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kbuild: lto: fix module versioning

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With CONFIG_MODVERSIONS, version information is linked into each
compilation unit that exports symbols. With LTO, we cannot use this
method as all C code is compiled into LLVM bitcode instead. This
change collects symbol versions into .symversions files and merges
them in link-vmlinux.sh where they are all linked into vmlinux.o at
the same time.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-4-samitolvanen@google.com
This commit is contained in:
Sami Tolvanen 2020-12-11 10:46:20 -08:00 • committed by Kees Cook
parent dc5723b02e
commit 38e8918490
6 changed files with 61 additions and 6 deletions
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6
scripts/Makefile.modpost
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@ -111,7 +111,11 @@ ifdef CONFIG_LTO_CLANG
prelink-ext := .lto
quiet_cmd_cc_lto_link_modules = LTO [M] $@
cmd_cc_lto_link_modules = $(LD) $(ld_flags) -r -o $@ --whole-archive $^
cmd_cc_lto_link_modules = \
$(LD) $(ld_flags) -r -o $@ \
$(shell [ -s $(@:.lto.o=.o.symversions) ] && \
echo -T $(@:.lto.o=.o.symversions)) \
--whole-archive $^
%.lto.o: %.o
$(call if_changed,cc_lto_link_modules)