Re: [RFC PATCH v3 20/20] x86: Add support for CONFIG_CFI_CLANG

[Sami Tolvanen]

On Sat, Jul 23, 2022 at 4:21 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Fri, Jun 10, 2022 at 04:35:13PM -0700, Sami Tolvanen wrote:
>
> > +#ifdef CONFIG_CFI_CLANG
> > +#define __CFI_TYPE(name)                                     \
> > +     .fill 7, 1, 0xCC ASM_NL                                 \
> > +     SYM_START(__cfi_##name, SYM_L_LOCAL, SYM_A_NONE)        \
> > +     int3 ASM_NL                                             \
> > +     int3 ASM_NL                                             \
> > +     mov __kcfi_typeid_##name, %eax ASM_NL                   \
> > +     int3 ASM_NL                                             \
> > +     int3 ASM_NL                                             \
> > +     SYM_FUNC_END(__cfi_##name)
> > +#endif
>
> Like said on IRC yesterday, this doesn't generate the right mov
> encoding.
>
>         .byte 0xb8 ; .long __kcfi_typeid_##name ;               \
>
> works. Your LLVM tree already has the ZExt patch you gave me yesterday
> to fix up the linker fallout from this change.

Indeed, I updated my kernel tree and confirmed that this fixes the
issue. Thanks for pointing it out.

Sami