This is a note to let you know that I've just added the patch titled
kbuild: fix Clang LTO with CONFIG_OBJTOOL=n
to the 6.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kbuild-fix-clang-lto-with-config_objtool-n.patch
and it can be found in the queue-6.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit fe7904010009ae489fad4c00929ff45db65e7094
Author: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Date: Fri Jan 31 23:04:01 2025 +0900
kbuild: fix Clang LTO with CONFIG_OBJTOOL=n
[ Upstream commit 695ed93bb30e03e9f826ee70abdd83f970741a37 ]
Since commit bede169618c6 ("kbuild: enable objtool for *.mod.o and
additional kernel objects"), Clang LTO builds do not perform any
optimizations when CONFIG_OBJTOOL is disabled (e.g., for ARCH=arm64).
This is because every LLVM bitcode file is immediately converted to
ELF format before the object files are linked together.
This commit fixes the breakage.
Fixes: bede169618c6 ("kbuild: enable objtool for *.mod.o and additional kernel objects")
Reported-by: Yonghong Song <yonghong.song@xxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Tested-by: Yonghong Song <yonghong.song@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index c16e4cf54d770..0b85bf27598a8 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -183,7 +183,9 @@ endif # CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
is-standard-object = $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD_$(target-stem).o)$(OBJECT_FILES_NON_STANDARD)n),$(is-kernel-object))
+ifdef CONFIG_OBJTOOL
$(obj)/%.o: private objtool-enabled = $(if $(is-standard-object),$(if $(delay-objtool),$(is-single-obj-m),y))
+endif
ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
cmd_warn_shared_object = $(if $(word 2, $(modname-multi)),$(warning $(kbuild-file): $*.o is added to multiple modules: $(modname-multi)))
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 7395200538da8..2e280a02e9e65 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -287,6 +287,8 @@ delay-objtool := $(or $(CONFIG_LTO_CLANG),$(CONFIG_X86_KERNEL_IBT))
cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool-args) $@)
cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
+objtool-enabled := y
+
endif # CONFIG_OBJTOOL
# Useful for describing the dependency of composite objects
@@ -302,11 +304,11 @@ endef
# ===========================================================================
# These are shared by some Makefile.* files.
-objtool-enabled := y
-
ifdef CONFIG_LTO_CLANG
-# objtool cannot process LLVM IR. Make $(LD) covert LLVM IR to ELF here.
-cmd_ld_single = $(if $(objtool-enabled), ; $(LD) $(ld_flags) -r -o $(tmp-target) $@; mv $(tmp-target) $@)
+# Run $(LD) here to covert LLVM IR to ELF in the following cases:
+# - when this object needs objtool processing, as objtool cannot process LLVM IR
+# - when this is a single-object module, as modpost cannot process LLVM IR
+cmd_ld_single = $(if $(objtool-enabled)$(is-single-obj-m), ; $(LD) $(ld_flags) -r -o $(tmp-target) $@; mv $(tmp-target) $@)
endif
quiet_cmd_cc_o_c = CC $(quiet_modtag) $@
