In order to preserve backwards compatability with kmod tools, we have to
move the namespace field in Module.symvers last, as the depmod -e -E
option looks at the first three fields in Module.symvers to check symbol
versions (and it's expected they stay in the original order of crc,
symbol, module).

In addition, update an ancient comment above read_dump() in modpost that
suggested that the export type field in Module.symvers was optional. I
suspect that there were historical reasons behind that comment that are
no longer accurate. We have been unconditionally printing the export
type since 2.6.18 (commit bd5cbcedf44), which is over a decade ago now.

Fix up read_dump() to treat each field as non-optional. I suspect the
original read_dump() code treated the export field as optional in order
to support pre <= 2.6.18 Module.symvers (which did not have the export
type field). Note that although symbol namespaces are optional, the
field will not be omitted from Module.symvers if a symbol does not have
a namespace. In this case, the field will simply be empty and the next
delimiter or end of line will follow.

Cc: stable@vger.kernel.org
Fixes: cb9b55d21fe0 ("modpost: add support for symbol namespaces")
Tested-by: Matthias Maennich <maennich@google.com>
Reviewed-by: Matthias Maennich <maennich@google.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

All the files in Documentation/kbuild/ were converted to reST.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

obj-* needs a trailing slash for a directory, but subdir-* does not.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

This sentence does not make sense in the section about mandatory-y.

This seems to be a copy-paste mistake of commit fcc8487d477a ("uapi:
export all headers under uapi directories").

The correct description would be "The convention is to list one
mandatory-y per line ...".

I just removed it instead of fixing it. If such information is needed,
it could be commented in include/asm-generic/Kbuild and
include/uapi/asm-generic/Kbuild.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

In old days, the "host-progs" syntax was used for specifying host
programs. It was renamed to the current "hostprogs-y" in 2004.

It is typically useful in scripts/Makefile because it allows Kbuild to
selectively compile host programs based on the kernel configuration.

This commit renames like follows:

  always       ->  always-y
  hostprogs-y  ->  hostprogs

So, scripts/Makefile will look like this:

  always-$(CONFIG_BUILD_BIN2C) += ...
  always-$(CONFIG_KALLSYMS)    += ...
      ...
  hostprogs := $(always-y) $(always-m)

I think this makes more sense because a host program is always a host
program, irrespective of the kernel configuration. We want to specify
which ones to compile by CONFIG options, so always-y will be handier.

The "always", "hostprogs-y", "hostprogs-m" will be kept for backward
compatibility for a while.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

The difference between "always" and "extra-y" is that the targets
listed in $(always) are always built, whereas the ones in $(extra-y)
are built only when KBUILD_BUILTIN is set.

So, "make modules" does not build the targets in $(extra-y).

vmlinux.lds is only needed for linking vmlinux. So, adding it to extra-y
is more correct. In fact, arch/x86/kernel/Makefile does this.

Fix the example code.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Pull Kconfig updates from Masahiro Yamada:

 - add 'yes2modconfig' and 'mod2yesconfig' targets (useful mainly for
   turning syzbot configs into more modular ones as a step to minimizing
   the result)

 - sanitize help text

 - various code cleanups

* tag 'kconfig-v5.6' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kconfig: fix documentation typos
  kconfig: fix an "implicit declaration of function" warning
  kconfig: fix nesting of symbol help text
  kconfig: distinguish between dependencies and visibility in help text
  kconfig: list all definitions of a symbol in help text
  kconfig: Add yes2modconfig and mod2yesconfig targets.
  kconfig: use $(PERL) in Makefile
  kconfig: fix too deep indentation in Makefile
  kconfig: localmodconfig: fix indentation for closing brace
  kconfig: localmodconfig: remove unused $config
  kconfig: squash prop_alloc() into menu_add_prop()
  kconfig: remove sym from struct property
  kconfig: remove 'prompt' argument from menu_add_prop()
  kconfig: move prompt handling to menu_add_prompt() from menu_add_prop()
  kconfig: remove 'prompt' symbol
  kconfig: drop T_WORD from the RHS of 'prompt' symbol
  kconfig: use parent->dep as the parentdep of 'menu'
  kconfig: remove the rootmenu check in menu_add_prop()

Fix a couple typos in kconfig-language documentation.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Commit bc081dd6e9f6 ("kbuild: generate modules.builtin") added
infrastructure to generate modules.builtin, the list of all
builtin modules.

Basically, it works like this:

  - Kconfig generates include/config/tristate.conf, the list of
    tristate CONFIG options with a value in a capital letter.

  - scripts/Makefile.modbuiltin makes Kbuild descend into
    directories to collect the information of builtin modules.

I am not a big fan of it because Kbuild ends up with traversing
the source tree twice.

I am not sure how perfectly it should work, but this approach cannot
avoid false positives; even if the relevant CONFIG option is tristate,
some Makefiles forces obj-m to obj-y.

Some examples are:

  arch/powerpc/platforms/powermac/Makefile:
    obj-$(CONFIG_NVRAM:m=y)         += nvram.o

  net/ipv6/Makefile:
    obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o

  net/netlabel/Makefile:
    obj-$(subst m,y,$(CONFIG_IPV6)) += netlabel_calipso.o

Nobody has complained about (or noticed) it, so it is probably fine to
have false positives in modules.builtin.

This commit simplifies the implementation. Let's exploit the fact
that every module has MODULE_LICENSE(). (modpost shows a warning if
MODULE_LICENSE is missing. If so, 0-day bot would already have blocked
such a module.)

I added MODULE_FILE to <linux/module.h>. When the code is being compiled
as builtin, it will be filled with the file path of the module, and
collected into modules.builtin.info. Then, scripts/link-vmlinux.sh
extracts the list of builtin modules out of it.

This new approach fixes the false-positives above, but adds another
type of false-positives; non-modular code may have MODULE_LICENSE()
by mistake. This is not a big deal, it is just the code is always
orphan. We can clean it up if we like. You can see cleanup examples by:

  $ git log --grep='make.* explicitly non-modular'

To sum up, this commits deletes lots of code, but still produces almost
equivalent results. Please note it does not increase the vmlinux size at
all. As you can see in include/asm-generic/vmlinux.lds.h, the .modinfo
section is discarded in the link stage.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Kbuild descends into a directory by either 'y' or 'm', but there is an
important difference.

Kbuild combines the built-in objects into built-in.a in each directory.
The built-in.a in the directory visited by obj-y is merged into the
built-in.a in the parent directory. This merge happens recursively
when Kbuild is ascending back towards the top directory, then built-in
objects are linked into vmlinux eventually. This works properly only
when the Makefile specifying obj-y is reachable by the chain of obj-y.

On the other hand, Kbuild does not take built-in.a from the directory
visited by obj-m. This it, all the objects in that directory are
supposed to be modular. If Kbuild descends into a directory by obj-m,
but the Makefile in the sub-directory specifies obj-y, those objects
are just left orphan.

The current statement "Kbuild only uses this information to decide that
it needs to visit the directory" is misleading. Clarify the difference.

Reported-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Johan Hovold <johan@kernel.org>