Re: [PATCH 02/12] arm64/module: Fix BTI exceptions caused by omitted landing pads in Clang 21

[Josh Poimboeuf <jpoimboe@kernel.org>]

On Sun, Aug 16, 2026 at 04:49:59PM +0300, Ard Biesheuvel wrote:
> On Sun, 16 Aug 2026, at 12:41, Will Deacon wrote:
> > Overall, it seems to me like there are three cases we need to consider
> > for re-enabling BTI in the kernel:
> >
> > 1. A cross-section call that spans beyond the 128M range and therefore
> >    needs a veneer. I think the static linker should resolve this, probably
> >    by emitting a second veneer with the landing pad. Do we know if LLD
> >    gets this right?
> >
> 
> There are two variants here:
> 
> A cross-section call .init.text to .text that spans beyond the 128M range:
> 
> 1a. inside vmlinux, which should be dealt with by the linker, but which might
> be unreliable in practice due to the lack of BTI annotations in asm files,
> missing exec permissions on ELF sections etc. This is addressed by this series,
> but is only an issue for unusually large kernel images (e.g., allyesconfig).

Right, and if we don't care about the >128MB kernel case (I have no idea
if anybody actually uses that big of a kernel?), then we can basically
just drop patches 3-11 in favor of a simple linker assertion (similar to
patches 5 and 6) which just *always* triggers a build error on a large
kernel + BTI + !COMPILE_TEST.

-- 
Josh