kbuild: use $(src) instead of $(srctree)/$(src) for source directory

Kbuild conventionally uses $(obj)/ for generated files, and $(src)/ for
checked-in source files. It is merely a convention without any functional
difference. In fact, $(obj) and $(src) are exactly the same, as defined
in scripts/Makefile.build:

    src := $(obj)

When the kernel is built in a separate output directory, $(src) does
not accurately reflect the source directory location. While Kbuild
resolves this discrepancy by specifying VPATH=$(srctree) to search for
source files, it does not cover all cases. For example, when adding a
header search path for local headers, -I$(srctree)/$(src) is typically
passed to the compiler.

This introduces inconsistency between upstream and downstream Makefiles
because $(src) is used instead of $(srctree)/$(src) for the latter.

To address this inconsistency, this commit changes the semantics of
$(src) so that it always points to the directory in the source tree.

Going forward, the variables used in Makefiles will have the following
meanings:

  $(obj)     - directory in the object tree
  $(src)     - directory in the source tree  (changed by this commit)
  $(objtree) - the top of the kernel object tree
  $(srctree) - the top of the kernel source tree

Consequently, $(srctree)/$(src) in upstream Makefiles need to be replaced
with $(src).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

10 files changed, 22 insertions, 23 deletions

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 2f331879816b..faf37bafa3f8 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -62,8 +62,7 @@ stringify = $(squote)$(quote)$1$(quote)$(squote)
 
 ###
 # The path to Kbuild or Makefile. Kbuild has precedence over Makefile.
-kbuild-dir = $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
-kbuild-file = $(or $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Makefile)
+kbuild-file = $(or $(wildcard $(src)/Kbuild),$(src)/Makefile)
 
 ###
 # Read a file, replacing newlines with spaces
diff --git a/scripts/Makefile.asm-generic b/scripts/Makefile.asm-generic
index 8d01b37b7677..1486abf34c7c 100644
--- a/scripts/Makefile.asm-generic
+++ b/scripts/Makefile.asm-generic
@@ -9,7 +9,7 @@
 PHONY := all
 all:
 
-src := $(subst /generated,,$(obj))
+src := $(srctree)/$(subst /generated,,$(obj))
 
 include $(srctree)/scripts/Kbuild.include
 -include $(kbuild-file)
@@ -20,14 +20,14 @@ include $(srctree)/$(generic)/Kbuild
 endif
 
 redundant := $(filter $(mandatory-y) $(generated-y), $(generic-y))
-redundant += $(foreach f, $(generic-y), $(if $(wildcard $(srctree)/$(src)/$(f)),$(f)))
+redundant += $(foreach f, $(generic-y), $(if $(wildcard $(src)/$(f)),$(f)))
 redundant := $(sort $(redundant))
 $(if $(redundant),\
 	$(warning redundant generic-y found in $(src)/Kbuild: $(redundant)))
 
 # If arch does not implement mandatory headers, fallback to asm-generic ones.
 mandatory-y := $(filter-out $(generated-y), $(mandatory-y))
-generic-y   += $(foreach f, $(mandatory-y), $(if $(wildcard $(srctree)/$(src)/$(f)),,$(f)))
+generic-y   += $(foreach f, $(mandatory-y), $(if $(wildcard $(src)/$(f)),,$(f)))
 
 generic-y   := $(addprefix $(obj)/, $(generic-y))
 generated-y := $(addprefix $(obj)/, $(generated-y))
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 41138346afb0..43b71c3d0ff6 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -3,7 +3,7 @@
 # Building
 # ==========================================================================
 
-src := $(obj)
+src := $(if $(VPATH),$(VPATH)/)$(obj)
 
 PHONY := $(obj)/
 $(obj)/:
diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
index f2cb4d7ffd96..4fcfab40ed61 100644
--- a/scripts/Makefile.clean
+++ b/scripts/Makefile.clean
@@ -3,7 +3,7 @@
 # Cleaning up
 # ==========================================================================
 
-src := $(obj)
+src := $(if $(VPATH),$(VPATH)/)$(obj)
 
 PHONY := __clean
 __clean:
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 42d3c772c8e0..08d42e93bea0 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -209,13 +209,13 @@ _c_flags += $(if $(patsubst n%,, \
 	-D__KCSAN_INSTRUMENT_BARRIERS__)
 endif
 
-# $(srctree)/$(src) for including checkin headers from generated source files
-# $(objtree)/$(obj) for including generated headers from checkin source files
+# $(src) for including checkin headers from generated source files
+# $(obj) for including generated headers from checkin source files
 ifeq ($(KBUILD_EXTMOD),)
 ifdef building_out_of_srctree
-_c_flags   += $(addprefix -I $(srctree)/,$(src)) $(addprefix -I $(objtree)/,$(obj))
-_a_flags   += $(addprefix -I $(srctree)/,$(src)) $(addprefix -I $(objtree)/,$(obj))
-_cpp_flags += $(addprefix -I $(srctree)/,$(src)) $(addprefix -I $(objtree)/,$(obj))
+_c_flags   += $(addprefix -I, $(src) $(obj))
+_a_flags   += $(addprefix -I, $(src) $(obj))
+_cpp_flags += $(addprefix -I, $(src) $(obj))
 endif
 endif
 
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 739402f45509..68c4f9ee0c90 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -112,7 +112,7 @@ else
 
 # set src + obj - they may be used in the modules's Makefile
 obj := $(KBUILD_EXTMOD)
-src := $(obj)
+src := $(if $(VPATH),$(VPATH)/)$(obj)
 
 # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
 include $(kbuild-file)
diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
index 4d32b9497da9..a18657072541 100644
--- a/scripts/dtc/Makefile
+++ b/scripts/dtc/Makefile
@@ -16,12 +16,12 @@ libfdt		= $(addprefix libfdt/,$(libfdt-objs))
 fdtoverlay-objs	:= $(libfdt) fdtoverlay.o util.o
 
 # Source files need to get at the userspace version of libfdt_env.h to compile
-HOST_EXTRACFLAGS += -I $(srctree)/$(src)/libfdt
+HOST_EXTRACFLAGS += -I $(src)/libfdt
 HOST_EXTRACFLAGS += -DNO_YAML
 
 # Generated files need one more search path to include headers in source tree
-HOSTCFLAGS_dtc-lexer.lex.o := -I $(srctree)/$(src)
-HOSTCFLAGS_dtc-parser.tab.o := -I $(srctree)/$(src)
+HOSTCFLAGS_dtc-lexer.lex.o := -I $(src)
+HOSTCFLAGS_dtc-parser.tab.o := -I $(src)
 
 # dependencies on generated files need to be listed explicitly
 $(obj)/dtc-lexer.lex.o: $(obj)/dtc-parser.tab.h
diff --git a/scripts/gdb/linux/Makefile b/scripts/gdb/linux/Makefile
index 48941faa6ea6..d77ad9079d0f 100644
--- a/scripts/gdb/linux/Makefile
+++ b/scripts/gdb/linux/Makefile
@@ -2,7 +2,7 @@
 
 ifdef building_out_of_srctree
 
-symlinks := $(patsubst $(srctree)/$(src)/%,%,$(wildcard $(srctree)/$(src)/*.py))
+symlinks := $(patsubst $(src)/%,%,$(wildcard $(src)/*.py))
 
 quiet_cmd_symlink = SYMLINK $@
       cmd_symlink = ln -fsn $(patsubst $(obj)/%,$(abspath $(srctree))/$(src)/%,$@) $@
diff --git a/scripts/genksyms/Makefile b/scripts/genksyms/Makefile
index d6a422a63b6a..312edccda736 100644
--- a/scripts/genksyms/Makefile
+++ b/scripts/genksyms/Makefile
@@ -23,8 +23,8 @@ $(obj)/pars%.tab.c $(obj)/pars%.tab.h: $(src)/pars%.y FORCE
 endif
 
 # -I needed for generated C source to include headers in source tree
-HOSTCFLAGS_parse.tab.o := -I $(srctree)/$(src)
-HOSTCFLAGS_lex.lex.o := -I $(srctree)/$(src)
+HOSTCFLAGS_parse.tab.o := -I $(src)
+HOSTCFLAGS_lex.lex.o := -I $(src)
 
 # dependencies on generated files need to be listed explicitly
 $(obj)/lex.lex.o: $(obj)/parse.tab.h
diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index ea1bf3b3dbde..a0a0be38cbdc 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -57,7 +57,7 @@ $(foreach c, config menuconfig nconfig gconfig xconfig, $(eval $(call config_rul
 
 PHONY += localmodconfig localyesconfig
 localyesconfig localmodconfig: $(obj)/conf
-	$(Q)$(PERL) $(srctree)/$(src)/streamline_config.pl --$@ $(srctree) $(Kconfig) > .tmp.config
+	$(Q)$(PERL) $(src)/streamline_config.pl --$@ $(srctree) $(Kconfig) > .tmp.config
 	$(Q)if [ -f .config ]; then 				\
 		cmp -s .tmp.config .config ||			\
 		(mv -f .config .config.old.1;			\
@@ -118,7 +118,7 @@ tinyconfig:
 # CHECK: -o cache_dir=<path> working?
 PHONY += testconfig
 testconfig: $(obj)/conf
-	$(Q)$(PYTHON3) -B -m pytest $(srctree)/$(src)/tests \
+	$(Q)$(PYTHON3) -B -m pytest $(src)/tests \
 	-o cache_dir=$(abspath $(obj)/tests/.cache) \
 	$(if $(findstring 1,$(KBUILD_VERBOSE)),--capture=no)
 clean-files += tests/.cache
@@ -165,8 +165,8 @@ common-objs	:= confdata.o expr.o lexer.lex.o menu.o parser.tab.o \
 		   preprocess.o symbol.o util.o
 
 $(obj)/lexer.lex.o: $(obj)/parser.tab.h
-HOSTCFLAGS_lexer.lex.o	:= -I $(srctree)/$(src)
-HOSTCFLAGS_parser.tab.o	:= -I $(srctree)/$(src)
+HOSTCFLAGS_lexer.lex.o	:= -I $(src)
+HOSTCFLAGS_parser.tab.o	:= -I $(src)
 
 # conf: Used for defconfig, oldconfig and related targets
 hostprogs	+= conf