Re: [PATCH v9 0/7] Introduce Kernel Control Flow Integrity ABI [PR107048]

[Kees Cook <kees@kernel.org>]

On Thu, Jan 08, 2026 at 09:48:58PM -0800, Andrew Pinski wrote:
> On Thu, Jan 1, 2026 at 7:42 PM Kees Cook <kees@kernel.org> wrote:
> >
> >
> >
> > On January 1, 2026 2:42:59 PM PST, Andrew Pinski <andrew.pinski@oss.qualcomm.com> wrote:
> > >On Tue, Dec 9, 2025 at 6:22 PM Kees Cook <kees@kernel.org> wrote:
> > >>
> > >> Hi,
> > >>
> > >> This series implements[1][2] the Linux Kernel Control Flow Integrity
> > >> ABI, which provides a function prototype based forward edge control flow
> > >> integrity protection by instrumenting every indirect call to check for
> > >> a hash value before the target function address. If the hash at the call
> > >> site and the hash at the target do not match, execution will trap.
> > >>
> > >> I'm hoping we can land front- and middle-end and do architectures as
> > >> they also pass review. What do folks think? I'd really like to get this
> > >> in a position where more people can test with GCC snapshots, etc.
> > >
> > >So looking back into the other implementation that was submitted a few
> > >years back (https://patchwork.sourceware.org/project/gcc/patch/20230325081117.93245-3-ashimida.1990@gmail.com/),
> > >a regnote (REG_CALL_CFI_TYPEID) was used instead of the wrapping with
> > >kfci rtl.
> > >I get the feeling a regnote would be better as there is less for the
> > >backend to deal with including new patterns.
> > >What do others think?
> >
> > I started there and it created way too many problems that I had to continuously hack around. Switching to RTL solved all of it. (See v1 and v2 of this series where that was how it was implemented.)
> 
> Ok, thanks for confirming that. I will try to give v10 a full review
> by the end of next week. But since GCC is starting stage 4 on Monday
> and I think it is too late to add this feature so this might be the
> first thing to be pushed once GCC 17 stage 1 starts (mid to late March
> depending on how fast regressions are fixed).

Thanks! Yeah, I'm not expecting to land this in GCC 16. We're very late
in the cycle. :)

-Kees

-- 
Kees Cook