[PATCH v1 3/3] objtool: Alter how HOSTCC is forced

[Ian Rogers <irogers@google.com>]

HOSTCC is always wanted when building objtool. Setting CC to HOSTCC
happens after tools/scripts/Makefile.include is included, meaning
flags are set assuming say CC is gcc, but then it can be later set to
HOSTCC which may be clang. tools/scripts/Makefile.include is needed
for host set up and common macros in objtool's Makefile. Rather than
override CC to HOSTCC, just pass CC as HOSTCC to Makefile.build, the
libsubcmd builds and the linkage step. This means the Makefiles don't
see things like CC changing and tool flag determination, and similar,
work properly. To avoid mixing CFLAGS from different compilers just
the objtool CFLAGS are determined. HOSTCFLAGS is added to these so
that command line flags can add to the CFLAGS.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/objtool/Makefile | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 6b6c20ba5160..c9992d73617f 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -2,16 +2,12 @@
 include ../scripts/Makefile.include
 include ../scripts/Makefile.arch
 
-# always use the host compiler
-AR	 = $(HOSTAR)
-CC	 = $(HOSTCC)
-LD	 = $(HOSTLD)
-
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))
 srctree := $(patsubst %/,%,$(dir $(srctree)))
 endif
 
+MAKE = make -S
 LIBSUBCMD_DIR = $(srctree)/tools/lib/subcmd/
 ifneq ($(OUTPUT),)
   LIBSUBCMD_OUTPUT = $(abspath $(OUTPUT))/libsubcmd
@@ -36,13 +32,20 @@ INCLUDES := -I$(srctree)/tools/include \
 	    -I$(srctree)/tools/objtool/include \
 	    -I$(srctree)/tools/objtool/arch/$(SRCARCH)/include \
 	    -I$(LIBSUBCMD_OUTPUT)/include
-WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs
-CFLAGS   := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS)
-LDFLAGS  += $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS)
+WARNINGS := -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs
+OBJTOOL_CFLAGS := -Werror $(WARNINGS) -g $(INCLUDES) $(LIBELF_FLAGS) $(HOSTCFLAGS)
+OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD)
 
 # Allow old libelf to be used:
 elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr)
-CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
+OBJTOOL_CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
+
+# Always want host compilation.
+HOST_OVERRIDES := CC="$(HOSTCC)" EXTRA_CFLAGS="$(OBJTOOL_CFLAGS)" \
+		  LD="$(HOSTLD)" AR="$(HOSTAR)"
+BUILD_HOST_OVERRIDES := CC="$(HOSTCC)" CFLAGS="$(OBJTOOL_CFLAGS)" \
+			LD="$(HOSTLD)" LDFLAGS="$(OBJTOOL_LDFLAGS)" \
+			AR="$(HOSTAR)"
 
 AWK = awk
 MKDIR = mkdir
@@ -65,10 +68,11 @@ include $(srctree)/tools/build/Makefile.include
 
 $(OBJTOOL_IN): fixdep FORCE
 	$(Q)$(CONFIG_SHELL) ./sync-check.sh
-	$(Q)$(MAKE) $(build)=objtool
+	$(Q)$(MAKE) $(build)=objtool $(BUILD_HOST_OVERRIDES)
+
 
 $(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN)
-	$(QUIET_LINK)$(CC) $(OBJTOOL_IN) $(LDFLAGS) -o $@
+	$(QUIET_LINK)$(HOSTCC) $(OBJTOOL_IN) $(KBUILD_HOSTLDFLAGS) $(OBJTOOL_LDFLAGS) -o $@
 
 
 $(LIBSUBCMD_OUTPUT):
@@ -77,6 +81,7 @@ $(LIBSUBCMD_OUTPUT):
 $(LIBSUBCMD): fixdep FORCE $(LIBSUBCMD_OUTPUT)
 	$(Q)$(MAKE) -C $(LIBSUBCMD_DIR) O=$(LIBSUBCMD_OUTPUT) \
 		DESTDIR=$(LIBSUBCMD_DESTDIR) prefix= \
+		$(HOST_OVERRIDES) \
 		$@ install_headers
 
 $(LIBSUBCMD)-clean:
-- 
2.38.1.584.g0f3c55d4c2-goog