cfi: Flip headers

Normal include order is that linux/foo.h should include asm/foo.h, CFI has it
the wrong way around.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20231215092707.231038174@infradead.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

asm-generic: Fix spelling of architecture

Fix spelling of "architecture" in the Kbuild file.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

kernel: remove platform_has() infrastructure

The only use case of the platform_has() infrastructure has been
removed again, so remove the whole feature.

Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 guest using Xen
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20220622063838.8854-3-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

random: remove CONFIG_ARCH_RANDOM

When RDRAND was introduced, there was much discussion on whether it
should be trusted and how the kernel should handle that. Initially, two
mechanisms cropped up, CONFIG_ARCH_RANDOM, a compile time switch, and
"nordrand", a boot-time switch.

Later the thinking evolved. With a properly designed RNG, using RDRAND
values alone won't harm anything, even if the outputs are malicious.
Rather, the issue is whether those values are being *trusted* to be good
or not. And so a new set of options were introduced as the real
ones that people use -- CONFIG_RANDOM_TRUST_CPU and "random.trust_cpu".
With these options, RDRAND is used, but it's not always credited. So in
the worst case, it does nothing, and in the best case, maybe it helps.

Along the way, CONFIG_ARCH_RANDOM's meaning got sort of pulled into the
center and became something certain platforms force-select.

The old options don't really help with much, and it's a bit odd to have
special handling for these instructions when the kernel can deal fine
with the existence or untrusted existence or broken existence or
non-existence of that CPU capability.

Simplify the situation by removing CONFIG_ARCH_RANDOM and using the
ordinary asm-generic fallback pattern instead, keeping the two options
that are actually used. For now it leaves "nordrand" for now, as the
removal of that will take a different route.

Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

kernel: add platform_has() infrastructure

Add a simple infrastructure for setting, resetting and querying
platform feature flags.

Flags can be either global or architecture specific.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Tested-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> # Arm64 only
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Juergen Gross <jgross@suse.com>

softirq: Move do_softirq_own_stack() to generic asm header

To avoid include recursion hell move the do_softirq_own_stack() related
content into a generic asm header and include it from all places in arch/
which need the prototype.

This allows architectures to provide an inline implementation of
do_softirq_own_stack() without introducing a lot of #ifdeffery all over the
place.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210210002513.289960691@linutronix.de

mm: Remove arch_remap() and mm-arch-hooks.h

powerpc was the last provider of arch_remap() and the last
user of mm-arch-hooks.h.

Since commit 526a9c4a7234 ("powerpc/vdso: Provide vdso_remap()"),
arch_remap() hence mm-arch-hooks.h are not used anymore.

Remove them.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Richard Weinberger <richard@nod.at>

local64.h: make <asm/local64.h> mandatory

Make <asm-generic/local64.h> mandatory in include/asm-generic/Kbuild and
remove all arch/*/include/asm/local64.h arch-specific files since they
only #include <asm-generic/local64.h>.

This fixes build errors on arch/c6x/ and arch/nios2/ for
block/blk-iocost.c.

Build-tested on 21 of 25 arch-es. (tools problems on the others)

Yes, we could even rename <asm-generic/local64.h> to
<linux/local64.h> and change all #includes to use
<linux/local64.h> instead.

Link: https://lkml.kernel.org/r/20201227024446.17018-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Aurelien Jacquiot <jacquiot.aurelien@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

highmem: Get rid of kmap_types.h

The header is not longer used and on alpha, ia64, openrisc, parisc and um
it was completely unused anyway as these architectures have no highmem
support.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20201103095858.422094352@linutronix.de

asm-generic: Provide kmap_size.h

kmap_types.h is a misnomer because the old atomic MAP based array does not
exist anymore and the whole indirection of architectures including
kmap_types.h is inconinstent and does not allow to provide guard page
debugging for this misfeature.

Add a common header file which defines the mapping stack size for all
architectures. Will be used when converting architectures over to a
generic kmap_local/atomic implementation.

The array size is chosen with the following constraints in mind:

- The deepest nest level in one context is 3 according to code
inspection.

- The worst case nesting for the upcoming reemptible version would be:

2 maps in task context and a fault inside
2 maps in the fault handler
3 maps in softirq
2 maps in interrupt

So a total of 16 is sufficient and probably overestimated.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20201103095857.078043987@linutronix.de

dma-mapping: remove <asm/dma-contiguous.h>

Just provide a weak default definition of dma_contiguous_early_fixup and
let arm override it.

Signed-off-by: Christoph Hellwig <hch@lst.de>

kbuild: preprocess module linker script

There was a request to preprocess the module linker script like we
do for the vmlinux one. (https://lkml.org/lkml/2020/8/21/512)

The difference between vmlinux.lds and module.lds is that the latter
is needed for external module builds, thus must be cleaned up by
'make mrproper' instead of 'make clean'. Also, it must be created
by 'make modules_prepare'.

You cannot put it in arch/$(SRCARCH)/kernel/, which is cleaned up by
'make clean'. I moved arch/$(SRCARCH)/kernel/module.lds to
arch/$(SRCARCH)/include/asm/module.lds.h, which is included from
scripts/module.lds.S.

scripts/module.lds is fine because 'make clean' keeps all the
build artifacts under scripts/.

You can add arch-specific sections in <asm/module.lds.h>.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Jessica Yu <jeyu@kernel.org>

compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h

In preparation for allowing architectures to define their own
implementation of the READ_ONCE() macro, move the generic
{READ,WRITE}_ONCE() definitions out of the unwieldy 'linux/compiler.h'
file and into a new 'rwonce.h' header under 'asm-generic'.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

arch: split MODULE_ARCH_VERMAGIC definitions out to <asm/vermagic.h>

As the bug report [1] pointed out, <linux/vermagic.h> must be included
after <linux/module.h>.

I believe we should not impose any include order restriction. We often
sort include directives alphabetically, but it is just coding style
convention. Technically, we can include header files in any order by
making every header self-contained.

Currently, arch-specific MODULE_ARCH_VERMAGIC is defined in
<asm/module.h>, which is not included from <linux/vermagic.h>.

Hence, the straight-forward fix-up would be as follows:

|--- a/include/linux/vermagic.h
|+++ b/include/linux/vermagic.h
|@@ -1,5 +1,6 @@
| /* SPDX-License-Identifier: GPL-2.0 */
| #include <generated/utsrelease.h>
|+#include <linux/module.h>
|
| /* Simply sanity version stamp for modules. */
| #ifdef CONFIG_SMP

This works enough, but for further cleanups, I split MODULE_ARCH_VERMAGIC
definitions into <asm/vermagic.h>.

With this, <linux/module.h> and <linux/vermagic.h> will be orthogonal,
and the location of MODULE_ARCH_VERMAGIC definitions will be consistent.

For arc and ia64, MODULE_PROC_FAMILY is only used for defining
MODULE_ARCH_VERMAGIC. I squashed it.

For hexagon, nds32, and xtensa, I removed <asm/modules.h> entirely
because they contained nothing but MODULE_ARCH_VERMAGIC definition.
Kbuild will automatically generate <asm/modules.h> at build-time,
wrapping <asm-generic/module.h>.

[1] https://lore.kernel.org/lkml/20200411155623.GA22175@zn.tnic

Reported-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Jessica Yu <jeyu@kernel.org>

asm-generic: make more kernel-space headers mandatory

Change a header to mandatory-y if both of the following are met:

[1] At least one architecture (except um) specifies it as generic-y in
arch/*/include/asm/Kbuild

[2] Every architecture (except um) either has its own implementation
(arch/*/include/asm/*.h) or specifies it as generic-y in
arch/*/include/asm/Kbuild

This commit was generated by the following shell script.

----------------------------------->8-----------------------------------

arches=$(cd arch; ls -1 | sed -e '/Kconfig/d' -e '/um/d')

tmpfile=$(mktemp)

grep "^mandatory-y +=" include/asm-generic/Kbuild > $tmpfile

find arch -path 'arch/*/include/asm/Kbuild' |
xargs sed -n 's/^generic-y += \(.*\)/\1/p' | sort -u |
while read header
do
mandatory=yes

for arch in $arches
do
if ! grep -q "generic-y += $header" arch/$arch/include/asm/Kbuild &&
! [ -f arch/$arch/include/asm/$header ]; then
mandatory=no
break
fi
done

if [ "$mandatory" = yes ]; then
echo "mandatory-y += $header" >> $tmpfile

for arch in $arches
do
sed -i "/generic-y += $header/d" arch/$arch/include/asm/Kbuild
done
fi

done

sed -i '/^mandatory-y +=/d' include/asm-generic/Kbuild

LANG=C sort $tmpfile >> include/asm-generic/Kbuild

----------------------------------->8-----------------------------------

One obvious benefit is the diff stat:

25 files changed, 52 insertions(+), 557 deletions(-)

It is tedious to list generic-y for each arch that needs it.

So, mandatory-y works like a fallback default (by just wrapping
asm-generic one) when arch does not have a specific header
implementation.

See the following commits:

def3f7cefe4e81c296090e1722a76551142c227c
a1b39bae16a62ce4aae02d958224f19316d98b24

It is tedious to convert headers one by one, so I processed by a shell
script.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: http://lkml.kernel.org/r/20200210175452.5030-1-masahiroy@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

asm-generic: Make dma-contiguous.h a mandatory include/asm header

dma-continuguous.h is generic for all architectures except arm32 which has
its own version.

Similar change was done for msi.h by commit a1b39bae16a6
("asm-generic: Make msi.h a mandatory include/asm header")

Suggested-by: Christoph Hellwig <hch@infradead.org>
Link: https://lore.kernel.org/linux-arm-kernel/20200117080446.GA8980@lst.de/T/#m92bb56b04161057635d4142e1b3b9b6b0a70122e
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Paul Walmsley <paul.walmsley@sifive.com> # for arch/riscv

asm-generic: Make msi.h a mandatory include/asm header

msi.h is generic for all architectures except x86, which has its own
version. Enabling MSI by adding msi.h to every architecture's Kbuild is
just an additional step which doesn't need to be done.

Make msi.h mandatory in the asm-generic/Kbuild so we don't have to do it
for each architecture.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Link: https://lore.kernel.org/r/c991669e29a79b1a8e28c3b4b3a125801a693de8.1571983829.git.michal.simek@xilinx.com
Tested-by: Paul Walmsley <paul.walmsley@sifive.com> # build only, rv32/rv64
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Paul Walmsley <paul.walmsley@sifive.com> # arch/riscv

asm-generic: make simd.h a mandatory include/asm header

The generic aegis128 software crypto driver recently gained support
for using SIMD intrinsics to increase performance, for which it
uncondionally #include's the <asm/simd.h> header. Unfortunately,
this header does not exist on many architectures, resulting in
build failures.

Since asm-generic already has a version of simd.h, let's make it
a mandatory header so that it gets instantiated on all architectures
that don't provide their own version.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

kbuild: force all architectures except um to include mandatory-y

Currently, every arch/*/include/uapi/asm/Kbuild explicitly includes
the common Kbuild.asm file. Factor out the duplicated include directives
to scripts/Makefile.asm-generic so that no architecture would opt out
of the mandatory-y mechanism.

um is not forced to include mandatory-y since it is a very exceptional
case which does not support UAPI.

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

UAPI: Remove empty non-UAPI Kbuild files

Remove non-UAPI Kbuild files that have become empty as a result of UAPI
disintegration. They used to have only header-y lines in them and those have
now moved to the Kbuild files in the corresponding uapi/ directories.

Possibly these should not be removed but rather have a comment inserted to say
they are intentionally left blank. This would make it easier to add generated
header lines in future without having to restore the infrastructure.

Note that at this point not all the UAPI disintegration parts have been merged,
so it is likely that more empty Kbuild files will turn up.

It is probably necessary to make the files non-empty to prevent the patch
program from automatically deleting them when it reduces them to nothing.

Signed-off-by: David Howells <dhowells@redhat.com>

UAPI: (Scripted) Disintegrate include/asm-generic

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>

KVM: Export asm-generic/kvm_para.h

Prevents build failures on non-KVM archs.

Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Avi Kivity <avi@redhat.com>

include: replace unifdef-y with header-y

unifdef-y and header-y has same semantic.
So there is no need to have both.

Drop the unifdef-y variant and sort all lines again

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

asm-generic: add a generic unistd.h

A new architecture should only define a minimal set of system
calls while still providing the full functionality. This version
of unistd.h has gone through intensive review to make sure that
by default it only enables syscalls that do not already have
a more featureful replacement.

It is modeled after the x86-64 version of unistd.h, which unifies
the syscall number definition and the actual system call table
in a single file, in order to keep them synchronized much more
easily.

This first version still keeps legacy system call definitions
around, guarded by various #ifdefs, and with numbers larger
than 1024. The idea behind this is to make it easier for
new architectures to transition from a full list to the reduced
set. In particular, the new microblaze architecture that should
migrate to using the generic ABI headers can at least use an
existing uClibc source tree without major rewrites during the
conversion.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

asm-generic: add generic ABI headers

These header files are typically copied from an existing architecture
into any new one, slightly modified and then remain untouched until
the end of time in the name of ABI stability.

To make it easier for future architectures, provide a sane generic
version here. In cases where multiple architectures already use
identical code, I used the most common version. In cases like
stat.h that are more or less broken everywhere, I provide a
version that is meant to be ideal for new architectures.

Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

asm-generic: add generic sysv ipc headers

The ipc64 data structures were originally meant to
be architecture specific so that each architecture
could add their own optimizations for padding.

In the end, most of them just copied the x86 version,
and most got that wrong. UClibc expects the x86 anyway,
so we might just declare that the default and get
rid of the extra copies.

Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

asm-generic: introduce asm/bitsperlong.h

This provides a reliable way for asm-generic/types.h and other
files to find out if it is running on a 32 or 64 bit platform.

We cannot use CONFIG_64BIT for this in headers that are included
from user space because CONFIG symbols are not available there.
We also cannot do it inside of asm/types.h because some headers
need the word size but cannot include types.h.

The solution is to introduce a new header <asm/bitsperlong.h>
that defines both __BITS_PER_LONG for user space and
BITS_PER_LONG for usage in the kernel. The asm-generic
version falls back to 32 bit unless the architecture overrides
it, which I did for all 64 bit platforms.

Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

asm-generic: rename termios.h, signal.h and mman.h

The existing asm-generic versions are incomplete and included
by some architectures. New architectures should be able
to use a generic version, so rename the existing files and
change all users, which lets us add the new files.

Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

types: create <asm-generic/int-*.h>

This creates two generic files with common integer definitions; one
where 64 bits is "long" (most 64-bit architectures) and one where 64
bits is "long long" (all 32-bit architectures and x86-64.)

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Bryan Wu <cooloney@kernel.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Howells <dhowells@redhat.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Grant Grundler <grundler@parisc-linux.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Cc: Kyle McMartin <kyle@parisc-linux.org>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: William L. Irwin <wli@holomorphy.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>

remove include/asm-*/ipc.h

All asm/ipc.h files do only #include <asm-generic/ipc.h>.

This patch therefore removes all include/asm-*/ipc.h files and moves the
contents of include/asm-generic/ipc.h to include/linux/ipc.h.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Consolidate asm/poll.h

These files are almost all the same.

This patch could be made even simpler if we don't mind POLLREMOVE turning
up in a few architectures that didn't have it previously (which should be
OK as POLLREMOVE is not used anywhere in the current tree).

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

[PATCH] cleanup include/asm-generic/atomic.h

cleanup asm-generic/atomic.h

- no longer a userspace header
- remove the unneeded #include <asm/types.h>
- #else/#endif comments

[akpm@osdl.org: fix arm build]
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[HEADERS] One line per header in Kbuild files to reduce conflicts

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

Add generic Kbuild files for 'make headers_install'

This adds the Kbuild files listing the files which are to be installed by
the 'headers_install' make target, in generic directories.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>