Arnd Bergmann reported false-positive modpost warnings detected by his
randconfig testing of linux-next.

Actually, this happens under the combination of CONFIG_MODVERSIONS
and CONFIG_TRIM_UNUSED_KSYMS since commit 15bfc234 ("modpost:
check for static EXPORT_SYMBOL* functions").

For example, arch/arm/config/multi_v7_defconfig + CONFIG_MODVERSIONS
+ CONFIG_TRIM_UNUSED_KSYMS produces the following false-positives:

WARNING: "__lshrdi3" [vmlinux] is a static (unknown)
WARNING: "__ashrdi3" [vmlinux] is a static (unknown)
WARNING: "__aeabi_lasr" [vmlinux] is a static (unknown)
WARNING: "__aeabi_llsr" [vmlinux] is a static (unknown)
WARNING: "ftrace_set_clr_event" [vmlinux] is a static (unknown)
WARNING: "__muldi3" [vmlinux] is a static (unknown)
WARNING: "__aeabi_ulcmp" [vmlinux] is a static (unknown)
WARNING: "__ucmpdi2" [vmlinux] is a static (unknown)
WARNING: "__aeabi_lmul" [vmlinux] is a static (unknown)
WARNING: "__bswapsi2" [vmlinux] is a static (unknown)
WARNING: "__bswapdi2" [vmlinux] is a static (unknown)
WARNING: "__ashldi3" [vmlinux] is a static (unknown)
WARNING: "__aeabi_llsl" [vmlinux] is a static (unknown)

The root cause of the problem is not in the modpost, but in the
implementation of CONFIG_TRIM_UNUSED_KSYMS.

If there is at least one untrimmed symbol in the file, genksyms is
invoked to calculate CRC of *all* the exported symbols in that file
even if some of them have been trimmed due to no caller existing.

As a result, .tmp_*.ver files contain CRC of trimmed symbols, thus
unneeded, orphan __crc* symbols are added to objects. It had been
harmless until recently.

With commit 15bfc234 ("modpost: check for static EXPORT_SYMBOL*
functions"), it is now harmful because the bogus __crc* symbols make
modpost call sym_update_crc() to add the symbols to the hash table,
but there is no one that clears the ->is_static member.

I gave Fixes to the first commit that uncovered the issue, but the
potential problem has long existed since commit f2355416
("export.h: allow for per-symbol configurable EXPORT_SYMBOL()").

Fixes: 15bfc234 ("modpost: check for static EXPORT_SYMBOL* functions")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Arnd Bergmann <arnd@arndb.de>

The conditional, define(__KERNEL__), was added by commit f2355416
("export.h: allow for per-symbol configurable EXPORT_SYMBOL()").

It was needed at that time to avoid the build error of modpost
with CONFIG_TRIM_UNUSED_KSYMS=y.

Since commit b2c5cdcf ("modpost: remove symbol prefix support"),
modpost no longer includes linux/export.h, thus the define(__KERNEL__)
is unneeded.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Nicolas Pitre <nico@fluxnic.net>

GCC and Clang have different policy for -Wunused-function; GCC does not
warn unused static inline functions at all whereas Clang does if they
are defined in source files instead of included headers although it has
been suppressed since commit abb2ea7d ("compiler, clang: suppress
warning for unused static inline functions").

We often miss to delete unused functions where 'static inline' is used
in *.c files since there is no tool to detect them. Unused code remains
until somebody notices. For example, commit 075ddd75 ("regulator:
core: remove unused rdev_get_supply()").

Let's remove __maybe_unused from the inline macro to allow Clang to
start finding unused static inline functions. For now, we do this only
for W=1 build since it is not a good idea to sprinkle warnings for the
normal build (e.g. 35 warnings for arch/x86/configs/x86_64_defconfig).

My initial attempt was to add -Wno-unused-function for no W= build
(https://lore.kernel.org/patchwork/patch/1120594/)

Nathan Chancellor pointed out that would weaken Clang's checks since
we would no longer get -Wunused-function without W=1. It is true GCC
would catch unused static non-inline functions, but it would weaken
Clang as a standalone compiler, at least.

Hence, here is a counter implementation. The current problem is, W=...
only controls compiler flags, which are globally effective. There is
no way to address only 'static inline' functions.

This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123].
When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from
the 'inline' macro.

The new macro __inline_maybe_unused makes the code a bit uglier, so I
hope we can remove it entirely after fixing most of the warnings.

If you contribute to code clean-up, please run "make CC=clang W=1"
and check -Wunused-function warnings. You will find lots of unused
functions.

Some of them are false-positives because the call-sites are disabled
by #ifdef. I do not like to abuse the inline keyword for suppressing
unused-function warnings because it is intended to be a hint for the
compiler optimization. I prefer #ifdef around the definition, or
__maybe_unused if #ifdef would make the code too ugly.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>

KBUILD_ENABLE_EXTRA_GCC_CHECKS started as a switch to add extra warning
options for GCC, but now it is a historical misnomer since we use it
also for Clang, DTC, and even kernel-doc.

Rename it to more sensible, shorter KBUILD_EXTRA_WARN.

For the backward compatibility, KBUILD_ENABLE_EXTRA_GCC_CHECKS is still
supported (but not advertised in the documentation).

I also fixed up 'make help', and updated the documentation.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>

Instead of the warning-[123] magic, let's accumulate compiler options
to KBUILD_CFLAGS directly as the top Makefile does. I think this makes
it easier to understand what is going on in this file.

This commit slightly changes the behavior, I think all of which are OK.

[1] Currently, cc-option calls are needlessly evaluated. For example,
      warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
    needs evaluating only when W=3, but it is actually evaluated for
    W=1, W=2 as well. With this commit, only relevant cc-option calls
    will be evaluated. This is a slight optimization.

[2] Currently, unsupported level like W=4 is checked by:
      $(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
    This will no longer be checked, but I do not think it is a big
    deal.

[3] Currently, 4 Clang warnings (Winitializer-overrides, Wformat,
    Wsign-compare, Wformat-zero-length) are shown by any of W=1, W=2,
    and W=3. With this commit, they will be warned only by W=1. I
    think this is a more correct behavior since each warning belongs
    to only one group.

For understanding this commit correctly:

We have 3 warning groups, W=1, W=2, and W=3. You may think W=3 has a
higher level than W=1, but they are actually independent. If you like,
you can combine them like W=13. To enable all the warnings, you can
pass W=123. It is shown by 'make help', but not noticed much. Since we
support W= combination, there should not exist intersection among the
three groups. If we enable Winitializer-overrides for W=1, we do not
need to for W=2 or W=3. This is the reason why I think the change [3]
makes sense.

The documentation says -Winitializer-overrides is enabled by default.
(https://clang.llvm.org/docs/DiagnosticsReference.html#winitializer-overrides)
We negate it by passing -Wno-initializer-overrides for the normal
build, but we do not do that for W=1. This means, W=1 effectively
enables -Winitializer-overrides by the clang's default. The same for
the other three.

Add comments in case people are confused with the code.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

The merge_config.sh script verifies that all the config options have
their expected value in the resulting file and prints any issues as
warnings.  These checks aren't intended to be treated as errors given
the current implementation.  However, since "set -e" was added, if the
grep command to look for a config option does not find it the script
will then abort prematurely.

Handle the case where the grep exit status is non-zero by setting
ACTUAL_VAL to an empty string to restore previous functionality.

Fixes: cdfca821 ("merge_config.sh: Check error codes from make")
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Kbuild provides per-file compiler flag addition/removal:

  CFLAGS_<basetarget>.o
  CFLAGS_REMOVE_<basetarget>.o
  AFLAGS_<basetarget>.o
  AFLAGS_REMOVE_<basetarget>.o
  CPPFLAGS_<basetarget>.lds
  HOSTCFLAGS_<basetarget>.o
  HOSTCXXFLAGS_<basetarget>.o

The <basetarget> is the filename of the target with its directory and
suffix stripped.

This syntax comes into a trouble when two files with the same basename
appear in one Makefile, for example:

  obj-y += foo.o
  obj-y += dir/foo.o
  CFLAGS_foo.o := <some-flags>

Here, the <some-flags> applies to both foo.o and dir/foo.o

The real world problem is:

  scripts/kconfig/util.c
  scripts/kconfig/lxdialog/util.c

Both files are compiled into scripts/kconfig/mconf, but only the
latter should be given with the ncurses flags.

It is more sensible to use the relative path to the Makefile, like this:

  obj-y += foo.o
  CFLAGS_foo.o := <some-flags>
  obj-y += dir/foo.o
  CFLAGS_dir/foo.o := <other-flags>

At first, I attempted to replace $(basetarget) with $*. The $* variable
is replaced with the stem ('%') part in a pattern rule. This works with
most of cases, but does not for explicit rules.

For example, arch/ia64/lib/Makefile reuses rule_as_o_S in its own
explicit rules, so $* will be empty, resulting in ignoring the per-file
AFLAGS.

I introduced a new variable, target-stem, which can be used also from
explicit rules.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Marc Zyngier <maz@kernel.org>

Add NOFAIL check for the strndup call, because the function
allocates memory and can return NULL. All calls to strdup in
modpost are checked with NOFAIL.
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Since guid_t is the recommended data type for UUIDs in
kernel (and I guess uuid_le is meant to be ultimately
replaced with it), it should be made available here as
well.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

CONFIG_SHELL falls back to sh when bash is not installed on the system,
but nobody is testing such a case since bash is usually installed.
So, shell scripts invoked by CONFIG_SHELL are only tested with bash.

It makes it difficult to test whether the hashbang #!/bin/sh is real.
For example, #!/bin/sh in arch/powerpc/kernel/prom_init_check.sh is
false. (I fixed it up)

Besides, some shell scripts invoked by CONFIG_SHELL use bash-extension
and #!/bin/bash is specified as the hashbang, while CONFIG_SHELL may
not always be set to bash.

Probably, the right thing to do is to introduce BASH, which is bash by
default, and always set CONFIG_SHELL to sh. Replace $(CONFIG_SHELL)
with $(BASH) for bash scripts.

If somebody tries to add bash-extension to a #!/bin/sh script, it will
be caught in testing because /bin/sh is a symlink to dash on some major
distributions.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

These flags were added by commit 61754c18 ("kbuild: Allow arch
Makefiles to override {cpp,ld,c}flags") to allow ARC to override -O2.

We did not see any other usage after all. Now that ARC switched to
CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3, there is no more user of
these variables.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arc/Makefile overrides -O2 with -O3. This is the only user of
ARCH_CFLAGS. There is no user of ARCH_CPPFLAGS or ARCH_AFLAGS.
My plan is to remove ARCH_{CPP,A,C}FLAGS after refactoring the ARC
Makefile.

Currently, ARC has no way to enable -Wmaybe-uninitialized because both
-O3 and -Os disable it. Enabling it will be useful for compile-testing.
This commit allows allmodconfig (, which defaults to -O2) to enable it.

Add CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3=y to all the defconfig files
in arch/arc/configs/ in order to keep the current config settings.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com>

This functionally reverts commit bfd77145 ("Makefile: Convert
-Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang").

clang enabled support for -Wimplicit-fallthrough in C in r369414 [1],
which causes a lot of warnings when building the kernel for two reasons:

1. Clang does not support the /* fall through */ comments. There seems
   to be a general consensus in the LLVM community that this is not
   something they want to support. Joe Perches wrote a script to convert
   all of the comments to a "fallthrough" keyword that will be added to
   compiler_attributes.h [2] [3], which catches the vast majority of the
   comments. There doesn't appear to be any consensus in the kernel
   community when to do this conversion.

2. Clang and GCC disagree about falling through to final case statements
   with no content or cases that simply break:

   https://godbolt.org/z/c8csDu

   This difference contributes at least 50 warnings in an allyesconfig
   build for x86, not considering other architectures. This difference
   will need to be discussed to see which compiler is right [4] [5].

[1]: https://github.com/llvm/llvm-project/commit/1e0affb6e564b7361b0aadb38805f26deff4ecfc
[2]: https://lore.kernel.org/lkml/61ddbb86d5e68a15e24ccb06d9b399bbf5ce2da7.camel@perches.com/
[3]: https://lore.kernel.org/lkml/1d2830aadbe9d8151728a7df5b88528fc72a0095.1564549413.git.joe@perches.com/
[4]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91432
[5]: https://github.com/ClangBuiltLinux/linux/issues/636

Given these two problems need discussion and coordination, do not enable
-Wimplicit-fallthrough with clang right now. Add a comment to explain
what is going on as well. This commit should be reverted once these two
issues are fully flushed out and resolved.
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

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

This '+' was added a long time ago:

| commit c23e6bf0 (HEAD)
| Author: Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de>
| Date:   Mon Oct 28 01:16:34 2002 -0600
|
|     kbuild: Fix a "make -j<N>" warning
|
| diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
| index 2c843e0380bc..e7c392fd5788 100644
| --- a/scripts/Makefile.clean
| +++ b/scripts/Makefile.clean
| @@ -42,7 +42,7 @@ quiet_cmd_clean = CLEAN   $(obj)
|
|  __clean: $(subdir-ymn)
|  ifneq ($(strip $(__clean-files) $(clean-rule)),)
| -        $(call cmd,clean)
| +        +$(call cmd,clean)
|  else
|          @:
|  endif

At that time, cmd_clean contained $(clean-rule), which was able to
invoke sub-make. That was why cleaning with the -j option showed:
warning: jobserver unavailable: using -j1.  Add '+' to parent make rule.

It is not the case any more; cmd_clean now just runs the 'rm' command.
The '+' marker is pointless.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The only the difference between clean-files and clean-dirs is the -r
option passed to the 'rm' command.

You can always pass -r, and then remove the clean-dirs syntax.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Move the outputmakefile target to the leftmost in the prerequisite list
so that this is checked first. GNU Make processes the prerequisites
left to right.

GNU Make will keep to stick to this behavior, and it seems even
POSIX standard, according to this:
https://lists.gnu.org/archive/html/bug-make/2019-08/msg00030.html

The POSIX standard of make is available here:
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/make.html

Of course, when the parallel option -j given, other targets will be run
simultaneously but it is nice to show the error as early as possible.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Now prepare3 does nothing but depends on include/config/kernel.release
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

With this commit, the error report is shown earlier, even before
running kconfig.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

If you try out-of-tree build with an unclean source tree, Kbuild
suggests to run make mrproper. The path to the source tree may be
shown with a relative path, for example, "make O=foo" emits the
following:

  .. is not clean, please run 'make mrproper'
  in the '..' directory.

This is somewhat confusing if you ran "make O=foo" in the source tree.
Using the absolute path will be clearer.

This commit changes the error message like follows:

***
*** The source tree is not clean, please run 'make mrproper'
*** in /absolute/path/to/linux
***
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Since commit 3a475b21 ("kbuild: Inform user to pass ARCH= for make
mrproper"), if you try out-of-tree build with an unclean source tree,
it suggests to run 'make ARCH=<ARCH> mrproper'.

This looks odd when you are not cross-compiling the kernel. Show the
'ARCH=<ARCH>' part only when ARCH= was given from the command line.
If ARCH is the default (native build) or came from the environment,
it should simply suggest 'make mrproper' as before.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

You already know the location of the source tree without this message.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Both relative path and absolute path have pros and cons. For example,
we can move the source and objtree around together by using the
relative path to the source tree.

Do not force the absolute path to the source tree. If you prefer the
absolute path, you can specify KBUILD_ABS_SRCTREE=1.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Commit 415008af ("docs-rst: convert lsm from DocBook to ReST")
stopped using if_changed_rule. There is no more users of if_changed*
for the doc targets. Hence, fixdep is unneeded. Remove the dependency
on scripts_basic.

All the doc targets are phony. The dependency on FORCE is not needed
either.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Kbuild descends into scripts/basic/ even before the Kconfig.
I do not expect any other host programs added to this Makefile.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

CONFIG_CC_OPTIMIZE_FOR_SIZE was originally an independent boolean
option, but commit 877417e6 ("Kbuild: change CC_OPTIMIZE_FOR_SIZE
definition") turned it into a choice between _PERFORMANCE and _SIZE.

The phrase "If unsure, say N." sounds like an independent option.
Reword the help text to make it appropriate for the choice menu.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Commit 055efab3 ("kbuild: drop support for cc-ldoption") correctly
removed the cc-ldoption from Documentation/kbuild/makefiles.txt, but
commit cd238eff ("docs: kbuild: convert docs to ReST and rename
to *.rst") revived it. I guess it was a rebase mistake.

Remove it again.

Fixes: cd238eff ("docs: kbuild: convert docs to ReST and rename to *.rst")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

I see the following warnings when I open this document with a ReST
viewer, retext:

/home/masahiro/ref/linux/Documentation/kbuild/makefiles.rst:1142: (WARNING/2) Inline emphasis start-string without end-string.
/home/masahiro/ref/linux/Documentation/kbuild/makefiles.rst:1152: (WARNING/2) Inline emphasis start-string without end-string.
/home/masahiro/ref/linux/Documentation/kbuild/makefiles.rst:1154: (WARNING/2) Inline emphasis start-string without end-string.

These hunks were added by commit e846f0dc ("kbuild: add support
for ensuring headers are self-contained") and commit 1e21cbfa
("kbuild: support header-test-pattern-y"), respectively. They were
written not for ReST but for the plain text, and merged via the
kbuild tree.

In the same development cycle, this document was converted to ReST
by commit cd238eff ("docs: kbuild: convert docs to ReST and rename
to *.rst"), and merged via the doc sub-system.

Merging them together into Linus' tree resulted in the current situation.

To fix the syntax, surround the asterisks with back-quotes, and
use :: for the code sample.

Fixes: 39ceda5c ("Merge tag 'kbuild-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This line contains $(MAKE), so Make knows that it will invoke sub-make
without help of the '+' marker.
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>

When we execute make after merging the configurations we ignore any
errors it produces causing whatever is running merge_config.sh to be
unaware of any failures.  This issue was noticed by Guillaume Tucker
while looking at problems with testing of clang only builds in KernelCI
which caused Kbuild to be unable to find a working host compiler.

This implementation was suggested by Yamada-san.
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reported-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Makefile.lib is included by Makefile.modfinal as well as Makefile.build.

Move modkern_cflags to Makefile.lib in order to simplify cmd_cc_o_c
in Makefile.modfinal. Move modkern_cflags as well for consistency.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Add CONFIG_ASM_MODVERSIONS. This allows to remove one if-conditional
nesting in scripts/Makefile.build.

scripts/Makefile.build is run every time Kbuild descends into a
sub-directory. So, I want to avoid $(wildcard ...) evaluation
where possible although computing $(wildcard ...) is so cheap that
it may not make measurable performance difference.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

The pattern '*.order' was added by commit c6025f4c ("kbuild: ignore
*.order files") to ignore modules.order files.

I do not see any other user of the '.order' extension.

Ignore 'modules.order' explicitly instead of '*.order'.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

I think splitting the modpost and linking modules into separate
Makefiles will be useful especially when more complex build steps
come in. The main motivation of this commit is to integrate the
proposed klp-convert feature cleanly.

I moved the logging 'Building modules, stage 2.' to Makefile.modpost
to avoid the code duplication although I do not know whether or not
this message is needed in the first place.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Currently, the timestamp of module linker scripts are not checked.
Add them to the dependency of modules so they are correctly rebuilt.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

These three variables are not intended to be tweaked by users.
Move them from kbuild.rst to makefiles.rst.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Now that the single target build descends into sub-directories in the
same way as the normal build, these dummy Makefiles are not needed
any more.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>