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Commit 64b1208d authored by Roland McGrath's avatar Roland McGrath Committed by Linus Torvalds
Browse files

tracehook: TIF_NOTIFY_RESUME 



This adds tracehook.h inlines to enable a new arch feature in support of
user debugging/tracing.  This is not used yet, but it lays the groundwork
for a debugger to be able to wrangle a task that's possibly running,
without interrupting its syscalls in progress.

Each arch should define TIF_NOTIFY_RESUME, and in their entry.S code treat
it much like TIF_SIGPENDING.  That is, it causes you to take the slow path
when returning to user mode, where you get the full user-mode state
accessible as for signal handling or ptrace.  The arch code should check
TIF_NOTIFY_RESUME after handling TIF_SIGPENDING.  When it's set, clear it
and then call tracehook_notify_resume().

In future, tracing code will call set_notify_resume() when it wants to get
a callback in tracehook_notify_resume().

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b787f7ba

include/linux/tracehook.h

+34 −0
Original line number Diff line number Diff line
@@ -537,4 +537,38 @@ static inline void tracehook_report_death(struct task_struct *task, 
{

}



#ifdef TIF_NOTIFY_RESUME

/**

 * set_notify_resume - cause tracehook_notify_resume() to be called

 * @task:		task that will call tracehook_notify_resume()

 *

 * Calling this arranges that @task will call tracehook_notify_resume()

 * before returning to user mode.  If it's already running in user mode,

 * it will enter the kernel and call tracehook_notify_resume() soon.

 * If it's blocked, it will not be woken.

 */

static inline void set_notify_resume(struct task_struct *task)

{

	if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))

		kick_process(task);

}



/**

 * tracehook_notify_resume - report when about to return to user mode

 * @regs:		user-mode registers of @current task

 *

 * This is called when %TIF_NOTIFY_RESUME has been set.  Now we are

 * about to return to user mode, and the user state in @regs can be

 * inspected or adjusted.  The caller in arch code has cleared

 * %TIF_NOTIFY_RESUME before the call.  If the flag gets set again

 * asynchronously, this will be called again before we return to

 * user mode.

 *

 * Called without locks.

 */

static inline void tracehook_notify_resume(struct pt_regs *regs)

{

}

#endif	/* TIF_NOTIFY_RESUME */



#endif	/* <linux/tracehook.h> */