In __sanitizer_cov_trace_pc(), previously we write pc before updating pos.
However, some early interrupt code could bypass check_kcov_mode() check
and invoke __sanitizer_cov_trace_pc(). If such interrupt is raised
between writing pc and updating pos, the pc could be overitten by the
recursive __sanitizer_cov_trace_pc().
As suggested by Dmitry, we cold update pos before writing pc to avoid such
interleaving.
Apply the same change to write_comp_data().
Link: https://lkml.kernel.org/r/20220523053531.1572793-1-liu3101@purdue.edu
Signed-off-by: Congyu Liu <liu3101@purdue.edu>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
vm_insert_page()'s failure is not an unexpected condition, so don't do
WARN_ONCE() in such a case.
Instead, print a kernel message and just return an error code.
This flaw has been reported under an OOM condition by sysbot [1].
The message is mainly for the benefit of the test log, in this case the
fuzzer's log so that humans inspecting the log can figure out what was
going on. KCOV is a testing tool, so I think being a little more chatty
when KCOV unexpectedly is about to fail will save someone debugging
time.
We don't want the WARN, because it's not a kernel bug that syzbot should
report, and failure can happen if the fuzzer tries hard enough (as
above).
Link: https://lkml.kernel.org/r/Ylkr2xrVbhQYwNLf@elver.google.com [1]
Link: https://lkml.kernel.org/r/20220401182512.249282-1-nogikh@google.com
Fixes: b3d7fe86fb ("kcov: properly handle subsequent mmap calls"),
Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Taras Madan <tarasmadan@google.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "kcov: improve mmap processing", v3.
Subsequent mmaps of the same kcov descriptor currently do not update the
virtual memory of the task and yet return 0 (success). This is
counter-intuitive and may lead to unexpected memory access errors.
Also, this unnecessarily limits the functionality of kcov to only the
simplest usage scenarios. Kcov instances are effectively forever attached
to their first address spaces and it becomes impossible to e.g. reuse the
same kcov handle in forked child processes without mmapping the memory
first. This is exactly what we tried to do in syzkaller and inadvertently
came upon this behavior.
This patch series addresses the problem described above.
This patch (of 3):
Currently all ioctls are de facto processed under a spinlock in order to
serialise them. This, however, prohibits the use of vmalloc and other
memory management functions in the implementations of those ioctls,
unnecessary complicating any further changes to the code.
Let all ioctls first be processed inside the kcov_ioctl() function which
should execute the ones that are not compatible with spinlock and then
pass control to kcov_ioctl_locked() for all other ones.
KCOV_REMOTE_ENABLE is processed both in kcov_ioctl() and
kcov_ioctl_locked() as the steps are easily separable.
Although it is still compatible with a spinlock, move KCOV_INIT_TRACE
handling to kcov_ioctl(), so that the changes from the next commit are
easier to follow.
Link: https://lkml.kernel.org/r/20220117153634.150357-1-nogikh@google.com
Link: https://lkml.kernel.org/r/20220117153634.150357-2-nogikh@google.com
Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Taras Madan <tarasmadan@google.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The kcov code mixes local_irq_save() and spin_lock() in
kcov_remote_{start|end}(). This creates a warning on PREEMPT_RT because
local_irq_save() disables interrupts and spin_lock_t is turned into a
sleeping lock which can not be acquired in a section with disabled
interrupts.
The kcov_remote_lock is used to synchronize the access to the hash-list
kcov_remote_map. The local_irq_save() block protects access to the
per-CPU data kcov_percpu_data.
There is no compelling reason to change the lock type to raw_spin_lock_t
to make it work with local_irq_save(). Changing it would require to
move memory allocation (in kcov_remote_add()) and deallocation outside
of the locked section.
Adding an unlimited amount of entries to the hashlist will increase the
IRQ-off time during lookup. It could be argued that this is debug code
and the latency does not matter. There is however no need to do so and
it would allow to use this facility in an RT enabled build.
Using a local_lock_t instead of local_irq_save() has the befit of adding
a protection scope within the source which makes it obvious what is
protected. On a !PREEMPT_RT && !LOCKDEP build the local_lock_irqsave()
maps directly to local_irq_save() so there is overhead at runtime.
Replace the local_irq_save() section with a local_lock_t.
Link: https://lkml.kernel.org/r/20210923164741.1859522-6-bigeasy@linutronix.de
Link: https://lore.kernel.org/r/20210830172627.267989-6-bigeasy@linutronix.de
Reported-by: Clark Williams <williams@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Marco Elver <elver@google.com>
Tested-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kcov_common_handle is a method that is used to obtain a "default" KCOV
remote handle of the current process. The handle can later be passed
to kcov_remote_start in order to collect coverage for the processing
that is initiated by one process, but done in another. For details see
Documentation/dev-tools/kcov.rst and comments in kernel/kcov.c.
Presently, if kcov_common_handle is called in an IRQ context, it will
return a handle for the interrupted process. This may lead to
unreliable and incorrect coverage collection.
Adjust the behavior of kcov_common_handle in the following way. If it
is called in a task context, return the common handle for the
currently running task. Otherwise, return 0.
Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
kcov_remote_stop() should check that the corresponding kcov_remote_start()
actually found the specified remote handle and started collecting
coverage. This is done by checking the per thread kcov_softirq flag.
A particular failure scenario where this was observed involved a softirq
with a remote coverage collection section coming between check_kcov_mode()
and the access to t->kcov_area in __sanitizer_cov_trace_pc(). In that
softirq kcov_remote_start() bailed out after kcov_remote_find() check, but
the matching kcov_remote_stop() didn't check if kcov_remote_start()
succeeded, and overwrote per thread kcov parameters with invalid (zero)
values.
Fixes: 5ff3b30ab5 ("kcov: collect coverage from interrupts")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Link: http://lkml.kernel.org/r/fcd1cd16eac1d2c01a66befd8ea4afc6f8d09833.1591576806.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This change extends kcov remote coverage support to allow collecting
coverage from soft interrupts in addition to kernel background threads.
To collect coverage from code that is executed in softirq context, a part
of that code has to be annotated with kcov_remote_start/stop() in a
similar way as how it is done for global kernel background threads. Then
the handle used for the annotations has to be passed to the
KCOV_REMOTE_ENABLE ioctl.
Internally this patch adjusts the __sanitizer_cov_trace_pc() compiler
inserted callback to not bail out when called from softirq context.
kcov_remote_start/stop() are updated to save/restore the current per task
kcov state in a per-cpu area (in case the softirq came when the kernel was
already collecting coverage in task context). Coverage from softirqs is
collected into pre-allocated per-cpu areas, whose size is controlled by
the new CONFIG_KCOV_IRQ_AREA_SIZE.
[andreyknvl@google.com: turn current->kcov_softirq into unsigned int to fix objtool warning]
Link: http://lkml.kernel.org/r/841c778aa3849c5cb8c3761f56b87ce653a88671.1585233617.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Marco Elver <elver@google.com>
Link: http://lkml.kernel.org/r/469bd385c431d050bc38a593296eff4baae50666.1584655448.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series " kcov: collect coverage from usb and vhost", v3.
This patchset extends kcov to allow collecting coverage from backgound
kernel threads. This extension requires custom annotations for each of
the places where coverage collection is desired. This patchset
implements this for hub events in the USB subsystem and for vhost
workers. See the first patch description for details about the kcov
extension. The other two patches apply this kcov extension to USB and
vhost.
Examples of other subsystems that might potentially benefit from this
when custom annotations are added (the list is based on
process_one_work() callers for bugs recently reported by syzbot):
1. fs: writeback wb_workfn() worker,
2. net: addrconf_dad_work()/addrconf_verify_work() workers,
3. net: neigh_periodic_work() worker,
4. net/p9: p9_write_work()/p9_read_work() workers,
5. block: blk_mq_run_work_fn() worker.
These patches have been used to enable coverage-guided USB fuzzing with
syzkaller for the last few years, see the details here:
https://github.com/google/syzkaller/blob/master/docs/linux/external_fuzzing_usb.md
This patchset has been pushed to the public Linux kernel Gerrit
instance:
https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/1524
This patch (of 3):
Add background thread coverage collection ability to kcov.
With KCOV_ENABLE coverage is collected only for syscalls that are issued
from the current process. With KCOV_REMOTE_ENABLE it's possible to
collect coverage for arbitrary parts of the kernel code, provided that
those parts are annotated with kcov_remote_start()/kcov_remote_stop().
This allows to collect coverage from two types of kernel background
threads: the global ones, that are spawned during kernel boot in a
limited number of instances (e.g. one USB hub_event() worker thread is
spawned per USB HCD); and the local ones, that are spawned when a user
interacts with some kernel interface (e.g. vhost workers).
To enable collecting coverage from a global background thread, a unique
global handle must be assigned and passed to the corresponding
kcov_remote_start() call. Then a userspace process can pass a list of
such handles to the KCOV_REMOTE_ENABLE ioctl in the handles array field
of the kcov_remote_arg struct. This will attach the used kcov device to
the code sections, that are referenced by those handles.
Since there might be many local background threads spawned from
different userspace processes, we can't use a single global handle per
annotation. Instead, the userspace process passes a non-zero handle
through the common_handle field of the kcov_remote_arg struct. This
common handle gets saved to the kcov_handle field in the current
task_struct and needs to be passed to the newly spawned threads via
custom annotations. Those threads should in turn be annotated with
kcov_remote_start()/kcov_remote_stop().
Internally kcov stores handles as u64 integers. The top byte of a
handle is used to denote the id of a subsystem that this handle belongs
to, and the lower 4 bytes are used to denote the id of a thread instance
within that subsystem. A reserved value 0 is used as a subsystem id for
common handles as they don't belong to a particular subsystem. The
bytes 4-7 are currently reserved and must be zero. In the future the
number of bytes used for the subsystem or handle ids might be increased.
When a particular userspace process collects coverage by via a common
handle, kcov will collect coverage for each code section that is
annotated to use the common handle obtained as kcov_handle from the
current task_struct. However non common handles allow to collect
coverage selectively from different subsystems.
Link: http://lkml.kernel.org/r/e90e315426a384207edbec1d6aa89e43008e4caf.1572366574.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: David Windsor <dwindsor@gmail.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
atomic_t variables are currently used to implement reference
counters with the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided refcount_t
type and API that prevents accidental counter overflows and underflows.
This is important since overflows and underflows can lead to
use-after-free situation and be exploitable.
The variable kcov.refcount is used as pure reference counter. Convert
it to refcount_t and fix up the operations.
**Important note for maintainers:
Some functions from refcount_t API defined in lib/refcount.c have
different memory ordering guarantees than their atomic counterparts.
The full comparison can be seen in https://lkml.org/lkml/2017/11/15/57
and it is hopefully soon in state to be merged to the documentation
tree. Normally the differences should not matter since refcount_t
provides enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter. Please double check that you don't
have some undocumented memory guarantees for this variable usage.
For the kcov.refcount it might make a difference
in following places:
- kcov_put(): decrement in refcount_dec_and_test() only
provides RELEASE ordering and control dependency on success
vs. fully ordered atomic counterpart
Link: http://lkml.kernel.org/r/1547634429-772-1-git-send-email-elena.reshetova@intel.com
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since __sanitizer_cov_trace_const_cmp4 is marked as notrace, the
function called from __sanitizer_cov_trace_const_cmp4 shouldn't be
traceable either. ftrace_graph_caller() gets called every time func
write_comp_data() gets called if it isn't marked 'notrace'. This is the
backtrace from gdb:
#0 ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
#1 0xffffff8010201920 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:151
#2 0xffffff8010439714 in write_comp_data (type=5, arg1=0, arg2=0, ip=18446743524224276596) at ../kernel/kcov.c:116
#3 0xffffff8010439894 in __sanitizer_cov_trace_const_cmp4 (arg1=<optimized out>, arg2=<optimized out>) at ../kernel/kcov.c:188
#4 0xffffff8010201874 in prepare_ftrace_return (self_addr=18446743524226602768, parent=0xffffff801014b918, frame_pointer=18446743524223531344) at ./include/generated/atomic-instrumented.h:27
#5 0xffffff801020194c in ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:182
Rework so that write_comp_data() that are called from
__sanitizer_cov_trace_*_cmp*() are marked as 'notrace'.
Commit 903e8ff867 ("kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace")
missed to mark write_comp_data() as 'notrace'. When that patch was
created gcc-7 was used. In lib/Kconfig.debug
config KCOV_ENABLE_COMPARISONS
depends on $(cc-option,-fsanitize-coverage=trace-cmp)
That code path isn't hit with gcc-7. However, it were that with gcc-8.
Link: http://lkml.kernel.org/r/20181206143011.23719-1-anders.roxell@linaro.org
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since __sanitizer_cov_trace_pc() is marked as notrace, function calls in
__sanitizer_cov_trace_pc() shouldn't be traced either.
ftrace_graph_caller() gets called for each function that isn't marked
'notrace', like canonicalize_ip(). This is the call trace from a run:
[ 139.644550] ftrace_graph_caller+0x1c/0x24
[ 139.648352] canonicalize_ip+0x18/0x28
[ 139.652313] __sanitizer_cov_trace_pc+0x14/0x58
[ 139.656184] sched_clock+0x34/0x1e8
[ 139.659759] trace_clock_local+0x40/0x88
[ 139.663722] ftrace_push_return_trace+0x8c/0x1f0
[ 139.667767] prepare_ftrace_return+0xa8/0x100
[ 139.671709] ftrace_graph_caller+0x1c/0x24
Rework so that check_kcov_mode() and canonicalize_ip() that are called
from __sanitizer_cov_trace_pc() are also marked as notrace.
Link: http://lkml.kernel.org/r/20181128081239.18317-1-anders.roxell@linaro.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signen-off-by: Anders Roxell <anders.roxell@linaro.org>
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
During a context switch, we first switch_mm() to the next task's mm,
then switch_to() that new task. This means that vmalloc'd regions which
had previously been faulted in can transiently disappear in the context
of the prev task.
Functions instrumented by KCOV may try to access a vmalloc'd kcov_area
during this window, and as the fault handling code is instrumented, this
results in a recursive fault.
We must avoid accessing any kcov_area during this window. We can do so
with a new flag in kcov_mode, set prior to switching the mm, and cleared
once the new task is live. Since task_struct::kcov_mode isn't always a
specific enum kcov_mode value, this is made an unsigned int.
The manipulation is hidden behind kcov_{prepare,finish}_switch() helpers,
which are empty for !CONFIG_KCOV kernels.
The code uses macros because I can't use static inline functions without a
circular include dependency between <linux/sched.h> and <linux/kcov.h>,
since the definition of task_struct uses things defined in <linux/kcov.h>
Link: http://lkml.kernel.org/r/20180504135535.53744-4-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On many architectures the vmalloc area is lazily faulted in upon first
access. This is problematic for KCOV, as __sanitizer_cov_trace_pc
accesses the (vmalloc'd) kcov_area, and fault handling code may be
instrumented. If an access to kcov_area faults, this will result in
mutual recursion through the fault handling code and
__sanitizer_cov_trace_pc(), eventually leading to stack corruption
and/or overflow.
We can avoid this by faulting in the kcov_area before
__sanitizer_cov_trace_pc() is permitted to access it. Once it has been
faulted in, it will remain present in the process page tables, and will
not fault again.
[akpm@linux-foundation.org: code cleanup]
[akpm@linux-foundation.org: add comment explaining kcov_fault_in_area()]
[akpm@linux-foundation.org: fancier code comment from Mark]
Link: http://lkml.kernel.org/r/20180504135535.53744-3-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "kcov: fix unexpected faults".
These patches fix a few issues where KCOV code could trigger recursive
faults, discovered while debugging a patch enabling KCOV for arch/arm:
* On CONFIG_PREEMPT kernels, there's a small race window where
__sanitizer_cov_trace_pc() can see a bogus kcov_area.
* Lazy faulting of the vmalloc area can cause mutual recursion between
fault handling code and __sanitizer_cov_trace_pc().
* During the context switch, switching the mm can cause the kcov_area to
be transiently unmapped.
These are prerequisites for enabling KCOV on arm, but the issues
themsevles are generic -- we just happen to avoid them by chance rather
than design on x86-64 and arm64.
This patch (of 3):
For kernels built with CONFIG_PREEMPT, some C code may execute before or
after the interrupt handler, while the hardirq count is zero. In these
cases, in_task() can return true.
A task can be interrupted in the middle of a KCOV_DISABLE ioctl while it
resets the task's kcov data via kcov_task_init(). Instrumented code
executed during this period will call __sanitizer_cov_trace_pc(), and as
in_task() returns true, will inspect t->kcov_mode before trying to write
to t->kcov_area.
In kcov_init_task() we update t->kcov_{mode,area,size} with plain stores,
which may be re-ordered, torn, etc. Thus __sanitizer_cov_trace_pc() may
see bogus values for any of these fields, and may attempt to write to
memory which is not mapped.
Let's avoid this by using WRITE_ONCE() to set t->kcov_mode, with a
barrier() to ensure this is ordered before we clear t->kov_{area,size}.
This ensures that any code execute while kcov_init_task() is preempted
will either see valid values for t->kcov_{area,size}, or will see that
t->kcov_mode is KCOV_MODE_DISABLED, and bail out without touching
t->kcov_area.
Link: http://lkml.kernel.org/r/20180504135535.53744-2-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
