Re: [PATCH 03/10] ptrace: implement PTRACE_SEIZE

[Tejun Heo]

Hello, Pedro.

On Fri, May 20, 2011 at 12:00:17AM +0100, Pedro Alves wrote:
> > > UUIC, that opens a race where between SEIZEing and
> > > SETOPTIONS(O_TRACE FORK|VFORK|EXEC...), the tracee can
> > > fork/vfork/clone/exec, without the tracer getting the
> > > nice corresponding PTRACE_EVENT_ events.

Does it matter?  The order of execution isn't even well defined
without synchronization border.  If you want full synchronization, you
can INTERRUPT tracee.

>  SEIZE,execvd,INTERRUPT (SETOPTS on interrupt)
> 
> will make the tracer see a SIGTRAP that 
> 
>  execvd,SEIZE,INTERRUPT
> 
> nor
> 
>  SEIZE,SETOPTS,execvd (SETOPTS on interrupt)
> 
> would cause, isn't it?

Yes, SIGTRAP on exec(2) is nasty but also is scheduled to be removed
if SEIZED.

> Now, if it were possible for the tracer to set the
> default OPTS _before_ PTRACE_ATTACH/PTRACE_SEIZE...

I don't see why that would be necessary.

Thanks.

-- 
tejun
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