: [PATCH v10 25/27] x86: enable initial Rust support

[Greg Kroah-Hartman]

On Mon, Oct 09, 2023 at 06:31:13PM +0200, Miguel Ojeda wrote:
> On Mon, Oct 9, 2023 at 6:01 PM Matthew Maurer <mmaurer@xxxxxxxxxx> wrote:
> >
> > If the IBT part would be helpful by itself immediately, I can split
> > that out - it's only the KCFI portion that won't currently work.
> 
> Thanks Matthew. I don't think we are in a rush, but if it is not too
> much work to split it, that would be great, instead of adding the
> restriction.
> 
> For retthunk, by the way, I forgot to mention to Greg above that (in
> the original discussion with PeterZ) that I did a quick test back then
> to hack the equivalent of `-mfunction-return=thunk-extern` into
> `rustc` to show that the compiler could use it via LLVM (by passing
> the attribute in the IR). At least at a basic level it seemed to work:
> I got a userspace program to count the times that it went through the
> return thunk. I didn't try to do anything on the kernel side, but at
> least for the compiler side, it seemed OK. So it may be way easier (on
> the compiler side) than the CFI work?

It should hopefully be much easier than CFI, it was a much simpler
change to gcc and clang when it landed.

thanks,

greg k-h