linux.git/arch/arc, branch v4.13-rc2 Linux kernel source tree arc: move generic-y of exported headers to uapi/asm/Kbuild 2017-07-09T18:43:21+00:00 Masahiro Yamada yamada.masahiro@socionext.com 2017-07-09T18:32:38+00:00 3e4f9376659d8646302a317848ffb3a12101aa89 Since commit fcc8487d477a ("uapi: export all headers under uapi directories"), all (and only) headers under uapi directories are exported, but asm-generic wrappers are still exceptions. To complete de-coupling the uapi from kernel headers, move generic-y of exported headers to uapi/asm/Kbuild. With this change, "make headers_install" will just need to parse uapi/asm/Kbuild to build up exported headers. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> 
Since commit fcc8487d477a ("uapi: export all headers under uapi
directories"), all (and only) headers under uapi directories are
exported, but asm-generic wrappers are still exceptions.

To complete de-coupling the uapi from kernel headers, move generic-y
of exported headers to uapi/asm/Kbuild.

With this change, "make headers_install" will just need to parse
uapi/asm/Kbuild to build up exported headers.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-03T23:14:51+00:00 Linus Torvalds torvalds@linux-foundation.org 2017-07-03T23:14:51+00:00 1b044f1cfc65a7d90b209dfabd57e16d98b58c5b Pull timer updates from Thomas Gleixner: "A rather large update for timers/timekeeping: - compat syscall consolidation (Al Viro) - Posix timer consolidation (Christoph Helwig / Thomas Gleixner) - Cleanup of the device tree based initialization for clockevents and clocksources (Daniel Lezcano) - Consolidation of the FTTMR010 clocksource/event driver (Linus Walleij) - The usual set of small fixes and updates all over the place" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (93 commits) timers: Make the cpu base lock raw clocksource/drivers/mips-gic-timer: Fix an error code in 'gic_clocksource_of_init()' clocksource/drivers/fsl_ftm_timer: Unmap region obtained by of_iomap clocksource/drivers/tcb_clksrc: Make IO endian agnostic clocksource/drivers/sun4i: Switch to the timer-of common init clocksource/drivers/timer-of: Fix invalid iomap check Revert "ktime: Simplify ktime_compare implementation" clocksource/drivers: Fix uninitialized variable use in timer_of_init kselftests: timers: Add test for frequency step kselftests: timers: Fix inconsistency-check to not ignore first timestamp time: Add warning about imminent deprecation of CONFIG_GENERIC_TIME_VSYSCALL_OLD time: Clean up CLOCK_MONOTONIC_RAW time handling posix-cpu-timers: Make timespec to nsec conversion safe itimer: Make timeval to nsec conversion range limited timers: Fix parameter description of try_to_del_timer_sync() ktime: Simplify ktime_compare implementation clocksource/drivers/fttmr010: Factor out clock read code clocksource/drivers/fttmr010: Implement delay timer clocksource/drivers: Add timer-of common init routine clocksource/drivers/tcb_clksrc: Save timer context on suspend/resume ... 
Pull timer updates from Thomas Gleixner:
 "A rather large update for timers/timekeeping:

   - compat syscall consolidation (Al Viro)

   - Posix timer consolidation (Christoph Helwig / Thomas Gleixner)

   - Cleanup of the device tree based initialization for clockevents and
     clocksources (Daniel Lezcano)

   - Consolidation of the FTTMR010 clocksource/event driver (Linus
     Walleij)

   - The usual set of small fixes and updates all over the place"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (93 commits)
  timers: Make the cpu base lock raw
  clocksource/drivers/mips-gic-timer: Fix an error code in 'gic_clocksource_of_init()'
  clocksource/drivers/fsl_ftm_timer: Unmap region obtained by of_iomap
  clocksource/drivers/tcb_clksrc: Make IO endian agnostic
  clocksource/drivers/sun4i: Switch to the timer-of common init
  clocksource/drivers/timer-of: Fix invalid iomap check
  Revert "ktime: Simplify ktime_compare implementation"
  clocksource/drivers: Fix uninitialized variable use in timer_of_init
  kselftests: timers: Add test for frequency step
  kselftests: timers: Fix inconsistency-check to not ignore first timestamp
  time: Add warning about imminent deprecation of CONFIG_GENERIC_TIME_VSYSCALL_OLD
  time: Clean up CLOCK_MONOTONIC_RAW time handling
  posix-cpu-timers: Make timespec to nsec conversion safe
  itimer: Make timeval to nsec conversion range limited
  timers: Fix parameter description of try_to_del_timer_sync()
  ktime: Simplify ktime_compare implementation
  clocksource/drivers/fttmr010: Factor out clock read code
  clocksource/drivers/fttmr010: Implement delay timer
  clocksource/drivers: Add timer-of common init routine
  clocksource/drivers/tcb_clksrc: Save timer context on suspend/resume
  ...
arch: remove unused macro/function thread_saved_pc() 2017-06-28T23:13:57+00:00 Tobias Klauser tklauser@distanz.ch 2017-06-28T13:30:02+00:00 6474924e2b5ddb0030c355558966adcbe3b49022 The only user of thread_saved_pc() in non-arch-specific code was removed in commit 8243d5597793 ("sched/core: Remove pointless printout in sched_show_task()"). Remove the implementations as well. Some architectures use thread_saved_pc() in their arch-specific code. Leave their thread_saved_pc() intact. Signed-off-by: Tobias Klauser <tklauser@distanz.ch> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
The only user of thread_saved_pc() in non-arch-specific code was removed
in commit 8243d5597793 ("sched/core: Remove pointless printout in
sched_show_task()").  Remove the implementations as well.

Some architectures use thread_saved_pc() in their arch-specific code.
Leave their thread_saved_pc() intact.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge branch 'timers/urgent' into timers/core 2017-06-21T07:07:52+00:00 Thomas Gleixner tglx@linutronix.de 2017-06-21T07:07:52+00:00 f0cd9ae5d0df8668e76359a3e0e99856aa9c53b9 Pick up dependent changes. 
Pick up dependent changes.
mm: larger stack guard gap, between vmas 2017-06-19T13:50:20+00:00 Hugh Dickins hughd@google.com 2017-06-19T11:03:24+00:00 1be7107fbe18eed3e319a6c3e83c78254b693acb Stack guard page is a useful feature to reduce a risk of stack smashing into a different mapping. We have been using a single page gap which is sufficient to prevent having stack adjacent to a different mapping. But this seems to be insufficient in the light of the stack usage in userspace. E.g. glibc uses as large as 64kB alloca() in many commonly used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX] which is 256kB or stack strings with MAX_ARG_STRLEN. This will become especially dangerous for suid binaries and the default no limit for the stack size limit because those applications can be tricked to consume a large portion of the stack and a single glibc call could jump over the guard page. These attacks are not theoretical, unfortunatelly. Make those attacks less probable by increasing the stack guard gap to 1MB (on systems with 4k pages; but make it depend on the page size because systems with larger base pages might cap stack allocations in the PAGE_SIZE units) which should cover larger alloca() and VLA stack allocations. It is obviously not a full fix because the problem is somehow inherent, but it should reduce attack space a lot. One could argue that the gap size should be configurable from userspace, but that can be done later when somebody finds that the new 1MB is wrong for some special case applications. For now, add a kernel command line option (stack_guard_gap) to specify the stack gap size (in page units). Implementation wise, first delete all the old code for stack guard page: because although we could get away with accounting one extra page in a stack vma, accounting a larger gap can break userspace - case in point, a program run with "ulimit -S -v 20000" failed when the 1MB gap was counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK and strict non-overcommit mode. Instead of keeping gap inside the stack vma, maintain the stack guard gap as a gap between vmas: using vm_start_gap() in place of vm_start (or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few places which need to respect the gap - mainly arch_get_unmapped_area(), and and the vma tree's subtree_gap support for that. Original-patch-by: Oleg Nesterov <oleg@redhat.com> Original-patch-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Tested-by: Helge Deller <deller@gmx.de> # parisc Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.

Original-patch-by: Oleg Nesterov <oleg@redhat.com>
Original-patch-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
clocksource/drivers: Rename clocksource_probe to timer_probe 2017-06-14T09:59:16+00:00 Daniel Lezcano daniel.lezcano@linaro.org 2017-05-26T15:40:46+00:00 ba5d08c0ea785d5710c5a1e7dc3182b7124d63c0 The function name is now renamed to 'timer_probe' for consistency with the CLOCKSOURCE_OF_DECLARE => TIMER_OF_DECLARE change. Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Heiko Stuebner <heiko@sntech.de> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> 
The function name is now renamed to 'timer_probe' for consistency with
the CLOCKSOURCE_OF_DECLARE => TIMER_OF_DECLARE change.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
signal: Remove non-uapi <asm/siginfo.h> 2017-06-04T13:11:47+00:00 Christoph Hellwig hch@lst.de 2017-06-03T19:01:02+00:00 6bc51cbaa9d75c7c240282da5ff270815caccac0 By moving the kernel side __SI_* defintions right next to the userspace ones we can kill the non-uapi versions of <asm/siginfo.h> include include/asm-generic/siginfo.h and untangle the unholy mess of includes. [ tglx: Removed uapi/asm/siginfo.h from m32r, microblaze, mn10300 and score ] Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch@vger.kernel.org Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: linux-ia64@vger.kernel.org Cc: Arnd Bergmann <arnd@arndb.de> Cc: sparclinux@vger.kernel.org Cc: "David S. Miller" <davem@davemloft.net> Link: http://lkml.kernel.org/r/20170603190102.28866-6-hch@lst.de 
By moving the kernel side __SI_* defintions right next to the userspace
ones we can kill the non-uapi versions of <asm/siginfo.h> include
include/asm-generic/siginfo.h and untangle the unholy mess of includes.

[ tglx: Removed uapi/asm/siginfo.h from m32r, microblaze, mn10300 and score ]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-ia64@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: sparclinux@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20170603190102.28866-6-hch@lst.de
Merge tag 'kbuild-uapi-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild 2017-05-11T03:45:36+00:00 Linus Torvalds torvalds@linux-foundation.org 2017-05-11T03:45:36+00:00 791a9a666d1afe2603bcb2c6a4852d684e879252 Pull Kbuild UAPI updates from Masahiro Yamada: "Improvement of headers_install by Nicolas Dichtel. It has been long since the introduction of uapi directories, but the de-coupling of exported headers has not been completed. Headers listed in header-y are exported whether they exist in uapi directories or not. His work fixes this inconsistency. All (and only) headers under uapi directories are now exported. The asm-generic wrappers are still exceptions, but this is a big step forward" * tag 'kbuild-uapi-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: arch/include: remove empty Kbuild files uapi: export all arch specifics directories uapi: export all headers under uapi directories smc_diag.h: fix include from userland btrfs_tree.h: fix include from userland uapi: includes linux/types.h before exporting files Makefile.headersinst: remove destination-y option Makefile.headersinst: cleanup input files x86: stop exporting msr-index.h to userland nios2: put setup.h in uapi h8300: put bitsperlong.h in uapi 
Pull Kbuild UAPI updates from Masahiro Yamada:
 "Improvement of headers_install by Nicolas Dichtel.

  It has been long since the introduction of uapi directories, but the
  de-coupling of exported headers has not been completed. Headers listed
  in header-y are exported whether they exist in uapi directories or
  not. His work fixes this inconsistency.

  All (and only) headers under uapi directories are now exported. The
  asm-generic wrappers are still exceptions, but this is a big step
  forward"

* tag 'kbuild-uapi-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  arch/include: remove empty Kbuild files
  uapi: export all arch specifics directories
  uapi: export all headers under uapi directories
  smc_diag.h: fix include from userland
  btrfs_tree.h: fix include from userland
  uapi: includes linux/types.h before exporting files
  Makefile.headersinst: remove destination-y option
  Makefile.headersinst: cleanup input files
  x86: stop exporting msr-index.h to userland
  nios2: put setup.h in uapi
  h8300: put bitsperlong.h in uapi
Merge tag 'kbuild-misc-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild 2017-05-11T03:41:43+00:00 Linus Torvalds torvalds@linux-foundation.org 2017-05-11T03:41:43+00:00 23ea3f62f3f90caaa7b4bf32690c341101228cca Pull misc Kbuild updates from Masahiro Yamada: - clean up builddeb script - use full path for KBUILD_IMAGE to fix rpm-pkg build - fix objdiff tool to ignore debug info * tag 'kbuild-misc-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: builddeb: fix typo builddeb: Update a few outdated and hardcoded strings deb-pkg: Remove the KBUILD_IMAGE workaround unicore32: Use full path in KBUILD_IMAGE definition sh: Use full path in KBUILD_IMAGE definition arc: Use full path in KBUILD_IMAGE definition arm: Use full path in KBUILD_IMAGE definition arm64: Use full path in KBUILD_IMAGE definition scripts: objdiff: Ignore debug info when comparing 
Pull misc Kbuild updates from Masahiro Yamada:

 - clean up builddeb script

 - use full path for KBUILD_IMAGE to fix rpm-pkg build

 - fix objdiff tool to ignore debug info

* tag 'kbuild-misc-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  builddeb: fix typo
  builddeb: Update a few outdated and hardcoded strings
  deb-pkg: Remove the KBUILD_IMAGE workaround
  unicore32: Use full path in KBUILD_IMAGE definition
  sh: Use full path in KBUILD_IMAGE definition
  arc: Use full path in KBUILD_IMAGE definition
  arm: Use full path in KBUILD_IMAGE definition
  arm64: Use full path in KBUILD_IMAGE definition
  scripts: objdiff: Ignore debug info when comparing
uapi: export all headers under uapi directories 2017-05-10T15:21:54+00:00 Nicolas Dichtel nicolas.dichtel@6wind.com 2017-03-27T12:20:15+00:00 fcc8487d477a3452a1d0ccbdd4c5e0e1e3cb8bed Regularly, when a new header is created in include/uapi/, the developer forgets to add it in the corresponding Kbuild file. This error is usually detected after the release is out. In fact, all headers under uapi directories should be exported, thus it's useless to have an exhaustive list. After this patch, the following files, which were not exported, are now exported (with make headers_install_all): asm-arc/kvm_para.h asm-arc/ucontext.h asm-blackfin/shmparam.h asm-blackfin/ucontext.h asm-c6x/shmparam.h asm-c6x/ucontext.h asm-cris/kvm_para.h asm-h8300/shmparam.h asm-h8300/ucontext.h asm-hexagon/shmparam.h asm-m32r/kvm_para.h asm-m68k/kvm_para.h asm-m68k/shmparam.h asm-metag/kvm_para.h asm-metag/shmparam.h asm-metag/ucontext.h asm-mips/hwcap.h asm-mips/reg.h asm-mips/ucontext.h asm-nios2/kvm_para.h asm-nios2/ucontext.h asm-openrisc/shmparam.h asm-parisc/kvm_para.h asm-powerpc/perf_regs.h asm-sh/kvm_para.h asm-sh/ucontext.h asm-tile/shmparam.h asm-unicore32/shmparam.h asm-unicore32/ucontext.h asm-x86/hwcap2.h asm-xtensa/kvm_para.h drm/armada_drm.h drm/etnaviv_drm.h drm/vgem_drm.h linux/aspeed-lpc-ctrl.h linux/auto_dev-ioctl.h linux/bcache.h linux/btrfs_tree.h linux/can/vxcan.h linux/cifs/cifs_mount.h linux/coresight-stm.h linux/cryptouser.h linux/fsmap.h linux/genwqe/genwqe_card.h linux/hash_info.h linux/kcm.h linux/kcov.h linux/kfd_ioctl.h linux/lightnvm.h linux/module.h linux/nbd-netlink.h linux/nilfs2_api.h linux/nilfs2_ondisk.h linux/nsfs.h linux/pr.h linux/qrtr.h linux/rpmsg.h linux/sched/types.h linux/sed-opal.h linux/smc.h linux/smc_diag.h linux/stm.h linux/switchtec_ioctl.h linux/vfio_ccw.h linux/wil6210_uapi.h rdma/bnxt_re-abi.h Note that I have removed from this list the files which are generated in every exported directories (like .install or .install.cmd). Thanks to Julien Floret <julien.floret@6wind.com> for the tip to get all subdirs with a pure makefile command. For the record, note that exported files for asm directories are a mix of files listed by: - include/uapi/asm-generic/Kbuild.asm; - arch/<arch>/include/uapi/asm/Kbuild; - arch/<arch>/include/asm/Kbuild. Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Russell King <rmk+kernel@armlinux.org.uk> Acked-by: Mark Salter <msalter@redhat.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> 
Regularly, when a new header is created in include/uapi/, the developer
forgets to add it in the corresponding Kbuild file. This error is usually
detected after the release is out.

In fact, all headers under uapi directories should be exported, thus it's
useless to have an exhaustive list.

After this patch, the following files, which were not exported, are now
exported (with make headers_install_all):
asm-arc/kvm_para.h
asm-arc/ucontext.h
asm-blackfin/shmparam.h
asm-blackfin/ucontext.h
asm-c6x/shmparam.h
asm-c6x/ucontext.h
asm-cris/kvm_para.h
asm-h8300/shmparam.h
asm-h8300/ucontext.h
asm-hexagon/shmparam.h
asm-m32r/kvm_para.h
asm-m68k/kvm_para.h
asm-m68k/shmparam.h
asm-metag/kvm_para.h
asm-metag/shmparam.h
asm-metag/ucontext.h
asm-mips/hwcap.h
asm-mips/reg.h
asm-mips/ucontext.h
asm-nios2/kvm_para.h
asm-nios2/ucontext.h
asm-openrisc/shmparam.h
asm-parisc/kvm_para.h
asm-powerpc/perf_regs.h
asm-sh/kvm_para.h
asm-sh/ucontext.h
asm-tile/shmparam.h
asm-unicore32/shmparam.h
asm-unicore32/ucontext.h
asm-x86/hwcap2.h
asm-xtensa/kvm_para.h
drm/armada_drm.h
drm/etnaviv_drm.h
drm/vgem_drm.h
linux/aspeed-lpc-ctrl.h
linux/auto_dev-ioctl.h
linux/bcache.h
linux/btrfs_tree.h
linux/can/vxcan.h
linux/cifs/cifs_mount.h
linux/coresight-stm.h
linux/cryptouser.h
linux/fsmap.h
linux/genwqe/genwqe_card.h
linux/hash_info.h
linux/kcm.h
linux/kcov.h
linux/kfd_ioctl.h
linux/lightnvm.h
linux/module.h
linux/nbd-netlink.h
linux/nilfs2_api.h
linux/nilfs2_ondisk.h
linux/nsfs.h
linux/pr.h
linux/qrtr.h
linux/rpmsg.h
linux/sched/types.h
linux/sed-opal.h
linux/smc.h
linux/smc_diag.h
linux/stm.h
linux/switchtec_ioctl.h
linux/vfio_ccw.h
linux/wil6210_uapi.h
rdma/bnxt_re-abi.h

Note that I have removed from this list the files which are generated in every
exported directories (like .install or .install.cmd).

Thanks to Julien Floret <julien.floret@6wind.com> for the tip to get all
subdirs with a pure makefile command.

For the record, note that exported files for asm directories are a mix of
files listed by:
 - include/uapi/asm-generic/Kbuild.asm;
 - arch/<arch>/include/uapi/asm/Kbuild;
 - arch/<arch>/include/asm/Kbuild.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Mark Salter <msalter@redhat.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>