During an investigation to fix up the execute bits of scripts in the
kernel repository, Andrew Morton and Kees Cook pointed out that the
execute bit should not matter, and that build scripts cannot rely on that.
Kees could not point to any documentation, though.

Masahiro Yamada explained the convention of setting execute bits to make
it easier for manual script invocation.

Provide some basic documentation how the build shall invoke scripts, such
that the execute bits do not matter, and acknowledge that execute bits are
useful nonetheless.

This serves as reference for further clean-up patches in the future.
Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
Suggested-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NLukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ujjwal Kumar <ujjwalkumar0501@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/lkml/20200830174409.c24c3f67addcce0cea9a9d4c@linux-foundation.org/
Link: https://lore.kernel.org/lkml/202008271102.FEB906C88@keescook/
Link: https://lore.kernel.org/linux-kbuild/CAK7LNAQdrvMkDA6ApDJCGr+5db8SiPo=G+p8EiOvnnGvEN80gA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20201001075723.24246-1-lukas.bulwahn@gmail.comSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

clang --target=<triple> is how we can specify a particular toolchain
triple to be use, fix the two occurences in the documentation.

Fixes: fcf1b6a3 ("Documentation/llvm: add documentation on building w/ Clang/LLVM")
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

This is a general cleanup of kbuild/makefiles.rst:

* Use "Chapter" for major heading references and use "section" for
  the next-level heading references, for consistency.
* Section 3.8 was deleted long ago.
* Drop the ending ':' in section names in the contents list.
* Correct some section numbering references.
* Correct verb agreement typo.
* Fix run-on sentence punctuation.
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Based on a vote at the LLVM BoF at Plumbers 2020, we decided to start
small, supporting just one formal upstream release of LLVM for now.

We can probably widen the support window of supported versions over
time.  Also, note that LLVM's release process is different than GCC's.
GCC tends to have 1 major release per year while releasing minor updates
to the past 3 major versions.  LLVM tends to support one major release
and one minor release every six months.
Signed-off-by: NNick Desaulniers <ndesaulniers@google.com>
Tested-by: NGustavo A. R. Silva <gustavoars@kernel.org>
Tested-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NWill Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200826191555.3350406-1-ndesaulniers@google.comSigned-off-by: NJonathan Corbet <corbet@lwn.net>

While reviewing a separate patch, I noticed that the formatting of the
commands, variables, and arguments was not in a monospaced font like the
rest of the Kbuild documentation (see kbuild/kconfig.rst for an
example). This is due to a lack of "::" before indented command blocks
and single backticks instead of double backticks for inline formatting.

Add those so that the document looks nicer in an HTML format, while not
ruining the look in plain text.

As a result of this, we can remove the escaped backslashes in the last
code block and move them to single backslashes.
Signed-off-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

To build host programs, you need to add the program names to 'hostprogs'
to use the necessary build rule, but it is not enough to build them
because there is no dependency.

There are two types of host programs: built as the prerequisite of
another (e.g. gen_crc32table in lib/Makefile), or always built when
Kbuild visits the Makefile (e.g. genksyms in scripts/genksyms/Makefile).

The latter is typical in Makefiles under scripts/, which contains host
programs globally used during the kernel build. To build them, you need
to add them to both 'hostprogs' and 'always-y'.

This commit adds hostprogs-always-y as a shorthand.

The same applies to user programs. net/bpfilter/Makefile builds
bpfilter_umh on demand, hence always-y is unneeded. In contrast,
programs under samples/ are added to both 'userprogs' and 'always-y'
so they are always built when Kbuild visits the Makefiles.

userprogs-always-y works as a shorthand.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NMiguel Ojeda <miguel.ojeda.sandonis@gmail.com>

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
  If not .svg:
    For each line:
      If doesn't contain `\bxmlns\b`:
        For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
	  If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
            If both the HTTP and HTTPS versions
            return 200 OK and serve the same content:
              Replace HTTP with HTTPS.
Signed-off-by: NAlexander A. Klimov <grandmaster@al2klimov.de>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

CFLAGS_REMOVE_<file>.o filters out flags when compiling a particular
object, but there is no convenient way to do that for every object in
a directory.

Add ccflags-remove-y and asflags-remove-y to make it easily.

Use ccflags-remove-y to clean up some Makefiles.

The add/remove order works as follows:

 [1] KBUILD_CFLAGS specifies compiler flags used globally

 [2] ccflags-y adds compiler flags for all objects in the
     current Makefile

 [3] ccflags-remove-y removes compiler flags for all objects in the
     current Makefile (New feature)

 [4] CFLAGS_<file> adds compiler flags per file.

 [5] CFLAGS_REMOVE_<file> removes compiler flags per file.

Having [3] before [4] allows us to remove flags from most (but not all)
objects in the current Makefile.

For example, kernel/trace/Makefile removes $(CC_FLAGS_FTRACE)
from all objects in the directory, then adds it back to
trace_selftest_dynamic.o and CFLAGS_trace_kprobe_selftest.o

The same applies to lib/livepatch/Makefile.

Please note ccflags-remove-y has no effect to the sub-directories.
In contrast, the previous notation got rid of compiler flags also from
all the sub-directories.

The following are not affected because they have no sub-directories:

  arch/arm/boot/compressed/
  arch/powerpc/xmon/
  arch/sh/
  kernel/trace/

However, lib/ has several sub-directories.

To keep the behavior, I added ccflags-remove-y to all Makefiles
in subdirectories of lib/, except the following:

  lib/vdso/Makefile        - Kbuild does not descend into this Makefile
  lib/raid/test/Makefile   - This is not used for the kernel build

I think commit 2464a609 ("ftrace: do not trace library functions")
excluded too much. In the next commit, I will remove ccflags-remove-y
from the sub-directories of lib/.
Suggested-by: NSami Tolvanen <samitolvanen@google.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Brendan Higgins <brendanhiggins@google.com> (KUnit)
Tested-by: NAnders Roxell <anders.roxell@linaro.org>

Drop the doubled word "the".
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Acked-by: NMasahiro Yamada <masahiroy@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: linux-kbuild@vger.kernel.org
Link: https://lore.kernel.org/r/20200707180414.10467-11-rdunlap@infradead.orgSigned-off-by: NJonathan Corbet <corbet@lwn.net>

Some Makefiles already pass -fno-stack-protector unconditionally.
For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile.

No problem report so far about hard-coding this option. So, we can
assume all supported compilers know -fno-stack-protector.

GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN)

Get rid of cc-option from -fno-stack-protector.

Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which is always 'y'.

Note:
arch/mips/vdso/Makefile adds -fno-stack-protector twice, first
unconditionally, and second conditionally. I removed the second one.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
Acked-by: NArd Biesheuvel <ardb@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

Commit cd238eff ("docs: kbuild: convert docs to ReST and rename to
*.rst") missed a ReST header and a verbatim file content area.
Signed-off-by: NDov Murik <dovmurik@linux.vnet.ibm.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Fix typos "plgins" -> "plugins".
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NKees Cook <keescook@chromium.org>

Commit d503ac53 ("kbuild: rename LDFLAGS to KBUILD_LDFLAGS") missed
to update the documentation.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

This is a left-over of commit 39808e45 ("kbuild: do not read
$(KBUILD_EXTMOD)/Module.symvers").

Kbuild no longer supports this way.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Kbuild now supports the syntax 'userprogs' to compile userspace
programs for the same architecture as the kernel.

Insert the section '5 Userspace Program support' to explain it.

I copy-pasted '4 Host Program support' and fixed it up.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NSam Ravnborg <sam@ravnborg.org>

Make it consistent with the other sections.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

As Documentation/kbuild/llvm.rst implies, building the kernel with a
full set of LLVM tools gets very verbose and unwieldy.

Provide a single switch LLVM=1 to use Clang and LLVM tools instead
of GCC and Binutils. You can pass it from the command line or as an
environment variable.

Please note LLVM=1 does not turn on the integrated assembler. You need
to pass LLVM_IAS=1 to use it. When the upstream kernel is ready for the
integrated assembler, I think we can make it default.

We discussed what we need, and we agreed to go with a simple boolean
flag that switches both target and host tools:

  https://lkml.org/lkml/2020/3/28/494
  https://lkml.org/lkml/2020/4/3/43

Some items discussed, but not adopted:

- LLVM_DIR

  When multiple versions of LLVM are installed, I just thought supporting
  LLVM_DIR=/path/to/my/llvm/bin/ might be useful.

  CC      = $(LLVM_DIR)clang
  LD      = $(LLVM_DIR)ld.lld
    ...

  However, we can handle this by modifying PATH. So, we decided to not do
  this.

- LLVM_SUFFIX

  Some distributions (e.g. Debian) package specific versions of LLVM with
  naming conventions that use the version as a suffix.

  CC      = clang$(LLVM_SUFFIX)
  LD      = ld.lld(LLVM_SUFFIX)
    ...

  will allow a user to pass LLVM_SUFFIX=-11 to use clang-11 etc.,
  but the suffixed versions in /usr/bin/ are symlinks to binaries in
  /usr/lib/llvm-#/bin/, so this can also be handled by PATH.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build
Tested-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

The 'AS' variable is unused for building the kernel. Only the remaining
usage is to turn on the integrated assembler. A boolean flag is a better
fit for this purpose.

AS=clang was added for experts. So, I replaced it with LLVM_IAS=1,
breaking the backward compatibility.
Suggested-by: NNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

The tool is called llvm-size, not llvm-objsize.

Fixes: fcf1b6a3 ("Documentation/llvm: add documentation on building w/ Clang/LLVM")
Signed-off-by: NFangrui Song <maskray@google.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

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 bd5cbced), 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: cb9b55d2 ("modpost: add support for symbol namespaces")
Tested-by: NMatthias Maennich <maennich@google.com>
Reviewed-by: NMatthias Maennich <maennich@google.com>
Reviewed-by: NLucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: NJessica Yu <jeyu@kernel.org>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

The 'imply' statement may create unmet direct dependency when the
implied symbol depends on m.

[Test Code]

  config FOO
          tristate "foo"
          imply BAZ

  config BAZ
          tristate "baz"
          depends on BAR

  config BAR
          def_tristate m

  config MODULES
          def_bool y
          option modules

If you set FOO=y, BAZ is also promoted to y, which results in the
following .config file:

  CONFIG_FOO=y
  CONFIG_BAZ=y
  CONFIG_BAR=m
  CONFIG_MODULES=y

This does not meet the dependency 'BAZ depends on BAR'.

Unlike 'select', what is worse, Kconfig never shows the
'WARNING: unmet direct dependencies detected for ...' for this case.

Because 'imply' is considered to be weaker than 'depends on', Kconfig
should take the direct dependency into account.

For clarification, describe this case in kconfig-language.rst too.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NNicolas Pitre <nico@fluxnic.net>
Tested-by: NGeert Uytterhoeven <geert@linux-m68k.org>

The 'imply' keyword restricts a symbol to y or n, excluding m
when it is implied by y. This is the original behavior since
commit 237e3ad0 ("Kconfig: Introduce the "imply" keyword").

However, the author of this feature, Nicolas Pitre, stated that
the 'imply' keyword should not impose any restrictions.
(https://lkml.org/lkml/2020/2/19/714)

I agree, and want to get rid of this tricky behavior.
Suggested-by: NNicolas Pitre <nico@fluxnic.net>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NNicolas Pitre <nico@fluxnic.net>

All the files in Documentation/kbuild/ were converted to reST.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Information about GCC plugins is relevant to kernel building, so move this
document to the kbuild manual.
Acked-by: NMasahiro Yamada <masahiroy@kernel.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Added to kbuild documentation. Provides more official info on building
kernels with Clang and LLVM than our wiki.
Suggested-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NNathan Chancellor <natechancellor@gmail.com>
Reviewed-by: NSedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: NNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

obj-* needs a trailing slash for a directory, but subdir-* does not.
Signed-off-by: NMasahiro 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 fcc8487d ("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: NMasahiro 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: NMasahiro 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: NMasahiro Yamada <masahiroy@kernel.org>

Fix a couple typos in kconfig-language documentation.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Commit bc081dd6 ("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: NMasahiro 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: NJohan Hovold <johan@kernel.org>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NJohan Hovold <johan@kernel.org>

Since commit 84af7a61 ("checkpatch: kconfig: prefer 'help' over
'---help---'"), scripts/checkpatch.pl warns the use of ---help---.

Kconfig still supports ---help---, but new code should avoid using it.
Let's stop advertising it in documentation.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

There are both positive and negative options about this feature.
At first, I thought it was a good idea, but actually Linus stated a
negative opinion (https://lkml.org/lkml/2019/9/29/227). I admit it
is ugly and annoying.

The baseline I'd like to keep is the compile-test of uapi headers.
(Otherwise, kernel developers have no way to ensure the correctness
of the exported headers.)

I will maintain a small build rule in usr/include/Makefile.
Remove the other header test functionality.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Since commit 040fcc81 ("kbuild: improved modversioning support for
external modules"), the external module build reads Module.symvers in
the directory of the module itself, then dumps symbols back into it.
It accumulates stale symbols in the file when you build an external
module incrementally.

The idea behind it was, as the commit log explained, you can copy
Modules.symvers from one module to another when you need to pass symbol
information between two modules. However, the manual copy of the file
sounds questionable to me, and containing stale symbols is a downside.

Some time later, commit 0d96fb20 ("kbuild: Add new Kbuild variable
KBUILD_EXTRA_SYMBOLS") introduced a saner approach.

So, this commit removes the former one. Going forward, the external
module build dumps symbols into Module.symvers to be carried via
KBUILD_EXTRA_SYMBOLS, but never reads it automatically.

With the -I option removed, there is no one to set the external_module
flag unless KBUILD_EXTRA_SYMBOLS is passed. Now the -i option does it
instead.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

We discussed a better location for this file, and agreed that
core-api/ is a good fit. Rename it to symbol-namespaces.rst
for disambiguation, and also add it to index.rst and MAINTAINERS.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NMatthias Maennich <maennich@google.com>
Signed-off-by: NJessica Yu <jeyu@kernel.org>

In commit 43d8ce9d ("Provide in-kernel headers to make
extending kernel easier") a new mechanism was introduced, for kernels
>=5.2, which embeds the kernel headers in the kernel image or a module
and exposes them in procfs for use by userland tools.

The archive containing the header files has nondeterminism caused by
header files metadata. This patch normalizes the metadata and utilizes
KBUILD_BUILD_TIMESTAMP if provided and otherwise falls back to the
default behaviour.

In commit f7b101d3 ("kheaders: Move from proc to sysfs") it was
modified to use sysfs and the script for generation of the archive was
renamed to what is being patched.
Signed-off-by: NDmitry Goldin <dgoldin+lkml@protonmail.ch>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Capitalize the first word in the sentence.

Use obj-m instead of obj-y. obj-y still works, but we have no built-in
objects in external module builds. So, obj-m is better IMHO.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Minor formatting fixup.

Fixes: cd238eff ("docs: kbuild: convert docs to ReST and rename to *.rst")
Signed-off-by: NAlex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: NMatthew Garrett <mjg59@google.com>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Commit 40df759e ("kbuild: Fix build with binutils <= 2.19")
introduced ar-option and KBUILD_ARFLAGS to deal with old binutils.

According to Documentation/process/changes.rst, the current minimal
supported version of binutils is 2.21 so you can assume the 'D' option
is always supported. Not only GNU ar but also llvm-ar supports it.

With the 'D' option hard-coded, there is no more user of ar-option
or KBUILD_ARFLAGS.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Tested-by: NNick Desaulniers <ndesaulniers@google.com>