Commit d3fc425e ("kbuild: make sure autoksyms.h exists early")
moved the code that touches autoksyms.h to scripts/kconfig/Makefile
with obscure reason.

From Nicolas' comment [1], he did not seem to be sure about the root
cause.

I guess I figured it out, so here is a fix-up I think is more correct.
According to the error log in the original post [2], the build failed
in scripts/mod/devicetable-offsets.c

scripts/mod/Makefile is descended from scripts/Makefile, which is
invoked from the top-level Makefile by the 'scripts' target.

To build vmlinux and/or modules, Kbuild descend into $(vmlinux-dirs).
This depends on 'prepare' and 'scripts' as follows:

  $(vmlinux-dirs): prepare scripts

Because there is no dependency between 'prepare' and 'scripts', the
parallel building can execute them simultaneously.

'prepare' depends on 'prepare1', which touched autoksyms.h, while
'scripts' descends into script/, then scripts/mod/, which needs
<generated/autoksyms.h> if CONFIG_TRIM_UNUSED_KSYMS.  It was the
reason of the race.

I am not happy to have unrelated code in the Kconfig Makefile, so
getting it back to the top Makefile.

I removed the standalone test target because I want to use it to
create an empty autoksyms.h file.  Here is a little improvement;
unnecessary autoksyms.h is not created when CONFIG_TRIM_UNUSED_KSYMS
is disabled.

[1] https://lkml.org/lkml/2016/11/30/734
[2] https://lkml.org/lkml/2016/11/30/531Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NNicolas Pitre <nico@linaro.org>

Just a trivial change to prepare for the next commit.
This target is still invisible from external module building.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Currently LDFLAGS is not cleared, so same flags are accumulated in
LDFLAGS when the top Makefile is recursively invoked.

I found unneeded rebuild for ARCH=arm64 when CONFIG_TRIM_UNUSED_KSYMS
is enabled.  If include/generated/autoksyms.h is updated, the top
Makefile is recursively invoked, then arch/arm64/Makefile adds one
more '-maarch64linux'.  Due to the command line change, modules are
rebuilt needlessly.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NNicolas Pitre <nico@linaro.org>

Support parallel building of clean, config, and build targets in a
single command.

For example,

  make -j<N> clean all

or

  make -j<N> mrproper defconfig all

They should be handled one by one.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Incremental linking is gone, so rename built-in.o to built-in.a, which
is the usual extension for archive files.

This patch does two things, first is a simple search/replace:

git grep -l 'built-in\.o' | xargs sed -i 's/built-in\.o/built-in\.a/g'

The second is to invert nesting of nested text manipulations to avoid
filtering built-in.a out from libs-y2:

-libs-y2 := $(filter-out %.a, $(patsubst %/, %/built-in.a, $(libs-y)))
+libs-y2 := $(patsubst %/, %/built-in.a, $(filter-out %.a, $(libs-y)))
Signed-off-by: NNicholas Piggin <npiggin@gmail.com>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

'--build-id' is passed to $(LD), so it should be tested by 'ld-option'.

This seems a kind of misconversion when ld-option was renamed to
cc-ldoption.

Commit f86fd306 ("kbuild: rename ld-option to cc-ldoption") renamed
all instances of 'ld-option' to 'cc-ldoption'.

Then, commit 691ef3e7 ("kbuild: introduce ld-option") re-added
'ld-option' as a new implementation.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Currently, sparse issues warnings on code using an attribute
it doesn't know about.

One of the problem with this is that these warnings have no
value for the developer, it's just noise for him. At best these
warnings tell something about some deficiencies of sparse itself
but not about a potential problem with code analyzed.

A second problem with this is that sparse release are, alas,
less frequent than new attributes are added to GCC.

So, avoid the noise by asking sparse to not warn about
attributes it doesn't know about.

Reference: https://marc.info/?l=linux-sparse&m=151871600016790
Reference: https://marc.info/?l=linux-sparse&m=151871725417322Signed-off-by: NLuc Van Oostenryck <luc.vanoostenryck@gmail.com>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Tested-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

The comment above the silentoldconfig invocation is outdated.
'make oldconfig' updates just .config and doesn't touch the
include/config/ tree.

This came up in https://lkml.org/lkml/2018/2/12/415.

While fixing the comment, make it more informative by explaining the
purpose of the unfortunately named silentoldconfig.

I can't make sense of the comment re. auto.conf.cmd and a cleaned tree.
include/config/auto.conf and include/config/auto.conf.cmd are both
created simultaneously by silentoldconfig (in
scripts/kconfig/confdata.c, by conf_write_autoconf()), and nothing seems
to remove auto.conf.cmd that wouldn't remove auto.conf. Remove that part
of the comment rather than blindly copying it. It might be a leftover
from an older way of doing things.

The include/config/auto.conf.cmd prerequisite might be there to ensure
that silentoldconfig gets rerun if conf_write_autoconf() fails between
writing out auto.conf.cmd and auto.conf (a comment in the function
indicates that auto.conf is deliberately written out last to mark
completion of the operation). It seems the Makefile dependency between
include/config/auto.conf and .config would already take care of that
though, since include/config/auto.conf would still be out of date re.
.config if the operation fails.

Cop out and leave the prerequisite in for now.
Signed-off-by: NUlf Magnusson <ulfalizer@gmail.com>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Disable retpoline validation in objtool if your compiler sucks, and otherwise
select the validation stuff for CONFIG_RETPOLINE=y (most builds would already
have it set due to ORC).
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Nearly all modern compilers support a stack-protector option, and nearly
all modern distributions enable the kernel stack-protector, so enabling
this by default in kernel builds would make sense.  However, Kconfig does
not have knowledge of available compiler features, so it isn't safe to
force on, as this would unconditionally break builds for the compilers or
architectures that don't have support.  Instead, this introduces a new
option, CONFIG_CC_STACKPROTECTOR_AUTO, which attempts to discover the best
possible stack-protector available, and will allow builds to proceed even
if the compiler doesn't support any stack-protector.

This option is made the default so that kernels built with modern
compilers will be protected-by-default against stack buffer overflows,
avoiding things like the recent BlueBorne attack.  Selection of a specific
stack-protector option remains available, including disabling it.

Additionally, tiny.config is adjusted to use CC_STACKPROTECTOR_NONE, since
that's the option with the least code size (and it used to be the default,
so we have to explicitly choose it there now).

Link: http://lkml.kernel.org/r/1510076320-69931-4-git-send-email-keescook@chromium.orgSigned-off-by: NKees Cook <keescook@chromium.org>
Tested-by: NLaura Abbott <labbott@redhat.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Various portions of the kernel, especially per-architecture pieces,
need to know if the compiler is building with the stack protector.
This was done in the arch/Kconfig with 'select', but this doesn't
allow a way to do auto-detected compiler support. In preparation for
creating an on-if-available default, move the logic for the definition of
CONFIG_CC_STACKPROTECTOR into the Makefile.

Link: http://lkml.kernel.org/r/1510076320-69931-3-git-send-email-keescook@chromium.orgSigned-off-by: NKees Cook <keescook@chromium.org>
Tested-by: NLaura Abbott <labbott@redhat.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In order to make stack-protector failures warn instead of unconditionally
breaking the build, this moves the compiler output sanity-check earlier,
and sets a flag for later testing.  Future patches can choose to warn or
fail, depending on the flag value.

Link: http://lkml.kernel.org/r/1510076320-69931-2-git-send-email-keescook@chromium.orgSigned-off-by: NKees Cook <keescook@chromium.org>
Tested-by: NLaura Abbott <labbott@redhat.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With KASAN enabled the kernel has two different memset() functions, one
with KASAN checks (memset) and one without (__memset).  KASAN uses some
macro tricks to use the proper version where required.  For example
memset() calls in mm/slub.c are without KASAN checks, since they operate
on poisoned slab object metadata.

The issue is that clang emits memset() calls even when there is no
memset() in the source code.  They get linked with improper memset()
implementation and the kernel fails to boot due to a huge amount of KASAN
reports during early boot stages.

The solution is to add -fno-builtin flag for files with KASAN_SANITIZE :=
n marker.

Link: http://lkml.kernel.org/r/8ffecfffe04088c52c42b92739c2bd8a0bcb3f5e.1516384594.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Acked-by: NNick Desaulniers <ndesaulniers@google.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently, GCC disables -Wunused-const-variable, but not
-Wunused-variable, so warns unused variables if they are
non-constant.

While, Clang does not warn unused variables at all regardless of
the const qualifier because -Wno-unused-const-variable is implied
by the stronger option -Wno-unused-variable.

Disable -Wunused-const-variable instead of -Wunused-variable so that
GCC and Clang work in the same way.
Signed-off-by: NPrasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

It appears that hardened gentoo enables "-fstack-check" by default for
gcc.

That doesn't work _at_all_ for the kernel, because the kernel stack
doesn't act like a user stack at all: it's much smaller, and it doesn't
auto-expand on use.  So the extra "probe one page below the stack" code
generated by -fstack-check just breaks the kernel in horrible ways,
causing infinite double faults etc.

[ I have to say, that the particular code gcc generates looks very
  stupid even for user space where it works, but that's a separate
  issue.  ]
Reported-and-tested-by: NAlexander Tsoy <alexander@tsoy.me>
Reported-and-tested-by: NToralf Förster <toralf.foerster@gmx.de>
Cc: stable@kernel.org
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Allow users to use their favorite lexer / parser generators.
This is useful for me to test various flex and bison versions.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Geert reported commit ae6b289a ("kbuild: Set KBUILD_CFLAGS before
incl. arch Makefile") broke cross-compilation using a cross-compiler
that supports less compiler options than the host compiler.

For example,

  cc1: error: unrecognized command line option "-Wno-unused-but-set-variable"

This problem happens on architectures that setup CROSS_COMPILE in their
arch/*/Makefile.

Move the cc-option and cc-disable-warning back to the original position,
but keep the Clang target options untouched.

Fixes: ae6b289a ("kbuild: Set KBUILD_CFLAGS before incl. arch Makefile")
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: NGeert Uytterhoeven <geert@linux-m68k.org>

*.i and *.lst are supported by the single target build.  Clean up them.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

The "rpm" has been kept for backward compatibility since pre-git era.
I am planning to remove it after the Linux 4.18 release.  Annouce the
end of the support, prompting to use "rpm-pkg" instead.

If you use "rpm", it will work like "rpm-pkg", but warning messages
will be displayed as follows:

  WARNING: "rpm" target will be removed after Linux 4.18
           Please use "rpm-pkg" instead.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

Set the clang KBUILD_CFLAGS up before including arch/ Makefiles,
so that ld-options (etc.) can work correctly.

This fixes errors with clang such as ld-options trying to CC
against your host architecture, but LD trying to link against
your target architecture.
Signed-off-by: NChris Fries <cfries@google.com>
Signed-off-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NMatthias Kaehlcke <mka@chromium.org>
Tested-by: NMatthias Kaehlcke <mka@chromium.org>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

"obj-y += foo/" syntax requires Kbuild to visit the "foo" subdirectory
and link built-in.o from that directory.  This means foo/Makefile is
responsible for creating built-in.o even if there is no object to
link (in this case, built-in.o is an empty archive).

We have had several fixups like commit 4b024242 ("kbuild: Fix
linking error built-in.o no such file or directory"), then ended up
with a complex condition as follows:

  ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),)
  builtin-target := $(obj)/built-in.o
  endif

We still have more cases not covered by the above, so we need to add
  obj- := dummy.o
in several places just for creating empty built-in.o.

A key point is, the parent Makefile knows whether built-in.o is needed
or not.  If a subdirectory needs to create built-in.o, its parent can
tell the fact when descending.

If non-empty $(need-builtin) flag is passed from the parent, built-in.o
should be created.  $(obj-y) should be still checked to support the
single target "%/".  All of ugly tricks will go away.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: NSam Ravnborg <sam@ravnborg.org>

Most places use pwd and rely on $PATH lookup. Moving the remaining
absolute path /bin/pwd users over for consistency.

Also, a reason for doing /bin/pwd -> pwd instead of the other way around
is because I believe build systems should make little assumptions on
host filesystem layout. Case in point, we do this kind of patching
already in NixOS.

Ref. commit 028568d8
("kbuild: revert $(realpath ...) to $(shell cd ... && /bin/pwd)").
Signed-off-by: NBjørn Forsman <bjorn.forsman@gmail.com>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

The flag enables Clang instrumentation of comparison operations
(currently not supported by GCC).  This instrumentation is needed by the
new KCOV device to collect comparison operands.

Link: http://lkml.kernel.org/r/20171011095459.70721-2-glider@google.comSigned-off-by: NVictor Chibotaru <tchibo@google.com>
Signed-off-by: NAlexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Popov <alex.popov@linux.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: <syzkaller@googlegroups.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In my view, it is not helpful to have a separate file just for
the coccicheck help message.  Merge scripts/Makefile.help into
the top-level Makefile.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NJulia Lawall <julia.lawall@lip6.fr>

I do not see any reason why $(wildcard ...) needs to be called twice
for computing cmd_files.  Remove the first one.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>