This adds support for tracing callchains for powerpc, both 32-bit
and 64-bit, and both in the kernel and userspace, from PMU interrupt
context.

The first three entries stored for each callchain are the NIP (next
instruction pointer), LR (link register), and the contents of the LR
save area in the second stack frame (the first is ignored because the
ABI convention on powerpc is that functions save their return address
in their caller's stack frame).  Because leaf functions don't have to
save their return address (LR value) and don't have to establish a
stack frame, it's possible for either or both of LR and the second
stack frame's LR save area to have valid return addresses in them.
This is basically impossible to disambiguate without either reading
the code or looking at auxiliary information such as CFI tables.
Since we don't want to do either of those things at interrupt time,
we store both LR and the second stack frame's LR save area.

Once we get past the second stack frame, there is no ambiguity; all
return addresses we get are reliable.

For kernel traces, we check whether they are valid kernel instruction
addresses and store zero instead if they are not (rather than
omitting them, which would make it impossible for userspace to know
which was which).  We also store zero instead of the second stack
frame's LR save area value if it is the same as LR.

For kernel traces, we check for interrupt frames, and for user traces,
we check for signal frames.  In each case, since we're starting a new
trace, we store a PERF_CONTEXT_KERNEL/USER marker so that userspace
knows that the next three entries are NIP, LR and the second stack frame
for the interrupted context.

We read user memory with __get_user_inatomic.  On 64-bit, if this
PMU interrupt occurred while interrupts are soft-disabled, and
there is no MMU hash table entry for the page, we will get an
-EFAULT return from __get_user_inatomic even if there is a valid
Linux PTE for the page, since hash_page isn't reentrant.  Thus we
have code here to read the Linux PTE and access the page via the
kernel linear mapping.  Since 64-bit doesn't use (or need) highmem
there is no need to do kmap_atomic.  On 32-bit, we don't do soft
interrupt disabling, so this complication doesn't occur and there
is no need to fall back to reading the Linux PTE, since hash_page
(or the TLB miss handler) will get called automatically if necessary.

Note that we cannot get PMU interrupts in the interval during
context switch between switch_mm (which switches the user address
space) and switch_to (which actually changes current to the new
process).  On 64-bit this is because interrupts are hard-disabled
in switch_mm and stay hard-disabled until they are soft-enabled
later, after switch_to has returned.  So there is no possibility
of trying to do a user stack trace when the user address space is
not current's address space.
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This adds support for the performance monitor hardware on the
MPC7450 family of processors (7450, 7451, 7455, 7447/7457, 7447A,
7448), used in the later Apple G4 powermacs/powerbooks and other
machines.  These machines have 6 hardware counters with a unique
set of events which can be counted on each counter, with some
events being available on multiple counters.

Raw event codes for these processors are (PMC << 8) + PMCSEL.
If PMC is non-zero then the event is that selected by the given
PMCSEL value for that PMC (hardware counter).  If PMC is zero
then the event selected is one of the low-numbered ones that are
common to several PMCs.  In this case PMCSEL must be <= 22 and
the event is what that PMCSEL value would select on PMC1 (but
it may be placed any other PMC that has the same event for that
PMCSEL value).

For events that count cycles or occurrences that exceed a threshold,
the threshold requested can be specified in the 0x3f000 bits of the
raw event codes.  If the event uses the threshold multiplier bit
and that bit should be set, that is indicated with the 0x40000 bit
of the raw event code.

This fills in some of the generic cache events.  Unfortunately there
are quite a few blank spaces in the table, partly because these
processors tend to count cache hits rather than cache accesses.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linuxppc-dev@ozlabs.org
Cc: benh@kernel.crashing.org
LKML-Reference: <19000.55631.802122.696927@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This enables the perf_counter subsystem on 32-bit powerpc.  Since we
don't have any support for hardware counters on 32-bit powerpc yet,
only software counters can be used.

Besides selecting HAVE_PERF_COUNTERS for 32-bit powerpc as well as
64-bit, the main thing this does is add an implementation of
set_perf_counter_pending().  This needs to arrange for
perf_counter_do_pending() to be called when interrupts are enabled.
Rather than add code to local_irq_restore as 64-bit does, the 32-bit
set_perf_counter_pending() generates an interrupt by setting the
decrementer to 1 so that a decrementer interrupt will become pending
in 1 or 2 timebase ticks (if a decrementer interrupt isn't already
pending).  When interrupts are enabled, timer_interrupt() will be
called, and some new code in there calls perf_counter_do_pending().
We use a per-cpu array of flags to indicate whether we need to call
perf_counter_do_pending() or not.

This introduces a couple of new Kconfig symbols: PPC_HAVE_PMU_SUPPORT,
which is selected by processor families for which we have hardware PMU
support (currently only PPC64), and PPC_PERF_CTRS, which enables the
powerpc-specific perf_counter back-end.
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linuxppc-dev@ozlabs.org
Cc: benh@kernel.crashing.org
LKML-Reference: <19000.55404.103840.393470@cargo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Add the option to build the code under arch/powerpc with -Werror.

The intention is to make it harder for people to inadvertantly introduce
warnings in the arch/powerpc code. It needs to be configurable so that
if a warning is introduced, people can easily work around it while it's
being fixed.

The option is a negative, ie. don't enable -Werror, so that it will be
turned on for allyes and allmodconfig builds.

The default is n, in the hope that developers will build with -Werror,
that will probably lead to some build breaks, I am prepared to be flamed.

It's not enabled for math-emu, which is a steaming pile of warnings.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Commit 28794d34 ("powerpc/kconfig: Kill PPC_MULTIPLATFORM"), added
CONFIG_PPC_OF_BOOT_TRAMPOLINE to control the buliding of prom_init.o

However the Makefile still unconditionally builds prom_init_check,
the script that checks prom_init.o for symbol usage, and so in turn
prom_init.o is still always being built. (it's not linked though)

So surround all the prom_init_check logic with an ifeq block testing
if CONFIG_PPC_OF_BOOT_TRAMPOLINE is set.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This adds the back-end for the PMU on POWER7 processors.  POWER7
has 4 fully-programmable counters and two fixed-function counters
(which do respect the freeze conditions, can generate interrupts,
and are writable, unlike PMC5/6 on POWER5+/6).
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <18992.36329.189378.17992@drongo.ozlabs.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This patch includes the basic infrastructure to use swiotlb
bounce buffering on 32-bit powerpc.  It is not yet enabled on
any platforms.  Probably the most interesting bit is the
addition of addr_needs_map to dma_ops - we need this as
a dma_op because the decision of whether or not an addr
can be mapped by a device is device-specific.
Signed-off-by: NBecky Bruce <beckyb@kernel.crashing.org>
Acked-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Currently, load_up_altivec and give_up_altivec are duplicated
in 32-bit and 64-bit. This creates a common implementation that
is moved away from head_32.S, head_64.S and misc_64.S and into
vector.S, using the same macros we already use for our common
implementation of load_up_fpu.

I also moved the VSX code over to vector.S though in that case
I didn't make it build on 32-bit (yet).
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

CONFIG_PPC_MULTIPLATFORM is a remain of the pre-powerpc days and isn't
really meaningful anymore. It was basically equivalent to PPC64 || 6xx.

This removes it along with the following changes:

 - 32-bit platforms that relied on PPC32 && PPC_MULTIPLATFORM now rely
   on 6xx which is what they want anyway.

 - A new symbol, PPC_BOOK3S, is defined that represent compliance with
   the "Server" variant of the architecture. This is set when either 6xx
   or PPC64 is set and open the door for future BOOK3E 64-bit.

 - 64-bit platforms that relied on PPC64 && PPC_MULTIPLATFORM now use
   PPC64 && PPC_BOOK3S

 - A separate and selectable CONFIG_PPC_OF_BOOT_TRAMPOLINE option is now
   used to control the use of prom_init.c
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Impact: more hardware support

This adds the back-end for the PMU on the POWER4 and POWER4+ processors
(GP and GQ).  This is quite similar to the PPC970, with 8 PMCs, but has
fewer events than the PPC970.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Impact: more hardware support

This adds the back-end for the PMU on the POWER5+ processors (i.e. GS,
including GS DD3 aka POWER5++).  This doesn't use the fixed-function
PMC5 and PMC6 since they don't respect the freeze conditions and don't
generate interrupts, as on POWER6.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This adds the back-end for the PMU on the POWER5 processor.  This knows
how to use the fixed-function PMC5 and PMC6 (instructions completed and
run cycles).  Unlike POWER6, PMC5/6 obey the freeze conditions and can
generate interrupts, so their use doesn't impose any extra restrictions.

POWER5+ is different and is not supported by this patch.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

The e500mc supports the new msgsnd/doorbell mechanisms that were added in
the Power ISA 2.05 architecture.  We use the normal level doorbell for
doing SMP IPIs at this point.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This is a port of the function graph tracer that was written by
Frederic Weisbecker for the x86.

This only works for PPC64 at the moment and only for static tracing.
PPC32 and dynamic function graph tracing support will come later.

The trace produces a visual calling of functions:

 # tracer: function_graph
 #
 # CPU  DURATION                  FUNCTION CALLS
 # |     |   |                     |   |   |   |
  0)   2.224 us    |                        }
  0) ! 271.024 us  |                      }
  0) ! 320.080 us  |                    }
  0) ! 324.656 us  |                  }
  0) ! 329.136 us  |                }
  0)               |                .put_prev_task_fair() {
  0)               |                  .update_curr() {
  0)   2.240 us    |                    .update_min_vruntime();
  0)   6.512 us    |                  }
  0)   2.528 us    |                  .__enqueue_entity();
  0) + 15.536 us   |                }
  0)               |                .pick_next_task_fair() {
  0)   2.032 us    |                  .__pick_next_entity();
  0)   2.064 us    |                  .__clear_buddies();
  0)               |                  .set_next_entity() {
  0)   2.672 us    |                    .__dequeue_entity();
  0)   6.864 us    |                  }

Geoff Lavand tested on PS3.
Tested-by: NGeoff Levand <geoffrey.levand@am.sony.com>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

We currently have a few variants of fsl-booke processors (e500v1, e500v2,
e500mc, and e200).  They all have minor differences that we had previously
been handling via ifdefs.

To move towards having this support the following changes have been made:

* PID1, PID2 only exist on e500v1 & e500v2 and should not be accessed on
  e500mc or e200.  We use MMUCFG[NPIDS] to determine which case we are
  since we only touch PID1/2 in extremely early init code.

* Not all IVORs exist on all the processors so introduce cpu_setup
  functions for each variant to setup the proper IVORs that are either
  unique or exist but have some variations between the processors
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

This adds the back-end for the PMU on the POWER6 processor.
Fortunately, the event selection hardware is somewhat simpler on
POWER6 than on other POWER family processors, so the constraints
fit into only 32 bits.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This adds the back-end for the PMU on the PPC970 family.

The PPC970 allows events from the ISU to be selected in two different
ways.  Rather than use alternative event codes to express this, we
instead use a single encoding for ISU events and express the
resulting constraint (that you can't select events from all three
of FPU/IFU/VPU, ISU and IDU/STS at the same time, since they all come
in through only 2 multiplexers) using a NAND constraint field, and
work out which multiplexer is used for ISU events at compute_mmcr
time.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This provides the architecture-specific functions needed to access
PMU hardware on the 64-bit PowerPC processors.  It has been designed
for the IBM POWER family (POWER 4/4+/5/5+/6 and PPC970) but will
hopefully also suit other 64-bit PowerPC machines (although probably
not Cell given how different it is in this area).  This doesn't
include back-ends for any specific processors.

This implements a system which allows back-ends to express the
constraints that their hardware has on what events can be counted
simultaneously.  The constraints are expressed as a 64-bit mask +
64-bit value for each event, and the encoding is capable of
expressing the constraints arising from having a set of multiplexers
feeding an event bus, with some events being available through
multiple multiplexer settings, such as we get on POWER4 and PPC970.
Furthermore, the back-end can supply alternative event codes for
each event, and the constraint checking code will try all possible
combinations of alternative event codes to try to find a combination
that will fit.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

The current code for providing processor cache information in sysfs
has the following deficiencies:
- several complex functions that are hard to understand
- implicit recursion (cache_desc_release -> kobject_put -> cache_desc_release)
- explicit recursion (create_cache_index_info)
- use of two per-cpu arrays when one would suffice
- duplication of work on systems where CPUs share cache

Also, when I looked at implementing support for a shared_cpu_map
attribute, it was pretty much impossible to handle hotplug without
checking every single online CPU's cache_desc list and fixing things
up... not that this is a hot path, but it would have introduced
O(n^2)-ish behavior during boot.  Addressing this involved rethinking
the core data structures used, which didn't lend itself to an
incremental approach.

This implementation maintains a "forest" (potentially more than one
tree) of cache objects which reflects the system's cache topology.
Cache objects are instantiated as needed as CPUs come online.  A
per-cpu array is used mainly for sysfs-related bookkeeping; the
objects in the array just point to the appropriate points in the
forest.

This maintains compatibility with the existing code and includes some
enhancements:
- Implement the shared_cpu_map attribute, which is essential for
  enabling userspace to discover the system's overall cache topology.
- Use cache-block-size properties if cache-line-size is not available.

I chose to place this implementation in a new file since it would have
roughly doubled the size of sysfs.c, which is already kind of messy.
Signed-off-by: NNathan Lynch <ntl@pobox.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This replaces the dummy crash_setup_regs function with full-fledged
crash_setup_regs implementation.  On PPC32 we simply use the new
ppc_save_regs function to dump the registers.
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Today the arch/powerpc/xmon/setjmp.S file contains only the
xmon_save_regs function.  We want to use it for kdump purposes, so
let's move the file into arch/powerpc/kernel/ and give the function a
more generic name (ppc_save_regs).
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Impact: fix for PowerPC 32 code

There were some early init code that was not safe for static
ftrace to boot on my PowerBook. This code must only use relative
addressing, and static mcount performs a compare of the
ftrace_trace_function pointer, and gets that with an absolute address.
In the early init boot up code, this will cause a fault.

This patch removes tracing from the files containing the offending
functions.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Due to confusion between the ftrace infrastructure and the gcc profiling
tracer "ftrace", this patch renames the config options from FTRACE to
FUNCTION_TRACER.  The other two names that are offspring from FTRACE
DYNAMIC_FTRACE and FTRACE_MCOUNT_RECORD will stay the same.

This patch was generated mostly by script, and partially by hand.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

We essentially adopt the 64-bit dma code, with some changes to support
32-bit systems, including HIGHMEM.  dma functions on 32-bit are now
invoked via accessor functions which call the correct op for a device based
on archdata dma_ops.  If there is no archdata dma_ops, this defaults
to dma_direct_ops.

In addition, the dma_map/unmap_page functions are added to dma_ops
because we can't just fall back on map/unmap_single when HIGHMEM is
enabled. In the case of dma_direct_*, we stop using map/unmap_single
and just use the page version - this saves a lot of ugly
ifdeffing.  We leave map/unmap_single in the dma_ops definition,
though, because they are needed by the iommu code, which does not
implement map/unmap_page.  Ideally, going forward, we will completely
eliminate map/unmap_single and just have map/unmap_page, if it's
workable for 64-bit.
Signed-off-by: NBecky Bruce <becky.bruce@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

32-bit platforms are about to start using dma.c; move the iommu
dma ops into their own file to make this a bit cleaner.
Signed-off-by: NBecky Bruce <becky.bruce@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

This is in preparation for the merge of the 32 and 64-bit
dma code in arch/powerpc.
Signed-off-by: NBecky Bruce <becky.bruce@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

This implements CONFIG_RELOCATABLE for 64-bit by making the kernel as
a position-independent executable (PIE) when it is set.  This involves
processing the dynamic relocations in the image in the early stages of
booting, even if the kernel is being run at the address it is linked at,
since the linker does not necessarily fill in words in the image for
which there are dynamic relocations.  (In fact the linker does fill in
such words for 64-bit executables, though not for 32-bit executables,
so in principle we could avoid calling relocate() entirely when we're
running a 64-bit kernel at the linked address.)

The dynamic relocations are processed by a new function relocate(addr),
where the addr parameter is the virtual address where the image will be
run.  In fact we call it twice; once before calling prom_init, and again
when starting the main kernel.  This means that reloc_offset() returns
0 in prom_init (since it has been relocated to the address it is running
at), which necessitated a few adjustments.

This also changes __va and __pa to use an equivalent definition that is
simpler.  With the relocatable kernel, PAGE_OFFSET and MEMORY_START are
constants (for 64-bit) whereas PHYSICAL_START is a variable (and
KERNELBASE ideally should be too, but isn't yet).

With this, relocatable kernels still copy themselves down to physical
address 0 and run there.
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This bug is causing random crashes
(http://bugzilla.kernel.org/show_bug.cgi?id=11414).

-fno-omit-frame-pointer is only needed on powerpc when -pg is also
supplied, and there is a gcc bug that causes incorrect code generation
on 32-bit powerpc when -fno-omit-frame-pointer is used---it uses stack
locations below the stack pointer, which is not allowed by the ABI
because those locations can and sometimes do get corrupted by an
interrupt.

This ensures that CONFIG_FRAME_POINTER is only selected by ftrace.
When CONFIG_FTRACE is enabled we also pass -mno-sched-epilog to work
around the gcc codegen bug.

Patch based on work by:
	Andreas Schwab <schwab@suse.de>
	Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: NTony Breeds <tony@bakeyournoodle.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

The file arch/powerpc/kernel/sysfs.c is currently only compiled for
64-bit kernels.  It contain code to register CPU sysdevs in sysfs and
add various properties such as cache topology and raw access by root
to performance monitor counters (PMCs).  A lot of that can be re-used
as is on 32-bits.

This makes the file be built for both, with appropriate ifdef'ing
for the few bits that are really 64-bit specific, and adds some
support for the raw PMCs for 75x and 74xx processors.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Now that arch/ppc is gone and CONFIG_PPC_MERGE is always set, remove
the dead code associated with !CONFIG_PPC_MERGE from arch/powerpc
and include/asm-powerpc.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This patch removes the old kgdb reminants from ARCH=powerpc and
implements the new style arch specific stub for the common kgdb core
interface.

It is possible to have xmon and kgdb in the same kernel, but you
cannot use both at the same time because there is only one set of
debug hooks.

The arch specific kgdb implementation saves the previous state of the
debug hooks and restores them if you unconfigure the kgdb I/O driver.
Kgdb should have no impact on a kernel that has no kgdb I/O driver
configured.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

Refactor common code between ppc32 and ppc64 module handling into a
shared filed.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

The e500 core enter DOZE/NAP power-saving modes when the core go to
cpu_idle routine.

The power management default running mode is DOZE, If the user

echo 1 > /proc/sys/kernel/powersave-nap

the system will change to NAP running mode.
Signed-off-by: NDave Liu <daveliu@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

This patch adds full support for ftrace for PowerPC (both 64 and 32 bit).
This includes dynamic tracing and function filtering.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/ppc doesn't have prom_init.o (anymore).
Signed-off-by: NSegher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This initializes the RapidIO controller driver using addresses and
interrupt numbers obtained from the firmware device tree, rather than
using hardcoded constants.
Signed-off-by: NZhang Wei <wei.zhang@freescale.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

As BenH said the other day, it is an "accident" that prom_init.o is
linked with the rest of the kernel.  The truth is a little more
subtle, prom_init isn't truly bootloader, it does access kernel data
in a few places.

What we can do is discourage people from adding new code that accesses
data outside of prom_init.  And hence this patch; from the script:

 # This script checks prom_init.o to see what external symbols it
 # is using, if it finds symbols not in the whitelist it returns
 # an error. The point of this is to discourage people from
 # intentionally or accidentally adding new code to prom_init.c
 # which has side effects on other parts of the kernel.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

This adds stacktrace support for powerpc, which will be needed for
lockdep.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility.  Thanks to Peter Zijlstra for fixing the lockdep
warning.  Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.
Signed-off-by: NMatthew Wilcox <willy@linux.intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>

vmlinux.lds and dtc-parser.tab.h get created but never cleaned up.
Signed-off-by: NPaul Mackerras <paulus@samba.org>