Pull module fixes from Jessica Yu:
 "Code cleanups and kbuild/namespace related fixups from Masahiro.

  Most importantly, it fixes a namespace-related modpost issue for
  external module builds

   - Fix broken external module builds due to a modpost bug in
     read_dump(), where the namespace was not being strdup'd and
     sym->namespace would be set to bogus data.

   - Various namespace-related kbuild fixes and cleanups thanks to
     Masahiro Yamada"

* tag 'modules-for-v5.4-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
  doc: move namespaces.rst from kbuild/ to core-api/
  nsdeps: make generated patches independent of locale
  nsdeps: fix hashbang of scripts/nsdeps
  kbuild: fix build error of 'make nsdeps' in clean tree
  module: rename __kstrtab_ns_* to __kstrtabns_* to avoid symbol conflict
  modpost: fix broken sym->namespace for external module builds
  module: swap the order of symbol.namespace
  scripts: add_namespace: Fix coccicheck failed

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: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>

In commit 43d8ce9d65a5 ("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 f7b101d33046 ("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: Dmitry Goldin <dgoldin+lkml@protonmail.ch>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Masahiro 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: Masahiro Yamada <yamada.masahiro@socionext.com>

Minor formatting fixup.

Fixes: cd238effefa2 ("docs: kbuild: convert docs to ReST and rename to *.rst")
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Commit 40df759e2b9e ("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: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

Pull modules updates from Jessica Yu:
 "The main bulk of this pull request introduces a new exported symbol
  namespaces feature. The number of exported symbols is increasingly
  growing with each release (we're at about 31k exports as of 5.3-rc7)
  and we currently have no way of visualizing how these symbols are
  "clustered" or making sense of this huge export surface.

  Namespacing exported symbols allows kernel developers to more
  explicitly partition and categorize exported symbols, as well as more
  easily limiting the availability of namespaced symbols to other parts
  of the kernel. For starters, we have introduced the USB_STORAGE
  namespace to demonstrate the API's usage. I have briefly summarized
  the feature and its main motivations in the tag below.

  Summary:

   - Introduce exported symbol namespaces.

     This new feature allows subsystem maintainers to partition and
     categorize their exported symbols into explicit namespaces. Module
     authors are now required to import the namespaces they need.

     Some of the main motivations of this feature include: allowing
     kernel developers to better manage the export surface, allow
     subsystem maintainers to explicitly state that usage of some
     exported symbols should only be limited to certain users (think:
     inter-module or inter-driver symbols, debugging symbols, etc), as
     well as more easily limiting the availability of namespaced symbols
     to other parts of the kernel.

     With the module import requirement, it is also easier to spot the
     misuse of exported symbols during patch review.

     Two new macros are introduced: EXPORT_SYMBOL_NS() and
     EXPORT_SYMBOL_NS_GPL(). The API is thoroughly documented in
     Documentation/kbuild/namespaces.rst.

   - Some small code and kbuild cleanups here and there"

* tag 'modules-for-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
  module: Remove leftover '#undef' from export header
  module: remove unneeded casts in cmp_name()
  module: move CONFIG_UNUSED_SYMBOLS to the sub-menu of MODULES
  module: remove redundant 'depends on MODULES'
  module: Fix link failure due to invalid relocation on namespace offset
  usb-storage: export symbols in USB_STORAGE namespace
  usb-storage: remove single-use define for debugging
  docs: Add documentation for Symbol Namespaces
  scripts: Coccinelle script for namespace dependencies.
  modpost: add support for generating namespace dependencies
  export: allow definition default namespaces in Makefiles or sources
  module: add config option MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
  modpost: add support for symbol namespaces
  module: add support for symbol namespaces.
  export: explicitly align struct kernel_symbol
  module: support reading multiple values per modinfo tag

Pull Kbuild updates from Masahiro Yamada:

 - add modpost warn exported symbols marked as 'static' because 'static'
   and EXPORT_SYMBOL is an odd combination

 - break the build early if gold linker is used

 - optimize the Bison rule to produce .c and .h files by a single
   pattern rule

 - handle PREEMPT_RT in the module vermagic and UTS_VERSION

 - warn CONFIG options leaked to the user-space except existing ones

 - make single targets work properly

 - rebuild modules when module linker scripts are updated

 - split the module final link stage into scripts/Makefile.modfinal

 - fix the missed error code in merge_config.sh

 - improve the error message displayed on the attempt of the O= build in
   unclean source tree

 - remove 'clean-dirs' syntax

 - disable -Wimplicit-fallthrough warning for Clang

 - add CONFIG_CC_OPTIMIZE_FOR_SIZE_O3 for ARC

 - remove ARCH_{CPP,A,C}FLAGS variables

 - add $(BASH) to run bash scripts

 - change *CFLAGS_<basetarget>.o to take the relative path to $(obj)
   instead of the basename

 - stop suppressing Clang's -Wunused-function warnings when W=1

 - fix linux/export.h to avoid genksyms calculating CRC of trimmed
   exported symbols

 - misc cleanups

* tag 'kbuild-v5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (63 commits)
  genksyms: convert to SPDX License Identifier for lex.l and parse.y
  modpost: use __section in the output to *.mod.c
  modpost: use MODULE_INFO() for __module_depends
  export.h, genksyms: do not make genksyms calculate CRC of trimmed symbols
  export.h: remove defined(__KERNEL__), which is no longer needed
  kbuild: allow Clang to find unused static inline functions for W=1 build
  kbuild: rename KBUILD_ENABLE_EXTRA_GCC_CHECKS to KBUILD_EXTRA_WARN
  kbuild: refactor scripts/Makefile.extrawarn
  merge_config.sh: ignore unwanted grep errors
  kbuild: change *FLAGS_<basetarget>.o to take the path relative to $(obj)
  modpost: add NOFAIL to strndup
  modpost: add guid_t type definition
  kbuild: add $(BASH) to run scripts with bash-extension
  kbuild: remove ARCH_{CPP,A,C}FLAGS
  kbuild,arc: add CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 for ARC
  kbuild: Do not enable -Wimplicit-fallthrough for clang for now
  kbuild: clean up subdir-ymn calculation in Makefile.clean
  kbuild: remove unneeded '+' marker from cmd_clean
  kbuild: remove clean-dirs syntax
  kbuild: check clean srctree even earlier
  ...

In the Distribution Kernels track at Linux Plumbers Conference there
was some discussion around the difficulty of making kernel builds
reproducible.

This is a solved problem, but the solutions don't appear to be
documented in one place.  This document lists the issues I know about
and the settings needed to ensure reproducibility.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Describe using Symbol Namespaces from a perspective of a user. I.e.
module authors or subsystem maintainers.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>