Re: [PATCH v2] kallsyms: strip LTO-only suffixes from promoted global functions

[Yonghong Song]

On 7/12/23 3:40 PM, Kees Cook wrote:
> On Wed, 28 Jun 2023 11:19:26 -0700, Yonghong Song wrote:
> > Commit 6eb4bd92c1ce ("kallsyms: strip LTO suffixes from static functions")
> > stripped all function/variable suffixes started with '.' regardless
> > of whether those suffixes are generated at LTO mode or not. In fact,
> > as far as I know, in LTO mode, when a static function/variable is
> > promoted to the global scope, '.llvm.<...>' suffix is added.
> >
> > The existing mechanism breaks live patch for a LTO kernel even if
> > no <symbol>.llvm.<...> symbols are involved. For example, for the following
> > kernel symbols:
> >    $ grep bpf_verifier_vlog /proc/kallsyms
> >    ffffffff81549f60 t bpf_verifier_vlog
> >    ffffffff8268b430 d bpf_verifier_vlog._entry
> >    ffffffff8282a958 d bpf_verifier_vlog._entry_ptr
> >    ffffffff82e12a1f d bpf_verifier_vlog.__already_done
> > 'bpf_verifier_vlog' is a static function. '_entry', '_entry_ptr' and
> > '__already_done' are static variables used inside 'bpf_verifier_vlog',
> > so llvm promotes them to file-level static with prefix 'bpf_verifier_vlog.'.
> > Note that the func-level to file-level static function promotion also
> > happens without LTO.
> >
> > [...]
>
> Applied, thanks!
>
> [1/1] kallsyms: strip LTO-only suffixes from promoted global functions
>        https://git.kernel.org/kees/c/8cc32a9bbf29

Thanks Kees!

> Best regards,