Currently, every arch/*/include/uapi/asm/Kbuild explicitly includes
the common Kbuild.asm file. Factor out the duplicated include directives
to scripts/Makefile.asm-generic so that no architecture would opt out
of the mandatory-y mechanism.

um is not forced to include mandatory-y since it is a very exceptional
case which does not support UAPI.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

During a simple no-op (nothing changed) build I saw 39 invocations of
the C compiler with the argument "-print-file-name=include".  We don't
need to call the C compiler 39 times for this--one time will suffice.

Let's change NOSTDINC_FLAGS to a simply expanded variable to avoid
this since there doesn't appear to be any reason it should be
recursively expanded.

On my build this shaved ~400 ms off my "no-op" build.

Note that the recursive expansion seems to date back to the (really
old) commit e8f5bdb02ce0 ("[PATCH] Makefile include path ordering").
It's a little unclear to me if the point of that patch was to switch
the variable to be recursively expanded (which it did) or to avoid
directly assigning to NOSTDINC_FLAGS (AKA to switch to +=) because
someone else (out of tree?) was setting it.  I presume later since if
the only goal was to switch to recursive expansion the patch would
have just removed the ":".

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Since commit 3812b8c5c5d5 ("kbuild: make -r/-R effective in top
Makefile for old Make versions"), make-kpkg is not working.

make-kpkg directly includes the top Makefile of Linux kernel, and
appends some debian_* targets.

  /usr/share/kernel-package/ruleset/kernel_version.mk:

    # Include the kernel makefile
    override dot-config := 1
    include Makefile
    dot-config := 1

I did not know the kernel Makefile was used in that way, and it is
hard to guarantee the behavior when the kernel Makefile is included
by another Makefile from a different project.

It looks like Debian Stretch stopped providing make-kpkg. Maybe it is
obsolete and being replaced with 'make deb-pkg' etc. but still widely
used.

This commit adds a workaround; if the top Makefile is included by
another Makefile, skip sub-make in order to make the main part visible.
'MAKEFLAGS += -rR' does not become effective for GNU Make < 4.0, but
Debian/Ubuntu is already using newer versions.

The effect of this commit:

  Debian 8 (Jessie)  : Fixed
  Debian 9 (Stretch) : make-kpkg (kernel-package) is not provided
  Ubuntu 14.04 LTS   : NOT Fixed
  Ubuntu 16.04 LTS   : Fixed
  Ubuntu 18.04 LTS   : Fixed

This commit cannot fix Ubuntu 14.04 because it installs GNU Make 3.81,
but its support will end in Apr 2019, which is before the Linux v5.1
release.

I added warning so that nobody would try to include the top Makefile.

Fixes: 3812b8c5c5d5 ("kbuild: make -r/-R effective in top Makefile for old Make versions")
Reported-by: Liz Zhang <lizzha@microsoft.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Lili Deng <v-lide@microsoft.com>
Cc: Manoj Srivastava <srivasta@debian.org>

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
  ...

Pull driver core updates from Greg KH:
 "Here is the big driver core patchset for 5.1-rc1

  More patches than "normal" here this merge window, due to some work in
  the driver core by Alexander Duyck to rework the async probe
  functionality to work better for a number of devices, and independant
  work from Rafael for the device link functionality to make it work
  "correctly".

  Also in here is:

   - lots of BUS_ATTR() removals, the macro is about to go away

   - firmware test fixups

   - ihex fixups and simplification

   - component additions (also includes i915 patches)

   - lots of minor coding style fixups and cleanups.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'driver-core-5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (65 commits)
  driver core: platform: remove misleading err_alloc label
  platform: set of_node in platform_device_register_full()
  firmware: hardcode the debug message for -ENOENT
  driver core: Add missing description of new struct device_link field
  driver core: Fix PM-runtime for links added during consumer probe
  drivers/component: kerneldoc polish
  async: Add cmdline option to specify drivers to be async probed
  driver core: Fix possible supplier PM-usage counter imbalance
  PM-runtime: Fix __pm_runtime_set_status() race with runtime resume
  driver: platform: Support parsing GpioInt 0 in platform_get_irq()
  selftests: firmware: fix verify_reqs() return value
  Revert "selftests: firmware: remove use of non-standard diff -Z option"
  Revert "selftests: firmware: add CONFIG_FW_LOADER_USER_HELPER_FALLBACK to config"
  device: Fix comment for driver_data in struct device
  kernfs: Allocating memory for kernfs_iattrs with kmem_cache.
  sysfs: remove unused include of kernfs-internal.h
  driver core: Postpone DMA tear-down until after devres release
  driver core: Document limitation related to DL_FLAG_RPM_ACTIVE
  PM-runtime: Take suppliers into account in __pm_runtime_set_status()
  device.h: Add __cold to dev_<level> logging functions
  ...

This build rule was introduced by commit cd05e6bdc600 ("[PATCH]
kbuild: fix split-include dependency") to handle the dependency of
scripts/basic/split-include.

Now, fixdep is the only tool in scripts/basic/, and this rule is
no longer used.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The flag '-Werror-implicit-function-declaration', present in GCC 2.95,
stopped to be documented in GCC 4.3, replaced by the more generic
'-Werror=...' form.

So, use the equivalent '-Werror=implicit-function-declaration' instead.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This code has been commented out since commit b7000adef17a
("Don't set the INITRD_COMPRESS environment variable automatically").

Clean it up now.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>