We've missed the dependency to rsync, so build fails on
minimal containers.

Fixes: 59b2bd05f5f4 ("kbuild: add 'headers' target to build up uapi headers in usr/include")
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Add a 'dir-pkg' target which just creates the same directory structures
as in tar-pkg, but doesn't package anything.
Useful when the user wants to copy the kernel tree on a machine using
ssh, rsync or whatever.

Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/package/Makefile does not use $(obj) or $(src) at all.
It actually generates files and directories in the top of $(objtree).
I do not see much sense in descending into scripts/package/.

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

These are not real targets. Adding them to PHONY is preferred.

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

I am not a big fan of the $(objtree)/ hack for clean-files/clean-dirs.

These are created in the top of $(objtree), so let's clean them up
from the top Makefile.

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

While descending directories, Kbuild produces objects for modules,
but do not link final *.ko files; it is done in the modpost.

To keep track of modules, Kbuild creates a *.mod file in $(MODVERDIR)
for every module it is building. Some post-processing steps read the
necessary information from *.mod files. This avoids descending into
directories again. This mechanism was introduced in 2003 or so.

Later, commit 551559e13af1 ("kbuild: implement modules.order") added
modules.order. So, we can simply read it out to know all the modules
with directory paths. This is easier than parsing the first line of
*.mod files.

$(MODVERDIR) has a flat directory structure, that is, *.mod files
are named only with base names. This is based on the assumption that
the module name is unique across the tree. This assumption is really
fragile.

Stephen Rothwell reported a race condition caused by a module name
conflict:

  https://lkml.org/lkml/2019/5/13/991

In parallel building, two different threads could write to the same
$(MODVERDIR)/*.mod simultaneously.

Non-unique module names are the source of all kind of troubles, hence
commit 3a48a91901c5 ("kbuild: check uniqueness of module names")
introduced a new checker script.

However, it is still fragile in the build system point of view because
this race happens before scripts/modules-check.sh is invoked. If it
happens again, the modpost will emit unclear error messages.

To fix this issue completely, create *.mod with full directory path
so that two threads never attempt to write to the same file.

$(MODVERDIR) is no longer needed.

Since modules with directory paths are listed in modules.order, Kbuild
is still able to find *.mod files without additional descending.

I also killed cmd_secanalysis; scripts/mod/sumversion.c computes MD4 hash
for modules with MODULE_VERSION(). When CONFIG_DEBUG_SECTION_MISMATCH=y,
it occurs not only in the modpost stage, but also during directory
descending, where sumversion.c may parse stale *.mod files. It would emit
'No such file or directory' warning when an object consisting a module is
renamed, or when a single-obj module is turned into a multi-obj module or
vice versa.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Nicolas Pitre <nico@fluxnic.net>

Debian-based distributions place libc header files in a machine
specific directory (/usr/include/<libc-machine>) instead of
/usr/include/asm to support installation of the linux-libc-dev
package from multiple architectures. Move headers installed by
"make headers_install" accordingly using Debian's tuple from
dpkg-architecture (stored in debian/arch).

Signed-off-by: Cedric Hombourger <Cedric_Hombourger@mentor.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

header-test-y does not work with headers in sub-directories.

For example, you may want to write a Makefile, like this:

include/linux/Kbuild:

  header-test-y += mtd/nand.h

This entry will create a wrapper include/linux/mtd/nand.hdrtest.c
with the following content:

  #include "mtd/nand.h"

To make this work, we need to add $(srctree)/include/linux to the
header search path. It would be tedious to add ccflags-y.

Instead, we could change the *.hdrtest.c rule to wrap:

  #include "nand.h"

This works for in-tree build since #include "..." searches in the
relative path from the header with this directive. For O=... build,
we need to add $(srctree)/include/linux/mtd to the header search path,
which will be even more tedious.

After all, I thought it would be handier to compile headers directly
without creating wrappers.

I added a new build rule to compile %.h into %.h.s

The target is %.h.s instead of %.h.o because it is slightly faster.
Also, as for GCC, an empty assembly is smaller than an empty object.

I wrote the build rule:

  $(CC) $(c_flags) -S -o $@ -x c /dev/null -include $<

instead of:

  $(CC) $(c_flags) -S -o $@ -x c $<

Both work fine with GCC, but the latter is bad for Clang.

This comes down to the difference in the -Wunused-function policy.
GCC does not warn about unused 'static inline' functions at all.
Clang does not warn about the ones in included headers, but does
about the ones in the source. So, we should handle headers as
headers, not as source files.

In fact, this has been hidden since commit abb2ea7dfd82 ("compiler,
clang: suppress warning for unused static inline functions"), but we
should not rely on that.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Jani Nikula <jani.nikula@intel.com>

It is absolutely fine to add extra sanity checks in package scripts,
but it is not necessary to do so.

This is already covered by the daily compile-testing (0day bot etc.)
because headers_check is run as a part of the normal build process
when CONFIG_HEADERS_CHECK=y.

Replace it with the newly-added "make headers".

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

The buildtar script might want to invoke a make, so tell the parent
make to pass the jobserver token pipe to the subcommand by prefixing
the command with a +.

This addresses the issue seen here:

  /bin/sh ../scripts/package/buildtar tar-pkg
  make[3]: warning: jobserver unavailable: using -j1.  Add '+' to parent make rule.

See https://www.gnu.org/software/make/manual/html_node/Job-Slots.html
for more information.

Signed-off-by: Trevor Bourget <tgb.kernel@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>