adios utrace.

1 files changed, 0 insertions, 4166 deletions

diff --git a/linux-2.6-utrace.patch b/linux-2.6-utrace.patch
deleted file mode 100644
index 366b8a176..000000000
--- a/linux-2.6-utrace.patch
+++ /dev/null
@@ -1,4166 +0,0 @@
-utrace core
-
-This adds the utrace facility, a new modular interface in the kernel for
-implementing user thread tracing and debugging.  This fits on top of the
-tracehook_* layer, so the new code is well-isolated.
-
-The new interface is in <linux/utrace.h> and the DocBook utrace book
-describes it.  It allows for multiple separate tracing engines to work in
-parallel without interfering with each other.  Higher-level tracing
-facilities can be implemented as loadable kernel modules using this layer.
-
-The new facility is made optional under CONFIG_UTRACE.
-When this is not enabled, no new code is added.
-It can only be enabled on machines that have all the
-prerequisites and select CONFIG_HAVE_ARCH_TRACEHOOK.
-
-In this initial version, utrace and ptrace do not play together at all.
-If ptrace is attached to a thread, the attach calls in the utrace kernel
-API return -EBUSY.  If utrace is attached to a thread, the PTRACE_ATTACH
-or PTRACE_TRACEME request will return EBUSY to userland.  The old ptrace
-code is otherwise unchanged and nothing using ptrace should be affected
-by this patch as long as utrace is not used at the same time.  In the
-future we can clean up the ptrace implementation and rework it to use
-the utrace API.
-
-Signed-off-by: Roland McGrath <roland@redhat.com>
----
- Documentation/DocBook/Makefile    |    2 +-
- Documentation/DocBook/utrace.tmpl |  589 +++++++++
- fs/proc/array.c                   |    3 +
- include/linux/sched.h             |    5 +
- include/linux/tracehook.h         |   87 ++-
- include/linux/utrace.h            |  692 +++++++++++
- init/Kconfig                      |    9 +
- kernel/Makefile                   |    1 +
- kernel/fork.c                     |    3 +
- kernel/ptrace.c                   |   14 +
- kernel/utrace.c                   | 2440 +++++++++++++++++++++++++++++++++++++
- 11 files changed, 3843 insertions(+), 2 deletions(-)
-
-diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile
-index 8b6e00a..2740633 100644  
---- a/Documentation/DocBook/Makefile
-+++ b/Documentation/DocBook/Makefile
-@@ -14,7 +14,7 @@ DOCBOOKS := z8530book.xml mcabook.xml de
- 	    genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \
- 	    80211.xml debugobjects.xml sh.xml regulator.xml \
- 	    alsa-driver-api.xml writing-an-alsa-driver.xml \
--	    tracepoint.xml media.xml drm.xml
-+	    tracepoint.xml utrace.xml media.xml drm.xml
- 
- ###
- # The build process is as follows (targets):
-diff --git a/Documentation/DocBook/utrace.tmpl b/Documentation/DocBook/utrace.tmpl
-new file mode 100644
-index ...0c40add 100644  
---- /dev/null
-+++ b/Documentation/DocBook/utrace.tmpl
-@@ -0,0 +1,589 @@
-+<?xml version="1.0" encoding="UTF-8"?>
-+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
-+"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-+
-+<book id="utrace">
-+  <bookinfo>
-+    <title>The utrace User Debugging Infrastructure</title>
-+  </bookinfo>
-+
-+  <toc></toc>
-+
-+  <chapter id="concepts"><title>utrace concepts</title>
-+
-+  <sect1 id="intro"><title>Introduction</title>
-+
-+  <para>
-+    <application>utrace</application> is infrastructure code for tracing
-+    and controlling user threads.  This is the foundation for writing
-+    tracing engines, which can be loadable kernel modules.
-+  </para>
-+
-+  <para>
-+    The basic actors in <application>utrace</application> are the thread
-+    and the tracing engine.  A tracing engine is some body of code that
-+    calls into the <filename>&lt;linux/utrace.h&gt;</filename>
-+    interfaces, represented by a <structname>struct
-+    utrace_engine_ops</structname>.  (Usually it's a kernel module,
-+    though the legacy <function>ptrace</function> support is a tracing
-+    engine that is not in a kernel module.)  The interface operates on
-+    individual threads (<structname>struct task_struct</structname>).
-+    If an engine wants to treat several threads as a group, that is up
-+    to its higher-level code.
-+  </para>
-+
-+  <para>
-+    Tracing begins by attaching an engine to a thread, using
-+    <function>utrace_attach_task</function> or
-+    <function>utrace_attach_pid</function>.  If successful, it returns a
-+    pointer that is the handle used in all other calls.
-+  </para>
-+
-+  </sect1>
-+
-+  <sect1 id="callbacks"><title>Events and Callbacks</title>
-+
-+  <para>
-+    An attached engine does nothing by default.  An engine makes something
-+    happen by requesting callbacks via <function>utrace_set_events</function>
-+    and poking the thread with <function>utrace_control</function>.
-+    The synchronization issues related to these two calls
-+    are discussed further below in <xref linkend="teardown"/>.
-+  </para>
-+
-+  <para>
-+    Events are specified using the macro
-+    <constant>UTRACE_EVENT(<replaceable>type</replaceable>)</constant>.
-+    Each event type is associated with a callback in <structname>struct
-+    utrace_engine_ops</structname>.  A tracing engine can leave unused
-+    callbacks <constant>NULL</constant>.  The only callbacks required
-+    are those used by the event flags it sets.
-+  </para>
-+
-+  <para>
-+    Many engines can be attached to each thread.  When a thread has an
-+    event, each engine gets a callback if it has set the event flag for
-+    that event type.  For most events, engines are called in the order they
-+    attached.  Engines that attach after the event has occurred do not get
-+    callbacks for that event.  This includes any new engines just attached
-+    by an existing engine's callback function.  Once the sequence of
-+    callbacks for that one event has completed, such new engines are then
-+    eligible in the next sequence that starts when there is another event.
-+  </para>
-+
-+  <para>
-+    Event reporting callbacks have details particular to the event type,
-+    but are all called in similar environments and have the same
-+    constraints.  Callbacks are made from safe points, where no locks
-+    are held, no special resources are pinned (usually), and the
-+    user-mode state of the thread is accessible.  So, callback code has
-+    a pretty free hand.  But to be a good citizen, callback code should
-+    never block for long periods.  It is fine to block in
-+    <function>kmalloc</function> and the like, but never wait for i/o or
-+    for user mode to do something.  If you need the thread to wait, use
-+    <constant>UTRACE_STOP</constant> and return from the callback
-+    quickly.  When your i/o finishes or whatever, you can use
-+    <function>utrace_control</function> to resume the thread.
-+  </para>
-+
-+  <para>
-+    The <constant>UTRACE_EVENT(SYSCALL_ENTRY)</constant> event is a special
-+    case.  While other events happen in the kernel when it will return to
-+    user mode soon, this event happens when entering the kernel before it
-+    will proceed with the work requested from user mode.  Because of this
-+    difference, the <function>report_syscall_entry</function> callback is
-+    special in two ways.  For this event, engines are called in reverse of
-+    the normal order (this includes the <function>report_quiesce</function>
-+    call that precedes a <function>report_syscall_entry</function> call).
-+    This preserves the semantics that the last engine to attach is called
-+    "closest to user mode"--the engine that is first to see a thread's user
-+    state when it enters the kernel is also the last to see that state when
-+    the thread returns to user mode.  For the same reason, if these
-+    callbacks use <constant>UTRACE_STOP</constant> (see the next section),
-+    the thread stops immediately after callbacks rather than only when it's
-+    ready to return to user mode; when allowed to resume, it will actually
-+    attempt the system call indicated by the register values at that time.
-+  </para>
-+
-+  </sect1>
-+
-+  <sect1 id="safely"><title>Stopping Safely</title>
-+
-+  <sect2 id="well-behaved"><title>Writing well-behaved callbacks</title>
-+
-+  <para>
-+    Well-behaved callbacks are important to maintain two essential
-+    properties of the interface.  The first of these is that unrelated
-+    tracing engines should not interfere with each other.  If your engine's
-+    event callback does not return quickly, then another engine won't get
-+    the event notification in a timely manner.  The second important
-+    property is that tracing should be as noninvasive as possible to the
-+    normal operation of the system overall and of the traced thread in
-+    particular.  That is, attached tracing engines should not perturb a
-+    thread's behavior, except to the extent that changing its user-visible
-+    state is explicitly what you want to do.  (Obviously some perturbation
-+    is unavoidable, primarily timing changes, ranging from small delays due
-+    to the overhead of tracing, to arbitrary pauses in user code execution
-+    when a user stops a thread with a debugger for examination.)  Even when
-+    you explicitly want the perturbation of making the traced thread block,
-+    just blocking directly in your callback has more unwanted effects.  For
-+    example, the <constant>CLONE</constant> event callbacks are called when
-+    the new child thread has been created but not yet started running; the
-+    child can never be scheduled until the <constant>CLONE</constant>
-+    tracing callbacks return.  (This allows engines tracing the parent to
-+    attach to the child.)  If a <constant>CLONE</constant> event callback
-+    blocks the parent thread, it also prevents the child thread from
-+    running (even to process a <constant>SIGKILL</constant>).  If what you
-+    want is to make both the parent and child block, then use
-+    <function>utrace_attach_task</function> on the child and then use
-+    <constant>UTRACE_STOP</constant> on both threads.  A more crucial
-+    problem with blocking in callbacks is that it can prevent
-+    <constant>SIGKILL</constant> from working.  A thread that is blocking
-+    due to <constant>UTRACE_STOP</constant> will still wake up and die
-+    immediately when sent a <constant>SIGKILL</constant>, as all threads
-+    should.  Relying on the <application>utrace</application>
-+    infrastructure rather than on private synchronization calls in event
-+    callbacks is an important way to help keep tracing robustly
-+    noninvasive.
-+  </para>
-+
-+  </sect2>
-+
-+  <sect2 id="UTRACE_STOP"><title>Using <constant>UTRACE_STOP</constant></title>
-+
-+  <para>
-+    To control another thread and access its state, it must be stopped
-+    with <constant>UTRACE_STOP</constant>.  This means that it is
-+    stopped and won't start running again while we access it.  When a
-+    thread is not already stopped, <function>utrace_control</function>
-+    returns <constant>-EINPROGRESS</constant> and an engine must wait
-+    for an event callback when the thread is ready to stop.  The thread
-+    may be running on another CPU or may be blocked.  When it is ready
-+    to be examined, it will make callbacks to engines that set the
-+    <constant>UTRACE_EVENT(QUIESCE)</constant> event bit.  To wake up an
-+    interruptible wait, use <constant>UTRACE_INTERRUPT</constant>.
-+  </para>
-+
-+  <para>
-+    As long as some engine has used <constant>UTRACE_STOP</constant> and
-+    not called <function>utrace_control</function> to resume the thread,
-+    then the thread will remain stopped.  <constant>SIGKILL</constant>
-+    will wake it up, but it will not run user code.  When the stop is
-+    cleared with <function>utrace_control</function> or a callback
-+    return value, the thread starts running again.
-+    (See also <xref linkend="teardown"/>.)
-+  </para>
-+
-+  </sect2>
-+
-+  </sect1>
-+
-+  <sect1 id="teardown"><title>Tear-down Races</title>
-+
-+  <sect2 id="SIGKILL"><title>Primacy of <constant>SIGKILL</constant></title>
-+  <para>
-+    Ordinarily synchronization issues for tracing engines are kept fairly
-+    straightforward by using <constant>UTRACE_STOP</constant>.  You ask a
-+    thread to stop, and then once it makes the
-+    <function>report_quiesce</function> callback it cannot do anything else
-+    that would result in another callback, until you let it with a
-+    <function>utrace_control</function> call.  This simple arrangement
-+    avoids complex and error-prone code in each one of a tracing engine's
-+    event callbacks to keep them serialized with the engine's other
-+    operations done on that thread from another thread of control.
-+    However, giving tracing engines complete power to keep a traced thread
-+    stuck in place runs afoul of a more important kind of simplicity that
-+    the kernel overall guarantees: nothing can prevent or delay
-+    <constant>SIGKILL</constant> from making a thread die and release its
-+    resources.  To preserve this important property of
-+    <constant>SIGKILL</constant>, it as a special case can break
-+    <constant>UTRACE_STOP</constant> like nothing else normally can.  This
-+    includes both explicit <constant>SIGKILL</constant> signals and the
-+    implicit <constant>SIGKILL</constant> sent to each other thread in the
-+    same thread group by a thread doing an exec, or processing a fatal
-+    signal, or making an <function>exit_group</function> system call.  A
-+    tracing engine can prevent a thread from beginning the exit or exec or
-+    dying by signal (other than <constant>SIGKILL</constant>) if it is
-+    attached to that thread, but once the operation begins, no tracing
-+    engine can prevent or delay all other threads in the same thread group
-+    dying.
-+  </para>
-+  </sect2>
-+
-+  <sect2 id="reap"><title>Final callbacks</title>
-+  <para>
-+    The <function>report_reap</function> callback is always the final event
-+    in the life cycle of a traced thread.  Tracing engines can use this as
-+    the trigger to clean up their own data structures.  The
-+    <function>report_death</function> callback is always the penultimate
-+    event a tracing engine might see; it's seen unless the thread was
-+    already in the midst of dying when the engine attached.  Many tracing
-+    engines will have no interest in when a parent reaps a dead process,
-+    and nothing they want to do with a zombie thread once it dies; for
-+    them, the <function>report_death</function> callback is the natural
-+    place to clean up data structures and detach.  To facilitate writing
-+    such engines robustly, given the asynchrony of
-+    <constant>SIGKILL</constant>, and without error-prone manual
-+    implementation of synchronization schemes, the
-+    <application>utrace</application> infrastructure provides some special
-+    guarantees about the <function>report_death</function> and
-+    <function>report_reap</function> callbacks.  It still takes some care
-+    to be sure your tracing engine is robust to tear-down races, but these
-+    rules make it reasonably straightforward and concise to handle a lot of
-+    corner cases correctly.
-+  </para>
-+  </sect2>
-+
-+  <sect2 id="refcount"><title>Engine and task pointers</title>
-+  <para>
-+    The first sort of guarantee concerns the core data structures
-+    themselves.  <structname>struct utrace_engine</structname> is
-+    a reference-counted data structure.  While you hold a reference, an
-+    engine pointer will always stay valid so that you can safely pass it to
-+    any <application>utrace</application> call.  Each call to
-+    <function>utrace_attach_task</function> or
-+    <function>utrace_attach_pid</function> returns an engine pointer with a
-+    reference belonging to the caller.  You own that reference until you
-+    drop it using <function>utrace_engine_put</function>.  There is an
-+    implicit reference on the engine while it is attached.  So if you drop
-+    your only reference, and then use
-+    <function>utrace_attach_task</function> without
-+    <constant>UTRACE_ATTACH_CREATE</constant> to look up that same engine,
-+    you will get the same pointer with a new reference to replace the one
-+    you dropped, just like calling <function>utrace_engine_get</function>.
-+    When an engine has been detached, either explicitly with
-+    <constant>UTRACE_DETACH</constant> or implicitly after
-+    <function>report_reap</function>, then any references you hold are all
-+    that keep the old engine pointer alive.
-+  </para>
-+
-+  <para>
-+    There is nothing a kernel module can do to keep a <structname>struct
-+    task_struct</structname> alive outside of
-+    <function>rcu_read_lock</function>.  When the task dies and is reaped
-+    by its parent (or itself), that structure can be freed so that any
-+    dangling pointers you have stored become invalid.
-+    <application>utrace</application> will not prevent this, but it can
-+    help you detect it safely.  By definition, a task that has been reaped
-+    has had all its engines detached.  All
-+    <application>utrace</application> calls can be safely called on a
-+    detached engine if the caller holds a reference on that engine pointer,
-+    even if the task pointer passed in the call is invalid.  All calls
-+    return <constant>-ESRCH</constant> for a detached engine, which tells
-+    you that the task pointer you passed could be invalid now.  Since
-+    <function>utrace_control</function> and
-+    <function>utrace_set_events</function> do not block, you can call those
-+    inside a <function>rcu_read_lock</function> section and be sure after
-+    they don't return <constant>-ESRCH</constant> that the task pointer is
-+    still valid until <function>rcu_read_unlock</function>.  The
-+    infrastructure never holds task references of its own.  Though neither
-+    <function>rcu_read_lock</function> nor any other lock is held while
-+    making a callback, it's always guaranteed that the <structname>struct
-+    task_struct</structname> and the <structname>struct
-+    utrace_engine</structname> passed as arguments remain valid
-+    until the callback function returns.
-+  </para>
-+
-+  <para>
-+    The common means for safely holding task pointers that is available to
-+    kernel modules is to use <structname>struct pid</structname>, which
-+    permits <function>put_pid</function> from kernel modules.  When using
-+    that, the calls <function>utrace_attach_pid</function>,
-+    <function>utrace_control_pid</function>,
-+    <function>utrace_set_events_pid</function>, and
-+    <function>utrace_barrier_pid</function> are available.
-+  </para>
-+  </sect2>
-+
-+  <sect2 id="reap-after-death">
-+    <title>
-+      Serialization of <constant>DEATH</constant> and <constant>REAP</constant>
-+    </title>
-+    <para>
-+      The second guarantee is the serialization of
-+      <constant>DEATH</constant> and <constant>REAP</constant> event
-+      callbacks for a given thread.  The actual reaping by the parent
-+      (<function>release_task</function> call) can occur simultaneously
-+      while the thread is still doing the final steps of dying, including
-+      the <function>report_death</function> callback.  If a tracing engine
-+      has requested both <constant>DEATH</constant> and
-+      <constant>REAP</constant> event reports, it's guaranteed that the
-+      <function>report_reap</function> callback will not be made until
-+      after the <function>report_death</function> callback has returned.
-+      If the <function>report_death</function> callback itself detaches
-+      from the thread, then the <function>report_reap</function> callback
-+      will never be made.  Thus it is safe for a
-+      <function>report_death</function> callback to clean up data
-+      structures and detach.
-+    </para>
-+  </sect2>
-+
-+  <sect2 id="interlock"><title>Interlock with final callbacks</title>
-+  <para>
-+    The final sort of guarantee is that a tracing engine will know for sure
-+    whether or not the <function>report_death</function> and/or
-+    <function>report_reap</function> callbacks will be made for a certain
-+    thread.  These tear-down races are disambiguated by the error return
-+    values of <function>utrace_set_events</function> and
-+    <function>utrace_control</function>.  Normally
-+    <function>utrace_control</function> called with
-+    <constant>UTRACE_DETACH</constant> returns zero, and this means that no
-+    more callbacks will be made.  If the thread is in the midst of dying,
-+    it returns <constant>-EALREADY</constant> to indicate that the
-+    <constant>report_death</constant> callback may already be in progress;
-+    when you get this error, you know that any cleanup your
-+    <function>report_death</function> callback does is about to happen or
-+    has just happened--note that if the <function>report_death</function>
-+    callback does not detach, the engine remains attached until the thread
-+    gets reaped.  If the thread is in the midst of being reaped,
-+    <function>utrace_control</function> returns <constant>-ESRCH</constant>
-+    to indicate that the <function>report_reap</function> callback may
-+    already be in progress; this means the engine is implicitly detached
-+    when the callback completes.  This makes it possible for a tracing
-+    engine that has decided asynchronously to detach from a thread to
-+    safely clean up its data structures, knowing that no
-+    <function>report_death</function> or <function>report_reap</function>
-+    callback will try to do the same.  <constant>utrace_detach</constant>
-+    returns <constant>-ESRCH</constant> when the <structname>struct
-+    utrace_engine</structname> has already been detached, but is
-+    still a valid pointer because of its reference count.  A tracing engine
-+    can use this to safely synchronize its own independent multiple threads
-+    of control with each other and with its event callbacks that detach.
-+  </para>
-+
-+  <para>
-+    In the same vein, <function>utrace_set_events</function> normally
-+    returns zero; if the target thread was stopped before the call, then
-+    after a successful call, no event callbacks not requested in the new
-+    flags will be made.  It fails with <constant>-EALREADY</constant> if
-+    you try to clear <constant>UTRACE_EVENT(DEATH)</constant> when the
-+    <function>report_death</function> callback may already have begun, or if
-+    you try to newly set <constant>UTRACE_EVENT(DEATH)</constant> or
-+    <constant>UTRACE_EVENT(QUIESCE)</constant> when the target is already
-+    dead or dying.  Like <function>utrace_control</function>, it returns
-+    <constant>-ESRCH</constant> when the <function>report_reap</function>
-+    callback may already have begun, or the thread has already been detached
-+    (including forcible detach on reaping).  This lets the tracing engine
-+    know for sure which event callbacks it will or won't see after
-+    <function>utrace_set_events</function> has returned.  By checking for
-+    errors, it can know whether to clean up its data structures immediately
-+    or to let its callbacks do the work.
-+  </para>
-+  </sect2>
-+
-+  <sect2 id="barrier"><title>Using <function>utrace_barrier</function></title>
-+  <para>
-+    When a thread is safely stopped, calling
-+    <function>utrace_control</function> with <constant>UTRACE_DETACH</constant>
-+    or calling <function>utrace_set_events</function> to disable some events
-+    ensures synchronously that your engine won't get any more of the callbacks
-+    that have been disabled (none at all when detaching).  But these can also
-+    be used while the thread is not stopped, when it might be simultaneously
-+    making a callback to your engine.  For this situation, these calls return
-+    <constant>-EINPROGRESS</constant> when it's possible a callback is in
-+    progress.  If you are not prepared to have your old callbacks still run,
-+    then you can synchronize to be sure all the old callbacks are finished,
-+    using <function>utrace_barrier</function>.  This is necessary if the
-+    kernel module containing your callback code is going to be unloaded.
-+  </para>
-+  <para>
-+    After using <constant>UTRACE_DETACH</constant> once, further calls to
-+    <function>utrace_control</function> with the same engine pointer will
-+    return <constant>-ESRCH</constant>.  In contrast, after getting
-+    <constant>-EINPROGRESS</constant> from
-+    <function>utrace_set_events</function>, you can call
-+    <function>utrace_set_events</function> again later and if it returns zero
-+    then know the old callbacks have finished.
-+  </para>
-+  <para>
-+    Unlike all other calls, <function>utrace_barrier</function> (and
-+    <function>utrace_barrier_pid</function>) will accept any engine pointer you
-+    hold a reference on, even if <constant>UTRACE_DETACH</constant> has already
-+    been used.  After any <function>utrace_control</function> or
-+    <function>utrace_set_events</function> call (these do not block), you can
-+    call <function>utrace_barrier</function> to block until callbacks have
-+    finished.  This returns <constant>-ESRCH</constant> only if the engine is
-+    completely detached (finished all callbacks).  Otherwise it waits
-+    until the thread is definitely not in the midst of a callback to this
-+    engine and then returns zero, but can return
-+    <constant>-ERESTARTSYS</constant> if its wait is interrupted.
-+  </para>
-+  </sect2>
-+
-+</sect1>
-+
-+</chapter>
-+
-+<chapter id="core"><title>utrace core API</title>
-+
-+<para>
-+  The utrace API is declared in <filename>&lt;linux/utrace.h&gt;</filename>.
-+</para>
-+
-+!Iinclude/linux/utrace.h
-+!Ekernel/utrace.c
-+
-+</chapter>
-+
-+<chapter id="machine"><title>Machine State</title>
-+
-+<para>
-+  The <function>task_current_syscall</function> function can be used on any
-+  valid <structname>struct task_struct</structname> at any time, and does
-+  not even require that <function>utrace_attach_task</function> was used at all.
-+</para>
-+
-+<para>
-+  The other ways to access the registers and other machine-dependent state of
-+  a task can only be used on a task that is at a known safe point.  The safe
-+  points are all the places where <function>utrace_set_events</function> can
-+  request callbacks (except for the <constant>DEATH</constant> and
-+  <constant>REAP</constant> events).  So at any event callback, it is safe to
-+  examine <varname>current</varname>.
-+</para>
-+
-+<para>
-+  One task can examine another only after a callback in the target task that
-+  returns <constant>UTRACE_STOP</constant> so that task will not return to user
-+  mode after the safe point.  This guarantees that the task will not resume
-+  until the same engine uses <function>utrace_control</function>, unless the
-+  task dies suddenly.  To examine safely, one must use a pair of calls to
-+  <function>utrace_prepare_examine</function> and
-+  <function>utrace_finish_examine</function> surrounding the calls to
-+  <structname>struct user_regset</structname> functions or direct examination
-+  of task data structures.  <function>utrace_prepare_examine</function> returns
-+  an error if the task is not properly stopped, or is dead.  After a
-+  successful examination, the paired <function>utrace_finish_examine</function>
-+  call returns an error if the task ever woke up during the examination.  If
-+  so, any data gathered may be scrambled and should be discarded.  This means
-+  there was a spurious wake-up (which should not happen), or a sudden death.
-+</para>
-+
-+<sect1 id="regset"><title><structname>struct user_regset</structname></title>
-+
-+<para>
-+  The <structname>struct user_regset</structname> API
-+  is declared in <filename>&lt;linux/regset.h&gt;</filename>.
-+</para>
-+
-+!Finclude/linux/regset.h
-+
-+</sect1>
-+
-+<sect1 id="task_current_syscall">
-+  <title><filename>System Call Information</filename></title>
-+
-+<para>
-+  This function is declared in <filename>&lt;linux/ptrace.h&gt;</filename>.
-+</para>
-+
-+!Elib/syscall.c
-+
-+</sect1>
-+
-+<sect1 id="syscall"><title><filename>System Call Tracing</filename></title>
-+
-+<para>
-+  The arch API for system call information is declared in
-+  <filename>&lt;asm/syscall.h&gt;</filename>.
-+  Each of these calls can be used only at system call entry tracing,
-+  or can be used only at system call exit and the subsequent safe points
-+  before returning to user mode.
-+  At system call entry tracing means either during a
-+  <structfield>report_syscall_entry</structfield> callback,
-+  or any time after that callback has returned <constant>UTRACE_STOP</constant>.
-+</para>
-+
-+!Finclude/asm-generic/syscall.h
-+
-+</sect1>
-+
-+</chapter>
-+
-+<chapter id="internals"><title>Kernel Internals</title>
-+
-+<para>
-+  This chapter covers the interface to the tracing infrastructure
-+  from the core of the kernel and the architecture-specific code.
-+  This is for maintainers of the kernel and arch code, and not relevant
-+  to using the tracing facilities described in preceding chapters.
-+</para>
-+
-+<sect1 id="tracehook"><title>Core Calls In</title>
-+
-+<para>
-+  These calls are declared in <filename>&lt;linux/tracehook.h&gt;</filename>.
-+  The core kernel calls these functions at various important places.
-+</para>
-+
-+!Finclude/linux/tracehook.h
-+
-+</sect1>
-+
-+<sect1 id="arch"><title>Architecture Calls Out</title>
-+
-+<para>
-+  An arch that has done all these things sets
-+  <constant>CONFIG_HAVE_ARCH_TRACEHOOK</constant>.
-+  This is required to enable the <application>utrace</application> code.
-+</para>
-+
-+<sect2 id="arch-ptrace"><title><filename>&lt;asm/ptrace.h&gt;</filename></title>
-+
-+<para>
-+  An arch defines these in <filename>&lt;asm/ptrace.h&gt;</filename>
-+  if it supports hardware single-step or block-step features.
-+</para>
-+
-+!Finclude/linux/ptrace.h arch_has_single_step arch_has_block_step
-+!Finclude/linux/ptrace.h user_enable_single_step user_enable_block_step
-+!Finclude/linux/ptrace.h user_disable_single_step
-+
-+</sect2>
-+
-+<sect2 id="arch-syscall">
-+  <title><filename>&lt;asm/syscall.h&gt;</filename></title>
-+
-+  <para>
-+    An arch provides <filename>&lt;asm/syscall.h&gt;</filename> that
-+    defines these as inlines, or declares them as exported functions.
-+    These interfaces are described in <xref linkend="syscall"/>.
-+  </para>
-+
-+</sect2>
-+
-+<sect2 id="arch-tracehook">
-+  <title><filename>&lt;linux/tracehook.h&gt;</filename></title>
-+
-+  <para>
-+    An arch must define <constant>TIF_NOTIFY_RESUME</constant>
-+    and <constant>TIF_SYSCALL_TRACE</constant>
-+    in its <filename>&lt;asm/thread_info.h&gt;</filename>.
-+    The arch code must call the following functions, all declared
-+    in <filename>&lt;linux/tracehook.h&gt;</filename> and
-+    described in <xref linkend="tracehook"/>:
-+
-+    <itemizedlist>
-+      <listitem>
-+	<para><function>tracehook_notify_resume</function></para>
-+      </listitem>
-+      <listitem>
-+	<para><function>tracehook_report_syscall_entry</function></para>
-+      </listitem>
-+      <listitem>
-+	<para><function>tracehook_report_syscall_exit</function></para>
-+      </listitem>
-+      <listitem>
-+	<para><function>tracehook_signal_handler</function></para>
-+      </listitem>
-+    </itemizedlist>
-+
-+  </para>
-+
-+</sect2>
-+
-+</sect1>
-+
-+</chapter>
-+
-+</book>
-diff --git a/fs/proc/array.c b/fs/proc/array.c
-index fff6572..a67bd83 100644  
---- a/fs/proc/array.c
-+++ b/fs/proc/array.c
-@@ -81,6 +81,7 @@
- #include <linux/pid_namespace.h>
- #include <linux/ptrace.h>
- #include <linux/tracehook.h>
-+#include <linux/utrace.h>
- 
- #include <asm/pgtable.h>
- #include <asm/processor.h>
-@@ -192,6 +193,8 @@ static inline void task_state(struct seq
- 		cred->uid, cred->euid, cred->suid, cred->fsuid,
- 		cred->gid, cred->egid, cred->sgid, cred->fsgid);
- 
-+	task_utrace_proc_status(m, p);
-+
- 	task_lock(p);
- 	if (p->files)
- 		fdt = files_fdtable(p->files);
-diff --git a/include/linux/sched.h b/include/linux/sched.h
-index 09f26df..e6fa5e9 100644  
---- a/include/linux/sched.h
-+++ b/include/linux/sched.h
-@@ -1357,6 +1357,11 @@ struct task_struct {
- #endif
- 	seccomp_t seccomp;
- 
-+#ifdef CONFIG_UTRACE
-+	struct utrace *utrace;
-+	unsigned long utrace_flags;
-+#endif
-+
- /* Thread group tracking */
-    	u32 parent_exec_id;
-    	u32 self_exec_id;
-diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
-index 98917e9..afba8f8 100644  
---- a/include/linux/tracehook.h
-+++ b/include/linux/tracehook.h
-@@ -49,6 +49,7 @@
- #include <linux/sched.h>
- #include <linux/ptrace.h>
- #include <linux/security.h>
-+#include <linux/utrace.h>
- struct linux_binprm;
- 
- /**
-@@ -63,6 +64,8 @@ struct linux_binprm;
-  */
- static inline int tracehook_expect_breakpoints(struct task_struct *task)
- {
-+	if (unlikely(task_utrace_flags(task) & UTRACE_EVENT(SIGNAL_CORE)))
-+		return 1;
- 	return (task_ptrace(task) & PT_PTRACED) != 0;
- }
- 
-@@ -111,6 +114,9 @@ static inline void ptrace_report_syscall
- static inline __must_check int tracehook_report_syscall_entry(
- 	struct pt_regs *regs)
- {
-+	if ((task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_ENTRY)) &&
-+	    utrace_report_syscall_entry(regs))
-+		return 1;
- 	ptrace_report_syscall(regs);
- 	return 0;
- }
-@@ -134,6 +140,9 @@ static inline __must_check int tracehook
-  */
- static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
- {
-+	if (task_utrace_flags(current) & UTRACE_EVENT(SYSCALL_EXIT))
-+		utrace_report_syscall_exit(regs);
-+
- 	if (step && (task_ptrace(current) & PT_PTRACED)) {
- 		siginfo_t info;
- 		user_single_step_siginfo(current, regs, &info);
-@@ -201,6 +210,8 @@ static inline void tracehook_report_exec
- 					 struct linux_binprm *bprm,
- 					 struct pt_regs *regs)
- {
-+	if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(EXEC)))
-+		utrace_report_exec(fmt, bprm, regs);
- 	if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) &&
- 	    unlikely(task_ptrace(current) & PT_PTRACED))
- 		send_sig(SIGTRAP, current, 0);
-@@ -218,10 +229,37 @@ static inline void tracehook_report_exec
-  */
- static inline void tracehook_report_exit(long *exit_code)
- {
-+	if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(EXIT)))
-+		utrace_report_exit(exit_code);
- 	ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code);
- }
- 
- /**
-+ * tracehook_init_task - task_struct has just been copied
-+ * @task:		new &struct task_struct just copied from parent
-+ *
-+ * Called from do_fork() when @task has just been duplicated.
-+ * After this, @task will be passed to tracehook_free_task()
-+ * even if the rest of its setup fails before it is fully created.
-+ */
-+static inline void tracehook_init_task(struct task_struct *task)
-+{
-+	utrace_init_task(task);
-+}
-+
-+/**
-+ * tracehook_free_task - task_struct is being freed
-+ * @task:		dead &struct task_struct being freed
-+ *
-+ * Called from free_task() when @task is no longer in use.
-+ */
-+static inline void tracehook_free_task(struct task_struct *task)
-+{
-+	if (task_utrace_struct(task))
-+		utrace_free_task(task);
-+}
-+
-+/**
-  * tracehook_prepare_clone - prepare for new child to be cloned
-  * @clone_flags:	%CLONE_* flags from clone/fork/vfork system call
-  *
-@@ -285,6 +323,8 @@ static inline void tracehook_report_clon
- 					  unsigned long clone_flags,
- 					  pid_t pid, struct task_struct *child)
- {
-+	if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(CLONE)))
-+		utrace_report_clone(clone_flags, child);
- 	if (unlikely(task_ptrace(child))) {
- 		/*
- 		 * It doesn't matter who attached/attaching to this
-@@ -317,6 +357,9 @@ static inline void tracehook_report_clon
- 						   pid_t pid,
- 						   struct task_struct *child)
- {
-+	if (unlikely(task_utrace_flags(current) & UTRACE_EVENT(CLONE)) &&
-+	    (clone_flags & CLONE_VFORK))
-+		utrace_finish_vfork(current);
- 	if (unlikely(trace))
- 		ptrace_event(0, trace, pid);
- }
-@@ -351,6 +394,10 @@ static inline void tracehook_report_vfor
-  */
- static inline void tracehook_prepare_release_task(struct task_struct *task)
- {
-+	/* see utrace_add_engine() about this barrier */
-+	smp_mb();
-+	if (task_utrace_flags(task))
-+		utrace_maybe_reap(task, task_utrace_struct(task), true);
- }
- 
- /**
-@@ -365,6 +412,7 @@ static inline void tracehook_prepare_rel
- static inline void tracehook_finish_release_task(struct task_struct *task)
- {
- 	ptrace_release_task(task);
-+	BUG_ON(task->exit_state != EXIT_DEAD);
- }
- 
- /**
-@@ -386,6 +434,8 @@ static inline void tracehook_signal_hand
- 					    const struct k_sigaction *ka,
- 					    struct pt_regs *regs, int stepping)
- {
-+	if (task_utrace_flags(current))
-+		utrace_signal_handler(current, stepping);
- 	if (stepping && (task_ptrace(current) & PT_PTRACED))
- 		ptrace_notify(SIGTRAP);
- }
-@@ -403,6 +453,8 @@ static inline void tracehook_signal_hand
- static inline int tracehook_consider_ignored_signal(struct task_struct *task,
- 						    int sig)
- {
-+	if (unlikely(task_utrace_flags(task) & UTRACE_EVENT(SIGNAL_IGN)))
-+		return 1;
- 	return (task_ptrace(task) & PT_PTRACED) != 0;
- }
- 
-@@ -422,6 +474,9 @@ static inline int tracehook_consider_ign
- static inline int tracehook_consider_fatal_signal(struct task_struct *task,
- 						  int sig)
- {
-+	if (unlikely(task_utrace_flags(task) & (UTRACE_EVENT(SIGNAL_TERM) |
-+						UTRACE_EVENT(SIGNAL_CORE))))
-+		return 1;
- 	return (task_ptrace(task) & PT_PTRACED) != 0;
- }
- 
-@@ -436,6 +491,8 @@ static inline int tracehook_consider_fat
-  */
- static inline int tracehook_force_sigpending(void)
- {
-+	if (unlikely(task_utrace_flags(current)))
-+		return utrace_interrupt_pending();
- 	return 0;
- }
- 
-@@ -465,6 +522,8 @@ static inline int tracehook_get_signal(s
- 				       siginfo_t *info,
- 				       struct k_sigaction *return_ka)
- {
-+	if (unlikely(task_utrace_flags(task)))
-+		return utrace_get_signal(task, regs, info, return_ka);
- 	return 0;
- }
- 
-@@ -492,6 +551,8 @@ static inline int tracehook_get_signal(s
-  */
- static inline int tracehook_notify_jctl(int notify, int why)
- {
-+	if (task_utrace_flags(current) & UTRACE_EVENT(JCTL))
-+		utrace_report_jctl(notify, why);
- 	return notify ?: task_ptrace(current) ? why : 0;
- }
- 
-@@ -502,6 +563,8 @@ static inline int tracehook_notify_jctl(
-  */
- static inline void tracehook_finish_jctl(void)
- {
-+	if (task_utrace_flags(current))
-+		utrace_finish_stop();
- }
- 
- #define DEATH_REAP			-1
-@@ -524,6 +587,8 @@ static inline void tracehook_finish_jctl
- static inline int tracehook_notify_death(struct task_struct *task,
- 					 void **death_cookie, int group_dead)
- {
-+	*death_cookie = task_utrace_struct(task);
-+
- 	if (task_detached(task))
- 		return task->ptrace ? SIGCHLD : DEATH_REAP;
- 
-@@ -560,6 +625,15 @@ static inline void tracehook_report_deat
- 					  int signal, void *death_cookie,
- 					  int group_dead)
- {
-+	/*
-+	 * If utrace_set_events() was just called to enable
-+	 * UTRACE_EVENT(DEATH), then we are obliged to call
-+	 * utrace_report_death() and not miss it.  utrace_set_events()
-+	 * checks @task->exit_state under tasklist_lock to synchronize
-+	 * with exit_notify(), the caller.
-+	 */
-+	if (task_utrace_flags(task) & _UTRACE_DEATH_EVENTS)
-+		utrace_report_death(task, death_cookie, group_dead, signal);
- }
- 
- #ifdef TIF_NOTIFY_RESUME
-@@ -589,10 +663,21 @@ static inline void set_notify_resume(str
-  * asynchronously, this will be called again before we return to
-  * user mode.
-  *
-- * Called without locks.
-+ * Called without locks.  However, on some machines this may be
-+ * called with interrupts disabled.
-  */
- static inline void tracehook_notify_resume(struct pt_regs *regs)
- {
-+	struct task_struct *task = current;
-+	/*
-+	 * Prevent the following store/load from getting ahead of the
-+	 * caller which clears TIF_NOTIFY_RESUME. This pairs with the
-+	 * implicit mb() before setting TIF_NOTIFY_RESUME in
-+	 * set_notify_resume().
-+	 */
-+	smp_mb();
-+	if (task_utrace_flags(task))
-+		utrace_resume(task, regs);
- }
- #endif	/* TIF_NOTIFY_RESUME */
- 
-diff --git a/include/linux/utrace.h b/include/linux/utrace.h
-new file mode 100644
-index ...f251efe 100644  
---- /dev/null
-+++ b/include/linux/utrace.h
-@@ -0,0 +1,692 @@
-+/*
-+ * utrace infrastructure interface for debugging user processes
-+ *
-+ * Copyright (C) 2006-2009 Red Hat, Inc.  All rights reserved.
-+ *
-+ * This copyrighted material is made available to anyone wishing to use,
-+ * modify, copy, or redistribute it subject to the terms and conditions
-+ * of the GNU General Public License v.2.
-+ *
-+ * Red Hat Author: Roland McGrath.
-+ *
-+ * This interface allows for notification of interesting events in a
-+ * thread.  It also mediates access to thread state such as registers.
-+ * Multiple unrelated users can be associated with a single thread.
-+ * We call each of these a tracing engine.
-+ *
-+ * A tracing engine starts by calling utrace_attach_task() or
-+ * utrace_attach_pid() on the chosen thread, passing in a set of hooks
-+ * (&struct utrace_engine_ops), and some associated data.  This produces a
-+ * &struct utrace_engine, which is the handle used for all other
-+ * operations.  An attached engine has its ops vector, its data, and an
-+ * event mask controlled by utrace_set_events().
-+ *
-+ * For each event bit that is set, that engine will get the
-+ * appropriate ops->report_*() callback when the event occurs.  The
-+ * &struct utrace_engine_ops need not provide callbacks for an event
-+ * unless the engine sets one of the associated event bits.
-+ */
-+
-+#ifndef _LINUX_UTRACE_H
-+#define _LINUX_UTRACE_H	1
-+
-+#include <linux/list.h>
-+#include <linux/kref.h>
-+#include <linux/signal.h>
-+#include <linux/sched.h>
-+
-+struct linux_binprm;
-+struct pt_regs;
-+struct utrace;
-+struct user_regset;
-+struct user_regset_view;
-+
-+/*
-+ * Event bits passed to utrace_set_events().
-+ * These appear in &struct task_struct.@utrace_flags
-+ * and &struct utrace_engine.@flags.
-+ */
-+enum utrace_events {
-+	_UTRACE_EVENT_QUIESCE,	/* Thread is available for examination.  */
-+	_UTRACE_EVENT_REAP,  	/* Zombie reaped, no more tracing possible.  */
-+	_UTRACE_EVENT_CLONE,	/* Successful clone/fork/vfork just done.  */
-+	_UTRACE_EVENT_EXEC,	/* Successful execve just completed.  */
-+	_UTRACE_EVENT_EXIT,	/* Thread exit in progress.  */
-+	_UTRACE_EVENT_DEATH,	/* Thread has died.  */
-+	_UTRACE_EVENT_SYSCALL_ENTRY, /* User entered kernel for system call. */
-+	_UTRACE_EVENT_SYSCALL_EXIT, /* Returning to user after system call.  */
-+	_UTRACE_EVENT_SIGNAL,	/* Signal delivery will run a user handler.  */
-+	_UTRACE_EVENT_SIGNAL_IGN, /* No-op signal to be delivered.  */
-+	_UTRACE_EVENT_SIGNAL_STOP, /* Signal delivery will suspend.  */
-+	_UTRACE_EVENT_SIGNAL_TERM, /* Signal delivery will terminate.  */
-+	_UTRACE_EVENT_SIGNAL_CORE, /* Signal delivery will dump core.  */
-+	_UTRACE_EVENT_JCTL,	/* Job control stop or continue completed.  */
-+	_UTRACE_NEVENTS
-+};
-+#define UTRACE_EVENT(type)	(1UL << _UTRACE_EVENT_##type)
-+
-+/*
-+ * All the kinds of signal events.
-+ * These all use the @report_signal() callback.
-+ */
-+#define UTRACE_EVENT_SIGNAL_ALL	(UTRACE_EVENT(SIGNAL) \
-+				 | UTRACE_EVENT(SIGNAL_IGN) \
-+				 | UTRACE_EVENT(SIGNAL_STOP) \
-+				 | UTRACE_EVENT(SIGNAL_TERM) \
-+				 | UTRACE_EVENT(SIGNAL_CORE))
-+/*
-+ * Both kinds of syscall events; these call the @report_syscall_entry()
-+ * and @report_syscall_exit() callbacks, respectively.
-+ */
-+#define UTRACE_EVENT_SYSCALL	\
-+	(UTRACE_EVENT(SYSCALL_ENTRY) | UTRACE_EVENT(SYSCALL_EXIT))
-+
-+/*
-+ * The event reports triggered synchronously by task death.
-+ */
-+#define _UTRACE_DEATH_EVENTS (UTRACE_EVENT(DEATH) | UTRACE_EVENT(QUIESCE))
-+
-+/*
-+ * Hooks in <linux/tracehook.h> call these entry points to the utrace dispatch.
-+ */
-+void utrace_free_task(struct task_struct *);
-+bool utrace_interrupt_pending(void);
-+void utrace_resume(struct task_struct *, struct pt_regs *);
-+void utrace_finish_stop(void);
-+void utrace_maybe_reap(struct task_struct *, struct utrace *, bool);
-+int utrace_get_signal(struct task_struct *, struct pt_regs *,
-+		      siginfo_t *, struct k_sigaction *);
-+void utrace_report_clone(unsigned long, struct task_struct *);
-+void utrace_finish_vfork(struct task_struct *);
-+void utrace_report_exit(long *exit_code);
-+void utrace_report_death(struct task_struct *, struct utrace *, bool, int);
-+void utrace_report_jctl(int notify, int type);
-+void utrace_report_exec(struct linux_binfmt *, struct linux_binprm *,
-+			struct pt_regs *regs);
-+bool utrace_report_syscall_entry(struct pt_regs *);
-+void utrace_report_syscall_exit(struct pt_regs *);
-+void utrace_signal_handler(struct task_struct *, int);
-+
-+#ifndef CONFIG_UTRACE
-+
-+/*
-+ * <linux/tracehook.h> uses these accessors to avoid #ifdef CONFIG_UTRACE.
-+ */
-+static inline unsigned long task_utrace_flags(struct task_struct *task)
-+{
-+	return 0;
-+}
-+static inline struct utrace *task_utrace_struct(struct task_struct *task)
-+{
-+	return NULL;
-+}
-+static inline void utrace_init_task(struct task_struct *child)
-+{
-+}
-+
-+static inline void task_utrace_proc_status(struct seq_file *m,
-+					   struct task_struct *p)
-+{
-+}
-+
-+#else  /* CONFIG_UTRACE */
-+
-+static inline unsigned long task_utrace_flags(struct task_struct *task)
-+{
-+	return task->utrace_flags;
-+}
-+
-+static inline struct utrace *task_utrace_struct(struct task_struct *task)
-+{
-+	struct utrace *utrace;
-+
-+	/*
-+	 * This barrier ensures that any prior load of task->utrace_flags
-+	 * is ordered before this load of task->utrace.  We use those
-+	 * utrace_flags checks in the hot path to decide to call into
-+	 * the utrace code.  The first attach installs task->utrace before
-+	 * setting task->utrace_flags nonzero with implicit barrier in
-+	 * between, see utrace_add_engine().
-+	 */
-+	smp_rmb();
-+	utrace = task->utrace;
-+
-+	smp_read_barrier_depends(); /* See utrace_task_alloc().  */
-+	return utrace;
-+}
-+
-+static inline void utrace_init_task(struct task_struct *task)
-+{
-+	task->utrace_flags = 0;
-+	task->utrace = NULL;
-+}
-+
-+void task_utrace_proc_status(struct seq_file *m, struct task_struct *p);
-+
-+
-+/*
-+ * Version number of the API defined in this file.  This will change
-+ * whenever a tracing engine's code would need some updates to keep
-+ * working.  We maintain this here for the benefit of tracing engine code
-+ * that is developed concurrently with utrace API improvements before they
-+ * are merged into the kernel, making LINUX_VERSION_CODE checks unwieldy.
-+ */
-+#define UTRACE_API_VERSION	20091216
-+
-+/**
-+ * enum utrace_resume_action - engine's choice of action for a traced task
-+ * @UTRACE_STOP:		Stay quiescent after callbacks.
-+ * @UTRACE_INTERRUPT:		Make @report_signal() callback soon.
-+ * @UTRACE_REPORT:		Make some callback soon.
-+ * @UTRACE_SINGLESTEP:		Resume in user mode for one instruction.
-+ * @UTRACE_BLOCKSTEP:		Resume in user mode until next branch.
-+ * @UTRACE_RESUME:		Resume normally in user mode.
-+ * @UTRACE_DETACH:		Detach my engine (implies %UTRACE_RESUME).
-+ *
-+ * See utrace_control() for detailed descriptions of each action.  This is
-+ * encoded in the @action argument and the return value for every callback
-+ * with a &u32 return value.
-+ *
-+ * The order of these is important.  When there is more than one engine,
-+ * each supplies its choice and the smallest value prevails.
-+ */
-+enum utrace_resume_action {
-+	UTRACE_STOP,
-+	UTRACE_INTERRUPT,
-+	UTRACE_REPORT,
-+	UTRACE_SINGLESTEP,
-+	UTRACE_BLOCKSTEP,
-+	UTRACE_RESUME,
-+	UTRACE_DETACH,
-+	UTRACE_RESUME_MAX
-+};
-+#define UTRACE_RESUME_BITS	(ilog2(UTRACE_RESUME_MAX) + 1)
-+#define UTRACE_RESUME_MASK	((1 << UTRACE_RESUME_BITS) - 1)
-+
-+/**
-+ * utrace_resume_action - &enum utrace_resume_action from callback action
-+ * @action:		&u32 callback @action argument or return value
-+ *
-+ * This extracts the &enum utrace_resume_action from @action,
-+ * which is the @action argument to a &struct utrace_engine_ops
-+ * callback or the return value from one.
-+ */
-+static inline enum utrace_resume_action utrace_resume_action(u32 action)
-+{
-+	return action & UTRACE_RESUME_MASK;
-+}
-+
-+/**
-+ * enum utrace_signal_action - disposition of signal
-+ * @UTRACE_SIGNAL_DELIVER:	Deliver according to sigaction.
-+ * @UTRACE_SIGNAL_IGN:		Ignore the signal.
-+ * @UTRACE_SIGNAL_TERM:		Terminate the process.
-+ * @UTRACE_SIGNAL_CORE:		Terminate with core dump.
-+ * @UTRACE_SIGNAL_STOP:		Deliver as absolute stop.
-+ * @UTRACE_SIGNAL_TSTP:		Deliver as job control stop.
-+ * @UTRACE_SIGNAL_REPORT:	Reporting before pending signals.
-+ * @UTRACE_SIGNAL_HANDLER:	Reporting after signal handler setup.
-+ *
-+ * This is encoded in the @action argument and the return value for
-+ * a @report_signal() callback.  It says what will happen to the
-+ * signal described by the &siginfo_t parameter to the callback.
-+ *
-+ * The %UTRACE_SIGNAL_REPORT value is used in an @action argument when
-+ * a tracing report is being made before dequeuing any pending signal.
-+ * If this is immediately after a signal handler has been set up, then
-+ * %UTRACE_SIGNAL_HANDLER is used instead.  A @report_signal callback
-+ * that uses %UTRACE_SIGNAL_DELIVER|%UTRACE_SINGLESTEP will ensure
-+ * it sees a %UTRACE_SIGNAL_HANDLER report.
-+ */
-+enum utrace_signal_action {
-+	UTRACE_SIGNAL_DELIVER	= 0x00,
-+	UTRACE_SIGNAL_IGN	= 0x10,
-+	UTRACE_SIGNAL_TERM	= 0x20,
-+	UTRACE_SIGNAL_CORE	= 0x30,
-+	UTRACE_SIGNAL_STOP	= 0x40,
-+	UTRACE_SIGNAL_TSTP	= 0x50,
-+	UTRACE_SIGNAL_REPORT	= 0x60,
-+	UTRACE_SIGNAL_HANDLER	= 0x70
-+};
-+#define	UTRACE_SIGNAL_MASK	0xf0
-+#define UTRACE_SIGNAL_HOLD	0x100 /* Flag, push signal back on queue.  */
-+
-+/**
-+ * utrace_signal_action - &enum utrace_signal_action from callback action
-+ * @action:		@report_signal callback @action argument or return value
-+ *
-+ * This extracts the &enum utrace_signal_action from @action, which
-+ * is the @action argument to a @report_signal callback or the
-+ * return value from one.
-+ */
-+static inline enum utrace_signal_action utrace_signal_action(u32 action)
-+{
-+	return action & UTRACE_SIGNAL_MASK;
-+}
-+
-+/**
-+ * enum utrace_syscall_action - disposition of system call attempt
-+ * @UTRACE_SYSCALL_RUN:		Run the system call.
-+ * @UTRACE_SYSCALL_ABORT:	Don't run the system call.
-+ *
-+ * This is encoded in the @action argument and the return value for
-+ * a @report_syscall_entry callback.
-+ */
-+enum utrace_syscall_action {
-+	UTRACE_SYSCALL_RUN	= 0x00,
-+	UTRACE_SYSCALL_ABORT	= 0x10
-+};
-+#define	UTRACE_SYSCALL_MASK	0xf0
-+#define	UTRACE_SYSCALL_RESUMED	0x100 /* Flag, report_syscall_entry() repeats */
-+
-+/**
-+ * utrace_syscall_action - &enum utrace_syscall_action from callback action
-+ * @action:		@report_syscall_entry callback @action or return value
-+ *
-+ * This extracts the &enum utrace_syscall_action from @action, which
-+ * is the @action argument to a @report_syscall_entry callback or the
-+ * return value from one.
-+ */
-+static inline enum utrace_syscall_action utrace_syscall_action(u32 action)
-+{
-+	return action & UTRACE_SYSCALL_MASK;
-+}
-+
-+/*
-+ * Flags for utrace_attach_task() and utrace_attach_pid().
-+ */
-+#define UTRACE_ATTACH_MATCH_OPS		0x0001 /* Match engines on ops.  */
-+#define UTRACE_ATTACH_MATCH_DATA	0x0002 /* Match engines on data.  */
-+#define UTRACE_ATTACH_MATCH_MASK	0x000f
-+#define UTRACE_ATTACH_CREATE		0x0010 /* Attach a new engine.  */
-+#define UTRACE_ATTACH_EXCLUSIVE		0x0020 /* Refuse if existing match.  */
-+
-+/**
-+ * struct utrace_engine - per-engine structure
-+ * @ops:	&struct utrace_engine_ops pointer passed to utrace_attach_task()
-+ * @data:	engine-private &void * passed to utrace_attach_task()
-+ * @flags:	event mask set by utrace_set_events() plus internal flag bits
-+ *
-+ * The task itself never has to worry about engines detaching while
-+ * it's doing event callbacks.  These structures are removed from the
-+ * task's active list only when it's stopped, or by the task itself.
-+ *
-+ * utrace_engine_get() and utrace_engine_put() maintain a reference count.
-+ * When it drops to zero, the structure is freed.  One reference is held
-+ * implicitly while the engine is attached to its task.
-+ */
-+struct utrace_engine {
-+/* private: */
-+	struct kref kref;
-+	void (*release)(void *);
-+	struct list_head entry;
-+
-+/* public: */
-+	const struct utrace_engine_ops *ops;
-+	void *data;
-+
-+	unsigned long flags;
-+};
-+
-+/**
-+ * utrace_engine_get - acquire a reference on a &struct utrace_engine
-+ * @engine:	&struct utrace_engine pointer
-+ *
-+ * You must hold a reference on @engine, and you get another.
-+ */
-+static inline void utrace_engine_get(struct utrace_engine *engine)
-+{
-+	kref_get(&engine->kref);
-+}
-+
-+void __utrace_engine_release(struct kref *);
-+
-+/**
-+ * utrace_engine_put - release a reference on a &struct utrace_engine
-+ * @engine:	&struct utrace_engine pointer
-+ *
-+ * You must hold a reference on @engine, and you lose that reference.
-+ * If it was the last one, @engine becomes an invalid pointer.
-+ */
-+static inline void utrace_engine_put(struct utrace_engine *engine)
-+{
-+	kref_put(&engine->kref, __utrace_engine_release);
-+}
-+
-+/**
-+ * struct utrace_engine_ops - tracing engine callbacks
-+ *
-+ * Each @report_*() callback corresponds to an %UTRACE_EVENT(*) bit.
-+ * utrace_set_events() calls on @engine choose which callbacks will
-+ * be made to @engine from @task.
-+ *
-+ * Most callbacks take an @action argument, giving the resume action
-+ * chosen by other tracing engines.  All callbacks take an @engine
-+ * argument.  The @report_reap callback takes a @task argument that
-+ * might or might not be @current.  All other @report_* callbacks
-+ * report an event in the @current task.
-+ *
-+ * For some calls, @action also includes bits specific to that event
-+ * and utrace_resume_action() is used to extract the resume action.
-+ * This shows what would happen if @engine wasn't there, or will if
-+ * the callback's return value uses %UTRACE_RESUME.  This always
-+ * starts as %UTRACE_RESUME when no other tracing is being done on
-+ * this task.
-+ *
-+ * All return values contain &enum utrace_resume_action bits.  For
-+ * some calls, other bits specific to that kind of event are added to
-+ * the resume action bits with OR.  These are the same bits used in
-+ * the @action argument.  The resume action returned by a callback
-+ * does not override previous engines' choices, it only says what
-+ * @engine wants done.  What @current actually does is the action that's
-+ * most constrained among the choices made by all attached engines.
-+ * See utrace_control() for more information on the actions.
-+ *
-+ * When %UTRACE_STOP is used in @report_syscall_entry, then @current
-+ * stops before attempting the system call.  In this case, another
-+ * @report_syscall_entry callback will follow after @current resumes if
-+ * %UTRACE_REPORT or %UTRACE_INTERRUPT was returned by some callback
-+ * or passed to utrace_control().  In a second or later callback,
-+ * %UTRACE_SYSCALL_RESUMED is set in the @action argument to indicate
-+ * a repeat callback still waiting to attempt the same system call
-+ * invocation.  This repeat callback gives each engine an opportunity
-+ * to reexamine registers another engine might have changed while
-+ * @current was held in %UTRACE_STOP.
-+ *
-+ * In other cases, the resume action does not take effect until @current
-+ * is ready to check for signals and return to user mode.  If there
-+ * are more callbacks to be made, the last round of calls determines
-+ * the final action.  A @report_quiesce callback with @event zero, or
-+ * a @report_signal callback, will always be the last one made before
-+ * @current resumes.  Only %UTRACE_STOP is "sticky"--if @engine returned
-+ * %UTRACE_STOP then @current stays stopped unless @engine returns
-+ * different from a following callback.
-+ *
-+ * The report_death() and report_reap() callbacks do not take @action
-+ * arguments, and only %UTRACE_DETACH is meaningful in the return value
-+ * from a report_death() callback.  None of the resume actions applies
-+ * to a dead thread.
-+ *
-+ * All @report_*() hooks are called with no locks held, in a generally
-+ * safe environment when we will be returning to user mode soon (or just
-+ * entered the kernel).  It is fine to block for memory allocation and
-+ * the like, but all hooks are asynchronous and must not block on
-+ * external events!  If you want the thread to block, use %UTRACE_STOP
-+ * in your hook's return value; then later wake it up with utrace_control().
-+ *
-+ * @report_quiesce:
-+ *	Requested by %UTRACE_EVENT(%QUIESCE).
-+ *	This does not indicate any event, but just that @current is in a
-+ *	safe place for examination.  This call is made before each specific
-+ *	event callback, except for @report_reap.  The @event argument gives
-+ *	the %UTRACE_EVENT(@which) value for the event occurring.  This
-+ *	callback might be made for events @engine has not requested, if
-+ *	some other engine is tracing the event; calling utrace_set_events()
-+ *	call here can request the immediate callback for this occurrence of
-+ *	@event.  @event is zero when there is no other event, @current is
-+ *	now ready to check for signals and return to user mode, and some
-+ *	engine has used %UTRACE_REPORT or %UTRACE_INTERRUPT to request this
-+ *	callback.  For this case, if @report_signal is not %NULL, the
-+ *	@report_quiesce callback may be replaced with a @report_signal
-+ *	callback passing %UTRACE_SIGNAL_REPORT in its @action argument,
-+ *	whenever @current is entering the signal-check path anyway.
-+ *
-+ * @report_signal:
-+ *	Requested by %UTRACE_EVENT(%SIGNAL_*) or %UTRACE_EVENT(%QUIESCE).
-+ *	Use utrace_signal_action() and utrace_resume_action() on @action.
-+ *	The signal action is %UTRACE_SIGNAL_REPORT when some engine has
-+ *	used %UTRACE_REPORT or %UTRACE_INTERRUPT; the callback can choose
-+ *	to stop or to deliver an artificial signal, before pending signals.
-+ *	It's %UTRACE_SIGNAL_HANDLER instead when signal handler setup just
-+ *	finished (after a previous %UTRACE_SIGNAL_DELIVER return); this
-+ *	serves in lieu of any %UTRACE_SIGNAL_REPORT callback requested by
-+ *	%UTRACE_REPORT or %UTRACE_INTERRUPT, and is also implicitly
-+ *	requested by %UTRACE_SINGLESTEP or %UTRACE_BLOCKSTEP into the
-+ *	signal delivery.  The other signal actions indicate a signal about
-+ *	to be delivered; the previous engine's return value sets the signal
-+ *	action seen by the the following engine's callback.  The @info data
-+ *	can be changed at will, including @info->si_signo.  The settings in
-+ *	@return_ka determines what %UTRACE_SIGNAL_DELIVER does.  @orig_ka
-+ *	is what was in force before other tracing engines intervened, and
-+ *	it's %NULL when this report began as %UTRACE_SIGNAL_REPORT or
-+ *	%UTRACE_SIGNAL_HANDLER.  For a report without a new signal, @info
-+ *	is left uninitialized and must be set completely by an engine that
-+ *	chooses to deliver a signal; if there was a previous @report_signal
-+ *	callback ending in %UTRACE_STOP and it was just resumed using
-+ *	%UTRACE_REPORT or %UTRACE_INTERRUPT, then @info is left unchanged
-+ *	from the previous callback.  In this way, the original signal can
-+ *	be left in @info while returning %UTRACE_STOP|%UTRACE_SIGNAL_IGN
-+ *	and then found again when resuming with %UTRACE_INTERRUPT.
-+ *	The %UTRACE_SIGNAL_HOLD flag bit can be OR'd into the return value,
-+ *	and might be in @action if the previous engine returned it.  This
-+ *	flag asks that the signal in @info be pushed back on @current's queue
-+ *	so that it will be seen again after whatever action is taken now.
-+ *
-+ * @report_clone:
-+ *	Requested by %UTRACE_EVENT(%CLONE).
-+ *	Event reported for parent, before the new task @child might run.
-+ *	@clone_flags gives the flags used in the clone system call, or
-+ *	equivalent flags for a fork() or vfork() system call.  This
-+ *	function can use utrace_attach_task() on @child.  Then passing
-+ *	%UTRACE_STOP to utrace_control() on @child here keeps the child
-+ *	stopped before it ever runs in user mode, %UTRACE_REPORT or
-+ *	%UTRACE_INTERRUPT ensures a callback from @child before it
-+ *	starts in user mode.
-+ *
-+ * @report_jctl:
-+ *	Requested by %UTRACE_EVENT(%JCTL).
-+ *	Job control event; @type is %CLD_STOPPED or %CLD_CONTINUED,
-+ *	indicating whether we are stopping or resuming now.  If @notify
-+ *	is nonzero, @current is the last thread to stop and so will send
-+ *	%SIGCHLD to its parent after this callback; @notify reflects
-+ *	what the parent's %SIGCHLD has in @si_code, which can sometimes
-+ *	be %CLD_STOPPED even when @type is %CLD_CONTINUED.
-+ *
-+ * @report_exec:
-+ *	Requested by %UTRACE_EVENT(%EXEC).
-+ *	An execve system call has succeeded and the new program is about to
-+ *	start running.  The initial user register state is handy to be tweaked
-+ *	directly in @regs.  @fmt and @bprm gives the details of this exec.
-+ *
-+ * @report_syscall_entry:
-+ *	Requested by %UTRACE_EVENT(%SYSCALL_ENTRY).
-+ *	Thread has entered the kernel to request a system call.
-+ *	The user register state is handy to be tweaked directly in @regs.
-+ *	The @action argument contains an &enum utrace_syscall_action,
-+ *	use utrace_syscall_action() to extract it.  The return value
-+ *	overrides the last engine's action for the system call.
-+ *	If the final action is %UTRACE_SYSCALL_ABORT, no system call
-+ *	is made.  The details of the system call being attempted can
-+ *	be fetched here with syscall_get_nr() and syscall_get_arguments().
-+ *	The parameter registers can be changed with syscall_set_arguments().
-+ *	See above about the %UTRACE_SYSCALL_RESUMED flag in @action.
-+ *	Use %UTRACE_REPORT in the return value to guarantee you get
-+ *	another callback (with %UTRACE_SYSCALL_RESUMED flag) in case
-+ *	@current stops with %UTRACE_STOP before attempting the system call.
-+ *
-+ * @report_syscall_exit:
-+ *	Requested by %UTRACE_EVENT(%SYSCALL_EXIT).
-+ *	Thread is about to leave the kernel after a system call request.
-+ *	The user register state is handy to be tweaked directly in @regs.
-+ *	The results of the system call attempt can be examined here using
-+ *	syscall_get_error() and syscall_get_return_value().  It is safe
-+ *	here to call syscall_set_return_value() or syscall_rollback().
-+ *
-+ * @report_exit:
-+ *	Requested by %UTRACE_EVENT(%EXIT).
-+ *	Thread is exiting and cannot be prevented from doing so,
-+ *	but all its state is still live.  The @code value will be
-+ *	the wait result seen by the parent, and can be changed by
-+ *	this engine or others.  The @orig_code value is the real
-+ *	status, not changed by any tracing engine.  Returning %UTRACE_STOP
-+ *	here keeps @current stopped before it cleans up its state and dies,
-+ *	so it can be examined by other processes.  When @current is allowed
-+ *	to run, it will die and get to the @report_death callback.
-+ *
-+ * @report_death:
-+ *	Requested by %UTRACE_EVENT(%DEATH).
-+ *	Thread is really dead now.  It might be reaped by its parent at
-+ *	any time, or self-reap immediately.  Though the actual reaping
-+ *	may happen in parallel, a report_reap() callback will always be
-+ *	ordered after a report_death() callback.
-+ *
-+ * @report_reap:
-+ *	Requested by %UTRACE_EVENT(%REAP).
-+ *	Called when someone reaps the dead task (parent, init, or self).
-+ *	This means the parent called wait, or else this was a detached
-+ *	thread or a process whose parent ignores SIGCHLD.
-+ *	No more callbacks are made after this one.
-+ *	The engine is always detached.
-+ *	There is nothing more a tracing engine can do about this thread.
-+ *	After this callback, the @engine pointer will become invalid.
-+ *	The @task pointer may become invalid if get_task_struct() hasn't
-+ *	been used to keep it alive.
-+ *	An engine should always request this callback if it stores the
-+ *	@engine pointer or stores any pointer in @engine->data, so it
-+ *	can clean up its data structures.
-+ *	Unlike other callbacks, this can be called from the parent's context
-+ *	rather than from the traced thread itself--it must not delay the
-+ *	parent by blocking.
-+ *
-+ * @release:
-+ *	If not %NULL, this is called after the last utrace_engine_put()
-+ *	call for a &struct utrace_engine, which could be implicit after
-+ *	a %UTRACE_DETACH return from another callback.  Its argument is
-+ *	the engine's @data member.
-+ */
-+struct utrace_engine_ops {
-+	u32 (*report_quiesce)(u32 action, struct utrace_engine *engine,
-+			      unsigned long event);
-+	u32 (*report_signal)(u32 action, struct utrace_engine *engine,
-+			     struct pt_regs *regs,
-+			     siginfo_t *info,
-+			     const struct k_sigaction *orig_ka,
-+			     struct k_sigaction *return_ka);
-+	u32 (*report_clone)(u32 action, struct utrace_engine *engine,
-+			    unsigned long clone_flags,
-+			    struct task_struct *child);
-+	u32 (*report_jctl)(u32 action, struct utrace_engine *engine,
-+			   int type, int notify);
-+	u32 (*report_exec)(u32 action, struct utrace_engine *engine,
-+			   const struct linux_binfmt *fmt,
-+			   const struct linux_binprm *bprm,
-+			   struct pt_regs *regs);
-+	u32 (*report_syscall_entry)(u32 action, struct utrace_engine *engine,
-+				    struct pt_regs *regs);
-+	u32 (*report_syscall_exit)(u32 action, struct utrace_engine *engine,
-+				   struct pt_regs *regs);
-+	u32 (*report_exit)(u32 action, struct utrace_engine *engine,
-+			   long orig_code, long *code);
-+	u32 (*report_death)(struct utrace_engine *engine,
-+			    bool group_dead, int signal);
-+	void (*report_reap)(struct utrace_engine *engine,
-+			    struct task_struct *task);
-+	void (*release)(void *data);
-+};
-+
-+/**
-+ * struct utrace_examiner - private state for using utrace_prepare_examine()
-+ *
-+ * The members of &struct utrace_examiner are private to the implementation.
-+ * This data type holds the state from a call to utrace_prepare_examine()
-+ * to be used by a call to utrace_finish_examine().
-+ */
-+struct utrace_examiner {
-+/* private: */
-+	long state;
-+	unsigned long ncsw;
-+};
-+
-+/*
-+ * These are the exported entry points for tracing engines to use.
-+ * See kernel/utrace.c for their kerneldoc comments with interface details.
-+ */
-+struct utrace_engine *utrace_attach_task(struct task_struct *, int,
-+					 const struct utrace_engine_ops *,
-+					 void *);
-+struct utrace_engine *utrace_attach_pid(struct pid *, int,
-+					const struct utrace_engine_ops *,
-+					void *);
-+int __must_check utrace_control(struct task_struct *,
-+				struct utrace_engine *,
-+				enum utrace_resume_action);
-+int __must_check utrace_set_events(struct task_struct *,
-+				   struct utrace_engine *,
-+				   unsigned long eventmask);
-+int __must_check utrace_barrier(struct task_struct *,
-+				struct utrace_engine *);
-+int __must_check utrace_prepare_examine(struct task_struct *,
-+					struct utrace_engine *,
-+					struct utrace_examiner *);
-+int __must_check utrace_finish_examine(struct task_struct *,
-+				       struct utrace_engine *,
-+				       struct utrace_examiner *);
-+
-+/**
-+ * utrace_control_pid - control a thread being traced by a tracing engine
-+ * @pid:		thread to affect
-+ * @engine:		attached engine to affect
-+ * @action:		&enum utrace_resume_action for thread to do
-+ *
-+ * This is the same as utrace_control(), but takes a &struct pid
-+ * pointer rather than a &struct task_struct pointer.  The caller must
-+ * hold a ref on @pid, but does not need to worry about the task
-+ * staying valid.  If it's been reaped so that @pid points nowhere,
-+ * then this call returns -%ESRCH.
-+ */
-+static inline __must_check int utrace_control_pid(
-+	struct pid *pid, struct utrace_engine *engine,
-+	enum utrace_resume_action action)
-+{
-+	/*
-+	 * We don't bother with rcu_read_lock() here to protect the
-+	 * task_struct pointer, because utrace_control will return
-+	 * -ESRCH without looking at that pointer if the engine is
-+	 * already detached.  A task_struct pointer can't die before
-+	 * all the engines are detached in release_task() first.
-+	 */
-+	struct task_struct *task = pid_task(pid, PIDTYPE_PID);
-+	return unlikely(!task) ? -ESRCH : utrace_control(task, engine, action);
-+}
-+
-+/**
-+ * utrace_set_events_pid - choose which event reports a tracing engine gets
-+ * @pid:		thread to affect
-+ * @engine:		attached engine to affect
-+ * @eventmask:		new event mask
-+ *
-+ * This is the same as utrace_set_events(), but takes a &struct pid
-+ * pointer rather than a &struct task_struct pointer.  The caller must
-+ * hold a ref on @pid, but does not need to worry about the task
-+ * staying valid.  If it's been reaped so that @pid points nowhere,
-+ * then this call returns -%ESRCH.
-+ */
-+static inline __must_check int utrace_set_events_pid(
-+	struct pid *pid, struct utrace_engine *engine, unsigned long eventmask)
-+{
-+	struct task_struct *task = pid_task(pid, PIDTYPE_PID);
-+	return unlikely(!task) ? -ESRCH :
-+		utrace_set_events(task, engine, eventmask);
-+}
-+
-+/**
-+ * utrace_barrier_pid - synchronize with simultaneous tracing callbacks
-+ * @pid:		thread to affect
-+ * @engine:		engine to affect (can be detached)
-+ *
-+ * This is the same as utrace_barrier(), but takes a &struct pid
-+ * pointer rather than a &struct task_struct pointer.  The caller must
-+ * hold a ref on @pid, but does not need to worry about the task
-+ * staying valid.  If it's been reaped so that @pid points nowhere,
-+ * then this call returns -%ESRCH.
-+ */
-+static inline __must_check int utrace_barrier_pid(struct pid *pid,
-+						  struct utrace_engine *engine)
-+{
-+	struct task_struct *task = pid_task(pid, PIDTYPE_PID);
-+	return unlikely(!task) ? -ESRCH : utrace_barrier(task, engine);
-+}
-+
-+#endif	/* CONFIG_UTRACE */
-+
-+#endif	/* linux/utrace.h */
-diff --git a/init/Kconfig b/init/Kconfig
-index c972899..17483b7 100644  
---- a/init/Kconfig
-+++ b/init/Kconfig
-@@ -339,6 +339,15 @@ config AUDIT_TREE
- 	depends on AUDITSYSCALL
- 	select FSNOTIFY
- 
-+config UTRACE
-+	bool "Infrastructure for tracing and debugging user processes"
-+	depends on EXPERIMENTAL
-+	depends on HAVE_ARCH_TRACEHOOK
-+	help
-+	  Enable the utrace process tracing interface.  This is an internal
-+	  kernel interface exported to kernel modules, to track events in
-+	  user threads, extract and change user thread state.
-+
- source "kernel/irq/Kconfig"
- 
- menu "RCU Subsystem"
-diff --git a/kernel/Makefile b/kernel/Makefile
-index 0b5ff08..1172528 100644  
---- a/kernel/Makefile
-+++ b/kernel/Makefile
-@@ -70,6 +70,7 @@ obj-$(CONFIG_IKCONFIG) += configs.o
- obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o
- obj-$(CONFIG_SMP) += stop_machine.o
- obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
-+obj-$(CONFIG_UTRACE) += utrace.o
- obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
- obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
- obj-$(CONFIG_AUDIT_WATCH) += audit_watch.o
-diff --git a/kernel/fork.c b/kernel/fork.c
-index 5447dc7..10a39fe 100644  
---- a/kernel/fork.c
-+++ b/kernel/fork.c
-@@ -162,6 +162,7 @@ void free_task(struct task_struct *tsk)
- 	free_thread_info(tsk->stack);
- 	rt_mutex_debug_task_free(tsk);
- 	ftrace_graph_exit_task(tsk);
-+	tracehook_free_task(tsk);
- 	free_task_struct(tsk);
- }
- EXPORT_SYMBOL(free_task);
-@@ -1018,6 +1019,8 @@ static struct task_struct *copy_process(
- 	if (!p)
- 		goto fork_out;
- 
-+	tracehook_init_task(p);
-+
- 	ftrace_graph_init_task(p);
- 
- 	rt_mutex_init_task(p);
-diff --git a/kernel/ptrace.c b/kernel/ptrace.c
-index 84d9f8f..e275608 100644  
---- a/kernel/ptrace.c
-+++ b/kernel/ptrace.c
-@@ -15,6 +15,7 @@
- #include <linux/highmem.h>
- #include <linux/pagemap.h>
- #include <linux/ptrace.h>
-+#include <linux/utrace.h>
- #include <linux/security.h>
- #include <linux/signal.h>
- #include <linux/audit.h>
-@@ -163,6 +164,14 @@ bool ptrace_may_access(struct task_struc
- 	return !err;
- }
- 
-+/*
-+ * For experimental use of utrace, exclude ptrace on the same task.
-+ */
-+static inline bool exclude_ptrace(struct task_struct *task)
-+{
-+	return unlikely(!!task_utrace_flags(task));
-+}
-+
- int ptrace_attach(struct task_struct *task)
- {
- 	int retval;
-@@ -186,6 +195,8 @@ int ptrace_attach(struct task_struct *ta
- 
- 	task_lock(task);
- 	retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
-+	if (!retval && exclude_ptrace(task))
-+		retval = -EBUSY;
- 	task_unlock(task);
- 	if (retval)
- 		goto unlock_creds;
-@@ -223,6 +234,9 @@ int ptrace_traceme(void)
- {
- 	int ret = -EPERM;
- 
-+	if (exclude_ptrace(current)) /* XXX locking */
-+		return -EBUSY;
-+
- 	write_lock_irq(&tasklist_lock);
- 	/* Are we already being traced? */
- 	if (!current->ptrace) {
-diff --git a/kernel/utrace.c b/kernel/utrace.c
-new file mode 100644
-index ...26d6faf 100644  
---- /dev/null
-+++ b/kernel/utrace.c
-@@ -0,0 +1,2440 @@
-+/*
-+ * utrace infrastructure interface for debugging user processes
-+ *
-+ * Copyright (C) 2006-2010 Red Hat, Inc.  All rights reserved.
-+ *
-+ * This copyrighted material is made available to anyone wishing to use,
-+ * modify, copy, or redistribute it subject to the terms and conditions
-+ * of the GNU General Public License v.2.
-+ *
-+ * Red Hat Author: Roland McGrath.
-+ */
-+
-+#include <linux/utrace.h>
-+#include <linux/tracehook.h>
-+#include <linux/regset.h>
-+#include <asm/syscall.h>
-+#include <linux/ptrace.h>
-+#include <linux/err.h>
-+#include <linux/sched.h>
-+#include <linux/freezer.h>
-+#include <linux/module.h>
-+#include <linux/init.h>
-+#include <linux/slab.h>
-+#include <linux/seq_file.h>
-+
-+
-+/*
-+ * Per-thread structure private to utrace implementation.
-+ * If task_struct.utrace_flags is nonzero, task_struct.utrace
-+ * has always been allocated first.  Once allocated, it is
-+ * never freed until free_task().
-+ *
-+ * The common event reporting loops are done by the task making the
-+ * report without ever taking any locks.  To facilitate this, the two
-+ * lists @attached and @attaching work together for smooth asynchronous
-+ * attaching with low overhead.  Modifying either list requires @lock.
-+ * The @attaching list can be modified any time while holding @lock.
-+ * New engines being attached always go on this list.
-+ *
-+ * The @attached list is what the task itself uses for its reporting
-+ * loops.  When the task itself is not quiescent, it can use the
-+ * @attached list without taking any lock.  Nobody may modify the list
-+ * when the task is not quiescent.  When it is quiescent, that means
-+ * that it won't run again without taking @lock itself before using
-+ * the list.
-+ *
-+ * At each place where we know the task is quiescent (or it's current),
-+ * while holding @lock, we call splice_attaching(), below.  This moves
-+ * the @attaching list members on to the end of the @attached list.
-+ * Since this happens at the start of any reporting pass, any new
-+ * engines attached asynchronously go on the stable @attached list
-+ * in time to have their callbacks seen.
-+ */
-+struct utrace {
-+	spinlock_t lock;
-+	struct list_head attached, attaching;
-+
-+	struct task_struct *cloning;
-+
-+	struct utrace_engine *reporting;
-+
-+	enum utrace_resume_action resume:UTRACE_RESUME_BITS;
-+	unsigned int signal_handler:1;
-+	unsigned int vfork_stop:1; /* need utrace_stop() before vfork wait */
-+	unsigned int death:1;	/* in utrace_report_death() now */
-+	unsigned int reap:1;	/* release_task() has run */
-+	unsigned int pending_attach:1; /* need splice_attaching() */
-+};
-+
-+static struct kmem_cache *utrace_cachep;
-+static struct kmem_cache *utrace_engine_cachep;
-+static const struct utrace_engine_ops utrace_detached_ops; /* forward decl */
-+
-+static int __init utrace_init(void)
-+{
-+	utrace_cachep = KMEM_CACHE(utrace, SLAB_PANIC);
-+	utrace_engine_cachep = KMEM_CACHE(utrace_engine, SLAB_PANIC);
-+	return 0;
-+}
-+module_init(utrace_init);
-+
-+/*
-+ * Set up @task.utrace for the first time.  We can have races
-+ * between two utrace_attach_task() calls here.  The task_lock()
-+ * governs installing the new pointer.  If another one got in first,
-+ * we just punt the new one we allocated.
-+ *
-+ * This returns false only in case of a memory allocation failure.
-+ */
-+static bool utrace_task_alloc(struct task_struct *task)
-+{
-+	struct utrace *utrace = kmem_cache_zalloc(utrace_cachep, GFP_KERNEL);
-+	if (unlikely(!utrace))
-+		return false;
-+	spin_lock_init(&utrace->lock);
-+	INIT_LIST_HEAD(&utrace->attached);
-+	INIT_LIST_HEAD(&utrace->attaching);
-+	utrace->resume = UTRACE_RESUME;
-+	task_lock(task);
-+	if (likely(!task->utrace)) {
-+		/*
-+		 * This barrier makes sure the initialization of the struct
-+		 * precedes the installation of the pointer.  This pairs
-+		 * with smp_read_barrier_depends() in task_utrace_struct().
-+		 */
-+		smp_wmb();
-+		task->utrace = utrace;
-+	}
-+	task_unlock(task);
-+
-+	if (unlikely(task->utrace != utrace))
-+		kmem_cache_free(utrace_cachep, utrace);
-+	return true;
-+}
-+
-+/*
-+ * This is called via tracehook_free_task() from free_task()
-+ * when @task is being deallocated.
-+ */
-+void utrace_free_task(struct task_struct *task)
-+{
-+	kmem_cache_free(utrace_cachep, task->utrace);
-+}
-+
-+/*
-+ * This is calledwhen the task is safely quiescent, i.e. it won't consult
-+ * utrace->attached without the lock.  Move any engines attached
-+ * asynchronously from @utrace->attaching onto the @utrace->attached list.
-+ */
-+static void splice_attaching(struct utrace *utrace)
-+{
-+	lockdep_assert_held(&utrace->lock);
-+	list_splice_tail_init(&utrace->attaching, &utrace->attached);
-+	utrace->pending_attach = 0;
-+}
-+
-+/*
-+ * This is the exported function used by the utrace_engine_put() inline.
-+ */
-+void __utrace_engine_release(struct kref *kref)
-+{
-+	struct utrace_engine *engine = container_of(kref, struct utrace_engine,
-+						    kref);
-+	BUG_ON(!list_empty(&engine->entry));
-+	if (engine->release)
-+		(*engine->release)(engine->data);
-+	kmem_cache_free(utrace_engine_cachep, engine);
-+}
-+EXPORT_SYMBOL_GPL(__utrace_engine_release);
-+
-+static bool engine_matches(struct utrace_engine *engine, int flags,
-+			   const struct utrace_engine_ops *ops, void *data)
-+{
-+	if ((flags & UTRACE_ATTACH_MATCH_OPS) && engine->ops != ops)
-+		return false;
-+	if ((flags & UTRACE_ATTACH_MATCH_DATA) && engine->data != data)
-+		return false;
-+	return engine->ops && engine->ops != &utrace_detached_ops;
-+}
-+
-+static struct utrace_engine *find_matching_engine(
-+	struct utrace *utrace, int flags,
-+	const struct utrace_engine_ops *ops, void *data)
-+{
-+	struct utrace_engine *engine;
-+	list_for_each_entry(engine, &utrace->attached, entry)
-+		if (engine_matches(engine, flags, ops, data))
-+			return engine;
-+	list_for_each_entry(engine, &utrace->attaching, entry)
-+		if (engine_matches(engine, flags, ops, data))
-+			return engine;
-+	return NULL;
-+}
-+
-+/*
-+ * Enqueue @engine, or maybe don't if UTRACE_ATTACH_EXCLUSIVE.
-+ */
-+static int utrace_add_engine(struct task_struct *target,
-+			     struct utrace *utrace,
-+			     struct utrace_engine *engine,
-+			     int flags,
-+			     const struct utrace_engine_ops *ops,
-+			     void *data)
-+{
-+	int ret;
-+
-+	spin_lock(&utrace->lock);
-+
-+	ret = -EEXIST;
-+	if ((flags & UTRACE_ATTACH_EXCLUSIVE) &&
-+	     unlikely(find_matching_engine(utrace, flags, ops, data)))
-+		goto unlock;
-+
-+	/*
-+	 * In case we had no engines before, make sure that
-+	 * utrace_flags is not zero. Since we did unlock+lock
-+	 * at least once after utrace_task_alloc() installed
-+	 * ->utrace, we have the necessary barrier which pairs
-+	 * with rmb() in task_utrace_struct().
-+	 */
-+	ret = -ESRCH;
-+	if (!target->utrace_flags) {
-+		target->utrace_flags = UTRACE_EVENT(REAP);
-+		/*
-+		 * If we race with tracehook_prepare_release_task()
-+		 * make sure that either it sees utrace_flags != 0
-+		 * or we see exit_state == EXIT_DEAD.
-+		 */
-+		smp_mb();
-+		if (unlikely(target->exit_state == EXIT_DEAD)) {
-+			target->utrace_flags = 0;
-+			goto unlock;
-+		}
-+	}
-+
-+	/*
-+	 * Put the new engine on the pending ->attaching list.
-+	 * Make sure it gets onto the ->attached list by the next
-+	 * time it's examined.  Setting ->pending_attach ensures
-+	 * that start_report() takes the lock and splices the lists
-+	 * before the next new reporting pass.
-+	 *
-+	 * When target == current, it would be safe just to call
-+	 * splice_attaching() right here.  But if we're inside a
-+	 * callback, that would mean the new engine also gets
-+	 * notified about the event that precipitated its own
-+	 * creation.  This is not what the user wants.
-+	 */
-+	list_add_tail(&engine->entry, &utrace->attaching);
-+	utrace->pending_attach = 1;
-+	utrace_engine_get(engine);
-+	ret = 0;
-+unlock:
-+	spin_unlock(&utrace->lock);
-+
-+	return ret;
-+}
-+
-+/**
-+ * utrace_attach_task - attach new engine, or look up an attached engine
-+ * @target:	thread to attach to
-+ * @flags:	flag bits combined with OR, see below
-+ * @ops:	callback table for new engine
-+ * @data:	engine private data pointer
-+ *
-+ * The caller must ensure that the @target thread does not get freed,
-+ * i.e. hold a ref or be its parent.  It is always safe to call this
-+ * on @current, or on the @child pointer in a @report_clone callback.
-+ * For most other cases, it's easier to use utrace_attach_pid() instead.
-+ *
-+ * UTRACE_ATTACH_CREATE:
-+ * Create a new engine.  If %UTRACE_ATTACH_CREATE is not specified, you
-+ * only look up an existing engine already attached to the thread.
-+ *
-+ * UTRACE_ATTACH_EXCLUSIVE:
-+ * Attempting to attach a second (matching) engine fails with -%EEXIST.
-+ *
-+ * UTRACE_ATTACH_MATCH_OPS: Only consider engines matching @ops.
-+ * UTRACE_ATTACH_MATCH_DATA: Only consider engines matching @data.
-+ *
-+ * Calls with neither %UTRACE_ATTACH_MATCH_OPS nor %UTRACE_ATTACH_MATCH_DATA
-+ * match the first among any engines attached to @target.  That means that
-+ * %UTRACE_ATTACH_EXCLUSIVE in such a call fails with -%EEXIST if there
-+ * are any engines on @target at all.
-+ */
-+struct utrace_engine *utrace_attach_task(
-+	struct task_struct *target, int flags,
-+	const struct utrace_engine_ops *ops, void *data)
-+{
-+	struct utrace *utrace = task_utrace_struct(target);
-+	struct utrace_engine *engine;
-+	int ret;
-+
-+	if (!(flags & UTRACE_ATTACH_CREATE)) {
-+		if (unlikely(!utrace))
-+			return ERR_PTR(-ENOENT);
-+		spin_lock(&utrace->lock);
-+		engine = find_matching_engine(utrace, flags, ops, data);
-+		if (engine)
-+			utrace_engine_get(engine);
-+		spin_unlock(&utrace->lock);
-+		return engine ?: ERR_PTR(-ENOENT);
-+	}
-+
-+	if (unlikely(!ops) || unlikely(ops == &utrace_detached_ops))
-+		return ERR_PTR(-EINVAL);
-+
-+	if (unlikely(target->flags & PF_KTHREAD))
-+		/*
-+		 * Silly kernel, utrace is for users!
-+		 */
-+		return ERR_PTR(-EPERM);
-+
-+	if (!utrace) {
-+		if (unlikely(!utrace_task_alloc(target)))
-+			return ERR_PTR(-ENOMEM);
-+		utrace = task_utrace_struct(target);
-+	}
-+
-+	engine = kmem_cache_alloc(utrace_engine_cachep, GFP_KERNEL);
-+	if (unlikely(!engine))
-+		return ERR_PTR(-ENOMEM);
-+
-+	/*
-+	 * Initialize the new engine structure.  It starts out with one ref
-+	 * to return.  utrace_add_engine() adds another for being attached.
-+	 */
-+	kref_init(&engine->kref);
-+	engine->flags = 0;
-+	engine->ops = ops;
-+	engine->data = data;
-+	engine->release = ops->release;
-+
-+	ret = utrace_add_engine(target, utrace, engine, flags, ops, data);
-+
-+	if (unlikely(ret)) {
-+		kmem_cache_free(utrace_engine_cachep, engine);
-+		engine = ERR_PTR(ret);
-+	}
-+
-+
-+	return engine;
-+}
-+EXPORT_SYMBOL_GPL(utrace_attach_task);
-+
-+/**
-+ * utrace_attach_pid - attach new engine, or look up an attached engine
-+ * @pid:	&struct pid pointer representing thread to attach to
-+ * @flags:	flag bits combined with OR, see utrace_attach_task()
-+ * @ops:	callback table for new engine
-+ * @data:	engine private data pointer
-+ *
-+ * This is the same as utrace_attach_task(), but takes a &struct pid
-+ * pointer rather than a &struct task_struct pointer.  The caller must
-+ * hold a ref on @pid, but does not need to worry about the task
-+ * staying valid.  If it's been reaped so that @pid points nowhere,
-+ * then this call returns -%ESRCH.
-+ */
-+struct utrace_engine *utrace_attach_pid(
-+	struct pid *pid, int flags,
-+	const struct utrace_engine_ops *ops, void *data)
-+{
-+	struct utrace_engine *engine = ERR_PTR(-ESRCH);
-+	struct task_struct *task = get_pid_task(pid, PIDTYPE_PID);
-+	if (task) {
-+		engine = utrace_attach_task(task, flags, ops, data);
-+		put_task_struct(task);
-+	}
-+	return engine;
-+}
-+EXPORT_SYMBOL_GPL(utrace_attach_pid);
-+
-+/*
-+ * When an engine is detached, the target thread may still see it and
-+ * make callbacks until it quiesces.  We install a special ops vector
-+ * with these two callbacks.  When the target thread quiesces, it can
-+ * safely free the engine itself.  For any event we will always get
-+ * the report_quiesce() callback first, so we only need this one
-+ * pointer to be set.  The only exception is report_reap(), so we
-+ * supply that callback too.
-+ */
-+static u32 utrace_detached_quiesce(u32 action, struct utrace_engine *engine,
-+				   unsigned long event)
-+{
-+	return UTRACE_DETACH;
-+}
-+
-+static void utrace_detached_reap(struct utrace_engine *engine,
-+				 struct task_struct *task)
-+{
-+}
-+
-+static const struct utrace_engine_ops utrace_detached_ops = {
-+	.report_quiesce = &utrace_detached_quiesce,
-+	.report_reap = &utrace_detached_reap
-+};
-+
-+/*
-+ * The caller has to hold a ref on the engine.  If the attached flag is
-+ * true (all but utrace_barrier() calls), the engine is supposed to be
-+ * attached.  If the attached flag is false (utrace_barrier() only),
-+ * then return -ERESTARTSYS for an engine marked for detach but not yet
-+ * fully detached.  The task pointer can be invalid if the engine is
-+ * detached.
-+ *
-+ * Get the utrace lock for the target task.
-+ * Returns the struct if locked, or ERR_PTR(-errno).
-+ *
-+ * This has to be robust against races with:
-+ *	utrace_control(target, UTRACE_DETACH) calls
-+ *	UTRACE_DETACH after reports
-+ *	utrace_report_death
-+ *	utrace_release_task
-+ */
-+static struct utrace *get_utrace_lock(struct task_struct *target,
-+				      struct utrace_engine *engine,
-+				      bool attached)
-+	__acquires(utrace->lock)
-+{
-+	struct utrace *utrace;
-+
-+	rcu_read_lock();
-+
-+	/*
-+	 * If this engine was already detached, bail out before we look at
-+	 * the task_struct pointer at all.  If it's detached after this
-+	 * check, then RCU is still keeping this task_struct pointer valid.
-+	 *
-+	 * The ops pointer is NULL when the engine is fully detached.
-+	 * It's &utrace_detached_ops when it's marked detached but still
-+	 * on the list.  In the latter case, utrace_barrier() still works,
-+	 * since the target might be in the middle of an old callback.
-+	 */
-+	if (unlikely(!engine->ops)) {
-+		rcu_read_unlock();
-+		return ERR_PTR(-ESRCH);
-+	}
-+
-+	if (unlikely(engine->ops == &utrace_detached_ops)) {
-+		rcu_read_unlock();
-+		return attached ? ERR_PTR(-ESRCH) : ERR_PTR(-ERESTARTSYS);
-+	}
-+
-+	utrace = task_utrace_struct(target);
-+	spin_lock(&utrace->lock);
-+	if (unlikely(utrace->reap) || unlikely(!engine->ops) ||
-+	    unlikely(engine->ops == &utrace_detached_ops)) {
-+		/*
-+		 * By the time we got the utrace lock,
-+		 * it had been reaped or detached already.
-+		 */
-+		spin_unlock(&utrace->lock);
-+		utrace = ERR_PTR(-ESRCH);
-+		if (!attached && engine->ops == &utrace_detached_ops)
-+			utrace = ERR_PTR(-ERESTARTSYS);
-+	}
-+	rcu_read_unlock();
-+
-+	return utrace;
-+}
-+
-+/*
-+ * Now that we don't hold any locks, run through any
-+ * detached engines and free their references.  Each
-+ * engine had one implicit ref while it was attached.
-+ */
-+static void put_detached_list(struct list_head *list)
-+{
-+	struct utrace_engine *engine, *next;
-+	list_for_each_entry_safe(engine, next, list, entry) {
-+		list_del_init(&engine->entry);
-+		utrace_engine_put(engine);
-+	}
-+}
-+
-+/*
-+ * We use an extra bit in utrace_engine.flags past the event bits,
-+ * to record whether the engine is keeping the target thread stopped.
-+ *
-+ * This bit is set in task_struct.utrace_flags whenever it is set in any
-+ * engine's flags.  Only utrace_reset() resets it in utrace_flags.
-+ */
-+#define ENGINE_STOP		(1UL << _UTRACE_NEVENTS)
-+
-+static void mark_engine_wants_stop(struct task_struct *task,
-+				   struct utrace_engine *engine)
-+{
-+	engine->flags |= ENGINE_STOP;
-+	task->utrace_flags |= ENGINE_STOP;
-+}
-+
-+static void clear_engine_wants_stop(struct utrace_engine *engine)
-+{
-+	engine->flags &= ~ENGINE_STOP;
-+}
-+
-+static bool engine_wants_stop(struct utrace_engine *engine)
-+{
-+	return (engine->flags & ENGINE_STOP) != 0;
-+}
-+
-+/**
-+ * utrace_set_events - choose which event reports a tracing engine gets
-+ * @target:		thread to affect
-+ * @engine:		attached engine to affect
-+ * @events:		new event mask
-+ *
-+ * This changes the set of events for which @engine wants callbacks made.
-+ *
-+ * This fails with -%EALREADY and does nothing if you try to clear
-+ * %UTRACE_EVENT(%DEATH) when the @report_death callback may already have
-+ * begun, or if you try to newly set %UTRACE_EVENT(%DEATH) or
-+ * %UTRACE_EVENT(%QUIESCE) when @target is already dead or dying.
-+ *
-+ * This fails with -%ESRCH if you try to clear %UTRACE_EVENT(%REAP) when
-+ * the @report_reap callback may already have begun, or when @target has
-+ * already been detached, including forcible detach on reaping.
-+ *
-+ * If @target was stopped before the call, then after a successful call,
-+ * no event callbacks not requested in @events will be made; if
-+ * %UTRACE_EVENT(%QUIESCE) is included in @events, then a
-+ * @report_quiesce callback will be made when @target resumes.
-+ *
-+ * If @target was not stopped and @events excludes some bits that were
-+ * set before, this can return -%EINPROGRESS to indicate that @target
-+ * may have been making some callback to @engine.  When this returns
-+ * zero, you can be sure that no event callbacks you've disabled in
-+ * @events can be made.  If @events only sets new bits that were not set
-+ * before on @engine, then -%EINPROGRESS will never be returned.
-+ *
-+ * To synchronize after an -%EINPROGRESS return, see utrace_barrier().
-+ *
-+ * When @target is @current, -%EINPROGRESS is not returned.  But note
-+ * that a newly-created engine will not receive any callbacks related to
-+ * an event notification already in progress.  This call enables @events
-+ * callbacks to be made as soon as @engine becomes eligible for any
-+ * callbacks, see utrace_attach_task().
-+ *
-+ * These rules provide for coherent synchronization based on %UTRACE_STOP,
-+ * even when %SIGKILL is breaking its normal simple rules.
-+ */
-+int utrace_set_events(struct task_struct *target,
-+		      struct utrace_engine *engine,
-+		      unsigned long events)
-+{
-+	struct utrace *utrace;
-+	unsigned long old_flags, old_utrace_flags;
-+	int ret = -EALREADY;
-+
-+	/*
-+	 * We just ignore the internal bit, so callers can use
-+	 * engine->flags to seed bitwise ops for our argument.
-+	 */
-+	events &= ~ENGINE_STOP;
-+
-+	utrace = get_utrace_lock(target, engine, true);
-+	if (unlikely(IS_ERR(utrace)))
-+		return PTR_ERR(utrace);
-+
-+	old_utrace_flags = target->utrace_flags;
-+	old_flags = engine->flags & ~ENGINE_STOP;
-+
-+	/*
-+	 * If utrace_report_death() is already progress now,
-+	 * it's too late to clear the death event bits.
-+	 */
-+	if (((old_flags & ~events) & _UTRACE_DEATH_EVENTS) && utrace->death)
-+		goto unlock;
-+
-+	/*
-+	 * When setting these flags, it's essential that we really
-+	 * synchronize with exit_notify().  They cannot be set after
-+	 * exit_notify() takes the tasklist_lock.  By holding the read
-+	 * lock here while setting the flags, we ensure that the calls
-+	 * to tracehook_notify_death() and tracehook_report_death() will
-+	 * see the new flags.  This ensures that utrace_release_task()
-+	 * knows positively that utrace_report_death() will be called or
-+	 * that it won't.
-+	 */
-+	if ((events & ~old_flags) & _UTRACE_DEATH_EVENTS) {
-+		read_lock(&tasklist_lock);
-+		if (unlikely(target->exit_state)) {
-+			read_unlock(&tasklist_lock);
-+			goto unlock;
-+		}
-+		target->utrace_flags |= events;
-+		read_unlock(&tasklist_lock);
-+	}
-+
-+	engine->flags = events | (engine->flags & ENGINE_STOP);
-+	target->utrace_flags |= events;
-+
-+	if ((events & UTRACE_EVENT_SYSCALL) &&
-+	    !(old_utrace_flags & UTRACE_EVENT_SYSCALL))
-+		set_tsk_thread_flag(target, TIF_SYSCALL_TRACE);
-+
-+	ret = 0;
-+	if ((old_flags & ~events) && target != current &&
-+	    !task_is_stopped_or_traced(target) && !target->exit_state) {
-+		/*
-+		 * This barrier ensures that our engine->flags changes
-+		 * have hit before we examine utrace->reporting,
-+		 * pairing with the barrier in start_callback().  If
-+		 * @target has not yet hit finish_callback() to clear
-+		 * utrace->reporting, we might be in the middle of a
-+		 * callback to @engine.
-+		 */
-+		smp_mb();
-+		if (utrace->reporting == engine)
-+			ret = -EINPROGRESS;
-+	}
-+unlock:
-+	spin_unlock(&utrace->lock);
-+
-+	return ret;
-+}
-+EXPORT_SYMBOL_GPL(utrace_set_events);
-+
-+/*
-+ * Asynchronously mark an engine as being detached.
-+ *
-+ * This must work while the target thread races with us doing
-+ * start_callback(), defined below.  It uses smp_rmb() between checking
-+ * @engine->flags and using @engine->ops.  Here we change @engine->ops
-+ * first, then use smp_wmb() before changing @engine->flags.  This ensures
-+ * it can check the old flags before using the old ops, or check the old
-+ * flags before using the new ops, or check the new flags before using the
-+ * new ops, but can never check the new flags before using the old ops.
-+ * Hence, utrace_detached_ops might be used with any old flags in place.
-+ * It has report_quiesce() and report_reap() callbacks to handle all cases.
-+ */
-+static void mark_engine_detached(struct utrace_engine *engine)
-+{
-+	engine->ops = &utrace_detached_ops;
-+	smp_wmb();
-+	engine->flags = UTRACE_EVENT(QUIESCE);
-+}
-+
-+/*
-+ * Get @target to stop and return true if it is already stopped now.
-+ * If we return false, it will make some event callback soonish.
-+ * Called with @utrace locked.
-+ */
-+static bool utrace_do_stop(struct task_struct *target, struct utrace *utrace)
-+{
-+	if (task_is_stopped(target)) {
-+		/*
-+		 * Stopped is considered quiescent; when it wakes up, it will
-+		 * go through utrace_finish_stop() before doing anything else.
-+		 */
-+		spin_lock_irq(&target->sighand->siglock);
-+		if (likely(task_is_stopped(target)))
-+			__set_task_state(target, TASK_TRACED);
-+		spin_unlock_irq(&target->sighand->siglock);
-+	} else if (utrace->resume > UTRACE_REPORT) {
-+		utrace->resume = UTRACE_REPORT;
-+		set_notify_resume(target);
-+	}
-+
-+	return task_is_traced(target);
-+}
-+
-+/*
-+ * If the target is not dead it should not be in tracing
-+ * stop any more.  Wake it unless it's in job control stop.
-+ */
-+static void utrace_wakeup(struct task_struct *target, struct utrace *utrace)
-+{
-+	lockdep_assert_held(&utrace->lock);
-+	spin_lock_irq(&target->sighand->siglock);
-+	if (target->signal->flags & SIGNAL_STOP_STOPPED ||
-+	    target->signal->group_stop_count)
-+		target->state = TASK_STOPPED;
-+	else
-+		wake_up_state(target, __TASK_TRACED);
-+	spin_unlock_irq(&target->sighand->siglock);
-+}
-+
-+/*
-+ * This is called when there might be some detached engines on the list or
-+ * some stale bits in @task->utrace_flags.  Clean them up and recompute the
-+ * flags.  Returns true if we're now fully detached.
-+ *
-+ * Called with @utrace->lock held, returns with it released.
-+ * After this returns, @utrace might be freed if everything detached.
-+ */
-+static bool utrace_reset(struct task_struct *task, struct utrace *utrace)
-+	__releases(utrace->lock)
-+{
-+	struct utrace_engine *engine, *next;
-+	unsigned long flags = 0;
-+	LIST_HEAD(detached);
-+
-+	splice_attaching(utrace);
-+
-+	/*
-+	 * Update the set of events of interest from the union
-+	 * of the interests of the remaining tracing engines.
-+	 * For any engine marked detached, remove it from the list.
-+	 * We'll collect them on the detached list.
-+	 */
-+	list_for_each_entry_safe(engine, next, &utrace->attached, entry) {
-+		if (engine->ops == &utrace_detached_ops) {
-+			engine->ops = NULL;
-+			list_move(&engine->entry, &detached);
-+		} else {
-+			flags |= engine->flags | UTRACE_EVENT(REAP);
-+		}
-+	}
-+
-+	if (task->exit_state) {
-+		/*
-+		 * Once it's already dead, we never install any flags
-+		 * except REAP.  When ->exit_state is set and events
-+		 * like DEATH are not set, then they never can be set.
-+		 * This ensures that utrace_release_task() knows
-+		 * positively that utrace_report_death() can never run.
-+		 */
-+		BUG_ON(utrace->death);
-+		flags &= UTRACE_EVENT(REAP);
-+	} else if (!(flags & UTRACE_EVENT_SYSCALL) &&
-+		   test_tsk_thread_flag(task, TIF_SYSCALL_TRACE)) {
-+		clear_tsk_thread_flag(task, TIF_SYSCALL_TRACE);
-+	}
-+
-+	if (!flags) {
-+		/*
-+		 * No more engines, cleared out the utrace.
-+		 */
-+		utrace->resume = UTRACE_RESUME;
-+		utrace->signal_handler = 0;
-+	}
-+
-+	/*
-+	 * If no more engines want it stopped, wake it up.
-+	 */
-+	if (task_is_traced(task) && !(flags & ENGINE_STOP)) {
-+		/*
-+		 * It just resumes, so make sure single-step
-+		 * is not left set.
-+		 */
-+		if (utrace->resume == UTRACE_RESUME)
-+			user_disable_single_step(task);
-+		utrace_wakeup(task, utrace);
-+	}
-+
-+	/*
-+	 * In theory spin_lock() doesn't imply rcu_read_lock().
-+	 * Once we clear ->utrace_flags this task_struct can go away
-+	 * because tracehook_prepare_release_task() path does not take
-+	 * utrace->lock when ->utrace_flags == 0.
-+	 */
-+	rcu_read_lock();
-+	task->utrace_flags = flags;
-+	spin_unlock(&utrace->lock);
-+	rcu_read_unlock();
-+
-+	put_detached_list(&detached);
-+
-+	return !flags;
-+}
-+
-+void utrace_finish_stop(void)
-+{
-+	/*
-+	 * If we were task_is_traced() and then SIGKILL'ed, make
-+	 * sure we do nothing until the tracer drops utrace->lock.
-+	 */
-+	if (unlikely(__fatal_signal_pending(current))) {
-+		struct utrace *utrace = task_utrace_struct(current);
-+		spin_unlock_wait(&utrace->lock);
-+	}
-+}
-+
-+/*
-+ * Perform %UTRACE_STOP, i.e. block in TASK_TRACED until woken up.
-+ * @task == current, @utrace == current->utrace, which is not locked.
-+ * Return true if we were woken up by SIGKILL even though some utrace
-+ * engine may still want us to stay stopped.
-+ */
-+static void utrace_stop(struct task_struct *task, struct utrace *utrace,
-+			enum utrace_resume_action action)
-+{
-+relock:
-+	spin_lock(&utrace->lock);
-+
-+	if (action < utrace->resume) {
-+		/*
-+		 * Ensure a reporting pass when we're resumed.
-+		 */
-+		utrace->resume = action;
-+		if (action == UTRACE_INTERRUPT)
-+			set_thread_flag(TIF_SIGPENDING);
-+		else
-+			set_thread_flag(TIF_NOTIFY_RESUME);
-+	}
-+
-+	/*
-+	 * If the ENGINE_STOP bit is clear in utrace_flags, that means
-+	 * utrace_reset() ran after we processed some UTRACE_STOP return
-+	 * values from callbacks to get here.  If all engines have detached
-+	 * or resumed us, we don't stop.  This check doesn't require
-+	 * siglock, but it should follow the interrupt/report bookkeeping
-+	 * steps (this can matter for UTRACE_RESUME but not UTRACE_DETACH).
-+	 */
-+	if (unlikely(!(task->utrace_flags & ENGINE_STOP))) {
-+		utrace_reset(task, utrace);
-+		if (task->utrace_flags & ENGINE_STOP)
-+			goto relock;
-+		return;
-+	}
-+
-+	/*
-+	 * The siglock protects us against signals.  As well as SIGKILL
-+	 * waking us up, we must synchronize with the signal bookkeeping
-+	 * for stop signals and SIGCONT.
-+	 */
-+	spin_lock_irq(&task->sighand->siglock);
-+
-+	if (unlikely(__fatal_signal_pending(task))) {
-+		spin_unlock_irq(&task->sighand->siglock);
-+		spin_unlock(&utrace->lock);
-+		return;
-+	}
-+
-+	__set_current_state(TASK_TRACED);
-+
-+	/*
-+	 * If there is a group stop in progress,
-+	 * we must participate in the bookkeeping.
-+	 */
-+	if (unlikely(task->signal->group_stop_count) &&
-+			!--task->signal->group_stop_count)
-+		task->signal->flags = SIGNAL_STOP_STOPPED;
-+
-+	spin_unlock_irq(&task->sighand->siglock);
-+	spin_unlock(&utrace->lock);
-+
-+	schedule();
-+
-+	utrace_finish_stop();
-+
-+	/*
-+	 * While in TASK_TRACED, we were considered "frozen enough".
-+	 * Now that we woke up, it's crucial if we're supposed to be
-+	 * frozen that we freeze now before running anything substantial.
-+	 */
-+	try_to_freeze();
-+
-+	/*
-+	 * While we were in TASK_TRACED, complete_signal() considered
-+	 * us "uninterested" in signal wakeups.  Now make sure our
-+	 * TIF_SIGPENDING state is correct for normal running.
-+	 */
-+	spin_lock_irq(&task->sighand->siglock);
-+	recalc_sigpending();
-+	spin_unlock_irq(&task->sighand->siglock);
-+}
-+
-+/*
-+ * Called by release_task() with @reap set to true.
-+ * Called by utrace_report_death() with @reap set to false.
-+ * On reap, make report_reap callbacks and clean out @utrace
-+ * unless still making callbacks.  On death, update bookkeeping
-+ * and handle the reap work if release_task() came in first.
-+ */
-+void utrace_maybe_reap(struct task_struct *target, struct utrace *utrace,
-+		       bool reap)
-+{
-+	struct utrace_engine *engine, *next;
-+	struct list_head attached;
-+
-+	spin_lock(&utrace->lock);
-+
-+	if (reap) {
-+		/*
-+		 * If the target will do some final callbacks but hasn't
-+		 * finished them yet, we know because it clears these event
-+		 * bits after it's done.  Instead of cleaning up here and
-+		 * requiring utrace_report_death() to cope with it, we
-+		 * delay the REAP report and the teardown until after the
-+		 * target finishes its death reports.
-+		 */
-+		utrace->reap = 1;
-+
-+		if (target->utrace_flags & _UTRACE_DEATH_EVENTS) {
-+			spin_unlock(&utrace->lock);
-+			return;
-+		}
-+	} else {
-+		/*
-+		 * After we unlock with this flag clear, any competing
-+		 * utrace_control/utrace_set_events calls know that we've
-+		 * finished our callbacks and any detach bookkeeping.
-+		 */
-+		utrace->death = 0;
-+
-+		if (!utrace->reap) {
-+			/*
-+			 * We're just dead, not reaped yet.  This will
-+			 * reset @target->utrace_flags so the later call
-+			 * with @reap set won't hit the check above.
-+			 */
-+			utrace_reset(target, utrace);
-+			return;
-+		}
-+	}
-+
-+	/*
-+	 * utrace_add_engine() checks ->utrace_flags != 0.  Since
-+	 * @utrace->reap is set, nobody can set or clear UTRACE_EVENT(REAP)
-+	 * in @engine->flags or change @engine->ops and nobody can change
-+	 * @utrace->attached after we drop the lock.
-+	 */
-+	target->utrace_flags = 0;
-+
-+	/*
-+	 * We clear out @utrace->attached before we drop the lock so
-+	 * that find_matching_engine() can't come across any old engine
-+	 * while we are busy tearing it down.
-+	 */
-+	list_replace_init(&utrace->attached, &attached);
-+	list_splice_tail_init(&utrace->attaching, &attached);
-+
-+	spin_unlock(&utrace->lock);
-+
-+	list_for_each_entry_safe(engine, next, &attached, entry) {
-+		if (engine->flags & UTRACE_EVENT(REAP))
-+			engine->ops->report_reap(engine, target);
-+
-+		engine->ops = NULL;
-+		engine->flags = 0;
-+		list_del_init(&engine->entry);
-+
-+		utrace_engine_put(engine);
-+	}
-+}
-+
-+/*
-+ * You can't do anything to a dead task but detach it.
-+ * If release_task() has been called, you can't do that.
-+ *
-+ * On the exit path, DEATH and QUIESCE event bits are set only
-+ * before utrace_report_death() has taken the lock.  At that point,
-+ * the death report will come soon, so disallow detach until it's
-+ * done.  This prevents us from racing with it detaching itself.
-+ *
-+ * Called only when @target->exit_state is nonzero.
-+ */
-+static inline int utrace_control_dead(struct task_struct *target,
-+				      struct utrace *utrace,
-+				      enum utrace_resume_action action)
-+{
-+	lockdep_assert_held(&utrace->lock);
-+
-+	if (action != UTRACE_DETACH || unlikely(utrace->reap))
-+		return -ESRCH;
-+
-+	if (unlikely(utrace->death))
-+		/*
-+		 * We have already started the death report.  We can't
-+		 * prevent the report_death and report_reap callbacks,
-+		 * so tell the caller they will happen.
-+		 */
-+		return -EALREADY;
-+
-+	return 0;
-+}
-+
-+/**
-+ * utrace_control - control a thread being traced by a tracing engine
-+ * @target:		thread to affect
-+ * @engine:		attached engine to affect
-+ * @action:		&enum utrace_resume_action for thread to do
-+ *
-+ * This is how a tracing engine asks a traced thread to do something.
-+ * This call is controlled by the @action argument, which has the
-+ * same meaning as the &enum utrace_resume_action value returned by
-+ * event reporting callbacks.
-+ *
-+ * If @target is already dead (@target->exit_state nonzero),
-+ * all actions except %UTRACE_DETACH fail with -%ESRCH.
-+ *
-+ * The following sections describe each option for the @action argument.
-+ *
-+ * UTRACE_DETACH:
-+ *
-+ * After this, the @engine data structure is no longer accessible,
-+ * and the thread might be reaped.  The thread will start running
-+ * again if it was stopped and no longer has any attached engines
-+ * that want it stopped.
-+ *
-+ * If the @report_reap callback may already have begun, this fails
-+ * with -%ESRCH.  If the @report_death callback may already have
-+ * begun, this fails with -%EALREADY.
-+ *
-+ * If @target is not already stopped, then a callback to this engine
-+ * might be in progress or about to start on another CPU.  If so,
-+ * then this returns -%EINPROGRESS; the detach happens as soon as
-+ * the pending callback is finished.  To synchronize after an
-+ * -%EINPROGRESS return, see utrace_barrier().
-+ *
-+ * If @target is properly stopped before utrace_control() is called,
-+ * then after successful return it's guaranteed that no more callbacks
-+ * to the @engine->ops vector will be made.
-+ *
-+ * The only exception is %SIGKILL (and exec or group-exit by another
-+ * thread in the group), which can cause asynchronous @report_death
-+ * and/or @report_reap callbacks even when %UTRACE_STOP was used.
-+ * (In that event, this fails with -%ESRCH or -%EALREADY, see above.)
-+ *
-+ * UTRACE_STOP:
-+ *
-+ * This asks that @target stop running.  This returns 0 only if
-+ * @target is already stopped, either for tracing or for job
-+ * control.  Then @target will remain stopped until another
-+ * utrace_control() call is made on @engine; @target can be woken
-+ * only by %SIGKILL (or equivalent, such as exec or termination by
-+ * another thread in the same thread group).
-+ *
-+ * This returns -%EINPROGRESS if @target is not already stopped.
-+ * Then the effect is like %UTRACE_REPORT.  A @report_quiesce or
-+ * @report_signal callback will be made soon.  Your callback can
-+ * then return %UTRACE_STOP to keep @target stopped.
-+ *
-+ * This does not interrupt system calls in progress, including ones
-+ * that sleep for a long time.  For that, use %UTRACE_INTERRUPT.
-+ * To interrupt system calls and then keep @target stopped, your
-+ * @report_signal callback can return %UTRACE_STOP.
-+ *
-+ * UTRACE_RESUME:
-+ *
-+ * Just let @target continue running normally, reversing the effect
-+ * of a previous %UTRACE_STOP.  If another engine is keeping @target
-+ * stopped, then it remains stopped until all engines let it resume.
-+ * If @target was not stopped, this has no effect.
-+ *
-+ * UTRACE_REPORT:
-+ *
-+ * This is like %UTRACE_RESUME, but also ensures that there will be
-+ * a @report_quiesce or @report_signal callback made soon.  If
-+ * @target had been stopped, then there will be a callback before it
-+ * resumes running normally.  If another engine is keeping @target
-+ * stopped, then there might be no callbacks until all engines let
-+ * it resume.
-+ *
-+ * Since this is meaningless unless @report_quiesce callbacks will
-+ * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE).
-+ *
-+ * UTRACE_INTERRUPT:
-+ *
-+ * This is like %UTRACE_REPORT, but ensures that @target will make a
-+ * @report_signal callback before it resumes or delivers signals.
-+ * If @target was in a system call or about to enter one, work in
-+ * progress will be interrupted as if by %SIGSTOP.  If another
-+ * engine is keeping @target stopped, then there might be no
-+ * callbacks until all engines let it resume.
-+ *
-+ * This gives @engine an opportunity to introduce a forced signal
-+ * disposition via its @report_signal callback.
-+ *
-+ * UTRACE_SINGLESTEP:
-+ *
-+ * It's invalid to use this unless arch_has_single_step() returned true.
-+ * This is like %UTRACE_RESUME, but resumes for one user instruction only.
-+ *
-+ * Note that passing %UTRACE_SINGLESTEP or %UTRACE_BLOCKSTEP to
-+ * utrace_control() or returning it from an event callback alone does
-+ * not necessarily ensure that stepping will be enabled.  If there are
-+ * more callbacks made to any engine before returning to user mode,
-+ * then the resume action is chosen only by the last set of callbacks.
-+ * To be sure, enable %UTRACE_EVENT(%QUIESCE) and look for the
-+ * @report_quiesce callback with a zero event mask, or the
-+ * @report_signal callback with %UTRACE_SIGNAL_REPORT.
-+ *
-+ * Since this is not robust unless @report_quiesce callbacks will
-+ * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE).
-+ *
-+ * UTRACE_BLOCKSTEP:
-+ *
-+ * It's invalid to use this unless arch_has_block_step() returned true.
-+ * This is like %UTRACE_SINGLESTEP, but resumes for one whole basic
-+ * block of user instructions.
-+ *
-+ * Since this is not robust unless @report_quiesce callbacks will
-+ * be made, it returns -%EINVAL if @engine lacks %UTRACE_EVENT(%QUIESCE).
-+ *
-+ * %UTRACE_BLOCKSTEP devolves to %UTRACE_SINGLESTEP when another
-+ * tracing engine is using %UTRACE_SINGLESTEP at the same time.
-+ */
-+int utrace_control(struct task_struct *target,
-+		   struct utrace_engine *engine,
-+		   enum utrace_resume_action action)
-+{
-+	struct utrace *utrace;
-+	bool reset;
-+	int ret;
-+
-+	if (unlikely(action >= UTRACE_RESUME_MAX)) {
-+		WARN(1, "invalid action argument to utrace_control()!");
-+		return -EINVAL;
-+	}
-+
-+	/*
-+	 * This is a sanity check for a programming error in the caller.
-+	 * Their request can only work properly in all cases by relying on
-+	 * a follow-up callback, but they didn't set one up!  This check
-+	 * doesn't do locking, but it shouldn't matter.  The caller has to
-+	 * be synchronously sure the callback is set up to be operating the
-+	 * interface properly.
-+	 */
-+	if (action >= UTRACE_REPORT && action < UTRACE_RESUME &&
-+	    unlikely(!(engine->flags & UTRACE_EVENT(QUIESCE)))) {
-+		WARN(1, "utrace_control() with no QUIESCE callback in place!");
-+		return -EINVAL;
-+	}
-+
-+	utrace = get_utrace_lock(target, engine, true);
-+	if (unlikely(IS_ERR(utrace)))
-+		return PTR_ERR(utrace);
-+
-+	reset = task_is_traced(target);
-+	ret = 0;
-+
-+	/*
-+	 * ->exit_state can change under us, this doesn't matter.
-+	 * We do not care about ->exit_state in fact, but we do
-+	 * care about ->reap and ->death. If either flag is set,
-+	 * we must also see ->exit_state != 0.
-+	 */
-+	if (unlikely(target->exit_state)) {
-+		ret = utrace_control_dead(target, utrace, action);
-+		if (ret) {
-+			spin_unlock(&utrace->lock);
-+			return ret;
-+		}
-+		reset = true;
-+	}
-+
-+	switch (action) {
-+	case UTRACE_STOP:
-+		mark_engine_wants_stop(target, engine);
-+		if (!reset && !utrace_do_stop(target, utrace))
-+			ret = -EINPROGRESS;
-+		reset = false;
-+		break;
-+
-+	case UTRACE_DETACH:
-+		if (engine_wants_stop(engine))
-+			target->utrace_flags &= ~ENGINE_STOP;
-+		mark_engine_detached(engine);
-+		reset = reset || utrace_do_stop(target, utrace);
-+		if (!reset) {
-+			/*
-+			 * As in utrace_set_events(), this barrier ensures
-+			 * that our engine->flags changes have hit before we
-+			 * examine utrace->reporting, pairing with the barrier
-+			 * in start_callback().  If @target has not yet hit
-+			 * finish_callback() to clear utrace->reporting, we
-+			 * might be in the middle of a callback to @engine.
-+			 */
-+			smp_mb();
-+			if (utrace->reporting == engine)
-+				ret = -EINPROGRESS;
-+		}
-+		break;
-+
-+	case UTRACE_RESUME:
-+		clear_engine_wants_stop(engine);
-+		break;
-+
-+	case UTRACE_BLOCKSTEP:
-+		/*
-+		 * Resume from stopped, step one block.
-+		 * We fall through to treat it like UTRACE_SINGLESTEP.
-+		 */
-+		if (unlikely(!arch_has_block_step())) {
-+			WARN(1, "UTRACE_BLOCKSTEP when !arch_has_block_step()");
-+			action = UTRACE_SINGLESTEP;
-+		}
-+
-+	case UTRACE_SINGLESTEP:
-+		/*
-+		 * Resume from stopped, step one instruction.
-+		 * We fall through to the UTRACE_REPORT case.
-+		 */
-+		if (unlikely(!arch_has_single_step())) {
-+			WARN(1,
-+			     "UTRACE_SINGLESTEP when !arch_has_single_step()");
-+			reset = false;
-+			ret = -EOPNOTSUPP;
-+			break;
-+		}
-+
-+	case UTRACE_REPORT:
-+		/*
-+		 * Make the thread call tracehook_notify_resume() soon.
-+		 * But don't bother if it's already been interrupted.
-+		 * In that case, utrace_get_signal() will be reporting soon.
-+		 */
-+		clear_engine_wants_stop(engine);
-+		if (action < utrace->resume) {
-+			utrace->resume = action;
-+			set_notify_resume(target);
-+		}
-+		break;
-+
-+	case UTRACE_INTERRUPT:
-+		/*
-+		 * Make the thread call tracehook_get_signal() soon.
-+		 */
-+		clear_engine_wants_stop(engine);
-+		if (utrace->resume == UTRACE_INTERRUPT)
-+			break;
-+		utrace->resume = UTRACE_INTERRUPT;
-+
-+		/*
-+		 * If it's not already stopped, interrupt it now.  We need
-+		 * the siglock here in case it calls recalc_sigpending()
-+		 * and clears its own TIF_SIGPENDING.  By taking the lock,
-+		 * we've serialized any later recalc_sigpending() after our
-+		 * setting of utrace->resume to force it on.
-+		 */
-+		if (reset) {
-+			/*
-+			 * This is really just to keep the invariant that
-+			 * TIF_SIGPENDING is set with UTRACE_INTERRUPT.
-+			 * When it's stopped, we know it's always going
-+			 * through utrace_get_signal() and will recalculate.
-+			 */
-+			set_tsk_thread_flag(target, TIF_SIGPENDING);
-+		} else {
-+			struct sighand_struct *sighand;
-+			unsigned long irqflags;
-+			sighand = lock_task_sighand(target, &irqflags);
-+			if (likely(sighand)) {
-+				signal_wake_up(target, 0);
-+				unlock_task_sighand(target, &irqflags);
-+			}
-+		}
-+		break;
-+
-+	default:
-+		BUG();		/* We checked it on entry.  */
-+	}
-+
-+	/*
-+	 * Let the thread resume running.  If it's not stopped now,
-+	 * there is nothing more we need to do.
-+	 */
-+	if (reset)
-+		utrace_reset(target, utrace);
-+	else
-+		spin_unlock(&utrace->lock);
-+
-+	return ret;
-+}
-+EXPORT_SYMBOL_GPL(utrace_control);
-+
-+/**
-+ * utrace_barrier - synchronize with simultaneous tracing callbacks
-+ * @target:		thread to affect
-+ * @engine:		engine to affect (can be detached)
-+ *
-+ * This blocks while @target might be in the midst of making a callback to
-+ * @engine.  It can be interrupted by signals and will return -%ERESTARTSYS.
-+ * A return value of zero means no callback from @target to @engine was
-+ * in progress.  Any effect of its return value (such as %UTRACE_STOP) has
-+ * already been applied to @engine.
-+ *
-+ * It's not necessary to keep the @target pointer alive for this call.
-+ * It's only necessary to hold a ref on @engine.  This will return
-+ * safely even if @target has been reaped and has no task refs.
-+ *
-+ * A successful return from utrace_barrier() guarantees its ordering
-+ * with respect to utrace_set_events() and utrace_control() calls.  If
-+ * @target was not properly stopped, event callbacks just disabled might
-+ * still be in progress; utrace_barrier() waits until there is no chance
-+ * an unwanted callback can be in progress.
-+ */
-+int utrace_barrier(struct task_struct *target, struct utrace_engine *engine)
-+{
-+	struct utrace *utrace;
-+	int ret = -ERESTARTSYS;
-+
-+	if (unlikely(target == current))
-+		return 0;
-+
-+	do {
-+		utrace = get_utrace_lock(target, engine, false);
-+		if (unlikely(IS_ERR(utrace))) {
-+			ret = PTR_ERR(utrace);
-+			if (ret != -ERESTARTSYS)
-+				break;
-+		} else {
-+			/*
-+			 * All engine state changes are done while
-+			 * holding the lock, i.e. before we get here.
-+			 * Since we have the lock, we only need to
-+			 * worry about @target making a callback.
-+			 * When it has entered start_callback() but
-+			 * not yet gotten to finish_callback(), we
-+			 * will see utrace->reporting == @engine.
-+			 * When @target doesn't take the lock, it uses
-+			 * barriers to order setting utrace->reporting
-+			 * before it examines the engine state.
-+			 */
-+			if (utrace->reporting != engine)
-+				ret = 0;
-+			spin_unlock(&utrace->lock);
-+			if (!ret)
-+				break;
-+		}
-+		schedule_timeout_interruptible(1);
-+	} while (!signal_pending(current));
-+
-+	return ret;
-+}
-+EXPORT_SYMBOL_GPL(utrace_barrier);
-+
-+/*
-+ * This is local state used for reporting loops, perhaps optimized away.
-+ */
-+struct utrace_report {
-+	u32 result;
-+	enum utrace_resume_action action;
-+	enum utrace_resume_action resume_action;
-+	bool detaches;
-+	bool spurious;
-+};
-+
-+#define INIT_REPORT(var)			\
-+	struct utrace_report var = {		\
-+		.action = UTRACE_RESUME,	\
-+		.resume_action = UTRACE_RESUME,	\
-+		.spurious = true 		\
-+	}
-+
-+/*
-+ * We are now making the report, so clear the flag saying we need one.
-+ * When there is a new attach, ->pending_attach is set just so we will
-+ * know to do splice_attaching() here before the callback loop.
-+ */
-+static enum utrace_resume_action start_report(struct utrace *utrace)
-+{
-+	enum utrace_resume_action resume = utrace->resume;
-+	if (utrace->pending_attach ||
-+	    (resume > UTRACE_INTERRUPT && resume < UTRACE_RESUME)) {
-+		spin_lock(&utrace->lock);
-+		splice_attaching(utrace);
-+		resume = utrace->resume;
-+		if (resume > UTRACE_INTERRUPT)
-+			utrace->resume = UTRACE_RESUME;
-+		spin_unlock(&utrace->lock);
-+	}
-+	return resume;
-+}
-+
-+static inline void finish_report_reset(struct task_struct *task,
-+				       struct utrace *utrace,
-+				       struct utrace_report *report)
-+{
-+	if (unlikely(report->spurious || report->detaches)) {
-+		spin_lock(&utrace->lock);
-+		if (utrace_reset(task, utrace))
-+			report->action = UTRACE_RESUME;
-+	}
-+}
-+
-+/*
-+ * Complete a normal reporting pass, pairing with a start_report() call.
-+ * This handles any UTRACE_DETACH or UTRACE_REPORT or UTRACE_INTERRUPT
-+ * returns from engine callbacks.  If @will_not_stop is true and any
-+ * engine's last callback used UTRACE_STOP, we do UTRACE_REPORT here to
-+ * ensure we stop before user mode.  If there were no callbacks made, it
-+ * will recompute @task->utrace_flags to avoid another false-positive.
-+ */
-+static void finish_report(struct task_struct *task, struct utrace *utrace,
-+			  struct utrace_report *report, bool will_not_stop)
-+{
-+	enum utrace_resume_action resume = report->action;
-+
-+	if (resume == UTRACE_STOP)
-+		resume = will_not_stop ? UTRACE_REPORT : UTRACE_RESUME;
-+
-+	if (resume < utrace->resume) {
-+		spin_lock(&utrace->lock);
-+		utrace->resume = resume;
-+		if (resume == UTRACE_INTERRUPT)
-+			set_tsk_thread_flag(task, TIF_SIGPENDING);
-+		else
-+			set_tsk_thread_flag(task, TIF_NOTIFY_RESUME);
-+		spin_unlock(&utrace->lock);
-+	}
-+
-+	finish_report_reset(task, utrace, report);
-+}
-+
-+static void finish_callback_report(struct task_struct *task,
-+				   struct utrace *utrace,
-+				   struct utrace_report *report,
-+				   struct utrace_engine *engine,
-+				   enum utrace_resume_action action)
-+{
-+	if (action == UTRACE_DETACH) {
-+		/*
-+		 * By holding the lock here, we make sure that
-+		 * utrace_barrier() (really get_utrace_lock()) sees the
-+		 * effect of this detach.  Otherwise utrace_barrier() could
-+		 * return 0 after this callback had returned UTRACE_DETACH.
-+		 * This way, a 0 return is an unambiguous indicator that any
-+		 * callback returning UTRACE_DETACH has indeed caused detach.
-+		 */
-+		spin_lock(&utrace->lock);
-+		engine->ops = &utrace_detached_ops;
-+		spin_unlock(&utrace->lock);
-+	}
-+
-+	/*
-+	 * If utrace_control() was used, treat that like UTRACE_DETACH here.
-+	 */
-+	if (engine->ops == &utrace_detached_ops) {
-+		report->detaches = true;
-+		return;
-+	}
-+
-+	if (action < report->action)
-+		report->action = action;
-+
-+	if (action != UTRACE_STOP) {
-+		if (action < report->resume_action)
-+			report->resume_action = action;
-+
-+		if (engine_wants_stop(engine)) {
-+			spin_lock(&utrace->lock);
-+			clear_engine_wants_stop(engine);
-+			spin_unlock(&utrace->lock);
-+		}
-+
-+		return;
-+	}
-+
-+	if (!engine_wants_stop(engine)) {
-+		spin_lock(&utrace->lock);
-+		/*
-+		 * If utrace_control() came in and detached us
-+		 * before we got the lock, we must not stop now.
-+		 */
-+		if (unlikely(engine->ops == &utrace_detached_ops))
-+			report->detaches = true;
-+		else
-+			mark_engine_wants_stop(task, engine);
-+		spin_unlock(&utrace->lock);
-+	}
-+}
-+
-+/*
-+ * Apply the return value of one engine callback to @report.
-+ * Returns true if @engine detached and should not get any more callbacks.
-+ */
-+static bool finish_callback(struct task_struct *task, struct utrace *utrace,
-+			    struct utrace_report *report,
-+			    struct utrace_engine *engine,
-+			    u32 ret)
-+{
-+	report->result = ret & ~UTRACE_RESUME_MASK;
-+	finish_callback_report(task, utrace, report, engine,
-+			       utrace_resume_action(ret));
-+
-+	/*
-+	 * Now that we have applied the effect of the return value,
-+	 * clear this so that utrace_barrier() can stop waiting.
-+	 * A subsequent utrace_control() can stop or resume @engine
-+	 * and know this was ordered after its callback's action.
-+	 *
-+	 * We don't need any barriers here because utrace_barrier()
-+	 * takes utrace->lock.  If we touched engine->flags above,
-+	 * the lock guaranteed this change was before utrace_barrier()
-+	 * examined utrace->reporting.
-+	 */
-+	utrace->reporting = NULL;
-+
-+	/*
-+	 * We've just done an engine callback.  These are allowed to sleep,
-+	 * though all well-behaved ones restrict that to blocking kalloc()
-+	 * or quickly-acquired mutex_lock() and the like.  This is a good
-+	 * place to make sure tracing engines don't introduce too much
-+	 * latency under voluntary preemption.
-+	 */
-+	might_sleep();
-+
-+	return engine->ops == &utrace_detached_ops;
-+}
-+
-+/*
-+ * Start the callbacks for @engine to consider @event (a bit mask).
-+ * This makes the report_quiesce() callback first.  If @engine wants
-+ * a specific callback for @event, we return the ops vector to use.
-+ * If not, we return NULL.  The return value from the ops->callback
-+ * function called should be passed to finish_callback().
-+ */
-+static const struct utrace_engine_ops *start_callback(
-+	struct utrace *utrace, struct utrace_report *report,
-+	struct utrace_engine *engine, struct task_struct *task,
-+	unsigned long event)
-+{
-+	const struct utrace_engine_ops *ops;
-+	unsigned long want;
-+
-+	/*
-+	 * This barrier ensures that we've set utrace->reporting before
-+	 * we examine engine->flags or engine->ops.  utrace_barrier()
-+	 * relies on this ordering to indicate that the effect of any
-+	 * utrace_control() and utrace_set_events() calls is in place
-+	 * by the time utrace->reporting can be seen to be NULL.
-+	 */
-+	utrace->reporting = engine;
-+	smp_mb();
-+
-+	/*
-+	 * This pairs with the barrier in mark_engine_detached().
-+	 * It makes sure that we never see the old ops vector with
-+	 * the new flags, in case the original vector had no report_quiesce.
-+	 */
-+	want = engine->flags;
-+	smp_rmb();
-+	ops = engine->ops;
-+
-+	if ((want & UTRACE_EVENT(QUIESCE)) || ops == &utrace_detached_ops) {
-+		if (finish_callback(task, utrace, report, engine,
-+				    (*ops->report_quiesce)(report->action,
-+							   engine, event)))
-+			return NULL;
-+
-+		if (!event) {
-+			/* We only got here to report QUIESCE */
-+			report->spurious = false;
-+			return NULL;
-+		}
-+
-+		/*
-+		 * finish_callback() reset utrace->reporting after the
-+		 * quiesce callback.  Now we set it again (as above)
-+		 * before re-examining engine->flags, which could have
-+		 * been changed synchronously by ->report_quiesce or
-+		 * asynchronously by utrace_control() or utrace_set_events().
-+		 */
-+		utrace->reporting = engine;
-+		smp_mb();
-+		want = engine->flags;
-+	}
-+
-+	if (want & ENGINE_STOP)
-+		report->action = UTRACE_STOP;
-+
-+	if (want & event) {
-+		report->spurious = false;
-+		return ops;
-+	}
-+
-+	utrace->reporting = NULL;
-+	return NULL;
-+}
-+
-+/*
-+ * Do a normal reporting pass for engines interested in @event.
-+ * @callback is the name of the member in the ops vector, and remaining
-+ * args are the extras it takes after the standard three args.
-+ */
-+#define REPORT_CALLBACKS(rev, task, utrace, report, event, callback, ...)     \
-+	do {								      \
-+		struct utrace_engine *engine;				      \
-+		const struct utrace_engine_ops *ops;			      \
-+		list_for_each_entry##rev(engine, &utrace->attached, entry) {  \
-+			ops = start_callback(utrace, report, engine, task,    \
-+					     event);			      \
-+			if (!ops)					      \
-+				continue;				      \
-+			finish_callback(task, utrace, report, engine,	      \
-+					(*ops->callback)(__VA_ARGS__));	      \
-+		}							      \
-+	} while (0)
-+#define REPORT(task, utrace, report, event, callback, ...)		      \
-+	do {								      \
-+		start_report(utrace);					      \
-+		REPORT_CALLBACKS(, task, utrace, report, event, callback,     \
-+				 (report)->action, engine, ## __VA_ARGS__);   \
-+		finish_report(task, utrace, report, true);		      \
-+	} while (0)
-+
-+/*
-+ * Called iff UTRACE_EVENT(EXEC) flag is set.
-+ */
-+void utrace_report_exec(struct linux_binfmt *fmt, struct linux_binprm *bprm,
-+			struct pt_regs *regs)
-+{
-+	struct task_struct *task = current;
-+	struct utrace *utrace = task_utrace_struct(task);
-+	INIT_REPORT(report);
-+
-+	REPORT(task, utrace, &report, UTRACE_EVENT(EXEC),
-+	       report_exec, fmt, bprm, regs);
-+}
-+
-+static u32 do_report_syscall_entry(struct pt_regs *regs,
-+				   struct task_struct *task,
-+				   struct utrace *utrace,
-+				   struct utrace_report *report,
-+				   u32 resume_report)
-+{
-+	start_report(utrace);
-+	REPORT_CALLBACKS(_reverse, task, utrace, report,
-+			 UTRACE_EVENT(SYSCALL_ENTRY), report_syscall_entry,
-+			 resume_report | report->result | report->action,
-+			 engine, regs);
-+	finish_report(task, utrace, report, false);
-+
-+	if (report->action != UTRACE_STOP)
-+		return 0;
-+
-+	utrace_stop(task, utrace, report->resume_action);
-+
-+	if (fatal_signal_pending(task)) {
-+		/*
-+		 * We are continuing despite UTRACE_STOP because of a
-+		 * SIGKILL.  Don't let the system call actually proceed.
-+		 */
-+		report->result = UTRACE_SYSCALL_ABORT;
-+	} else if (utrace->resume <= UTRACE_REPORT) {
-+		/*
-+		 * If we've been asked for another report after our stop,
-+		 * go back to report (and maybe stop) again before we run
-+		 * the system call.  The second (and later) reports are
-+		 * marked with the UTRACE_SYSCALL_RESUMED flag so that
-+		 * engines know this is a second report at the same
-+		 * entry.  This gives them the chance to examine the
-+		 * registers anew after they might have been changed
-+		 * while we were stopped.
-+		 */
-+		report->detaches = false;
-+		report->spurious = true;
-+		report->action = report->resume_action = UTRACE_RESUME;
-+		return UTRACE_SYSCALL_RESUMED;
-+	}
-+
-+	return 0;
-+}
-+
-+/*
-+ * Called iff UTRACE_EVENT(SYSCALL_ENTRY) flag is set.
-+ * Return true to prevent the system call.
-+ */
-+bool utrace_report_syscall_entry(struct pt_regs *regs)
-+{
-+	struct task_struct *task = current;
-+	struct utrace *utrace = task_utrace_struct(task);
-+	INIT_REPORT(report);
-+	u32 resume_report = 0;
-+
-+	do {
-+		resume_report = do_report_syscall_entry(regs, task, utrace,
-+							&report, resume_report);
-+	} while (resume_report);
-+
-+	return utrace_syscall_action(report.result) == UTRACE_SYSCALL_ABORT;
-+}
-+
-+/*
-+ * Called iff UTRACE_EVENT(SYSCALL_EXIT) flag is set.
-+ */
-+void utrace_report_syscall_exit(struct pt_regs *regs)
-+{
-+	struct task_struct *task = current;
-+	struct utrace *utrace = task_utrace_struct(task);
-+	INIT_REPORT(report);
-+
-+	REPORT(task, utrace, &report, UTRACE_EVENT(SYSCALL_EXIT),
-+	       report_syscall_exit, regs);
-+}
-+
-+/*
-+ * Called iff UTRACE_EVENT(CLONE) flag is set.
-+ * This notification call blocks the wake_up_new_task call on the child.
-+ * So we must not quiesce here.  tracehook_report_clone_complete will do
-+ * a quiescence check momentarily.
-+ */
-+void utrace_report_clone(unsigned long clone_flags, struct task_struct *child)
-+{
-+	struct task_struct *task = current;
-+	struct utrace *utrace = task_utrace_struct(task);
-+	INIT_REPORT(report);
-+
-+	/*
-+	 * We don't use the REPORT() macro here, because we need
-+	 * to clear utrace->cloning before finish_report().
-+	 * After finish_report(), utrace can be a stale pointer
-+	 * in cases when report.action is still UTRACE_RESUME.
-+	 */
-+	start_report(utrace);
-+	utrace->cloning = child;
-+
-+	REPORT_CALLBACKS(, task, utrace, &report,
-+			 UTRACE_EVENT(CLONE), report_clone,
-+			 report.action, engine, clone_flags, child);
-+
-+	utrace->cloning = NULL;
-+	finish_report(task, utrace, &report, !(clone_flags & CLONE_VFORK));
-+
-+	/*
-+	 * For a vfork, we will go into an uninterruptible block waiting
-+	 * for the child.  We need UTRACE_STOP to happen before this, not
-+	 * after.  For CLONE_VFORK, utrace_finish_vfork() will be called.
-+	 */
-+	if (report.action == UTRACE_STOP && (clone_flags & CLONE_VFORK)) {
-+		spin_lock(&utrace->lock);
-+		utrace->vfork_stop = 1;
-+		spin_unlock(&utrace->lock);
-+	}
-+}
-+
-+/*
-+ * We're called after utrace_report_clone() for a CLONE_VFORK.
-+ * If UTRACE_STOP was left from the clone report, we stop here.
-+ * After this, we'll enter the uninterruptible wait_for_completion()
-+ * waiting for the child.
-+ */
-+void utrace_finish_vfork(struct task_struct *task)
-+{
-+	struct utrace *utrace = task_utrace_struct(task);
-+
-+	if (utrace->vfork_stop) {
-+		spin_lock(&utrace->lock);
-+		utrace->vfork_stop = 0;
-+		spin_unlock(&utrace->lock);
-+		utrace_stop(task, utrace, UTRACE_RESUME); /* XXX */
-+	}
-+}
-+
-+/*
-+ * Called iff UTRACE_EVENT(JCTL) flag is set.
-+ *
-+ * Called with siglock held.
-+ */
-+void utrace_report_jctl(int notify, int what)
-+{
-+	struct task_struct *task = current;
-+	struct utrace *utrace = task_utrace_struct(task);
-+	INIT_REPORT(report);
-+
-+	spin_unlock_irq(&task->sighand->siglock);
-+
-+	REPORT(task, utrace, &report, UTRACE_EVENT(JCTL),
-+	       report_jctl, what, notify);
-+
-+	spin_lock_irq(&task->sighand->siglock);
-+}
-+
-+/*
-+ * Called iff UTRACE_EVENT(EXIT) flag is set.
-+ */
-+void utrace_report_exit(long *exit_code)
-+{
-+	struct task_struct *task = current;
-+	struct utrace *utrace = task_utrace_struct(task);
-+	INIT_REPORT(report);
-+	long orig_code = *exit_code;
-+
-+	REPORT(task, utrace, &report, UTRACE_EVENT(EXIT),
-+	       report_exit, orig_code, exit_code);
-+
-+	if (report.action == UTRACE_STOP)
-+		utrace_stop(task, utrace, report.resume_action);
-+}
-+
-+/*
-+ * Called iff UTRACE_EVENT(DEATH) or UTRACE_EVENT(QUIESCE) flag is set.
-+ *
-+ * It is always possible that we are racing with utrace_release_task here.
-+ * For this reason, utrace_release_task checks for the event bits that get
-+ * us here, and delays its cleanup for us to do.
-+ */
-+void utrace_report_death(struct task_struct *task, struct utrace *utrace,
-+			 bool group_dead, int signal)
-+{
-+	INIT_REPORT(report);
-+
-+	BUG_ON(!task->exit_state);
-+
-+	/*
-+	 * We are presently considered "quiescent"--which is accurate
-+	 * inasmuch as we won't run any more user instructions ever again.
-+	 * But for utrace_control and utrace_set_events to be robust, they
-+	 * must be sure whether or not we will run any more callbacks.  If
-+	 * a call comes in before we do, taking the lock here synchronizes
-+	 * us so we don't run any callbacks just disabled.  Calls that come
-+	 * in while we're running the callbacks will see the exit.death
-+	 * flag and know that we are not yet fully quiescent for purposes
-+	 * of detach bookkeeping.
-+	 */
-+	spin_lock(&utrace->lock);
-+	BUG_ON(utrace->death);
-+	utrace->death = 1;
-+	utrace->resume = UTRACE_RESUME;
-+	splice_attaching(utrace);
-+	spin_unlock(&utrace->lock);
-+
-+	REPORT_CALLBACKS(, task, utrace, &report, UTRACE_EVENT(DEATH),
-+			 report_death, engine, group_dead, signal);
-+
-+	utrace_maybe_reap(task, utrace, false);
-+}
-+
-+/*
-+ * Finish the last reporting pass before returning to user mode.
-+ */
-+static void finish_resume_report(struct task_struct *task,
-+				 struct utrace *utrace,
-+				 struct utrace_report *report)
-+{
-+	finish_report_reset(task, utrace, report);
-+
-+	switch (report->action) {
-+	case UTRACE_STOP:
-+		utrace_stop(task, utrace, report->resume_action);
-+		break;
-+
-+	case UTRACE_INTERRUPT:
-+		if (!signal_pending(task))
-+			set_tsk_thread_flag(task, TIF_SIGPENDING);
-+		break;
-+
-+	case UTRACE_BLOCKSTEP:
-+		if (likely(arch_has_block_step())) {
-+			user_enable_block_step(task);
-+			break;
-+		}
-+
-+		/*
-+		 * This means some callback is to blame for failing
-+		 * to check arch_has_block_step() itself.  Warn and
-+		 * then fall through to treat it as SINGLESTEP.
-+		 */
-+		WARN(1, "UTRACE_BLOCKSTEP when !arch_has_block_step()");
-+
-+	case UTRACE_SINGLESTEP:
-+		if (likely(arch_has_single_step())) {
-+			user_enable_single_step(task);
-+		} else {
-+			/*
-+			 * This means some callback is to blame for failing
-+			 * to check arch_has_single_step() itself.  Spew
-+			 * about it so the loser will fix his module.
-+			 */
-+			WARN(1,
-+			     "UTRACE_SINGLESTEP when !arch_has_single_step()");
-+		}
-+		break;
-+
-+	case UTRACE_REPORT:
-+	case UTRACE_RESUME:
-+	default:
-+		user_disable_single_step(task);
-+		break;
-+	}
-+}
-+
-+/*
-+ * This is called when TIF_NOTIFY_RESUME had been set (and is now clear).
-+ * We are close to user mode, and this is the place to report or stop.
-+ * When we return, we're going to user mode or into the signals code.
-+ */
-+void utrace_resume(struct task_struct *task, struct pt_regs *regs)
-+{
-+	struct utrace *utrace = task_utrace_struct(task);
-+	INIT_REPORT(report);
-+	struct utrace_engine *engine;
-+
-+	/*
-+	 * Some machines get here with interrupts disabled.  The same arch
-+	 * code path leads to calling into get_signal_to_deliver(), which
-+	 * implicitly reenables them by virtue of spin_unlock_irq.
-+	 */
-+	local_irq_enable();
-+
-+	/*
-+	 * If this flag is still set it's because there was a signal
-+	 * handler setup done but no report_signal following it.  Clear
-+	 * the flag before we get to user so it doesn't confuse us later.
-+	 */
-+	if (unlikely(utrace->signal_handler)) {
-+		spin_lock(&utrace->lock);
-+		utrace->signal_handler = 0;
-+		spin_unlock(&utrace->lock);
-+	}
-+
-+	/*
-+	 * Update our bookkeeping even if there are no callbacks made here.
-+	 */
-+	report.action = start_report(utrace);
-+
-+	switch (report.action) {
-+	case UTRACE_RESUME:
-+		/*
-+		 * Anything we might have done was already handled by
-+		 * utrace_get_signal(), or this is an entirely spurious
-+		 * call.  (The arch might use TIF_NOTIFY_RESUME for other
-+		 * purposes as well as calling us.)
-+		 */
-+		return;
-+	case UTRACE_REPORT:
-+		if (unlikely(!(task->utrace_flags & UTRACE_EVENT(QUIESCE))))
-+			break;
-+		/*
-+		 * Do a simple reporting pass, with no specific
-+		 * callback after report_quiesce.
-+		 */
-+		report.action = UTRACE_RESUME;
-+		list_for_each_entry(engine, &utrace->attached, entry)
-+			start_callback(utrace, &report, engine, task, 0);
-+		break;
-+	default:
-+		/*
-+		 * Even if this report was truly spurious, there is no need
-+		 * for utrace_reset() now.  TIF_NOTIFY_RESUME was already
-+		 * cleared--it doesn't stay spuriously set.
-+		 */
-+		report.spurious = false;
-+		break;
-+	}
-+
-+	/*
-+	 * Finish the report and either stop or get ready to resume.
-+	 * If utrace->resume was not UTRACE_REPORT, this applies its
-+	 * effect now (i.e. step or interrupt).
-+	 */
-+	finish_resume_report(task, utrace, &report);
-+}
-+
-+/*
-+ * Return true if current has forced signal_pending().
-+ *
-+ * This is called only when current->utrace_flags is nonzero, so we know
-+ * that current->utrace must be set.  It's not inlined in tracehook.h
-+ * just so that struct utrace can stay opaque outside this file.
-+ */
-+bool utrace_interrupt_pending(void)
-+{
-+	return task_utrace_struct(current)->resume == UTRACE_INTERRUPT;
-+}
-+
-+/*
-+ * Take the siglock and push @info back on our queue.
-+ * Returns with @task->sighand->siglock held.
-+ */
-+static void push_back_signal(struct task_struct *task, siginfo_t *info)
-+	__acquires(task->sighand->siglock)
-+{
-+	struct sigqueue *q;
-+
-+	if (unlikely(!info->si_signo)) { /* Oh, a wise guy! */
-+		spin_lock_irq(&task->sighand->siglock);
-+		return;
-+	}
-+
-+	q = sigqueue_alloc();
-+	if (likely(q)) {
-+		q->flags = 0;
-+		copy_siginfo(&q->info, info);
-+	}
-+
-+	spin_lock_irq(&task->sighand->siglock);
-+
-+	sigaddset(&task->pending.signal, info->si_signo);
-+	if (likely(q))
-+		list_add(&q->list, &task->pending.list);
-+
-+	set_tsk_thread_flag(task, TIF_SIGPENDING);
-+}
-+
-+/*
-+ * This is the hook from the signals code, called with the siglock held.
-+ * Here is the ideal place to stop.  We also dequeue and intercept signals.
-+ */
-+int utrace_get_signal(struct task_struct *task, struct pt_regs *regs,
-+		      siginfo_t *info, struct k_sigaction *return_ka)
-+	__releases(task->sighand->siglock)
-+	__acquires(task->sighand->siglock)
-+{
-+	struct utrace *utrace;
-+	struct k_sigaction *ka;
-+	INIT_REPORT(report);
-+	struct utrace_engine *engine;
-+	const struct utrace_engine_ops *ops;
-+	unsigned long event, want;
-+	u32 ret;
-+	int signr;
-+
-+	utrace = task_utrace_struct(task);
-+	if (utrace->resume < UTRACE_RESUME ||
-+	    utrace->pending_attach || utrace->signal_handler) {
-+		enum utrace_resume_action resume;
-+
-+		/*
-+		 * We've been asked for an explicit report before we
-+		 * even check for pending signals.
-+		 */
-+
-+		spin_unlock_irq(&task->sighand->siglock);
-+
-+		spin_lock(&utrace->lock);
-+
-+		splice_attaching(utrace);
-+
-+		report.result = utrace->signal_handler ?
-+			UTRACE_SIGNAL_HANDLER : UTRACE_SIGNAL_REPORT;
-+		utrace->signal_handler = 0;
-+
-+		resume = utrace->resume;
-+		utrace->resume = UTRACE_RESUME;
-+
-+		spin_unlock(&utrace->lock);
-+
-+		/*
-+		 * Make sure signal_pending() only returns true
-+		 * if there are real signals pending.
-+		 */
-+		if (signal_pending(task)) {
-+			spin_lock_irq(&task->sighand->siglock);
-+			recalc_sigpending();
-+			spin_unlock_irq(&task->sighand->siglock);
-+		}
-+
-+		if (resume > UTRACE_REPORT) {
-+			/*
-+			 * We only got here to process utrace->resume.
-+			 * Despite no callbacks, this report is not spurious.
-+			 */
-+			report.action = resume;
-+			report.spurious = false;
-+			finish_resume_report(task, utrace, &report);
-+			return -1;
-+		} else if (!(task->utrace_flags & UTRACE_EVENT(QUIESCE))) {
-+			/*
-+			 * We only got here to clear utrace->signal_handler.
-+			 */
-+			return -1;
-+		}
-+
-+		/*
-+		 * Do a reporting pass for no signal, just for EVENT(QUIESCE).
-+		 * The engine callbacks can fill in *info and *return_ka.
-+		 * We'll pass NULL for the @orig_ka argument to indicate
-+		 * that there was no original signal.
-+		 */
-+		event = 0;
-+		ka = NULL;
-+		memset(return_ka, 0, sizeof *return_ka);
-+	} else if (!(task->utrace_flags & UTRACE_EVENT_SIGNAL_ALL) ||
-+		   unlikely(task->signal->group_stop_count)) {
-+		/*
-+		 * If no engine is interested in intercepting signals or
-+		 * we must stop, let the caller just dequeue them normally
-+		 * or participate in group-stop.
-+		 */
-+		return 0;
-+	} else {
-+		/*
-+		 * Steal the next signal so we can let tracing engines
-+		 * examine it.  From the signal number and sigaction,
-+		 * determine what normal delivery would do.  If no
-+		 * engine perturbs it, we'll do that by returning the
-+		 * signal number after setting *return_ka.
-+		 */
-+		signr = dequeue_signal(task, &task->blocked, info);
-+		if (signr == 0)
-+			return signr;
-+		BUG_ON(signr != info->si_signo);
-+
-+		ka = &task->sighand->action[signr - 1];
-+		*return_ka = *ka;
-+
-+		/*
-+		 * We are never allowed to interfere with SIGKILL.
-+		 * Just punt after filling in *return_ka for our caller.
-+		 */
-+		if (signr == SIGKILL)
-+			return signr;
-+
-+		if (ka->sa.sa_handler == SIG_IGN) {
-+			event = UTRACE_EVENT(SIGNAL_IGN);
-+			report.result = UTRACE_SIGNAL_IGN;
-+		} else if (ka->sa.sa_handler != SIG_DFL) {
-+			event = UTRACE_EVENT(SIGNAL);
-+			report.result = UTRACE_SIGNAL_DELIVER;
-+		} else if (sig_kernel_coredump(signr)) {
-+			event = UTRACE_EVENT(SIGNAL_CORE);
-+			report.result = UTRACE_SIGNAL_CORE;
-+		} else if (sig_kernel_ignore(signr)) {
-+			event = UTRACE_EVENT(SIGNAL_IGN);
-+			report.result = UTRACE_SIGNAL_IGN;
-+		} else if (signr == SIGSTOP) {
-+			event = UTRACE_EVENT(SIGNAL_STOP);
-+			report.result = UTRACE_SIGNAL_STOP;
-+		} else if (sig_kernel_stop(signr)) {
-+			event = UTRACE_EVENT(SIGNAL_STOP);
-+			report.result = UTRACE_SIGNAL_TSTP;
-+		} else {
-+			event = UTRACE_EVENT(SIGNAL_TERM);
-+			report.result = UTRACE_SIGNAL_TERM;
-+		}
-+
-+		/*
-+		 * Now that we know what event type this signal is, we
-+		 * can short-circuit if no engines care about those.
-+		 */
-+		if ((task->utrace_flags & (event | UTRACE_EVENT(QUIESCE))) == 0)
-+			return signr;
-+
-+		/*
-+		 * We have some interested engines, so tell them about
-+		 * the signal and let them change its disposition.
-+		 */
-+		spin_unlock_irq(&task->sighand->siglock);
-+	}
-+
-+	/*
-+	 * This reporting pass chooses what signal disposition we'll act on.
-+	 */
-+	list_for_each_entry(engine, &utrace->attached, entry) {
-+		/*
-+		 * See start_callback() comment about this barrier.
-+		 */
-+		utrace->reporting = engine;
-+		smp_mb();
-+
-+		/*
-+		 * This pairs with the barrier in mark_engine_detached(),
-+		 * see start_callback() comments.
-+		 */
-+		want = engine->flags;
-+		smp_rmb();
-+		ops = engine->ops;
-+
-+		if ((want & (event | UTRACE_EVENT(QUIESCE))) == 0) {
-+			utrace->reporting = NULL;
-+			continue;
-+		}
-+
-+		if (ops->report_signal)
-+			ret = (*ops->report_signal)(
-+				report.result | report.action, engine,
-+				regs, info, ka, return_ka);
-+		else
-+			ret = (report.result | (*ops->report_quiesce)(
-+				       report.action, engine, event));
-+
-+		/*
-+		 * Avoid a tight loop reporting again and again if some
-+		 * engine is too stupid.
-+		 */
-+		switch (utrace_resume_action(ret)) {
-+		default:
-+			break;
-+		case UTRACE_INTERRUPT:
-+		case UTRACE_REPORT:
-+			ret = (ret & ~UTRACE_RESUME_MASK) | UTRACE_RESUME;
-+			break;
-+		}
-+
-+		finish_callback(task, utrace, &report, engine, ret);
-+	}
-+
-+	/*
-+	 * We express the chosen action to the signals code in terms
-+	 * of a representative signal whose default action does it.
-+	 * Our caller uses our return value (signr) to decide what to
-+	 * do, but uses info->si_signo as the signal number to report.
-+	 */
-+	switch (utrace_signal_action(report.result)) {
-+	case UTRACE_SIGNAL_TERM:
-+		signr = SIGTERM;
-+		break;
-+
-+	case UTRACE_SIGNAL_CORE:
-+		signr = SIGQUIT;
-+		break;
-+
-+	case UTRACE_SIGNAL_STOP:
-+		signr = SIGSTOP;
-+		break;
-+
-+	case UTRACE_SIGNAL_TSTP:
-+		signr = SIGTSTP;
-+		break;
-+
-+	case UTRACE_SIGNAL_DELIVER:
-+		signr = info->si_signo;
-+
-+		if (return_ka->sa.sa_handler == SIG_DFL) {
-+			/*
-+			 * We'll do signr's normal default action.
-+			 * For ignore, we'll fall through below.
-+			 * For stop/death, break locks and returns it.
-+			 */
-+			if (likely(signr) && !sig_kernel_ignore(signr))
-+				break;
-+		} else if (return_ka->sa.sa_handler != SIG_IGN &&
-+			   likely(signr)) {
-+			/*
-+			 * Complete the bookkeeping after the report.
-+			 * The handler will run.  If an engine wanted to
-+			 * stop or step, then make sure we do another
-+			 * report after signal handler setup.
-+			 */
-+			if (report.action != UTRACE_RESUME)
-+				report.action = UTRACE_INTERRUPT;
-+			finish_report(task, utrace, &report, true);
-+
-+			if (unlikely(report.result & UTRACE_SIGNAL_HOLD))
-+				push_back_signal(task, info);
-+			else
-+				spin_lock_irq(&task->sighand->siglock);
-+
-+			/*
-+			 * We do the SA_ONESHOT work here since the
-+			 * normal path will only touch *return_ka now.
-+			 */
-+			if (unlikely(return_ka->sa.sa_flags & SA_ONESHOT)) {
-+				return_ka->sa.sa_flags &= ~SA_ONESHOT;
-+				if (likely(valid_signal(signr))) {
-+					ka = &task->sighand->action[signr - 1];
-+					ka->sa.sa_handler = SIG_DFL;
-+				}
-+			}
-+
-+			return signr;
-+		}
-+
-+		/* Fall through for an ignored signal.  */
-+
-+	case UTRACE_SIGNAL_IGN:
-+	case UTRACE_SIGNAL_REPORT:
-+	default:
-+		/*
-+		 * If the signal is being ignored, then we are on the way
-+		 * directly back to user mode.  We can stop here, or step,
-+		 * as in utrace_resume(), above.  After we've dealt with that,
-+		 * our caller will relock and come back through here.
-+		 */
-+		finish_resume_report(task, utrace, &report);
-+
-+		if (unlikely(fatal_signal_pending(task))) {
-+			/*
-+			 * The only reason we woke up now was because of a
-+			 * SIGKILL.  Don't do normal dequeuing in case it
-+			 * might get a signal other than SIGKILL.  That would
-+			 * perturb the death state so it might differ from
-+			 * what the debugger would have allowed to happen.
-+			 * Instead, pluck out just the SIGKILL to be sure
-+			 * we'll die immediately with nothing else different
-+			 * from the quiescent state the debugger wanted us in.
-+			 */
-+			sigset_t sigkill_only;
-+			siginitsetinv(&sigkill_only, sigmask(SIGKILL));
-+			spin_lock_irq(&task->sighand->siglock);
-+			signr = dequeue_signal(task, &sigkill_only, info);
-+			BUG_ON(signr != SIGKILL);
-+			*return_ka = task->sighand->action[SIGKILL - 1];
-+			return signr;
-+		}
-+
-+		if (unlikely(report.result & UTRACE_SIGNAL_HOLD)) {
-+			push_back_signal(task, info);
-+			spin_unlock_irq(&task->sighand->siglock);
-+		}
-+
-+		return -1;
-+	}
-+
-+	/*
-+	 * Complete the bookkeeping after the report.
-+	 * This sets utrace->resume if UTRACE_STOP was used.
-+	 */
-+	finish_report(task, utrace, &report, true);
-+
-+	return_ka->sa.sa_handler = SIG_DFL;
-+
-+	/*
-+	 * If this signal is fatal, si_signo gets through as exit_code.
-+	 * We can't allow a completely bogus value there or else core
-+	 * kernel code can freak out.  (If an engine wants to control
-+	 * the exit_code value exactly, it can do so in report_exit.)
-+	 * We'll produce a big complaint in dmesg, but won't crash.
-+	 * That's nicer for debugging your utrace engine.
-+	 */
-+	if (unlikely(info->si_signo & 0x80)) {
-+		WARN(1, "utrace engine left bogus si_signo value!");
-+		info->si_signo = SIGTRAP;
-+	}
-+
-+	if (unlikely(report.result & UTRACE_SIGNAL_HOLD))
-+		push_back_signal(task, info);
-+	else
-+		spin_lock_irq(&task->sighand->siglock);
-+
-+	if (sig_kernel_stop(signr))
-+		task->signal->flags |= SIGNAL_STOP_DEQUEUED;
-+
-+	return signr;
-+}
-+
-+/*
-+ * This gets called after a signal handler has been set up.
-+ * We set a flag so the next report knows it happened.
-+ * If we're already stepping, make sure we do a report_signal.
-+ * If not, make sure we get into utrace_resume() where we can
-+ * clear the signal_handler flag before resuming.
-+ */
-+void utrace_signal_handler(struct task_struct *task, int stepping)
-+{
-+	struct utrace *utrace = task_utrace_struct(task);
-+
-+	spin_lock(&utrace->lock);
-+
-+	utrace->signal_handler = 1;
-+	if (utrace->resume > UTRACE_INTERRUPT) {
-+		if (stepping) {
-+			utrace->resume = UTRACE_INTERRUPT;
-+			set_tsk_thread_flag(task, TIF_SIGPENDING);
-+		} else if (utrace->resume == UTRACE_RESUME) {
-+			set_tsk_thread_flag(task, TIF_NOTIFY_RESUME);
-+		}
-+	}
-+
-+	spin_unlock(&utrace->lock);
-+}
-+
-+/**
-+ * utrace_prepare_examine - prepare to examine thread state
-+ * @target:		thread of interest, a &struct task_struct pointer
-+ * @engine:		engine pointer returned by utrace_attach_task()
-+ * @exam:		temporary state, a &struct utrace_examiner pointer
-+ *
-+ * This call prepares to safely examine the thread @target using
-+ * &struct user_regset calls, or direct access to thread-synchronous fields.
-+ *
-+ * When @target is current, this call is superfluous.  When @target is
-+ * another thread, it must be held stopped via %UTRACE_STOP by @engine.
-+ *
-+ * This call may block the caller until @target stays stopped, so it must
-+ * be called only after the caller is sure @target is about to unschedule.
-+ * This means a zero return from a utrace_control() call on @engine giving
-+ * %UTRACE_STOP, or a report_quiesce() or report_signal() callback to
-+ * @engine that used %UTRACE_STOP in its return value.
-+ *
-+ * Returns -%ESRCH if @target is dead or -%EINVAL if %UTRACE_STOP was
-+ * not used.  If @target has started running again despite %UTRACE_STOP
-+ * (for %SIGKILL or a spurious wakeup), this call returns -%EAGAIN.
-+ *
-+ * When this call returns zero, it's safe to use &struct user_regset
-+ * calls and task_user_regset_view() on @target and to examine some of
-+ * its fields directly.  When the examination is complete, a
-+ * utrace_finish_examine() call must follow to check whether it was
-+ * completed safely.
-+ */
-+int utrace_prepare_examine(struct task_struct *target,
-+			   struct utrace_engine *engine,
-+			   struct utrace_examiner *exam)
-+{
-+	int ret = 0;
-+
-+	if (unlikely(target == current))
-+		return 0;
-+
-+	rcu_read_lock();
-+	if (unlikely(!engine_wants_stop(engine)))
-+		ret = -EINVAL;
-+	else if (unlikely(target->exit_state))
-+		ret = -ESRCH;
-+	else {
-+		exam->state = target->state;
-+		if (unlikely(exam->state == TASK_RUNNING))
-+			ret = -EAGAIN;
-+		else
-+			get_task_struct(target);
-+	}
-+	rcu_read_unlock();
-+
-+	if (likely(!ret)) {
-+		exam->ncsw = wait_task_inactive(target, exam->state);
-+		put_task_struct(target);
-+		if (unlikely(!exam->ncsw))
-+			ret = -EAGAIN;
-+	}
-+
-+	return ret;
-+}
-+EXPORT_SYMBOL_GPL(utrace_prepare_examine);
-+
-+/**
-+ * utrace_finish_examine - complete an examination of thread state
-+ * @target:		thread of interest, a &struct task_struct pointer
-+ * @engine:		engine pointer returned by utrace_attach_task()
-+ * @exam:		pointer passed to utrace_prepare_examine() call
-+ *
-+ * This call completes an examination on the thread @target begun by a
-+ * paired utrace_prepare_examine() call with the same arguments that
-+ * returned success (zero).
-+ *
-+ * When @target is current, this call is superfluous.  When @target is
-+ * another thread, this returns zero if @target has remained unscheduled
-+ * since the paired utrace_prepare_examine() call returned zero.
-+ *
-+ * When this returns an error, any examination done since the paired
-+ * utrace_prepare_examine() call is unreliable and the data extracted
-+ * should be discarded.  The error is -%EINVAL if @engine is not
-+ * keeping @target stopped, or -%EAGAIN if @target woke up unexpectedly.
-+ */
-+int utrace_finish_examine(struct task_struct *target,
-+			  struct utrace_engine *engine,
-+			  struct utrace_examiner *exam)
-+{
-+	int ret = 0;
-+
-+	if (unlikely(target == current))
-+		return 0;
-+
-+	rcu_read_lock();
-+	if (unlikely(!engine_wants_stop(engine)))
-+		ret = -EINVAL;
-+	else if (unlikely(target->state != exam->state))
-+		ret = -EAGAIN;
-+	else
-+		get_task_struct(target);
-+	rcu_read_unlock();
-+
-+	if (likely(!ret)) {
-+		unsigned long ncsw = wait_task_inactive(target, exam->state);
-+		if (unlikely(ncsw != exam->ncsw))
-+			ret = -EAGAIN;
-+		put_task_struct(target);
-+	}
-+
-+	return ret;
-+}
-+EXPORT_SYMBOL_GPL(utrace_finish_examine);
-+
-+/*
-+ * This is declared in linux/regset.h and defined in machine-dependent
-+ * code.  We put the export here to ensure no machine forgets it.
-+ */
-+EXPORT_SYMBOL_GPL(task_user_regset_view);
-+
-+/*
-+ * Called with rcu_read_lock() held.
-+ */
-+void task_utrace_proc_status(struct seq_file *m, struct task_struct *p)
-+{
-+	seq_printf(m, "Utrace:\t%lx\n", p->utrace_flags);
-+}