[PATCH v2] tools/resolve_btfids: Tidy host CFLAGS forcing

[Ian Rogers]

Avoid passing CROSS_COMPILE to submakes and ensure CFLAGS is forced to
HOSTCFLAGS for submake builds. This fixes problems with cross
compilation.

Tidy to not unnecessarily modify/export CFLAGS, make the override for
prepare and build clearer.

Fixes: 13e07691a16f ("tools/resolve_btfids: Alter how HOSTCC is forced")
Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/bpf/resolve_btfids/Makefile | 49 ++++++++++++++++---------------
 1 file changed, 26 insertions(+), 23 deletions(-)

diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
index daed388aa5d7..3ed4e3be4e06 100644
--- a/tools/bpf/resolve_btfids/Makefile
+++ b/tools/bpf/resolve_btfids/Makefile
@@ -17,12 +17,7 @@ else
   MAKEFLAGS=--no-print-directory
 endif
 
-# always use the host compiler
-HOST_OVERRIDES := AR="$(HOSTAR)" CC="$(HOSTCC)" LD="$(HOSTLD)" ARCH="$(HOSTARCH)" \
-		  EXTRA_CFLAGS="$(HOSTCFLAGS) $(KBUILD_HOSTCFLAGS)"
-
 RM      ?= rm
-CROSS_COMPILE =
 
 OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/
 
@@ -43,8 +38,31 @@ SUBCMD_INCLUDE := $(SUBCMD_DESTDIR)include
 BINARY     := $(OUTPUT)/resolve_btfids
 BINARY_IN  := $(BINARY)-in.o
 
+LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)
+LIBELF_LIBS  := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
+
+RESOLVE_BTFIDS_CFLAGS = -g \
+          -I$(srctree)/tools/include \
+          -I$(srctree)/tools/include/uapi \
+          -I$(LIBBPF_INCLUDE) \
+          -I$(SUBCMD_INCLUDE) \
+          $(LIBELF_FLAGS)
+
+# Overrides for the prepare step libraries.
+HOST_OVERRIDES_PREPARE := AR="$(HOSTAR)" CC="$(HOSTCC)" LD="$(HOSTLD)" \
+	  ARCH="$(HOSTARCH)" CROSS_COMPILE=""
+
+# Overrides for Makefile.build C targets.
+HOST_OVERRIDES_BUILD := $(HOST_OVERRIDES_PREPARE) \
+	  CFLAGS="$(HOSTCFLAGS) $(KBUILD_HOSTCFLAGS) $(RESOLVE_BTFIDS_CFLAGS)" \
+
+LIBS = $(LIBELF_LIBS) -lz
+
 all: $(BINARY)
 
+export srctree OUTPUT Q
+include $(srctree)/tools/build/Makefile.include
+
 prepare: $(BPFOBJ) $(SUBCMDOBJ)
 
 $(OUTPUT) $(OUTPUT)/libsubcmd $(LIBBPF_OUT):
@@ -53,31 +71,16 @@ $(OUTPUT) $(OUTPUT)/libsubcmd $(LIBBPF_OUT):
 
 $(SUBCMDOBJ): fixdep FORCE | $(OUTPUT)/libsubcmd
 	$(Q)$(MAKE) -C $(SUBCMD_SRC) OUTPUT=$(SUBCMD_OUT) \
-		    DESTDIR=$(SUBCMD_DESTDIR) $(HOST_OVERRIDES) prefix= subdir= \
+		    DESTDIR=$(SUBCMD_DESTDIR) $(HOST_OVERRIDES_PREPARE) prefix= subdir= \
 		    $(abspath $@) install_headers
 
 $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUT)
 	$(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) OUTPUT=$(LIBBPF_OUT)    \
-		    DESTDIR=$(LIBBPF_DESTDIR) $(HOST_OVERRIDES) prefix= subdir= \
+		    DESTDIR=$(LIBBPF_DESTDIR) $(HOST_OVERRIDES_PREPARE) prefix= subdir= \
 		    $(abspath $@) install_headers
 
-LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)
-LIBELF_LIBS  := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
-
-CFLAGS += -g \
-          -I$(srctree)/tools/include \
-          -I$(srctree)/tools/include/uapi \
-          -I$(LIBBPF_INCLUDE) \
-          -I$(SUBCMD_INCLUDE) \
-          $(LIBELF_FLAGS)
-
-LIBS = $(LIBELF_LIBS) -lz
-
-export srctree OUTPUT CFLAGS Q
-include $(srctree)/tools/build/Makefile.include
-
 $(BINARY_IN): fixdep FORCE prepare | $(OUTPUT)
-	$(Q)$(MAKE) $(build)=resolve_btfids $(HOST_OVERRIDES)
+	$(Q)$(MAKE) $(build)=resolve_btfids $(HOST_OVERRIDES_BUILD)
 
 $(BINARY): $(BPFOBJ) $(SUBCMDOBJ) $(BINARY_IN)
 	$(call msg,LINK,$@)
-- 
2.39.1.519.gcb327c4b5f-goog