Hi Pierre-Clément,
On Fri, Jun 23, 2023 at 7:08 AM Pierre-Clément Tosi <ptosi@xxxxxxxxxx> wrote:
>
> The (relatively) new KCFI feature in LLVM/Clang encodes type information
> for C functions by generating symbols named __kcfi_typeid_<fname>, which
> can then be referenced from assembly. However, some custom build rules
> (e.g. EFI, nVHE, or early PIE on arm64) use objcopy to add a prefix to
> all the symbols in their object files, making mksysmap's ignore filter
> miss those KCFI symbols.
>
> Therefore, explicitly list those twice-prefixed KCFI symbols as ignored.
>
> Alternatively, this could also be achieved in a less verbose way by
> ignoring any symbol containing the string "__kcfi_typeid_". However,
> listing the combined prefixes explicitly saves us from running the small
> risk of ignoring symbols that should be kept.
>
> Signed-off-by: Pierre-Clément Tosi <ptosi@xxxxxxxxxx>
> ---
> scripts/mksysmap | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/scripts/mksysmap b/scripts/mksysmap
> index 26f39772f7a5..17cf4292e26b 100755
> --- a/scripts/mksysmap
> +++ b/scripts/mksysmap
> @@ -61,7 +61,10 @@ ${NM} -n ${1} | sed >${2} -e "
> / __microLA25Thunk_/d
>
> # CFI type identifiers
> +/ __efistub___kcfi_typeid_/d
Does the existing __efistub_/d rule not catch this?
> / __kcfi_typeid_/d
> +/ __kvm_nvhe___kcfi_typeid_/d
> +/ __pi___kcfi_typeid_/d
Either way, otherwise this looks reasonable to me. Thanks for the patch!
Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Sami
