Re: [patch] i386: fix singlestepping though a syscall

[Linus Torvalds <torvalds@osdl.org>]

On Thu, 16 Feb 2006, Chuck Ebbert wrote:
>
> Singlestep through a syscall using vsyscall-sysenter had two bugs:
> 
>     1.  Setting TIF_SINGLESTEP is not enough to force
>         do_notify_resume() to be run on return to user;
>         TIF_IRET must also be set.

Interesting, but I think you pinpointed the _real_ bug.

TIF_SINGLESTEP very much should be enough to force do_notify_resume() to 
be run on return to user space.

Sounds like somebody is testing _TIF_WORK_MASK rather than 
_TIF_ALLWORK_MASK.

I'd suspect the "work_pending" case. Looks like we miss testing the TIF 
flags there.

Oh, actually, I think you should just remove the clearing of 
_TIF_SINGLESTEP from _TIF_WORK_MASK. Does that fix the bug.

		Linus
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