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authorDave Jones <davej@redhat.com>2011-05-09 16:41:28 -0400
committerDave Jones <davej@redhat.com>2011-05-09 16:41:28 -0400
commit57671e4ed5e8ec1546c5b38222cee66d5ea32dee (patch)
tree6ca2b46de7b5d4092ea70f23b28a354c7720b4a6 /linux-2.6-utrace.patch
parent9de65275ff9c115edcf583ed209f5d5c50fbbf1d (diff)
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adios utrace.
Diffstat (limited to 'linux-2.6-utrace.patch')
-rw-r--r--linux-2.6-utrace.patch4166
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);
-+}