kbuild: deb-pkg: call more misc debhelper commands

Use dh_prep instead of removing old build directories manually.

Use dh_clean instead of removing build directories and debian/files
manually.

Call dh_testdir and dh_testroot for preliminary checks.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: build binary-arch in parallel

'make deb-pkg' builds build-arch in parallel, but binary-arch serially.

Given that all binary packages are independent of one another, they can
be built in parallel.

I am uncertain whether debian/files is robust against a race condition.
Just in case, make dh_gencontrol (dpkg-gencontrol) output to separate
debian/*.files, which are then concatenated into debian/files.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: make debian/rules quiet for 'make deb-pkg'

Add $(Q) to the commands in debian/rules to make them quiet when the
package built is initiated by 'make deb-pkg' or when the 'terse' tag
is set to DEB_BUILD_OPTIONS.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: show verbose log for direct package builds

When the Debian package build is initiated by Kbuild ('make deb-pkg'
or 'make bindeb-pkg'), the log messages are displayed in the short
form, which is the Kbuild default.

Otherwise, let's show verbose messages (unless the 'terse' tag is set
in DEB_BUILD_OPTION), as suggested by Debian Policy: "The package build
should be as verbose as reasonably possible, except where the terse tag
is included in DEB_BUILD_OPTIONS." [1]

This is what the Debian kernel also does. [2]

[1]: https://www.debian.org/doc/debian-policy/ch-source.html#main-building-script-debian-rules
[2]: https://salsa.debian.org/kernel-team/linux/-/blob/debian/6.7-1_exp1/debian/rules.real#L36

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: move 'make headers' to build-arch

Strictly speaking, 'make headers' should be a part of build-arch
instead of binary-arch.

'make headers' constructs ready-to-copy UAPI headers in the kernel
directory.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: use more debhelper commands in builddeb

Commit 36862e14e316 ("kbuild: deb-pkg: use dh_listpackages to know
enabled packages") started to require the debhelper tool suite.

Use more dh_* commands in create_package():

- dh_installdocs to install copyright
- dh_installchangelogs to install changelog
- dh_compress to compress changelog
- dh_fixperms to replace the raw chmod command
- dh_gencontrol to replace the raw dpkg-gencontrol command
- dh_md5sums to record the md5sum of included files
- dh_builddeb to replace the raw dpkg-deb command

Set DEB_RULES_REQUIRES_ROOT to 'no' in case debian/rules is executed
directly.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: remove unneeded '-f $srctree/Makefile' in debian/rules

This is unneeded because the Makefile in the output directory wraps
the top-level Makefile in the srctree.

Just run $(MAKE) irrespective of the build location.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: allow to run debian/rules from output directory

'make O=... deb-pkg' creates the debian directory in the output
directory. However, currently it is impossible to run debian/rules
created in the separate output directory.

This commit delays the $(srctree) expansion by escaping '$' and by
quoting the entire command, making it possible to run debian/rules in
the output directory.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: set DEB_* variables if debian/rules is directly executed

Since commit 491b146d4c13 ("kbuild: builddeb: Eliminate debian/arch
use"), direct execution of debian/rules results in the following error:

dpkg-architecture: error: unknown option 'DEB_HOST_MULTIARCH'

The current code:

dpkg-architecture -a$DEB_HOST_ARCH -qDEB_HOST_MULTIARCH

... does not look sensible because:

- For this code to work correctly, DEB_HOST_ARCH must be pre-defined,
which is true when the packages are built via dpkg-buildpackage.
In this case, DEB_HOST_MULTIARCH is also likely defined, hence there
is no need to query DEB_HOST_MULTIARCH in the first place.

- If DEB_HOST_MULTIARCH is undefined, DEB_HOST_ARCH is likely undefined
too. So, you cannot query DEB_HOST_MULTIARCH in this way. This is
mostly the case where debian/rules is directly executed.

When debian/rules is directly executed, querying DEB_HOST_MUCHARCH is
not enough because we need to know DEB_{BUILD,HOST}_GNU_TYPE as well.

All DEB_* variables are defined when the package build is initiated by
dpkg-buildpackage, but otherwise, let's call dpkg-architecture to set
all DEB_* environment variables.

This requires dpkg 1.20.6 or newer because --print-format option
was added in dpkg commit 7c54fa2b232e ("dpkg-architecture: Add a
--print-format option").

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: squash scripts/package/deb-build-option to debian/rules

The binary-arch target needs to use the same CROSS_COMPILE as used in
build-arch; otherwise, 'make run-command' may attempt to resync the
.config file.

Squash scripts/package/deb-build-option into debian/rules, as it is a
small amount of code.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: factor out common Make options in debian/rules

This avoids code duplication between binary-arch and built-arch.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

kbuild: deb-pkg: support DEB_BUILD_OPTIONS=parallel=N in debian/rules

'make srcdeb-pkg' generates a source package, which you can build
later by using dpkg-buildpackage.

In older dpkg versions, 'dpkg-buildpackage --jobs=N' sets not only
DEB_BUILD_OPTIONS but also MAKEFLAGS. Hence, passing -j or --jobs
to dpkg-buildpackage was enough for kicking the parallel execution.

The behavior was changed by commit 1d0ea9b2ba3f ("dpkg-buildpackage:
Change -j, --jobs semantics to non-force mode") of dpkg project. [1]

Since then, 'dpkg-buildpackage --jobs=N' sets only DEB_BUILD_OPTIONS,
which is not parsed by the current debian/rules. To build the package
in parallel, you need to pass the alternative --jobs-force option or
set the MAKEFLAGS environment variable.

Debian policy [2] suggests the following code snippet for debian/rules.

ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
MAKEFLAGS += -j$(NUMJOBS)
endif

I tweaked the code to filter out parallel=1 and passed --jobs=1 to
dpkg-buildpackage from scripts/Makefile.package. It is needed to force
'make deb-pkg' without the -j option to run in serial. Please note that
dpkg-buildpackage sets parallel=<nproc> in DEB_BUILD_OPTIONS by default
(that is, --jobs=auto is the default) and --jobs=1 is needed to restore
the serial execution. When dpkg-buildpackage is invoked from Kbuild,
the number of jobs is inherited from the top level Makefile. Passing
--jobs=1 to dpkg-buildpackage allows debian/rules to skip parsing
DEB_BUILD_OPTIONS.

[1] https://salsa.debian.org/dpkg-team/dpkg/-/commit/1d0ea9b2ba3f6a2de5b1a6ff55f3df7b71f73db6
[2] https://www.debian.org/doc/debian-policy/ch-source.html#s-debianrules-options

Reported-by: Bastian Germann <bage@linutronix.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

kbuild: deb-pkg: split debian/rules

debian/rules is generated by shell, but the escape sequence (\$) is
unreadable.

debian/rules embeds only two variables (ARCH and KERNELRELEASE).

Split them out to debian/rules.vars, and check-in the rest of Makefile
code to scripts/package/debian/rules.

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