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authorMasahiro Yamada <masahiroy@kernel.org>2022-05-05 16:22:35 +0900
committerMasahiro Yamada <masahiroy@kernel.org>2022-05-11 21:46:39 +0900
commit78e9e56af3858bf2c52c065daa6c8bee0d72048c (patch)
tree77732a7f52cdd495fae4ef92a1fce5efd326b913 /scripts
parente493f472752000968f5b30aac10391288cfbf5b1 (diff)
kbuild: record symbol versions in *.cmd files
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> Tested-by: Nathan Chancellor <nathan@kernel.org>
Diffstat (limited to 'scripts')
-rw-r--r--scripts/Makefile.build7
1 files changed, 7 insertions, 0 deletions
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