Add user-mode implementations of gettimeofday() and clock_gettime() to
the VDSO. This is currently usable with 2 clocksources: the CP0 count
register, which is accessible to user-mode via RDHWR on R2 and later
cores, or the MIPS Global Interrupt Controller (GIC) timer, which
provides a "user-mode visible" section containing a mirror of its
counter registers. This section must be mapped into user memory, which
is done below the VDSO data page.

When a supported clocksource is not in use, the VDSO functions will
return -ENOSYS, which causes libc to fall back on the standard syscall
path.

When support for neither of these clocksources is compiled into the
kernel at all, the VDSO still provides clock_gettime(), as the coarse
realtime/monotonic clocks can still be implemented. However,
gettimeofday() is not provided in this case as nothing can be done
without a suitable clocksource. This causes the symbol lookup to fail
in libc and it will then always use the standard syscall path.

This patch includes a workaround for a bug in QEMU which results in
RDHWR on the CP0 count register always returning a constant (incorrect)
value. A fix for this has been submitted, and the workaround can be
removed after the fix has been in stable releases for a reasonable
amount of time.

A simple performance test which calls gettimeofday() 1000 times in a
loop and calculates the average execution time gives the following
results on a Malta + I6400 (running at 20MHz):

 - Syscall:    ~31000 ns
 - VDSO (GIC): ~15000 ns
 - VDSO (CP0): ~9500 ns

[markos.chandras@imgtec.com:
- Minor code re-arrangements in order for mappings to be made
in the order they appear to the process' address space.
- Move do_{monotonic, realtime} outside of the MIPS_CLOCK_VSYSCALL ifdef
- Use gic_get_usm_range so we can do the GIC mapping in the
arch/mips/kernel/vdso instead of the GIC irqchip driver]

Cc: linux-kernel@vger.kernel.org
Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

The GIC provides a "user-mode visible" section containing a mirror of
the counter registers which can be mapped into user memory. This will
be used by the VDSO time function implementations, so provide a
function to map it in.

When the GIC is not enabled in Kconfig a dummy inline version of this
function is provided, along with "#define gic_present 0", so that we
don't have to litter the VDSO code with ifdefs.

[markos.chandras@imgtec.com:
- Move mapping code to arch/mips/kernel/vdso.c and use a resource
type to get the GIC usermode information
- Avoid renaming function arguments and use __gic_base_addr to hold
the base GIC address prior to ioremap.]

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

Add an initial implementation of a proper (i.e. an ELF shared library)
VDSO. With this commit it does not export any symbols, it only replaces
the current signal return trampoline page. A later commit will add user
implementations of gettimeofday()/clock_gettime().

To support both new toolchains and old ones which don't generate ABI
flags section, we define its content manually and then use a tool
(genvdso) to patch up the section to have the correct name and type.
genvdso also extracts symbol offsets ({,rt_}sigreturn) needed by the
kernel, and generates a C file containing a "struct mips_vdso_image"
containing both the VDSO data and these offsets. This C file is
compiled into the kernel.

On 64-bit kernels we require a different VDSO for each supported ABI,
so we may build up to 3 different VDSOs. The VDSO to use is selected by
the mips_abi structure.

A kernel/user shared data page is created and mapped below the VDSO
image. This is currently empty, but will be used by the user time
function implementations which are added later.

[markos.chandras@imgtec.com:
- Add more comments
- Move abi detection in genvdso.h since it's the get_symbol function
that needs it.
- Add an R6 specific way to calculate the base address of VDSO in order
to avoid the branch instruction which affects performance.
- Do not patch .gnu.attributes since it's not needed for dynamic linking.
- Simplify Makefile a little bit.
- checkpatch fixes]

Cc: Matthew Fortune <matthew.fortune@imgtec.com>
Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

Pull x86 fixes from Thomas Gleixner:
 "Two bugfixes from Andy addressing at least some of the subtle NMI
  related wreckage which has been reported by Sasha Levin"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code
  x86/paravirt: Replace the paravirt nop with a bona fide empty function

Pull irq fix from Thomass Gleixner:
 "A bugfix for the atmel aic5 irq chip driver which caches the wrong
  data and thereby breaking resume"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/atmel-aic5: Use per chip mask caches in mask/unmask()

Pull ARM fixes from Russell King:
 "Just two fixes: wire up the new system calls added during the last
  merge window, and fix another user access site"

* 'fixes' of git://ftp.arm.linux.org.uk/~rmk/linux-arm:
  ARM: alignment: fix alignment handling for uaccess changes
  ARM: wire up new syscalls

Pull ARM SoC fixes from Olof Johansson:
 "Our first real batch of fixes this release cycle.  Nothing really
  concerning, and diffstat is a bit inflated due to some DT contents
  moving around on STi platforms.

  There's a collection of them here:

   - A fixup for a build breakage that hits on arm64 allmodconfig in
     QCOM SCM firmware drivers
   - MMC fixes for OMAP that had quite a bit of breakage this merge
     window.
   - Misc build/warning fixes on PXA and OMAP
   - A couple of minor fixes for Beagleboard X15 which is now starting
     to see a few more users in the wild"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (31 commits)
  ARM: sti: dt: adapt DT to fix probe/bind issues in DRM driver
  ARM: dts: fix omap2+ address translation for pbias
  firmware: qcom: scm: Add function stubs for ARM64
  ARM: dts: am57xx-beagle-x15: use palmas-usb for USB2
  ARM: omap2plus_defconfig: enable GPIO_PCA953X
  ARM: dts: omap5-uevm.dts: fix i2c5 pinctrl offsets
  ARM: OMAP2+: AM43XX: Enable autoidle for clks in am43xx_init_late
  ARM: dts: am57xx-beagle-x15: Update Phy supplies
  ARM: pxa: balloon3: Fix build error
  ARM: dts: Fixup model name for HP t410 dts
  ARM: dts: DRA7: fix a typo in ethernet
  ARM: omap2plus_defconfig: make PCF857x built-in
  ARM: dts: Use ti,pbias compatible string for pbias
  ARM: OMAP5: Cleanup options for SoC only build
  ARM: DRA7: Select missing options for SoC only build
  ARM: OMAP2+: board-generic: Remove stale of_irq macros
  ARM: OMAP4+: PM: erratum is used by OMAP5 and DRA7 as well
  ARM: dts: omap3-igep: Move eth IRQ pinmux to IGEPv2 common dtsi
  ARM: dts: am57xx-beagle-x15: Add wakeup irq for mcp79410
  ARM: dts: am335x-phycore-som: Fix mpu voltage
  ...

Pull CIFS fixes from Steve French:
 "Four fixes from testing at the recent SMB3 Plugfest including two
  important authentication ones (one fixes authentication problems to
  some popular servers when clock times differ more than two hours
  between systems, the other fixes Kerberos authentication for SMB3)"

* 'for-next' of git://git.samba.org/sfrench/cifs-2.6:
  fix encryption error checks on mount
  [SMB3] Fix sec=krb5 on smb3 mounts
  cifs: use server timestamp for ntlmv2 authentication
  disabling oplocks/leases via module parm enable_oplocks broken for SMB3

ARM: pxa: fixes for v4.3

These fixes are mainly regression fixes triggered by irq changes,
common clock framework introduction and sound side-effect of
other platforms.

* tag 'pxa-fixes-v4.3' of https://github.com/rjarzmik/linux:
  ARM: pxa: balloon3: Fix build error
  ARM: pxa: ssp: Fix build error by removing originally incorrect DT binding
  ARM: pxa: fix DFI bus lockups on startup

Signed-off-by: Olof Johansson <olof@lixom.net>