Re: [PATCH 2/3] x86/kcfi: Emit the FineIBT paranoid "cs" prefix as a byte

[Peter Zijlstra]

On Mon, Oct 12, 2026 at 02:04:25AM -0700, Kees Cook wrote:
> The "cs" prefix on the LEA in the FineIBT paranoid caller template is
> padding: it places the LEA's 0xf0 immediate byte where it doubles as the
> LOCK prefix that makes the failing Jcc raise #UD. GNU as warns about it
> in every CONFIG_FINEIBT=y build:
> 
>   Warning: segment override on `lea' is ineffectual

Shees...