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Roland McGrath88ac2922008-07-25 19:45:43 -07001/*
2 * Tracing hooks
3 *
4 * Copyright (C) 2008 Red Hat, Inc. All rights reserved.
5 *
6 * This copyrighted material is made available to anyone wishing to use,
7 * modify, copy, or redistribute it subject to the terms and conditions
8 * of the GNU General Public License v.2.
9 *
10 * This file defines hook entry points called by core code where
11 * user tracing/debugging support might need to do something. These
12 * entry points are called tracehook_*(). Each hook declared below
13 * has a detailed kerneldoc comment giving the context (locking et
14 * al) from which it is called, and the meaning of its return value.
15 *
16 * Each function here typically has only one call site, so it is ok
17 * to have some nontrivial tracehook_*() inlines. In all cases, the
18 * fast path when no tracing is enabled should be very short.
19 *
20 * The purpose of this file and the tracehook_* layer is to consolidate
21 * the interface that the kernel core and arch code uses to enable any
22 * user debugging or tracing facility (such as ptrace). The interfaces
23 * here are carefully documented so that maintainers of core and arch
24 * code do not need to think about the implementation details of the
25 * tracing facilities. Likewise, maintainers of the tracing code do not
26 * need to understand all the calling core or arch code in detail, just
27 * documented circumstances of each call, such as locking conditions.
28 *
29 * If the calling core code changes so that locking is different, then
30 * it is ok to change the interface documented here. The maintainer of
31 * core code changing should notify the maintainers of the tracing code
32 * that they need to work out the change.
33 *
34 * Some tracehook_*() inlines take arguments that the current tracing
35 * implementations might not necessarily use. These function signatures
36 * are chosen to pass in all the information that is on hand in the
37 * caller and might conceivably be relevant to a tracer, so that the
38 * core code won't have to be updated when tracing adds more features.
39 * If a call site changes so that some of those parameters are no longer
40 * already on hand without extra work, then the tracehook_* interface
41 * can change so there is no make-work burden on the core code. The
42 * maintainer of core code changing should notify the maintainers of the
43 * tracing code that they need to work out the change.
44 */
45
46#ifndef _LINUX_TRACEHOOK_H
47#define _LINUX_TRACEHOOK_H 1
48
49#include <linux/sched.h>
50#include <linux/ptrace.h>
Roland McGrath6341c392008-07-25 19:45:44 -070051#include <linux/security.h>
52struct linux_binprm;
53
54/**
Roland McGrathfa8e26c2008-07-25 19:45:50 -070055 * tracehook_expect_breakpoints - guess if task memory might be touched
56 * @task: current task, making a new mapping
57 *
58 * Return nonzero if @task is expected to want breakpoint insertion in
59 * its memory at some point. A zero return is no guarantee it won't
60 * be done, but this is a hint that it's known to be likely.
61 *
62 * May be called with @task->mm->mmap_sem held for writing.
63 */
64static inline int tracehook_expect_breakpoints(struct task_struct *task)
65{
66 return (task_ptrace(task) & PT_PTRACED) != 0;
67}
68
Roland McGrath283d7552008-07-25 19:45:52 -070069/*
70 * ptrace report for syscall entry and exit looks identical.
71 */
72static inline void ptrace_report_syscall(struct pt_regs *regs)
73{
74 int ptrace = task_ptrace(current);
75
76 if (!(ptrace & PT_PTRACED))
77 return;
78
79 ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
80
81 /*
82 * this isn't the same as continuing with a signal, but it will do
83 * for normal use. strace only continues with a signal if the
84 * stopping signal is not SIGTRAP. -brl
85 */
86 if (current->exit_code) {
87 send_sig(current->exit_code, current, 1);
88 current->exit_code = 0;
89 }
90}
91
92/**
93 * tracehook_report_syscall_entry - task is about to attempt a system call
94 * @regs: user register state of current task
95 *
96 * This will be called if %TIF_SYSCALL_TRACE has been set, when the
97 * current task has just entered the kernel for a system call.
98 * Full user register state is available here. Changing the values
99 * in @regs can affect the system call number and arguments to be tried.
100 * It is safe to block here, preventing the system call from beginning.
101 *
102 * Returns zero normally, or nonzero if the calling arch code should abort
103 * the system call. That must prevent normal entry so no system call is
104 * made. If @task ever returns to user mode after this, its register state
105 * is unspecified, but should be something harmless like an %ENOSYS error
Roland McGrath828c3652008-07-25 19:45:57 -0700106 * return. It should preserve enough information so that syscall_rollback()
107 * can work (see asm-generic/syscall.h).
Roland McGrath283d7552008-07-25 19:45:52 -0700108 *
109 * Called without locks, just after entering kernel mode.
110 */
111static inline __must_check int tracehook_report_syscall_entry(
112 struct pt_regs *regs)
113{
114 ptrace_report_syscall(regs);
115 return 0;
116}
117
118/**
119 * tracehook_report_syscall_exit - task has just finished a system call
120 * @regs: user register state of current task
121 * @step: nonzero if simulating single-step or block-step
122 *
123 * This will be called if %TIF_SYSCALL_TRACE has been set, when the
124 * current task has just finished an attempted system call. Full
125 * user register state is available here. It is safe to block here,
126 * preventing signals from being processed.
127 *
128 * If @step is nonzero, this report is also in lieu of the normal
129 * trap that would follow the system call instruction because
130 * user_enable_block_step() or user_enable_single_step() was used.
131 * In this case, %TIF_SYSCALL_TRACE might not be set.
132 *
133 * Called without locks, just before checking for pending signals.
134 */
135static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
136{
137 ptrace_report_syscall(regs);
138}
139
Roland McGrathfa8e26c2008-07-25 19:45:50 -0700140/**
Roland McGrath6341c392008-07-25 19:45:44 -0700141 * tracehook_unsafe_exec - check for exec declared unsafe due to tracing
142 * @task: current task doing exec
143 *
144 * Return %LSM_UNSAFE_* bits applied to an exec because of tracing.
145 *
146 * Called with task_lock() held on @task.
147 */
148static inline int tracehook_unsafe_exec(struct task_struct *task)
149{
150 int unsafe = 0;
151 int ptrace = task_ptrace(task);
152 if (ptrace & PT_PTRACED) {
153 if (ptrace & PT_PTRACE_CAP)
154 unsafe |= LSM_UNSAFE_PTRACE_CAP;
155 else
156 unsafe |= LSM_UNSAFE_PTRACE;
157 }
158 return unsafe;
159}
160
161/**
Roland McGrath0d094ef2008-07-25 19:45:49 -0700162 * tracehook_tracer_task - return the task that is tracing the given task
163 * @tsk: task to consider
164 *
165 * Returns NULL if noone is tracing @task, or the &struct task_struct
166 * pointer to its tracer.
167 *
168 * Must called under rcu_read_lock(). The pointer returned might be kept
169 * live only by RCU. During exec, this may be called with task_lock()
170 * held on @task, still held from when tracehook_unsafe_exec() was called.
171 */
172static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk)
173{
174 if (task_ptrace(tsk) & PT_PTRACED)
175 return rcu_dereference(tsk->parent);
176 return NULL;
177}
178
179/**
Roland McGrath6341c392008-07-25 19:45:44 -0700180 * tracehook_report_exec - a successful exec was completed
181 * @fmt: &struct linux_binfmt that performed the exec
182 * @bprm: &struct linux_binprm containing exec details
183 * @regs: user-mode register state
184 *
185 * An exec just completed, we are shortly going to return to user mode.
186 * The freshly initialized register state can be seen and changed in @regs.
187 * The name, file and other pointers in @bprm are still on hand to be
188 * inspected, but will be freed as soon as this returns.
189 *
190 * Called with no locks, but with some kernel resources held live
191 * and a reference on @fmt->module.
192 */
193static inline void tracehook_report_exec(struct linux_binfmt *fmt,
194 struct linux_binprm *bprm,
195 struct pt_regs *regs)
196{
197 if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) &&
198 unlikely(task_ptrace(current) & PT_PTRACED))
199 send_sig(SIGTRAP, current, 0);
200}
Roland McGrath88ac2922008-07-25 19:45:43 -0700201
Roland McGrath30199f52008-07-25 19:45:46 -0700202/**
203 * tracehook_report_exit - task has begun to exit
204 * @exit_code: pointer to value destined for @current->exit_code
205 *
206 * @exit_code points to the value passed to do_exit(), which tracing
207 * might change here. This is almost the first thing in do_exit(),
208 * before freeing any resources or setting the %PF_EXITING flag.
209 *
210 * Called with no locks held.
211 */
212static inline void tracehook_report_exit(long *exit_code)
213{
214 ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code);
215}
216
Roland McGrath09a05392008-07-25 19:45:47 -0700217/**
218 * tracehook_prepare_clone - prepare for new child to be cloned
219 * @clone_flags: %CLONE_* flags from clone/fork/vfork system call
220 *
221 * This is called before a new user task is to be cloned.
222 * Its return value will be passed to tracehook_finish_clone().
223 *
224 * Called with no locks held.
225 */
226static inline int tracehook_prepare_clone(unsigned clone_flags)
227{
228 if (clone_flags & CLONE_UNTRACED)
229 return 0;
230
231 if (clone_flags & CLONE_VFORK) {
232 if (current->ptrace & PT_TRACE_VFORK)
233 return PTRACE_EVENT_VFORK;
234 } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
235 if (current->ptrace & PT_TRACE_CLONE)
236 return PTRACE_EVENT_CLONE;
237 } else if (current->ptrace & PT_TRACE_FORK)
238 return PTRACE_EVENT_FORK;
239
240 return 0;
241}
242
243/**
244 * tracehook_finish_clone - new child created and being attached
245 * @child: new child task
246 * @clone_flags: %CLONE_* flags from clone/fork/vfork system call
Roland McGratha9906a12008-07-26 14:41:26 -0700247 * @trace: return value from tracehook_prepare_clone()
Roland McGrath09a05392008-07-25 19:45:47 -0700248 *
249 * This is called immediately after adding @child to its parent's children list.
250 * The @trace value is that returned by tracehook_prepare_clone().
251 *
252 * Called with current's siglock and write_lock_irq(&tasklist_lock) held.
253 */
254static inline void tracehook_finish_clone(struct task_struct *child,
255 unsigned long clone_flags, int trace)
256{
257 ptrace_init_task(child, (clone_flags & CLONE_PTRACE) || trace);
258}
259
260/**
261 * tracehook_report_clone - in parent, new child is about to start running
Roland McGratha9906a12008-07-26 14:41:26 -0700262 * @trace: return value from tracehook_prepare_clone()
Roland McGrath09a05392008-07-25 19:45:47 -0700263 * @regs: parent's user register state
264 * @clone_flags: flags from parent's system call
265 * @pid: new child's PID in the parent's namespace
266 * @child: new child task
267 *
Roland McGratha9906a12008-07-26 14:41:26 -0700268 * Called after a child is set up, but before it has been started
269 * running. @trace is the value returned by tracehook_prepare_clone().
270 * This is not a good place to block, because the child has not started
271 * yet. Suspend the child here if desired, and then block in
272 * tracehook_report_clone_complete(). This must prevent the child from
273 * self-reaping if tracehook_report_clone_complete() uses the @child
274 * pointer; otherwise it might have died and been released by the time
Roland McGrath22f30162008-09-05 14:00:23 -0700275 * tracehook_report_clone_complete() is called.
Roland McGrath09a05392008-07-25 19:45:47 -0700276 *
277 * Called with no locks held, but the child cannot run until this returns.
278 */
279static inline void tracehook_report_clone(int trace, struct pt_regs *regs,
280 unsigned long clone_flags,
281 pid_t pid, struct task_struct *child)
282{
Roland McGrath5861bbf2008-08-07 16:55:03 -0700283 if (unlikely(trace) || unlikely(clone_flags & CLONE_PTRACE)) {
Roland McGrath09a05392008-07-25 19:45:47 -0700284 /*
285 * The child starts up with an immediate SIGSTOP.
286 */
287 sigaddset(&child->pending.signal, SIGSTOP);
288 set_tsk_thread_flag(child, TIF_SIGPENDING);
289 }
290}
291
292/**
293 * tracehook_report_clone_complete - new child is running
Roland McGratha9906a12008-07-26 14:41:26 -0700294 * @trace: return value from tracehook_prepare_clone()
Roland McGrath09a05392008-07-25 19:45:47 -0700295 * @regs: parent's user register state
296 * @clone_flags: flags from parent's system call
297 * @pid: new child's PID in the parent's namespace
298 * @child: child task, already running
299 *
300 * This is called just after the child has started running. This is
301 * just before the clone/fork syscall returns, or blocks for vfork
302 * child completion if @clone_flags has the %CLONE_VFORK bit set.
303 * The @child pointer may be invalid if a self-reaping child died and
304 * tracehook_report_clone() took no action to prevent it from self-reaping.
305 *
306 * Called with no locks held.
307 */
308static inline void tracehook_report_clone_complete(int trace,
309 struct pt_regs *regs,
310 unsigned long clone_flags,
311 pid_t pid,
312 struct task_struct *child)
313{
314 if (unlikely(trace))
315 ptrace_event(0, trace, pid);
316}
317
Roland McGrathdaded342008-07-25 19:45:47 -0700318/**
319 * tracehook_report_vfork_done - vfork parent's child has exited or exec'd
320 * @child: child task, already running
321 * @pid: new child's PID in the parent's namespace
322 *
323 * Called after a %CLONE_VFORK parent has waited for the child to complete.
324 * The clone/vfork system call will return immediately after this.
325 * The @child pointer may be invalid if a self-reaping child died and
326 * tracehook_report_clone() took no action to prevent it from self-reaping.
327 *
328 * Called with no locks held.
329 */
330static inline void tracehook_report_vfork_done(struct task_struct *child,
331 pid_t pid)
332{
333 ptrace_event(PT_TRACE_VFORK_DONE, PTRACE_EVENT_VFORK_DONE, pid);
334}
335
Roland McGrathdae33572008-07-25 19:45:48 -0700336/**
337 * tracehook_prepare_release_task - task is being reaped, clean up tracing
338 * @task: task in %EXIT_DEAD state
339 *
340 * This is called in release_task() just before @task gets finally reaped
341 * and freed. This would be the ideal place to remove and clean up any
342 * tracing-related state for @task.
343 *
344 * Called with no locks held.
345 */
346static inline void tracehook_prepare_release_task(struct task_struct *task)
347{
348}
349
350/**
Roland McGratha9906a12008-07-26 14:41:26 -0700351 * tracehook_finish_release_task - final tracing clean-up
Roland McGrathdae33572008-07-25 19:45:48 -0700352 * @task: task in %EXIT_DEAD state
353 *
354 * This is called in release_task() when @task is being in the middle of
355 * being reaped. After this, there must be no tracing entanglements.
356 *
357 * Called with write_lock_irq(&tasklist_lock) held.
358 */
359static inline void tracehook_finish_release_task(struct task_struct *task)
360{
361 ptrace_release_task(task);
362}
363
Roland McGrathc45aea22008-07-25 19:45:50 -0700364/**
365 * tracehook_signal_handler - signal handler setup is complete
366 * @sig: number of signal being delivered
367 * @info: siginfo_t of signal being delivered
368 * @ka: sigaction setting that chose the handler
369 * @regs: user register state
370 * @stepping: nonzero if debugger single-step or block-step in use
371 *
372 * Called by the arch code after a signal handler has been set up.
373 * Register and stack state reflects the user handler about to run.
374 * Signal mask changes have already been made.
375 *
376 * Called without locks, shortly before returning to user mode
377 * (or handling more signals).
378 */
379static inline void tracehook_signal_handler(int sig, siginfo_t *info,
380 const struct k_sigaction *ka,
381 struct pt_regs *regs, int stepping)
382{
383 if (stepping)
384 ptrace_notify(SIGTRAP);
385}
386
Roland McGrath35de2542008-07-25 19:45:51 -0700387/**
388 * tracehook_consider_ignored_signal - suppress short-circuit of ignored signal
389 * @task: task receiving the signal
390 * @sig: signal number being sent
Roland McGrath35de2542008-07-25 19:45:51 -0700391 *
392 * Return zero iff tracing doesn't care to examine this ignored signal,
393 * so it can short-circuit normal delivery and never even get queued.
Roland McGrath35de2542008-07-25 19:45:51 -0700394 *
395 * Called with @task->sighand->siglock held.
396 */
397static inline int tracehook_consider_ignored_signal(struct task_struct *task,
Oleg Nesterov43918f22009-04-02 16:58:00 -0700398 int sig)
Roland McGrath35de2542008-07-25 19:45:51 -0700399{
400 return (task_ptrace(task) & PT_PTRACED) != 0;
401}
402
Roland McGrath445a91d2008-07-25 19:45:52 -0700403/**
404 * tracehook_consider_fatal_signal - suppress special handling of fatal signal
405 * @task: task receiving the signal
406 * @sig: signal number being sent
Roland McGrath445a91d2008-07-25 19:45:52 -0700407 *
408 * Return nonzero to prevent special handling of this termination signal.
Oleg Nesterov43918f22009-04-02 16:58:00 -0700409 * Normally handler for signal is %SIG_DFL. It can be %SIG_IGN if @sig is
410 * ignored, in which case force_sig() is about to reset it to %SIG_DFL.
Roland McGrath445a91d2008-07-25 19:45:52 -0700411 * When this returns zero, this signal might cause a quick termination
412 * that does not give the debugger a chance to intercept the signal.
413 *
414 * Called with or without @task->sighand->siglock held.
415 */
416static inline int tracehook_consider_fatal_signal(struct task_struct *task,
Oleg Nesterov43918f22009-04-02 16:58:00 -0700417 int sig)
Roland McGrath445a91d2008-07-25 19:45:52 -0700418{
419 return (task_ptrace(task) & PT_PTRACED) != 0;
420}
421
Roland McGrath7bcf6a22008-07-25 19:45:53 -0700422/**
Roland McGrathb787f7b2008-07-25 19:45:55 -0700423 * tracehook_force_sigpending - let tracing force signal_pending(current) on
424 *
425 * Called when recomputing our signal_pending() flag. Return nonzero
426 * to force the signal_pending() flag on, so that tracehook_get_signal()
427 * will be called before the next return to user mode.
428 *
429 * Called with @current->sighand->siglock held.
430 */
431static inline int tracehook_force_sigpending(void)
432{
433 return 0;
434}
435
436/**
Roland McGrath7bcf6a22008-07-25 19:45:53 -0700437 * tracehook_get_signal - deliver synthetic signal to traced task
438 * @task: @current
439 * @regs: task_pt_regs(@current)
440 * @info: details of synthetic signal
441 * @return_ka: sigaction for synthetic signal
442 *
443 * Return zero to check for a real pending signal normally.
444 * Return -1 after releasing the siglock to repeat the check.
445 * Return a signal number to induce an artifical signal delivery,
446 * setting *@info and *@return_ka to specify its details and behavior.
447 *
448 * The @return_ka->sa_handler value controls the disposition of the
449 * signal, no matter the signal number. For %SIG_DFL, the return value
450 * is a representative signal to indicate the behavior (e.g. %SIGTERM
451 * for death, %SIGQUIT for core dump, %SIGSTOP for job control stop,
452 * %SIGTSTP for stop unless in an orphaned pgrp), but the signal number
453 * reported will be @info->si_signo instead.
454 *
455 * Called with @task->sighand->siglock held, before dequeuing pending signals.
456 */
457static inline int tracehook_get_signal(struct task_struct *task,
458 struct pt_regs *regs,
459 siginfo_t *info,
460 struct k_sigaction *return_ka)
461{
462 return 0;
463}
464
Roland McGrathfa00b802008-07-25 19:45:54 -0700465/**
466 * tracehook_notify_jctl - report about job control stop/continue
467 * @notify: nonzero if this is the last thread in the group to stop
468 * @why: %CLD_STOPPED or %CLD_CONTINUED
469 *
470 * This is called when we might call do_notify_parent_cldstop().
471 * It's called when about to stop for job control; we are already in
472 * %TASK_STOPPED state, about to call schedule(). It's also called when
473 * a delayed %CLD_STOPPED or %CLD_CONTINUED report is ready to be made.
474 *
475 * Return nonzero to generate a %SIGCHLD with @why, which is
476 * normal if @notify is nonzero.
477 *
478 * Called with no locks held.
479 */
480static inline int tracehook_notify_jctl(int notify, int why)
481{
482 return notify || (current->ptrace & PT_PTRACED);
483}
484
Roland McGrath115a3262008-08-04 13:56:01 -0700485#define DEATH_REAP -1
486#define DEATH_DELAYED_GROUP_LEADER -2
487
Roland McGrath2b2a1ff2008-07-25 19:45:54 -0700488/**
489 * tracehook_notify_death - task is dead, ready to notify parent
490 * @task: @current task now exiting
491 * @death_cookie: value to pass to tracehook_report_death()
492 * @group_dead: nonzero if this was the last thread in the group to die
493 *
Roland McGrath5c7edcd2008-07-31 02:04:09 -0700494 * A return value >= 0 means call do_notify_parent() with that signal
495 * number. Negative return value can be %DEATH_REAP to self-reap right
496 * now, or %DEATH_DELAYED_GROUP_LEADER to a zombie without notifying our
497 * parent. Note that a return value of 0 means a do_notify_parent() call
498 * that sends no signal, but still wakes up a parent blocked in wait*().
Roland McGrath2b2a1ff2008-07-25 19:45:54 -0700499 *
500 * Called with write_lock_irq(&tasklist_lock) held.
501 */
502static inline int tracehook_notify_death(struct task_struct *task,
503 void **death_cookie, int group_dead)
504{
Oleg Nesterovbb24c672009-04-02 16:58:20 -0700505 if (task_detached(task))
Roland McGrath5c7edcd2008-07-31 02:04:09 -0700506 return task->ptrace ? SIGCHLD : DEATH_REAP;
Roland McGrath2b2a1ff2008-07-25 19:45:54 -0700507
508 /*
509 * If something other than our normal parent is ptracing us, then
510 * send it a SIGCHLD instead of honoring exit_signal. exit_signal
511 * only has special meaning to our real parent.
512 */
513 if (thread_group_empty(task) && !ptrace_reparented(task))
514 return task->exit_signal;
515
Roland McGrath5c7edcd2008-07-31 02:04:09 -0700516 return task->ptrace ? SIGCHLD : DEATH_DELAYED_GROUP_LEADER;
Roland McGrath2b2a1ff2008-07-25 19:45:54 -0700517}
518
519/**
520 * tracehook_report_death - task is dead and ready to be reaped
521 * @task: @current task now exiting
Roland McGrath5c7edcd2008-07-31 02:04:09 -0700522 * @signal: return value from tracheook_notify_death()
Roland McGrath2b2a1ff2008-07-25 19:45:54 -0700523 * @death_cookie: value passed back from tracehook_notify_death()
524 * @group_dead: nonzero if this was the last thread in the group to die
525 *
526 * Thread has just become a zombie or is about to self-reap. If positive,
527 * @signal is the signal number just sent to the parent (usually %SIGCHLD).
Roland McGrath5c7edcd2008-07-31 02:04:09 -0700528 * If @signal is %DEATH_REAP, this thread will self-reap. If @signal is
529 * %DEATH_DELAYED_GROUP_LEADER, this is a delayed_group_leader() zombie.
530 * The @death_cookie was passed back by tracehook_notify_death().
Roland McGrath2b2a1ff2008-07-25 19:45:54 -0700531 *
532 * If normal reaping is not inhibited, @task->exit_state might be changing
533 * in parallel.
534 *
535 * Called without locks.
536 */
537static inline void tracehook_report_death(struct task_struct *task,
538 int signal, void *death_cookie,
539 int group_dead)
540{
541}
542
Roland McGrath64b1208d2008-07-25 19:45:56 -0700543#ifdef TIF_NOTIFY_RESUME
544/**
545 * set_notify_resume - cause tracehook_notify_resume() to be called
546 * @task: task that will call tracehook_notify_resume()
547 *
548 * Calling this arranges that @task will call tracehook_notify_resume()
549 * before returning to user mode. If it's already running in user mode,
550 * it will enter the kernel and call tracehook_notify_resume() soon.
551 * If it's blocked, it will not be woken.
552 */
553static inline void set_notify_resume(struct task_struct *task)
554{
555 if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
556 kick_process(task);
557}
558
559/**
560 * tracehook_notify_resume - report when about to return to user mode
561 * @regs: user-mode registers of @current task
562 *
563 * This is called when %TIF_NOTIFY_RESUME has been set. Now we are
564 * about to return to user mode, and the user state in @regs can be
565 * inspected or adjusted. The caller in arch code has cleared
566 * %TIF_NOTIFY_RESUME before the call. If the flag gets set again
567 * asynchronously, this will be called again before we return to
568 * user mode.
569 *
570 * Called without locks.
571 */
572static inline void tracehook_notify_resume(struct pt_regs *regs)
573{
574}
575#endif /* TIF_NOTIFY_RESUME */
576
Roland McGrath88ac2922008-07-25 19:45:43 -0700577#endif /* <linux/tracehook.h> */