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Diffstat (limited to 'linux-2.6-utrace.patch')
| -rw-r--r-- | linux-2.6-utrace.patch | 4166 |
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><linux/utrace.h></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><linux/utrace.h></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><linux/regset.h></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><linux/ptrace.h></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><asm/syscall.h></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><linux/tracehook.h></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><asm/ptrace.h></filename></title> -+ -+<para> -+ An arch defines these in <filename><asm/ptrace.h></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><asm/syscall.h></filename></title> -+ -+ <para> -+ An arch provides <filename><asm/syscall.h></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><linux/tracehook.h></filename></title> -+ -+ <para> -+ An arch must define <constant>TIF_NOTIFY_RESUME</constant> -+ and <constant>TIF_SYSCALL_TRACE</constant> -+ in its <filename><asm/thread_info.h></filename>. -+ The arch code must call the following functions, all declared -+ in <filename><linux/tracehook.h></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); -+} |