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authorSami Tolvanen <samitolvanen@google.com>2021-08-16 21:05:19 +0300
committerMasahiro Yamada <masahiroy@kernel.org>2021-09-03 02:12:39 +0300
commit850ded46c64299f04d15e39caaba21963fb966f8 (patch)
tree782ee2114059886c099257096c2ede2623ad0b1e /scripts/Makefile.build
parent7d73c3e9c51400d3e0e755488050804e4d44737a (diff)
downloadlinux-850ded46c64299f04d15e39caaba21963fb966f8.tar.xz
kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG
With CONFIG_LTO_CLANG, we currently link modules into native code just before modpost, which means with TRIM_UNUSED_KSYMS enabled, we still look at the LLVM bitcode in the .o files when generating the list of used symbols. As the bitcode doesn't yet have calls to compiler intrinsics and llvm-nm doesn't see function references that only exist in function-level inline assembly, we currently need a whitelist for TRIM_UNUSED_KSYMS to work with LTO. This change moves module LTO linking to happen earlier, and thus avoids the issue with LLVM bitcode and TRIM_UNUSED_KSYMS entirely, allowing us to also drop the whitelist from gen_autoksyms.sh. Link: https://github.com/ClangBuiltLinux/linux/issues/1369 Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Alexander Lobakin <alobakin@pm.me> Tested-by: Alexander Lobakin <alobakin@pm.me> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'scripts/Makefile.build')
-rw-r--r--scripts/Makefile.build27
1 files changed, 26 insertions, 1 deletions
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 02197cb8e3a7..ea549579bfb7 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -88,6 +88,10 @@ endif
targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
+ifdef CONFIG_LTO_CLANG
+targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m)))
+endif
+
ifdef need-modorder
targets-for-modules += $(obj)/modules.order
endif
@@ -271,12 +275,33 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) $$(objtool_dep) FORCE
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)
+ifdef CONFIG_LTO_CLANG
+# Module .o files may contain LLVM bitcode, compile them into native code
+# before ELF processing
+quiet_cmd_cc_lto_link_modules = LTO [M] $@
+cmd_cc_lto_link_modules = \
+ $(LD) $(ld_flags) -r -o $@ \
+ $(shell [ -s $(@:.lto.o=.o.symversions) ] && \
+ echo -T $(@:.lto.o=.o.symversions)) \
+ --whole-archive $(filter-out FORCE,$^)
+
+ifdef CONFIG_STACK_VALIDATION
+# objtool was skipped for LLVM bitcode, run it now that we have compiled
+# modules into native code
+cmd_cc_lto_link_modules += ; \
+ $(objtree)/tools/objtool/objtool $(objtool_args) --module $@
+endif
+
+$(obj)/%.lto.o: $(obj)/%.o FORCE
+ $(call if_changed,cc_lto_link_modules)
+endif
+
cmd_mod = { \
echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
$(undefined_syms) echo; \
} > $@
-$(obj)/%.mod: $(obj)/%.o FORCE
+$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
$(call if_changed,mod)
quiet_cmd_cc_lst_c = MKLST $@