Messages in this thread Patch in this message |  | | From | Masahiro Yamada <> | Subject | [PATCH v2 15/26] kbuild: record symbol versions in *.cmd files | Date | Sun, 1 May 2022 17:40:21 +0900 |
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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.
- 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@kernel.org> Tested-by: Nicolas Schier <nicolas@fjasle.eu> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu> ---
Changes in v2: - Fix CONFIG_MODULE_REL_CRCS=y case
scripts/Makefile.build | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index f6a506318795..a1023868775f 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -171,10 +171,17 @@ ifdef CONFIG_MODVERSIONS # Generate .o.symversions files for each .o with exported symbols, and link these # to the kernel and/or modules at the end. + +genksyms_format_rel_crc := [^_]*__crc_\([^ ]*\) = \.; LONG(\([^)]*\)).* +genksyms_format_normal := __crc_\(.*\) = \(.*\); +genksyms_format := $(if $(CONFIG_MODULE_REL_CRCS),$(genksyms_format_rel_crc),$(genksyms_format_normal)) + gen_symversions = \ if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \ $(call cmd_gensymtypes_$(1),$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \ > $@.symversions; \ + sed -n 's/$(genksyms_format)/$(pound)SYMVER \1 \2/p' $@.symversions \ + >> $(dot-target).cmd; \ else \ rm -f $@.symversions; \ fi -- 2.32.0
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