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tracehook: TIF_NOTIFY_RESUME

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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: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2008-07-25 19:45:56 -07:00 committed by Linus Torvalds
parent b787f7ba67
commit 64b1208d5b
1 changed files with 34 additions and 0 deletions
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34
include/linux/tracehook.h
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@ -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> */