Commit 2b50f7ab authored by Masahiro Yamada's avatar Masahiro Yamada

kbuild: add workaround for Debian make-kpkg

Since commit 3812b8c5 ("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 Maybe it is
obsolete and being replaced with 'make deb-pkg' etc.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: 3812b8c5 ("kbuild: make -r/-R effective in top Makefile for old Make versions")
Reported-by: 's avatarLiz Zhang <lizzha@microsoft.com>
Signed-off-by: 's avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: 's avatarLili Deng <v-lide@microsoft.com>
Cc: Manoj Srivastava <srivasta@debian.org>
parent 94cf8acc
......@@ -31,6 +31,16 @@ _all:
# descending is started. They are now explicitly listed as the
# prepare rule.
# Ugly workaround for Debian make-kpkg:
# make-kpkg directly includes the top Makefile of Linux kernel. In such a case,
# skip sub-make to support debian_* targets in ruleset/kernel_version.mk, but
# displays warning to discourage such abusage.
ifneq ($(word 2, $(MAKEFILE_LIST)),)
$(warning Do not include top Makefile of Linux Kernel)
sub-make-done := 1
MAKEFLAGS += -rR
endif
ifneq ($(sub-make-done),1)
# Do not use make's built-in rules and variables
......
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