Merge tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - do not generate unneeded top-level built-in.a

 - let git ignore O= directory entirely

 - optimize scripts/kallsyms slightly

 - exclude DWARF info from *.s regardless of config options

 - fix GCC toolchain search path for Clang to prepare ld.lld support

 - do not generate modules.order when CONFIG_MODULES is disabled

 - simplify single target rules and remove VPATH for external module
   build

 - allow to add optional flags to dpkg-buildpackage when building
   deb-pkg

 - move some compiler option tests from Makefile to Kconfig

 - various Makefile cleanups

* tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (40 commits)
  kbuild: remove scripts/basic/% build target
  kbuild: use -Werror=implicit-... instead of -Werror-implicit-...
  kbuild: clean up scripts/gcc-version.sh
  kbuild: remove cc-version macro
  kbuild: update comment block of scripts/clang-version.sh
  kbuild: remove commented-out INITRD_COMPRESS
  kbuild: move -gsplit-dwarf, -gdwarf-4 option tests to Kconfig
  kbuild: [bin]deb-pkg: add DPKG_FLAGS variable
  kbuild: move ".config not found!" message from Kconfig to Makefile
  kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing
  kbuild: simplify single target rules
  kbuild: remove empty rules for makefiles
  kbuild: make -r/-R effective in top Makefile for old Make versions
  kbuild: move tools_silent to a more relevant place
  kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig
  kbuild: refactor cc-cross-prefix implementation
  kbuild: hardcode genksyms path and remove GENKSYMS variable
  scripts/gdb: refactor rules for symlink creation
  kbuild: create symlink to vmlinux-gdb.py in scripts_gdb target
  scripts/gdb: do not descend into scripts/gdb from scripts
  ...

Author: torvalds

Documentation/devicetree/bindings/Makefile

@@ -15,7 +15,7 @@ DT_TMP_SCHEMA := processed-schema.yaml
 extra-y += $(DT_TMP_SCHEMA)
 
 quiet_cmd_mk_schema = SCHEMA  $@
-      cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(filter-out FORCE, $^)
+      cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(real-prereqs)
 
 DT_DOCS = $(shell \
 	cd $(srctree)/$(src) && \

Documentation/kbuild/kbuild.txt

@@ -232,17 +232,12 @@ KBUILD_LDS
 --------------------------------------------------
 The linker script with full path. Assigned by the top-level Makefile.
 
-KBUILD_VMLINUX_INIT
+KBUILD_VMLINUX_OBJS
 --------------------------------------------------
-All object files for the init (first) part of vmlinux.
-Files specified with KBUILD_VMLINUX_INIT are linked first.
-
-KBUILD_VMLINUX_MAIN
---------------------------------------------------
-All object files for the main part of vmlinux.
+All object files for vmlinux. They are linked to vmlinux in the same
+order as listed in KBUILD_VMLINUX_OBJS.
 
 KBUILD_VMLINUX_LIBS
 --------------------------------------------------
-All .a "lib" files for vmlinux.
-KBUILD_VMLINUX_INIT, KBUILD_VMLINUX_MAIN, and KBUILD_VMLINUX_LIBS together
-specify all the object files used to link vmlinux.
+All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and KBUILD_VMLINUX_LIBS
+together specify all the object files used to link vmlinux.

Documentation/kbuild/makefiles.txt

@@ -154,13 +154,8 @@ more details, with real examples.
 
 	Kbuild compiles all the $(obj-y) files.  It then calls
 	"$(AR) rcSTP" to merge these files into one built-in.a file.
-	This is a thin archive without a symbol table, which makes it
-	unsuitable as a linker input.
-
-	The scripts/link-vmlinux.sh script later makes an aggregate
-	built-in.a with "${AR} rcsTP", which creates the thin archive
-	with a symbol table and an index, making it a valid input for
-	the final vmlinux link passes.
+	This is a thin archive without a symbol table. It will be later
+	linked into vmlinux by scripts/link-vmlinux.sh
 
 	The order of files in $(obj-y) is significant.  Duplicates in
 	the lists are allowed: the first instance will be linked into
@@ -504,23 +499,6 @@ more details, with real examples.
 	In the above example, -Wno-unused-but-set-variable will be added to
 	KBUILD_CFLAGS only if gcc really accepts it.
 
-    cc-version
-	cc-version returns a numerical version of the $(CC) compiler version.
-	The format is <major><minor> where both are two digits. So for example
-	gcc 3.41 would return 0341.
-	cc-version is useful when a specific $(CC) version is faulty in one
-	area, for example -mregparm=3 was broken in some gcc versions
-	even though the option was accepted by gcc.
-
-	Example:
-		#arch/x86/Makefile
-		cflags-y += $(shell \
-		if [ $(cc-version) -ge 0300 ] ; then \
-			echo "-mregparm=3"; fi ;)
-
-	In the above example, -mregparm=3 is only used for gcc version greater
-	than or equal to gcc 3.0.
-
     cc-ifversion
 	cc-ifversion tests the version of $(CC) and equals the fourth parameter
 	if version expression is true, or the fifth (if given) if the version

Documentation/kbuild/modules.txt

@@ -140,7 +140,7 @@ executed to make module versioning work.
 		make -C $KDIR M=$PWD bar.lst
 		make -C $KDIR M=$PWD baz.o
 		make -C $KDIR M=$PWD foo.ko
-		make -C $KDIR M=$PWD /
+		make -C $KDIR M=$PWD ./
 
 
 === 3. Creating a Kbuild File for an External Module

Kbuild

@@ -1,16 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # Kbuild for top-level directory of the kernel
-# This file takes care of the following:
-# 1) Generate bounds.h
-# 2) Generate timeconst.h
-# 3) Generate asm-offsets.h (may need bounds.h and timeconst.h)
-# 4) Check for missing system calls
-# 5) check atomics headers are up-to-date
-# 6) Generate constants.py (may need bounds.h)
 
 #####
-# 1) Generate bounds.h
+# Generate bounds.h
 
 bounds-file := include/generated/bounds.h
 
@@ -21,7 +14,7 @@ $(bounds-file): kernel/bounds.s FORCE
 	$(call filechk,offsets,__LINUX_BOUNDS_H__)
 
 #####
-# 2) Generate timeconst.h
+# Generate timeconst.h
 
 timeconst-file := include/generated/timeconst.h
 
@@ -33,8 +26,7 @@ $(timeconst-file): kernel/time/timeconst.bc FORCE
 	$(call filechk,gentimeconst)
 
 #####
-# 3) Generate asm-offsets.h
-#
+# Generate asm-offsets.h
 
 offsets-file := include/generated/asm-offsets.h
 
@@ -47,8 +39,7 @@ $(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
 	$(call filechk,offsets,__ASM_OFFSETS_H__)
 
 #####
-# 4) Check for missing system calls
-#
+# Check for missing system calls
 
 always += missing-syscalls
 targets += missing-syscalls
@@ -60,8 +51,7 @@ missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
 	$(call cmd,syscalls)
 
 #####
-# 5) Check atomic headers are up-to-date
-#
+# Check atomic headers are up-to-date
 
 always += old-atomics
 targets += old-atomics
@@ -72,14 +62,5 @@ quiet_cmd_atomics = CALL    $<
 old-atomics: scripts/atomic/check-atomics.sh FORCE
 	$(call cmd,atomics)
 
-#####
-# 6) Generate constants for Python GDB integration
-#
-
-extra-$(CONFIG_GDB_SCRIPTS) += build_constants_py
-
-build_constants_py: $(timeconst-file) $(bounds-file)
-	@$(MAKE) $(build)=scripts/gdb/linux $@
-
 # Keep these three files during make clean
 no-clean-files := $(bounds-file) $(offsets-file) $(timeconst-file)