Re: [RFC PATCH v2 00/21] KCFI support

[Sami Tolvanen <samitolvanen@google.com>]

On Tue, May 17, 2022 at 1:58 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, May 13, 2022 at 01:21:38PM -0700, Sami Tolvanen wrote:
> > KCFI is a proposed forward-edge control-flow integrity scheme for
> > Clang, which is more suitable for kernel use than the existing CFI
> > scheme used by CONFIG_CFI_CLANG. KCFI doesn't require LTO, doesn't
> > alter function references to point to a jump table, and won't break
> > function address equality. The latest LLVM patch is here:
> >
> >   https://reviews.llvm.org/D119296
> >
> > This RFC series replaces the current arm64 CFI implementation with
> > KCFI and adds support for x86_64.
>
> You have some weird behaviour vs weak functions (I so hate those)...
>
> 100: 0000000000000980     9 FUNC    LOCAL  DEFAULT    2 __cfi_free_initmem
> 233: 0000000000000989    35 FUNC    WEAK   DEFAULT    2 free_initmem
>
> With the result that on the final link:
>
>    179: 00000000000009b0     9 FUNC    LOCAL  DEFAULT    1 __cfi_free_initmem
>   8689: 00000000000007f0     9 FUNC    LOCAL  DEFAULT   65 __cfi_free_initmem
> 173283: 00000000000007f9   198 FUNC    GLOBAL DEFAULT   65 free_initmem
>
> This is getting me objtool issues (I'll fix them) but perhaps it's
> something you can do something about as well.

Good catch, I'll fix this.

Sami