On ma. 25. april 2022 kl. 04.08 +0000 Masahiro Yamada wrote:
> When CONFIG_MODVERSIONS=y, the output from genksyms is saved in
> separate *.symversions files, and will be used much later when
> CONFIG_LTO_CLANG=y because it is impossible to update LLVM bit code
> here.
>
> This approach is not robust because:
>
> - *.symversions may or may not exist. If *.symversions does not
> exist, we never know if it is missing for legitimate reason
> (i.e. no EXPORT_SYMBOL) or something bad has happened (for
> example, the user accidentally deleted it). Once it occurs,
> it is not self-healing because *.symversions is generated
> as a side effect of the build rule of the object.
>
> - stale (i.e. invalid) *.symversions might be picked up if an
> object is generated in a non-ordinary way, and corresponding
> *.symversions (, which was generated by old builds) just happen
> to exist.
>
> A more robust approach is to save symbol versions in *.cmd files
> because:
>
> - *.cmd always exists (if the object is generated by if_changed
> rule or friends). Even if the user accidentally deletes it,
> it will be regenerated in the next build.
>
> - *.cmd is always re-generated when the object is updated. This
> avoid stale version information being picked up.
>
> I will remove *.symversions later.
>
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> ---
>
> scripts/Makefile.build | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index f6a506318795..e03e85c90b26 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -175,6 +175,8 @@ gen_symversions = \
> if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \
> $(call cmd_gensymtypes_$(1),$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
> > $@.symversions; \
> + echo >> $(dot-target).cmd ; \
> + sed 's/\(.*\) = \(.*\);/$(pound)\1=\2/' $@.symversions >> $(dot-target).cmd ; \
> else \
> rm -f $@.symversions; \
> fi
While reviewing this patch, I was missing the update of the comment a
few lines above. But I understand that it makes more sense to update
it in the follow-up patch.
Tested-by: Nicolas Schier <nicolas@xxxxxxxxx>
Reviewed-by: Nicolas Schier <nicolas@xxxxxxxxx>
> --
> 2.32.0
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