prctl: avoid using mmap_sem for exe_file serialization

Oleg cleverly suggested using xchg() to set the new mm->exe_file instead
of calling set_mm_exe_file() which requires some form of serialization --
mmap_sem in this case.  For archs that do not have atomic rmw instructions
we still fallback to a spinlock alternative, so this should always be
safe.  As such, we only need the mmap_sem for looking up the backing
vm_file, which can be done sharing the lock.  Naturally, this means we
need to manually deal with both the new and old file reference counting,
and we need not worry about the MMF_EXE_FILE_CHANGED bits, which can
probably be deleted in the future anyway.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tomoyo-reduce-mmap_sem-hold-for-mm-exe_file-checkpatch-fixes

Sumeone needs to buy a tab key.

WARNING: please, no spaces at the start of a line
#29: FILE: security/tomoyo/util.c:951:
+       struct file *exe_file;$

WARNING: please, no spaces at the start of a line
#30: FILE: security/tomoyo/util.c:952:
+       const char *cp;$

WARNING: please, no spaces at the start of a line
#31: FILE: security/tomoyo/util.c:953:
+       struct mm_struct *mm = current->mm;$

WARNING: please, no spaces at the start of a line
#40: FILE: security/tomoyo/util.c:955:
+       if (!mm)$

WARNING: suspect code indent for conditional statements (7, 15)
#40: FILE: security/tomoyo/util.c:955:
+       if (!mm)
+        return NULL;

WARNING: please, no spaces at the start of a line
#42: FILE: security/tomoyo/util.c:957:
+       exe_file = get_mm_exe_file(mm);$

WARNING: please, no spaces at the start of a line
#43: FILE: security/tomoyo/util.c:958:
+       if (!exe_file)$

WARNING: suspect code indent for conditional statements (7, 15)
#43: FILE: security/tomoyo/util.c:958:
+       if (!exe_file)
+        return NULL;

WARNING: please, no spaces at the start of a line
#46: FILE: security/tomoyo/util.c:961:
+       cp = tomoyo_realpath_from_path(&exe_file->f_path);$

WARNING: please, no spaces at the start of a line
#47: FILE: security/tomoyo/util.c:962:
+       fput(exe_file);$

WARNING: please, no spaces at the start of a line
#48: FILE: security/tomoyo/util.c:963:
+       return cp;$

total: 0 errors, 11 warnings, 28 lines checked

./patches/tomoyo-reduce-mmap_sem-hold-for-mm-exe_file.patch has style problems, please review.

If any of these errors are false positives, please report
them to the maintainer, see CHECKPATCH in MAINTAINERS.

Please run checkpatch prior to sending patches

Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: James Morris <jmorris@namei.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tomoyo: reduce mmap_sem hold for mm->exe_file

The mm->exe_file is currently serialized with mmap_sem (shared) in order
to both safely (1) read the file and (2) compute the realpath by calling
tomoyo_realpath_from_path, making it an absolute overkill.  Good users
will, on the other hand, make use of the more standard get_mm_exe_file(),
requiring only holding the mmap_sem to read the value, and relying on
reference

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

oprofile-reduce-mmap_sem-hold-for-mm-exe_file-fix

export get_mm_exe_file for arch/x86/oprofile/oprofile.ko

Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Robert Richter <rric@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

powerpc/oprofile: reduce mmap_sem hold for exe_file

In the future mm->exe_file will be done without mmap_sem serialization,
thus isolate and reorganize the related code to make the transition
easier.  Good users will, make use of the more standard get_mm_exe_file(),
requiring only holding the mmap_sem to read the value, and relying on
reference counting to make sure that the exe file won't dissappear
underneath us while getting the dcookie.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Robert Richter <rric@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

oprofile: reduce mmap_sem hold for mm->exe_file

sync_buffer() needs the mmap_sem for two distinct operations, both only
occurring upon user context switch handling:

 1) Dealing with the exe_file.

 2) Adding the dcookie data as we need to lookup the vma that
   backs it. This is done via add_sample() and add_data().

This patch isolates 1), for it will no longer need the mmap_sem for
serialization.  However, for now, make of the more standard
get_mm_exe_file(), requiring only holding the mmap_sem to read the value,
and relying on reference counting to make sure that the exe file won't
dissappear underneath us while doing the get dcookie.

As a consequence, for 2) we move the mmap_sem locking into where we really
need it, in lookup_dcookie().  The benefits are twofold: reduce mmap_sem
hold times, and cleaner code.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Robert Richter <rric@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mips: ip32: add platform data hooks to use DS1685 driver

This modifies the IP32 (SGI O2) platform and reset code to utilize the new
rtc-ds1685 driver.  The old mc146818rtc.h header is removed and ip32_defconfig
is updated as well.

Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/Kconfig: fix up HAVE_ARCH_BITREVERSE help text

Cc: Yalin Wang <yalin.wang@sonymobile.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/unicore32/kernel/fpu-ucf64.c: remove unnecessary KERN_ERR

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Merge branch 'akpm-current/current'

Conflicts:
Documentation/printk-formats.txt
arch/arm64/Kconfig
arch/parisc/include/asm/Kbuild
arch/s390/mm/mmap.c
drivers/rtc/class.c
drivers/rtc/rtc-mc13xxx.c
fs/ext2/file.c
fs/ext4/file.c
fs/fat/inode.c

Merge remote-tracking branch 'livepatching/for-next'

Conflicts:
arch/s390/Kconfig

Merge remote-tracking branch 'y2038/y2038'

Conflicts:
drivers/staging/media/lirc/lirc_parallel.c

Merge remote-tracking branch 'kselftest/next'

Conflicts:
tools/testing/selftests/powerpc/Makefile

Merge remote-tracking branch 'llvmlinux/for-next'

Merge remote-tracking branch 'clk/clk-next'

Merge remote-tracking branch 'dma-buf/for-next'

Merge remote-tracking branch 'pwm/for-next'

Merge remote-tracking branch 'dma-mapping/dma-mapping-next'

Merge remote-tracking branch 'gpio/for-next'

Merge remote-tracking branch 'remoteproc/for-next'

Merge remote-tracking branch 'vhost/linux-next'

Conflicts:
drivers/usb/dwc3/dwc3-pci.c

Merge remote-tracking branch 'pinctrl/for-next'

Merge remote-tracking branch 'target-updates/for-next'

Merge remote-tracking branch 'scsi/for-next'

Merge remote-tracking branch 'cgroup/for-next'

Merge remote-tracking branch 'kdbus/kdbus'

Conflicts:
Documentation/Makefile

Merge remote-tracking branch 'extcon/extcon-next'

Merge remote-tracking branch 'char-misc/char-misc-next'

Merge remote-tracking branch 'staging/staging-next'

Conflicts:
drivers/staging/media/mn88473/mn88473.c

Merge remote-tracking branch 'usb-gadget/next'

Merge remote-tracking branch 'usb/usb-next'

Merge remote-tracking branch 'tty/tty-next'

Conflicts:
drivers/dma/Kconfig

Merge remote-tracking branch 'driver-core/driver-core-next'

Merge remote-tracking branch 'ipmi/for-next'

Merge remote-tracking branch 'leds/for-next'

Merge remote-tracking branch 'hsi/for-next'

Merge remote-tracking branch 'regmap/for-next'

Merge remote-tracking branch 'chrome-platform/for-next'

Merge remote-tracking branch 'drivers-x86/for-next'

Merge remote-tracking branch 'workqueues/for-next'

Merge remote-tracking branch 'xen-tip/linux-next'

Conflicts:
drivers/xen/Kconfig

Merge remote-tracking branch 'kvm/linux-next'

Conflicts:
arch/mips/kernel/genex.S

Merge remote-tracking branch 'rcu/rcu/next'

Merge remote-tracking branch 'ftrace/for-next'

Merge remote-tracking branch 'irqchip/irqchip/for-next'

Conflicts:
arch/arm/mach-exynos/suspend.c

Merge remote-tracking branch 'edac-amd/for-next'

Merge remote-tracking branch 'clockevents/clockevents/next'

Conflicts:
arch/arm/mach-rockchip/Kconfig
drivers/clocksource/Kconfig
drivers/clocksource/rockchip_timer.c

Merge remote-tracking branch 'tip/auto-latest'

Conflicts:
include/linux/bpf.h
include/uapi/linux/bpf.h
samples/bpf/Makefile

Merge remote-tracking branch 'spi/for-next'

Conflicts:
drivers/dma/intel_mid_dma.c
drivers/dma/intel_mid_dma_regs.h

Merge remote-tracking branch 'mailbox/mailbox-for-next'

Merge remote-tracking branch 'devicetree/devicetree/next'

Conflicts:
Documentation/devicetree/bindings/mips/brcm/brcm,bcm3384-intc.txt
Documentation/devicetree/bindings/mips/brcm/brcm,cm-dsl.txt

Merge remote-tracking branch 'audit/next'

Merge remote-tracking branch 'trivial/for-next'

Merge remote-tracking branch 'jc_docs/docs-next'

Merge remote-tracking branch 'vfio/next'

Merge remote-tracking branch 'dwmw2-iommu/master'

Merge remote-tracking branch 'iommu/next'

Merge remote-tracking branch 'watchdog/master'

Merge remote-tracking branch 'selinux/next'

Merge remote-tracking branch 'integrity/next'

Merge remote-tracking branch 'security/next'

Conflicts:
drivers/char/tpm/tpm-chip.c

Merge remote-tracking branch 'regulator/for-next'

Merge remote-tracking branch 'omap_dss2/for-next'

Merge remote-tracking branch 'battery/master'

Conflicts:
drivers/hid/wacom.h
drivers/hid/wacom_sys.c

Merge remote-tracking branch 'backlight/for-backlight-next'

Merge remote-tracking branch 'mfd/for-mfd-next'

Merge remote-tracking branch 'md/for-next'

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Merge remote-tracking branch 'input/next'

Merge remote-tracking branch 'virtio/virtio-next'

Merge remote-tracking branch 'modules/modules-next'

Merge remote-tracking branch 'sound-asoc/for-next'

Merge remote-tracking branch 'sound/for-next'

Merge remote-tracking branch 'drm-exynos/exynos-drm/for-next'

Merge remote-tracking branch 'drm-misc/topic/drm-misc'

Merge remote-tracking branch 'drm/drm-next'

Merge remote-tracking branch 'crypto/master'

Conflicts:
crypto/Kconfig

Merge remote-tracking branch 'l2-mtd/master'

Merge remote-tracking branch 'bluetooth/master'

Merge remote-tracking branch 'wireless-drivers-next/master'

Merge remote-tracking branch 'ipsec-next/master'

Merge remote-tracking branch 'slave-dma/next'

Conflicts:
arch/arm/mach-shmobile/board-ape6evm.c
arch/arm/mach-shmobile/board-mackerel.c

Merge remote-tracking branch 'thermal-soc/next'

Merge remote-tracking branch 'thermal/next'

Merge remote-tracking branch 'idle/next'

Merge remote-tracking branch 'pm/linux-next'

Merge remote-tracking branch 'libata/for-next'

Merge remote-tracking branch 'kbuild/for-next'

Merge remote-tracking branch 'v4l-dvb/master'

Merge remote-tracking branch 'hwmon-staging/hwmon-next'

Merge remote-tracking branch 'i2c/i2c/for-next'

Merge remote-tracking branch 'hid/for-next'

Merge remote-tracking branch 'pci/next'

Merge remote-tracking branch 'vfs/for-next'

Conflicts:
fs/ext4/inode.c
fs/udf/file.c
net/9p/protocol.c

Merge remote-tracking branch 'net-next/master'

Merge remote-tracking branch 'file-locks/linux-next'

Merge remote-tracking branch 'xfs/for-next'