[RFC PATCH v3 5/6] kbuild: Add objtool integration for PowerPC feature fixups

[Sathvika Vasireddy <sv@linux.ibm.com>]

Add build system support for PowerPC feature fixup processing:

- Add HAVE_OBJTOOL_FTR_FIXUP config option for architectures that support
  build-time feature fixup processing
- Integrate objtool feature fixup processing into vmlinux build

Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
---
 Makefile                 | 7 +++++++
 scripts/Makefile.lib     | 4 ++--
 scripts/Makefile.vmlinux | 3 ++-
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 665b79aa21b8..383e35b39a15 100644
--- a/Makefile
+++ b/Makefile
@@ -1451,6 +1451,13 @@ ifdef CONFIG_OBJTOOL
 prepare: tools/objtool
 endif
 
+# CONFIG_OBJTOOL and CONFIG_HAVE_OBJTOOL_FTR_FIXUP are unrelated, separate
+# options. It was integrated in objtool in order to borrow the elf parser,
+# but this is different from how the other objtool commands are used.
+ifdef CONFIG_HAVE_OBJTOOL_FTR_FIXUP
+prepare: tools/objtool
+endif
+
 ifdef CONFIG_BPF
 ifdef CONFIG_DEBUG_INFO_BTF
 prepare: tools/bpf/resolve_btfids
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 28a1c08e3b22..dc090b11bdf2 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -169,10 +169,10 @@ cpp_flags      = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 
 ld_flags       = $(KBUILD_LDFLAGS) $(ldflags-y) $(LDFLAGS_$(@F))
 
-ifdef CONFIG_OBJTOOL
-
 objtool := $(objtree)/tools/objtool/objtool
 
+ifdef CONFIG_OBJTOOL
+
 objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
 objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
 objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index cd788cac9d91..e3dd7fc62f20 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -65,7 +65,8 @@ ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
 # Final link of vmlinux with optional arch pass after final link
 cmd_link_vmlinux =							\
 	$< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)" "$@";	\
-	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
+	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true);	\
+	$(if $(CONFIG_HAVE_OBJTOOL_FTR_FIXUP), $(objtool) --ftr-fixup --link $@, true)
 
 targets += vmlinux.unstripped .vmlinux.export.o
 vmlinux.unstripped: scripts/link-vmlinux.sh vmlinux.o .vmlinux.export.o $(KBUILD_LDS) FORCE
-- 
2.43.0